WorldWideScience

Sample records for voltage sags ride-through

  1. Analysis of ride through capability of fluorescent lamps during voltage sags

    Energy Technology Data Exchange (ETDEWEB)

    Shareef, H.; Mohamed, A.; Marzuki, N. [Kebangsaan Malaysia Univ., Selangor (Malaysia). Dept. of Electrical, Electronic and Systems Engineering, Faculty of Engineering and Built Environment

    2009-03-11

    A comparative analysis of the sensitivity to voltage sags of various low-wattage fluorescent lamps (FL) used in commercial and residential lighting applications was presented. A power corrupter and advanced photometer were used to conduct the tests on three 18 watt FLs with different ballasts. Sag depth and duration were varied in order to develop voltage immunity curves for a predefined malfunction criterion of 0 illuminance. The study showed that ballast technologies play a significant role in voltage sag event ride-through. Lamps with electromagnetic ballasts were more sensitive to voltage sags than lamps equipped with electronic ballasts. The study also demonstrated that the voltage immunity levels of the compact fluorescent lamps (CFLs) with electromagnetic ballasts did not meet ITIC and SEMI F47 standards. 12 refs., 1 tab., 10 figs.

  2. Voltage Sags Ride-Through of Motion Sensorless Controlled PMSG for Wind Turbines

    DEFF Research Database (Denmark)

    Fatu, Marius; Lascu, Cristian; Andreescu, Gheorghe-Daniel

    2007-01-01

    is used to robustly estimate the grid voltage positivesequence for control in the case of asymmetric voltages. The paper investigates the ride-through performance of this system during asymmetric power grid voltage sags. Design details for various parts of the control system are presented, together...... with experimental results for single-, two-, and three-phase voltage source sags. Smooth transition through asymmetric voltage sags is demonstrated by all experiments........ The control system employs PI current controllers with crosscoupling decoupling for both inverters, an active power controller, and a DC link voltage controller. The PMSG rotor speed without using emf integration, and the line voltage frequency are estimated by two PLL based observers. A Dmodule filter...

  3. Distributed Low Voltage Ride-Through Operation of Power Converters in Grid-Connected Microgrids under Voltage Sags

    DEFF Research Database (Denmark)

    Zhao, Xin; Meng, Lexuan; Dragicevic, Tomislav

    2015-01-01

    it can make the MG a contributor in smooth ride through the faults. In this paper, a reactive power support strategy using droop controlled converters is proposed to aid MG riding through three phase symmetrical voltage sags. In such a case, the MGs should inject reactive power to the grid to boost...... the voltage in all phases at AC common bus. However, since the line admittances from each converter to point of common coupling (PCC) are not identical, the injected reactive power may not be equally shared. In order to achieve low voltage ride through (LVRT) capability along with a good power sharing...

  4. Active Rectifier with Extended Functions: An Option to Voltage Sags Ride Through and Power Quality Improvement

    Directory of Open Access Journals (Sweden)

    Echavarría–Solís R.

    2010-07-01

    Full Text Available The power quality concept, is usually confused with energy saving. However, even if energy saving is desirable over all in industry applications, the first concept does not implie the second one. For the electrical engineers, the improvement of power quality using the existing converters is a great challenge. This paper deals with a multilevel, single phase active rectifier whose main objective is to compensate power factor which, with an adequate control, provides voltage sag compensation and power quality conditioning

  5. Benchmarking of Voltage Sag Generators

    DEFF Research Database (Denmark)

    Yang, Yongheng; Blaabjerg, Frede; Zou, Zhixiang

    2012-01-01

    to guide these grid-connected distributed power generation systems. In order to verify the response of such systems for voltage disturbance, mainly for evaluation of voltage sags/dips, a Voltage Sag Generator (VSG) is needed. This paper evaluates such sag test devices according to IEC 61000 in order...... to provide cheaper solutions to test against voltage sags. Simulation and experimental results demonstrate that the shunt impedance based VSG solution is the easiest and cheapest one for laboratory test applications. The back-to-back fully controlled converter based VSG is the most flexible solution......The increased penetration of renewable energy systems, like photovoltaic and wind power systems, rises the concern about the power quality and stability of the utility grid. Some regulations for Low Voltage Ride-Through (LVRT) for medium voltage or high voltage applications, are coming into force...

  6. Low voltage ride-Through strategy based on virtual synchronous generator control

    Science.gov (United States)

    Guo, L.; Su, J. H.; Yu, L.; Lai, J. D.

    2017-06-01

    Inverters controlled in virtual synchronous generator(VSG) method is able to operate in both grid-connected mode and islanding mode. Due to this characteristic, this paper put forwards a low voltage ride-through(LVRT) strategy which is based on VSG control. If the grid voltage sags, VSG can limit the output current amplitude and meanwhile inject reactive power to the grid. Once the voltage drop time exceeds the maximum ride-through time, VSG would smoothly switch to islanding mode and continues to carry loads independently. The proposed strategy achieves a control algorithm unity between normal operating and grid voltage sag status in grid-connected mode. Simulations can support the validity of the strategy.

  7. Low Voltage Ride-Through Capability Solutions for Permanent Magnet Synchronous Wind Generators

    Directory of Open Access Journals (Sweden)

    Victor F. Mendes

    2016-01-01

    Full Text Available Due to the increasing number of wind power plants, several countries have modified their grid codes to include specific requirements for the connection of this technology to the power system. One of the requirements is the ride-through fault capability (RTFC, i.e., the system capability to sustain operation during voltage sags. In this sense, the present paper intends to investigate the behavior of a full-converter wind generator with a permanent magnet synchronous machine during symmetrical and asymmetrical voltage sags. Two solutions to improve the low voltage ride-through capability (LVRT of this technology are analyzed: discharging resistors (brake chopper and resonant controllers (RCs. The design and limitations of these solutions and the others proposed in the literature are discussed. Experimental results in a 34 kW test bench, which represents a scaled prototype of a real 2 MW wind conversion system, are presented.

  8. Fast Coordinated Control of DFIG Wind Turbine Generators for Low and High Voltage Ride-Through

    DEFF Research Database (Denmark)

    Wang, Yun; Wu, Qiuwei; Xu, Honghua

    2014-01-01

    (HVRT) capability of the DFIG WTGs. The characteristics of DFIG WTGs under voltage sags and swells were studied focusing on the DFIG WTG stator flux and rotor voltages during the transient periods of grid voltage changes. The protection schemes of the rotor crowbar circuit and the dc chopper circuit......This paper presents a fast coordinated control scheme of the rotor side converter (RSC), the DC chopper and the grid side converter (GSC) of doubly fed induction generator (DFIG) wind turbine generators (WTGs) which is to improve the low voltage ride through (LVRT) and high voltage ride through...... were proposed considering the characteristics of the DFIG WTGs during voltage changes. The fast coordinated control of RSC and GSC were developed based on the characteristic analysis in order to realize efficient LVRT and HVRT of the DFIG WTGs. The proposed fast coordinated control schemes were...

  9. Fast Coordinated Control of DFIG Wind Turbine Generators for Low and High Voltage Ride-Through

    Directory of Open Access Journals (Sweden)

    Yun Wang

    2014-06-01

    Full Text Available This paper presents a fast coordinated control scheme of the rotor side converter (RSC, the Direct Current (DC chopper and the grid side converter (GSC of doubly fed induction generator (DFIG wind turbine generators (WTGs to improve the low voltage ride through (LVRT and high voltage ride through (HVRT capability of the DFIG WTGs. The characteristics of DFIG WTGs under voltage sags and swells were studied focusing on the DFIG WTG stator flux and rotor voltages during the transient periods of grid voltage changes. The protection schemes of the rotor crowbar circuit and the DC chopper circuit were proposed considering the characteristics of the DFIG WTGs during voltage changes. The fast coordinated control of RSC and GSC were developed based on the characteristic analysis in order to realize efficient LVRT and HVRT of the DFIG WTGs. The proposed fast coordinated control schemes were verified by time domain simulations using Matlab-Simulink.

  10. A flexible low-voltage ride-through operation for the distributed generation converters

    DEFF Research Database (Denmark)

    Chen, Hsin-Chih; Lee, Chia-Tse; Cheng, Po-Tai

    2013-01-01

    With more and more distributed energy resources (DERs) are installed in the utility grid, the utility requires the DER generation system to remain grid-connected and injects reactive and active power to support grid voltage during voltage sags. In this paper, a positive- and negative......-sequence current injection method is proposed to meet the low-voltage ride through (LVRT) requirement. The proposed method predefined a current constraint to avoid the overcurrent during the LVRT operation and adjust the positive-sequence reactive current to reduce the DC-bus voltage ripple. Comparisons...

  11. Challenges to Grid Synchronization of Single-Phase Grid-Connected Inverters in Zero-Voltage Ride-Through Operation

    DEFF Research Database (Denmark)

    Zhang, Zhen; Yang, Yongheng; Blaabjerg, Frede

    2016-01-01

    to remain connected under grid voltage sags (even zero voltage condition). In this case, much attention should be paid to the grid synchronization in such a way to properly ride-through grid faults. Thus, in this paper, the most commonly-used and recently-developed Phase Locked Loop (PLL) synchronization...... methods have been evaluated for single-phase grid-connected PV systems in the case of Zero-Voltage Ride-Through (ZVRT) operation. The performances of the prior-art PLL methods in response to zero voltage faults in terms of detection precision and dynamic response are assessed in this paper. Simulation...

  12. Low Voltage Ride-Through of Single-Phase Transformerless Photovoltaic Inverters

    DEFF Research Database (Denmark)

    Yang, Yongheng; Blaabjerg, Frede; Wang, Huai

    2014-01-01

    , although the HERIC inverter is the best candidate in terms of efficiency, it is not very special feasible in case of a voltage sag. The other two topologies are capable of providing reactive current during LVRT. A benchmarking of those inverters is also provided in this paper, which offers the possibility......, e.g. Low Voltage Ride-Through (LVRT) under grid faults and grid support service. In order to map future challenges, the LVRT capability of three mainstream single-phase transformerless PV inverters under grid faults are explored in this paper. Control strategies with reactive power injections...

  13. Low voltage ride-through of single-phase transformerless photovoltaic inverters

    DEFF Research Database (Denmark)

    Yang, Yongheng; Blaabjerg, Frede; Wang, Huai

    2013-01-01

    the HERIC inverter is the best candidate in terms of efficiency, it is not very feasible in case of a voltage sag. The other topologies are capable of providing reactive current during LVRT. A benchmarking of those inverters is also provided, which offers the possibility to select appropriate devices.......g. Low Voltage Ride-Through (LVRT) under grid faults and grid support service. In order to map future challenges, the LVRT capability of three mainstream single-phase transformerless PV inverters under grid faults are explored in this paper. Control strategies with reactive power injections are also...

  14. A Dynamic Consensus Algorithm based Low-Voltage Ride-Through Operation of Power Converters in Grid-Interactive Microgrids

    DEFF Research Database (Denmark)

    Zhao, Xin; Meng, Lexuan; Savaghebi, Mehdi

    2016-01-01

    The possibility of increasing penetration level of grid-interactive microgrids (MGs) has gained a great interest over the past decade. Thus, it is critical to investigate the performance of the MGs under voltage sags, since it may induce instability to the power grid. Negative sequence droop...... control based voltage support strategy has been proposed to aid MGs riding through three phase asymmetrical voltage sags. However, since the line impedance from each converter to the point of common coupling (PCC) is not identical, both positive sequence and negative sequence output current...

  15. Doubly-Fed Induction Generator Control Under Voltage Sags

    DEFF Research Database (Denmark)

    Teodorescu, Remus; Blaabjerg, Frede; Lima, K.

    2008-01-01

    This paper proposes a new control technique to improve the fault-ride through capability of doubly fed induction generators (DFIG). In such generators the appearance of severe voltage sags at the coupling point make rise to high over currents at the rotor/stator windings, something that makes...

  16. Negative Sequence Droop Method based Hierarchical Control for Low Voltage Ride-Through in Grid-Interactive Microgrids

    DEFF Research Database (Denmark)

    Zhao, Xin; Firoozabadi, Mehdi Savaghebi; Quintero, Juan Carlos Vasquez

    2015-01-01

    In highly microgrid (MG) integrated distribution systems, problems such as a sudden cut out of the MGs due to grid faults may lead to adverse effects to the grid. As a consequence, ancillary services provided by MGs are preferred since it can make the MG a contributor to ride through the faults....... In this paper, a voltage support strategy based on negative sequence droop control, which regulate the positive/negative sequence active and reactive power flow by means of sending proper voltage reference to the inner control loop, is proposed for the grid connected MGs to ride through voltage sags under...... complex line impedance conditions. In this case, the MGs should inject a certain amount of positive and negative sequence power to the grid so that the voltage quality at load side can be maintained at a satisfied level. A two layer hierarchical control strategy is proposed in this paper. The primary...

  17. Low-Voltage Ride-Through Operation of Power Converters in Grid-Interactive Microgrids by Using Negative-Sequence Droop Control

    DEFF Research Database (Denmark)

    Zhao, Xin; Guerrero, Josep M.; Savaghebi, Mehdi

    2017-01-01

    Due to the increasing penetration level of microgrids (MGs), it becomes a critical issue for MGs to help sustaining power system stability. Therefore, ancillary services, such as the low-voltage ride-through (LVRT) capability should be incorporated in MGs in order to guarantee stable operation of......, while the secondary controller is based on a positive/negative sequence droop scheme which is able to coordinate the power injection during voltage sags. Experimental results are obtained to verify the effectiveness of the proposed control strategy....... of the utility grid during grid faults. In this paper, a LVRT control strategy based on positive/negative sequence droop control is proposed for grid-interactive MGs to ride-through voltage sags with not only inductive/resistive, but also complex line impedance. By using the proposed control strategy, MGs can...

  18. Macroeconomic Assessment of Voltage Sags

    Directory of Open Access Journals (Sweden)

    Sinan Küfeoğlu

    2016-12-01

    Full Text Available The electric power sector has changed dramatically since the 1980s. Electricity customers are now demanding uninterrupted and high quality service from both utilities and authorities. By becoming more and more dependent on the voltage sensitive electronic equipment, the industry sector is the one which is affected the most by voltage disturbances. Voltage sags are one of the most crucial problems for these customers. The utilities, on the other hand, conduct cost-benefit analyses before going through new investment projects. At this point, understanding the costs of voltage sags become imperative for planning purposes. The characteristics of electric power consumption and hence the susceptibility against voltage sags differ considerably among different industry subsectors. Therefore, a model that will address the estimation of worth of electric power reliability for a large number of customer groups is necessary. This paper introduces a macroeconomic model to calculate Customer Voltage Sag Costs (CVSCs for the industry sector customers. The proposed model makes use of analytical data such as value added, annual energy consumption, working hours, and average outage durations and provides a straightforward, credible, and easy to follow methodology for the estimation of CVSCs.

  19. Improved fault ride through capability of DFIG based wind turbines using synchronous reference frame control based dynamic voltage restorer.

    Science.gov (United States)

    Rini Ann Jerin, A; Kaliannan, Palanisamy; Subramaniam, Umashankar

    2017-09-01

    Fault ride through (FRT) capability in wind turbines to maintain the grid stability during faults has become mandatory with the increasing grid penetration of wind energy. Doubly fed induction generator based wind turbine (DFIG-WT) is the most popularly utilized type of generator but highly susceptible to the voltage disturbances in grid. Dynamic voltage restorer (DVR) based external FRT capability improvement is considered. Since DVR is capable of providing fast voltage sag mitigation during faults and can maintain the nominal operating conditions for DFIG-WT. The effectiveness of the DVR using Synchronous reference frame (SRF) control is investigated for FRT capability in DFIG-WT during both balanced and unbalanced fault conditions. The operation of DVR is confirmed using time-domain simulation in MATLAB/Simulink using 1.5MW DFIG-WT. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

  20. Improving Low Voltage Ride Through Capability of Wind Generators Using Dynamic Voltage Restorer

    Science.gov (United States)

    Sivasankar, Gangatharan; Suresh Kumar, Velu

    2014-08-01

    The increasing wind power integration with power grid has forced the situation to improve the reliability of wind generators for stable operation. One important problem with induction generator based wind farm is its low ride through capability to the grid voltage disturbance. Any disturbance such as voltage dip may cause wind farm outages. Since wind power contribution is in predominant percentage, such outages may lead to stability problem. The proposed strategy is to use dynamic voltage controller (DVR) to compensate the voltage disturbance. The DVR provides the wind generator the ability to remain connected in grid and improve the reliability. The voltage dips due to symmetrical and unsymmetrical faults are considered for analysis. The vector control scheme is employed for fault compensation which uses software phase locked loop scheme and park dq0 transformation technique. Extensive simulation results are included to illustrate the control and operation of DVR.

  1. Low Voltage Ride-Through of Variable Speed Wind Turbines with Permanent Magnet Synchronous Generator

    DEFF Research Database (Denmark)

    Hu, Weihao; Chen, Zhe; Wang, Yue

    2009-01-01

    This paper presents a simulation model of a MW-level variable speed wind turbine with a permanent magnet synchronous generator (PMSG) and a full-scale converter developed in the simulation tool of PSCAD/EMTDC. The low voltage ride-through (LVRT) capability of the wind turbine is investigated. A new...

  2. Fault ride through and voltage regulation for grid connected wind turbine

    Energy Technology Data Exchange (ETDEWEB)

    Kyaw, Min Min; Ramachandaramurthy, V.K. [Power Quality Research Group, Department of Electrical Power Engineering, Universiti Tenaga Nasional, Putrajaya Campus, 43009 Selangor (Malaysia)

    2011-01-15

    High penetration of wind generation challenges wind turbine operators to supply reliable power and extract optimum power from the wind. Hence, the fault ride through (FRT) capability of wind turbine together with the optimum power tracking and regulation of wind turbine output voltage due to fluctuating nature of the wind becomes essential. In this paper, a method is proposed to ensure that the double fed induction generator (DFIG) wind turbine continues to operate during severe grid faults and maintains a constant output voltage, irrespective of the fluctuating wind. The proposed controller also allows the DFIG wind turbine to track optimum power from the wind. Extensive simulation is performed using PSCAD/EMTDC software and results obtained show that the DFIG output voltage fulfills the grid code requirements. The results also show that the proposed method is able to track the optimum power, regulate the DFIG output voltage and perform fault ride through of wind turbine. (author)

  3. Low Voltage Ride-Through of Two-Stage Grid-Connected Photovoltaic Systems Through the Inherent Linear Power-Voltage Characteristic

    DEFF Research Database (Denmark)

    Yang, Yongheng; Sangwongwanich, Ariya; Liu, Hongpeng

    2017-01-01

    automatically through a proportional controller according to the voltage sag level and PV inherent characteristics (i.e., the voltage and power droop). Compared to prior-art LVRT schemes, the proposed method is cost-effective, as it is achieved by simply plugging the proportional controller into a maximum power......In this paper, a cost-effective control scheme for two-stage grid-connected PhotoVoltaic (PV) systems in Low Voltage Ride-Through (LVRT) operation is proposed. In the case of LVRT, the active power injection by PV panels should be limited to prevent from inverter over-current and also energy...... point tracking controller without significant hardware or software modifications. In this way, the PV system will not operate at the maximum power point, whereas the inverter will not face any over-current challenge but can provide reactive power support in response to the grid voltage fault...

  4. Coordinated Low Voltage Ride through strategies for Permanent Magnet Direct Drive Synchronous Generators

    Directory of Open Access Journals (Sweden)

    Zhang Ge

    2016-01-01

    Full Text Available By analyzing the mechanism of the low voltage ride through on the permanent magnet direct drive synchronous wind power generating units, this paper proposes a coordinated control strategy for permanent magnet synchronous generator. In order to avoid over speed operation of the generation units, over voltage on DC capacitor and over current on convert, the improved pitch angle control and inverter control are used. When the grid voltage drops, the captured wind power is cut down by the variable pitch system, which limits the speed of the generator, the generator side converter keeps the DC capacitor voltage stabile; and the grid side converter provides reactive power to the grid to help the grid voltage recover. The control strategy does not require any additional hardware equipment, with existing control means, the unit will be able to realize low voltage ride through. Finally, based on Matlab/Simulink to build permanent magnet direct drive wind power generation system, the simulation results verify the correctness and effectiveness of the control strategy.

  5. Inrush Transient Current Analysis and Suppression of Photovoltaic Grid-Connected Inverters During Voltage Sag

    DEFF Research Database (Denmark)

    Li, Zhongyu; Zhao, Rende; Xin, Zhen

    2016-01-01

    The Inrush Transient Current (ITC) in the output of the photovoltaic grid-connected inverters is usually generated when grid voltage sag occurs, which can trigger the protection of the grid-connected inverters, and even destroy the semiconductor switches. Then, the grid-connected inverters...... will thus fail to ride through the voltage sag and even further cause more serious grid faults. This paper analyzes the generation principle of ITC and explores its influence factors, upon which, the suppression approaches are presented. Simulation and experimental results validate the theoretical analysis...

  6. Cooperative control of VSC-HVDC connected offshore wind farm with Low-Voltage Ride-Through capability

    DEFF Research Database (Denmark)

    Liu, Yan; Wang, Xiongfei; Chen, Zhe

    2012-01-01

    The Low-Voltage Ride-Through (LVRT) has become an important grid requirement for offshore wind farms connecting with Voltage Source Converter based High Voltage Direct Current (VSC-HVDC) links. In this paper, a cooperative control strategy with LVRT ability is proposed for a VSC-HVDC connected...

  7. Coordinated control for low voltage ride-through of a PMSG-based wind power plant

    Directory of Open Access Journals (Sweden)

    Khagendra Thapa

    2016-01-01

    Full Text Available Wind turbine generators should be kept connected to a power grid, while supporting the voltage recovery in the case of a grid fault to meet low voltage ride-through requirement in some grid codes. This paper proposes a coordinated control scheme that prevents the increase in the DC-link voltage by reducing the active power in the machine side converter of permanent magnet synchronous generators (PMSGs in proportion to the voltage dip at the terminal of PMSGs. The proposed scheme changes the current priorities from the active current to the reactive current to inject more reactive power for a severe fault depending on the voltage dip. In addition, the grid-side converter operates in a voltage control mode with the slope, which is the ratio of reactive current capability to the voltage tolerance around a rated value. Moreover, during the fault, the slope is changed depending on the voltage dip to inject more reactive current. The performance of the proposed scheme is validated for a wind power plant consisting of 20 units of 5-MW PMSGs using an EMTP-RV simulator. The results demonstrate that the scheme enables the PMSGs not only to survive during the fault, but also to provide a dynamic reactive power support.

  8. A Low-Voltage Ride-Through Technique for Grid-Connected Converters with Reduced Power Transistors Stress

    DEFF Research Database (Denmark)

    Chen, Hsin-Chih; Lee, Chia-Tse; Cheng, Po-Tai

    2016-01-01

    With more and more distributed energy resources being installed in the utility grid, grid operators start imposing the low-voltage ride-through requirement on such systems to remain grid-connected and inject reactive and/or active current to support grid voltage during fault conditions. This pape...

  9. Coordinated Control Strategies of VSC-HVDC-Based Wind Power Systems for Low Voltage Ride Through

    Directory of Open Access Journals (Sweden)

    Xinyin Zhang

    2015-07-01

    Full Text Available The Voltage Source Converter-HVDC (VSC-HVDC system applied to wind power generation can solve large scale wind farm grid-connection and long distance transmission problems. However, the low voltage ride through (LVRT of the VSC-HVDC connected wind farm is a key technology issue that must be solved, and it is currently lacking an economic and effective solution. In this paper, a LVRT coordinated control strategy is proposed for the VSC-HVDC-based wind power system. In this strategy, the operation and control of VSC-HVDC and wind farm during the grid fault period is improved. The VSC-HVDC system not only provides reactive power support to the grid, but also effectively maintains the power balance and DC voltage stability by reducing wind-farm power output, without increasing the equipment investment. Correspondingly, to eliminate the influence on permanent magnet synchronous generator (PMSG-based wind turbine (WT systems, a hierarchical control strategy is designed. The speed and validity of the proposed LVRT coordinated control strategy and hierarchical control strategy were verified by MATLAB/Simulink simulations.

  10. Mitigation of Voltage Sags in CIGRE Low Voltage Distribution Network

    DEFF Research Database (Denmark)

    Mustafa, Ghullam; Bak-Jensen, Birgitte; Mahat, Pukar

    2013-01-01

    problems in the distribution system. The voltage problems dealt with in this paper are to show how to mitigate voltage sags in the CIGRE Low Voltage (LV) test network and networks like this. The voltage sags, for the tested cases in the CIGRE LV test network are mainly due to three phase faults....... The compensation of voltage sags in the different parts of CIGRE distribution network is done by using the four STATCOM compensators already existing in the test grid. The simulations are carried out in DIgSILENT power factory software version 15.0.......Any problem in voltage in a power network is undesirable as it aggravates the quality of the power. Power electronic devices such as Voltage Source Converter (VSC) based Static Synchronous Compensator (STATCOM), Dynamic Voltage Restorer (DVR) etc. are commonly used for the mitigation of voltage...

  11. Study of Low Voltage Ride Through Performance for Wind Power Generation with Doubly Fed Induction Generator

    Science.gov (United States)

    Hirawata, Ryoya; Kai, Takaaki

    Recently, the introduction of wind power generation is increasing rapidly. The ratio of wind power generation to the capacity of a total generation is getting higher and higher. When the phase-to-phase fault occurs in the power system, the frequency of power system is lower due to disconnecting of the wind power generation with doubly fed induction generator (DFIG). Therefore, the power system might become unstable. This paper describes the LVRT (low voltage ride through) performance improvement scheme of the wind power generation with DFIG. The wind power generation is disconnected from the grid in case of the power system fault. It is independently in operation from the grid by controlling of the inverter equipped in the generation. After clearance of the power system fault, the wind power generation is immediately re-connected to the grid. As a result, instability in the power system disappears. The performance of LVRT is confirmed by using simulation software PSCAD/EMTDC. The simulation result shows an excellent result to the three-phase short-circuit fault of the voltage dip 100%.

  12. Dynamic Stability Improvement of Grid Connected DFIG Using Enhanced Field Oriented Control Technique for High Voltage Ride Through

    OpenAIRE

    Ananth Duggirala, V.N.; Nagesh Kumar Gundavarapu, V.

    2015-01-01

    Doubly fed induction generator (DFIG) is a better alternative to increased power demand. Modern grid regulations force DFIG to operate without losing synchronism during overvoltages called high voltage ride through (HVRT) during grid faults. Enhanced field oriented control technique (EFOC) was proposed in Rotor Side Control of DFIG converter to improve power flow transfer and to improve dynamic and transient stability. Further electromagnetic oscillations are damped, improved voltage mitigati...

  13. Low Voltage Ride-through in DFIG Wind Generators by Controlling the Rotor Current without Crowbars

    Directory of Open Access Journals (Sweden)

    Jaime Rodríguez Arribas

    2014-01-01

    Full Text Available Among all the different types of electric wind generators, those that are based on doubly fed induction generators, or DFIG technology, are the most vulnerable to grid faults such as voltage sags. This paper proposes a new control strategy for this type of wind generator, that allows these devices to withstand the effects of a voltage sag while following the new requirements imposed by grid operators. This new control strategy makes the use of complementary devices such as crowbars unnecessary, as it greatly reduces the value of currents originated by the fault. This ensures less costly designs for the rotor systems as well as a more economic sizing of the necessary power electronics. The strategy described here uses an electric generator model based on space-phasor theory that provides a direct control over the position of the rotor magnetic flux. Controlling the rotor magnetic flux has a direct influence on the rest of the electrical variables enabling the machine to evolve to a desired work point during the transient imposed by the grid disturbance. Simulation studies have been carried out, as well as test bench trials, in order to prove the viability and functionality of the proposed control strategy.

  14. Voltage sag source location based on instantaneous energy detection

    DEFF Research Database (Denmark)

    Chen, Zhe; Xinzhou, Dong; Wei, Kong

    2007-01-01

    Voltage sag is the major power quality problem, which could disrupt the operation of sensitive equipment. This paper presents the applications of instantaneous energy direction for voltage sag source detection. Simulations have been performed to provide the analysis for system with distributed...... generation units. The studies show that the presented method can effectively detect the location of the voltage sag source....

  15. A Low-Voltage Ride-Through Control Strategy for Three-Phase Grid-Connected PV Systems

    DEFF Research Database (Denmark)

    Afshari, Ehsan; Farhangi, Babak; Yang, Yongheng

    2017-01-01

    This paper proposes a novel control strategy for the two-stage three-phase Photovoltaic (PV) systems to improve the operation under unbalanced grid faults. In case that a three-phase power converter operates under unbalanced grid voltage faults, power related issues, including injected currents...... similar variations in the dc-link voltage of conventional two-stage PV inverters. In such systems with an electrolytic capacitor in the dc-link, the oscillations of the dc-link voltage with DGF can deteriorate the capacitor lifetime, and thus the entire system. The proposed Low-Voltage Ride-Through (LVRT...

  16. Low Voltage Ride-Through Capability of a Single-Stage Single-Phase Photovoltaic System Connected to the Low-Voltage Grid

    DEFF Research Database (Denmark)

    Yang, Yongheng; Blaabjerg, Frede

    2013-01-01

    to map future challenges. The system is verified by simulations and experiments. Test results show that the proposed power control method is effective and the single-phase PV inverters connected to low-voltage networks are ready to provide grid support and ride-through voltage fault capability...

  17. Affect of Voltage Sags on Electro-magnetic Contactor

    Science.gov (United States)

    Iyoda, Isao; Ando, Yoshitaro; Pounyakhet, Sompathana; Hirata, Masaya; Ise, Toshifumi

    Sensitivity of electro-magnetic contactors for voltage sags is studied by experiments and simulations. An experimental circuit with a semiconductor fault switch that controls the phase angle of system voltage at the initial point of voltage sags is developed. The phase angle is a new parameter for voltage sags. The operating characteristics of the contactor are evaluated in various conditions. It is found that shallow sags may cause faster trips of contactors compared to deep sags in some cases. The reason of this phenomenon is analyzed with simulations.

  18. Low voltage ride through strategies for SCIG wind turbines in distributed power generation systems

    DEFF Research Database (Denmark)

    Blaabjerg, Frede; Teodorescu, Remus; Rodriguez, Pedro

    2008-01-01

    Fulfilling the new grid codes constitutes one of the main challenges for the wind power industry, that is specially concerned about the new fault-ride-through requirements. Enhancing the operation of wind-turbines in front of grid faults is not only an important issue for new wind farms, but also...

  19. Voltage Sag Source Location Based on Instantaneous Energy Detection

    DEFF Research Database (Denmark)

    Chen, Zhe; Kong, Wei; Dong, Xinzhou

    2008-01-01

    Voltage sag is a major power quality problem, which could disrupt the operation of voltage-sensitive equipment. This paper presents the method based on variation components-based instantaneous energy for voltage sag source detection. Simulations have been performed to provide the thorough analysis...... for system with distributed generation units. The studies show that the presented method can effectively detect the location of voltage sag source....

  20. An Enhanced LVRT Scheme for DFIG-based WECSs under Both Balanced and Unbalanced Grid Voltage Sags

    DEFF Research Database (Denmark)

    Mohammadi, Jafar; Afsharnia, Saeed; Ebrahimzadeh, Esmaeil

    2017-01-01

    Due to the latest grid codes, wind energy conversion systems (WECSs) are required to remain connected to grid under grid voltage sags and supply reactive power into the grid. So, this paper proposes an enhanced scheme to improve low-voltage ride through (LVRT) capability of doubly fed induction...... generator (DFIG)-based WECSs under both balanced and unbalanced grid voltage sags. The proposed scheme is composed of active and passive LVRT compensators. The active compensator is performed by controlling the rotor- and grid-side converters of the DFIG to decrease the stator flux oscillations and inject...... reactive power into the grid. The passive compensator is based on a three-phase stator damping resistor (SDR) located in series with the stator windings. The proposed scheme decreases the negative effects of grid voltage sags in the DFIG system including the rotor over-currents, electromagnetic torque...

  1. Reduced junction temperature control during low-voltage ride-through for single-phase photovoltaic inverters

    DEFF Research Database (Denmark)

    Yang, Yongheng; Wang, Huai; Blaabjerg, Frede

    2014-01-01

    Future photovoltaic (PV) inverters are expected to comply with more stringent grid codes and reliability requirements, especially when a high penetration degree is reached, and also to lower the cost of energy. A junction temperature control concept is proposed in this study for the switching...... devices in a single-phase PV inverter in order to reduce the junction temperature stress, and thus to achieve improved reliability of a PV inverter. The thermal stresses of the switching devices are analysed during low voltage ride-through operation with different levels of reactive power injection...

  2. Low-Voltage Ride-Through Capability of a Single-Stage Single-Phase Photovoltaic System Connected to the Low-Voltage Grid

    Directory of Open Access Journals (Sweden)

    Yongheng Yang

    2013-01-01

    Full Text Available The progressive growing of single-phase photovoltaic (PV systems makes the Distribution System Operators (DSOs update or revise the existing grid codes in order to guarantee the availability, quality, and reliability of the electrical system. It is expected that the future PV systems connected to the low-voltage grid will be more active with functionalities of low-voltage ride-through (LVRT and the grid support capability, which is not the case today. In this paper, the operation principle is demonstrated for a single-phase grid-connected PV system in a low-voltage ride-through operation in order to map future challenges. The system is verified by simulations and experiments. Test results show that the proposed power control method is effective and the single-phase PV inverters connected to low-voltage networks are ready to provide grid support and ride-through voltage fault capability with a satisfactory performance based on the grid requirements for three-phase renewable energy systems.

  3. Effects of unsymmetrical voltage sags on industrial adjustable speed drives

    Directory of Open Access Journals (Sweden)

    Petronijević Milutin P.

    2009-01-01

    Full Text Available This paper researches unsymmetrical voltage sag influence on torque ripple in scalar controlled (V/Hz, rotor field oriented (RFO and direct torque controlled (DTC drives. Electric drives performance degradation during voltage sag mainly depends on the used control algorithm. Industrial drives with all three types control methods are experimentally tested. Experiments with digital observer's application confirm the proposed solution. .

  4. Internal balance during low-voltage-ride-through of the modular multilevel converter statcom

    DEFF Research Database (Denmark)

    Tsolaridis, Georgios; Kontos, Epameinondas; Chaudhary, Sanjay K.

    2017-01-01

    Grid faults are common in power systems and can have a severe impact on the operation of the converters in the system. In this paper, the operation of a Modular Multilevel Converter (MMC)-based Static Synchronous Compensators (STATCOM) is investigated during grid faults. The study focuses...... on the challenging internal control of the converter to allow the independent control of the energy levels of each arm, with the goal to maintain internal balancing of the MMC during contingencies. Extensive experimental results highlight the need for a sophisticated internal control. Moreover, the experimental...... analysis verifies that, by using the proposed control structure, the MMC can effectively ride through a fault on the AC side without tripping, while injecting the necessary positive and negative sequence reactive current levels according to the most recent grid codes....

  5. A robust and fast generic voltage sag detection technique

    DEFF Research Database (Denmark)

    L. Dantas, Joacillo; Lima, Francisco Kleber A.; Branco, Carlos Gustavo C.

    2015-01-01

    In this paper, a fast and robust voltage sag detection algorithm, named VPS2D, is introduced. Using the DSOGI, the algorithm creates a virtual positive sequence voltage and monitories the fundamental voltage component of each phase. After calculating the aggregate value in the o:;3-reference frame......, the algorithm can rapidly identify the starting and the ending of symmetric and asymmetric voltage sags, even if there are harmonics on the grid. Simulation and experimental results are given to validate the proposed algorithm....

  6. Dynamic Stability Improvement of Grid Connected DFIG Using Enhanced Field Oriented Control Technique for High Voltage Ride Through

    Directory of Open Access Journals (Sweden)

    V. N. Ananth Duggirala

    2015-01-01

    Full Text Available Doubly fed induction generator (DFIG is a better alternative to increased power demand. Modern grid regulations force DFIG to operate without losing synchronism during overvoltages called high voltage ride through (HVRT during grid faults. Enhanced field oriented control technique (EFOC was proposed in Rotor Side Control of DFIG converter to improve power flow transfer and to improve dynamic and transient stability. Further electromagnetic oscillations are damped, improved voltage mitigation and limit surge currents for sustained operation of DFIG during voltage swells. The proposed strategy has advantages such as improved reactive power control, better damping of electromagnetic torque oscillations, and improved continuity of voltage and current from stator and rotor to grid during disturbance. In EFOC technique, rotor flux reference changes its value from synchronous speed to zero during fault for injecting current at the rotor slip frequency. In this process, DC-Offset component of stator flux is controlled so that decomposition during overvoltage faults can be minimized. The offset decomposition of flux will be oscillatory in a conventional FOC, whereas in EFOC it is aimed to be quick damping. The system performance with overvoltage of 1.3 times, 1.62 times, and 2 times the rated voltage occurring is analyzed by using simulation studies.

  7. A STATCOM with Supercapacitors for Low-Voltage Ride-Through in Fixed-Speed Wind Turbines

    Directory of Open Access Journals (Sweden)

    Andrés Felipe Obando-Montaño

    2014-09-01

    Full Text Available Fixed-speed wind generator (FSWG technology has an important presence in countries where wind energy started to be developed more than a decade ago. This type of technology cannot be directly adapted to the grid codes, for example those requirements related to the immunity level under voltage dips. That behavior is typically referred as low-voltage ride through (LVRT, and it usually implies certain reactive and active power injection requirements, both during a voltage dip and during the voltage recovery. In this context, a review is presented of the LVRT exigencies present in some of the countries with the most advanced grid codes (Denmark, Germany, Spain and the United Kingdom. In this paper, the capabilities of STATCOM-based devices for fulfilling the LVRT requirements in FSWGs are analyzed. For this purpose, two technologies are considered: a STATCOM with a supercapacitor, which improves its energy storage features; and a STATCOM with a supercapacitor and a DC-DC converter, to achieve higher discharge levels.

  8. Proportional-Resonant Control of Doubly-Fed Induction Generator Wind Turbines for Low-Voltage Ride-Through Enhancement

    Directory of Open Access Journals (Sweden)

    Zhan-Feng Song

    2012-11-01

    Full Text Available A novel control strategy is proposed in this paper for the rotor side converter (RSC of doubly-fed induction generator (DFIG-based wind power generation systems. It is supposed to enhance the low-voltage ride-through (LVRT capability of DFIGs during great-level grid voltage dips. The strategy consists of a proportional-resonant (PR controller and auxiliary PR controllers. The auxiliary controllers compensate the output voltage of the RSC in case of grid faults, thus limiting the rotor inrush current of DFIG and meeting the requirements of LVRT. Sequential-component decompositions of current are not required in the control system to improve the response of system. Since the resonant compensator is a double-side integrator, the auxiliary controllers can be simplified through coordinate transformation. The feasibility of the control strategy is validated by simulation on a 1.5 MW wind-turbine driven DFIG system. The impact of the RSC converter voltage rating on the LVRT capability of DFIG is investigated. Meanwhile, the influence of angular frequency detection and control parameters are also discussed. Compared with traditional vector control schemes based on PI current controllers, the presented control strategy effectively suppress rotor current and reduce oscillations of DFIG power and torque under grid faults.

  9. Voltage Sags Matching to Locate Faults for Underground Distribution Networks

    Directory of Open Access Journals (Sweden)

    BAKAR, A. H. A.

    2011-05-01

    Full Text Available A voltage sags matching to locate a fault for underground distribution network is presented in this paper. Firstly the method identifies the faulted section by matching a voltage sags measured at the primary substation during a fault with pre-developed voltage sag database. From the identified faulted section, the distance of a fault from sending-end is calculated. The problem of multiple sections is addressed by ranking approach. Test results on an underground distribution network shows most faults can be located by the first attempt within high accuracy distance. Only few faulted sections found by the second attempt. Since the method is using only voltage sag data, monitored at the primary substation, the method is considers economical to be implemented for a rural distribution network.

  10. Mitigation of voltage sag using DVR under feedback and ...

    African Journals Online (AJOL)

    Mitigation of voltage sag using DVR under feedback and feedforward control scheme. B Panda, S Behera. Abstract. The paper deals with Dynamic Voltage Restorer (DVR) that aims at the integration of series active filter with minimum VA handling. The DVR not only regulates the voltage at load end but also acts as series ...

  11. Thermal Optimized Operation of the Single-Phase Full-Bridge PV Inverter under Low Voltage Ride-Through Mode

    DEFF Research Database (Denmark)

    Wang, Huai; Yang, Yongheng; Blaabjerg, Frede

    2013-01-01

    The efficiency of 98% has been reported on transformer-less photovoltaic (PV) inverters and the penetration of grid-connected PV systems is booming as well. In the future, the PV systems are expected to contribute to the grid stability by means of low voltage ride-through operation and grid support...... on the power devices of a single-phase full-bridge PV inverter are analyzed in different operational modes in this paper. The low voltage grid condition is specially taken into account in this paper. The analysis is demonstrated by a 3 kW single-phase full-bridge grid-connected PV system by simulations....... At the same time, the target of a long service time (25 years or more) imposes new challenges to grid-connected transformer-less PV systems. Achieving more reliable PV inverters is of intense interest in recent research. As one of the most critical stresses that induce failures, the thermal stresses...

  12. FDI based on Artificial Neural Network for Low-Voltage-Ride-Through in DFIG-based Wind Turbine.

    Science.gov (United States)

    Adouni, Amel; Chariag, Dhia; Diallo, Demba; Ben Hamed, Mouna; Sbita, Lassaâd

    2016-09-01

    As per modern electrical grid rules, Wind Turbine needs to operate continually even in presence severe grid faults as Low Voltage Ride Through (LVRT). Hence, a new LVRT Fault Detection and Identification (FDI) procedure has been developed to take the appropriate decision in order to develop the convenient control strategy. To obtain much better decision and enhanced FDI during grid fault, the proposed procedure is based on voltage indicators analysis using a new Artificial Neural Network architecture (ANN). In fact, two features are extracted (the amplitude and the angle phase). It is divided into two steps. The first is fault indicators generation and the second is indicators analysis for fault diagnosis. The first step is composed of six ANNs which are dedicated to describe the three phases of the grid (three amplitudes and three angle phases). Regarding to the second step, it is composed of a single ANN which analysis the indicators and generates a decision signal that describes the function mode (healthy or faulty). On other hand, the decision signal identifies the fault type. It allows distinguishing between the four faulty types. The diagnosis procedure is tested in simulation and experimental prototype. The obtained results confirm and approve its efficiency, rapidity, robustness and immunity to the noise and unknown inputs. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

  13. Mitigation of Unbalanced Voltage Sags and Voltage Unbalance in CIGRE Low Voltage Distribution Network

    DEFF Research Database (Denmark)

    Mustafa, Ghullam; Bak-Jensen, Birgitte; Mahat, Pukar

    2013-01-01

    . The voltage problems dealt with in this paper are to show how to mitigate unbalanced voltage sags and voltage unbalance in the CIGRE Low Voltage (LV) test network and net-works like this. The voltage unbalances, for the tested cases in the CIGRE LV test network are mainly due to single phase loads and due...... to unbalanced faults. The compensation of unbalanced voltage sags and voltage unbalance in the CIGRE distribution network is done by using the four STATCOM compensators already existing in the test grid. The simulations are carried out in DIgSILENT power factory software version 15.0.......Any problem with voltage in a power network is undesirable as it aggravates the quality of the power. Power electronic devices such as Voltage Source Converter (VSC) based Static Synchronous Compensator (STATCOM) etc. can be used to mitigate the voltage problems in the distribution system...

  14. Power conditioning using dynamic voltage restorers under different voltage sag types

    Directory of Open Access Journals (Sweden)

    Ahmed M. Saeed

    2016-01-01

    Full Text Available Voltage sags can be symmetrical or unsymmetrical depending on the causes of the sag. At the present time, one of the most common procedures for mitigating voltage sags is by the use of dynamic voltage restorers (DVRs. By definition, a DVR is a controlled voltage source inserted between the network and a sensitive load through a booster transformer injecting voltage into the network in order to correct any disturbance affecting a sensitive load voltage. In this paper, modelling of DVR for voltage correction using MatLab software is presented. The performance of the device under different voltage sag types is described, where the voltage sag types are introduced using the different types of short-circuit faults included in the environment of the MatLab/Simulink package. The robustness of the proposed device is evaluated using the common voltage sag indices, while taking into account voltage and current unbalance percentages, where maintaining the total harmonic distortion percentage of the load voltage within a specified range is desired. Finally, several simulation results are shown in order to highlight that the DVR is capable of effective correction of the voltage sag while minimizing the grid voltage unbalance and distortion, regardless of the fault type.

  15. Power conditioning using dynamic voltage restorers under different voltage sag types.

    Science.gov (United States)

    Saeed, Ahmed M; Abdel Aleem, Shady H E; Ibrahim, Ahmed M; Balci, Murat E; El-Zahab, Essam E A

    2016-01-01

    Voltage sags can be symmetrical or unsymmetrical depending on the causes of the sag. At the present time, one of the most common procedures for mitigating voltage sags is by the use of dynamic voltage restorers (DVRs). By definition, a DVR is a controlled voltage source inserted between the network and a sensitive load through a booster transformer injecting voltage into the network in order to correct any disturbance affecting a sensitive load voltage. In this paper, modelling of DVR for voltage correction using MatLab software is presented. The performance of the device under different voltage sag types is described, where the voltage sag types are introduced using the different types of short-circuit faults included in the environment of the MatLab/Simulink package. The robustness of the proposed device is evaluated using the common voltage sag indices, while taking into account voltage and current unbalance percentages, where maintaining the total harmonic distortion percentage of the load voltage within a specified range is desired. Finally, several simulation results are shown in order to highlight that the DVR is capable of effective correction of the voltage sag while minimizing the grid voltage unbalance and distortion, regardless of the fault type.

  16. Comprehensive Reactive Power Support of DFIG Adapted to Different Depth of Voltage Sags

    Directory of Open Access Journals (Sweden)

    Yangwu Shen

    2017-06-01

    Full Text Available The low voltage ride-through (LVRT capability of the doubly-fed induction generator (DFIG significantly impacts upon the integration of wind power into the power grid. This paper develops a novel comprehensive control strategy to enhance the LVRT and reactive power support capacities of the DFIG by installing the energy storage system (ESS. The ESS is connected to the DC-link capacitor of the DFIG and used to regulate the DC-link voltage during normal or fault operations. The unbalanced power between the captured wind power and the power injected to the grid during the transient process is absorbed or compensated by the ESS. The rotor-side converter (RSC is used to control the maximum power production and the grid-side converter (GSC is used to control the reactive power before participating in the voltage support. When the supply voltage continues to drop, the rotor speed is increased by controlling the RSC to realize the LVRT capability and help the GSC further enhance the reactive power support capability. The capacity of the GSC is dedicated to injecting the reactive power to the grid. An auxiliary transient pitch angle controller is proposed to protect the generator’s over speed. Both RSC and GSC act as reactive power sources to further enhance the voltage support capability with serious voltage sags. Simulations based on a single-machine infinite-bus power system verify the effectiveness of the developed comprehensive control strategy.

  17. Fault Ride-Through of a Grid-connected Photovoltaic System with Quasi Z Source Inverter

    DEFF Research Database (Denmark)

    Al-Durra, Ahmed; Fayyad, Yara; Muyeen, S.M.

    2016-01-01

    This article presents fault ride-through schemes for a three-phase quasi Z source single-stage photovoltaic (PV) inverter that is connected to the grid after the distribution network. The quasi Z source inverter employs a unique LC network to couple the inverter main circuit to the input of the PV...... panel. By controlling the shoot-through duty cycle, the quasi Z source inverter can theoretically produce any desired output AC voltage, even greater than the line voltage. Three different control strategies to improve the low-voltage ride-through capability are proposed when there is voltage sag from...... the grid side so that the grid fault ride-through requirements can be fulfilled. Scheme A involves control modification in the system; Schemes B and C involve hardware modification in the circuit topology by adding a chopper circuit across the DC link in Scheme B and across the quasi Z source inverter...

  18. Allocation of Load-Loss Cost Caused by Voltage Sag

    Science.gov (United States)

    Gao, X.

    2017-10-01

    This paper focuses on the allocation of load-loss cost caused by voltage sag in the environment of electricity market. To compensate the loss of loads due to voltage sags, the load-loss cost is allocated to both sources and power consumers. On the basis of Load Drop Cost (LDC), a quantitative evaluation index of load-loss cost caused by voltage sag is identified. The load-loss cost to be allocated to power consumers themselves is calculated according to load classification. Based on the theory of power component the quantitative relation between sources and loads is established, thereby a quantitative calculation method for load-loss cost allocated to each source is deduced and the quantitative compensation from individual source to load is proposed. A simple five-bus system illustrates the main features of the proposed method.

  19. Early Prediction of Transient Voltage Sags caused by Rotor Swings

    DEFF Research Database (Denmark)

    Weckesser, Johannes Tilman Gabriel; Jóhannsson, Hjörtur; Van Cutsem, Thierry

    2014-01-01

    The paper investigates various methods to predict voltage sags at load buses caused by large generator rotor swings and following a transient disturbance. Three different prediction methods are proposed, which all use real-time measurements from PMUs. One of the methods uses a slightly extended...... version of the E-SIME method. The other two methods use Measurements and process them by recursive least square estimation. It is shown that the prediction method employing E-SIME allows the earliest detection of a critical voltage sag with satisfactory accuracy....

  20. Responsive demand to mitigate slow recovery voltage sags

    DEFF Research Database (Denmark)

    Garcia-Valle, Rodrigo; da Silva, Luiz Carlos Pereira; Xu, Zhao

    2012-01-01

    can be provided by thermostatically controlled loads as well as other types of load. This technology has proven to be effective in distribution systems with a large composition of induction motors, when voltage sags present slow recovery characteristics because of the deceleration of the motors during...

  1. The state of the art and new developments in voltage sag immunity

    Directory of Open Access Journals (Sweden)

    Joaquín Caicedo

    2011-06-01

    Full Text Available This paper presents the state of the art regarding electrical equipment’s immunity to voltage sags. It deals with immunity analysis and voltage sag generators. An alternative methodology for testing equipment regarding voltage sag is proposed, along with immunity assessment. A comprehensive bibliographic review was made, describing voltage sag immunity standards and selected research and industry publications. The proposed methodology for assessing immunity was based on the literature presented and the authors’ work.

  2. The influence of transformers, induction motors and fault resistance regarding propagation voltage sags

    Directory of Open Access Journals (Sweden)

    Jairo Blanco

    2011-06-01

    Full Text Available This article presents an analysis of voltage sag propagation. The ATPDraw tool was selected for simulating the IEEE 34 node test feeder. It takes into account both voltage sags caused by electrical fault network, as well as voltage sag propagation characteristics caused by induction motor starting and transformer energising. The analysis was aimed at assessing the influence of transformer winding connections, the impedance of these transformers, lines and cables, summarising the effects on disturbance magnitude and phase. The study shows that the influence of an induction motor on voltage sag propagation results in increased voltage sag severity. Voltage sags caused by induction motor starting and transformer energising have no zero-sequence component, so they are only affected by type 3 transformers. The influence of fault resistance on voltage sag magnitude and phase characteristics is examined and some aspects of interest in characterising these electromagnetic disturbances is identified.

  3. The influence of transformers, induction motors and fault resistance regarding propagation voltage sags

    Directory of Open Access Journals (Sweden)

    Jairo Blanco

    2011-07-01

    Full Text Available This article presents an analysis of voltage sag propagation. The ATPDraw tool was selected for simulating the IEEE 34 node test feeder. It takes into account both voltage sags caused by electrical fault network, as well as voltage sag propagation characteristics caused by induction motor starting and transformer energising. The analysis was aimed at assessing the influence of transformer winding connections, the impedance of these transformers, lines and cables, summarising the effects on disturbance magnitude and phase. The study shows that the influence of an induction motor on voltage sag propagation results in increased voltage sag severity. Voltage sags caused by induction motor starting and transformer energising have no zero-sequence component, so they are only affected by type 3 transformers. The influence of fault resistance on voltage sag magnitude and phase characteristics is examined and some aspects of interest in characterising these electromagnetic disturbances is identified.

  4. Modulation Methods for Neutral-Point-Clamped Wind Power Converter Achieving Loss and Thermal Redistribution Under Low-Voltage Ride-Through

    DEFF Research Database (Denmark)

    Ma, Ke; Blaabjerg, Frede

    2014-01-01

    The three-level neutral-point (NP)-clamped (3L-NPC) converter is a promising multilevel topology in the application of megawatt wind power generation systems. However, the growing requirements by grid codes may impose high stress and even give reliability problem to this converter topology....... This paper investigates the loss and thermal performances of a 10-MW 3L-NPC wind power inverter undergoing low-voltage ride-through (LVRT) operation. A series of new space vector modulation methods is then proposed to relocate the thermal loading among the power switching devices. It is concluded that...

  5. Loss and thermal redistributed modulation methods for three-level neutral-point-clamped wind power inverter undergoing Low Voltage Ride Through

    DEFF Research Database (Denmark)

    Ma, Ke; Blaabjerg, Frede

    2012-01-01

    The three-level neutral-point-clamped (3L-NPC) converter is a promising multilevel topology in the application of mega-watts wind power generation system. However, the growing requirements by grid codes may impose high stress and even give reliability problem to this converter topology. This paper...... investigates the loss and thermal performances of a 10 MW 3L-NPC wind power inverter undergoing Low Voltage Ride Through (LVRT) operation. A series of new space vector modulation methods are then proposed to relocate the thermal loading among the power switching devices. It is concluded that, with the proposed...

  6. Computational Intelligence Methods for Identifying Voltage Sag in Smart Grid

    Directory of Open Access Journals (Sweden)

    Turgay Yalcin

    2017-05-01

    Full Text Available In recent years pattern recognition of power quality (PQ disturbances in smart grids has developed into crucial topic for system equipments and end-users. Undoubtedly analyzing the PQ disturbances develop and maintain smart grids effectiveness. Voltage sags are the most common events that affect power quality. These faults are also the most costly. This paper represents performance comparisons of different computer intelligence methods for voltage sag identification. PQube Analyzer which is installed in Ondokuz Mayis University Computer Laboratory for collecting real time disturbances data for each three phases in order to test for proposed algorithms. Firstly, we used Hilbert Huang Transform to genarate Instantaneous Amplitude (IA feature signal. Then Characteristic features are attained from IA. The 4 features, mean, standard deviation, skewness, kurtosis of IA are calculated. Support Vector Machines (SVMs and C4.5 Decision Tree methods are conducted for classification of the disturbance. Secondly we used Fishers Discriminant Ratio for selecting statistical features such as mean, standard deviation, skewness and kurtosis of the normal and voltage sag signals for this part K Means Clustering Method were performed for classification of the disturbance. Consecuently, SVMs, C4.5 Decision Tree and K Means Clustering Methods were performed also their achievements were matched for error rates and CPU timing

  7. Research on uncertainty evaluation measure and method of voltage sag severity

    Science.gov (United States)

    Liu, X. N.; Wei, J.; Ye, S. Y.; Chen, B.; Long, C.

    2018-01-01

    Voltage sag is an inevitable serious problem of power quality in power system. This paper focuses on a general summarization and reviews on the concepts, indices and evaluation methods about voltage sag severity. Considering the complexity and uncertainty of influencing factors, damage degree, the characteristics and requirements of voltage sag severity in the power source-network-load sides, the measure concepts and their existing conditions, evaluation indices and methods of voltage sag severity have been analyzed. Current evaluation techniques, such as stochastic theory, fuzzy logic, as well as their fusion, are reviewed in detail. An index system about voltage sag severity is provided for comprehensive study. The main aim of this paper is to propose thought and method of severity research based on advanced uncertainty theory and uncertainty measure. This study may be considered as a valuable guide for researchers who are interested in the domain of voltage sag severity.

  8. Modeling and Simulation of Dynamic Voltage Restorer (DVR for Enhancing Voltage Sag

    Directory of Open Access Journals (Sweden)

    Amrita RAI

    2008-01-01

    Full Text Available The aim of this paper is to summaries the fundamental aspects of voltage sag production and their effects on power quality as well as enhancing this power quality in distribution network, using FACTS (Flexible AC Transmission System Devices i.e. Dynamic Voltage Restorer (DVR. DVR is a powerful custom power device for short duration voltage compensation, which is connected in series with the load & hence it possesses some advantages. (In this paper detailed modeling and simulation and analysis of the DVR device is presented.

  9. A Comprehensive Review of Low-Voltage-Ride-Through Methods for Fixed-Speed Wind Power Generators

    DEFF Research Database (Denmark)

    Moghadasi, Amirhasan; Sarwat, Arif; Guerrero, Josep M.

    2016-01-01

    complexity, and economic feasibility. A novel feature of this paper is to categorize LVRT capability enhancement approaches into three main groups depending on the connection configuration: series, shunt, and series-shunt (hybrid) connections and then discuss their advantages and limitations in detail....... For verification purposes, several simulations are presented in MATLAB software to demonstrate and compare the reviewed LVRT schemes. Based on the simulated results, series connection dynamic voltage restorer (DVR) and shunt connection static synchronous compensators (STATCOM) are the highly efficient LVRT...

  10. Methodology for Determination of the Number of Equipment Malfunctions Due to Voltage Sags

    Directory of Open Access Journals (Sweden)

    Alena Otcenasova

    2017-03-01

    Full Text Available This article deals with the assessment of the reliability of sensitive equipment due to voltage sags. The most frequent problems of power quality are voltage sags. Equipment that cannot withstand short-term voltage sag is defined as sensitive device. Sensitivity of such equipment can be described by the voltage–tolerance curves. A device (generator to generate voltage sags (also interruptions with duration at least 1 ms has been designed and developed for this purpose. Equipment sensitive to voltage sags was tested using this generator. Overall, five types of sensitive equipment were tested: personal computers, fluorescent lamps, drives with speed control, programmable logic controllers, and contactors. The measured sensitivity curves of these devices have been used to determine the number of trips (failures due to voltage sags. Two probabilistic methods (general probability method and cumulative probability method to determine probability of equipment failure occurrence are used. These methods were applied to real node in the distribution system with its actual performance of voltage sags/swells. The calculations also contain different levels of sensitivity of the sensitive equipment.

  11. Fault ride-through capability of wind turbine connected to the grid in case of unbalanced voltages

    Directory of Open Access Journals (Sweden)

    Ivanović Zoran R.

    2016-01-01

    Full Text Available This paper deals with control of wind turbine connected to the grid through the back-to-back converter in case of unbalanced grid voltages. The motivation for this research has been found in recent transmission and distribution grid code, which demand modern wind turbines to stay connected to the grid and supply the highest possible apparent power during the grid disturbances. In order to comply with these requirements we proposed improved dual vector current controller to deal with the unbalance imposed by the electrical grid. Controller provides injection of active and reactive power to the grid, even if the voltages are lower than the nominal one. The results are validated using low power prototype and contemporary hardware-in-the-loop emulation platform. In both cases the controller is based on TMS320F2812 DSP. [Projekat Ministarstva nauke Republike Srbije, br. III 042004 and by the Provincial Secretariat for Science and Technological Development of AP Vojvodina under contract No. 114-451-3508/2013-04

  12. Effect of voltage sags on digitally controlled line connected switched-mode power supplies

    DEFF Research Database (Denmark)

    Török, Lajos; Munk-Nielsen, Stig

    2012-01-01

    Different voltage disorders like voltage fluctuations, sags, frequency variations may occur in the power supply networks due to different fault conditions. These deviations from normal operation affects in different ways the line connected devices. Standards were developed to protect and ensure...... of voltage sags is analyzed. Fault tolerant control algorithm was designed, implemented and is discussed. The fault conditions and their effects were investigated at different power levels....

  13. Factor affecting characteristic of voltage sag due to fault in the power system

    Directory of Open Access Journals (Sweden)

    Patne Nita R.

    2008-01-01

    Full Text Available Faults in the power system are the most common reason for the occurrence of important power quality problem, voltage sag in the system. Due to increasing use of sensitive and sophisticated control in almost all modern devices at the industrial and residential consumer level, the Voltage sag which causes severe problems to these devices needs to be analyzed. Factors which affect the characteristics of voltage sag as a type of fault in the system, location of fault in the system, X/R ratio of transmission lines, type of transmission as single or double circuit transmission, Point on wave of sag initiation are studied in this paper. PSCAD/EMTDC is used as a simulation tool.

  14. Electronic Power Transformer Control Strategy in Wind Energy Conversion Systems for Low Voltage Ride-through Capability Enhancement of Directly Driven Wind Turbines with Permanent Magnet Synchronous Generators (D-PMSGs

    Directory of Open Access Journals (Sweden)

    Hui Huang

    2014-11-01

    Full Text Available This paper investigates the use of an Electronic Power Transformer (EPT incorporated with an energy storage system to smooth the wind power fluctuations and enhance the low voltage ride-through (LVRT capability of directly driven wind turbines with permanent magnet synchronous generators (D-PMSGs. The decoupled control schemes of the system, including the grid side converter control scheme, generator side converter control scheme and the control scheme of the energy storage system, are presented in detail. Under normal operating conditions, the energy storage system absorbs the high frequency component of the D-PMSG output power to smooth the wind power fluctuations. Under grid fault conditions, the energy storage system absorbs the redundant power, which could not be transferred to the grid by the EPT, to help the D-PMSG to ride through low voltage conditions. This coordinated control strategy is validated by simulation studies using MATLAB/Simulink. With the proposed control strategy, the output wind power quality is improved and the D-PMSG can ride through severe grid fault conditions.

  15. Performance Improvement of DFIG Wind Turbine Using Series Grid-Side Converter under Unbalanced Grid Voltage and Voltage Sag Conditions

    DEFF Research Database (Denmark)

    Shokri, Yunes; Ebrahimzadeh, Esmaeil; Lesani, Hamid

    2014-01-01

    at twice the supply frequency. This paper presents a modified configuration of DFIG with series grid-side converter (SGSC) and its control system, which is suitable not only for unbalanced grid voltage conditions, but also for small voltage sags. The proposed configuration improves all the DFIG signals...... under unbalanced grid voltage and small voltage sag conditions without needing additional DC link capacitor or energy storage unlike other methods. The control system includes negative and positive sequence controllers which make the stator voltage balanced and keep it constant at the nominal value......Under unbalanced grid voltage conditions, the doubly fed induction generator (DFIG) stator voltage, in addition to positive sequence component has negative sequence component. The negative sequence component causes oscillations in the output power, electromagnetic torque and DC link voltage...

  16. Immunity of industrial equipment against voltage sags; Imunidade de equipamentos industriais a afundamentos de tensao

    Energy Technology Data Exchange (ETDEWEB)

    Bollen, Math H.J. [Smithsonian Tropical Research Institution (STRI), Stockholm (Sweden); Gordon, Jose Romero [Endesa (Spain); Djokic, Sasa Z. [The University of Edinburgh (United Kingdom); Milanovic, Jovina V. [University of Manchester (United Kingdom); Neuman, Robert [Qualitrol (United Kingdom); Stockman, Kurt [Ghent University (Belgium); Ethier, Gaetan [Hydro Quebec (Canada)

    2011-11-15

    The voltage sags, which consists of short-term reductions of the magnitude of the voltage, may damage the operation of end user equipment and even disrupt industrial processes, resulting in large losses. This article details the characterization, class and economic value, among other things, of the immunity of the equipment against these phenomena.

  17. An evaluation method of voltage sag using a risk assessment model in power distribution systems

    Energy Technology Data Exchange (ETDEWEB)

    Sang Yun Yun [LG Industrial Systems, Cheongju (Korea). Electrotechnology R and D Center; Jae Chul Kim [Soongsil Univ., Seoul (Korea). Dept. of Electrical Engineering

    2003-12-01

    In this paper we explore a new method for evaluating the impact of voltage sags in the power distribution systems. The proposed method incorporates the generalization of the evaluation method as well as the effects of voltage sags on customers. To generalize the evaluation method, historical reliability data will be used. We take into account the impact of voltage sags on customers using a representative power acceptability curve and a fuzzy model. The final result of the evaluation model yields on a yearly basis the magnitude of customers' risk caused by voltage sags. The evaluation methodology is divided into the analytic and probabilistic method. The time sequential Monte Carlo simulation is used as probabilistic method. The proposed method is tested using the modified Roy Billinton Test System (RBTS) form and the reliability data of Korea Electric Power Corporation (KEPCO) system. Through the case study, we verify that the proposed method evaluate the actual impact of voltage sags and can be effectively applied to the real system using the historical reliability data as the conventional reliability indices in power distribution systems. (author)

  18. Impact of Distributed Generation on the Voltage Sag Performance of Transmission Systems

    Directory of Open Access Journals (Sweden)

    Pierluigi Caramia

    2017-07-01

    Full Text Available In this paper, we analysed the growing penetration of generating units from renewable energy sources in transmission power systems. Among the possible effects of the interaction of distributed generation (DG with transmission systems, we considered the abnormal operating conditions caused by short circuits in the transmission systems and the resulting voltage sags that occur in the network. A systematic method is presented for analysing the voltage sag behaviour of any transmission system in which large DG units are connected to the transmission system by means of High Voltage/Medium Voltage (HV/MV stations. The method proposed for obtaining the voltage sags is the fault position method (FPM, from which we derived a graphical visualization of the during-fault voltage (DFV matrix as a valuable tool to obtain an immediate measure of the propagation of voltage sags in the network. The results obtained were based on a portion of a real transmission system. The system that we considered is an actual portion of the Italian transmission system, and all of the quantities we used were obtained from the data of the Transmission system operator (TSO.

  19. Analysis and Design of a DSTATCOM Based on Sliding Mode Control Strategy for Improvement of Voltage Sag in Distribution Systems

    Directory of Open Access Journals (Sweden)

    Ghazanfar Shahgholian

    2016-07-01

    Full Text Available Voltage sag is considered to be the most serious problem of power quality. It is caused by faults in the power system or by the starting of large induction motors. Voltage sag causes about 80% of the power quality problems in power systems. One of the main reasons for voltage sag is short circuit fault, which can be compensated for by a distribution static compensator (DSTATCOM as an efficient and economical flexible AC transmission system (FACTS device. In this paper, compensation of this voltage sag using DSTATCOM is reviewed, in which a sliding mode control (SMC technique is employed. The results of this control system are compared with a P+Resonant control system. It will be shown that this control system is able to compensate the voltage sag over a broader range compared to other common control systems. Simulation results are obtained using PSCAD/EMTDC software and compared to that of a similar method.

  20. Voltage sag influence on fatigue life of the drivetrain of fixed speed wind turbines

    DEFF Research Database (Denmark)

    Veluri, Badrinath; Santos-Martin, David; Jensen, Henrik Myhre

    2011-01-01

    Occurrence of voltage sags due to electrical grid faults and other network disturbances generate transients of the generator electromagnetic torque which result in significant high stresses and noticeable vibrations for the wind turbine mechanical system and may also have a detrimental effect...

  1. Heat-pump performance: voltage dip/sag, under-voltage and over-voltage

    Directory of Open Access Journals (Sweden)

    William J.B. Heffernan

    2014-12-01

    Full Text Available Reverse cycle air-source heat-pumps are an increasingly significant load in New Zealand and in many other countries. This has raised concern over the impact wide-spread use of heat-pumps may have on the grid. The characteristics of the loads connected to the power system are changing because of heat-pumps. Their performance during under-voltage events such as voltage dips has the potential to compound the event and possibly cause voltage collapse. In this study, results from testing six heat-pumps are presented to assess their performance at various voltages and hence their impact on voltage stability.

  2. CLASSIFICATION OF POWER QUALITY CONSIDERING VOLTAGE SAGS IN DISTRIBUTION SYSTEMS USING KDD PROCESS

    Directory of Open Access Journals (Sweden)

    Anderson Roges Teixeira Góes

    2015-08-01

    Full Text Available In this paper, we propose a methodology to classify Power Quality (PQ in distribution systems based on voltage sags. The methodology uses the KDD process (Knowledge Discovery in Databases in order to establish a quality level to be printed in labels. The methodology was applied to feeders on a substation located in Curitiba, Paraná, Brazil, considering attributes such as sag length (remnant voltage, duration and frequency (number of occurrences on a given period of time. On the Data Mining Stage (the main stage on KDD Process, three different techniques were used, in a comparative way, for pattern recognition, in order to achieve the quality classification for the feeders: Artificial Neural Networks (ANN; Support Vector Machines (SVM and Genetic Algorithms (GA. By printing a label with quality level information, utilities companies (power concessionaires can get better organized for mitigation procedures by establishing clear targets. Moreover, the same way costumers already receive information regarding PQ based on interruptions, they will also be able to receive information based on voltage sags.

  3. Sensitivity based Assessment of Transient Voltage Sags caused by Rotor Swings

    DEFF Research Database (Denmark)

    Weckesser, Johannes Tilman Gabriel; Jóhannsson, Hjörtur; Østergaard, Jacob

    2014-01-01

    The paper introduces an approach to investigate voltage sags, which are caused by large generator rotor swings following a transient disturbance. Therefore, the method exploits sensitivities derived from the algebraic network equations. These provide information on the impact of a generator...... on the voltage magnitude at a load bus and the effect of load variation on the generator’s power injection. It is shown that these sensitivities give valuable information to identify critical generator-load pairs and locations for applying preventive control measures....

  4. Derivation and application of sensitivities to assess transient voltage sags caused by rotor swings

    DEFF Research Database (Denmark)

    Weckesser, Johannes Tilman Gabriel; Jóhannsson, Hjörtur; Østergaard, Jacob

    2015-01-01

    The paper introduces an approach to investigate voltage sags, which are caused by large generator rotor swings following a transient disturbance. Therefore, the method exploits sensitivities derived from the algebraic network equations. These provide information on the impact of a generator...... on the voltage magnitude at a load bus and the effect of load variation on the generator’s power injection. It is shown that these sensitivities give valuable information to identify critical generator–load pairs and locations for applying preventive control measures....

  5. Analysis of doubly-fed induction machine operating at motoring mode subjected to voltage sag

    Directory of Open Access Journals (Sweden)

    Navneet Kumar

    2016-09-01

    Full Text Available Variable Speed (VS Pumped Storage Plants (PSP equipped with large asynchronous (Doubly-Fed Induction machines are emerging now in hydropower applications. Motoring mode of operation of Doubly-Fed Induction Machine (DFIM is essential and techno-economical in this application due to: (1 its uniqueness in active power controllability, (2 bulk power handing capability with less rated power converters in rotor circuit, and (3 integrating Renewable Energy Sources (RES. This paper investigates the performance of two DFIMs at different power ratings (2.2 kW and 2 MW under voltage sag with different attribute. The test results are analyzed in terms of the peaks in torque, speed, power taken and transient currents in rotor and stator circuits. During sag, stable region for DFIM operation along with speed and stator side reactive power input control is also illustrated. The negative effects of voltage sag are briefly discussed. MATLAB simulation is validated with experimentation. The various observations during simulation and experimental analysis are also supported by the theoretical explanations.

  6. Asymmetrical Grid Fault Ride-Through Strategy of Three-phase Grid-connected Inverter Considering Network Impedance Impact in Low Voltage Grid

    DEFF Research Database (Denmark)

    Guo, Xiaoqiang; Zhang, Xue; Wang, Baocheng

    2014-01-01

    inductive, the proposed control strategy is more flexible and effective by considering the network impedance impact, which is of great importance for the high penetration of grid-connected renewable energy systems into low-voltage grids. The experimental tests are carried out to validate the effectiveness...... of the proposed solution for the flexible voltage support in a low-voltage grid, where thenetwork impedance is mainly resistive....

  7. Second-order sliding mode control for DFIG-based wind turbines fault ride-through capability enhancement.

    Science.gov (United States)

    Benbouzid, Mohamed; Beltran, Brice; Amirat, Yassine; Yao, Gang; Han, Jingang; Mangel, Hervé

    2014-05-01

    This paper deals with the fault ride-through capability assessment of a doubly fed induction generator-based wind turbine using a high-order sliding mode control. Indeed, it has been recently suggested that sliding mode control is a solution of choice to the fault ride-through problem. In this context, this paper proposes a second-order sliding mode as an improved solution that handle the classical sliding mode chattering problem. Indeed, the main and attractive features of high-order sliding modes are robustness against external disturbances, the grids faults in particular, and chattering-free behavior (no extra mechanical stress on the wind turbine drive train). Simulations using the NREL FAST code on a 1.5-MW wind turbine are carried out to evaluate ride-through performance of the proposed high-order sliding mode control strategy in case of grid frequency variations and unbalanced voltage sags. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

  8. Distribution-Connected PV's Response to Voltage Sags at Transmission-Scale

    Energy Technology Data Exchange (ETDEWEB)

    Mather, Barry; Ding, Fei

    2016-11-21

    The ever increasing amount of residential- and commercial-scale distribution-connected PV generation being installed and operated on the U.S.'s electric power system necessitates the use of increased fidelity representative distribution system models for transmission stability studies in order to ensure the continued safe and reliable operation of the grid. This paper describes a distribution model-based analysis that determines the amount of distribution-connected PV that trips off-line for a given voltage sag seen at the distribution circuit's substation. Such sags are what could potentially be experienced over a wide area of an interconnection during a transmission-level line fault. The results of this analysis show that the voltage diversity of the distribution system does cause different amounts of PV generation to be lost for differing severity of voltage sags. The variation of the response is most directly a function of the loading of the distribution system. At low load levels the inversion of the circuit's voltage profile results in considerable differences in the aggregated response of distribution-connected PV Less variation is seen in the response to specific PV deployment scenarios, unless pushed to extremes, and in the total amount of PV penetration attained. A simplified version of the combined CMPLDW and PVD1 models is compared to the results from the model-based analysis. Furthermore, the parameters of the simplified model are tuned to better match the determined response. The resulting tuning parameters do not match the expected physical model of the distribution system and PV systems and thus may indicate that another modeling approach would be warranted.

  9. Coordinated Control of a Doubly-Fed Induction Generator-Based Wind Farm and a Static Synchronous Compensator for Low Voltage Ride-through Grid Code Compliance during Asymmetrical Grid Faults

    Directory of Open Access Journals (Sweden)

    Hua Geng

    2013-09-01

    Full Text Available This paper aims to explore a viable solution for a doubly-fed induction generator (DFIG-based wind farm to meet the reactive support requirement of the low voltage ride-through (LVRT grid code with safe grid-connected operation during asymmetrical grid faults. First, the control scheme for the DFIG-based wind energy conversion system (WECS is designed. Then, the controllability issue is analyzed by means of an optimal method, and the derived controllable regions indicate that the DFIG-based WECS can only remain controllable under mild asymmetrical fault situations. Afterwards, the static synchronous compensator (STATCOM is introduced as extra equipment to ensure that the DFIG-based wind farm remains controllable under severe asymmetrical fault situations. For this purpose, a voltage compensation control scheme and a corresponding capacity matching method for the STATCOM are proposed. The simulation results verify that, with the proposed coordinated control between the DFIG-based wind farm and the STATCOM, the required positive-sequence reactive current can be supplied to support the power grid. The oscillations on the electromagnetic torque and direct current (DC-link voltage of the DFIG-based WECS can also be eliminated. Therefore, the control scheme can be helpful to improve the reliability of both the wind farm and the power system during grid faults.

  10. Electromechanical performance of induction motor/drive systems subjected to voltage sags

    Science.gov (United States)

    Tunaboylu, Serdar N.

    Induction Motors are workhorses for many industries. They are extensively utilized in industrial variable-frequency drive (VFD) or adjustable-speed drive (ASD) applications as well as constant speed applications. Recent advances in power electronics have made AC motor drives an economically viable solution for ASD applications traditionally dominated by dc motor drives. In this study, electromechanical performance variables of an Induction Motor (IM) have been studied during the balanced voltage sags. For this purpose a laboratory prototype of an industrial mixer has been designed. IM has been coupled to a speed reducer that is worm gear type with a ratio 10 to 1. Then the reducer is vertically coupled to a food process mixer within a metal canister. The mixer represents a high friction load with practically zero inertia. Voltage, current, speed, and power measurements have been collected and compared with the simulation results from Simnon. An open-loop control Volts per Hertz boost strategy has been used in order to compensate the speed loss during the three-phase balanced voltage sags. Both compensated and uncompensated cases have been run and compared with simulation results. Results are verified with a reasonably good agreement that the total system modeling is successful and boost compensation circuit is effective.

  11. Power Quality Improvement And Mitigation Of Voltage Sag And Current Swell Using Distributed Power Flow Controller

    OpenAIRE

    P. Nirmala; SK.SAJIDA

    2014-01-01

    Modern power utilities have to respond to a number of challenges such as growth of electricity demand specially in non-linear loads in power grids, consequently, That higher power quality should be considered. In this paper, DPFC which is similar to unified power flow controller (UPFC) in structure, which is used to mitigate the voltage sag and swell as a power quality issue. Unlike UPFC, the common dc-link in DPFC, between the shunt and series converter devices should be eliminated and three...

  12. Analisa Pengaruh Koordinasi Peralatan Proteksi Terhadap Karakteristik Voltage Sag Di PT. Pupuk Kaltim (PKT Bontang

    Directory of Open Access Journals (Sweden)

    Arif Rakhman Prayuga

    2012-09-01

    Full Text Available Program paket merupakan software simulasi transien pada sistem tenaga yang digunakan untuk menganalisa pengujian jaringan listrik di industri pada kondisi saat gangguan. Untuk meneliti karakteristik voltage sag pada sistem jaringan listrik di industri dalam kondisi saat gangguan, digunakan dua metode untuk koordinasi peralatan proteksi. Keluaran dari hasil simulasi berupa kurva transien tegangan terhadap durasi waktu gangguan yang merupakan karakteristik voltage sag. Kurva hasil simulasi ini dievaluasi dengan kurva standar CBEMA, ITIC, dan SEMI yang telah distandarkan untuk performa jaringan. Hasil simulasi hubung singkat 3 fasa di titik Fault 2 menyebabkan tegangan sisa sebesar 88,4 % di tiap fasa, hubung singkat 1 fasa ke tanah sebesar 81,4 % di fasa A, 98,6 % di fasa B, dan 96,2 % di fasa C, hubung singkat antar fasa sebesar 92,6 % di fasa A, 105,9 % di fasa B, 87,6 % di fasa C. Metode kedua yaitu dengan CB atau pemutus dari hasil evaluasi simulasi didapatkan durasi gangguan yang lebih kecil dari metode pertama yaitu tanpa peralatan proteksi.

  13. Mitigation of voltage sag, swell and power factor correction using solid-state transformer b

    Directory of Open Access Journals (Sweden)

    M.R. Banaei

    2014-09-01

    Full Text Available This paper presents a novel topology of solid-state transformer (SST. In the design process, the AC/DC, DC/AC and AC/AC converters have been integrated to achieve higher efficiency. To obtain higher efficiency from other SST with DC-link topologies, the AC/DC and DC/AC converters have been integrated in one matrix converter. The proposed SST performs typical functions and has advantages such as power factor correction, voltage sag and swell elimination, voltage flicker reduction and protection capability in fault situations. In addition, it has other benefits such as light weight, low volume and elimination of hazardous liquid dielectrics because it uses medium frequency transformer. The operation and some performances of the proposed SST have been verified by the simulation results.

  14. An algorithm for reduction of extracted power from photovoltaic strings in grid-tied photovoltaic power plants during voltage sags

    DEFF Research Database (Denmark)

    Tafti, Hossein Dehghani; Maswood, Ali Iftekhar; Pou, Josep

    2016-01-01

    , the injected active power should be reduced during voltage sags. In order to obtain a constant dc-link voltage in a multi-string PVPP, the extracted power from PV strings should be equal to the injected power to the grid in all operating conditions (excluding power losses). Therefore, the extracted power of PV...... strings should be reduced during voltage sags. In this paper, an algorithm is proposed for determining the reference voltage of the PV string which results in a reduction of the output power to a certain amount. The proposed algorithm calculates the reference voltage for the dc/dc converter controller......, based on the characteristics of the power-voltage curve of the PV string and therefore, no modification is required in the the controller of the dc/dc converter. Simulation results on a 50-kW PV string verified the effectiveness of the proposed algorithm in reducing the power from PV strings under...

  15. Effect of recovery time of fault current limiter on over current from distributed generator in micro grid after voltage sag

    Directory of Open Access Journals (Sweden)

    Daisuke Iioka

    2016-01-01

    Full Text Available This paper describes an effect of recovery time of fault current limiter on over current from a micro grid system which is interconnected to a power distribution system. We have assumed that the semi-conductor type fault current limiter is installed between the micro grid system with the synchronous generator and the power distribution system, measured the over current after a voltage sag occurrence in the power distribution system and a recovery of fault current limiter by experiments in our laboratory. Finally, it was found that the introduction of recovery time for fault current limiter after voltage sag is useful for suppressing the over current from the distributed generator.

  16. Current source converter based D-STATCOM for voltage sag mitigation

    Directory of Open Access Journals (Sweden)

    Singh Moirangthem Deben

    2015-01-01

    Full Text Available This paper presents a novel method of realizing one of the custom power controllers, the distribution static synchronous compensator (D-STATCOM using current source converter (CSC topology. Almost all the custom power controllers such as dynamic voltage restorer (DVR, unified power quality conditioner (UPQC including D-STATCOM are generally designed and implemented by using voltage source converters (VSC and not much research publications with CSC based approach has been reported over the last one decade. Since the D-STATCOM is a current injection device, its performance can be improved when realized by a current-source converter which can generate a controllable current directly at its output terminals and offers many advantageous features. In this paper, an attempt has been made to study the performance of a CSC based D-STATCOM suitable for use in the power distribution system in order to mitigate voltage sag and improve power quality. The proposed model uses a three leg CSC whose switching strategy is based on sinusoidal pulse width modulation (SPWM. The model has been simulated in the Matlab/Simulink environment. The results of the simulation runs under steady state and dynamic load perturbation provide excellent voltage and current waveforms that support the justification of the proposed model.

  17. Extension of the Accurate Voltage-Sag Fault Location Method in Electrical Power Distribution Systems

    Directory of Open Access Journals (Sweden)

    Youssef Menchafou

    2016-03-01

    Full Text Available Accurate Fault location in an Electric Power Distribution System (EPDS is important in maintaining system reliability. Several methods have been proposed in the past. However, the performances of these methods either show to be inefficient or are a function of the fault type (Fault Classification, because they require the use of an appropriate algorithm for each fault type. In contrast to traditional approaches, an accurate impedance-based Fault Location (FL method is presented in this paper. It is based on the voltage-sag calculation between two measurement points chosen carefully from the available strategic measurement points of the line, network topology and current measurements at substation. The effectiveness and the accuracy of the proposed technique are demonstrated for different fault types using a radial power flow system. The test results are achieved from the numerical simulation using the data of a distribution line recognized in the literature.

  18. Control of Doubly-Fed Induction Generator to Ride-Through Recurring Grid Faults

    DEFF Research Database (Denmark)

    Chen, Wenjie; Xu, Dehong; Zhu, Nan

    2016-01-01

    The wind turbine system (WTS) is required to ride-through recurring grid faults by the new grid codes. Under single grid faults, the fault ride-through (FRT) strategy with rotor-side crowbar is normally used for the doubly-fed induction generator (DFIG) WTS. However, under recurring faults, larger...... system will be influenced. In this paper, an FRT strategy for the DFIG WTS to ride-through recurring symmetrical grid faults is investigated. An improved control strategy is introduced and it is applied during the voltage recovery of the grid faults. The decay of the stator natural flux can...... transient current and voltage may be produced, and the DFIG may fail to ride-through the second fault even with the rotor-side crowbar. The crowbar can be active again during the voltage recovery, but large electromagnetic torque (EM-torque) fluctuations will be introduced. The reliability of the mechanical...

  19. DG Allocation Based on Reliability, Losses and Voltage Sag Considerations: an expert system approach

    Directory of Open Access Journals (Sweden)

    Sahar Abdel Moneim Moussa

    2017-03-01

    Full Text Available Expert System (ES as a branch of Artificial Intelligence (AI methodology can potentially help in solving complicated power system problems. This may be more appropriate methodology than conventional optimization techniques when contradiction between objectives appears in reaching the optimum solution. When this contradiction is the hindrance in reaching the required system operation through the application of traditional methods ES can give a hand in such case. In this paper, the  knowledge- based ES technique is proposed to reach near-optimum solution which is further directed to the optimum solution through particle swarm optimization (PSO technique. This idea is known as Hybrid-Expert-System (HES. The proposed idea is used in getting the optimum allocation of a number of distributed generation (DG units on Distribution System (DS busbars taking into consideration three issues; reliability, voltage sag, and line losses. Optimality is assessed on the economic basis by calculating money benefits (or losses resulting from DG addition considering the three aforementioned issues. The effectiveness of the proposed technique is ascertained through example.

  20. The impacts of voltage sags in industrial electric systems; Os impactos dos afundamentos de tensao em sistemas eletricos industriais

    Energy Technology Data Exchange (ETDEWEB)

    Maia, Reinaldo Moreira [Moinhos Vera Cruz, Santa Luzia, MG (Brazil); Silva, Selenio Rocha [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil)

    2010-10-15

    The sensitiveness increasing of industrial equipment related to the perturbation of electric grid, resulting in losses to the productive chain, turns the energy quality in the subject more discussed by the electrical community. In this study case on the problems caused by voltage sags to equipment of an industrial plant from the food sector, it is presented the identification process and the adopted solutions. (author)

  1. Analysis of voltage sag compensation in distribution systems using a multilevel DSTATCOM in ATP/EMTP

    Directory of Open Access Journals (Sweden)

    Herbert Enrique Rojas-Cubides

    2015-01-01

    Full Text Available Los hundimientos de tensión (sags son perturbaciones de calida d de potencia comunes en los sistemas eléctricos. Estos pueden causar daños en equipos sensibles y la interrupción de procesos. El co mpensador estático de distribución (DSTATCOM es un dispositivo que puede compensar sags inyectando potencia reactiva al sistema. E ste artículo muestra la influencia que tiene la conexión de un DSTATCOM de 12-pulsos sobre los sags que se presentan en el sistema de d istribución IEEE-13 modificado. El análisis se realiza mediante la generación aleatoria de perturbaciones usan do una rutina de MATLAB para id entificar los nodos críticos del sistema de prueba. Además, se describe el modelo del DSTATCOM usando lo s elementos disponibles en el s oftware ATP/EMTP. Las simulaciones muestran que cuando el DSTATCOM se conecta al nodo afectado es posible mitigar el sag completamente. Finalmente, se considera la relación entre la po tencia reactiva inyectada por el DSTATCOM, el tipo de sag y la ubicaci ón del nodo afectado.

  2. Optimal Allocation of Distributed Generation Minimizing Loss and Voltage Sag Problem-Using Genetic Algorithm

    Science.gov (United States)

    Biswas, S.; Goswami, S. K.

    2010-10-01

    In the present paper an attempt has been made to place the distributed generation at an optimal location so as to improve the technical as well as economical performance. Among technical issues the sag performance and the loss have been considered. Genetic algorithm method has been used as the optimization technique in this problem. For sag analysis the impact of 3-phase symmetrical short circuit faults is considered. Total load disturbed during the faults is considered as an indicator of sag performance. The solution algorithm is demonstrated on a 34 bus radial distribution system with some lateral branches. For simplicity only one DG of predefined capacity is considered. MATLAB has been used as the programming environment.

  3. The account of sagging of wires at definition of specific potential factors of air High-Voltage Power Transmission Lines

    Directory of Open Access Journals (Sweden)

    Suslov V.M.

    2005-12-01

    Full Text Available The opportunity approached is shown, but more exact as it is usually accepted, the account of sagging of wires at definition of specific potential factors air High-Voltage Power Transmission Lines. The technique of reception of analytical expressions is resulted. For an opportunity of comparison traditional expressions for specific potential factors are resulted also. Communication of the offered and traditional analytical expressions is shown. Offered analytical expressions are not difficult for programming on a personal computer of any class and besides they allow to make an estimation of an error of traditional expressions by means of parallel definition of specific potential factors by both ways.

  4. Electromagnetic validation of fault-ride through capabilities of wind turbines

    DEFF Research Database (Denmark)

    Arana Aristi, Iván; Garcia-Valle, Rodrigo; Sharma, Ranjan

    2010-01-01

    Scope of the present project is the development and validation of electro-magnetic transient model of fixed-speed wind turbines. The research work is focused on the development of a fixed-speed wind turbine model with fault-ride through capabilities during transient over-voltages. The model...

  5. Fault Ride-Through Capability Enhancement of VSC HVDC connected Offshore Wind Power Plants

    DEFF Research Database (Denmark)

    Sharma, Ranjan; Wu, Qiuwei; Cha, Seung-Tae

    2015-01-01

    This paper presents a feed forward direct current (DC) voltage control based fault ride-through (FRT) scheme for voltage source converter (VSC) high voltage DC (HVDC) connected offshore wind power plants (WPPs) in order to achieve active control of the WPP collector network AC voltage magnitude......, and to improve the FRT capability. During steady state operation, an open loop AC voltage control is implemented at the WPP side VSC of the HVDC system such that any possible control interactions between the WPP side VSC and the wind turbine VSC are minimized. Whereas during any grid faults, a dynamic AC voltage...

  6. Impact of distributed generation in the probability density of voltage sags; Impacto da geracao distribuida na densidade de probabilidade de afundamentos de tensao

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, Alessandro Candido Lopes [CELG - Companhia Energetica de Goias, Goiania, GO (Brazil). Generation and Transmission. System' s Operation Center], E-mail: alessandro.clr@celg.com.br; Batista, Adalberto Jose [Universidade Federal de Goias (UFG), Goiania, GO (Brazil)], E-mail: batista@eee.ufg.br; Leborgne, Roberto Chouhy [Universidade Federal do Rio Grande do Sul (UFRS), Porto Alegre, RS (Brazil)], E-mail: rcl@ece.ufrgs.br; Emiliano, Pedro Henrique Mota, E-mail: ph@phph.com.br

    2009-07-01

    This article presents the impact of distributed generation in studies of voltage sags caused by faults in the electrical system. We simulated short-circuit-to-ground in 62 lines of 230, 138, 69 and 13.8 kV that are part of the electrical system of the city of Goiania, of Goias state . For each fault position was monitored the bus voltage of 380 V in an industrial consumer sensitive to such sags. Were inserted different levels of GD near the consumer. The simulations of a short circuit, with the monitoring bar 380 V, were performed again. A study using stochastic simulation Monte Carlo (SMC) was performed to obtain, at each level of GD, the probability curves and sags of the probability density and its voltage class. With these curves were obtained the average number of sags according to each class, that the consumer bar may be submitted annually. The simulations were performed using the Program Analysis of Simultaneous Faults - ANAFAS. In order to overcome the intrinsic limitations of the methods of simulation of this program and allow data entry via windows, a computational tool was developed in Java language. Data processing was done using the MATLAB software.

  7. Voltage sags and transient detection and classification using half/one-cycle windowing techniques based on continuous s-transform with neural network

    Science.gov (United States)

    Daud, Kamarulazhar; Abidin, Ahmad Farid; Ismail, Ahmad Puad

    2017-08-01

    This paper was conducted to detect and classify the different power quality disturbance (PQD) using Half and One-Cycle Windowing Technique (WT) based on Continuous S-Transform (CST) and Neural Network (NN). The system using 14 bus bars based on IEEE standard had been designing using MATLAB©/Simulink to provide PQD data. The datum of PQD is analyzed by using WT based on CST to extract features and it characteristics. Besides, the study focused an important issue concerning the identification of PQD selection and detection, the feature and characteristics of two types of signals such as voltage sag and transient signal are obtained. After the feature extraction, the classified process had been done using NN to show the percentage of classification PQD either voltage sags or transients. The analysis show which selection of cycle for windowing technique can provide the smooth detection of PQD and the suitable characteristic to provide the highest percentage of classification of PQD.

  8. Improving Fault Ride-Through Capability of Variable Speed Wind Turbines in Distribution Networks

    DEFF Research Database (Denmark)

    Mokryani, Geev; Siano, P.; Piccolo, Antonio

    2013-01-01

    In this paper, a fuzzy controller for improving the fault ride-through (FRT) capability of variable speed wind turbines (WTs) equipped with a doubly fed induction generator (DFIG) is presented. DFIGs can be used as reactive power sources to control the voltage at the point of common coupling (PCC...... on a real 37-bus weak distribution system confirmed that the proposed controller can enhance the FRT capability....

  9. A Simple Sag Generator Using SSRs

    DEFF Research Database (Denmark)

    Senturk, Osman Selcuk; Hava, Ahmet M.

    2012-01-01

    Power line voltage sags are among the most frequent and costly power quality problems. Most equipment must be designed such that they can tolerate voltage sags (within limits defined according to some standards). Furthermore, some equipment must continue proper operation even under extreme sag...... conditions (critical loads) and this property often may not be accommodated inside the device itself and sag compensating power conditioners have been developed for such purposes. While in practice voltage sags are not wanted, generating sags becomes necessary for the purpose of experimentally verifying...... SSR (solid state relay, a semiconductor power module of triac characteristics) and variable transformer (variac) based sag generator is built for three-phase 10kVA ratings and balanced/imbalanced voltage sags are demonstrated in the laboratory. The performance under resistive and inductive loads...

  10. A Simple Sag Generator Using SSRs

    DEFF Research Database (Denmark)

    Senturk, Osman Selcuk; Hava, Ahmet M.

    2010-01-01

    Power line voltage sags are among the most frequent and costly power quality problems. Most equipment must be designed such that they can tolerate voltage sags (within limits defined according to some standards). Furthermore, some equipment must continue proper operation even under extreme sag...... conditions (critical loads) and this property often may not be accommodated inside the device itself and sag compensating power conditioners have been developed for such purposes. While in practice voltage sags are not wanted, generating sags becomes necessary for the purpose of experimentally verifying...... SSR (solid state relay, a semiconductor power module of triac characteristics) and variable transformer (variac) based sag generator is built for three-phase 10kVA ratings and balanced/imbalanced voltage sags are demonstrated in the laboratory. The performance under resistive and inductive loads...

  11. Fault ride-through and grid support of permanent magnet synchronous generator-based wind farms with HVAC and VSC-HVDC transmission systems

    DEFF Research Database (Denmark)

    Liu, Hongzhi; Chen, Zhe

    2012-01-01

    This paper describes fault ride-through and grid support of offshore wind farms based on permanent magnet synchronous generator (PMSG) wind turbines connected to the onshore AC network through two alternative transmission systems: high voltage AC (HVAC) or high voltage DC (HVDC) based on voltage...

  12. Assessment of duration of the drive operation in the mode of kinetic energy recovery under power supply voltage sags in electrical grids of mechanical engineering enterprises

    Science.gov (United States)

    Shonin, O. B.; Novozhilov, N. G.

    2017-02-01

    Voltage sags in electric grids of mechanical engineering enterprises may lead to disconnection of important power consumers with variable frequency drives from the power grid and further interruption of the production process. The paper considers a sensorless V/f control system of еру induction motor drive under normal conditions and under voltage sags on the basis of a computer model of the drive and derivation of a formula for assessment of possible duration of the drive operation in the mode of controlled recovery of kinetic energy accumulated in rotating mass of the drive. Results of simulations have been used to validate results of calculations of the rotor velocity deceleration made in a closed form obtained from the equation reflecting the balance of torques. It is shown that results of calculations practically coincide with results of simulations in the range up to 5% of the velocity initial value. The proposed formula may be useful for estimation of the duration of the drive operation in the mode of recovery of kinetic energy depending on parameters of the motor and driven mechanisms.

  13. Power Hardware In The Loop Validation of Fault Ride Through of VSC HVDC Connected Offshore Wind Power Plants

    DEFF Research Database (Denmark)

    Sharma, Ranjan; Wu, Qiuwei; Cha, Seung-Tae

    2014-01-01

    This paper presents the power hardware in the loop (PHIL) validation of a feed forward DC voltage control scheme for the fault ride through (FTR) of voltage source converter (VSC) high voltage DC (HVDC) connected offshore wind power plants (WPPs). In the proposed FRT scheme, the WPP collector...... network AC voltage is actively controlled by considering both the DC voltage error and the AC current from the WPP AC collector system which ensures fast and robust FRT of the VSC HVDC connected offshore WPPs. The PHIL tests were carried out in order to verify the efficacy of the proposed feed forward DC...

  14. A Fuzzy Logic Controller to Increase Fault Ride-Through Capability of Variable Speed Wind Turbines

    Directory of Open Access Journals (Sweden)

    Geev Mokryani

    2012-01-01

    Full Text Available A fuzzy controller for improving Fault Ride-Through (FRT capability of Variable Speed Wind Turbines (WTs equipped with Doubly Fed Induction Generator (DFIG is presented. The controller is designed in order to compensate the voltage at the Point of Common Coupling (PCC by regulating the reactive and active power generated by WTs. The performances of the controller are evaluated in some case studies considering a different number of wind farms in different locations. Simulations, carried out on a real 37-bus Italian weak distribution system, confirmed that the proposed controller can enhance the FRT capability in many cases.

  15. Advanced fault ride-through control of DFIG based wind turbines including grid connection via VSC-HVDC

    Energy Technology Data Exchange (ETDEWEB)

    Feltes, Christian

    2012-07-01

    With the growing renewable energy share in the power generation mix it becomes inevitable that also these new generation technologies participate on the provision of grid services to guarantee stable operation of the grid, especially when one considers the decreasing number of conventional power plants in operation as a result of the expansion of wind based generation plants. These so-called ancillary services include frequency / active power control, voltage / reactive power control and fault ride-through (FRT) with fast voltage control and are stipulated in modern grid codes. In the context of this thesis advanced control algorithms have been developed for wind turbines based on doubly-fed induction generator (DFIG) to allow safe FRT during symmetrical and unsymmetrical faults. This covers the control for conventional AC grid connection as well as for the connection through voltage source converter (VSC) based high voltage direct current transmission (HVDC). Currently, the DFIG is the most used generator technology in modem wind turbines, since it combines a relatively simple slip-ring induction machine with a frequency converter rated to only approx. 30% of the total power. This makes the DFIG a cost-effective concept, which offers a variable speed range and a high degree of flexibility in control. However, due to the direct coupling of the generator stator circuit to the grid, grid faults are a special challenge for the frequency converter, its protection circuits and control algorithms. As base for the detailed evaluation of the impact of grid faults to the DFIG, this thesis contains the analytical derivation of the DFIG short circuit currents under consideration of frequency converter control. The DFIG concept presented in this thesis makes use of a DC chopper in the frequency converter, which allows safe FRT with grid voltage support through both converter sides. The developed control contains a new algorithm for a clear separation and control of positive

  16. Advanced Control Strategy of DFIG Wind Turbines for Power System Fault Ride Through

    DEFF Research Database (Denmark)

    Yang, Lihui; Xu, Zhao; Ostergaard, Jacob

    2012-01-01

    This paper presents an advanced control strategy for the rotor and grid side converters of the doubly fed induction generator (DFIG) based wind turbine (WT) to enhance the low-voltage ride-through (LVRT) capability according to the grid connection requirement. Within the new control strategy...... the instantaneous DC-link current of the rotor side converter in order to smooth the DC-link voltage fluctuations during the grid fault. A major difference from other methods is that the proposed control strategy can absorb the additional kinetic energy during the fault conditions, and significantly reduce...... the oscillations in the stator and rotor currents and the DC bus voltage. The effectiveness of the proposed control strategy has been demonstrated through various simulation cases. Compared with conventional crowbar protection, the proposed control method can not only improve the LVRT capability of the DFIG WT...

  17. A Current Limiting Strategy to Improve Fault Ride-Through of Inverter Interfaced Autonomous Microgrids

    DEFF Research Database (Denmark)

    Sadeghkhani, Iman; Esmail Hamedani Golshan, Mohamad; Guerrero, Josep M.

    2017-01-01

    With high penetration of distributed energy resources (DER), fault management strategy is of great importance for the distribution network operation. The objective of this paper is to propose a current and voltage limiting strategy to enhance fault ride-through (FRT) capability of inverter......-based islanded microgrids (MGs) in which the effects of inverter control system and inverter topology (four/three-wire) are considered. A threephase voltage-sourced inverter (VSI) with multi-loop control system implemented in synchronous, stationary, and natural reference frames is employed in this study...... for both four- and three-wire configurations. The proposed strategy provides high voltage and current quality during overcurrent conditions, which is necessary for sensitive loads. Several time-domain simulation studies are conducted to investigate the FRT capability of the proposed strategy against both...

  18. Z-Source Inverter Based Power Quality Compensator with Enhanced Ride-Through Capability

    DEFF Research Database (Denmark)

    Gajanayake, C.J.; Vilathgamuwa, D.M.; Loh, P.C.

    2007-01-01

    a Zsource inverter based power quality compensator and a control structure that supplies high quality voltage to the connected sensitive load in the presence of other non linear loads. The proposed topology consists of combination of shunt and series inverters connected to a common Z-source impedance...... network. The shunt inverter is controlled to maintain a quality voltage waveform at the load bus. Whereas the series inverter enhances the ride-through capability during grid faults, protects the shunt inverter by limiting the current and also controls the power delivered to the grid. The performance......Distributed generation has been gaining acceptance over the years and it has the potential to provide reliable power to sensitive loads. However, distributed networks are prone to unbalanced faults conditions. This makes single inverter DG systems unsuitable as UPS systems. This paper proposes...

  19. An adaptive Phase-Locked Loop algorithm for faster fault ride through performance of interconnected renewable energy sources

    DEFF Research Database (Denmark)

    Hadjidemetriou, Lenos; Kyriakides, Elias; Blaabjerg, Frede

    2013-01-01

    Interconnected renewable energy sources require fast and accurate fault ride through operation in order to support the power grid when faults occur. This paper proposes an adaptive Phase-Locked Loop (adaptive dαβPLL) algorithm, which can be used for a faster and more accurate response of the grid...... side converter control of a renewable energy source, especially under fault ride through operation. The adaptive dαβPLL is based on modifying the control parameters of the dαβPLL according to the type and voltage characteristic of the grid fault with the purpose of accelerating the performance...... results. Furthermore, the benefits of using the proposed adaptive PLL on the control of the GSC of RES are also demonstrated in this paper....

  20. Using forecast information for storm ride-through control

    DEFF Research Database (Denmark)

    Barahona Garzón, Braulio; Trombe, Pierre-Julien; Vincent, Claire Louise

    2013-01-01

    Using probabilistic forecast information in control algorithms can improve the performance of wind farms during periods of extreme winds. This work presents a wind farm supervisor control concept that uses probabilistic forecast information to ride-through a storm with softer ramps of power. Wind...... speed forecasts are generated with a statistical approach (i.e. time series models). The supervisor control is based on a set of logical rules that consider point forecasts and predictive densities to ramp-down the power of the wind farm before the storm hits. The potential of this supervisor control...... information, and particularly weather radar images....

  1. A grid side converter current controller for accurate current injection under normal and fault ride through operation

    DEFF Research Database (Denmark)

    Hadjidemetriou, Lenos; Kyriakides, Elias; Blaabjerg, Frede

    2013-01-01

    requirements. In addition, the renewable energy systems require fault ride through capability in order to support the power grid under balanced or unbalanced low voltage grid faults. Therefore, the development of advanced current controller techniques is essential for the grid side power electronic converters...... controller is designed using multiple synchronous reference frames and can inject full positive or full negative sequence balanced sinusoidal currents under abnormal grid conditions. The accurate performance with robustness against unbalanced and harmonic distorted grid voltage indicates that the proposed...

  2. Active damping control of DFIG wind turbines during fault ride through

    OpenAIRE

    Xu, H.; Chen, L; Wenske, J.

    2013-01-01

    Grid voltage sag causes typical transients in the generator electromagnetic torque, which result in significant stress on the wind turbine drive-train. In this paper, a combination of different simulation packages, namely FAST (Fatigue, Aerodynamics, Structure, Turbulence) and Simulink, is used to model the mechanical and electrical aspects of a 5-MW doubly-fed induction generator (DFIG) based wind turbine respectively. To reduce the mechanical loads induced by grid faults, a linear-quadratic...

  3. Novel scheme for enhancement of fault ride-through capability of doubly fed induction generator based wind farms

    Energy Technology Data Exchange (ETDEWEB)

    Vinothkumar, K. [Department of Electrical and Electronics Engineering, National Institute of Technology, Tiruchirappalli, Tamilnadu 620015 (India); Selvan, M.P., E-mail: selvanmp@nitt.ed [Department of Electrical and Electronics Engineering, National Institute of Technology, Tiruchirappalli, Tamilnadu 620015 (India)

    2011-07-15

    Research highlights: {yields} Proposed Fault ride-through (FRT) scheme for DFIG is aimed at energy conservation. {yields} The input mechanical energy is stored during fault and utilized at fault clearance. {yields} Enhanced Rotor speed stability of DFIG. {yields} Reduced Reactive power requirement and rapid voltage recovery at fault clearance. {yields} Improved post fault performance of DFIG at fault clearance. -- Abstract: Enhancement of fault ride-through (FRT) capability and subsequent improvement of rotor speed stability of wind farms equipped with doubly fed induction generator (DFIG) is the objective of this paper. The objective is achieved by employing a novel FRT scheme with suitable control strategy. The proposed FRT scheme, which is connected between the rotor circuit and dc link capacitor in parallel with Rotor Side Converter, consists of an uncontrolled rectifier, two sets of IGBT switches, a diode and an inductor. In this scheme, the input mechanical energy of the wind turbine during grid fault is stored and utilized at the moment of fault clearance, instead of being dissipated in the resistors of the crowbar circuit as in the existing FRT schemes. Consequently, torque balance between the electrical and mechanical quantities is achieved and hence the rotor speed deviation and electromagnetic torque fluctuations are reduced. This results in reduced reactive power requirement and rapid reestablishment of terminal voltage on fault clearance. Furthermore, the stored electromagnetic energy in the inductor is transferred into the dc link capacitor on fault clearance and hence the grid side converter is relieved from charging the dc link capacitor, which is very crucial at this moment, and this converter can be utilized to its full capacity for rapid restoration of terminal voltage and normal operation of DFIG. Extensive simulation study carried out employing PSCAD/EMTDC software vividly demonstrates the potential capabilities of the proposed scheme in

  4. Rotor Voltage Dynamics in the Doubly Fed Induction Generator During Grid Faults

    DEFF Research Database (Denmark)

    Lima, Francisco K. A.; Luna, Alvaro; Rodriguez, Pedro

    2010-01-01

    the system to control the initial overcurrents that appear in the generator during voltage sags, which can damage the RSC, without tripping it. As a difference with classical solutions, based on the installation of crowbar circuits, this operation mode permits to keep the inverter connected to the generator......This paper presents a new control strategy for the rotor-side converter (RSC) of wind turbines (WTs) based on doubly fed induction generators (DFIG) that intends to improve its low-voltage ride through capability. The main objective of this work is to design an algorithm that would enable......, something that would permit the injection of power to the grid during the fault, as the new grid codes demand. A theoretical study of the dynamical behavior of the rotor voltage is also developed, in order to show that the voltage at the rotor terminals required for the control strategy implementation...

  5. Assessment of control strategies for fault ride through of SCIG-based wind energy conversion systems

    Directory of Open Access Journals (Sweden)

    Manaullah

    2016-01-01

    Full Text Available With increasing penetration of wind energy into the power grid, researchers have started focusing more on control and coordination of wind energy conversion systems (WECS with the other components at system level, especially during fault. It is important to implement a suitable fault ride through control strategy to avoid tripping of the generators when the power system is subjected to voltage dips normally below 90% of nominal voltage. The dips below 90% may lead to a significant loss of generation and frequency collapse, followed by a blackout. This article implements and assesses the methodologies to deal with such situations for squirrel cage induction generator-based wind energy conversion systems employing fully rated power electronic converters. Three distinct control techniques—namely, balanced positive sequence control, positive negative sequence control, and dual current control—have been simulated and applied to grid side converter of SCIG-based WECS. The performance of all the three control strategies has been compared and presented in this work. During this study, the system is subjected to the most common unsymmetrical line to ground (LG fault and most severe symmetrical LLL fault on grid for the purpose of anaysis.

  6. Análisis multirresolución del motor trifásico de inducción sometido a huecos de tensión Triphasic induction motor multiresolution analysis on voltage sags

    Directory of Open Access Journals (Sweden)

    M.G Macri

    2012-04-01

    Full Text Available Este documento presenta los resultados del estudio realizado de la descomposición wavelet multinivel 1D de las señales perturbadas del par electromagnético y de la velocidad del eje del motor trifásico de inducción, cuando este es sometido a diferentes tipologías de huecos de tensión según la caracterización ABC, Bollen (2000. Los huecos de tensión trifásicos (3 variables son analizados indirectamente en el efecto producido en una variable perturbada (el par electromagnético o la velocidad del eje que contiene indirectamente información del tipo de hueco de tensión trifásico producido en el estator. El estudio analiza el efecto de los siete diferentes tipos de huecos de tensión, considerando también la influencia de la duración y tensión retenida. Para cada caso se obtiene un vector cuyos elementos son los niveles de energía wavelet en los distintos niveles de descomposición de la variable analizada, mostrando que la forma en que se distribuye la energía de la señal 1D en los distintos niveles de descomposición establece una firma única para cada caso. Esta forma de descripción de los huecos de tensión producidos en el estator, basada en la descomposición multinivel de una variable perturbada, reduce la cantidad de variables a analizar y permite posteriormente la clasificación de las perturbaciones empleando técnicas de inteligencia artificial; es ventajosa pues el almacenamiento de los vectores de niveles de energía de aproximación en las bases de datos emplea menor cantidad de espacio que la necesaria para una señal temporal, y empleando una DWT reversible es posible, además, reconstruir la variable de estado temporal.This document presents the study results of the wavelet 1D multi-level decomposition of perturbed electromagnetic torque and shaft speed signals, of the three-phase induction motor, when it is subjected to different types of voltage sags, as characterization ABC, Bollen (2000. The three

  7. Flexible fault ride through of DFIG wind turbines with DC-chopper solution

    Energy Technology Data Exchange (ETDEWEB)

    Wessels, Christian; Laubrock, Malte; Bellgardt, Uwe [Nordex Energy GmbH, Hamburg (Germany). System Dept Grid and Grid Integration; Genius, Andreas [Woodward Kempen GmbH, Kempen (Germany). Wind Power Systems

    2012-07-01

    Grid code requirements are becoming increasingly challenging due to the growing integration of decentralized power generators like renewable energy devices. One of the most challenging grid code requirements is the fault ride through (FRT) of wind turbines. Internationally varying and quickly revised grid code requirements are making it necessary for wind turbine manufacturers to apply competitive hardware and flexible software structures to respond quickly to renewed requirements or project specific changes. In this paper an industrially applied and field-tested hardware solution for the FRT of a DFIG wind turbine is presented. The method using a DC-chopper is making the utilization of the conventionally used rotor crowbar unnecessary. Thus, the consumption of reactive power during grid faults is avoided. Instead, a controlled current can be fed dynamically in order to support the grid voltage and to avoid mechanical stress on the drivetrain of the turbine. Using the presented technology, the application of a flexible FRT software structure is possible to fulfill the internationally varying FRT requirements, which is described here. Selected measurement results from long term FRT tests from a wind turbine manufacturer of a real 2.5 MW wind turbine during grid faults are presented and verify the results. (orig.)

  8. A Novel Wind Turbine Concept Based on an Electromagnetic Coupler and the Study of Its Fault Ride-through Capability

    Directory of Open Access Journals (Sweden)

    Rui You

    2013-11-01

    Full Text Available This paper presents a novel type of variable speed wind turbine with a new drive train different from the variable speed wind turbine commonly used nowadays. In this concept, a synchronous generator is directly coupled with the grid, therefore, the wind turbine transient overload capability and grid voltage support capability can be significantly improved. An electromagnetic coupling speed regulating device (EMCD is used to connect the gearbox high speed shaft and synchronous generator rotor shaft, transmitting torque to the synchronous generator, while decoupling the gearbox side and the synchronous generator, so the synchronous generator torque oscillations during a grid fault are not transmitted to the gearbox. The EMCD is composed of an electromagnetic coupler and a one quadrant operation converter with reduced capability and low cost. A control strategy for the new wind turbine is proposed and a 2 MW wind turbine model is built to study the wind turbine fault ride-through capability. An integrated simulation environment based on the aeroelastic code HAWC2 and software Matlab/Simulink is used to study its fault ride-through capability and the impact on the structural loads during grid three phase and two phase short circuit faults.

  9. Passivity-Based Control of a Doubly Fed Induction Generator System under Unbalanced Grid Voltage Conditions

    Directory of Open Access Journals (Sweden)

    Jiawei Huang

    2017-08-01

    Full Text Available According to the theory of passivity-based control (PBC, this paper establishes a port-controlled Hamiltonian system with dissipation (PCHD model for a doubly fed induction generator (DFIG system under unbalanced grid voltage conditions and proposes a method of interconnection and damping assignment passivity-based control (IDA-PBC of the system under such conditions. By using this method, the rotor-side converter and grid-side converter can be controlled simultaneously in order to improve fault ride-through capability of the DFIG system. Simulation results indicate that this IDA-PBC strategy effectively suppresses fluctuations of output current and power in the DFIG system during unbalanced grid voltage sag/swell, enhances dynamic performance, and improves the robustness of the system.

  10. DVR(Dynamic Voltage Restorer)

    Indian Academy of Sciences (India)

    First page Back Continue Last page Graphics. DVR(Dynamic Voltage Restorer). Supply voltage Sag compensation. Supply voltage Swell Compensation. Balancing the Load voltage. Compensation of Supply Voltage Harmonics.

  11. Fault ride-through enhancement of fixed speed wind turbine using bridge-type fault current limiter

    Directory of Open Access Journals (Sweden)

    Mostafa I. Marei

    2016-05-01

    Full Text Available The interaction between wind energy turbines and the grid results in two main problems, increasing the short-circuit level and reducing the Fault Ride-Through (FRT capability during faults. The objective of this paper is to solve these problems, for fixed speed Wind Energy Systems (WECS, utilizing the bridge-type Fault Current Limiter (FCL with a discharging resistor. A simple cascaded control system is proposed for the FCL to regulate the terminal voltage of the generator and limit the current. The system is simulated on PSCAD/EMTDC software to evaluate the dynamic performance of the proposed WECS compensated by FCL. The simulation results show the potentials of the FCL as a simple and effective method for solving grid interconnection problems of WECS.

  12. Grid to Standalone Transition Motion-Sensorless Dual-Inverter Control of PMSG With Asymmetrical Grid Voltage Sags and Harmonics Filtering

    DEFF Research Database (Denmark)

    Fatu, M.; Blaabjerg, Frede; Boldea, I.

    2014-01-01

    -coupling decoupling and line-voltage feedforward disturbance compensation. Also, a D-module filter is used to robustly extract the line voltage positive sequence followed by a phase-locked-loop (PLL) based observer to estimate the positive-sequence angle for control, including the case of asymmetric voltages...

  13. Differential Evolution Based IDWNN Controller for Fault Ride-Through of Grid-Connected Doubly Fed Induction Wind Generators.

    Science.gov (United States)

    Manonmani, N; Subbiah, V; Sivakumar, L

    2015-01-01

    The key objective of wind turbine development is to ensure that output power is continuously increased. It is authenticated that wind turbines (WTs) supply the necessary reactive power to the grid at the time of fault and after fault to aid the flowing grid voltage. At this juncture, this paper introduces a novel heuristic based controller module employing differential evolution and neural network architecture to improve the low-voltage ride-through rate of grid-connected wind turbines, which are connected along with doubly fed induction generators (DFIGs). The traditional crowbar-based systems were basically applied to secure the rotor-side converter during the occurrence of grid faults. This traditional controller is found not to satisfy the desired requirement, since DFIG during the connection of crowbar acts like a squirrel cage module and absorbs the reactive power from the grid. This limitation is taken care of in this paper by introducing heuristic controllers that remove the usage of crowbar and ensure that wind turbines supply necessary reactive power to the grid during faults. The controller is designed in this paper to enhance the DFIG converter during the grid fault and this controller takes care of the ride-through fault without employing any other hardware modules. The paper introduces a double wavelet neural network controller which is appropriately tuned employing differential evolution. To validate the proposed controller module, a case study of wind farm with 1.5 MW wind turbines connected to a 25 kV distribution system exporting power to a 120 kV grid through a 30 km 25 kV feeder is carried out by simulation.

  14. Differential Evolution Based IDWNN Controller for Fault Ride-Through of Grid-Connected Doubly Fed Induction Wind Generators

    Directory of Open Access Journals (Sweden)

    N. Manonmani

    2015-01-01

    Full Text Available The key objective of wind turbine development is to ensure that output power is continuously increased. It is authenticated that wind turbines (WTs supply the necessary reactive power to the grid at the time of fault and after fault to aid the flowing grid voltage. At this juncture, this paper introduces a novel heuristic based controller module employing differential evolution and neural network architecture to improve the low-voltage ride-through rate of grid-connected wind turbines, which are connected along with doubly fed induction generators (DFIGs. The traditional crowbar-based systems were basically applied to secure the rotor-side converter during the occurrence of grid faults. This traditional controller is found not to satisfy the desired requirement, since DFIG during the connection of crowbar acts like a squirrel cage module and absorbs the reactive power from the grid. This limitation is taken care of in this paper by introducing heuristic controllers that remove the usage of crowbar and ensure that wind turbines supply necessary reactive power to the grid during faults. The controller is designed in this paper to enhance the DFIG converter during the grid fault and this controller takes care of the ride-through fault without employing any other hardware modules. The paper introduces a double wavelet neural network controller which is appropriately tuned employing differential evolution. To validate the proposed controller module, a case study of wind farm with 1.5 MW wind turbines connected to a 25 kV distribution system exporting power to a 120 kV grid through a 30 km 25 kV feeder is carried out by simulation.

  15. Differential Evolution Based IDWNN Controller for Fault Ride-Through of Grid-Connected Doubly Fed Induction Wind Generators

    Science.gov (United States)

    Manonmani, N.; Subbiah, V.; Sivakumar, L.

    2015-01-01

    The key objective of wind turbine development is to ensure that output power is continuously increased. It is authenticated that wind turbines (WTs) supply the necessary reactive power to the grid at the time of fault and after fault to aid the flowing grid voltage. At this juncture, this paper introduces a novel heuristic based controller module employing differential evolution and neural network architecture to improve the low-voltage ride-through rate of grid-connected wind turbines, which are connected along with doubly fed induction generators (DFIGs). The traditional crowbar-based systems were basically applied to secure the rotor-side converter during the occurrence of grid faults. This traditional controller is found not to satisfy the desired requirement, since DFIG during the connection of crowbar acts like a squirrel cage module and absorbs the reactive power from the grid. This limitation is taken care of in this paper by introducing heuristic controllers that remove the usage of crowbar and ensure that wind turbines supply necessary reactive power to the grid during faults. The controller is designed in this paper to enhance the DFIG converter during the grid fault and this controller takes care of the ride-through fault without employing any other hardware modules. The paper introduces a double wavelet neural network controller which is appropriately tuned employing differential evolution. To validate the proposed controller module, a case study of wind farm with 1.5 MW wind turbines connected to a 25 kV distribution system exporting power to a 120 kV grid through a 30 km 25 kV feeder is carried out by simulation. PMID:26516636

  16. Fault-Ride through Strategy for Permanent-Magnet Synchronous Generators in Variable-Speed Wind Turbines

    Directory of Open Access Journals (Sweden)

    Mohamed Abdelrahem

    2016-12-01

    Full Text Available Currently, the electric power production by wind energy conversion systems (WECSs has increased significantly. Consequently, wind turbine (WT generators are requested to fulfill the grid code (GC requirements stated by network operators. In case of grid faults/voltage dips, a mismatch between the generated active power from the wind generator and the active power delivered to the grid is produced. The conventional approach is using a braking chopper (BC in the DC-link to dissipate this active power. This paper proposes a fault-ride through (FRT strategy for variable-speed WECSs based on permanent magnet synchronous generators (PMSGs. The proposed strategy exploits the rotor inertia of the WECS (inertia of the WT and PMSG to store the surplus active power during the grid faults/voltage dips. Thus, no additional hardware components are requested. Furthermore, a direct model predictive control (DMPC scheme for the PMSG is proposed in order to enhance the dynamic behavior of the WECS. The behavior of the proposed FRT strategy is verified and compared with the conventional BC approach for all the operation conditions by simulation results. Finally, the simulation results confirm the feasibility of the proposed FRT strategy.

  17. Fault Characteristics of Full Power Inverted Source Considering Low-voltage Ride Through Control Strategy

    Science.gov (United States)

    Zhang, Chi; Zeng, Jie; Zhao, Wei; Zhong, Guobin; Xu, Qi; Luo, Pandian; Li, Weiren; Liu, Bohan

    2017-05-01

    New energy source is thriving in China. However, the fault characteristics of grids have been altered significantly with the penetration of new energy source increasing. In conventional researches, the fault features of wind farms were discussed briefly or simply overlooked. This paper began with the theoretical analysis of control system of full power inverted (FPI) sources and indicated that the response time of current control loop is 8.5 ms, while the steady state current of FPI source is controlled by reference values and set value of current limiter; the expressions of steady state current of FPI source were presented then. In addition, main factors affecting fault current, including different active power generation before fault, different fault locations and different fault types, were analyzed comprehensively and compared through simulation to gain a clear insight into the whole process of faults. The research is helpful to obtain a better understanding of new energy source.

  18. A Reactive Current Injection Technique for Renewable Energy Converters in Low Voltage Ride-Through Operations

    DEFF Research Database (Denmark)

    Chou, Shih-Feng; Lee, Chia-Tse; Cheng, Po-Tai

    2011-01-01

    Distributed energy resources have assumed an important role in meeting the energy demand of today's world, thanks to their dramatic growth in recent years. Their potential in reducing the green house gas emission also leads to great attentions and expectations. As DERs are integrated into the uti...

  19. Solid state transformer with low-voltage ride-through and current unbalance management capabilities

    OpenAIRE

    Alepuz Menéndez, Salvador; González, Francisco; Martín-Arnedo, Jacinto; Martínez Velasco, Juan Antonio

    2013-01-01

    The solid state transformer is an emerging technology which aims at replacing the conventional lowfrequency power transformer by means of a high-frequency transformer driven by a proper AC/AC power electronics conversion system, at both transformer sides. In comparison with the conventional power transformer, the solid state transformer provides extended and enhanced operating capabilities that can be achieved with an appropriate controller design for the power electronics converters. I...

  20. Zero-voltage ride-through capability of single-phase grid-connected photovoltaic systems

    DEFF Research Database (Denmark)

    Zhang, Zhen; Yang, Yongheng; Ma, Ruiqing

    2017-01-01

    Distributed renewable energy systems play an increasing role in today’s energy paradigm. Thus, intensive research activities have been centered on improving the performance of renewable energy systems, including photovoltaic (PV) systems, which should be of multiple-functionality. That is, the PV...

  1. Internal Balance during Low-Voltage-Ride-Through of the Modular Multilevel Converter STATCOM

    NARCIS (Netherlands)

    Tsolaridis, Georgios; Kontos, E.; Chaudhary, Sanjay K.; Bauer, P.; Teodorescu, Remus

    2017-01-01

    Grid faults are common in power systems and can have a severe impact on the operation of the converters in the system. In this paper, the operation of a Modular Multilevel Converter (MMC)-based Static Synchronous Compensators (STATCOM) is investigated during grid faults. The study focuses on the

  2. Low Voltage Ride-Through of Single-Phase Transformerless Photovoltaic Inverters

    OpenAIRE

    Yang, Yongheng; Blaabjerg, Frede; Wang, Huai

    2014-01-01

    Transformerless photovoltaic (PV) inverters are going to be more widely adopted in order to achieve high efficiency, as the penetration level of PV systems is continuously booming. However, problems may arise in highly PV-integrated distribution systems. For example, a sudden stoppage of all PV systems due to anti-islanding protection may contribute to grid disturbances. Thus, standards featuring with ancillary services for the next generation PV systems are under a revision in some countries...

  3. Low voltage ride-through of single-phase transformerless photovoltaic inverters

    OpenAIRE

    Yang, Yongheng; Blaabjerg, Frede; Wang, Huai

    2013-01-01

    Transformerless photovoltaic (PV) inverters are going to be more widely adopted in order to achieve high efficiency, as the penetration level of PV systems is continuously booming. However, problems may arise in highly PV-integrated distribution systems. For example, a sudden stoppage of all PV systems due to anti-islanding protection may trigger grid disturbances. Thus, standards featuring with ancillary services for the next generation PV systems are under a revision in some countries. The ...

  4. Study on Application of New Approach of Fault Current Limiters in Fault Ride through Capability Improvement of DFIG Based Wind Turbine

    DEFF Research Database (Denmark)

    Naderi, Seyed Behzad; Davari, Pooya; Zhou, Dao

    2018-01-01

    . The proposed FCL can insert a controllable resistance in fault current pass to not only restrict fault current level and compensate voltage sag in the stator but also consume pre-fault output active power of the DFIG regarding wind speed variation. Simulation results and analytics are presented to prove...

  5. Impact of fault ride-through requirements on fixed-speed wind turbine structural loads

    DEFF Research Database (Denmark)

    Hansen, Anca Daniela; Cutululis, Nicolaos Antonio; Markou, Helen

    2011-01-01

    simulation tools, which have expertise in different specialized wind turbines design areas. Two complimentary simulation tools are considered i.e. the detailed power system simulation tool PowerFactory from DIgSILENT and the advanced aeroelastic computer code HAWC2, in order to assess of the dynamic response...... by performing a rainflow and a statistical analysis for fatigue and ultimate structural loads, respectively. Two cases are compared i.e. one where the turbine is immediately disconnected from the grid when a grid fault occurs and one where the turbine is equipped with a fault ride-through controller...... faults. This article proposes a computer approach for the quantification of the wind turbines structural loads caused by the fault ride-through grid requirements. This approach, exemplified for the case of a 2MW active stall wind turbine, relies on the combination of knowledge from complimentary...

  6. High-Order Sliding Mode Control for DFIG-Based Wind Turbine Fault Ride-Through

    OpenAIRE

    Benbouzid, Mohamed; Beltran, Brice; Amirat, Yassine; Gang, Yao; Jingang, Han; Mangel, Hervé

    2013-01-01

    International audience; This paper deals with the Fault Ride-Through (FRT) capability assessment of a Doubly-Fed Induction Generator (DFIG)-based Wind Turbine (WT) using High-Order Sliding Mode (HOSM) control. Indeed, it has been recently suggested that sliding mode control is a solution of choice to the FRT problem. In this context, this paper proposes HOSM as an improved solution that handle the classical sliding mode chattering problem. Indeed, the main and attractive features of HOSMs are...

  7. Coordination between Fault-Ride-Through Capability and Overcurrent Protection of DFIG Generatorsfor Wind Farms

    OpenAIRE

    Bak-Jensen, Birgitte; Kawady, Tamer A.; Abdel-Rahman, Mansour H.

    2009-01-01

    Due to the increasing penetration of wind farms in power systems, stability issues arise strongly for power system operation. Doubly-Fed Induction Generators (DFIG) are charac-terized with some unique features during normal/abnormal op-erating conditions as compared with singly-fed ones. Fault ride-Through (FRT) mainly aims to delay a disconnecting of the DFIG units during grid faults for a possible time to restore the system stability if the fault is cleared within a permissible time. This s...

  8. A dynamic voltage restorer (DVR) with selective harmonic compensation at medium voltage level

    DEFF Research Database (Denmark)

    Newman, M.J.; Holmes, D.G.; Nielsen, J.G.

    2005-01-01

    Dynamic voltage restorers (DVRs) are now becoming more established in industry to reduce the impact of voltage sags to sensitive loads. However, DVRs spend most of their time in standby mode, since voltage sags occur very infrequently, and hence their utilization is low. In principle, it would...... voltage harmonic compensation capabilities with minimal effect on the sag compensation performance of the basic DVR. The proposed controller has been experimentally verified on a medium-voltage (10 kV) three-phase DVR prototype under a range of conditions, including distorted supply voltages, nonlinear...... loads, and operation during distorted voltage sags....

  9. Examination of fault ride-through methods for off-shore wind farms connected to the grid through VSC-based HVDC transmission

    Energy Technology Data Exchange (ETDEWEB)

    Karaagac, U.; Mahseredjian, J.; Saad, H. [Ecole Polytechnique de Montreal, QC (Canada); Jensen, S.; Cai, L. [REpower Systems AG, Hamburg (Germany)

    2012-07-01

    The fault ride-through (FRT) performance of offshore wind farms (OWFs) is a challenging task when the OWF is connected to the onshore ac grid through a voltage source converter (VSC) based HVDC transmission system. The injected power from the OWF cannot be reduced by the offshore VSC during onshore ac faults and this causes a fast increase in the dc network voltage. Without any special FRT method, the dc network voltage may increase up to intolerable levels and cause operation of dc overvoltage protection. This paper compares various FRT methods based on fast reduction of power generation in OWFs. In addition, this paper proposes an improved FRT method based on controlled voltage drop for output power reduction in OWFs. The proposed improvement reduces mechanical stress on the wind turbine (WT) drive train, and electrical stress on the insulated gate bipolar transistors (IGBTs) of the HVDC and doubly-fed induction generator (DFIG) converters. Practical onshore ac fault scenarios are simulated for an OWF composed of DFIG type WTs and connected to a practical ac grid through a point-to-point modular multilevel converter (MMC) based HVDC system. (orig.)

  10. Coordination between Fault-Ride-Through Capability and Overcurrent Protection of DFIG Generatorsfor Wind Farms

    DEFF Research Database (Denmark)

    Bak-Jensen, Birgitte; Kawady, Tamer A.; Abdel-Rahman, Mansour H.

    2009-01-01

    -Through (FRT) mainly aims to delay a disconnecting of the DFIG units during grid faults for a possible time to restore the system stability if the fault is cleared within a permissible time. This strategy may, however, affect the performance of related protective elements during fault periods. In this paper......, the Coor-dination between Fault Ride-Through Capability and Overcur-rent Protection of DFIG Wind Generators in MV Networks is in-vestigated. Simulation test cases using MATLAB-Simulink are implemented on a 345-MW wind farm in AL-Zaafarana, Egypt. The simulation results show the influence of FRT capability......Due to the increasing penetration of wind farms in power systems, stability issues arise strongly for power system operation. Doubly-Fed Induction Generators (DFIG) are charac-terized with some unique features during normal/abnormal op-erating conditions as compared with singly-fed ones. Fault ride...

  11. Wind Farm Stabilization by using DFIG with Current Controlled Voltage Source Converters Taking Grid Codes into Consideration

    Science.gov (United States)

    Okedu, Kenneth Eloghene; Muyeen, S. M.; Takahashi, Rion; Tamura, Junji

    Recent wind farm grid codes require wind generators to ride through voltage sags, which means that normal power production should be re-initiated once the nominal grid voltage is recovered. However, fixed speed wind turbine generator system using induction generator (IG) has the stability problem similar to the step-out phenomenon of a synchronous generator. On the other hand, doubly fed induction generator (DFIG) can control its real and reactive powers independently while being operated in variable speed mode. This paper proposes a new control strategy using DFIGs for stabilizing a wind farm composed of DFIGs and IGs, without incorporating additional FACTS devices. A new current controlled voltage source converter (CC-VSC) scheme is proposed to control the converters of DFIG and the performance is verified by comparing the results with those of voltage controlled voltage source converter (VC-VSC) scheme. Another salient feature of this study is to reduce the number of proportionate integral (PI) controllers used in the rotor side converter without degrading dynamic and transient performances. Moreover, DC-link protection scheme during grid fault can be omitted in the proposed scheme which reduces overall cost of the system. Extensive simulation analyses by using PSCAD/EMTDC are carried out to clarify the effectiveness of the proposed CC-VSC based control scheme of DFIGs.

  12. Elimination & Mitigation of Sag & Swell Using a New UPQC-S Methodology & Fuzzy Logic Controller

    OpenAIRE

    Kanaka Raju Kalla,; Suneelgoutham Karudumpa

    2014-01-01

    This paper presents the enhancement of voltage sags, harmonic distortion and low power factor using Unified Power Quality Conditioner (UPQC) with Fuzzy Logic Controller in distribution system, The series inverter of UPQC is controlled to perform simultaneous 1) voltage sag/swell compensation and 2) load reactive power sharing with the shunt inverter. Since the series inverter simultaneously delivers active and reactive powers, this concept is named as UPQC-S (S for complex pow...

  13. Implementation of Dynamic Voltage Restorer for Mitigation of Voltage Sag

    National Research Council Canada - National Science Library

    K.Vinod Kumar

    2013-01-01

    Power quality is one of major concerns in the present. It has become important, especially with the introduction of sophisticated devices, whose performance is very sensitive to the quality of power supply...

  14. Coordination between Fault-Ride-Through Capability and Over-current Protection of DFIG Generators for Wind Farms

    OpenAIRE

    Bak-Jensen, Birgitte; Kawady, T.A.; Abdel-Rahman, Mansour Hassan

    2010-01-01

    Fault Ride-Through (FRT) capabilities set up according to the grid codes may affect the performance of related protective elements during fault periods. Therefore, in this paper the coordination between the FRT capability and over-current protection of DFIG Wind Generators in MV networks is investigated. Simulation test cases using MATLAB-Simulink are implemented on a 365-MW wind farm in AL-Zaafarana, Egypt. The simulation results show the influence of the FRT capability on the protective rel...

  15. Performance Evaluation of Low/Zero Voltage Ride-Through Operations for Single-Stage Single-Phase Photovoltaic Inverters

    DEFF Research Database (Denmark)

    Zhang, Zhen; Yang, Yongheng; Blaabjerg, Frede

    2017-01-01

    to be continuously updated. In current active grid requirements/codes, PV systems should be more intelligent in the considerations of the grid stability, reliability and fault protection. In this paper, two control strategies (i.e., the single-phase PQ control and power phase-angle control) are evaluated for grid...

  16. Low voltage ride through peformance of a STATCOM based on modular multilevel cascade converters for offshore wind application

    DEFF Research Database (Denmark)

    Tanaka, Takaaki; Wang, Huai; Ma, Ke

    2017-01-01

    Static Synchronous Compensators (STATCOMs) are being applied for offshore wind power plants to satisfy the grid codes under both normal operation and grid fault conditions. This paper investigates the performances of Modular Multilevel Cascade Converters (MMCC) for the STATCOM application, with s...

  17. Thermal analysis of multilevel grid side converters for 10 MW wind turbines under Low Voltage Ride Through

    DEFF Research Database (Denmark)

    Ma, Ke; Blaabjerg, Frede; Liserre, Marco

    2011-01-01

    , and able to contribute to the grid recovery by injecting reactive current during grid faults. Consequently, the full-scale power converter solutions are becoming more and more popular to fulfill the growing challenges in the wind power application. Nevertheless, the loading of the power devices in full......-scale power converters, especially during grid faults may compromise the reliability performance and further increase the cost of the system. In this paper, three promising grid side multilevel converter topologies for the next generation 10 MW wind turbines are proposed and basically designed as case study......As the power level of a single wind turbine is continuously pushed up even to 7 MW, the wind power generation system are required to be more reliable, and able to withstand extreme grid disturbances. Moreover, it is becoming a need that the wind power generation system should be more active...

  18. Thermal Analysis of Multilevel Grid-side Converters for 10-MW Wind turbines under Low-Voltage Ride Through

    DEFF Research Database (Denmark)

    Ma, Ke; Blaabjerg, Frede; Liserre, Marco

    2013-01-01

    As the power level of a single wind turbine is continuously pushed up even to 7 MW, the wind power generation systems are required to be more reliable and able to withstand extreme grid disturbances. Moreover, it is becoming a need that the wind power generation system should be more active...... devices in full-scale power converters, particularly during grid faults, may compromise the reliability performance and further increase the cost of the system. In this paper, three promising grid-side multilevel converter topologies for the next-generation 10-MW wind turbines are proposed and basically...

  19. Fault Ride-Through Strategies for VSC-Connected Wind Parks

    NARCIS (Netherlands)

    Hendriks, R.L.; Völzke, R.; Kling, W.L.

    2009-01-01

    High-voltage direct-current transmission based on voltage-sourced converters (VSC-HVDC) is an economic connection technology for large remote wind parks. Wind power plants that are connected through a VSC-HVDC link are subjected to the same technical connection requirements as conventional

  20. Study of DFIG Wind Turbine Fault Ride-Through According to The Danish Grid Code

    DEFF Research Database (Denmark)

    Abulanwar, Elsayed; Chen, Zhe; Bak-Jensen, Birgitte

    2013-01-01

    This paper presents a new decentralized control strategy to enable a Doubly-fed Induction generator wind turbine, DFIG WT, to fulfill the Danish grid code requirements during different perturbations. A nonlinear controller is adopted for the grid side converter, GSC, to ensure decoupled control...... of the DC link voltage and the reactive power, and counteract the DC link voltage runaway. Moreover, the GSC is dedicated to inject more reactive power during voltage dips to satisfy the grid code reactive power support obligation. A conventional PI controller is devoted to control the rotor side converter....... The obtained results assure the capability of the proposed control strategy to satisfy the Danish grid code requirements....

  1. Fault ride-through enhancement using an enhanced field oriented control technique for converters of grid connected DFIG and STATCOM for different types of faults.

    Science.gov (United States)

    Ananth, D V N; Nagesh Kumar, G V

    2016-05-01

    With increase in electric power demand, transmission lines were forced to operate close to its full load and due to the drastic change in weather conditions, thermal limit is increasing and the system is operating with less security margin. To meet the increased power demand, a doubly fed induction generator (DFIG) based wind generation system is a better alternative. For improving power flow capability and increasing security STATCOM can be adopted. As per modern grid rules, DFIG needs to operate without losing synchronism called low voltage ride through (LVRT) during severe grid faults. Hence, an enhanced field oriented control technique (EFOC) was adopted in Rotor Side Converter of DFIG converter to improve power flow transfer and to improve dynamic and transient stability. A STATCOM is coordinated to the system for obtaining much better stability and enhanced operation during grid fault. For the EFOC technique, rotor flux reference changes its value from synchronous speed to zero during fault for injecting current at the rotor slip frequency. In this process DC-Offset component of flux is controlled, decomposition during symmetric and asymmetric faults. The offset decomposition of flux will be oscillatory in a conventional field oriented control, whereas in EFOC it was aimed to damp quickly. This paper mitigates voltage and limits surge currents to enhance the operation of DFIG during symmetrical and asymmetrical faults. The system performance with different types of faults like single line to ground, double line to ground and triple line to ground was applied and compared without and with a STATCOM occurring at the point of common coupling with fault resistance of a very small value at 0.001Ω. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

  2. Coordination between Fault-Ride-Through Capability and Over-current Protection of DFIG Generators for Wind Farms

    DEFF Research Database (Denmark)

    Bak-Jensen, Birgitte; Kawady, T.A.; Abdel-Rahman, Mansour Hassan

    2010-01-01

    Fault Ride-Through (FRT) capabilities set up according to the grid codes may affect the performance of related protective elements during fault periods. Therefore, in this paper the coordination between the FRT capability and over-current protection of DFIG Wind Generators in MV networks...... is investigated. Simulation test cases using MATLAB-Simulink are implemented on a 365-MW wind farm in AL-Zaafarana, Egypt. The simulation results show the influence of the FRT capability on the protective relaying coordination in wind farms, showing that the FRT may work in situations where is were expected...

  3. Sensorless Control of Late-Stage Offshore DFIG-WT with FSTP Converters by Using EKF to Ride through Hybrid Faults

    Directory of Open Access Journals (Sweden)

    Wei Li

    2017-11-01

    Full Text Available A hybrid fault scenario in a late-stage offshore doubly-fed induction generator (DFIG-based wind turbine (DFIG-WT with converter open-circuit fault and position sensor failure is investigated in this paper. An extended Kalman filter (EKF-based sensorless control strategy is utilized to eliminate the encoder. Based on the detailed analysis of the seventh-order dynamic state space model of DFIG, along with the input voltage signals and measured current signals, the EKF algorithm for DFIG is designed to estimate the rotor speed and position. In addition, the bridge arm open circuit in the back-to-back (BTB power converter of DFIG is taken as a commonly-encountered fault due to the fragility of semiconductor switches. Four-switch three-phase (FSTP topology-based fault-tolerant converters are employed for post-fault operation by considering the minimization of switching losses and reducing the circuit complexity. Moreover, a simplified space vector pulse width modulation (SVPWM technique is proposed to reduce the computational burden, and a voltage balancing scheme is put forward to increase the DC-bus voltage utilization rate. Simulation studies are carried out in MATLAB/Simulink2017a (MathWorks, Natick, MA, USA to demonstrate the validity of the proposed hybrid fault-tolerant strategy for DFIG-WT, with the wind speed fluctuation, measurement noises and grid voltage sag taken into consideration.

  4. En sag af principiel karakter

    DEFF Research Database (Denmark)

    Schaffalitzky de Muckadell, Caroline

    2015-01-01

    Denne artikel argumenterer for at der er brug for en mere systematisk tilgang til spørgsmålet om religionsdefinitoner. Udgangspunktet for artiklen er en sag hvor en fodboldfanklub fik afvist sin ansøgning om officiel godkendelse uden at afslaget henviste til egentlige kriterier for hvornår noget ...... til en definition på baggrund af denne metode. Dermed kan artiklen belyse en velkendt tidligere diskussion og en nyere tilgang og desuden foreslå hvordan afslaget til fodboldfanklubben kunne være begrundet tydeligere....

  5. Co-ordinated voltage control of DFIG wind turbines in uninterrupted operation during grid faults

    DEFF Research Database (Denmark)

    Hansen, Anca Daniela; Michalke, G.; Sørensen, Poul Ejnar

    2007-01-01

    is implemented in the power system simulation toolbox PowerFactory DIgSILENT. The DFIG wind farm ride-through capability and contribution to voltage control in the power system are assessed and discussed by means of simulations with the use of a transmission power system generic model developed and delivered......-side converter as long as it is not blocked by the protection system, otherwise the grid-side converter takes over the voltage control. Moreover, the article presents a DFIG wind farm model equipped with a grid fault protection system and the described co-ordinated voltage control. The whole DFIG wind farm model...... by the Danish Transmission System Operator Energinet.dk. The simulation results show how a DFIG wind farm equipped with voltage control can help a nearby active stall wind farm to ride through a grid fault, without implementation of any additional ride-through control strategy in the active stall wind farm....

  6. Modeling and Stress Analysis of Doubly-Fed Induction Generator during Grid Voltage Swell

    DEFF Research Database (Denmark)

    Zhou, Dao; Song, Yipeng; Blaabjerg, Frede

    2016-01-01

    the DFIG modeling and challenges when facing the symmetrical voltage swell. Then, the High Voltage Ride-Through (HVRT) capability of the DFIG can be calculated by using the demagnetizing current control, and the stator current, rotor current as well as the electromagnetic torque can be deduced during...... the transient voltage swell and its recovery. It is concluded that although both higher swell level and higher rotor speed cause higher rotor electromotive force, the doubly-fed induction generator can successfully ride through the grid fault due to the relatively small swell level required by the modern grid...

  7. A New Coordinated Voltage Control Scheme for Offshore AC Grid of HVDC Connected Offshore Wind Power Plants

    DEFF Research Database (Denmark)

    Sakamuri, Jayachandra N.; Cutululis, Nicolaos Antonio; Rather, Zakir Hussain

    2015-01-01

    This paper proposes a coordinated voltage control scheme (CVCS) which enhances the voltage ride through (VRT) capability of an offshore AC grid comprised of a cluster of offshore wind power plants (WPP) connected through AC cables to the offshore voltage source converter based high voltage DC (VS......V with active power balance (hence DC voltage) control assigned to the onshore converter, while frequency and AC voltage control at the offshore substation assigned to the offshore converter....

  8. Traffic Flow at Sags : Theory, Modeling and Control

    NARCIS (Netherlands)

    Goni-Ros, B.

    2016-01-01

    Sag vertical curves (sags) are roadway sections along which the gradient increases gradually in the direction of traffic. Empirical observations show that, on freeways, traffic congestion often occurs at sags; actually, in some countries (e.g., Japan), sags are one of the most common types of

  9. Compensation for gravitational sag of bent mirror

    Energy Technology Data Exchange (ETDEWEB)

    Mao, Chengwen; Jiang, Hui; He, Yan; Liang, Dongxu; Lan, Xuying; Yan, Shuai [Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, CAS, Shanghai 201800 (China); Shu, De-ming [Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439 (United States); Li, Aiguo, E-mail: aiguo.li@sinap.ac.cn [Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, CAS, Shanghai 201800 (China)

    2017-05-01

    The gravitational sag of aspheric bent mirrors with face-up or face-down geometry produces a nonnegligible optical error. As an effective compensation, width optimization is used to match the combined effects of the gravitational and bending moments. This method is described by analytical expressions and two calculation algorithms. The results of theoretical simulations and finite element analysis have proved that this method can reduce the slope error resulting from gravitational sag to the level of nano radians.

  10. Rotor Current Control of DFIG for Improving Fault Ride - Through Using a Novel Sliding Mode Control Approach

    Science.gov (United States)

    Cai, Guowei; Liu, Cheng; Yang, Deyou

    2013-11-01

    The doubly fed induction generators (DFIG) have been recognized as the dominant technology used in wind power generation systems with the rapid development of wind power. However, continuous operation of DFIG may cause a serious wind turbine generators tripping accident, due to destructive over-current in the rotor winding which is caused by the power system fault or inefficient fault ride-through (FRT) strategy. A new rotor current control scheme in the rotor-side converter (RSC) ispresented to enhance FRT capacities of grid-connected DFIG. Due to the strongly nonlinear nature of DFIG and insensitive to DFIG parameter's variations, a novel sliding mode controller was designed. The controller combines extended state observer (ESO) with sliding model variable structure control theory. The simulation is carried out to verify the effectiveness of the proposed control approach under various types of grid disturbances. It is shown that the proposed controller provides enhanced transient features than the classic proportional-integral control. The proposed control method can effectively reduce over-current in the RSC, and the transient pulse value of electromagnetic torque is too large under power grid fault.

  11. VOLTAGE COMPENSATION USING ARTIFICIAL NEURAL NETWORK

    African Journals Online (AJOL)

    A study of hourly voltage log taken over a period of six months from Rumuola Distribution network Port Harcourt, Rivers State indicates that power quality problems prevalent in the Network are undervoltage/voltage sags and overvoltage/voltage swells. This paper aims at addressing these power quality problems in the ...

  12. Characterization, identification and location of voltage sags: review of state of art Caracterización, identificación y localización de huecos de tensión: revisión del estado del arte

    Directory of Open Access Journals (Sweden)

    Jairo Blanco Solano

    2012-06-01

    Full Text Available This paper presents a review of the state of art of characterization, identification and location of voltage sags. The methods presented are the product of different analyzes on electromagnetic disturbance, specifically on voltage and current waveforms. Electrical circuits theory, electromagnetic transients and knowledge of the phenomenon are used to propose attributes and descriptors to characterize the disturbances according to some interest characteristic. A review of basic characterizations and methodologies that integrate complex classifiers and descriptor is performed. Emphasis is performed on characterization methods, together with attributes and descriptors, where the limitations and possible improvements are included. According at development level in these studies, new methodologies are needed to integrate characterization, diagnosis of causes, localization, assessment and information extraction modules. The methodologies are oriented towards a tool for automatic management of power systems disturbances.En este artículo se presenta una revisión del estado del arte de la caracterización, identificación y localización de los huecos de tensión. Los métodos presentados son el producto de diferentes análisis aplicados a la perturbación electromagnética, específicamente a las formas de onda de tensión y corriente, donde basándose en la teoría de circuitos eléctricos, transitorios electromagnéticos y el conocimiento del fenómeno se proponen atributos y descriptores que permiten caracterizar las perturbaciones de acuerdo a cierta característica de interés. Se hace una revisión tanto de caracterizaciones básicas como de metodologías que integran clasificadores y descriptores más complejos. Se hace énfasis en los métodos de caracterización, junto con sus atributos y descriptores, incluyendo sus limitantes y posibles mejoras. De acuerdo al nivel de desarrollo encontrado en estos estudios, resulta la necesidad de

  13. A detailed comparison of system topologies for dynamic voltage restorers

    DEFF Research Database (Denmark)

    Nielsen, J.G.; Blaabjerg, Frede

    2005-01-01

    In this paper, four different system topologies for dynamic voltage restorers (DVRs) are analyzed and tested, with particular focus on the methods used to acquire the necessary energy during a voltage sag. Comparisons are made between two topologies that can be realized with a minimum amount...... of energy storage, with energy taken from the grid during the voltage sag, and two topologies that take energy from stored energy devices during the voltage sag. Experimental tests using a 10-kVA DVR show that the no-energy storage concept is feasible, but an improved performance can be achieved for certain...... voltage sags using stored energy topologies. The results of this comparison rank the no-storage topology with a passive shunt converter on the load side first, followed by the stored energy topology with a constant dc-link voltage....

  14. Fault Ride through Capability Improvement of Wind Turbine Based DFIG Considering an Optimized Crowbar Along with STATCOM under Grid Fault Condition

    OpenAIRE

    Alireza Zohoori; Ahad Kazemi; Rouhollah Shafaie

    2013-01-01

    Grid disturbances, especially grid faults, have very unfavorable effect on the performance of wind turbine based Doubly Fed Induction Generator (DFIG). In this study active and reactive powers control of DFIG with STATCOM has been carried out to improve Fault Ride Through (FRT) capability of a wind turbine. In order to excel improvement of the DFIG behavior under grid fault disturbances, an optimized crowbar protection method is also considered together with STATCOM. The optimized protection ...

  15. Control and Testing of a Dynamic Voltage Restorer (DVR) at Medium Voltage Level

    DEFF Research Database (Denmark)

    Nielsen, John Godsk; Newman, Michael; Nielsen, Hans Ove

    2004-01-01

    The dynamic voltage restorer (DVR) has become popular as a cost effective solution for the protection of sensitive loads from voltage sags. Implementations of the DVR have been proposed at both a low voltage (LV) level, as well as a medium voltage (MV) level; and give an opportunity to protect high...... power sensitive loads from voltage sags. This paper reports practical test results obtained on a medium voltage (10 kV) level using a DVR at a Distribution test facility in Kyndby, Denmark. The DVR was designed to protect a 400-kVA load from a 0.5-p.u. maximum voltage sag. The reported DVR verifies...... duration voltage sags were created using a controllable LV breaker fed by a 630 kVA Distribution transformer placed upstream of the sensitive load. The fault currents in excess of 12 kA were designed and created to obtain the required voltage sags. It is concluded the DVR works well in all operating...

  16. Mains voltage profile in Dar es Salaam: A case study | Mvungi ...

    African Journals Online (AJOL)

    ... 40% and surges as high 17.4% above the normal value. The paper further proposes methods to address the problems at the consumer end. Keywords: Voltage instability, under-voltage, over-voltage, shedding, brownouts, voltage dips, voltage sags, voltage regulation. Journal of Agriculture, Science and Technology Vol.

  17. Grid Voltage Synchronization for Distributed Generation Systems under Grid Fault Conditions

    DEFF Research Database (Denmark)

    Luna, Alvaro; Rocabert, J.; Candela, I.

    2015-01-01

    The actual grid code requirements for the grid connection of distributed generation systems, mainly wind and PV systems, are becoming very demanding. The Transmission System Operators (TSOs) are especially concerned about the Low Voltage Ride Through requirements. Solutions based on the installat...

  18. SAG Foam Flooding in Carbonate Rocks

    NARCIS (Netherlands)

    Boeije, C.S.; Rossen, W.R.

    2017-01-01

    Foam is used in gas-injection EOR processes to reduce the mobility of gas, resulting in greater volumetric sweep. SAG (Surfactant Alternating Gas) is a preferred method of injection as it results in greater injectivity in the field, but designing a successful process

  19. (ann) based dynamic voltage restorer

    African Journals Online (AJOL)

    HOD

    artificial intelligence to provide smart triggering pulses for the DVR to mitigate and to provide compensation against voltage sags and swells. The Artificial Neural Network (ANN) was trained ... 90% of the nominal rms value and lasting for 0.5cycles. (10msec for 50Hz power system) up to 1 minute. It is considered as the most ...

  20. (ann) based dynamic voltage restorer

    African Journals Online (AJOL)

    HOD

    artificial intelligence to provide smart triggering pulses for the DVR to mitigate and to provide compensation against ... the starting of large induction motor [6]. ... ANN-based DVR under voltage sags and swells phenomena. In this case, the ANN is trained off-line, and the trained network is employed for on-line control.

  1. A Voltage Quality Detection Method

    DEFF Research Database (Denmark)

    Chen, Zhe; Wei, Mu

    2008-01-01

    This paper presents a voltage quality detection method based on a phase-locked loop (PLL) technique. The technique can detect the voltage magnitude and phase angle of each individual phase under both normal and fault power system conditions. The proposed method has the potential to evaluate various...... power quality disturbances, such as interruptions, sags and imbalances. Simulation studies have been performed. The effectiveness of the proposed method has been demonstrated under the simulated typical power disturbances....

  2. Variable speed wind turbine generator system with current controlled voltage source inverter

    Energy Technology Data Exchange (ETDEWEB)

    Muyeen, S.M., E-mail: muyeen0809@yahoo.co [Dept. of Electrical Engineering, Petroleum Institute, P.O. Box 2533, Abu Dhabi (United Arab Emirates); Al-Durra, Ahmed [Dept. of Electrical Engineering, The Petroleum Institute, P.O. Box 2533, Abu Dhabi (United Arab Emirates); Tamura, J. [Dept. of EEE, Kitami Institute of Technology, 165 Koen-cho, Kitami 090-8507 (Japan)

    2011-07-15

    highlights: {yields} Current controlled voltage source inverter scheme for wind power application. {yields} Low voltage ride through of wind farm. {yields} Variable speed wind turbine driven permanent magnet synchronous generator-operation and control. -- Abstract: The present popular trend of wind power generation is to use variable speed wind turbine (VSWT) driving a doubly fed induction generator (DFIG), wound field synchronous generator (WFSG) or permanent magnet synchronous generator (PMSG). Among them, stability analyses of DFIG type of VSWT have already been reported in many literatures. However, transient stability and low voltage ride through (LVRT) characteristics analyses for synchronous generator type of VSWT is not sufficient enough. This paper focuses on detailed LVRT characteristic analysis of variable speed wind turbine driving a PMSG (VSWT-PMSG) with current controlled voltage source inverter (CC-VSI). Modeling and suitable control strategies for overall system are developed to augment the low voltage ride through capability of variable speed wind generator, considering recent wind farm grid code. Both symmetrical and unsymmetrical faults are analyzed as network disturbances in this paper. The permanent fault due to unsuccessful reclosing of circuit breakers is taken into consideration, which is a salient feature of this study. Moreover, the dynamic characteristic is analyzed using real wind speed data measured in Hokkaido Island, Japan. The proposed control scheme is simulated by using the standard power system simulation package PSCAD/EMTDC and results are verified by comparing that of voltage controlled voltage source inverter scheme available in power system literature.

  3. Protection of Multiterminal HVDC Grids based on Modular Multilevel Converters : DC Fault Ride-Through and AC Grid Support

    NARCIS (Netherlands)

    Kontos, E.

    2018-01-01

    High Voltage DC (HVDC) grids provide an efficient solution for the transmission of bulk power over long distances between the energy production and consumption centers. Up to now, most of the implemented dc connections are point-to-point, creating dc links to strengthen the existing, predominantly

  4. Design and control of single-phase dynamic voltage restorer

    Indian Academy of Sciences (India)

    Dynamic voltage restorer (DVR) is a custom power device used in electrical distribution system for power quality improvement. It ensures regulated voltage supply to the sensitive loads, even in case of voltage sag and swell disturbances in the distribution network. It is a series connected device and compensates voltagesag ...

  5. Dynamic Voltage Restorer Based on Combination of Feed Back and Feed Forward PI

    Directory of Open Access Journals (Sweden)

    Dimas Anton A

    2009-08-01

    Full Text Available Dynamic voltage restorer (DVR is one of equipments to protect sensitive load from voltage drop. DVR is installed series with line feeder by serial transformer which injecting voltage when under voltage occurs. This research is investigate the capability of DVR, which controlled by combination of feed back and feed forward PI, to handle voltage sag and interruption. DVR controls have been designed and implemented in DVR prototype. As a result, in simulation, DVR can maintain voltage in range 90% - 105% nominal voltage. Voltage at load side can be restored to 1 pu and 0.79 pu when voltage sag and interruption respectively. Furthermore, DVR prototype can restore 0.95 pu when voltage sag and 0.54 pu when interruption.

  6. Modeling and Control of a DFIG-Based Wind Turbine During a Grid Voltage Drop

    OpenAIRE

    M. Shahabi; S. Asghar Gholamian; A. Babaie Lajimi

    2011-01-01

    Doubly-fed induction generators (DFIG) are widely used in wind energy generation systems. During a grid voltage drop, performance is degraded with rotor over current deteriorating the fault-ride through (FRT) capability of the DFIG wind-energy generation system. In this paper, a complete mathematical DFIG model is proposed. The rotor is considered fed by a voltage source converter whereas the stator is connected to the grid directly. Output power and electromagnetic torque are controlled usin...

  7. Fault Ride Though Control of Photovoltaic Grid-connected Inverter with Current-limited Capability under Offshore Unbalanced Voltage Conditions

    DEFF Research Database (Denmark)

    Liu, Wenzhao; Guo, Xiaoqiang; Savaghebi, Mehdi

    2016-01-01

    The photovoltaic (PV) inverter installed on board experiences the excessive current stress in case of the offshore unbalanced voltage fault ride through (FRT), which significantly affects the operation reliability of the power supply system. In order to solve the problem, the inherent mechanism...... of the excessive current phenomenon with the conventional fault ride through control is discussed. The quantitative analysis of the current peak value is conducted and a new current-limiting control strategy is proposed to achieve the flexible power control and successful fault ride through in a safe current...... operation area, which is beneficial to the system reliability. Finally, the simulations of conventional and proposed control solutions are carried out. The results verify the effectiveness of the proposed method....

  8. Protection of Multiterminal HVDC Grids based on Modular Multilevel Converters: DC Fault Ride-Through and AC Grid Support

    OpenAIRE

    Kontos, E.

    2018-01-01

    High Voltage DC (HVDC) grids provide an efficient solution for the transmission of bulk power over long distances between the energy production and consumption centers. Up to now, most of the implemented dc connections are point-to-point, creating dc links to strengthen the existing, predominantly ac, electricity grid. However, to optimize the use of assets and energy harvest, multi-terminal HVdc grids are envisioned. Based on recent research and industrial trends, the Multilevel Modular Conv...

  9. Flexible voltage support control for three-phase distributed generation inverters under grid fault

    DEFF Research Database (Denmark)

    Camacho, Antonio; Castilla, Miguel; Miret, Jaume

    2013-01-01

    Operators describe the behavior of the energy source, regulating voltage limits and reactive power injection to remain connected and support the grid under fault. On the basis that different kinds of voltage sags require different voltage support strategies, a flexible control scheme for three phase grid...... connected inverters is proposed. In three phase balanced voltage sags, the inverter should inject reactive power in order to raise the voltage in all phases. In one or two phase faults, the main concern of the distributed generation inverter is to equalize voltages by reducing the negative symmetric...... of this work is the introduction of a control algorithm for reference current generation that provides flexible voltage support under grid faults. Two different voltage sags have been experimentally tested to illustrate the behavior of the proposed voltage support control scheme....

  10. A Novel Wind Turbine Concept Based on an Electromagnetic Coupler and the Study of Its Fault Ride-through Capability

    DEFF Research Database (Denmark)

    You, Rui; Barahona Garzón, Braulio; Chai, Jianyun

    2013-01-01

    and grid voltage support capability can be significantly improved. An electromagnetic coupling speed regulating device (EMCD) is used to connect the gearbox high speed shaft and synchronous generator rotor shaft, transmitting torque to the synchronous generator, while decoupling the gearbox side...... and the synchronous generator, so the synchronous generator torque oscillations during a grid fault are not transmitted to the gearbox. The EMCD is composed of an electromagnetic coupler and a one quadrant operation converter with reduced capability and low cost. A control strategy for the new wind turbine...

  11. Modeling and Control System Design for an Integrated Solar Generation and Energy Storage System with a Ride-Through Capability: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Wang, X.; Yue, M.; Muljadi, E.

    2012-09-01

    This paper presents a generic approach for PV panel modeling. Data for this modeling can be easily obtained from manufacturer datasheet, which provides a convenient way for the researchers and engineers to investigate the PV integration issues. A two-stage power conversion system (PCS) is adopted in this paper for the PV generation system and a Battery Energy Storage System (BESS) can be connected to the dc-link through a bi-directional dc/dc converter. In this way, the BESS can provide some ancillary services which may be required in the high penetration PV generation scenario. In this paper, the fault ride-through (FRT) capability is specifically focused. The integrated BESS and PV generation system together with the associated control systems is modeled in PSCAD and Matlab platforms and the effectiveness of the controller is validated by the simulation results.

  12. Compliance of REE's operational procedure 12.3 regarding fault ride-through capability. The experience of a multi-technology owner

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz Guillen, J.; Giraut Ruso, E.; Quinonez-Varela, G.; Navarrete Pablo-Romero, A.; Rebollo Rico, I.; Hernandez Fernandez de la Pradilla, T. [Acciona Energia, Sarriguren (Spain); Comench, M.P.; Garcia-Gracia, M. [Zaragoza Univ. (Spain). CIRCE

    2009-07-01

    The installed wind power capacity in Spain has rapidly increased over the last years, and consequently, a number of issues associated to the security and reliability of the power system have been prompted. A critical aspect is the fault ride-through capability of wind turbine generators. In 2006, the Spanish TSO published a new Operational Procedure which governs this capability for wind power plants, either new or existing, and was enforced in 2007. This paper describes the requirements that the wind power plants have to fulfil to comply with the Operational Procedure, the multiple technologies that Acciona Energia had to retrofit and the theoretical solutions that were analysed during this process. Also, simulations and field tests are discussed, together with a discussion on the current situation of solutions for old wind power plants, and the lessons learned throughout the retrofit process. (orig.)

  13. A Riding-through Technique for Seamless Transition between Islanded and Grid-Connected Modes of Droop-Controlled Inverters

    Directory of Open Access Journals (Sweden)

    Shang-Hung Hu

    2016-09-01

    Full Text Available This paper presents a seamless transition method for a droop-controlled inverter. The droop control is suitable to make the inverter work as a voltage source in both islanded and grid-connected modes, however, the transfer between theses modes can result in a big inrush current that may damage the system. The proposed method allows the droop-controlled inverter to improve the transient response when transferring between modes, by detecting the inrush current, activating a current control loop during transients, and then transferring back to droop-controlled mode smoothly by using a virtual inductance loop. In addition, a local phase-locked-loop (PLL is proposed to align the inverter voltage with the grid in order to reduce the transient current during the transition. Therefore, the droop-controlled inverter is able to operate in both grid-connected and islanded modes, providing as well a smooth transition between them, requiring neither synchronization signals nor grid-side information. The control algorithm and design procedure are presented. Experimental results from a laboratory prototype validate the effectiveness of the proposed method.

  14. Effect of Oil on Gravity Segregation in SAG Foam Flooding

    NARCIS (Netherlands)

    Hussain, A.A.A.; Amin, A.; Vincent-Bonnieu, S.Y.F.; Andrianov, A; Abdul Hamid, P.; Rossen, W.R.

    2017-01-01

    We report a simulation study of surfactant-alternating-gas (SAG) foam injection into a waterflooded oil reservoir. We show the effects of oil, and of SAG cycle size and number on sweep efficiency, and the longterm impact of a single surfactant slug on the areal sweep efficiency of a gas-flood. Shan

  15. Modeling driving behavior and traffic flow at sags (paper)

    NARCIS (Netherlands)

    Goni Ros, B.; Knoop, V.L.; Van Arem, B.; Hoogendoorn, S.P.

    2013-01-01

    Sags are freeway sections along which gradient changes significantly from downwards to upwards. Sags are often bottlenecks in freeway networks. Capacity decreases due to changes in car-following behavior. We present a microscopic traffic flow model that describes driving behavior and traffic flow

  16. Modeling driving behavior and traffic flow at sags (lecture)

    NARCIS (Netherlands)

    Goni Ros, B.; Knoop, V.L.; Van Arem, B.; Hoogendoorn, S.P.

    2013-01-01

    Sags are freeway sections along which gradient changes significantly from downwards to upwards. Sags are often bottlenecks in freeway networks. Capacity decreases due to changes in car-following behavior. We present a microscopic traffic flow model that describes driving behavior and traffic flow

  17. Reduced semiconductor three-level interline dynamic voltage restorer

    DEFF Research Database (Denmark)

    Zhang, Lei; Loh, Poh Chang; Gao, Feng

    2011-01-01

    The previously proposed Interline Dynamic Voltage Restorer (IDVR) system enhances its capability to compensate for long-term and deep voltage sags from propagating to critical loads in power system without requiring a bulky energy storage device. By having multiple DVRs connected to different...... transmission feeders, the common energy storage in IDVR system can be dynamically replenished from an unaffected feeder so as to maintain the rated power of critical loads in another feeder where voltage sag appears. However, despite its enhancement in compensation capability, the drawbacks faced by original...

  18. Methodology for relative location of voltage sag source using voltage measurements only

    Directory of Open Access Journals (Sweden)

    Jairo Blanco-Solano

    2015-01-01

    Full Text Available Este trabajo presenta una metodología para la localización rela tiva de las fuentes generadoras de hundimientos de tensión y la cual se basa únicamente en mediciones de tensión. Las fallas de red son las perturbaci ones más frecuentes en los sistemas eléctricos y son las causan tes del mayor número de hundimientos de tensión. Así , el algoritmo propuesto conside ra únicamente los hundimientos de tensión originados por fallas de red y requiere un mínimo de tres monitores de tensión para su aplicación. La cali dad de la potencia puede evaluar se automáticamente a través de la caracterización y extracción de información de los registros de tensión. Las tens iones de secuencia positiva son usadas como los descriptores pa ra determinar la localización relativa y la metodol ogía es aplicada en un caso d e estudio por simulación comproba ndo su efectividad. Para la va lidación de los resultados se usa Matlab, toman do como entradas los hundimiento s de tensión simula dos en ATP-EMTP.

  19. Optimized Control Strategy for a Medium-Voltage DVR-Theoretical Investigations and Experimental Results

    DEFF Research Database (Denmark)

    Meyer, Christoph; De Doncker, Rik W.; Li, Yun Wei

    2008-01-01

    Most power quality problems in distribution systems are related to voltage sags. Therefore, different solutions have been examined to compensate these sags to avoid production losses at sensitive loads. Dynamic voltage restorers (DVRs) have been proposed to provide higher power quality. Currently......, a system wide integration of DVRs is hampered because of their high cost, in particular, due to the expensive DC-link energy storage devices. The cost of these DC-link capacitors remains high because the DVR requires a minimum DC-link voltage to be able to operate and to compensate a sag. As a result, only...... a small fraction of the energy stored in the DC-link capacitor is used, which makes it impractical for DVRs to compensate relatively long voltage sags. Present control strategies are only able to minimize the distortions at the load or to allow a better utilization of the storage system by minimizing...

  20. Voltage quality enhancement in distribution system using artificial ...

    African Journals Online (AJOL)

    The aim was to employ artificial intelligence to provide smart triggering pulses for the DVR to mitigate and to provide compensation against voltage sags and swells. The Artificial Neural Network (ANN) was trained online by data gener ated via a 3 - phase programmable voltage generator and these were used as inputs to ...

  1. Down-regulation of OsSAG12-1 results in enhanced senescence ...

    Indian Academy of Sciences (India)

    2013-07-22

    Jul 22, 2013 ... Through BLAST search using AtSAG12 amino acid sequences as query, we identified ... OsSAG12-1 is the closest homologue of AtSAG12 with 64% similar amino acid composition. Expression of. OsSAG12-1 is ..... tive activation of salicylic acid signalling from growth defects. Mol. Plant Pathol. 12 855-865.

  2. Theoretical Analysis on the Short-Circuit Current of Inverter-Interfaced Renewable Energy Generators with Fault-Ride-Through Capability

    Directory of Open Access Journals (Sweden)

    Sumei Liu

    2017-12-01

    Full Text Available Renewable energy generators (REGs usually employ power electronic devices for connecting with the grid, which makes their fault characteristics completely different from those of conventional synchronous generators. In the existing studies, the simulation methods are mainly adopted to analyze fault current contribution from REG. As a result, the explanations on the fault current show diversity and cannot reach a recognized standard. The REGs’ mathematical model in relay-setting calculations is unknown. Thus, this paper theoretically analyses the fault current characteristics of inverter-interfaced REGs (IIREGs with fault-ride-through (FRT ability. In order to understand the fault current characteristics, the FRT control strategy for IIREGs is firstly studied. Then the characteristics of high-frequency and fundamental-frequency fault currents from IIREGs are theoretically analyzed after and during the faults. The affecting factors and duration time of different frequency fault currents are, respectively, revealed. Further, the mathematical expression of fundamental fault currents from IIREGs are derived and verified based on the experimental test bench. The results can be used in estimating the IIREGs’ fault contributions and developing the fault calculation model.

  3. User's Manual for SAG-2 SHARC/SAMM Atmosphere Generator

    National Research Council Canada - National Science Library

    Shroll, Robert

    2003-01-01

    The SHARC Atmosphere Generator (SAG) is a stand-alone, interactive program that utilizes a combination of empirical models to generate atmospheric profiles for Air Force IR radiation codes that account for systematic variability...

  4. Antimicrobial Tolerance of Pseudomonas aeruginosa Biofilms Is Activated during an Early Developmental Stage and Requires the Two-Component Hybrid SagS

    Science.gov (United States)

    Gupta, Kajal; Marques, Cláudia N. H.; Petrova, Olga E.

    2013-01-01

    A hallmark characteristic of biofilms is their extraordinary tolerance to antimicrobial agents. While multiple factors are thought to contribute to the high level of antimicrobial tolerance of biofilms, little is known about the timing of induction of biofilm tolerance. Here, we asked when over the course of their development do biofilms gain their tolerance to antimicrobial agents? We demonstrate that in Pseudomonas aeruginosa, biofilm tolerance is linked to biofilm development, with transition to the irreversible attachment stage regulated by the two-component hybrid SagS, marking the timing when biofilms switch to the high-level tolerance phenotype. Inactivation of sagS rendered biofilms but not planktonic cells more susceptible to tobramycin, norfloxacin, and hydrogen peroxide. Moreover, inactivation of sagS also eliminated the recalcitrance of biofilms to killing by bactericidal antimicrobial agents, a phenotype comparable to that observed upon inactivation of brlR, which encodes a MerR-like transcriptional regulator required for biofilm tolerance. Multicopy expression of brlR in a ΔsagS mutant restored biofilm resistance and recalcitrance to killing by bactericidal antibiotics to wild-type levels. In contrast, expression of sagS did not restore the susceptibility phenotype of ΔbrlR mutant biofilms to wild-type levels, indicating that BrlR functions downstream of SagS. Inactivation of sagS correlated with reduced BrlR levels in biofilms, with the produced BrlR being impaired in binding to the previously described BrlR-activated promoters of the two multidrug efflux pump operons mexAB-oprM and mexEF-oprN. Our findings demonstrate that biofilm tolerance is linked to early biofilm development and SagS, with SagS contributing indirectly to BrlR activation. PMID:23995639

  5. The rice OsSAG12-2 gene codes for a functional protease that ...

    Indian Academy of Sciences (India)

    OsSAG12-1, the closest structural homologue of AtSAG12, is a negativeregulator of developmental and stress-induced cell death. Proteolytic activity has not been established for any SAG12homologues in vitro. Here, we report that OsSAG12-2, the second structural homologue of AtSAG12 from rice, codesfor a functional ...

  6. Performance Evaluation of Three Different Inverter Configurations of DVR for Mitigation of Voltage Events

    Directory of Open Access Journals (Sweden)

    Miska Prasad

    2016-12-01

    Full Text Available The voltage events namely voltage sags and voltage swells represent the most common, frequent and important power quality events in today’s power system. Dynamic voltage restorer (DVR is one of the key components used to mitigate the supply voltage quality disturbances in terms of voltage sags and swells in the distribution system. It consists of an energy storage unit, a voltage source inverter, a filter, a coupling transformer and the control system. This paper presents three different inverter configurations of dynamic voltage restorer (DVR for mitigation of voltage events such as voltage sags and swells with sudden addition or removal of the nonlinear load. These three configurations are voltage source inverter based DVR (VSI-DVR, current source inverter based DVR (CSI-DVR and impedance or Z-source inverter based DVR (ZSI-DVR. The d-q control technique is used to control the operation of the DVR. The response of ZSI-DVR for mitigation of voltage sags and swells are investigated and compared with VSI-DVR and CSI-DVR using MATLAB/SIMULINK environment.

  7. Analysis and Mathematical Model for Restitution of Voltage Using Dynamic Voltage Restorer

    Directory of Open Access Journals (Sweden)

    C. Gopinath

    2014-01-01

    Full Text Available Voltage sag and swell have a major concern in the distribution systems. In order to mitigate the voltage sag and swell, a custom power device called dynamic voltage restorer (DVR is used. The proposed system is a polymer electrolyte membrane (PEM fuel cell based DVR. The energy from the fuel cell is stored in the super capacitor to restitute the voltage. In this proposed DVR, Z-source inverter is used instead of traditional inverter because of buck-boost and shoot through capability. The simulation is performed using three controller topologies: PI controller, synchronous reference frame controller and fuzzy controller and the results are verified using Matlab-Simulink environment.

  8. A comprehensive review of dynamic voltage restorers

    DEFF Research Database (Denmark)

    Farhadi-Kangarlu, Mohammad; Babaei, Ebrahim; Blaabjerg, Frede

    2017-01-01

    will consider all of the fast voltage compensators, i.e. the devices called Static Series Compensator (SSC), sag corrector, Dynamic Sag Corrector (DySC), and other similar devices are also considered. All of these devices will be called DVR since they operate almost in the same way. Some comparative conclusions......During the last half century the Power Quality (PQ) related problems have become important issues. Many solutions have been proposed to address the PQ problems. The most attractive and flexible way is to use power electronic converter based devices such as Dynamic Voltage Restorer (DVR......), Distribution Static Compensator (DSTATCOM), Unified Power Quality Conditioner (UPQC), Uninterruptible Power Supply (UPS), and other devices usually called custom power devices. Among custom power devices, the DVR is the most economical solution to overcome the voltage-related PQ problems. Intensive research...

  9. A Case Study Of Turkish Transmission System For VoltageDips

    OpenAIRE

    Inan, E.; Alboyaci, B.; Bak, Claus Leth

    2009-01-01

    Power quality problems usually appear in the form of voltage sags, transients and harmonics. From these three broad categories of power quality problems, voltage dips account the most disturbances experienced by industrial customers. Voltage dips generally refer to instantaneous short-duration voltage variations. The aim of this paper is to have an idea about voltage dip performance of Turkey Transmission System. Turkey's transmission system has 21 regions. For simulations, 2nd region, which ...

  10. Mitigation of Voltage Dip and Voltage Flickering by Multilevel D-STATCOM

    Directory of Open Access Journals (Sweden)

    M. S. Ballal

    2012-01-01

    Full Text Available The basic power quality problems in the distribution network are voltage sag (dip, voltage flickering, and the service interruptions. STATCOM is a Flexible AC Transmission Systems (FACTS technology device which can independently control the flow of reactive power. This paper presents the simulation and analysis of a STATCOM for voltage dip and voltage flickering mitigation. Simulations are carried out in MATLAB/Simulink to validate the performance of the STATCOM. A comparison between the six-pulse inverter and the five-level diode-clamped inverter is carried out for the performance of 66/11 KV distribution system.

  11. RETRACTED ARTICLE: Dynamic voltage restorer controller using grade algorithm

    Directory of Open Access Journals (Sweden)

    S. Deepa

    2015-12-01

    Full Text Available This paper deals with the terminology and various issues about power quality problems. This problem occurs owing to voltage sag, swell, harmonics, and surges. The sustained overvoltage and undervoltage originated from power system may often damage/or disrupt computerized process. Voltage sags and harmonics disturb the power quality and this can be overcome by custom power device called dynamic voltage restorer (DVR. The DVR is normally installed between the source voltage and critical or sensitive load. The vital role of DVR depends on the efficiency of the control technique involved in switching circuit of the inverter. In this paper, Combination of improved grade algorithm with fuzzy membership function is used to decide the Proportional-Integral coefficients. The DVR works well both in balanced and unbalanced conditions of voltages. The simulation results show the efficiency of the proposed method.

  12. Measurement of binding strength between prey proteins interacting with Toxoplasma gondii SAG1 and SAG2 using isothermal titration calorimetry (ITC).

    Science.gov (United States)

    Lai, Meng-Yee; Lau, Yee-Ling

    2018-03-26

    Following the outcome from a previously performed yeast two-hybrid experiment, the binding strength between T. gondii SAG1 and SAG2 and their respective prey proteins were further confirmed in this study. The sag1, sag2 and their prey genes were amplified and cloned into a pGEMT vector. To express the recombinant proteins, the fragments were then subcloned into a pRSETA vector and transformed into E. coli BL21 (DE3) cells. The recombinant proteins were expressed optimally at 37°C and 1mM of IPTG. The 6X His-tag fusion proteins were purified, dialyzed and concentrated. To confirm the expressed proteins, the recombinant proteins were analysed by SDS-PAGE and Western blot. As expected, the size of SAG1, SAG2, HLY and HZF protein were 32, 23, 28 and 37 kDa, respectively. The purified proteins were loaded onto a MicroCal Auto-iTC200 calorimeter from MicroCal™ to quantify binding strength. ITC results indicated there was a typical binding curve for interactions between SAG1 and HLY protein. However, there was an atypical binding curve obtained for interactions between SAG2 and HZF protein. By observing the data obtained from the ITC assay, both of the human proteins (HLY and HZF) were demonstrated to bind to their respective SAG1 and SAG2 proteins.

  13. Enhanced Decoupled Double Synchronous Reference Frame Current Controller for Unbalanced Grid-Voltage Conditions

    DEFF Research Database (Denmark)

    Reyes, M.; Rodriguez, Pedro; Vazquez, S.

    2012-01-01

    . In these codes, the injection of positive- and negative-sequence current components becomes necessary for fulfilling, among others, the low-voltage ride-through requirements during balanced and unbalanced grid faults. However, the performance of classical dq current controllers, applied to power converters......, under unbalanced grid-voltage conditions is highly deficient, due to the unavoidable appearance of current oscillations. This paper analyzes the performance of the double synchronous reference frame controller and improves its structure by adding a decoupling network for estimating and compensating...

  14. Modeling and Control of a DFIG-Based Wind Turbine During a Grid Voltage Drop

    Directory of Open Access Journals (Sweden)

    M. Shahabi

    2011-10-01

    Full Text Available Doubly-fed induction generators (DFIG are widely used in wind energy generation systems. During a grid voltage drop, performance is degraded with rotor over current deteriorating the fault-ride through (FRT capability of the DFIG wind-energy generation system. In this paper, a complete mathematical DFIG model is proposed. The rotor is considered fed by a voltage source converter whereas the stator is connected to the grid directly. Output power and electromagnetic torque are controlled using field-oriented control (FOC. Simulation results show the efficiency of the controller in exploiting the maximum power of wind.

  15. Effect of Microstructural Evolution on Sagging Behavior of Cold-Rolled Aluminum Foil During the Brazing Thermal Cycle

    Science.gov (United States)

    Liu, Canwei; Xue, Xili; Chen, Xin; Li, Long; Xia, Chengdong; Zhong, Zhaojun; Zhou, Dejing

    2017-11-01

    Effect of microstructural evolution on sagging behavior of aluminum foil was investigated during the brazing thermal cycle. During the brazing thermal cycle, the sagging behavior consists of three stages: slight sagging stage, accelerative sagging stage and slow sagging stage. The sagging of cold-rolled aluminum foil mainly occurs in the accelerative sagging stage, which is governed by recovery under external stress in the sagging test. The coarse recrystallized grain is responsible for the slow sagging stage by reducing grain boundary sliding. Increasing cold-rolled reduction and addition of final annealing heat treatment can improve sagging resistance by shortening recovery process during the brazing thermal cycle. Dissolution of dispersoids has few effects on sagging deformation.

  16. A Case Study Of Turkish Transmission System For VoltageDips

    DEFF Research Database (Denmark)

    Inan, E.; Alboyaci, B.; Bak, Claus Leth

    2009-01-01

    Power quality problems usually appear in the form of voltage sags, transients and harmonics. From these three broad categories of power quality problems, voltage dips account the most disturbances experienced by industrial customers. Voltage dips generally refer to instantaneous short-duration vo...... analysis of voltage dip performance of the whole transmission system, is used to compare with results constructed fault statics from SIMPOW DIPS analysis program real data. SIMPOW DIPS software enables to calculate dip frequency for all busses and lines....

  17. Investigation and Improvement of Transient Response of DVR at Medium Voltage Level

    DEFF Research Database (Denmark)

    Blaabjerg, Frede; Wei Li, Yun; Chaing Loh, Poh

    2007-01-01

    An area of interest for dynamic voltage restorer (DVR) research is the damping of transient oscillations initiated at the start and at the recovery instant from a voltage sag. Nonlinear loads, with harmonic currents close to the DVR filter resonance frequency, can also excite the resonance...

  18. Fuzzy Logic Controlled DC-DC Converter Based Dynamic Voltage Restorer

    Directory of Open Access Journals (Sweden)

    Mustafa İnci

    2015-12-01

    Full Text Available This paper presents fuzzy logic controlled dc-dc boost converter based Dynamic Voltage Restorer (DVR to compensate severe voltage sag problems in an electrical system. DVR absorbs real power from battery to compensate voltage sags in the system. This condition causes reduction in voltage magnitude of dc-link capacitor. Additionally, DVR requires large dc capacitors to compensate long and severe voltage sags in the system. In this study, dc-dc boost converter is connected to DVR for keeping dc link voltage constant. For this propose, a control algorithm based on Fuzzy Logic (FL control is developed for dc-dc boost converter. The main contribution of this study is that Fuzzy Logic (FL is firstly used to generate reference signal for PWM signals of dc-dc converter applied in DVR. FL is a very flexible controller which keeps the dc link voltage constant during voltage sag. The performance results of proposed study are verified with PSCAD/EMDTC.

  19. SAG-UPS attenuates proapoptotic SARM and Noxa to confer survival advantage to early hepatocellular carcinoma.

    Science.gov (United States)

    Chang, S C; Choo, W Q W; Toh, H C; Ding, J L

    2015-01-01

    Hepatocellular carcinoma (HCC) is a deadly cancer because of its commonly late diagnosis and limited treatment options. SAG (sensitive to apoptosis gene)-dependent UPS (ubiquitin-proteasome system) is a key switch between immune-mediated apoptosis and overactivation-mediated protumorigenesis, prompting us to hypothesize that SAG-UPS modulates chronic inflammation-induced tumorigenesis. Here, we investigated the molecular mechanism by which SAG-UPS regulates death/survival of liver cancer cells. By retrospective studies, we found reciprocal expressions of anti-/proapoptotic factors: SAG/SARM and SAG/Noxa in human primary HCC tissues - the antiapoptotic SAG was significantly upregulated whereas the proapoptotic SARM and Noxa were markedly downregulated, suggesting their involvement in hepatocarcinogenesis. Upregulated SAG-UPS effectively manipulates the levels of high-molecular-weight ubiquitinated SARM and Noxa in carcinoma tissues compared with corresponding normal tissues. SAG-overexpressing HCC cell lines display reduced SARM and Noxa (but not Bcl-2, Bax and Bcl-xL), suggesting that SARM and Noxa are specific substrates of SAG-dependent ubiquitination. SARM overexpression activated caspase-3 and caspase-9, reducing cell viability. SAG knockdown significantly elevated apoptosis with increased cytosolic cytochrome c, confirming SAG-mediated antiapoptosis in HCC. SAG overexpression stimulated protumorigenic cytokines, IL-1β, IL-6 and TNF, but not antitumorigenic IL-12p40 and anti-inflammatory IL-10. This is consistent with higher proinflammatory cytokines (IL-1β, IL-6 and TNF) in hepatoma compared with healthy tissues. Altogether, early stage-upregulated SAG-UPS exacerbates hepatocarcinogenesis progression, through: (1) ubiquitination-mediated degradation of proapoptotic SARM and Noxa; and (2) production of protumorigenic cytokines that induce a protumorigenic microenvironment, conferring survival advantage to HCC cells. Thus, we propose SAG-UPS to be an early

  20. Fault Characteristics and Control Strategies of Multiterminal High Voltage Direct Current Transmission Based on Modular Multilevel Converter

    Directory of Open Access Journals (Sweden)

    Fei Chang

    2015-01-01

    Full Text Available The modular multilevel converter (MMC is an emerging voltage source converter topology suitable for multiterminal high voltage direct current transmission based on modular multilevel converter (MMC-MTDC. This paper presents fault characteristics of MMC-MTDC including submodule fault, DC line fault, and fault ride-through of wind farm integration. Meanwhile, the corresponding protection strategies are proposed. The correctness and effectiveness of the control strategies are verified by establishing a three-terminal MMC-MTDC system under the PSCAD/EMTDC electromagnetic transient simulation environment.

  1. A Grid Voltage Measurement Method for Wind Power Systems during Grid Fault Conditions

    Directory of Open Access Journals (Sweden)

    Cheol-Hee Yoo

    2014-11-01

    Full Text Available Grid codes in many countries require low-voltage ride-through (LVRT capability to maintain power system stability and reliability during grid fault conditions. To meet the LVRT requirement, wind power systems must stay connected to the grid and also supply reactive currents to the grid to support the recovery from fault voltages. This paper presents a new fault detection method and inverter control scheme to improve the LVRT capability for full-scale permanent magnet synchronous generator (PMSG wind power systems. Fast fault detection can help the wind power systems maintain the DC-link voltage in a safe region. The proposed fault detection method is based on on-line adaptive parameter estimation. The performance of the proposed method is verified in comparison to the conventional voltage measurement method defined in the IEC 61400-21 standard.

  2. Effect of Doubly Fed Induction GeneratorTidal Current Turbines on Stability of a Distribution Grid under Unbalanced Voltage Conditions

    Directory of Open Access Journals (Sweden)

    Dahai Zhang

    2017-02-01

    Full Text Available This paper analyses the effects of doubly fed induction generator (DFIG tidal current turbines on a distribution grid under unbalanced voltage conditions of the grid. A dynamic model of an electrical power system under the unbalanced network is described in the paper, aiming to compare the system performance when connected with and without DFIG at the same location in a distribution grid. Extensive simulations of investigating the effect of DFIG tidal current turbine on stability of the distribution grid are performed, taking into account factors such as the power rating, the connection distance of the turbine and the grid voltage dip. The dynamic responses of the distribution system are examined, especially its ability to ride through fault events under unbalanced grid voltage conditions. The research has shown that DFIG tidal current turbines can provide a good damping performance and that modern DFIG tidal current power plants, equipped with power electronics and low-voltage ride-through capability, can stay connected to weak electrical grids even under the unbalanced voltage conditions, whilst not reducing system stability.

  3. Modelling Of Converter Characteristics of Wind Energy Conversion System during Voltage Sags

    OpenAIRE

    Pratyusha Dikkala,; B. Srinivasa Rao

    2014-01-01

    The proposed system presents power-control strategies of a grid-connected hybrid generation system with versatile power transfer. This hybrid system allows maximum utilization of freely available renewable energy sources like wind and photovoltaic energies. For this, an adaptive maximum power point tracking (MPPT) algorithm along with standard perturbs and observe method will be used for the system. The turbine rotor speed is the main determinant of mechanical output from wind energy and Sola...

  4. Faulted zone determination using statistical modeling of voltage sag database in power distribution systems

    Directory of Open Access Journals (Sweden)

    Gabriel Ordóñez Plata

    2009-01-01

    Full Text Available En este artículo, se presenta una solución alternativa para el problema de continuidad del servicio asociada a la localización de fallas. La metodología propuesta es de naturaleza estadística y basada en las mezclas finitas. El modelo estadístico es obtenido a partir de la extracción de la magnitud del hueco de tensión registrado durante un evento de falla y de los parámetros de la red y de su topología. El objetivo esta asociado a ofrecer una alternativa económica y de fácil implementación para el desarrollo de estrategias orientadas a mejorar la confiabilidad a partir de la reducción de los tiempos de restauración de los sistemas de distribución. Como resultados más importantes, se presentan los obtenidos en un ejemplo de aplicación en un sistema de 25 kV, en el cual las zonas en falla fueron localizadas con un bajo error en el desempeño del localizador.

  5. Grid voltage sags effects on frequency converter drivers and controlled rectifier drivers

    DEFF Research Database (Denmark)

    Sudrià, Antoni; Teixido, Miquel; Galceran, Samuel

    2005-01-01

    The aim of this article is to increase the under¬standing of the problems arising when using ASD in relation to its environment. To accomplish this, a description of the ASD hardware and the electrical environment will be made, analysing the most sensitive elements. After critical points have bee...

  6. Classification of voltage sags according to the severity of the effects on the induction motor

    Directory of Open Access Journals (Sweden)

    Adolfo Andrés Jaramillo-Matta

    2015-01-01

    Full Text Available En este artículo se clasifican los huecos de tensión simétricos y asimétricos de acuerdo a la severidad de sus efectos sobre el comportamiento de los motores de inducción, utilizando el modelo de doble jaula. Las variables analizadas son: picos de corriente y par, y pérdida de velocidad en régimen transitorio y en estado estable. La severidad de estos efectos se analiza con 14640 huecos, tanto al inicio del hueco como cuando se recupera la tensión, cambiando su tipo, magnitud, duración y punto de onda inicial. Para el análisis se utilizaron tres cargas de par mecánico con comportamiento constante y una carga con comportamiento cuadrático. Los resultados muestran las duraciones y los puntos de la onda inicial que tienen efectos más severos para cada tipo de hueco. Finalmente se obtiene una clasificación que depende tanto del tipo de hueco como de la variable de interés.

  7. Numerical Simulation of Barite Sag in Pipe and Annular Flow

    Directory of Open Access Journals (Sweden)

    Patrick Kabanda

    2017-01-01

    Full Text Available With the ever increasing global energy demand and diminishing petroleum reserves, current advances in drilling technology have resulted in numerous directional wells being drilled as operators strive to offset the ever-rising operating costs. In as much as deviated-well drilling allows drillers to exploit reservoir potential by penetrating the pay zone in a horizontal, rather than vertical, fashion, it also presents conditions under which the weighting agents can settle out of suspension. The present work is categorized into two parts. In the first part, governing equations were built inside a two-dimensional horizontal pipe geometry and the finite element method utilized to solve the equation-sets. In the second part, governing equations were built inside a three-dimensional horizontal annular geometry and the finite volume method utilized to solve the equation-sets. The results of the first part of the simulation are the solid concentration, mixture viscosity, and a prediction of the barite bed characteristics. For the second part, simulation results show that the highest occurrence of barite sag is at low annular velocities, nonrotating drill pipe, and eccentric drill pipe. The CFD approach in this study can be utilized as a research study tool in understanding and managing the barite sag problem.

  8. Salivary agglutinin/DMBT1SAG expression is up-regulated in the presence of salivary gland tumors

    DEFF Research Database (Denmark)

    Bikker, F J; van der Wal, J E; Ligtenberg, A J M

    2004-01-01

    Salivary agglutinin (SAG) is encoded by the gene Deleted in Malignant Brain Tumors 1 (DMBT1) and represents the salivary variant of DMBT1 (DMBT1(SAG)). While SAG is a bona fide anti-caries factor, DMBT1 was proposed as a candidate tumor-suppressor for brain, digestive tract, and lung cancer. Thou...

  9. A New Fast Peak Current Controller for Transient Voltage Faults for Power Converters

    Directory of Open Access Journals (Sweden)

    Jesús Muñoz-Cruzado-Alba

    2015-12-01

    Full Text Available Power converters are the basic unit for the transient voltage fault ride through capability for most renewable distributed generators (DGs. When a transient fault happens, the grid voltage will drop suddenly and probably will also suffer a phase-jump event as well. State-of-the-art voltage fault control techniques regulate the current injected during the grid fault. However, the beginning of the fault could be too fast for the inner current control loops of the inverter, and transient over-current would be expected. In order to avoid the excessive peak current of the methods presented in the literature, a new fast peak current control (FPCC technique is proposed. Controlling the peak current magnitude avoids undesirable disconnection of the distributed generator in a fault state and improves the life expectancy of the converter. Experimental and simulation tests with high power converters provide the detailed behaviour of the method with excellent results.

  10. Power Quality Improvement Using an Enhanced Network-Side-Shunt-Connected Dynamic Voltage Restorer

    Science.gov (United States)

    Fereidouni, Alireza; Masoum, Mohammad A. S.; Moghbel, Moayed

    2015-10-01

    Among the four basic dynamic voltage restorer (DVR) topologies, the network-side shunt-connected DVR (NSSC-DVR) has a relatively poor performance and is investigated in this paper. A new configuration is proposed and implemented for NSSC-DVR to enhance its performance in compensating (un)symmetrical deep and long voltage sags and mitigate voltage harmonics. The enhanced NSSC-DVR model includes a three-phase half-bridge semi-controlled network-side-shunt-connected rectifier and a three-phase full-bridge series-connected inverter implemented with a back-to-back configuration through a bidirectional buck-boost converter. The network-side-shunt-connected rectifier is employed to inject/draw the required energy by NSSC-DVR to restore the load voltage to its pre-fault value under sag/swell conditions. The buck-boost converter is responsible for maintaining the DC-link voltage of the series-connected inverter at its designated value in order to improve the NSSC-DVR capability in compensating deep and long voltage sags/swells. The full-bridge series-connected inverter permits to compensate unbalance voltage sags containing zero-sequence component. The harmonic compensation of the load voltage is achieved by extracting harmonics from the distorted network voltage using an artificial neural network (ANN) method called adaptive linear neuron (Adaline) strategy. Detailed simulations are performed by SIMULINK/MATLAB software for six case studies to verify the highly robustness of the proposed NSSC-DVR model under various conditions.

  11. Immunogenic Eimeria tenella glycosylphosphatidylinositol-anchored surface antigens (SAGs induce inflammatory responses in avian macrophages.

    Directory of Open Access Journals (Sweden)

    Yock-Ping Chow

    Full Text Available At least 19 glycosylphosphatidylinositol (GPI-anchored surface antigens (SAGs are expressed specifically by second-generation merozoites of Eimeria tenella, but the ability of these proteins to stimulate immune responses in the chicken is unknown.Ten SAGs, belonging to two previously defined multigene families (A and B, were expressed as soluble recombinant (r fusion proteins in E. coli. Chicken macrophages were treated with purified rSAGs and changes in macrophage nitrite production, and in mRNA expression profiles of inducible nitric oxide synthase (iNOS and of a panel of cytokines were measured. Treatment with rSAGs 4, 5, and 12 induced high levels of macrophage nitric oxide production and IL-1β mRNA transcription that may contribute to the inflammatory response observed during E. tenella infection. Concomitantly, treatment with rSAGs 4, 5 and 12 suppressed the expression of IL-12 and IFN-γ and elevated that of IL-10, suggesting that during infection these molecules may specifically impair the development of cellular mediated immunity.In summary, some E. tenella SAGs appear to differentially modulate chicken innate and humoral immune responses and those derived from multigene family A (especially rSAG 12 may be more strongly linked with E. tenella pathogenicity associated with the endogenous second generation stages.

  12. Twenty year experience of the oral rabies vaccine SAG2 in wildlife: a global review.

    Science.gov (United States)

    Mähl, Philippe; Cliquet, Florence; Guiot, Anne-Laure; Niin, Enel; Fournials, Emma; Saint-Jean, Nathalie; Aubert, Michel; Rupprecht, Charles E; Gueguen, Sylvie

    2014-08-10

    The SAG2 vaccine (RABIGEN® SAG2) is a modified live attenuated rabies virus vaccine, selected from the SAD Bern strain in a two-step process of amino acid mutation using neutralizing monoclonal antibodies. The strain is genetically stable and does not spread in vivo or induce a persistent infection. Its absence of residual pathogenicity was extensively demonstrated in multiple target and non target species (such as wild carnivores and rodent species), including non-human primates. The efficacy of SAG2 baits was demonstrated according to the EU requirements for the red fox and raccoon dog. The use of safe and potent rabies vaccines such as SAG2 largely contributed to the elimination of rabies in Estonia, France, Italy and Switzerland. Importantly, these countries were declared free of rabies after few years of oral vaccination campaigns with SAG2 baits distributed with an appropriate strategy. The excellent tolerance of the SAG2 vaccine has been confirmed in the field since its first use in 1993. No safety issues have been reported, and in particular no vaccine-induced rabies cases were diagnosed, after the distribution of more than 20 million SAG2 baits in Europe.

  13. Patterns and role of diversifying selection in the evolution of Toxoplasma gondii SAG5 locus.

    Science.gov (United States)

    Elsheikha, Hany M; Zhao, Xiangrong

    2008-06-01

    The higher intergenotypic polymorphism of the surface antigen genes 5 (SAG5)A, SAG5C, and SAG5E in Toxoplasma gondii was proposed to be the outcome of positive selection pressure favoring variation within these loci. However, the exact nature and magnitude of this selection is not completely known. To address this issue, the amino acids on which natural selection may operate were identified by comparing the ratios of nonsynonymous and synonymous substitutions (pN/pS) of homologous DNA sequences in strains belonging to the three major genotypes of T. gondii. Both positive and negative selections were detected and are likely to have contributed to shaping the patterns of nucleotide substitution and polymorphism in SAG5 genes. Several sites identified in SAG5 loci as likely to be under positive selection suggesting that diversifying selection may have promoted divergence in these genes. Also, it was noted that the SAG5 genetic loci contain many areas that exhibit signs of purifying selection; some of these areas might be the attractive candidates for drug targets. Phylogenetic analysis using the neighbor-joining and maximum parsimony methods grouped the SAG5 sequences of T. gondii strains into three distinct statistically well-supported evolutionary lineages. These findings carry important implications for human and veterinary toxoplasmosis epidemiology and may provide important insights into the pathways through which virulence has evolved in T. gondii.

  14. Control model design to limit DC-link voltage during grid fault in a dfig variable speed wind turbine

    Science.gov (United States)

    Nwosu, Cajethan M.; Ogbuka, Cosmas U.; Oti, Stephen E.

    2017-08-01

    This paper presents a control model design capable of inhibiting the phenomenal rise in the DC-link voltage during grid- fault condition in a variable speed wind turbine. Against the use of power circuit protection strategies with inherent limitations in fault ride-through capability, a control circuit algorithm capable of limiting the DC-link voltage rise which in turn bears dynamics that has direct influence on the characteristics of the rotor voltage especially during grid faults is here proposed. The model results so obtained compare favorably with the simulation results as obtained in a MATLAB/SIMULINK environment. The generated model may therefore be used to predict near accurately the nature of DC-link voltage variations during fault given some factors which include speed and speed mode of operation, the value of damping resistor relative to half the product of inner loop current control bandwidth and the filter inductance.

  15. Voltage support transformer, a new solution for energy quality; Transformador de suporte de tensao, uma nova solucao de qualidade da energia

    Energy Technology Data Exchange (ETDEWEB)

    Kojovic, Ljubomir A. [Cooper Power Systems (United States)

    2008-04-15

    Specifically designed for performing the mutual coupling of similar phases of two or more lines, the equipment which is serial connected with the loads, uses the current variation caused by shortages or other perturbations to sustain the voltage on the lines affected in near levels to the existent before the occurrence, eliminating therefore voltage sags and overvoltage caused by the manoeuvres of shunt capacitors.

  16. Coordination of horizontal and sag vertical curves on two-lane rural roads: Driving simulator study

    Directory of Open Access Journals (Sweden)

    Francesco Bella

    2015-07-01

    The primary result was that on suggested sag combinations, the driver's speed behavior did not differ in any statistically significant way from that on the reference curves. Whereas the critical sag combinations (configurations that should be avoided caused high values of maximum speed reduction along the tangent–curve transition, which pointed to the driver's reaction to an incorrect perception of the road alignment. Therefore, this result confirmed the effectiveness of the road design guidelines for the coordination of horizontal curves and sag vertical curves.

  17. A Robust Control Scheme for Medium-Voltage-Level DVR Implementation

    DEFF Research Database (Denmark)

    Blaabjerg, Frede; Loh, Poh Chiang; Li, Yun Wei

    2007-01-01

    of Hinfin controller weighting function selection, inner current loop tuning, and system disturbance rejection capability is presented. Finally, the designed control scheme is extensively tested on a laboratory 10-kV MV-level DVR system with varying voltage sag (balanced and unbalanced) and loading (linear......In this paper, a robust control scheme with an outer Hinfin voltage control loop and an inner current control loop is designed and implemented on a medium-voltage (MV)-level dynamic voltage restorer (DVR) system. Through a simple selection of weighting functions, the synthesized Hinfin controller....../nonlinear load and induction motor load) conditions. It is shown that the proposed control scheme is effective in both balanced and unbalanced sag compensation and load disturbance rejection, as its robustness is explicitly specified....

  18. Performance Evaluation of Type-3 PLLs Under Wide Variation in Input Voltage and Frequency

    DEFF Research Database (Denmark)

    Aravind, C. K.; Rani, B.Indu; Chakkarapani, M.

    2017-01-01

    bandwidth, both the single loop and dual loop Type-3 PLL exhibit similar dynamics provided the supply voltage is balanced. However, under voltage sag conditions, dual loop PLL shows improved dynamic response without affecting its stability. Further, the tracking time is reduced as the feed forward frequency......This paper presents a detailed analysis of Type-3 PLL under wide variation in input voltage and frequency. Using small signal modeling, the performance of both single loop and dual loop type-3 PLL for variation in input voltage and frequency is studied. The analysis shows that for the same...

  19. Implication of CT table sag on geometrical accuracy during virtual simulation.

    Science.gov (United States)

    Zullo, John R; Kudchadker, Rajat; Wu, Richard; Lee, Andrew; Prado, Karl

    2007-01-01

    Computed tomography (CT) scanners are used in hospitals worldwide for radiation oncology treatment simulation. It is critical that the process very accurately represents the patient positioning to be used during the administration of radiation therapy to minimize the dose delivery to normal tissue. Unfortunately, this is not always the case. One problem is that some degree of vertical displacement, or sag, occurs when the table is extended from its base when under a clinical weight load, a problem resulting from mechanical limitations of the CT table. In an effort to determine the extent of the problem, we measured and compared the degree of table sag for various CT scanner tables at our institution. A clinically representative weight load was placed on each table, and the amount of table sag was measured for varying degrees of table extension from its base. Results indicated that the amount of table sag varied from approximately 0.7 to 6.6 mm and that the amount of table sag varied not only between tables from different manufacturers but also between tables of the same model from the same manufacturer. Failure to recognize and prevent this problem could lead to incorrectly derived isocenter localization and subsequent patient positioning errors. Treatment site-specific and scanner-based laser offset correction should be implemented for each patient's virtual simulation procedure. In addition, the amount of sag should be measured under a clinically representative weight load upon CT-simulator commissioning.

  20. Improving Performance of LVRT Capability in Single-phase Grid-tied PV Inverters by a Model Predictive Controller

    DEFF Research Database (Denmark)

    Zangeneh Bighash, Esmaeil; Sadeghzadeh, Seyed Mohammad; Ebrahimzadeh, Esmaeil

    2018-01-01

    New interconnection standards for Photovoltaic systems are going to be mandatory in some countries. Such that the next generation of PV should support a full range of operation mode like in a power plant and also support Low-Voltage Ride-Through (LVRT) capability during voltage sag fault. Since...... the voltage sag period is short, a fast dynamic performance along with a soft behavior of the controller is the most important issue in the LVRT duration. Recently, some methods like Proportional Resonant (PR) controllers, have been presented to control the single phase PV systems in LVRT mode. However...

  1. IMPROVING ENERGY EFFICIENCY VIA OPTIMIZED CHARGE MOTION AND SLURRY FLOW IN PLANT SCALE SAG MILLS

    Energy Technology Data Exchange (ETDEWEB)

    Raj K. Rajamani; Sanjeeva Latchireddi; Sravan K. Prathy; Trilokyanath Patra

    2005-12-01

    The U.S. mining industry operates approximately 80 semi-autogenesis grinding mills (SAG) throughout the United States. Depending on the mill size the SAG mills draws between 2 MW and 17 MW. The product from the SAG mill is further reduced in size using pebble crushers and ball mills. Hence, typical gold or copper ore requires between 2.0 and 7.5 kWh per ton of energy to reduce the particle size. Considering a typical mining operation processes 10,000 to 100,000 tons per day the energy expenditure in grinding is 50 percent of the cost of production of the metal. A research team from the University of Utah is working to make inroads into saving energy in these SAG mills. In 2003, Industries of the Future Program of the Department of Energy tasked the University of Utah team to build a partnership between the University and the mining industry for the specific purpose of reducing energy consumption in SAG mills. A partnership was formed with Cortez Gold Mines, Kennecott Utah Copper Corporation, Process Engineering Resources Inc. and others. In the current project, Cortez Gold Mines played a key role in facilitating the 26-ft SAG mill at Cortez as a test mill for this study. According to plant personnel, there were a number of unscheduled shut downs to repair broken liners and the mill throughput fluctuated depending on ore type. The University team had two softwares, Millsoft and FlowMod to tackle the problem. Millsoft is capable of simulating the motion of charge in the mill. FlowMod calculates the slurry flow through the grate and pulp lifters. Based on this data the two models were fine-tuned to fit the Cortez SAG will. In the summer of 2004 a new design of shell lifters were presented to Cortez and in September 2004 these lifters were installed in the SAG mill. By December 2004 Cortez Mines realized that the SAG mill is drawing approximately 236-kW less power than before while maintaining the same level of production. In the first month there was extreme cycling

  2. SagE induces highly effective protective immunity against Streptococcus iniae mainly through an immunogenic domain in the extracellular region.

    Science.gov (United States)

    Sun, Yun; Sun, Li; Xing, Ming-qing; Liu, Chun-sheng; Hu, Yong-hua

    2013-11-12

    Streptococcus iniae is a Gram-positive bacterium and a severe pathogen of a wide range of farmed fish. S. iniae possesses a virulence-associated streptolysin S cluster composed of several components, one of which is SagE. SagE a transmembrane protein with one major extracellular region named ECR. This study aimed to develop a SagE-based DNA candidate vaccine against streptococcosis and examine the immunoprotective mechanism of the vaccine. We constructed a DNA vaccine, pSagE, based on the sagE gene and examined its immunological property in a Japanese flounder (Paralichthys olivaceus) model. The results showed that at 7 days post-vaccination, expression of SagE at transcription and translation levels was detected in the tissues of the vaccinated fish. After challenge with S. iniae at one and two months post-vaccination, pSagE-vaccinated fish exhibited relative percent survival (RPS) of 95% and 88% respectively. Immunological analysis showed that (i) pSagE significantly upregulated the expression of a wide range of immune genes, (ii) pSagE induced the production of specific serum antibodies that bound whole-cell S. iniae, and (iii) treatment of S. iniae with pSagE-induced antibodies blocked bacterial invasion of host cells. To localize the immunoprotective domain of SagE, the ECR-expressing DNA vaccine pSagEECR was constructed. Immunization analysis showed that flounder vaccinated with pSagEECR exhibited a RPS of 68%, and that pSagEECR induced serum antibody production and immune gene expression in a manner similar to, though to lower magnitudes than, those induced by pSagE. We in this study developed a DNA vaccine, pSagE, which induces highly protective immunity against S. iniae. The protective effect of pSagE is probably due to its ability to elicit systemic immune response, in particular that of the humoral branch, which leads to production of specific serum antibodies that impair bacterial infection. These results add insights to the immunoprotective mechanism

  3. Electrical engineering unit for the reactive power control of the load bus at the voltage instability

    Science.gov (United States)

    Kotenev, A. V.; Kotenev, V. I.; Kochetkov, V. V.; Elkin, D. A.

    2018-01-01

    For the purpose of reactive power control error reduction and decrease of the voltage sags in the electric power system caused by the asynchronous motors started the mathematical model of the load bus was developed. The model was built up of the sub-models of the following elements: a transformer, a transmission line, a synchronous and an asynchronous loads and a capacitor bank load, and represents the automatic reactive power control system taking into account electromagnetic processes of the asynchronous motors started and reactive power changing of the electric power system elements caused by the voltage fluctuation. The active power/time and reactive power/time characteristics based on the recommended procedure of the equivalent electric circuit parameters calculation were obtained. The derived automatic reactive power control system was shown to eliminate the voltage sags in the electric power system caused by the asynchronous motors started.

  4. The digital algorithm for fast detecting and identifying the asymmetry of voltages in three-phase electric grids of mechanical engineering facilities

    Science.gov (United States)

    Shonin, O. B.; Kryltcov, S. B.; Novozhilov, N. G.

    2017-02-01

    The paper considers a new technique for the fast method of extracting symmetrical components of unbalanced voltages caused by the faults in electric grids of mechanical engineering facilities. The proposed approach is based on the iterative algorithm that checks if the set of at least three voltage discrete measurements belongs to a specific ellipse trajectory of the voltage space vector. Using classification of unbalanced faults in the grid and results of decomposing the voltages into symmetrical components, the algorithm is capable to discriminate between one-phase, two-phase and three-phase voltage sags. The paper concludes that results of simulation in Simulink environment have proved the correctness of the proposed algorithm for detecting and identifying the unbalanced voltage sags in the electrical grid under condition that it is free from high order harmonics.

  5. The Static WKB Solution to Catenary Problems with Large Sag and Bending Stiffness

    Directory of Open Access Journals (Sweden)

    Yuhung Hsu

    2014-01-01

    Full Text Available Large sag with a bending stiffness catenary is a subject that draws attention in the realm of fatigue analysis, estimation of suspension cable sag for bridge cable hoisting, and ocean engineering of the employment of mooring systems. However, the bending stiffness is the cause of boundary layers at the anchorage of cables, thereby finding a solution of the differential equation can be extremely difficult. Previous studies have tackled this problem with the perturbation method; yet, due to the complexity of the matching process and solution finding, the method might not be an ideal solution for engineering applications. Moreover, the finite difference method and the finite element method in numerical analysis can often be ineffective because of inappropriate parameter configuration and the drastic variation of functions in the boundary layers. Therefore, this study proposed a novel bending moment expression of a large sag catenary. The expression was derived from the sag identified using bending moment equations, and a solution was found by applying the WKB method (Wentzel-Kramers-Brillouin method to overcome the complex problem of boundary layers. Consequently, a simple solution of various mechanical properties in a cable with bending stiffness and large sag could be obtained.

  6. Local Dynamic Reactive Power for Correction of System Voltage Problems

    Energy Technology Data Exchange (ETDEWEB)

    Kueck, John D [ORNL; Rizy, D Tom [ORNL; Li, Fangxing [ORNL; Xu, Yan [ORNL; Li, Huijuan [University of Tennessee, Knoxville (UTK); Adhikari, Sarina [ORNL; Irminger, Philip [ORNL

    2008-12-01

    Distribution systems are experiencing outages due to a phenomenon known as local voltage collapse. Local voltage collapse is occurring in part because modern air conditioner compressor motors are much more susceptible to stalling during a voltage dip than older motors. These motors can stall in less than 3 cycles (.05s) when a fault, such as on the sub-transmission system, causes voltage to sag to 70 to 60%. The reasons for this susceptibility are discussed in the report. During the local voltage collapse, voltages are depressed for a period of perhaps one or two minutes. There is a concern that these local events are interacting together over larger areas and may present a challenge to system reliability. An effective method of preventing local voltage collapse is the use of voltage regulation from Distributed Energy Resources (DER) that can supply or absorb reactive power. DER, when properly controlled, can provide a rapid correction to voltage dips and prevent motor stall. This report discusses the phenomenon and causes of local voltage collapse as well as the control methodology we have developed to counter voltage sag. The problem is growing because of the use of low inertia, high efficiency air conditioner (A/C) compressor motors and because the use of electric A/C is growing in use and becoming a larger percentage of system load. A method for local dynamic voltage regulation is discussed which uses reactive power injection or absorption from local DER. This method is independent, rapid, and will not interfere with conventional utility system voltage control. The results of simulations of this method are provided. The method has also been tested at the ORNL s Distributed Energy Communications and Control (DECC) Laboratory using our research inverter and synchronous condenser. These systems at the DECC Lab are interconnected to an actual distribution system, the ORNL distribution system, which is fed from TVA s 161kV sub-transmission backbone. The test results

  7. CARACTERIZACIÓN DE LUMINARIAS TIPO HALURO METÁLICO ANTE EVENTOS SAG

    Directory of Open Access Journals (Sweden)

    Bonie Johana Restrepo Cuestas

    Full Text Available Este artículo plantea una metodología para la caracterización de luminarias de haluro metálico, ante eventos sag. Inicialmente, se diseñó y construyó un generador de eventos sag. Luego, se planteó un esquema de pruebas, que fue utilizado para analizar el comportamiento de un tipo de luminarias de alta densidad de descarga tipo Metal Halide, ante eventos sag. Finalmente, tomando como referente el estándar SEMI F-47, se realizó la construcción de una curva característica que muestra la región de operación de la luminaria.

  8. Synthesis, morphological control, and antibacterial properties of hollow/solid Ag2S/Ag heterodimers

    KAUST Repository

    Pang, Maolin

    2010-08-11

    Ag2S and Ag are important functional materials that have received considerable research interest in recent years. In this work, we develop a solution-based synthetic method to combine these two materials into hollow/solid Ag2S/Ag heterodimers at room temperature. Starting from monodisperse Cu2O solid spheres, CuS hollow spheres can be converted from Cu2O through a modified Kirkendall process, and the obtained CuS can then be used as a solid precursor for preparation of the Ag2S/Ag heterodimers through ion exchange and photo-assisted reduction. We have found that formation of the Ag2S/Ag heterodimers is instantaneous, and the size of Ag nanocrystals on the hollow spheres of Ag2S can be controlled by changing the concentration and power of reducing agents in the synthesis. The growth of Ag nanoparticles on hollow spheres of Ag2S in the dimers is along the [111] direction of the silver crystal; the light absorption properties have also been investigated. Furthermore, coupling or tripling of Ag2S/Ag heterodimers into dumbbell-like trimers ((Ag 2S)2/Ag, linear) and triangular tetramers ((Ag 2S)3/Ag, coplanar) can also be attained at 60°C by adding the bidentate ligand ethylenediamine as a cross-linking agent. To test the applicability of this highly asymmetric dipolar composite, photocatalytic inactivation of Escherichia coli K-12 in the presence of the as-prepared Ag 2S/Ag heterodimers has been carried out under UV irradiation. The added Ag2S/Ag heterodimers show good chemical stability under prolonged UV irradiation, and no appreciable solid dissolution is found. Possible mechanisms regarding the enhanced antibacterial activity have also been addressed. © 2010 American Chemical Society.

  9. Disruption of the Arabidopsis Defense Regulator Genes SAG101, EDS1, and PAD4 Confers Enhanced Freezing Tolerance.

    Science.gov (United States)

    Chen, Qin-Fang; Xu, Le; Tan, Wei-Juan; Chen, Liang; Qi, Hua; Xie, Li-Juan; Chen, Mo-Xian; Liu, Bin-Yi; Yu, Lu-Jun; Yao, Nan; Zhang, Jian-Hua; Shu, Wensheng; Xiao, Shi

    2015-10-05

    In Arabidopsis, three lipase-like regulators, SAG101, EDS1, and PAD4, act downstream of resistance protein-associated defense signaling. Although the roles of SAG101, EDS1, and PAD4 in biotic stress have been extensively studied, little is known about their functions in plant responses to abiotic stresses. Here, we show that SAG101, EDS1, and PAD4 are involved in the regulation of freezing tolerance in Arabidopsis. With or without cold acclimation, the sag101, eds1, and pad4 single mutants, as well as their double mutants, exhibited similarly enhanced tolerance to freezing temperatures. Upon cold exposure, the sag101, eds1, and pad4 mutants showed increased transcript levels of C-REPEAT/DRE BINDING FACTORs and their regulons compared with the wild type. Moreover, freezing-induced cell death and accumulation of hydrogen peroxide were ameliorated in sag101, eds1, and pad4 mutants. The sag101, eds1, and pad4 mutants had much lower salicylic acid (SA) and diacylglycerol (DAG) contents than the wild type, and exogenous application of SA and DAG compromised the freezing tolerance of the mutants. Furthermore, SA suppressed the cold-induced expression of DGATs and DGKs in the wild-type leaves. These findings indicate that SAG101, EDS1, and PAD4 are involved in the freezing response in Arabidopsis, at least in part, by modulating the homeostasis of SA and DAG. Copyright © 2015 The Author. Published by Elsevier Inc. All rights reserved.

  10. Improving Energy Efficiency Via Optimized Charge Motion and Slurry Flow in Plant Scale Sag Mills

    Energy Technology Data Exchange (ETDEWEB)

    Raj K. Rajamani; Jose Angel Delgadillo

    2006-07-21

    A research team from the University of Utah is working to make inroads into saving energy in these SAG mills. In 2003, Industries of the Future Program of the Department of Energy tasked the University of Utah team to build a partnership between the University and the mining industry for the specific purpose of reducing energy consumption in SAG mills. A partnership was formed with Cortez Gold Mines, Kennecott Utah Copper Corporation, Process Engineering Resources Inc. and Outokumpu Technology. In the current project, Cortez Gold Mines played a key role in facilitating the 26-ft SAG mill at Cortez as a test mill for this study. According to plant personnel, there were a number of unscheduled shut downs to repair broken liners and the mill throughput fluctuated depending on ore type. The University team had two softwares, Millsoft and FlowMod to tackle the problem. Millsoft is capable of simulating the motion of charge in the mill. FlowMod calculates the slurry flow through the grate and pulp lifters. Based on this data the two models were fine-tuned to fit the Cortez SAG will. In the summer of 2004 a new design of shell lifters were presented to Cortez and in September 2004 these lifters were installed in the SAG mill. By December 2004 Cortez Mines realized that the SAG mill is drawing approximately 236-kW less power than before while maintaining the same level of production. In the first month there was extreme cycling and operators had to learn more. Now the power consumption is 0.3-1.3 kWh/ton lower than before. The actual SAG mill power draw is 230-370 kW lower. Mill runs 1 rpm lesser in speed on the average. The recirculation to the cone crusher is reduced by 1-10%, which means more efficient grinding of critical size material is taking place in the mill. All of the savings have resulted in reduction of operating cost be about $0.023-$0.048/ ton. After completing the shell lifter design, the pulp lifter design was taken up. Through a series of mill surveys and

  11. Preparation of Power Distribution System for High Penetration of Renewable Energy Part I. Dynamic Voltage Restorer for Voltage Regulation Pat II. Distribution Circuit Modeling and Validation

    Science.gov (United States)

    Khoshkbar Sadigh, Arash

    Part I: Dynamic Voltage Restorer In the present power grids, voltage sags are recognized as a serious threat and a frequently occurring power-quality problem and have costly consequence such as sensitive loads tripping and production loss. Consequently, the demand for high power quality and voltage stability becomes a pressing issue. Dynamic voltage restorer (DVR), as a custom power device, is more effective and direct solutions for "restoring" the quality of voltage at its load-side terminals when the quality of voltage at its source-side terminals is disturbed. In the first part of this thesis, a DVR configuration with no need of bulky dc link capacitor or energy storage is proposed. This fact causes to reduce the size of the DVR and increase the reliability of the circuit. In addition, the proposed DVR topology is based on high-frequency isolation transformer resulting in the size reduction of transformer. The proposed DVR circuit, which is suitable for both low- and medium-voltage applications, is based on dc-ac converters connected in series to split the main dc link between the inputs of dc-ac converters. This feature makes it possible to use modular dc-ac converters and utilize low-voltage components in these converters whenever it is required to use DVR in medium-voltage application. The proposed configuration is tested under different conditions of load power factor and grid voltage harmonic. It has been shown that proposed DVR can compensate the voltage sag effectively and protect the sensitive loads. Following the proposition of the DVR topology, a fundamental voltage amplitude detection method which is applicable in both single/three-phase systems for DVR applications is proposed. The advantages of proposed method include application in distorted power grid with no need of any low-pass filter, precise and reliable detection, simple computation and implementation without using a phased locked loop and lookup table. The proposed method has been verified

  12. SAG2 locus genotyping of Toxoplasma gondii in meat products of ...

    African Journals Online (AJOL)

    T. gondii DNA was detected in 16.6, 19.1, 15 and 56.6%, in salami, sausages, and hamburger and kebab samples, respectively. Genotyping by restriction fragment length polymorphism (RFLP) analysis of SAG2 locus revealed that all of the samples belonged to genotype I. The detection of the parasite in uncooked meat ...

  13. Inactivation of SAG E3 ubiquitin ligase blocks embryonic stem cell differentiation and sensitizes leukemia cells to retinoid acid.

    Directory of Open Access Journals (Sweden)

    Mingjia Tan

    Full Text Available Sensitive to Apoptosis Gene (SAG, also known as RBX2 (RING box protein-2, is the RING component of SCF (SKP1, Cullin, and F-box protein E3 ubiquitin ligase. Our previous studies have demonstrated that SAG is an anti-apoptotic protein and an attractive anti-cancer target. We also found recently that Sag knockout sensitized mouse embryonic stem cells (mES to radiation and blocked mES cells to undergo endothelial differentiation. Here, we reported that compared to wild-type mES cells, the Sag(-/- mES cells were much more sensitive to all-trans retinoic acid (RA-induced suppression of cell proliferation and survival. While wild-type mES cells underwent differentiation upon exposure to RA, Sag(-/- mES cells were induced to death via apoptosis instead. The cell fate change, reflected by cellular stiffness, can be detected as early as 12 hrs post RA exposure by AFM (Atomic Force Microscopy. We then extended this novel finding to RA differentiation therapy of leukemia, in which the resistance often develops, by testing our hypothesis that SAG inhibition would sensitize leukemia to RA. Indeed, we found a direct correlation between SAG overexpression and RA resistance in multiple leukemia lines. By using MLN4924, a small molecule inhibitor of NEDD8-Activating Enzyme (NAE, that inactivates SAG-SCF E3 ligase by blocking cullin neddylation, we were able to sensitize two otherwise resistant leukemia cell lines, HL-60 and KG-1 to RA. Mechanistically, RA sensitization by MLN4924 was mediated via enhanced apoptosis, likely through accumulation of pro-apoptotic proteins NOXA and c-JUN, two well-known substrates of SAG-SCF E3 ligase. Taken together, our study provides the proof-of-concept evidence for effective treatment of leukemia patients by RA-MLN4924 combination.

  14. Detection and correction for EPID and gantry sag during arc delivery using cine EPID imaging.

    Science.gov (United States)

    Rowshanfarzad, Pejman; Sabet, Mahsheed; O'Connor, Daryl J; McCowan, Peter M; McCurdy, Boyd M C; Greer, Peter B

    2012-02-01

    Electronic portal imaging devices (EPIDs) have been studied and used for pretreatment and in-vivo dosimetry applications for many years. The application of EPIDs for dosimetry in arc treatments requires accurate characterization of the mechanical sag of the EPID and gantry during rotation. Several studies have investigated the effects of gravity on the sag of these systems but each have limitations. In this study, an easy experiment setup and accurate algorithm have been introduced to characterize and correct for the effect of EPID and gantry sag during arc delivery. Three metallic ball bearings were used as markers in the beam: two of them fixed to the gantry head and the third positioned at the isocenter. EPID images were acquired during a 360° gantry rotation in cine imaging mode. The markers were tracked in EPID images and a robust in-house developed MATLAB code was used to analyse the images and find the EPID sag in three directions as well as the EPID + gantry sag by comparison to the reference gantry zero image. The algorithm results were then tested against independent methods. The method was applied to compare the effect in clockwise and counter clockwise gantry rotations and different source-to-detector distances (SDDs). The results were monitored for one linear accelerator over a course of 15 months and six other linear-accelerators from two treatment centers were also investigated using this method. The generalized shift patterns were derived from the data and used in an image registration algorithm to correct for the effect of the mechanical sag in the system. The Gamma evaluation (3%, 3 mm) technique was used to investigate the improvement in alignment of cine EPID images of a fixed field, by comparing both individual images and the sum of images in a series with the reference gantry zero image. The mechanical sag during gantry rotation was dependent on the gantry angle and was larger in the in-plane direction, although the patterns were not

  15. Effect of codon optimization and subcellular targeting on Toxoplasma gondii antigen SAG1 expression in tobacco leaves to use in subcutaneous and oral immunization in mice.

    Science.gov (United States)

    Laguía-Becher, Melina; Martín, Valentina; Kraemer, Mauricio; Corigliano, Mariana; Yacono, María L; Goldman, Alejandra; Clemente, Marina

    2010-07-15

    Codon optimization and subcellular targeting were studied with the aim to increase the expression levels of the SAG178-322 antigen of Toxoplasma gondii in tobacco leaves. The expression of the tobacco-optimized and native versions of the SAG1 gene was explored by transient expression from the Agrobacterium tumefaciens binary expression vector, which allows targeting the recombinant protein to the endoplasmic reticulum (ER) and the apoplast. Finally, mice were subcutaneously and orally immunized with leaf extracts-SAG1 and the strategy of prime boost with rSAG1 expressed in Escherichia coli was used to optimize the oral immunization with leaf extracts-SAG1. Leaves agroinfiltrated with an unmodified SAG1 gene accumulated 5- to 10-fold more than leaves agroinfiltrated with a codon-optimized SAG1 gene. ER localization allowed the accumulation of higher levels of native SAG1. However, no significant differences were observed between the mRNA accumulations of the different versions of SAG1. Subcutaneous immunization with leaf extracts-SAG1 (SAG1) protected mice against an oral challenge with a non-lethal cyst dose, and this effect could be associated with the secretion of significant levels of IFN-gamma. The protection was increased when mice were ID boosted with rSAG1 (SAG1+boost). This group elicited a significant Th1 humoral and cellular immune response characterized by high levels of IFN-gamma. In an oral immunization assay, the SAG1+boost group showed a significantly lower brain cyst burden compared to the rest of the groups. Transient agroinfiltration was useful for the expression of all of the recombinant proteins tested. Our results support the usefulness of endoplasmic reticulum signal peptides in enhancing the production of recombinant proteins meant for use as vaccines. The results showed that this plant-produced protein has potential for use as vaccine and provides a potential means for protecting humans and animals against toxoplasmosis.

  16. Improving Energy Efficiency Via Optimized Charge Motion and Slurry Flow in Plant Scale Sag Mills

    Energy Technology Data Exchange (ETDEWEB)

    Raj K. Rajamani

    2006-07-21

    A research team from the University of Utah is working to make inroads into saving energy in these SAG mills. In 2003, Industries of the Future Program of the Department of Energy tasked the University of Utah team to build a partnership between the University and the mining industry for the specific purpose of reducing energy consumption in SAG mills. A partnership was formed with Cortez Gold Mines, Outokumpu Technology, Kennecott Utah Copper Corporation, and Process Engineering Resources Inc. At Cortez Gold Operations the shell and pulp lifters of the semiautogenous grinding mill was redesigned. The redesigned shell lifter has been in operation for over three years and the redesigned pulp lifter has been in operation for over nine months now. This report summarizes the dramatic reductions in energy consumption. Even though the energy reductions are very large, it is safe to say that a 20% minimum reduction would be achieved in any future installations of this technology.

  17. Pore Distribution Characteristics of the Igneous Reservoirs in the Eastern Sag of the Liaohe Depression

    OpenAIRE

    Zongli Liu; Zhuwen Wang; Dapeng Zhou; Shuqin Zhao; Min Xiang

    2017-01-01

    In the Es3 formation (third section of the Shahejie) of the Eastern sag section of the Liaohe Depression, basalt and trachyte are predominant in the igneous rock. The reservoir consists of complex reservoir space types. Based on the porosity bins of nuclear magnetic logging and the porosity distribution of electric imaging logging, the pores’ sizes and distribution, as well as the mutual connectivity of the reservoir, were analyzed. Also, the characteristics of the different reservoirs were s...

  18. Reactive Power Control of Single-Stage Three-Phase Photovoltaic System during Grid Faults Using Recurrent Fuzzy Cerebellar Model Articulation Neural Network

    OpenAIRE

    Faa-Jeng Lin; Kuang-Chin Lu; Hsuan-Yu Lee

    2014-01-01

    This study presents a new active and reactive power control scheme for a single-stage three-phase grid-connected photovoltaic (PV) system during grid faults. The presented PV system utilizes a single-stage three-phase current-controlled voltage-source inverter to achieve the maximum power point tracking (MPPT) control of the PV panel with the function of low voltage ride through (LVRT). Moreover, a formula based on positive sequence voltage for evaluating the percentage of voltage sag is deri...

  19. Deriving Sight Distance on a Compound Sag and Circular Curve in a Three Dimensional Space

    Directory of Open Access Journals (Sweden)

    Chiu Liu, PhD, PE, PTOE

    2012-09-01

    Full Text Available Insufficient roadway sight distance (SD may become a contribution factor to traffic collisions or other unsafe traffic maneuvers. The sight distance (SD for a two-dimensional (2-d sag or circular curve has been addressed in detail in various traffic engineering literatures. Although three-dimensional (3-d compound sag and circular curves are often found along ramps, connectors, and mountain roads, the sight distances for these compound curves are yet to be analyzed on an exact analytic setting. By considering human-vehicle-roadway interaction, the formulas for computing the SD on a 3-d curve are derived the first time on a unified analytic framework. The 2-d sag curve SD can also be deduced from these derived formulas as special limiting cases. Practitioners can easily program these formulas or equations on a user-friendly Microsoft Excel spread sheet to calculate 3-d SD on most roadways with roadside clearance. This framework can be extended to estimate SD on roadways with obstacles partially blocking vehicle headlight beams. 6.

  20. Thermomagnetic properties of peat-soil layers from Sag pond near Lembang Fault, West Java, Indonesia

    Science.gov (United States)

    Iryanti, Mimin; Wibowo, Dimas Maulana; Bijaksana, Satria

    2015-09-01

    Sag pond is a body of water near fault system as water flows blocked by the fault. Sag pond is a special type of environment for peat formation as peat layers in were deposited as the fault moves in episodic fashion. Depending on the history of the fault, peat layers are often interrupted by soil layers. In this study, core of peat-soil layers from a Sag pond in Karyawangi Village near Lembang Fault was obtained and analyzed for its magnetic properties. The 5 m core was obtained using a hand auger. Individual samples were obtained every cm and measured for their magnetic susceptibility. In general, there are three distinct magnetic susceptibility layers that were associated with peat and soil layers. The upper first 1 m is unconsolidated mud layer with its relatively high magnetic susceptibility. Between 1-2.81 m, there is consolidated mud layer and the lowest part (2.82-5) m is basically peat layer. Six samples were then measured for their thermomagnetic properties by measuring their susceptibility during heating and cooling from room temperature to 700°C. The thermomagnetic profiles provide Curie temperatures for various magnetic minerals in the cores. It was found that the upper part (unconsolidated mud) contains predominantly iron-oxides, such as magnetite while the lowest part (peat layer) contains significant amount of iron-sulphides, presumably greigite.

  1. The sagging rope sign in achondroplasia - different from Perthes' disease

    Energy Technology Data Exchange (ETDEWEB)

    Shingade, Viraj U. [Korea University, Department of Paediatric Orthopaedics, College of Medicine, Guro Hospital, Seoul (Korea); Song, Hae-Ryong [Korea University, Department of Paediatric Orthopaedic Surgery, College of Medicine, Guro Hospital, Seoul (Korea); Lee, Seok-Hyun; Suh, Seung-Woo [Korea University, Department of Orthopaedic Surgery, College of Medicine, Guro Hospital, Seoul (Korea); Oh, Chang-Wug [Kyungpook National University Hospital, Department of Orthopaedic Surgery, Daegu (Korea); Hong, Jun-Seok [Ansan Hospital, Department of Orthopaedic Surgery, Korea University, Ansan, Gyeonggi do (Korea)

    2006-12-15

    The sagging rope sign is a radio-opaque line, seen on radiographs of the hips, with Perthes' disease. The main purpose of this study was to determine the incidence, cause and importance of this sign in achondroplasia, and to reveal how it differs from in Perthes' disease. Serial radiograms, along with 2-dimensional and 3-dimensional CT images were studied in 42 achondroplasic patients. Forty-two achondroplasic patients, reported at our institute (for routine outpatient consultation, spine surgeries, deformity corrections, limb-lengthening procedures) were included in this study. There were 26 males and 16 females. The sign was observed bilaterally, in all patients. Evaluation of CT images revealed spherical heads, with presence of circumferential overhang in all hips. This circumferential overhang, seen on 3-D CT scan, corresponded to the sagging rope sign on radiographs. Presence of the sagging rope sign in bilateral hips is a characteristic feature of achondroplasia. It usually appears before epiphyseal closure. Its cause, incidence, and nature differ from Perthes' disease, and its presence does not carry a bad prognosis in achondroplasia. (orig.)

  2. A new trivalent SnSAG surface antigen chimera for efficient detection of antibodies against Sarcocystis neurona and diagnosis of equine protozoal myeloencephalitis.

    Science.gov (United States)

    Yeargan, Michelle; de Assis Rocha, Izabela; Morrow, Jennifer; Graves, Amy; Reed, Stephen M; Howe, Daniel K

    2015-05-01

    Enzyme-linked immunosorbent assays (ELISAs) based on the SnSAG surface antigens of Sarcocystis neurona provide reliable detection of infection by the parasite. Moreover, accurate serodiagnosis of equine protozoal myeloencephalitis (EPM) is achieved with the SnSAG ELISAs by measuring antibodies in serum and cerebrospinal fluid (CSF) to reveal active infection in the central nervous system. Two independent ELISAs based on recombinant (r)SnSAG2 or a chimeric fusion of SnSAG3 and SnSAG4 (rSnSAG4/3) are currently used together for EPM serodiagnosis to overcome varied antibody responses in different horses. To achieve reliable antibody detection with a single ELISA instead of 2 separate ELISAs, rSnSAG2 was fused with rSnSAG4/3 into a single trivalent protein, designated rSnSAG2/4/3. Paired serum and CSF from 163 horses were tested with all 3 ELISAs. When the consensus antibody titers obtained with the rSnSAG2 and rSnSAG4/3 ELISAs were compared to the single SAG2/4/3 ELISA titers, Spearman rank correlation coefficients of ρ = 0.74 and ρ = 0.90 were obtained for serum and CSF, respectively, indicating strong agreement between the tests. When the rSnSAG2 and rSnSAG4/3 consensus serum-to-CSF titer ratio was compared to the rSnSAG2/4/3 serum-to-CSF titer ratio, the Spearman correlation coefficient was ρ = 0.87, again signifying strong agreement. Importantly, comparing the diagnostic interpretation of the serum-to-CSF titer ratios yielded a Cohen kappa value of 0.77. These findings suggest that the single ELISA based on the trivalent rSnSAG2/4/3 will provide serologic and diagnostic results that are highly comparable to the consensus of the 2 independent ELISAs based on rSnSAG2 and rSnSAG4/3. © 2015 The Author(s).

  3. Toxoplasma gondii antigen SAG2A differentially modulates IL-1β expression in resistant and susceptible murine peritoneal cells.

    Science.gov (United States)

    Leal-Sena, Jamilly Azevedo; Dos Santos, Jane Lima; Dos Santos, Thaise Anne Rocha; de Andrade, Edson Mário; de Oliveira Mendes, Tiago Antônio; Santana, Juliano Oliveira; Mineo, Tiago Wilson Patriarca; Mineo, José Roberto; da Cunha-Júnior, Jair Pereira; Pirovani, Carlos Priminho

    2018-03-01

    The cell surface of Toxoplasma gondii is covered by antigens (SAGs) from the SRS family anchored by glycosylphosphatidylinositol (GPI) and includes antigens from the SAG2 family. Among these, the SAG2A surface antigen shows great potential in activating humoral responses and has been used in characterizing the acute phase of infection and in the serological diagnosis of toxoplasmosis. In this study, we aimed to evaluate rSAG2A-induced proteins in BALB/c and C57BL/c mice macrophages and to evaluate the phenotypic polarization induced in the process. We treated the peritoneal macrophages from mouse strains that were resistant or susceptible to T. gondii with rSAG2A to analyze their proteomic profile by mass spectrometry and systems biology. We also examined the gene expression of these cells by RT-qPCR using the phenotypic markers of M1 and M2 macrophages. Differences were observed in the expression of proteins involved in the inflammatory process in both resistant and susceptible cells, and macrophages were preferentially induced to obtain a pro-inflammatory immune response (M1) via the overexpression of IL-1β in mice susceptible to this parasite. These data suggest that the SAG2A antigen induces phenotypic and classical activation of macrophages in both resistant and susceptible strains of mice during the acute phase of the disease.

  4. Advanced DVR with Zero-Sequence Voltage Component and Voltage Harmonic Elimination for Three-Phase Three-Wire Distribution Systems

    Directory of Open Access Journals (Sweden)

    Margo P

    2009-11-01

    Full Text Available Dynamic Voltage Restorer (DVR is a power electronics device to protect sensitive load when voltage sag occurs. Commonly, sensitive loads are electronic-based devices which generate harmonics. The magnitude and phase of compensated voltage in DVR depend on grounding system and type of fault. If the system is floating, the zero sequence components do not appear on the load side. Meanwhile, in a neutral grounded system, voltage sag is extremely affected by zero sequence components. A blocking transformer is commonly installed in series with DVR to reduce the effect of zero sequence components. This paper proposes a new DVR control scheme that is capable of eliminating the blocking transformer and reducing harmonic distortion. The system uses fuzzy polar controller to replace the conventional PI or FL controller that is commonly used. By taking into account the zero sequence components in the controller design, the effects of zero sequence components can be compensated. Simulated results show the effectiveness of the proposed DVR controller

  5. Relevance of the directionality of skin elasticity to aging and sagging of the face.

    Science.gov (United States)

    Ohshima, Hiroshi; Tada, Akihiro; Kanamaru, Akiko; Akamatsu, Hisashi; Sakai, Yuji; Itoh, Masatoshi; Kanto, Hiromi

    2011-02-01

    Forces acting in facial skin have been suggested to show directionality. Non-invasive methods of measuring this directionality may thus provide information related to aging processes. The Reviscometer(®) RVM600 device is capable of measuring directionality of forces on the skin. This device has not been used previously in a published study to evaluate changes in directionality of forces on facial skin with aging. The first objective of this pilot study was to investigate relationships between mechanical directionality using the Reviscometer(®) RVM600, the Cutometer(®) MPA580, and aging of the facial skin in a supine position. In addition, the study investigated relationships between mechanical directionality and 'skin sagging,' which may be caused by gravity. To validate this as a new measurement of mechanical directionality, we also performed double-blinded trials on two groups of subjects, with one group using a product containing an anti-aging substance and the other group using a placebo product without an anti-aging substance. We examined 91 healthy Japanese women with a mean age of 48.5 years (range, 20-79 years) at the three sites on the face using the Reviscometer(®) RVM600 and the Cutometer(®) MPA580, and evaluation was performed for skin sagging in September and November 2008, and January 2009. The Reviscometer(®) RVM600 was used to measure resonance-running time (RRT) every 10° from 0° to 350°. Evaluation of skin sagging was undertaken by making marks on the face and using face photographs taken in both sitting and supine positions to calculate the sagging index. Usage testing was conducted on 38 healthy Japanese women in a double-blinded study with one group, using a preparation containing Yomogi AGEs Clearing (YAC) extract and another group using the same preparation without the YAC extract from October 2008 to April 2009. Mean age of these subjects was 44.0 years (range, 30-60 years). Measurements were taken at the three sites on the face

  6. A dulal-functional medium voltage level DVR to limit downstream fault currents

    DEFF Research Database (Denmark)

    Blaabjerg, Frede; Li, Yun Wei; Vilathgamuwa, D. Mahinda

    2007-01-01

    on the other parallel feeders connected to PCC. Furthermore, if not controlled properly, the DVR might also contribute to this PCC voltage sag in the process of compensating the missing voltage, thus further worsening the fault situation. To limit the flow of large line currents, and therefore restore the PCC......, the DVR will therefore be tasked to mitigate even more faults involving downstream loads. Large fault currents would flow through the DVR during a downstream fault before the opening of a circuit breaker. This will cause the voltage at point of common coupling (PCC) to drop, which would affect the loads...... voltage as well as protect the DVR system components, a downstream fault limiting function is proposed and integrated in the DVR operation. A flux-charge-model feedback algorithm is implemented so that the DVR would act as a large virtual inductance in series with the distribution feeder in fault...

  7. Detecting Power Voltage Dips using Tracking Filters - A Comparison against Kalman

    Directory of Open Access Journals (Sweden)

    STANCIU, I.-R.

    2012-11-01

    Full Text Available Due of its significant economical impact, Power-Quality (PQ analysis is an important domain today. Severe voltage distortions affect the consumers and disturb their activity. They may be caused by short circuits (in this case the voltage drops significantly or by varying loads (with a smaller drop. These two types are the PQ currently issues. Monitoring these phenomena (called dips or sags require powerful techniques. Digital Signal Processing (DSP algorithms are currently employed to fulfill this task. Discrete Wavelet Transforms, (and variants, Kalman filters, and S-Transform are currently proposed by researchers to detect voltage dips. This paper introduces and examines a new tool to detect voltage dips: the so-called tracking filters. Discovered and tested during the cold war, they can estimate a parameter of interest one-step-ahead based on the previously observed values. Two filters are implemented. Their performance is assessed by comparison against the Kalman filter?s results.

  8. Control Method Stretches Suspensions by Measuring the Sag of Strands in Cable-Stayed Bridges

    Science.gov (United States)

    Bętkowski, Piotr

    2017-10-01

    In the article is described the method that allows on evaluation and validation of measurement correctness of dynamometers (strain gauges, tension meters) used in systems of suspensions. Control of monitoring devices such as dynamometers is recommended in inspections of suspension bridges. Control device (dynamometer) works with an anchor, and the degree of this cooperation could have a decisive impact on the correctness of the results. Method, which determines the stress in the strand (cable), depending on the sag of stayed cable, is described. This method can be used to control the accuracy of measuring devices directly on the bridge. By measuring the strand sag, it is possible to obtain information about the strength (force) which occurred in the suspension cable. Digital camera is used for the measurement of cable sag. Control measurement should be made independently from the controlled parameter but should verify this parameter directly (it is the best situation). In many cases in practice the controlled parameter is not designation by direct measurement, but the calculations, i.e. relation measured others parameters, as in the method described in the article. In such cases occurred the problem of overlapping error of measurement of intermediate parameters (data) and the evaluation of the reliability of the results. Method of control calculations made in relation to installed in the bridge measuring devices is doubtful without procedure of uncertainty estimation. Such an assessment of the accuracy can be performed using the interval numbers. With the interval numbers are possible the analysis of parametric relationship accuracy of the designation of individual parameters and uncertainty of results. Method of measurements, relations and analytical formulas, and numerical example can be found in the text of the article.

  9. Continentward-dipping detachment fault system and asymmetric rift structure of the Baiyun Sag, northern South China Sea

    Science.gov (United States)

    Zhou, Zhichao; Mei, Lianfu; Liu, Jun; Zheng, Jinyun; Chen, Liang; Hao, Shihao

    2018-02-01

    The rift architecture and deep crustal structure of the distal margin at the mid-northern margin of the South China Sea have been previously investigated by using deep seismic reflection profiles. However, one fundamental recurring problem in the debate is the extensional fault system and rift structure of the hyperextended rift basins (Baiyun Sag and Liwan Sag) within the distal margin because of the limited amount of seismic data. Based on new 3D seismic survey data and 2D seismic reflection profiles, we observe an array of fault blocks in the Baiyun Sag, which were tilted towards the ocean by extensional faulting. The extensional faults consistently dip towards the continent. Beneath the tilted fault blocks and extensional faults, a low-angle, high-amplitude and continuous reflection has been interpreted as the master detachment surface that controls the extension process. During rifting, the continentward-dipping normal faults evolved in a sequence from south to north, generating the asymmetric rift structure of the Baiyun Sag. The Baiyun Sag is separated from the oceanic domain by a series of structural highs that were uplifted by magmatic activity in response to the continental breakup at 33 Ma and a ridge jump to the south at 26-24 Ma. Therefore, we propose that magmatism played a significant role in the continental extension and final breakup in the South China Sea.

  10. Toxoplasmose em sagüi-de-bigode (Saguinus imperator: relato de caso

    Directory of Open Access Journals (Sweden)

    Sabrina Epiphanio

    1999-01-01

    Full Text Available É relatado um caso de toxoplasmose ocorrido em sagüi-de-bigode (Saguinus imperator. O animal foi encontrado morto sem que tenham sido observados sinais clínicos. Achados de necropsia e histopatológicos incluíram pneumonia intersticial moderada, hepatite necrótica multifocal e linfadenite necrosante multifocal a coalescente. A técnica imunoistoquímica (strepto-avidina-biotina peroxidase realizada em pulmão, fígado, linfonodos, baço, coração, intestino e tecido adiposo foi fortemente positiva para Toxoplasma gondii.

  11. Sagging Skin

    Science.gov (United States)

    ... Hands Age Spots Aging Skin Birthmarks Burn Scars Cellulite Crow's Feet Droopy Eyelids Excess Fat Excessive Sweating ... Hands Age Spots Aging Skin Birthmarks Burn Scars Cellulite Crow's Feet Droopy Eyelids Excess Fat Excessive Sweating ...

  12. Safety, efficacy and immunogenicity evaluation of the SAG2 oral rabies vaccine in Formosan ferret badgers.

    Science.gov (United States)

    Hsu, Ai-Ping; Tseng, Chun-Hsien; Barrat, Jacques; Lee, Shu-Hwae; Shih, Yu-Hua; Wasniewski, Marine; Mähl, Philippe; Chang, Chia-Chia; Lin, Chun-Ta; Chen, Re-Shang; Tu, Wen-Jane; Cliquet, Florence; Tsai, Hsiang-Jung

    2017-01-01

    Since 2013, rabies cases have been reported among Formosan ferret badgers in Taiwan, and they have been shown to be the major reservoirs for Taiwanese enzootics. To control and eradicate rabies, the authorities plan to implement a vaccination programme. Before distributing live vaccines in the field, this study assessed the safety, efficacy, and immunogenicity of SAG2 vaccine on ferret badgers by direct oral instillation. After application of 109 TCID50/dose, no virus was excreted into the oral cavity 1-7 days post-application, and safety was also satisfactorily verified over a 266-day period. Moreover, despite the low level of rabies virus neutralising antibodies induced after vaccination of a 108 TCID50/dose, the efficacy assessment revealed a 100% survival rate (15/15) of vaccinees and an 87.5% fatality rate (7/8) in control animals after a challenge on the 198th day post-vaccination. The immunisation and protection rates obtained more than 6 months after a single vaccination dose demonstrated that SAG2 is an ideal vaccine candidate to protect Formosan ferret badgers against rabies in Taiwan.

  13. Over-Expression of Cysteine Leucine Rich Protein Is Related to SAG Resistance in Clinical Isolates of Leishmania donovani.

    Directory of Open Access Journals (Sweden)

    Sanchita Das

    2015-08-01

    Full Text Available Resistance emergence against antileishmanial drugs, particularly Sodium Antimony Gluconate (SAG has severely hampered the therapeutic strategy against visceral leishmaniasis, the mechanism of resistance being indistinguishable. Cysteine leucine rich protein (CLrP, was recognized as one of the overexpressed proteins in resistant isolates, as observed in differential proteomics between sensitive and resistant isolates of L. donovani. The present study deals with the characterization of CLrP and for its possible connection with SAG resistance.In pursuance of deciphering the role of CLrP in SAG resistance, gene was cloned, over-expressed in E. coli system and thereafter antibody was raised. The expression profile of CLrP and was found to be over-expressed in SAG resistant clinical isolates of L. donovani as compared to SAG sensitive ones when investigated by real-time PCR and western blotting. CLrP has been characterized through bioinformatics, immunoblotting and immunolocalization analysis, which reveals its post-translational modification along with its dual existence in the nucleus as well as in the membrane of the parasite. Further investigation using a ChIP assay confirmed its DNA binding potential. Over-expression of CLrP in sensitive isolate of L. donovani significantly decreased its responsiveness to SAG (SbV and SbIII and a shift towards the resistant mode was observed. Further, a significant increase in its infectivity in murine macrophages has been observed.The study reports the differential expression of CLrP in SAG sensitive and resistant isolates of L. donovani. Functional intricacy of CLrP increases with dual localization, glycosylation and DNA binding potential of the protein. Further over-expressing CLrP in sensitive isolate of L. donovani shows significantly decreased sensitivity towards SAG and increased infectivity as well, thus assisting the parasite in securing a safe niche. Results indicates the possible contribution of CLr

  14. Effect of codon optimization and subcellular targeting on Toxoplasma gondii antigen SAG1 expression in tobacco leaves to use in subcutaneous and oral immunization in mice

    Directory of Open Access Journals (Sweden)

    Yacono María L

    2010-07-01

    Full Text Available Abstract Background Codon optimization and subcellular targeting were studied with the aim to increase the expression levels of the SAG178-322 antigen of Toxoplasma gondii in tobacco leaves. The expression of the tobacco-optimized and native versions of the SAG1 gene was explored by transient expression from the Agrobacterium tumefaciens binary expression vector, which allows targeting the recombinant protein to the endoplasmic reticulum (ER and the apoplast. Finally, mice were subcutaneously and orally immunized with leaf extracts-SAG1 and the strategy of prime boost with rSAG1 expressed in Escherichia coli was used to optimize the oral immunization with leaf extracts-SAG1. Results Leaves agroinfiltrated with an unmodified SAG1 gene accumulated 5- to 10-fold more than leaves agroinfiltrated with a codon-optimized SAG1 gene. ER localization allowed the accumulation of higher levels of native SAG1. However, no significant differences were observed between the mRNA accumulations of the different versions of SAG1. Subcutaneous immunization with leaf extracts-SAG1 (SAG1 protected mice against an oral challenge with a non-lethal cyst dose, and this effect could be associated with the secretion of significant levels of IFN-γ. The protection was increased when mice were ID boosted with rSAG1 (SAG1+boost. This group elicited a significant Th1 humoral and cellular immune response characterized by high levels of IFN-γ. In an oral immunization assay, the SAG1+boost group showed a significantly lower brain cyst burden compared to the rest of the groups. Conclusion Transient agroinfiltration was useful for the expression of all of the recombinant proteins tested. Our results support the usefulness of endoplasmic reticulum signal peptides in enhancing the production of recombinant proteins meant for use as vaccines. The results showed that this plant-produced protein has potential for use as vaccine and provides a potential means for protecting humans and

  15. A Dynamic Voltage Restorer based on Matrix Converter with Fuzzy Controller

    Directory of Open Access Journals (Sweden)

    Amin Shabanpour

    2012-01-01

    Full Text Available In this paper, a Dynamic Voltage Restorer (DVR without any energy storage devices is proposed to compensate network voltage during disturbances. This DVR utilizes a matrix converter in its topology which eliminates the DC-link capacitor of conventional DVR. The modulation method for matrix converter which is used in this paper is indirect space vector modulation. A fuzzy PI controller is proposed instead of conventional PI controllers. The proposed topology is able to compensate balanced sags/swells as well as unbalanced ones. Moreover it can compensate harmonic pollution of the input source. The simulation results in MATLAB/Simulink environment show that the proposed DVR operates well during different disturbances and it has the ability to control the sensitive load voltage.

  16. Comparison of the effects of SAG-M and whole-blood transfusions on postoperative suppression of delayed hypersensitivity

    DEFF Research Database (Denmark)

    Nielsen, Hans Jørgen; Hammer, J H; Moesgaard, F

    1991-01-01

    The influence of perioperative whole-blood transfusion and transfusion with erythrocyte suspension (SAG-M blood) on postoperative depression of cell-mediated immunity (CMI) was investigated in 67 patients who underwent elective resection for colorectal cancer. Cell-mediated immunity was assessed ...

  17. Complete protection against lethal Toxoplasma gondii infection in mice immunized with a plasmid encoding the SAG1 gene

    DEFF Research Database (Denmark)

    Nielsen, H V; Lauemøller, S L; Christiansen, L

    1999-01-01

    Infection with the protozoan parasite Toxoplasma gondii is transmitted to humans from infected animals by tissue cysts and oocysts excreted by cats. Immunization with inactivated parasites or recombinant proteins has at best shown partial protection. We constructed a plasmid expressing the SAG1...

  18. Semi-Active Control of Three-Dimensional Vibrations of an Inclined Sag Cable with Magnetorheological Dampers

    DEFF Research Database (Denmark)

    Zhou, Q.; Nielsen, Søren R.K.; Qu, W. L.

    2006-01-01

    Three-dimensional semi-active vibration control of an inclined sag cable with discrete magnetorheological (MR) dampers is investigated in this paper using the finite difference method (FDM). A modified Dahl model is used to describe the dynamic property of MR damper. The nonlinear equations of mo...

  19. Glutenite bodies sequence division of the upper Es4 in northern Minfeng zone of Dongying Sag, Bohai Bay Basin, China

    Science.gov (United States)

    Shao, Xupeng

    2017-04-01

    Glutenite bodies are widely developed in northern Minfeng zone of Dongying Sag. Their litho-electric relationship is not clear. In addition, as the conventional sequence stratigraphic research method drawbacks of involving too many subjective human factors, it has limited deepening of the regional sequence stratigraphic research. The wavelet transform technique based on logging data and the time-frequency analysis technique based on seismic data have advantages of dividing sequence stratigraphy quantitatively comparing with the conventional methods. Under the basis of the conventional sequence research method, this paper used the above techniques to divide the fourth-order sequence of the upper Es4 in northern Minfeng zone of Dongying Sag. The research shows that the wavelet transform technique based on logging data and the time-frequency analysis technique based on seismic data are essentially consistent, both of which divide sequence stratigraphy quantitatively in the frequency domain; wavelet transform technique has high resolutions. It is suitable for areas with wells. The seismic time-frequency analysis technique has wide applicability, but a low resolution. Both of the techniques should be combined; the upper Es4 in northern Minfeng zone of Dongying Sag is a complete set of third-order sequence, which can be further subdivided into 5 fourth-order sequences that has the depositional characteristics of fine-upward sequence in granularity. Key words: Dongying sag, northern Minfeng zone, wavelet transform technique, time-frequency analysis technique ,the upper Es4, sequence stratigraphy

  20. Geometry and Evolution of the Cangdong Sag in the Bohai Bay Basin, China: Implications for Subduction of the Pacific Plate.

    Science.gov (United States)

    Luo, Liang; Qi, Jiafu; Li, Hongxiang; Dong, Yueqi; Zhang, Shuai; Zhang, Xichen; Yu, Xiaoxia; Luo, Lingyan

    2017-11-13

    The Cangdong Sag is a complex Cenozoic rift basin at the center of the Bohai Bay Basin. Cenozoic structures in the Cangdong Sag can be subdivided into the Cangdong Fault System in the west and the Xuxi Fault System in the east. The geometry of the boundary faults varies along the axes of half-grabens. According to the cross-sectional strata geometry, unconformity and planar structural pattern, the Cenozoic structural evolution of the Cangdong Sag can be divided into four distinct stages: (1) major Paleocene initial rift, (2) latest Paleocene-early Eocene intensive rift, (3) late Eocene-Oligocene strike-slip superimposed rift, and (4) Neogene to present-day post-rift depression. The extensional deformation was mainly derived from horizontal stress induced by the upwelling of asthenosphere. The strike-slip structure of the Cangdong Sag provides important information related to the subduction of the Western Pacific Plate. It was found that the strike-slip movement of the southern Xuxi Fault Zone was activated during the deposition of the third member of Shahejie Formation to the Dongying Formation; therefore, ~43 Ma probably marks the time when the Western Pacific Plate initially changed its subduction direction from northwest to nearly west.

  1. Distinct SagA from Hospital-Associated Clade A1 Enterococcus faecium Strains Contributes to Biofilm Formation.

    Science.gov (United States)

    Paganelli, F L; de Been, M; Braat, J C; Hoogenboezem, T; Vink, C; Bayjanov, J; Rogers, M R C; Huebner, J; Bonten, M J M; Willems, R J L; Leavis, H L

    2015-10-01

    Enterococcus faecium is an important nosocomial pathogen causing biofilm-mediated infections. Elucidation of E. faecium biofilm pathogenesis is pivotal for the development of new strategies to treat these infections. In several bacteria, extracellular DNA (eDNA) and proteins act as matrix components contributing to biofilm development. In this study, we investigated biofilm formation capacity and the roles of eDNA and secreted proteins for 83 E. faecium strains with different phylogenetic origins that clustered in clade A1 and clade B. Although there was no significant difference in biofilm formation between E. faecium strains from these two clades, the addition of DNase I or proteinase K to biofilms demonstrated that eDNA is essential for biofilm formation in most E. faecium strains, whereas proteolysis impacted primarily biofilms of E. faecium clade A1 strains. Secreted antigen A (SagA) was the most abundant protein in biofilms from E. faecium clade A1 and B strains, although its localization differed between the two groups. sagA was present in all sequenced E. faecium strains, with a consistent difference in the repeat region between the clades, which correlated with the susceptibility of biofilms to proteinase K. This indicates an association between the SagA variable repeat profile and the localization and contribution of SagA in E. faecium biofilms. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  2. Development of a Voltage Compensation Type Active SFCL and Its Application for Transient Performance Enhancement of a PMSG-Based Wind Turbine System

    Directory of Open Access Journals (Sweden)

    Lei Chen

    2017-01-01

    Full Text Available Considering the rapid development of high temperature superconducting (HTS materials, superconducting power applications have attracted more and more attention in the power industry, particularly for electrical systems including renewable energy. This paper conducts experimental tests on a voltage compensation type active superconducting fault current limiter (SFCL prototype and explores the SFCL’s application in a permanent-magnet synchronous generator- (PMSG- based wind turbine system. The SFCL prototype is composed of a three-phase air-core superconducting transformer and a voltage source converter (VSC integrated with supercapacitor energy storage. According to the commissioning test and the current-limiting test, the SFCL prototype can automatically suppress the fault current and offer a highly controlled compensation voltage in series with the 132 V electrical test system. To expand the application of the active SFCL in a 10 kW class PMSG-based wind turbine system, digital simulations under different fault cases are performed in MATLAB/Simulink. From the demonstrated simulation results, using the active SFCL can help to maintain the power balance, mitigate the voltage-current fluctuation, and improve the wind energy efficiency. The active SFCL can be regarded as a feasible solution to assist the PMSG-based wind turbine system to achieve low-voltage ride-through (LVRT operation.

  3. Super and Combinatorial Harmonic Response of Flexible Elastic Cables with Small Sag

    DEFF Research Database (Denmark)

    Nielsen, Søren R. K.; Kirkegaard, Poul Henning

    2002-01-01

    The paper deals with the analysis of cables in stayed bridges and TV-towers, where the excitation is caused by harmonically varying in-plane motions of the upper support point with the amplitude ;. Such cables are characterized by a sag-to-chord-length ratio below 0·02, which means that the lowest...... circular eigenfrequencies for in-plane and out-of-plane eigenvibrations, ω and ω, are closely separated. The dynamic analysis is performed by a two-degree-of-freedom modal decomposition in the lowest in-plane and out-of-plane eigenmodes. Modal parameters are evaluated based on the eigenmodes...... for the parabolic approximation to the equilibrium suspension....

  4. Sag Compensation System for Assembly of MDT-Chambers for the ATLAS Experiment

    CERN Document Server

    Barashkou, A V; Chepurnov, V F; Evtoukhovitch, P G; Glonti, G L; Gongadze, A L; Ilyushenka, Y N; Kotov, S A; Kruchonak, V G; Tskhadadze, E G

    2005-01-01

    The description of a system of the devices created for compensation of the gravitational deflection of the drift chamber during its assembly is presented. By means of this system during stage-by-stage gluing of layers of tube drift detectors to the chamber the transversal deflection considerably decreases and by that high accuracy of mutual position of separate tubes is provided. The devices were applied at assembly of 74 MDT-chambers of the ATLAS experiment. Design values of deformation of the chambers as well as the results of measurement of transversal deflections obtained during the assembly with the use of the system of sag compensation are given. Testing of chambers on the X-ray tomograph at CERN has shown that the accuracy of the positions of separate signal wires inside the assembled chambers is within the limits of the required 20 $\\mu$m.

  5. Pore Distribution Characteristics of the Igneous Reservoirs in the Eastern Sag of the Liaohe Depression

    Science.gov (United States)

    Zongli, Liu; Zhuwen, Wang; Dapeng, Zhou; Shuqin, Zhao; Min, Xiang

    2017-05-01

    In the Es3 formation (third section of the Shahejie) of the Eastern sag section of the Liaohe Depression, basalt and trachyte are predominant in the igneous rock. The reservoir consists of complex reservoir space types. Based on the porosity bins of nuclear magnetic logging and the porosity distribution of electric imaging logging, the pores' sizes and distribution, as well as the mutual connectivity of the reservoir, were analyzed. Also, the characteristics of the different reservoirs were summarized. In regards to the oil reservoirs, large pores (PS>10) were found to account for the majority of the reservoir spaces, and the pore distribution was concentrated and well connected. However, for the poor oil reservoirs, the large and small pores were found to alternate, and the pore distribution was scattered and poorly connected. Within the dry layers, the smaller pores (PS<10) were predominant. The pore distributions were found to be influenced by lithology, facies, and tectonism. The reservoirs of the pyroclastic flow of the explosive facies had good connectivity, and the interlayer heterogeneity was relatively weak. This reservoir's pore distributions were found to be mainly dominated by the larger pores (PS10-PS13), which displayed a concentrated distribution mainly in one porosity bin. Therefore, it was taken as a favorable facie belt in the eastern sag of the Liaohe Depression. The examination of the pore distribution characteristics of the igneous rock was the key to the evaluation of the properties and effectiveness of the igneous reservoirs in this study, which potentially has great significance to the future exploration and development of igneous rock.

  6. Pore Distribution Characteristics of the Igneous Reservoirs in the Eastern Sag of the Liaohe Depression

    Directory of Open Access Journals (Sweden)

    Zongli Liu

    2017-05-01

    Full Text Available In the Es3 formation (third section of the Shahejie of the Eastern sag section of the Liaohe Depression, basalt and trachyte are predominant in the igneous rock. The reservoir consists of complex reservoir space types. Based on the porosity bins of nuclear magnetic logging and the porosity distribution of electric imaging logging, the pores’ sizes and distribution, as well as the mutual connectivity of the reservoir, were analyzed. Also, the characteristics of the different reservoirs were summarized. In regards to the oil reservoirs, large pores (PS>10 were found to account for the majority of the reservoir spaces, and the pore distribution was concentrated and well connected. However, for the poor oil reservoirs, the large and small pores were found to alternate, and the pore distribution was scattered and poorly connected. Within the dry layers, the smaller pores (PS<10 were predominant. The pore distributions were found to be influenced by lithology, facies, and tectonism. The reservoirs of the pyroclastic flow of the explosive facies had good connectivity, and the interlayer heterogeneity was relatively weak. This reservoir’s pore distributions were found to be mainly dominated by the larger pores (PS10-PS13, which displayed a concentrated distribution mainly in one porosity bin. Therefore, it was taken as a favorable facie belt in the eastern sag of the Liaohe Depression. The examination of the pore distribution characteristics of the igneous rock was the key to the evaluation of the properties and effectiveness of the igneous reservoirs in this study, which potentially has great significance to the future exploration and development of igneous rock.

  7. Grid support capabilities of wind turbines

    DEFF Research Database (Denmark)

    Michalke, Gabriele; Hansen, Anca Daniela

    2013-01-01

    turbines, such as fault ride-through and reactive power supply during voltage sags. To date different wind turbine concepts exist on the market comprising different control features in order to provide ancillary services to the power system. In the first place the present chapter emphasizes the most...... important issues related to wind power grid integration. Then different wind turbine concepts are characterized and their grid support capabilities are analysed and compared. Simulation cases are presented in which the respective wind turbine concepts are subjected to a voltage dip specified in a grid code....

  8. Mapping of grid faults and grid codes

    DEFF Research Database (Denmark)

    Iov, F.; Hansen, Anca Daniela; Sørensen, Poul Ejnar

    for such investigations. The grid connection requirements for wind turbines have increased significantly during the last 5-10 years. Especially the requirements for wind turbines to stay connected to the grid during and after voltage sags, imply potential challenges in the design of wind turbines. These requirements pose......’ impact on the wind turbines’ lifetime are defined. The goal of this report is to present a mapping of different grid fault types and their frequency in different countries. The report provides also a detailed overview of the Low Voltage Ride-Through Capabilities for wind turbines in different relevant...

  9. Mapping of grid faults and grid codes

    DEFF Research Database (Denmark)

    Iov, Florin; Hansen, A.D.; Sørensen, P.

    for such investigations. The grid connection requirements for wind turbines have increased significantly during the last 5-10 years. Especially the requirements for wind turbines to stay connected to the grid during and after voltage sags, imply potential challenges in the design of wind turbines. These requirements pose......' impact on the wind turbines' lifetime are defined. The goal of this report is to present a mapping of different grid fault types and their frequency in different countries. The report provides also a detailed overview of the Low Voltage Ride-Through Capabilities for wind turbines in different relevant...

  10. Comprehensive analysis of the dynamic behavior of grid-connected DFIG-based wind turbines under LVRT conditions

    DEFF Research Database (Denmark)

    Alsmadi, Yazan M.; Xu, Longya; Blaabjerg, Frede

    2015-01-01

    presents a comprehensive study of the LVRT of grid-connected DFIG-based wind turbines. It provides a detailed investigation of the transient characteristics and the dynamic behavior of DFIGs during symmetrical and asymmetrical grid voltage sags. A detailed theoretical study supported by computer......Power generation and grid stability have become key issues in the last decade. The high penetration of large capacity wind generation into the electric power grid has led to serious concerns about their influence on the dynamic behavior of power systems. The Low-Voltage Ride-Through (LVRT...

  11. Instability of Wind Turbine Converters during Current Injection to Low Voltage Grid Faults and PLL Frequency Based Stability Solution

    DEFF Research Database (Denmark)

    Göksu, Ömer; Teodorescu, Remus; Bak, Claus Leth

    2014-01-01

    turbines lose synchronism with the grid fundamental frequency (e.g., 50 Hz) during very deep voltage sags, is explored with its theory, analyzed and a novel stability solution based on PLL frequency is proposed; and both are verified with power system simulations and by experiments on a grid......In recent grid codes for wind power integration, wind turbines are required to stay connected during grid faults even when the grid voltage drops down to zero; and also to inject reactive current in proportion to the voltage drop. However, a physical fact, instability of grid-connected converters...... during current injection to very low (close to zero) voltage faults, has been omitted, i.e., failed to be noticed in the previous wind power studies and grid code revisions. In this paper, the instability of grid side converters of wind turbines defined as loss of synchronism (LOS), where the wind...

  12. Technological Aspects: High Voltage

    CERN Document Server

    Faircloth, D.C.

    2013-12-16

    This paper covers the theory and technological aspects of high-voltage design for ion sources. Electric field strengths are critical to understanding high-voltage breakdown. The equations governing electric fields and the techniques to solve them are discussed. The fundamental physics of high-voltage breakdown and electrical discharges are outlined. Different types of electrical discharges are catalogued and their behaviour in environments ranging from air to vacuum are detailed. The importance of surfaces is discussed. The principles of designing electrodes and insulators are introduced. The use of high-voltage platforms and their relation to system design are discussed. The use of commercially available high-voltage technology such as connectors, feedthroughs and cables are considered. Different power supply technologies and their procurement are briefly outlined. High-voltage safety, electric shocks and system design rules are covered.

  13. High voltage test techniques

    CERN Document Server

    Kind, Dieter

    2001-01-01

    The second edition of High Voltage Test Techniques has been completely revised. The present revision takes into account the latest international developments in High Voltage and Measurement technology, making it an essential reference for engineers in the testing field.High Voltage Technology belongs to the traditional area of Electrical Engineering. However, this is not to say that the area has stood still. New insulating materials, computing methods and voltage levels repeatedly pose new problems or open up methods of solution; electromagnetic compatibility (EMC) or components and systems al

  14. High voltage engineering

    CERN Document Server

    Rizk, Farouk AM

    2014-01-01

    Inspired by a new revival of worldwide interest in extra-high-voltage (EHV) and ultra-high-voltage (UHV) transmission, High Voltage Engineering merges the latest research with the extensive experience of the best in the field to deliver a comprehensive treatment of electrical insulation systems for the next generation of utility engineers and electric power professionals. The book offers extensive coverage of the physical basis of high-voltage engineering, from insulation stress and strength to lightning attachment and protection and beyond. Presenting information critical to the design, selec

  15. Stray voltage mitigation

    Energy Technology Data Exchange (ETDEWEB)

    Jamali, B.; Piercy, R.; Dick, P. [Kinetrics Inc., Toronto, ON (Canada). Transmission and Distribution Technologies

    2008-04-09

    This report discussed issues related to farm stray voltage and evaluated mitigation strategies and costs for limiting voltage to farms. A 3-phase, 3-wire system with no neutral ground was used throughout North America before the 1930s. Transformers were connected phase to phase without any electrical connection between the primary and secondary sides of the transformers. Distribution voltage levels were then increased and multi-grounded neutral wires were added. The earth now forms a parallel return path for the neutral current that allows part of the neutral current to flow continuously through the earth. The arrangement is responsible for causing stray voltage. Stray voltage causes uneven milk production, increased incidences of mastitis, and can create a reluctance to drink water amongst cows when stray voltages are present. Off-farm sources of stray voltage include phase unbalances, undersized neutral wire, and high resistance splices on the neutral wire. Mitigation strategies for reducing stray voltage include phase balancing; conversion from single to 3-phase; increasing distribution voltage levels, and changing pole configurations. 22 refs., 5 tabs., 13 figs.

  16. Characterization of Tn5801.Sag, a variant of Staphylococcus aureus Tn916 family transposon Tn5801 that is widespread in clinical isolates of Streptococcus agalactiae.

    Science.gov (United States)

    Mingoia, Marina; Morici, Eleonora; Tili, Emily; Giovanetti, Eleonora; Montanari, Maria Pia; Varaldo, Pietro E

    2013-09-01

    Tn5801, originally detected in Staphylococcus aureus Mu50, is a Tn916 family element in which a unique int gene (int5801) replaces the int and xis genes in Tn916 (int916 and xis916). Among 62 tet(M)-positive tetracycline-resistant Streptococcus agalactiae isolates, 43 harbored Tn916, whereas 19 harbored a Tn5801-like element (Tn5801.Sag, ∼20.6 kb). Tn5801.Sag was characterized (PCR mapping, partial sequencing, and chromosomal integration) and compared to other Tn5801-like elements. Similar to Tn5801 from S. aureus Mu50, tested in parallel, Tn5801.Sag was unable to undergo circularization and conjugal transfer.

  17. Enzyme-linked immunosorbent assays using recombinant TgSAG2 and NcSAG1 to detect Toxoplasma gondii and Neospora caninum-specific antibodies in domestic animals in Turkey.

    Science.gov (United States)

    Zhou, Mo; Cao, Shinuo; Sevinc, Ferda; Sevinc, Mutlu; Ceylan, Onur; Liu, Mingming; Wang, Guanbo; Moumouni, Paul Franck Adjou; Jirapattharasate, Charoonluk; Suzuki, Hiroshi; Nishikawa, Yoshifumi; Xuan, Xuenan

    2017-01-10

    Considering the scarce information on occurrences of Toxoplasma gondii and Neospora caninum in domestic animals from Turkey, the aim of this study was to investigate the seroprevalence of these parasite infections in cattle, horses, sheep, goats and dogs in Turkey. The specific antibodies against T. gondii and N. caninum were detected by iELISAs based on the recombinant TgSAG2 or NcSAG1 in a total of 2,039 serum samples from eleven provinces. The seroprevalence of T. gondii infections was 46.3%, 4.0%, 20.0%, 12.9% and 19.8%, that of N. caninum infections was 0.3%, 7.4%, 2.1%, 3.2% and 16.6% in the horses, cattle, sheep, goats and dogs, respectively. These results indicated that T. gondii and N. caninum infections are prevalent in Turkish domestic animals.

  18. Voltage verification unit

    Science.gov (United States)

    Martin, Edward J [Virginia Beach, VA

    2008-01-15

    A voltage verification unit and method for determining the absence of potentially dangerous potentials within a power supply enclosure without Mode 2 work is disclosed. With this device and method, a qualified worker, following a relatively simple protocol that involves a function test (hot, cold, hot) of the voltage verification unit before Lock Out/Tag Out and, and once the Lock Out/Tag Out is completed, testing or "trying" by simply reading a display on the voltage verification unit can be accomplished without exposure of the operator to the interior of the voltage supply enclosure. According to a preferred embodiment, the voltage verification unit includes test leads to allow diagnostics with other meters, without the necessity of accessing potentially dangerous bus bars or the like.

  19. Feasibility and efficacy of oral rabies vaccine SAG2 in endangered Ethiopian wolves.

    Science.gov (United States)

    Sillero-Zubiri, Claudio; Marino, Jorgelina; Gordon, Christopher H; Bedin, Eric; Hussein, Alo; Regassa, Fekede; Banyard, Ashley; Fooks, Anthony R

    2016-09-14

    Diseases are a major cause of population declines in endangered populations of several canid species. Parenteral vaccination efforts to protect Ethiopian wolves (Canis simensis) from rabies have targeted the domestic dog reservoir, or the wolves themselves in response to confirmed outbreaks. Oral vaccination offers a more cost-efficient, safe and proactive approach to protect Ethiopian wolves and other threatened canids from rabies. Field trials of the oral vaccine Rabigen® SAG2Dog were undertaken in the Bale Mountains of southeastern Ethiopia. Four different bait types and three delivery methods were tested in twelve Ethiopian wolf packs, and the oral vaccine (using the preferred bait) was trialled in three packs. Vaccine uptake and immunization rates were measured through direct observations and in live-trapped animals through the assessment of biomarker levels and serological status. Commercial baits were never taken by wolves; goat meat baits had the highest uptake, compared to rodent and intestine baits. Targeted delivery from horseback and nocturnal delivery within a pack's territory performed favourably compared to random bait distribution. Bait uptake by non-target species was lowest during the nocturnal blind distribution. Of 21 wolves trapped after vaccination, 14 were positive for the biomarker iophenoxic acid (i.e. ingested the bait and most likely pierced the sachet with the vaccine). Of these, 86% (n=12/14) had levels considered sufficient to provide protective immunity to wildlife (⩾0.20IU/ml), and 50% (n=7/14) demonstrated antibody titres above the universally recognised threshold (⩾0.5IU/ml) -the baseline average was 0.09IU/ml (n=12 wolves). All but one of the wolves vaccinated in 2014 were alive 14months later. Our trials confirm the potential for SAG2, delivered in a goat meat bait, to effectively protect Ethiopian wolves against rabies, supporting the initiative for a more efficient and proactive approach to manage and eventually eliminate

  20. A modified SAG technique for the fabrication of DWDM DFB laser arrays with highly uniform wavelength spacings.

    Science.gov (United States)

    Zhang, Can; Liang, Song; Zhu, Hongliang; Wang, Baojun; Wang, Wei

    2012-12-31

    A modified selective area growth (SAG) technique, in which the effective index of only the upper separate confinement heterostructure (SCH) layer are modulated to obtain different emission wavelengths, is reported for the fabrication of dense wavelength division multiplexing (DWDM) multi-wavelength laser arrays (MWLAs). InP based 1.5 μm distributed feedback (DFB) laser arrays with 0.8 nm, 0.42 nm, and 0.19 nm channel separations are demonstrated, all showing highly uniform wavelength spacings. The standard deviation of the distribution of the wavelength residues with respect to the corresponding linear fitting values is 0.0672 nm, which is a lot smaller than those of the MWLAs fabricated by other techniques including electron beam lithography. These results indicate that our SAG technique which needs only a simple procedure is promising for the fabrication of low cost DWDM MWLAs.

  1. Comparison of the effects of SAG-M and whole-blood transfusions on postoperative suppression of delayed hypersensitivity

    DEFF Research Database (Denmark)

    Nielsen, Hans Jørgen; Hammer, J H; Moesgaard, F

    1991-01-01

    pre- and postoperatively by skin testing with seven common delayed-type hypersensitivity (DTH) antigens. The postoperative skin-test response decreased more in the patients who received whole blood (15 patients) than in those who received SAG-M blood (16 patients) (60% versus 42%, p less than 0......The influence of perioperative whole-blood transfusion and transfusion with erythrocyte suspension (SAG-M blood) on postoperative depression of cell-mediated immunity (CMI) was investigated in 67 patients who underwent elective resection for colorectal cancer. Cell-mediated immunity was assessed.......001) and in those who did not receive a blood transfusion (36 patients) (60% versus 40%, p less than 0.001). The enhanced postoperative immunosuppression in patients who received whole-blood transfusions persisted after matching according to age, sex, height, weight, hemoglobin and serum albumin levels, duration...

  2. Clash of symbols a ride through the riches of glyphs

    CERN Document Server

    Webb, Stephen

    2018-01-01

    From the ampersat and amerpsand, via smileys and runes to the ubiquitous presence of mathematical and other symbols in sciences and technology: both old and modern documents abound with many familiar as well as lesser known characters, symbols and other glyphs. Yet, who would be readily able to answer any question like: ‘who chose π to represent the ratio of a circle’s diameter to its circumference?’ or ‘what’s the reasoning behind having a ⌘ key on my computer keyboard?’  This book is precisely for those who have always asked themselves this sort of questions. So, here are the stories behind one hundred glyphs, the book being evenly divided into five parts, with each featuring 20 symbols. Part 1, called Character sketches, looks at some of the glyphs we use in writing. Part 2, called Signs of the times, discusses some glyphs used in pol­itics, religion, and other areas of everyday life. Some of these symbols are common; others are used only rarely. Some are modern inventions; others, which...

  3. Over-expression of 60s ribosomal L23a is associated with cellular proliferation in SAG resistant clinical isolates of Leishmania donovani.

    Directory of Open Access Journals (Sweden)

    Sanchita Das

    Full Text Available Sodium antimony gluconate (SAG unresponsiveness of Leishmania donovani (Ld had effectively compromised the chemotherapeutic potential of SAG. 60s ribosomal L23a (60sRL23a, identified as one of the over-expressed protein in different resistant strains of L.donovani as observed with differential proteomics studies indicates towards its possible involvement in SAG resistance in L.donovani. In the present study 60sRL23a has been characterized for its probable association with SAG resistance mechanism.The expression profile of 60s ribosomal L23a (60sRL23a was checked in different SAG resistant as well as sensitive strains of L.donovani clinical isolates by real-time PCR and western blotting and was found to be up-regulated in resistant strains. Ld60sRL23a was cloned, expressed in E.coli system and purified for raising antibody in swiss mice and was observed to have cytosolic localization in L.donovani. 60sRL23a was further over-expressed in sensitive strain of L.donovani to check its sensitivity profile against SAG (Sb V and III and was found to be altered towards the resistant mode.This study reports for the first time that the over expression of 60sRL23a in SAG sensitive parasite decreases the sensitivity of the parasite towards SAG, miltefosine and paramomycin. Growth curve of the tranfectants further indicated the proliferative potential of 60sRL23a assisting the parasite survival and reaffirming the extra ribosomal role of 60sRL23a. The study thus indicates towards the role of the protein in lowering and redistributing the drug pressure by increased proliferation of parasites and warrants further longitudinal study to understand the underlying mechanism.

  4. Tectono-sedimentary evolution of the deepwater sags in the Pearl River Mouth Basin (South China Sea)

    Science.gov (United States)

    Zhao, Fang; Xia, Shaohong; Sun, Jinlong; Xu, Huilong; Cao, Jinghe

    2017-04-01

    Regional (2D) seismic reflection profiles and borehole data are used to present the first comprehensive seismic-stratigraphic analysis of the deepwater sags in the Pearl River Mouth Basin, northern South China Sea (SCS). Three seismic-stratigraphic units were defined based on correlation between strata geometries and the continental rifting and breakup history of the northern South China margin. Unit 1 records syn-rift deposition that is associated with continental rifting of the SCS. On the basis of mapping seismic units we are able to identify three major phases of Cenozoic extension, each comprising distinct subsidence pulses separated by individual stratigraphic unconformity. The overlying Unit 2 is interpreted as the breakup sequences, probably recording the sedimentological changes during the continental breakup process of SCS. Multiple episodes of uplift and erosion, which generated substantial mass wasting into the Liwan Sag, occurred after the onset of continental breakup in the northern SCS. The most prominent uplifting and erosional events are the truncation related to the Early Miocene volcanism in the Baiyun Sag, uplift and erosion towards the southeast. Unit 3 records post-rift sedimentation and passive subsidence. Detailed seismic interpretation indicates that the post-rift succession is dominated by a complex of the downslope and alongslope processes.

  5. A Force Method Model for Dynamic Analysis of Flat-Sag Cable Structures

    Directory of Open Access Journals (Sweden)

    Xing Ma

    2009-01-01

    Full Text Available A new force method is proposed for analysing the dynamic behaviour of oscillating cables with small sags. The accepted dynamic model of such cables reduces to a partial differential equation (the equation of motion and an integral equation (the compatibility equation. In the paper, D’Alembert’s travelling wave solution is applied to the partial differential equation (PDE. Substituting the solution into the compatibility and boundary conditions, the governing equation is obtained in terms of the dynamic tension increment. This equation has been named the force method dynamic equation (FMDE. In this way the infinite-degree-of-freedom dynamic system is effectively simplified to a system with only one unknown. Explicit solutions for both single-span and multi-span cable systems are derived. The natural frequencies obtained from the FMDE are shown to be identical to those deduced using the conventional displacement method (DM. Nonlinear governing equations are developed by considering the effect of quadratic and cubic displacement terms. Finally, two examples are presented to illustrate the accuracy of the proposed force method for single and multi-span cable systems subjected to harmonic forces.

  6. Design of a MEMS Capacitive Comb-drive Micro-accelerometer with Sag Optimization

    Directory of Open Access Journals (Sweden)

    B. D. PANT

    2009-09-01

    Full Text Available The current paper presents an optimization study for the designing of a highly sensitive inertial grade capacitive accelerometer based on comb-drive actuation and sensing. The proof mass, suspension system (beams or tethers, stators and rotors have to be realized through an HAR (high aspect ratio DRIE (deep reactive ion etching process for which process optimization has already been done at our laboratory. As the proof mass is a bulk micro-machined structure having a mass in milligram range, the optimum positioning of the tethers on the proof mass is important to have minimum sag, necessary to reduce the off-axis sensitivity. The optimization for the positioning of the tethers has been carried out using a commercial software tool ANSYSTM Multiphysics. The accelerometer has been modeled analytically to predict its characteristics. The dependency of sensitivity on the dimensions of the suspension beams (tethers has also been verified using the above FEM software tool. The present device has been designed to deliver a high sensitivity of 13.6 mV/g/V for low-g applications.

  7. Design of a MEMS Capacitive Comb-drive Micro-accelerometer with Sag Optimization

    Directory of Open Access Journals (Sweden)

    B. D. PANT

    2009-10-01

    Full Text Available The current paper presents an optimization study for the designing of a highly sensitive inertial grade capacitive accelerometer based on comb-drive actuation and sensing. The proof mass, suspension system (beams or tethers, stators and rotors have to be realized through an HAR (high aspect ratio DRIE (deep reactive ion etching process for which process optimization has already been done at our laboratory. As the proof mass is a bulk micro-machined structure having a mass in milligram range, the optimum positioning of the tethers on the proof mass is important to have minimum sag, necessary to reduce the off-axis sensitivity. The optimization for the positioning of the tethers has been carried out using a commercial software tool ANSYSTM Multiphysics. The accelerometer has been modeled analytically to predict its characteristics. The dependency of sensitivity on the dimensions of the suspension beams (tethers has also been verified using the above FEM software tool. The present device has been designed to deliver a high sensitivity of 13.6 mV/g/V for low-g applications.

  8. Imaging voltage in neurons

    Science.gov (United States)

    Peterka, Darcy S.; Takahashi, Hiroto; Yuste, Rafael

    2011-01-01

    In the last decades, imaging membrane potential has become a fruitful approach to study neural circuits, especially in invertebrate preparations with large, resilient neurons. At the same time, particularly in mammalian preparations, voltage imaging methods suffer from poor signal to noise and secondary side effects, and they fall short of providing single-cell resolution when imaging of the activity of neuronal populations. As an introduction to these techniques, we briefly review different voltage imaging methods (including organic fluorophores, SHG chromophores, genetic indicators, hybrid, nanoparticles and intrinsic approaches), and illustrate some of their applications to neuronal biophysics and mammalian circuit analysis. We discuss their mechanisms of voltage sensitivity, from reorientation, electrochromic or electro-optical phenomena, to interaction among chromophores or membrane scattering, and highlight their advantages and shortcomings, commenting on the outlook for development of novel voltage imaging methods. PMID:21220095

  9. Calibration of Voltage Transformers and High- Voltage Capacitors at NIST

    Science.gov (United States)

    Anderson, William E.

    1989-01-01

    The National Institute of Standards and Technology (NIST) calibration service for voltage transformers and high-voltage capacitors is described. The service for voltage transformers provides measurements of ratio correction factors and phase angles at primary voltages up to 170 kV and secondary voltages as low as 10 V at 60 Hz. Calibrations at frequencies from 50–400 Hz are available over a more limited voltage range. The service for high-voltage capacitors provides measurements of capacitance and dissipation factor at applied voltages ranging from 100 V to 170 kV at 60 Hz depending on the nominal capacitance. Calibrations over a reduced voltage range at other frequencies are also available. As in the case with voltage transformers, these voltage constraints are determined by the facilities at NIST. PMID:28053409

  10. High voltage engineering fundamentals

    CERN Document Server

    Kuffel, E; Hammond, P

    1984-01-01

    Provides a comprehensive treatment of high voltage engineering fundamentals at the introductory and intermediate levels. It covers: techniques used for generation and measurement of high direct, alternating and surge voltages for general application in industrial testing and selected special examples found in basic research; analytical and numerical calculation of electrostatic fields in simple practical insulation system; basic ionisation and decay processes in gases and breakdown mechanisms of gaseous, liquid and solid dielectrics; partial discharges and modern discharge detectors; and over

  11. Device for monitoring cell voltage

    Science.gov (United States)

    Doepke, Matthias [Garbsen, DE; Eisermann, Henning [Edermissen, DE

    2012-08-21

    A device for monitoring a rechargeable battery having a number of electrically connected cells includes at least one current interruption switch for interrupting current flowing through at least one associated cell and a plurality of monitoring units for detecting cell voltage. Each monitoring unit is associated with a single cell and includes a reference voltage unit for producing a defined reference threshold voltage and a voltage comparison unit for comparing the reference threshold voltage with a partial cell voltage of the associated cell. The reference voltage unit is electrically supplied from the cell voltage of the associated cell. The voltage comparison unit is coupled to the at least one current interruption switch for interrupting the current of at least the current flowing through the associated cell, with a defined minimum difference between the reference threshold voltage and the partial cell voltage.

  12. Model development for prediction and mitigation of dissolved oxygen sags in the Athabasca River, Canada

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Nancy, E-mail: nancy@ualberta.ca [Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB, Canada T6G 2W2 (Canada); McEachern, Preston [Tervita Corporation, AB (Canada); Yu, Tong; Zhu, David Z. [Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB, Canada T6G 2W2 (Canada)

    2013-01-15

    Northern rivers exposed to high biochemical oxygen demand (BOD) loads are prone to dissolved oxygen (DO) sags in winter due to re-aeration occurring within limited open water leads. Additionally, photosynthesis is reduced by decreased daylight hours, inability of solar radiation to pass through ice, and slower algal growth in winter. The low volumetric flow decreases point-source dilution while their travel time increases. The Athabasca River in Alberta, Canada, has experienced these sags which may affect the aquatic ecosystem. A water quality model for an 800 km reach of this river was customized, calibrated, and validated specifically for DO and the factors that determine its concentration. After validation, the model was used to assess the assimilative capacity of the river and mitigation measures that could be deployed. The model reproduced the surface elevation and water temperature for the seven years simulated with mean absolute errors of < 15 cm and < 0.9 °C respectively. The ice cover was adequately predicted for all seven winters, and the simulation of nutrients and phytoplankton primary productivity were satisfactory. The DO concentration was very sensitive to the sediment oxygen demand (SOD), which represented about 50% of the DO sink in winter. The DO calibration was improved by implementing an annual SOD based on the BOD load. The model was used to estimate the capacity of the river to assimilate BOD loads in order to maintain a DO concentration of 7 mg/L, which represents the chronic provincial guideline plus a buffer of 0.5 mg/L. The results revealed the maximum assimilative BOD load of 8.9 ton/day at average flow conditions, which is lower than the maximum permitted load. In addition, the model predicted a minimum assimilative flow of about 52 m{sup 3}/s at average BOD load. Climate change scenarios could increase the frequency of this low flow. A three-level warning-system is proposed to manage the BOD load proactively at different river

  13. Modularized Three-Phase Semiconductor Transformer with Bidirectional Power Flow for Medium Voltage Application

    Directory of Open Access Journals (Sweden)

    Do-Hyun Kim

    2016-08-01

    Full Text Available This paper describes a prototype of modularized three-phase semiconductor transformer that was developed in the lab for feasibility study. The developed prototype is composed of three units of single-phase semiconductor transformer coupled in Y-connection. Each single-phase unit has multiple units of high-voltage high-frequency resonant AC–DC converter, a low-voltage hybrid-switching DC–DC converter, and a low-voltage hybrid-switching DC–AC inverter. Also, each single-phase unit has two digital signal processor (DSP boards to control converter operation and to acquire monitoring data. The monitoring system was developed based on LabView by using controller area network (CAN communication between the DSP board and the personal computer (PC. Through diverse experimental analyses it was verified that the prototype operates with proper performance under normal and sag conditions. The developed prototype confirms the possibility of fabricating a commercial high-voltage high-power semiconductor transformer by increasing the number of series-connected converter modules in high-voltage side and improving the system efficiency with a new switching device such as an SiC device.

  14. Efficacy of SAG-2 oral rabies vaccine in two species of jackal (Canis adustus and Canis mesomelas).

    Science.gov (United States)

    Bingham, J; Schumacher, C L; Hill, F W; Aubert, A

    1999-02-12

    Trials were carried out to test the efficacy of SAG-2 oral rabies vaccine in two species of jackals, namely the side-striped jackal (C. adustus) and the black-backed jackal (C. mesomelas). The first trial tested the efficacy of SAG-2 when given by direct oral administration at doses of 6.5 and 7.5 log10 median tissue culture infectious doses (TCID50). One side-striped jackal which had received the higher dose did not seroconvert and succumbed to challenge, while all other jackals seroconverted and resisted a lethal challenge. The second trial tested the efficacy in side-striped jackals only of the SAG-2 vaccine when given within chicken head baits. A volume of 1.8 ml of vaccine fluid with titers of 7.0 or 8.0 log10 TCID50/ml were placed into blisters which were stapled under the skin of the chicken heads. All jackals (5/5) which received 8.0 log10 TCID50/ml and 3 of 5 which received 7.0 log10 TCID50/ml seroconverted and resisted lethal challenge. A third trial tested the rate of vaccine virus titer loss in chicken head baits placed under field conditions. Titer loss was marked in baits which were not protected from direct sunshine, whereas under vegetation cover approximately log10 TCID50/ml was lost every 3 days. Hence, it was concluded that a bait vaccine virus titer of 8.0 log10 TCID50/ml will be sufficient to immunize wild jackal populations if enough baits can be consumed by jackals within 3 days. This conclusion needs to be tested through the use of oral vaccine in field trials.

  15. Survey of the rubber tree genome reveals a high number of cysteine protease-encoding genes homologous to Arabidopsis SAG12.

    Science.gov (United States)

    Zou, Zhi; Liu, Jianting; Yang, Lifu; Xie, Guishui

    2017-01-01

    Arabidopsis thaliana SAG12, a senescence-specific gene encoding a cysteine protease, is widely used as a molecular marker for the study of leaf senescence. To date, its potential orthologues have been isolated from several plant species such as Brassica napus and Nicotiana tabacum. However, little information is available in rubber tree (Hevea brasiliensis), a rubber-producing plant of the Euphorbiaceae family. This study presents the identification of SAG12-like genes from the rubber tree genome. Results showed that an unexpected high number of 17 rubber orthologues with a single intron were found, contrasting the single copy with two introns in Arabidopsis. The gene expansion was also observed in another two Euphorbiaceae plants, castor bean (Ricinus communis) and physic nut (Jatropha curcas), both of which contain 8 orthologues. In accordance with no occurrence of recent whole-genome duplication (WGD) events, most duplicates in castor and physic nut were resulted from tandem duplications. In contrast, the duplicated HbSAG12H genes were derived from tandem duplications as well as the recent WGD. Expression analysis showed that most HbSAG12H genes were lowly expressed in examined tissues except for root and male flower. Furthermore, HbSAG12H1 exhibits a strictly senescence-associated expression pattern in rubber tree leaves, and thus can be used as a marker gene for the study of senescence mechanism in Hevea.

  16. Geomagnetism and Induced Voltage

    Science.gov (United States)

    Abdul-Razzaq, W.; Biller, R. D.

    2010-01-01

    Introductory physics laboratories have seen an influx of "conceptual integrated science" over time in their classrooms with elements of other sciences such as chemistry, biology, Earth science, and astronomy. We describe a laboratory to introduce this development, as it attracts attention to the voltage induced in the human brain as it…

  17. Biological Mechanisms Underlying the Ultraviolet Radiation-Induced Formation of Skin Wrinkling and Sagging I: Reduced Skin Elasticity, Highly Associated with Enhanced Dermal Elastase Activity, Triggers Wrinkling and Sagging

    Science.gov (United States)

    Imokawa, Genji; Ishida, Koichi

    2015-01-01

    The repetitive exposure of skin to ultraviolet B (UVB) preferentially elicits wrinkling while ultraviolet A (UVA) predominantly elicits sagging. In chronically UVB or UVA-exposed rat skin there is a similar tortuous deformation of elastic fibers together with decreased skin elasticity, whose magnitudes are greater in UVB-exposed skin than in UVA-exposed skin. Comparison of skin elasticity with the activity of matrix metalloproteinases (MMPs) in the dermis of ovariectomized rats after UVB or UVA irradiation demonstrates that skin elasticity is more significantly decreased in ovariectomized rats than in sham-operated rats, which is accompanied by a reciprocal increase in elastase activity but not in the activities of collagenases I or IV. Clinical studies using animal skin and human facial skin demonstrated that topical treatment with a specific inhibitor or an inhibitory extract of skin fibroblast-derived elastase distinctly attenuates UVB and sunlight-induced formation of wrinkling. Our results strongly indicated that the upregulated activity of skin fibroblast-derived elastase plays a pivotal role in wrinkling and/or sagging of the skin via the impairment of elastic fiber configuration and the subsequent loss of skin elasticity. PMID:25856675

  18. Biological mechanisms underlying the ultraviolet radiation-induced formation of skin wrinkling and sagging I: reduced skin elasticity, highly associated with enhanced dermal elastase activity, triggers wrinkling and sagging.

    Science.gov (United States)

    Imokawa, Genji; Ishida, Koichi

    2015-04-08

    The repetitive exposure of skin to ultraviolet B (UVB) preferentially elicits wrinkling while ultraviolet A (UVA) predominantly elicits sagging. In chronically UVB or UVA-exposed rat skin there is a similar tortuous deformation of elastic fibers together with decreased skin elasticity, whose magnitudes are greater in UVB-exposed skin than in UVA-exposed skin. Comparison of skin elasticity with the activity of matrix metalloproteinases (MMPs) in the dermis of ovariectomized rats after UVB or UVA irradiation demonstrates that skin elasticity is more significantly decreased in ovariectomized rats than in sham-operated rats, which is accompanied by a reciprocal increase in elastase activity but not in the activities of collagenases I or IV. Clinical studies using animal skin and human facial skin demonstrated that topical treatment with a specific inhibitor or an inhibitory extract of skin fibroblast-derived elastase distinctly attenuates UVB and sunlight-induced formation of wrinkling. Our results strongly indicated that the upregulated activity of skin fibroblast-derived elastase plays a pivotal role in wrinkling and/or sagging of the skin via the impairment of elastic fiber configuration and the subsequent loss of skin elasticity.

  19. Ten-channel InP-based large-scale photonic integrated transmitter fabricated by SAG technology

    Science.gov (United States)

    Zhang, Can; Zhu, Hongliang; Liang, Song; Cui, Xiao; Wang, Huitao; Zhao, Lingjuan; Wang, Wei

    2014-12-01

    A 10-channel InP-based large-scale photonic integrated transmitter was fabricated by selective area growth (SAG) technology combined with butt-joint regrowth (BJR) technology. The SAG technology was utilized to fabricate the electroabsorption modulated distributed feedback (DFB) laser (EML) arrays at the same time. The design of coplanar electrodes for electroabsorption modulator (EAM) was used for the flip-chip bonding package. The lasing wavelength of DFB laser could be tuned by the integrated micro-heater to match the ITU grids, which only needs one electrode pad. The average output power of each channel is 250 μW with an injection current of 200 mA. The static extinction ratios of the EAMs for 10 channels tested are ranged from 15 to 27 dB with a reverse bias of 6 V. The frequencies of 3 dB bandwidth of the chip for each channel are around 14 GHz. The novel design and simple fabrication process show its enormous potential in reducing the cost of large-scale photonic integrated circuit (LS-PIC) transmitter with high chip yields.

  20. METODOLOGÍA GENERAL PARA CORRELACIONAR SAGS CON EVENTOS AMBIENTALES U OPERATIVOS DEL SISTEMA DE DISTRIBUCIÓN

    Directory of Open Access Journals (Sweden)

    Alejandro Castillo Guasca

    2013-07-01

    Full Text Available Es de gran importancia conocer cuáles son las causas  para que se presenten sags en las barrajes de distribución, debido a que la afectación sobre los clientes industriales es de carácter relevante. Por esta razón se planteó  una metodología para buscar la correlación existente entre sags y los eventos ambientales u operativos del sistema de distribución. A manera de ejemplo, se aplicó en tres subestaciones, las cuales se encuentran ubicadas en diferentes sectores de la ciudad. Para el desarrollo de esta metodología, se realizó la correlación de los datos mediante la implementación de tablas dinámicas y programación en Access, donde se evidenció qué tipo de eventos son los que tienen un mayor impacto sobre los clientes. De acuerdo a los resultados obtenidos se sugiere algunas recomendaciones para mitigar este tipo de eventos en el sistema de distribución.

  1. SAG/ROC-SCFβ-TrCP E3 Ubiquitin Ligase Promotes Pro-Caspase-3 Degradation as a Mechanism of Apoptosis Protection

    Directory of Open Access Journals (Sweden)

    Mingjia Tan

    2006-12-01

    Full Text Available Skp1-cullin-F-box protein (SCF is a multicomponent E3 ubiquitin (Ub ligase that ubiquitinates a number of important biologic molecules such as p27, β-catenin, and lκB for proteasomal degradation, thus regulating cell proliferation and survival. One SCF component, SAG/ROC2/Rbx2/Hrt2, a RING finger protein, was first identified as a redox-inducible protein, which, when overexpressed, inhibited apoptosis both in vitro and in vivo. We report here that sensitive to apoptosis gene (SAG, as well as its family member ROC1/Rbxi, bound to the proinactive form of caspase-3 (pro-caspase-3. Binding was likely mediated through F-box protein, β-transducin repeat-containing protein (β-TrCP, which binds to the first 38 amino acids of pro-caspase-3. Importantly, β-TrCP1 expression significantly shortened the protein half-life of pro-caspase-3, whereas expression of a dominant-negative β-TrCP1 mutant with the F-box domain deleted extended it. An in vitro ubiquitination assay showed that SAG/ROC-SCF -Trcp promoted ubiquitination of pro-caspase-3. Furthermore, endogenous levels of pro-caspase-3 were decreased by overexpression of SAG/ROC-SCFβ-TrCP E3 Ub ligases, but increased on siRNA silencing of SAG, regulator of cullin-1 (ROC1, or β-TrCPs, leading to increased apoptosis by etoposide and TNF-related apoptosis-inducing ligand through increased activation of caspase-3. Thus, pro-caspase-3 appears to be a substrate of SAG/ROC-SCFβ-TrCP E3 Ub ligase, which protects cells from apoptosis through increased apoptosis threshold by reducing the basal level of pro-caspase-3.

  2. Deployment of low-voltage regulator considering existing voltage control in medium-voltage distribution systems

    Directory of Open Access Journals (Sweden)

    Hiroshi Kikusato

    2016-01-01

    Full Text Available Many photovoltaic (PV systems have been installed in distribution systems. This installation complicates the maintenance of all voltages within the appropriate range in all low-voltage distribution systems (LVDSs because the trends in voltage fluctuation differ in each LVDS. The installation of a low-voltage regulator (LVR that can accordingly control the voltage in each LVDS has been studied as a solution to this problem. Voltage control in a medium-voltage distribution system must be considered to study the deployment of LVRs. In this study, we installed LVRs in the LVDSs in which the existing voltage-control scheme cannot prevent voltage deviation and performed a numerical simulation by using a distribution system model with PV to evaluate the deployment of the LVRs.

  3. High yield expression and single-step purification of Toxoplasma gondii SAG1, GRA1, and GRA7 antigens in Escherichia coli

    DEFF Research Database (Denmark)

    Hiszczynska-Sawicka, E.; Brillowska-Dabrowska, A.; Dabrowski, Slawomir

    2003-01-01

    This report describes a simple, highly efficient and reproducible method for obtaining large quantities of highly pure recombinant Toxoplasma gondii antigens, which can be used for diagnostic application. The obtained T gondii SAG1, GRA1, and GRA7 antigens (as fusion proteins), expressed in Esche......This report describes a simple, highly efficient and reproducible method for obtaining large quantities of highly pure recombinant Toxoplasma gondii antigens, which can be used for diagnostic application. The obtained T gondii SAG1, GRA1, and GRA7 antigens (as fusion proteins), expressed...

  4. Impact of the Converter Control Strategies on the Drive Train of Wind Turbine during Voltage Dips

    Directory of Open Access Journals (Sweden)

    Fenglin Miao

    2015-10-01

    Full Text Available The impact of converter control strategies on the drive train of wind turbines during voltage dips is investigated in this paper using a full electromechanical model. Aerodynamics and tower vibration are taken into consideration by means of a simulation program, named FAST. Detailed gearbox and electrical subsystems are represented in MATLAB. The dynamic response of electromagnetic torque and its impact on the mechanical variables are the concern in this paper and the response of electrical variables is less discussed. From the mechanical aspects, the effect of rising power recovery speed and unsymmetrical voltage dips are analyzed on the basis of the dynamic response of the high-speed shaft (HSS. A comparison of the impact on the drive train is made for two converter control strategies during small voltage dips. Through the analysis of torque, speed and tower vibration, the results indicate that both power recovery speed and the sudden torque sag have a significant impact on drive trains, and the effects depend on the different control strategies. Moreover, resonance might be excited on the drive train by an unbalanced voltage.

  5. High Voltage Charge Pump

    KAUST Repository

    Emira, Ahmed A.

    2014-10-09

    Various embodiments of a high voltage charge pump are described. One embodiment is a charge pump circuit that comprises a plurality of switching stages each including a clock input, a clock input inverse, a clock output, and a clock output inverse. The circuit further comprises a plurality of pumping capacitors, wherein one or more pumping capacitors are coupled to a corresponding switching stage. The circuit also comprises a maximum selection circuit coupled to a last switching stage among the plurality of switching stages, the maximum selection circuit configured to filter noise on the output clock and the output clock inverse of the last switching stage, the maximum selection circuit further configured to generate a DC output voltage based on the output clock and the output clock inverse of the last switching stage.

  6. High Voltage Seismic Generator

    Science.gov (United States)

    Bogacz, Adrian; Pala, Damian; Knafel, Marcin

    2015-04-01

    This contribution describes the preliminary result of annual cooperation of three student research groups from AGH UST in Krakow, Poland. The aim of this cooperation was to develop and construct a high voltage seismic wave generator. Constructed device uses a high-energy electrical discharge to generate seismic wave in ground. This type of device can be applied in several different methods of seismic measurement, but because of its limited power it is mainly dedicated for engineering geophysics. The source operates on a basic physical principles. The energy is stored in capacitor bank, which is charged by two stage low to high voltage converter. Stored energy is then released in very short time through high voltage thyristor in spark gap. The whole appliance is powered from li-ion battery and controlled by ATmega microcontroller. It is possible to construct larger and more powerful device. In this contribution the structure of device with technical specifications is resented. As a part of the investigation the prototype was built and series of experiments conducted. System parameter was measured, on this basis specification of elements for the final device were chosen. First stage of the project was successful. It was possible to efficiently generate seismic waves with constructed device. Then the field test was conducted. Spark gap wasplaced in shallowborehole(0.5 m) filled with salt water. Geophones were placed on the ground in straight line. The comparison of signal registered with hammer source and sparker source was made. The results of the test measurements are presented and discussed. Analysis of the collected data shows that characteristic of generated seismic signal is very promising, thus confirms possibility of practical application of the new high voltage generator. The biggest advantage of presented device after signal characteristics is its size which is 0.5 x 0.25 x 0.2 m and weight approximately 7 kg. This features with small li-ion battery makes

  7. Increased voltage photovoltaic cell

    Science.gov (United States)

    Ross, B.; Bickler, D. B.; Gallagher, B. D. (Inventor)

    1985-01-01

    A photovoltaic cell, such as a solar cell, is provided which has a higher output voltage than prior cells. The improved cell includes a substrate of doped silicon, a first layer of silicon disposed on the substrate and having opposite doping, and a second layer of silicon carbide disposed on the first layer. The silicon carbide preferably has the same type of doping as the first layer.

  8. Voltage Controlled Dynamic Demand Response

    DEFF Research Database (Denmark)

    Bhattarai, Bishnu Prasad; Bak-Jensen, Birgitte; Mahat, Pukar

    2013-01-01

    central or dispersed generations might not be sufficient for future scenario. One of the effective methods to cope with this scenario is to enable demand response. This paper proposes a dynamic voltage regulation based demand response technique to be applied in low voltage (LV) distribution feeders....... An adaptive dynamic model has been developed to determine composite voltage dependency of an aggregated load on feeder level. Following the demand dispatch or control signal, optimum voltage setting at the LV substation is determined based on the voltage dependency of the load. Furthermore, a new technique...... has been proposed to estimate the voltage at consumer point of connection (POC) to ensure operation within voltage limits. Finally, the effectiveness of the proposed method is analyzed comprehensively with reference to three different scenarios on a low voltage (LV) feeder (Borup feeder) owned...

  9. Low-voltage polyphasic circuits

    Science.gov (United States)

    Baird, William H.; Jaynes, Michael L.

    2010-05-01

    Experimentation with polyphasic voltages is greatly simplified when microcontrollers are used to generate multiple square waves with fixed phase offsets. Each square wave is sent through a simple second-order Sallen-Key filter to produce an approximately sinusoidal voltage signal. The microcontroller allows the reproduction of split-phase and three-phase voltage relationships, mirroring those commonly distributed on the North American power grid, at safe voltage levels.

  10. High voltage variable diameter insulator

    Science.gov (United States)

    Vanecek, David L.; Pike, Chester D.

    1984-01-01

    A high voltage feedthrough assembly (10) having a tubular insulator (15) extending between the ground plane ring (16) and the high voltage ring (30). The insulator (15) is made of Pyrex and decreases in diameter from the ground plane ring (16) to the high voltage ring (30), producing equipotential lines almost perpendicular to the wall (27) of the insulator (15) to optimize the voltage-holding capability of the feedthrough assembly (10).

  11. Charge-pump voltage converter

    Science.gov (United States)

    Brainard, John P [Albuquerque, NM; Christenson, Todd R [Albuquerque, NM

    2009-11-03

    A charge-pump voltage converter for converting a low voltage provided by a low-voltage source to a higher voltage. Charge is inductively generated on a transfer rotor electrode during its transit past an inductor stator electrode and subsequently transferred by the rotating rotor to a collector stator electrode for storage or use. Repetition of the charge transfer process leads to a build-up of voltage on a charge-receiving device. Connection of multiple charge-pump voltage converters in series can generate higher voltages, and connection of multiple charge-pump voltage converters in parallel can generate higher currents. Microelectromechanical (MEMS) embodiments of this invention provide a small and compact high-voltage (several hundred V) voltage source starting with a few-V initial voltage source. The microscale size of many embodiments of this invention make it ideally suited for MEMS- and other micro-applications where integration of the voltage or charge source in a small package is highly desirable.

  12. Transient voltage sharing in series-coupled high voltage switches

    Directory of Open Access Journals (Sweden)

    Editorial Office

    1992-07-01

    Full Text Available For switching voltages in excess of the maximum blocking voltage of a switching element (for example, thyristor, MOSFET or bipolar transistor such elements are often coupled in series - and additional circuitry has to be provided to ensure equal voltage sharing. Between each such series element and system ground there is a certain parasitic capacitance that may draw a significant current during high-speed voltage transients. The "open" switch is modelled as a ladder network. Analy­sis reveals an exponential progression in the distribution of the applied voltage across the elements. Overstressing thus oc­curs in some of the elements at levels of the total voltage that are significantly below the design value. This difficulty is overcome by grading the voltage sharing circuitry, coupled in parallel with each element, in a prescribed manner, as set out here.

  13. Design and control of single-phase dynamic voltage restorer

    Indian Academy of Sciences (India)

    Amit Meena

    ventionally, DVR consists of an energy storage device, which supplies the required power over the limited duration of the sags. Large magnitude and long duration of sags lead to heavy financial investment in energy storage unit. To overcome this limitation, a single-phase back-to-back converter-based DVR is implemented ...

  14. Coordinated Voltage Control of Distributed PV Inverters for Voltage Regulation in Low Voltage Distribution Networks

    DEFF Research Database (Denmark)

    Nainar, Karthikeyan; Pokhrel, Basanta Raj; Pillai, Jayakrishnan Radhakrishna

    2017-01-01

    This paper reviews and analyzes the existing voltage control methods of distributed solar PV inverters to improve the voltage regulation and thereby the hosting capacity of a low-voltage distribution network. A novel coordinated voltage control method is proposed based on voltage sensitivity...... optimization. The proposed method is used to calculate the voltage bands and droop settings of PV inverters at each node by the supervisory controller. The local controller of each PV inverter implements the volt/var control and if necessary, the active power curtailment as per the received settings and based...... on measured local voltages. The advantage of the proposed method is that the calculated reactive power and active power droop settings enable fair contribution of the PV inverters at each node to the voltage regulation. Simulation studies are conducted using DigSilent Power factory software on a simplified...

  15. Comparison between Different Control Strategies of a Z-Source Inverter Based Dynamic Voltage Restorer

    Directory of Open Access Journals (Sweden)

    Abolfazl Kazemdehdashti

    2013-01-01

    Full Text Available In this paper, dynamic voltage restorer (DVR compensation methods are compared to each other for the load side connected shunt converter topology of z-source inverter based DVR to choose the best method. Four different topologies are recognized for DVR that two of them have energy storage devices, and two topologies have no energy storage that take ener\\-gy from the grid during the period of compensation. Here the load side connected shunt converter topology that takes necessary energy from the grid is used. Pre-sag compensation, in-phase compensation, energy-optimized methods are the three DVR compensation methods that studied and compared. A deep analysis through different diagrams would show the advantages or disadvantages of each compensation method. Equations for all methods are derived and the characteristics of algorithms are compared with each other. The simulation results done by SIMULINK/ MATLAB shows compensating by this topology based on the compensation methods.

  16. AGRO-SYSTEM (AGS AS A TOOL FOR ANALYSIS, TAKING INTO ACCOUNT SUSTAINABILITY/ SISTEMA AGROINDUSTRIAL (SAG COMO UM INSTRUMENTO DE ANÁLISE, CONSIDERANDO A SUSTENTABILIDADE

    Directory of Open Access Journals (Sweden)

    Kassia WATANABE

    2011-06-01

    Full Text Available A proposta desse artigo é apresentar o sistema agroindustrial (SAG como um instrumento de análise que pode ser aplicado em diferentes sistemas, tais como sistema de produção de alimentos, sistema de produção de biodiesel, entre outros. A questão para esse artigo é a seguinte: Como a sustentabilidade pode ser analisada no SAG? A análise do SAG é importante porque pode apontar melhorias ou introduzir novo arranjo institucional (formas organizacionais. Entretanto, o arranjo institucional pode não ser suficiente bom quando transplantado para outro lugar e as instituições precisam ser consideradas. Por essa razão, o SAG é analisado dentro de um ambiente institucional que envolve as “regras do jogo”. Além disso, questões sociais e ambientais são levadas em consideração e fazem parte do arranjo e do ambiente institucional.Palavras-chave: Sistema Agroindustrial; Sustentabilidade; Arranjo Institucional

  17. Usefulness of Toxoplasma gondii recombinant antigens (GRA1, GRA7 and SAG1) in an immunoglobulin G avidity test for the serodiagnosis of toxoplasmosis

    DEFF Research Database (Denmark)

    Pietkiewicz, H; Hiszczyńska-Sawicka, E; Kur, J

    2007-01-01

    The precise diagnosis of an acute and recent Toxoplasma infection in pregnant women and the newborn child is important before treatment. This study describes a new Toxoplasma gondii IgG avidity test based on a combination of recombinant GRA1, GRA7 and SAG1 antigens and shows that this test...

  18. Sagging Eye Syndrome or Nemaline Rod Myopathy? Divergence Insufficiency with Levator Dehiscence as an Overlapping Symptom between Two Diagnoses

    Directory of Open Access Journals (Sweden)

    Stephanie S. L. Cheung

    2017-01-01

    Full Text Available A 78-year-old woman complained of gradual, painless onset of horizontal binocular diplopia associated with progressive axial weakness. Physical examination revealed esotropia that was greater at distance than at near vision, bilateral levator dehiscence, and normal abducting saccadic speeds. Given the age of the patient and compatible clinical findings, the diagnosis of Sagging Eye Syndrome (SES was made. However, further work-up with a muscle biopsy suggested Sporadic Late-Onset Nemaline Myopathy (SLONM as the cause of her progressive muscle weakness. Although rare, external ophthalmoplegia has been described in the literature as a presenting symptom in SLONM. To elucidate the pathological mechanism for the patient’s diplopia, an MRI of the orbits was performed, which revealed findings consistent with SES. This case aims to highlight the importance of integrating clinical findings during the diagnostic process and serves as a reminder that diplopia can be a common symptom for an uncommon diagnosis.

  19. In-line filtration of SAG-M red cell concentrates prepared in top/bottom or conventional bag systems.

    Science.gov (United States)

    Müller, N

    1996-01-01

    SAG-M RCCs were prepared in triple conventional or quadruple top/bottom bag systems and filtered at +4 degrees C using the in-line filter system Leucoflex LCR 4 Macopharma after 16-24-30 h of storage. Postfiltration WBC content was determined by Nageotte hemocytometer counting. The mean WBC content of the units prepared in conventional bag systems and filtered was higher than that of the units prepared in T/B bag systems. The best results could be obtained in T/B RCCs stored for 24 h; potassium and hemolysis levels were also improved. The Leucoflex LCR 4 in-line filter T/B system can be recommended for application in the clinical routine by virtue of the effective leukocyte elimination.

  20. Seroprevalence of antibody to NcSAG1 antigen of Neospora caninum in cattle from Western Java, Indonesia.

    Science.gov (United States)

    Ichikawa-Seki, Madoka; Guswanto, Azirwan; Allamanda, Puttik; Mariamah, Euis Siti; Wibowo, Putut Eko; Nishikawa, Yoshifumi

    2016-01-01

    Neospora caninum can cause fetal abortion and neonatal mortality in cattle, and is a cause of economic concern worldwide. This study aimed to determine the prevalence of Neospora caninum-specific antibodies in cattle from Western Java, Indonesia. Serum samples from 991 cattle from 21 locations were tested for antibodies to N. caninum by using an enzyme-linked immunosorbent assay (ELISA) on the basis of recombinant NcSAG1. The overall seroprevalence was 16.6%, ranging from 0 to 87.5% in the sampled locations. The results of this study indicate latent infection rates of sampled animals were different in each location. Further studies are necessary to elucidate the relationship between N. caninum infection and abortion in cattle, and to identify risk factors for infection in high-prevalence environments.

  1. Coordinated Voltage Control of Distributed PV Inverters for Voltage Regulation in Low Voltage Distribution Networks

    DEFF Research Database (Denmark)

    Nainar, Karthikeyan; Pokhrel, Basanta Raj; Pillai, Jayakrishnan Radhakrishna

    2017-01-01

    This paper reviews and analyzes the existing voltage control methods of distributed solar PV inverters to improve the voltage regulation and thereby the hosting capacity of a low-voltage distribution network. A novel coordinated voltage control method is proposed based on voltage sensitivity...... analysis, which is simple for computation and requires moderate automation and communication infrastructure. The proposed method is suitable for a hierarchical control structure where a supervisory controller has the provision to adapt the settings of local PV inverter controllers for overall system...

  2. A Simplified Model Applied to the Barite Sag and Fluid Flow in Drilling Muds: Simulation and Experimental Results

    Directory of Open Access Journals (Sweden)

    Messias Ribeiro José

    2017-07-01

    Full Text Available In this work, a study on the modeling of sedimentation and transport of barite particles in drilling fluids was developed. The goal of this study was to evaluate the feasibility of using a simplified two-phase model based on conservation equations to describe the sedimentation of particulate material in drilling fluids. The model was evaluated in three different case studies, where the transport and the sedimentation of solid particles in a carrying fluid were simulated. The simulation results included a two-dimensional flow of liquid in the absence of particles; the axial flow of fluid and particles to investigate the existence of the slip velocity; and the one-dimensional particle settling in drilling fluids. The resulting model used to predict the barite sag is based on the conservation equations and uses the Eulerian approach to take into account the two-phase flow. The model was able to predict the barite sedimentation as well as the formation and properties of the bed of particles. Moreover, the proposed model can be used to evaluate the influence of the particle size, the liquid viscosity, and the solids concentration on the sedimentation process of particles in drilling fluids. Experimental work was also conducted in order to estimate the parameters of the proposed model related to the solid-solid force interaction due to solid particles, and the contribution of the pressure gradient. The results were analyzed by using the one-way ANOVA test for a 95% confidence level, and showed significant reproducibility. Therefore, despite to the simplicity of the proposed model, it could be used as a first approach to the modeling of the barite sag in drilling fluids.

  3. Voltage Dependence of Supercapacitor Capacitance

    Directory of Open Access Journals (Sweden)

    Szewczyk Arkadiusz

    2016-09-01

    Full Text Available Electronic Double-Layer Capacitors (EDLC, called Supercapacitors (SC, are electronic devices that are capable to store a relatively high amount of energy in a small volume comparing to other types of capacitors. They are composed of an activated carbon layer and electrolyte solution. The charge is stored on electrodes, forming the Helmholtz layer, and in electrolyte. The capacitance of supercapacitor is voltage- dependent. We propose an experimental method, based on monitoring of charging and discharging a supercapacitor, which enables to evaluate the charge in an SC structure as well as the Capacitance-Voltage (C-V dependence. The measurement setup, method and experimental results of charging/discharging commercially available supercapacitors in various voltage and current conditions are presented. The total charge stored in an SC structure is proportional to the square of voltage at SC electrodes while the charge on electrodes increases linearly with the voltage on SC electrodes. The Helmholtz capacitance increases linearly with the voltage bias while a sublinear increase of total capacitance was found. The voltage on SC increases after the discharge of electrodes due to diffusion of charges from the electrolyte to the electrodes. We have found that the recovery voltage value is linearly proportional to the initial bias voltage value.

  4. Evaluation of an in-house TgSAG1 (P30) IgG ELISA for diagnosis of naturally acquired Toxoplasma gondii infection in pigs.

    Science.gov (United States)

    Pardini, L; Maksimov, P; Herrmann, D C; Bacigalupe, D; Rambeaud, M; Machuca, M; Moré, G; Basso, W; Schares, G; Venturini, M C

    2012-10-26

    Toxoplasma gondii is an apicomplexan protozoan parasite which is able to infect a large variety of warm-blooded animals. Raw or undercooked pork has been regarded as an important source of infection for humans. The aim of this study was to evaluate an in-house enzyme-linked immunosorbent assay to diagnose natural T. gondii infection in swine using native affinity chromatography-purified T. gondii surface protein-1 (TgSAG1-ELISA) as antigen, comparing its performance to that of indirect fluorescent antibody test (IFAT) and immunoblotting (IB). To obtain a panel of sera showing the evolution of the antibody response in the time course 12 pigs were experimentally inoculated intravenously (iv) with tachyzoites of the T. gondii strains RH (clonal type I), ME49 (clonal type II) and NED (clonal type III) and serologically monitored for a period of 11 weeks. Both IFAT and ELISA showed a similar time course of antibody response to T. gondii; but by IFAT this response was characterized by rapidly rising titers with peaks at two weeks post inoculation (wpi), while the ELISA indices increased slowly and reached a maximum in most animals at five wpi. Three-hundred randomly selected sera from a total of 602 pigs of different ages derived from outdoor and indoor farms from Argentina were analyzed. Serum samples testing either positive or negative by both IFAT and IB were considered as "relative standards of comparison" (RSC). Sensitivity and specificity of TgSAG1-ELISA were obtained by a Receiver Operating Characteristics (ROC) analysis and statistical agreement among serological tests was evaluated. Antibodies to T. gondii were detected in 160 of 300 sera (53.3%) by IB, in 133 of 300 (44.3%) by IFAT and in 123 of 300 sera (41%) by TgSAG1-ELISA. One hundred and eleven sera tested positive and 118 sera tested negative by both IFAT and IB (RSC); 103 of 111 positive RSC sera tested positive by TgSAG1-ELISA, and 116 of 118 negative RSC sera tested negative by TgSAG1-ELISA. Agreement

  5. Organic geochemistry and hydrocarbon potential contrasts among lithologically different source rocks in the Qingxi Sag, Jiuquan Basin, Northwest China

    Science.gov (United States)

    Zhang, Weiwei; Huang, Zhilong; Gao, Gang; Yin, Yue; Li, Tianjun

    2017-04-01

    Jiuquan Basin, located in the eastern part of Hexi Corridor, is a medium- to small-sized superimposed basin in northwest China. Situated in the southwest of the basin is the Qingxi sag, in which the development of large sets of argillaceous dolomite dominate (lithological assemblage named as LSA) and dolomitic mudstone (LSB), partially being mudstone. From electronical and seismic profile features, the Lower Cretaceous can be divided into the Chijinpu Formation, Xiagou Formation, and Zhonggou Formation in the Qingxi Sag. Moreover, the Xiagou Formation can be divided into four members, represented as K1g0, K1g1, K1g2, and K1g3. The given lithological assemblages and occurrence of particular mineralogical combinations indicate that it is the product of hydrothermal deposition. Lithologically, the argillaceous dolomite and dolomitic mudstone are diametrically different in both mineral contents and types. The integration of field outcrop observation and sampling with laboratory analyses, including solvent extract, Rock-Eval (S1, S2, and Tmax), organic petrography (lithological identification, cement, grain, mineral, and maceral observation), and laboratory modeling of hydrocarbon generation, show that both LSA and LSB contains good hydrocarbon potentials but rather different mineralogical compositions. The concurrence of LSA and LSB indicates the alternate interaction between the hydrothermal deposition and normal lacustrine deposits. The LSA mainly contains Type I kerogen and much lower Pr/Ph ratio, indicating parental material sourced from lacustrine algae and bacteria and much stronger reduction depostional environment. However, the LSB mainly contains Type III kerogen, containing parental material mainly sourced from terrestrial higher plant. And in the mudstone, there is almost no Type I kerogen, indicating no substantial input of lacustrine phytoplankton. The LSA contains TOC value of 1.2-3.2% (wt), averaging 2.1% (wt); while the LSB contains 0.8-2.4% (wt) with

  6. Interest of retro-anal levator plate myorrhaphy in selected cases of descending perineum syndrome with positive anti-sagging test

    Directory of Open Access Journals (Sweden)

    Beco Jacques

    2008-07-01

    Full Text Available Abstract Background Levator plate sagging (LPS, usually called descending perineum syndrome, is one of the main defects encountered in perineology. This defect is classically associated with colo-proctologic functional troubles (dyschesia and anal incontinence but can also induce perineodynia, gynaecological and lower urinary tract symptoms. Methods A retrospective case series of nine female patients (mean age: 44.3 underwent an isolated retro-anal levator plate myorrhaphy (RLPM to treat symptomatic LPS confirmed by rectal examination and/or Perineocaliper®. An anti-sagging test (support of the posterior perineum must significantly improve the symptoms that were resistant to conservative treatment. The effect of the procedure on the symptoms of the 3 axes of the perineum (urological, colo-proctologic and gynecological and on perineodynia was evaluated during a follow up consultation more than 9 months after surgery. The effect of RLPM on the position of the anal margin and on the levator plate angle was studied using rectal examination, Perineocaliper® and retro-anal ultrasound. Results Before surgery, anti-sagging tests were positive for dyschesia, urinary urgency and pain. After a mean follow-up of 16.1 months, RLPM resolved or improved 2/2 cases of stress urinary incontinence, 3/5 of urinary urgency, 3/4 of dysuria, 3/3 of anal incontinence, 7/8 of dyschesia, 3/4 of cystocele, 4/5 of rectocele, 5/8 of dyspareunia and 6/7 of perineodynia. Rectal examination showed a complete suppression of sagging in 4 patients and an improvement in the 5 others. The mean reduction of perineal descent was 1.08 cm (extremes: 0–1.5. Using retro-anal ultrasound of the levator plate, the mean reduction of sagging was 12.67 degrees (extremes: 1 – 21. Conclusion Anti-sagging tests can be used before surgery to simulate the effect of RLPM. This surgical procedure seems to improve stress urinary incontinence, frequency, nocturia, urgency, dysuria, anal

  7. Sedimentary characteristics of thick layer lacustrine beach-bars in the Cenozoic Banqiao Sag of the Bohai Bay Basin, East China

    Science.gov (United States)

    Song, Fan; Su, Nina; Yang, Shaochun; Yao, Ruixiang; Chu, Shumin

    2018-01-01

    Lacustrine beach-bar reservoirs have become important exploration targets in the Bohai Bay Basin in China, especially in the Banqiao Sag within the Huanghua Depression, where some typical thick layer beach-bar reservoirs have been discovered recently. The average single-layer thickness of the beach-bar sand bodies in the second member of the Paleogene Shahejie Formation within the sag is greater than 10 m and the cumulative thickness of these sands reach up to 100 m. The second member of the Shahejie Formation in the Banqiao Sag consists of a third-order sequence of three systems tracts-a lowstand systems tract, a transgressive systems tract, and a highstand systems tract. Beach-bar sand bodies were deposited widely in the sag in the lowstand systems tract, but were less deposited in the other systems tracts. The sedimentary characteristics, distribution patterns, and formation mechanisms of the beach-bar sand bodies in the lowstand systems tract of the second member of the Shahejie Formation were systemically studied using cores, wireline logs and 3D seismic data. The beach-bar was divided into five sedimentary microfacies, namely, sandy bar centre, sandy bar flank, interbar deposit, coastal beach, and infralittoral beach. Based on the integrated analysis of the paleostructure and sedimentary environment, it was inferred that the thick layer beach-bars in this area resulted from the combination and joint control of the sediment source system, hydrodynamic environment, lake level variations, and contemporaneous fault activity. Firstly, the sands in the braided river delta of the Beidagang buried hill structural belt served as the provenance that provided the material basis for the beach-bars in the Banqiao Sag. Secondly, the wave effects in the gentle-slope belt controlled the scale and distribution of the beach bars. Under the control of waves, various sedimentary microfacies were regularly distributed. In particular, the continuous activity of the contemporaneous

  8. Interest of retro-anal levator plate myorrhaphy in selected cases of descending perineum syndrome with positive anti-sagging test

    Science.gov (United States)

    Beco, Jacques

    2008-01-01

    Background Levator plate sagging (LPS), usually called descending perineum syndrome, is one of the main defects encountered in perineology. This defect is classically associated with colo-proctologic functional troubles (dyschesia and anal incontinence) but can also induce perineodynia, gynaecological and lower urinary tract symptoms. Methods A retrospective case series of nine female patients (mean age: 44.3) underwent an isolated retro-anal levator plate myorrhaphy (RLPM) to treat symptomatic LPS confirmed by rectal examination and/or Perineocaliper®. An anti-sagging test (support of the posterior perineum) must significantly improve the symptoms that were resistant to conservative treatment. The effect of the procedure on the symptoms of the 3 axes of the perineum (urological, colo-proctologic and gynecological) and on perineodynia was evaluated during a follow up consultation more than 9 months after surgery. The effect of RLPM on the position of the anal margin and on the levator plate angle was studied using rectal examination, Perineocaliper® and retro-anal ultrasound. Results Before surgery, anti-sagging tests were positive for dyschesia, urinary urgency and pain. After a mean follow-up of 16.1 months, RLPM resolved or improved 2/2 cases of stress urinary incontinence, 3/5 of urinary urgency, 3/4 of dysuria, 3/3 of anal incontinence, 7/8 of dyschesia, 3/4 of cystocele, 4/5 of rectocele, 5/8 of dyspareunia and 6/7 of perineodynia. Rectal examination showed a complete suppression of sagging in 4 patients and an improvement in the 5 others. The mean reduction of perineal descent was 1.08 cm (extremes: 0–1.5). Using retro-anal ultrasound of the levator plate, the mean reduction of sagging was 12.67 degrees (extremes: 1 – 21). Conclusion Anti-sagging tests can be used before surgery to simulate the effect of RLPM. This surgical procedure seems to improve stress urinary incontinence, frequency, nocturia, urgency, dysuria, anal incontinence, dyschesia

  9. Voltage Stability Impact of Grid-Tied Photovoltaic Systems Utilizing Dynamic Reactive Power Control

    Science.gov (United States)

    Omole, Adedamola

    Photovoltaic (PV) DGs can be optimized to provide reactive power support to the grid, although this feature is currently rarely utilized as most DG systems are designed to operate with unity power factor and supply real power only to the grid. In this work, the voltage stability of a power system embedded with PV DG is examined in the context of the high reactive power requirement after a voltage sag or fault. A real-time dynamic multi-function power controller that enables renewable source PV DGs to provide the reactive power support necessary to maintain the voltage stability of the microgrid, and consequently, the wider power system is proposed. The loadability limit necessary to maintain the voltage stability of an interconnected microgrid is determined by using bifurcation analysis to test for the singularity of the network Jacobian and load differential equations with and without the contribution of the DG. The maximum and minimum real and reactive power support permissible from the DG is obtained from the loadability limit and used as the limiting factors in controlling the real and reactive power contribution from the PV source. The designed controller regulates the voltage output based on instantaneous power theory at the point-of-common coupling (PCC) while the reactive power supply is controlled by means of the power factor and reactive current droop method. The control method is implemented in a modified IEEE 13-bus test feeder system using PSCADRTM power system analysis software and is applied to the model of a Tampa ElectricRTM PV installation at Lowry Park Zoo in Tampa, FL. This dissertation accomplishes the systematic analysis of the voltage impact of a PV DG-embedded power distribution system. The method employed in this work bases the contribution of the PV resource on the voltage stability margins of the microgrid rather than the commonly used loss-of-load probability (LOLP) and effective load-carrying capability (ELCC) measures. The results of

  10. Enhancement of DFIG-Wind Turbine’s LVRT capability using novel DVR based Odd-nary Cascaded Asymmetric Multi-Level Inverter

    Directory of Open Access Journals (Sweden)

    A.D. Falehi

    2017-06-01

    Full Text Available One of the most prominent issues relevant to Doubly Fed Induction Generator (DFIG is augmentation of its Low Voltage Ride Through (LVRT capability. Dynamic Voltage Restorer (DVR is a series kind of Distributed-Flexible AC Transmission Systems (D-FACTS that is here occupied to preserve the DFIG from the voltage sag whenever a fault to be occurred in the power system. Multi-Level Inverter (MLI is the beating-heart of DVR with unique responsibility of synthesizing a staircase sinusoidal voltage from the DC voltage sources. In this regard, it is immensely important a high performance and cost-effective MLI to be embedded into the DVR. In this paper, a novel MLI is introduced to provide a staircase sinusoidal voltage with high level numbers against less switch numbers as compared to the other kinds of MLIs. By adding the bi-directional switches and capacitors of sub-MLI as well as amount of DC sources, the held forth MLI can also operate as so-called “Odd-nary” Cascaded Asymmetric Multi-Level Inverter (OCAMLI. The performance of proposed DVR based on OCAMLI i.e., DVR-OCAMLI has been thoroughly evaluated under deep and shallow balanced and unbalanced voltage sags so that its LVRT capability to be cleared up. To more scrutinize the performance of DVR-OCAMLI, it has been withal dealt with under severe and slight voltage swells as well as harmonic voltage. The accuracy and performance of DVR-OCAMLI has been furthermore compared with conventional DVR. To sum up, the relevant analytical study along with the simulation results has transparently corroborated the performance of OCAMLI as compared to other MLIs. Meanwhile, the DVR-OCAMLI has significantly compensated deep and shallow symmetric and asymmetric voltage sags to enhance the LVRT capability of DFIG; correspondingly, the severe and slight symmetric and asymmetric voltage swells as well as voltage harmonic have been exceptionally compensated as compared to conventional DVR.

  11. Seroconversion in captive African wild dogs (Lycaon pictus) following administration of a chicken head bait/SAG-2 oral rabies vaccine combination.

    Science.gov (United States)

    Knobel, D L; Liebenberg, A; Du Toit, J T

    2003-03-01

    This study determined the proportion of captive juvenile and adult African wild dogs (Lycaon pictus) that developed protective titres of rabies neutralising antibodies following ingestion of a chicken head bait/SAG-2 oral rabies vaccine combination. A single chicken head containing 1.8 ml of SAG-2 vaccine (10(8.0) TCID50/ml) in a plastic blister was fed to each of eight adult and three juvenile wild dogs. Bait ingestion resulted in a significant rise in serum neutralising antibody titres. Overall seroconversion rate was eight out of 11 (72.7%), and all the puppies and five out of eight (62.5%) adults showed potentially protective levels of antibodies on day 31. The mean post-vaccination neutralising antibody titre was within the range reported to be protective against challenge with virulent rabies virus in other species.

  12. A pre-Paleogene unconformity surface of the Sikeshu Sag, Junggar Basin: Lithological, geophysical and geochemical implications for the transportation of hydrocarbons

    Directory of Open Access Journals (Sweden)

    Xiaoyue Gao

    2013-11-01

    Full Text Available The unconformity surface at the bottom of the Paleogene is one of the most important migration pathways in the Sikeshu Sag of the Junggar Basin, which consists of three layers: upper coarse clastic rock, lower weathering crust and leached zone. The upper coarse clastic rock is characterized by higher density and lower SDT and gamma-ray logging parameters, while the lower weathering crust displays opposite features. The transport coefficient of the unconformity surface is controlled by its position in respect to the basal sandstone; it is higher in the ramp region but lower in the adjacent uplifted and sag areas. The content of saturated hydrocarbons increases with the decrease of the content of non-hydrocarbons and asphaltenes. The content of benzo[c] carbazole decreases as the content of benzo[a] carbazole and [alkyl carbazole]/[alkyl + benzo carbazole] increases. This suggests that the unconformity surface is an efficient medium for the transportation of hydrocarbons.

  13. Regulation of sagA, siaA and scpC by SilCR, a putative signaling peptide of Streptococcus pyogenes.

    Science.gov (United States)

    Salim, Kowthar Y; de Azavedo, Joyce C; Bast, Darrin J; Cvitkovitch, Dennis G

    2008-12-01

    SilCR, a 17 amino acid putative signaling peptide, was proposed to modulate gene expression in Streptococcus pyogenes. We showed that SilCR added exogenously to an M1 serotype strain lacking the sil locus upregulates the in vitro expression of sagA, siaA, and scpC, genes associated with S. pyogenes pathogenesis. Interestingly, only sagA and siaA were upregulated by SilCR in vivo, whereas the expression of scpC remained unaltered. A previous report indicated that exogenously added SilCR protects mice to some degree from developing necrotic lesions caused by an invasive strain of S. pyogenes. In contrast to this report, we found that SilCR did not reduce lesion formation in a subcutaneous murine model of S. pyogenes infection but rather appeared to delay wound healing.

  14. Assessment of frontal lobe sagging after endoscopic endonasal transcribriform resection of anterior skull base tumors: is rigid structural reconstruction of the cranial base defect necessary?

    Science.gov (United States)

    Eloy, Jean Anderson; Shukla, Pratik A; Choudhry, Osamah J; Singh, Rahul; Liu, James K

    2012-12-01

    The endoscopic endonasal transcribriform approach (EETA) is a viable alternative option for resection of selected anterior skull base (ASB) tumors. However, this technique results in the creation of large cribriform defects. Some have reported the use of a rigid substitute for ASB reconstruction to prevent postoperative frontal lobe sagging. We evaluate the degree of frontal lobe sagging using our triple-layer technique [fascia lata, acellular dermal allograft, and pedicled nasoseptal flap (PNSF)] without the use of rigid structural reconstruction for large cribriform defects. Retrospective analysis. Nine patients underwent an EETA for resection of large ASB tumors from August 2010 to November 2011. The degree of frontal lobe displacement after EETA, defined as the ASB position, was calculated based on the most inferior position of the frontal lobe relative to the nasion-sellar line defined on preoperative and postoperative imaging. A positive value signified upward displacement, and a negative value represented inferior displacement of the frontal lobe. The average cribriform defect size was 9.3 cm(2) (range, 5.0-13.8 cm(2) ). The average distance of postoperative frontal lobe displacement was 0.2 mm (range, -3.9 to 2.9 mm) without any cases of significant brain sagging. The mean follow-up period was 10.1 months (range, 4-19 months). There were no postoperative CSF leaks. Rigid structural repair may not be necessary for ASB defect repair after endoscopic endonasal resection of the cribriform plate. Our technique for multilayer cranial base reconstruction appears to be satisfactory in preventing delayed frontal lobe sagging. Copyright © 2012 The American Laryngological, Rhinological, and Otological Society, Inc.

  15. A Novel Dominant Mutation in SAG, the Arrestin-1 Gene, Is a Common Cause of Retinitis Pigmentosa in Hispanic Families in the Southwestern United States.

    Science.gov (United States)

    Sullivan, Lori S; Bowne, Sara J; Koboldt, Daniel C; Cadena, Elizabeth L; Heckenlively, John R; Branham, Kari E; Wheaton, Dianna H; Jones, Kaylie D; Ruiz, Richard S; Pennesi, Mark E; Yang, Paul; Davis-Boozer, David; Northrup, Hope; Gurevich, Vsevold V; Chen, Rui; Xu, Mingchu; Li, Yumei; Birch, David G; Daiger, Stephen P

    2017-05-01

    To identify the causes of autosomal dominant retinitis pigmentosa (adRP) in a cohort of families without mutations in known adRP genes and consequently to characterize a novel dominant-acting missense mutation in SAG. Patients underwent ophthalmologic testing and were screened for mutations using targeted-capture and whole-exome next-generation sequencing. Confirmation and additional screening were done by Sanger sequencing. Haplotypes segregating with the mutation were determined using short tandem repeat and single nucleotide variant polymorphisms. Genealogies were established by interviews of family members. Eight families in a cohort of 300 adRP families, and four additional families, were found to have a novel heterozygous mutation in the SAG gene, c.440G>T; p.Cys147Phe. Patients exhibited symptoms of retinitis pigmentosa and none showed symptoms characteristic of Oguchi disease. All families are of Hispanic descent and most were ascertained in Texas or California. A single haplotype including the SAG mutation was identified in all families. The mutation dramatically alters a conserved amino acid, is extremely rare in global databases, and was not found in 4000+ exomes from Hispanic controls. Molecular modeling based on the crystal structure of bovine arrestin-1 predicts protein misfolding/instability. This is the first dominant-acting mutation identified in SAG, a founder mutation possibly originating in Mexico several centuries ago. The phenotype is clearly adRP and is distinct from the previously reported phenotypes of recessive null mutations, that is, Oguchi disease and recessive RP. The mutation accounts for 3% of the 300 families in the adRP Cohort and 36% of Hispanic families in this cohort.

  16. Three-Level AC-DC-AC Z-Source Converter Using Reduced Passive Component Count

    DEFF Research Database (Denmark)

    Loh, Poh Chiang; Gao, Feng; Tan, Pee-Chin

    2009-01-01

    of semiconductor commutations, and hence, no increase in switching losses. The proposed converter therefore offers a low-cost alternative to applications that need to ride through frequent input voltage sags. For confirming the converter performance, experimental testing using a constructed laboratory prototype......This paper presents a three-level ac-dc-ac Z-source converter with output voltage buck-boost capability. The converter is implemented by connecting a low-cost front-end diode rectifier to a neutral-point-clamped inverter through a single X-shaped LC impedance network. The inverter is controlled...... to switch with a three-level output voltage, where the middle neutral potential is uniquely tapped from the star-point of a wye-connected capacitive filter placed before the front-end diode rectifier for input current filtering. Through careful control, the resulting converter can produce the correct volt...

  17. Enhancing LVRT of DFIG by Using a Superconducting Current Limiter on Rotor Circuit

    Directory of Open Access Journals (Sweden)

    Flávio Oliveira

    2015-12-01

    Full Text Available This paper have studied the dynamic of a 2.0 MW Doubly Fed Induction Generator (DFIG during a severe voltage sag. Using the dynamic model of a DFIG, it was possible to determine the current, Electromagnetic Force and flux behavior during three-phase symmetrical voltage dip. Among the technologies of wind turbines the DFIG is widely employed; however, this machine is extremely susceptible to disturbances from the grid. In order to improve DFIG Low Voltage Ride-Through (LVRT, it is proposed a novel solution, using Superconducting Current Limiter (SCL in two arrangements: one, the SCL is placed between the machine rotor and the rotor side converter (RSC, and another placed in the RSC DC-link. The proposal is validated through simulation using PSCAD™/EMTDC™ and according to requirements of specific regulations. The analysis ensure that both SCL arrangements behave likewise, and are effective in decrement the rotor currents during the disturbance.

  18. Three-Level AC-DC-AC Z-Source Converter Using Reduced Passive Component Count

    DEFF Research Database (Denmark)

    Blaabjerg, Frede; Loh, Poh Chiang; Gao, Feng

    2007-01-01

    a low cost alternative to sensitive applications that need to ride-through frequent input voltage sags. For confirming the converter performance, experimental testing using a constructed laboratory prototype is performed with its captured results presented in a later section of the paper.......This paper presents a three-level ac-dc-ac Z-source converter with output voltage buck-boost capability. The converter is implemented by connecting a low cost front-end diode rectifier to a neutral-point-clamped inverter through a single X-shaped LC impedance network. The inverter is controlled...... to switch with a three-level output voltage, where the middle neutral potential is uniquely tapped from the star-point of a wye-connected capacitive filter placed before the front-end diode rectifier for input current filtering. Through careful control, the resulting converter can accurately produce...

  19. Failure of a vaccine using immunogenic recombinant proteins rNcSAG4 and rNcGRA7 against neosporosis in mice.

    Science.gov (United States)

    Aguado-Martínez, Adriana; Alvarez-García, Gema; Fernández-García, Aurora; Risco-Castillo, Verónica; Marugán-Hernández, Virginia; Ortega-Mora, Luis M

    2009-12-09

    The development of an effective vaccine against Neospora caninum infection in cattle is an important issue due to the significant economic impact of this parasitic disease worldwide. In this work, the immune response, safety and efficacy of different vaccine formulations using the N. caninum recombinant proteins rNcSAG4 (the first bradyzoite-specific protein assayed as a vaccine) and rNcGRA7 were evaluated in mouse models. The survival curves of pups from all vaccinated groups showed a slight delay in time to death compared to control groups; this difference was statistically significant for rNcSAG4+adjuvant group. Immune response of mice vaccinated with rNcSAG4 was characterized by reduced specific IgG and cytokine levels with an equilibrated IFN-gamma/IL-10 balance. Regarding mice vaccinated with rNcGRA7, a very strong humoral and cellular immune response was generated characterized by a hyper-production of IFN-gamma. This response was not accompanied by significant protection. Vaccination with a mixture of both recombinant proteins reduced infection in lung and brain during acute and chronic infection, respectively, although it was not statistically significant. In summary, no significant protection was obtained with these vaccine formulations in the present mouse models. However, the study reveals some positive results on immune response and efficacy for both recombinant proteins; these results are being discussed in order to suggest new approaches with new chronic infection mouse models and adjuvants.

  20. Thermal-history reconstruction of the Baiyun Sag in the deep-water area of the Pearl River Mouth Basin, northern South China Sea

    Science.gov (United States)

    Tang, Xiaoyin; Yang, Shuchun; Hu, Shengbiao

    2017-11-01

    The Baiyun Sag, located in the deep-water area of the northern South China Sea, is the largest and deepest subbasin in the Pearl River Mouth Basin and one of the most important hydrocarbon-accumulation depression areas in China. Thermal history is widely thought to be of great importance in oil and gas potential assessment of a basin as it controls the timing of hydrocarbon generation and expulsion from the source rock. In order to unravel the paleo-heat flow of the Baiyun Sag, we first analyzed tectonic subsidence of 55 pseudo-wells constructed based on newly interpreted seismic profiles, along with three drilled wells. We then carried out thermal modeling using the multi-stage finite stretching method and calibrated the results using collected present-day vitrinite reflectance data and temperature data. Results indicate that the first and second heating of the Baiyun Sag after 49 Ma ceased at 33.9 Ma and 23 Ma. Reconstructed average basal paleoheat flow values at the end of the rifting periods are 57.7-86.2 mW/m2 and 66.7-97.3 mW/m2, respectively. Following the last heating period at 23 Ma, the study area has undergone a persistent thermal attenuation phase, and basal heat flow has cooled down to 64.0-79.2 mW/m2 at present.

  1. Gene Cloning of 30 kDa Toxoplasma gondii Tachyzoites Surface An¬tigen (SAG1

    Directory of Open Access Journals (Sweden)

    L Maghen

    2007-05-01

    Full Text Available Background: Toxoplasma gondii is an obligate intracellular parasite and its sexual and asexual cycles, respectively take place in the intestinal epithelial cell of definitive host and tissue of intermediate hosts. Congenital toxoplasmosis is more impor¬tant when the mother acquired the infection during pregnancy period for the first time. Serological tests are the only meth¬ods for diagnosis of toxoplasmosis. Among serological tests, ELISA has specific value and availability of parasite spe¬cific anti¬gen increases the specificity of test. This study has designed and performed in the aim of availability to specific anti¬gen of Toxoplasma. Methods: A pair of forward and reverse primers was designed based on published sequence of T. gondii SAG1 gene. PCR reac¬tion was performed and PCR product was cloned in the pQE-30 expression vector. Results: The gene of 30 kDa protein of Toxoplasma tachyzoites was cloned in expression vector successfully. Recombinant plas¬mid was confirmed and is ready to express recombinant protein for further studies. Conclusion: In this research we cloned P30 gene of T. gondii tachyzoites surface protein successfully and is ready to ex¬press the recom¬binant protein.

  2. Voltage Sensors Monitor Harmful Static

    Science.gov (United States)

    2009-01-01

    A tiny sensor, small enough to be worn on clothing, now monitors voltage changes near sensitive instruments after being created to alert Agency workers to dangerous static buildup near fuel operations and avionics. San Diego s Quasar Federal Systems received a Small Business Innovation Research (SBIR) contract from Kennedy Space Center to develop its remote voltage sensor (RVS), a dime-sized electrometer designed to measure triboelectric changes in the environment. One of the unique qualities of the RVS is that it can detect static at greater distances than previous devices, measuring voltage changes from a few centimeters to a few meters away, due to its much-improved sensitivity.

  3. Power-MOSFET Voltage Regulator

    Science.gov (United States)

    Miller, W. N.; Gray, O. E.

    1982-01-01

    Ninety-six parallel MOSFET devices with two-stage feedback circuit form a high-current dc voltage regulator that also acts as fully-on solid-state switch when fuel-cell out-put falls below regulated voltage. Ripple voltage is less than 20 mV, transient recovery time is less than 50 ms. Parallel MOSFET's act as high-current dc regulator and switch. Regulator can be used wherever large direct currents must be controlled. Can be applied to inverters, industrial furnaces photovoltaic solar generators, dc motors, and electric autos.

  4. voltage compensation using artificial neural network

    African Journals Online (AJOL)

    Offor Theophilos

    VOLTAGE COMPENSATION USING ARTIFICIAL NEURAL NETWORK: A CASE STUDY OF. RUMUOLA ... using artificial neural network (ANN) controller based dynamic voltage restorer (DVR). ... substation by simulating with sample of average voltage for Omerelu, Waterlines, Rumuola, Shell Industrial and Barracks.

  5. Voltage Controlled Perpendicular Magnetic Anisotropy.

    Science.gov (United States)

    Noviasky, Nicholas; Sabirianov, Ildar; Cao, Shi; Zhang, Xiaozhe; Sokolov, Andrei; Kirianov, Eugene; Dowben, Peter; Ilie, Carolina C.; University of Nebraska at Lincoln Team; State University of New York at Oswego Collaboration

    Here we report the voltage controlled perpendicular magnetic anisotropy of a multilayer stack composed of P-type silicon substrate/ Gd2O3/ Co/ Pt grown by pulsed laser deposition (PLD) under ultra-high vacuum conditions. For examination of the voltage effect on magnetic properties of the samples, we performed magneto optical Kerr effect (MOKE) measurements. The results show a clear inverse relationship between voltage and coercivity. The exchange of oxygen ions which occurs at the interface between gadolinium oxide and cobalt may increase the cobalt oxide concentration within the optical interface layer. One potential application for this research could be the creation of a voltage controlled magnetic tunneling junction memory storage device. Proper implementation may be able to combine non-volatility with higher areal densities and low power consumption. NSF Research Experience for Faculty and Students at Undergraduate Institutions Program, UNL- MRSEC.

  6. Modular High Voltage Power Supply

    Energy Technology Data Exchange (ETDEWEB)

    Newell, Matthew R. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-05-18

    The goal of this project is to develop a modular high voltage power supply that will meet the needs of safeguards applications and provide a modular plug and play supply for use with standard electronic racks.

  7. Medium voltage substation insulation coordination

    Energy Technology Data Exchange (ETDEWEB)

    Caccia, M.; Gambirasio, D. (SAE Sadelmi, Milan (Italy))

    1991-01-01

    With reference to the provisions contained in applicable CEI (Italian Electrotechnical Committee) and IEC (International Electrotechnical Commission) normatives, a review is made of design criteria for the coordination of medium voltage substation switchgear and control gear. The design problematics are discussed with reference to optimization of neutral grounding, three phase ac short circuit calculation methods, and methods for the evaluation of voltages in fault conditions.

  8. Reliability criteria for voltage stability

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, Carson W.; Silverstein, Brian L. [Bonneville Power Administration, Portland, OR (United States)

    1994-12-31

    In face of costs pressures, there is need to allocate scare resources more effectively in order to achieve voltage stability. This naturally leads to development of probabilistic criteria and notions of rick management. In this paper it is presented a discussion about criteria for long term voltage stability limited to the case in which the time frames are topically several minutes. (author) 14 refs., 1 fig.

  9. Electro-optical voltage transformer

    Science.gov (United States)

    Xu, Yan; Ye, Miaoyuan; Cui, Ying

    1999-02-01

    The work introduces an optical fiber voltage transformer based on the Pockels effect. The transformer is different from a conventional electric-magnetic voltage transformer. A crystal BGO is used as sensor that is sealed in SF6 gas container; the measured signal is transferred by optical fiber in the Electro-Optical Voltage Transformer (EOVT). The principles and composition of EOVT is described here. The system consists of three parts: capacitive divider, optical sensor and electronics module. According to the analysis of factors that influence on the accuracy of measurement, the main ones, temperature and pressure of SF6, are corrected by means of signal digital process. The performances of 110kV EOVT were tested. The results show that the accuracy of EOVT could achieve 0.5 percent. Compared to a conventional electric-magnetic voltage transformer, the advantages of 110kV EOVT are higher accuracy, low cost, small volume, excellent dynamic characteristics and immunity from electromagnetic interference. In particular the low voltage is effectively isolated from the high voltage by means of the optical fiber.

  10. Unbalanced Voltage Compensation in Low Voltage Residential AC Grids

    DEFF Research Database (Denmark)

    Trintis, Ionut; Douglass, Philip; Munk-Nielsen, Stig

    2016-01-01

    This paper describes the design and test of a control algorithm for active front-end rectifiers that draw power from a residential AC grid to feed heat pump loads. The control algorithm is able to control the phase to neutral or phase to phase RMS voltages at the point of common coupling. The vol......This paper describes the design and test of a control algorithm for active front-end rectifiers that draw power from a residential AC grid to feed heat pump loads. The control algorithm is able to control the phase to neutral or phase to phase RMS voltages at the point of common coupling....... The voltage control was evaluated with either active or reactive independent phase load current control. The control performance in field operation in a residential grid situated in Bornholm, Denmark was investigated for different use cases....

  11. Electrode voltage fall and total voltage of a transient arc

    Science.gov (United States)

    Valensi, F.; Ratovoson, L.; Razafinimanana, M.; Masquère, M.; Freton, P.; Gleizes, A.

    2016-06-01

    This paper deals with an experimental study of the components of a transient arc total voltage with duration of a few tens of ms and a current peak close to 1000 A. The cathode tip is made of graphite whereas the flat anode is made either of copper or of graphite; the electrodes gap is a few mm. The analysis of the electrical parameters is supported and validated by fast imaging and by two models: the first one is a 2D physical model of the arc allowing to calculate both the plasma temperature field and the arc voltage; the second model is able to estimate the transient heating of the graphite electrode. The main aim of the study was to detect the possible change of the cathode voltage fall (CVF) during the first instants of the arc. Indeed it is expected that during the first ms the graphite cathode is rather cool and the main mechanism of the electron emission should be the field effect emission, whereas after several tens of ms the cathode is strongly heated and thermionic emission should be predominant. We have observed some change in the apparent CVF but we have shown that this apparent change can be attributed to the variation of the solid cathode resistance. On the other hand, the possible change of CVF corresponding to the transition between a ‘cold’ and a ‘hot’ cathode should be weak and could not be characterized considering our measurement uncertainty of about 2 V. The arc column voltage (ACV) was estimated by subtracting the electrode voltage fall from the total arc voltage. The experimental transient evolution of the ACV is in very good agreement with the theoretical variation predicted by the model, showing the good ability of the model to study this kind of transient arc.

  12. Automated Voltage Control in LHCb

    CERN Document Server

    Granado Cardoso, L; Jacobsson, R

    2011-01-01

    LHCb is one of the 4 LHC experiments. In order to ensure the safety of the detector and to maximize efficiency, LHCb needs to coordinate its own operations, in particular the voltage configuration of the different subdetectors, according to the accelerator status. A control software has been developed for this purpose, based on the Finite State Machine toolkit and the SCADA system used for control throughout LHCb (and the other LHC experiments). This software permits to efficiently drive both the Low Voltage (LV) and High Voltage (HV) systems of the 10 different sub-detectors that constitute LHCb, setting each sub-system to the required voltage (easily configurable at run-time) based on the accelerator state. The control software is also responsible for monitoring the state of the Sub-detector voltages and adding it to the event data in the form of status-bits. Safe and yet flexible operation of the LHCb detector has been obtained and automatic actions, triggered by the state changes of the ...

  13. Development of a New Cascade Voltage-Doubler for Voltage Multiplication

    Directory of Open Access Journals (Sweden)

    Arash Toudeshki

    2014-01-01

    Full Text Available For more than eight decades, cascade voltage-doubler circuits are used as a method to produce DC output voltage higher than the input voltage. In this paper, the topological developments of cascade voltage-doublers are reviewed. A new circuit configuration for cascade voltage-doubler is presented. This circuit can produce a higher value of the DC output voltage and better output quality compared to the conventional cascade voltage-doubler circuits, with the same number of stages.

  14. Development of a New Cascade Voltage-Doubler for Voltage Multiplication

    OpenAIRE

    Toudeshki, Arash; Mariun, Norman; Hizam, Hashim; Abdul Wahab, Noor Izzri

    2014-01-01

    For more than eight decades, cascade voltage-doubler circuits are used as a method to produce DC output voltage higher than the input voltage. In this paper, the topological developments of cascade voltage-doublers are reviewed. A new circuit configuration for cascade voltage-doubler is presented. This circuit can produce a higher value of the DC output voltage and better output quality compared to the conventional cascade voltage-doubler circuits, with the same number of stages.

  15. Low-Energy Real-Time OS Using Voltage Scheduling Algorithm for Variable Voltage Processors

    OpenAIRE

    Okuma, Takanori; Yasuura, Hiroto

    2001-01-01

    This paper presents a real-time OS based on $ mu $ITRON using proposed voltage scheduling algorithm for variable voltage processors which can vary supply voltage dynamically. The proposed voltage scheduling algorithms assign voltage level for each task dynamically in order to minimize energy consumption under timing constraints. Using the presented real-time OS, running tasks with low supply voltage leads to drastic energy reduction. In addition, the presented voltage scheduling algorithm is ...

  16. Voltage Quality of Grid Connected Wind Turbines

    DEFF Research Database (Denmark)

    Chen, Zhe; Blaabjerg, Frede; Sun, Tao

    2004-01-01

    Grid connected wind turbines may cause quality problems, such as voltage variation and flicker. This paper discusses the voltage variation and flicker emission of grid connected wind turbines with doubly-fed induction generators. A method to compensate flicker by using a voltage source converter...... (VSC) based STATCOM is presented, which shows it is an efficient mean to improve voltage quality....

  17. Portable High Voltage Impulse Generator

    Directory of Open Access Journals (Sweden)

    S. Gómez

    2011-06-01

    Full Text Available This paper presents a portable high voltage impulse generator which was designed and built with insulation up to 20 kV. This design was based on previous work in which simulation software for standard waves was developed. Commercial components and low-cost components were used in this work; however, these particular elements are not generally used for high voltage applications. The impulse generators used in industry and laboratories are usually expensive; they are built to withstand extra high voltage and they are big, making them impossible to transport. The proposed generator is portable, thereby allowing tests to be made on devices that cannot be moved from their location. The results obtained with the proposed impulse generator were satisfactory in terms of time and waveforms compared to other commercial impulse generators and the standard impulse wave simulator.

  18. Voltage Control of Magnetic Anisotropy

    Science.gov (United States)

    Hao, Guanhua; Cao, Shi; Noviasky, Nick; Ilie, Carolina; Sokolov, Andre; Yin, Yuewei; Xu, Xiaoshan; Dowben, Peter

    Pd/Co/Gd2O3/Si heterostructures were fabricated via pulsed laser deposition and e-beam evaporation. Hysteresis loops, obtained by longitudinal magneto-optical Kerr-effect (MOKE) measurements, indicates an initial in-plane magnetic anisotropy. Applying a perpendicular voltage on the sample, the differences between the polar and longitudinal MOKE and anomalous Hall effect data indicates there is a reversible change in magnetic anisotropy, from in-plane to out-of-plane, with applied voltage. Prior work by others suggests that the change in magnetic anisotropy is due to redox reactions at the Co/Gd2O3 interference. Voltage controlled magnetism can result from changing interfacial chemistry and does not always require a magneto-electric coupling tensor.

  19. Resilient architecture design for voltage variation

    CERN Document Server

    Reddi, Vijay Janapa

    2013-01-01

    Shrinking feature size and diminishing supply voltage are making circuits sensitive to supply voltage fluctuations within the microprocessor, caused by normal workload activity changes. If left unattended, voltage fluctuations can lead to timing violations or even transistor lifetime issues that degrade processor robustness. Mechanisms that learn to tolerate, avoid, and eliminate voltage fluctuations based on program and microarchitectural events can help steer the processor clear of danger, thus enabling tighter voltage margins that improve performance or lower power consumption. We describe

  20. A new analysis of Mars "Special Regions": findings of the second MEPAG Special Regions Science Analysis Group (SR-SAG2).

    Science.gov (United States)

    Rummel, John D; Beaty, David W; Jones, Melissa A; Bakermans, Corien; Barlow, Nadine G; Boston, Penelope J; Chevrier, Vincent F; Clark, Benton C; de Vera, Jean-Pierre P; Gough, Raina V; Hallsworth, John E; Head, James W; Hipkin, Victoria J; Kieft, Thomas L; McEwen, Alfred S; Mellon, Michael T; Mikucki, Jill A; Nicholson, Wayne L; Omelon, Christopher R; Peterson, Ronald; Roden, Eric E; Sherwood Lollar, Barbara; Tanaka, Kenneth L; Viola, Donna; Wray, James J

    2014-11-01

    A committee of the Mars Exploration Program Analysis Group (MEPAG) has reviewed and updated the description of Special Regions on Mars as places where terrestrial organisms might replicate (per the COSPAR Planetary Protection Policy). This review and update was conducted by an international team (SR-SAG2) drawn from both the biological science and Mars exploration communities, focused on understanding when and where Special Regions could occur. The study applied recently available data about martian environments and about terrestrial organisms, building on a previous analysis of Mars Special Regions (2006) undertaken by a similar team. Since then, a new body of highly relevant information has been generated from the Mars Reconnaissance Orbiter (launched in 2005) and Phoenix (2007) and data from Mars Express and the twin Mars Exploration Rovers (all 2003). Results have also been gleaned from the Mars Science Laboratory (launched in 2011). In addition to Mars data, there is a considerable body of new data regarding the known environmental limits to life on Earth-including the potential for terrestrial microbial life to survive and replicate under martian environmental conditions. The SR-SAG2 analysis has included an examination of new Mars models relevant to natural environmental variation in water activity and temperature; a review and reconsideration of the current parameters used to define Special Regions; and updated maps and descriptions of the martian environments recommended for treatment as "Uncertain" or "Special" as natural features or those potentially formed by the influence of future landed spacecraft. Significant changes in our knowledge of the capabilities of terrestrial organisms and the existence of possibly habitable martian environments have led to a new appreciation of where Mars Special Regions may be identified and protected. The SR-SAG also considered the impact of Special Regions on potential future human missions to Mars, both as locations of

  1. Usefulness of rNcGRA7- and rNcSAG4-based ELISA tests for distinguishing primo-infection, recrudescence, and chronic bovine neosporosis.

    Science.gov (United States)

    Aguado-Martínez, A; Alvarez-García, G; Fernández-García, A; Risco-Castillo, V; Arnaiz-Seco, I; Rebordosa-Trigueros, X; Navarro-Lozano, V; Ortega-Mora, L M

    2008-11-07

    Bovine reproductive failure caused by the parasite Neospora caninum is a major problem and is responsible for severe economic losses worldwide. Currently, appropriate control measures depend on the predominant transmission route in a particular herd. Therefore, the development of diagnostic tools capable of discriminating between primo-infection, recrudescence, re-infection, and chronic infection is a major challenge in the serodiagnosis of bovine neosporosis. Here, two recombinant protein-based ELISAs utilizing the immunodominant NcGRA7 dense granule protein and the NcSAG4 bradyzoite stage-specific protein were developed and showed good diagnostic performances. Their usefulness for discerning between primo-infection, recrudescence, re-infection, and chronic infection was also studied by analyzing an appropriate panel of serum samples belonging to different groups of experimentally and naturally infected bovines. Our results suggest that anti-rNcGRA7 antibody levels may be indicative of acute infection (primo-infection, re-infection, and recrudescence), whereas the presence of anti-rNcSAG4 antibodies may be associated with chronic infection and could be a good indicator of infection establishment (tachyzoite-bradyzoite conversion). Moreover, primo-infection associated with a Neospora-associated epidemic abortion pattern is characterized by the detection of anti-rNcGRA7 antibodies together with the absence or detection of anti-rNcSAG4 antibody levels around the cut-off point. In contrast, the detection of antibody levels directed against both recombinant proteins may be quite indicative of recrudescence or re-infection associated with abortion and/or vertical transmission in herds with a Neospora-associated endemic abortion pattern. In conclusion, both serological tests developed in the present study offer additional information to conventional avidity tests and, consequently, improve the diagnosis of bovine neosporosis with perspectives for control measures.

  2. Physical simulation of gas reservoir formation in the Liwan 3-1 deep-water gas field in the Baiyun sag, Pearl River Mouth Basin

    Directory of Open Access Journals (Sweden)

    Gang Gao

    2015-01-01

    Full Text Available To figure out the process and controlling factors of gas reservoir formation in deep-waters, based on an analysis of geological features, source of natural gas and process of reservoir formation in the Liwan 3-1 gas field, physical simulation experiment of the gas reservoir formation process has been performed, consequently, pattern and features of gas reservoir formation in the Baiyun sag has been found out. The results of the experiment show that: ① the formation of the Liwan 3-1 faulted anticline gas field is closely related to the longstanding active large faults, where natural gas is composed of a high proportion of hydrocarbons, a small amount of non-hydrocarbons, and the wet gas generated during highly mature stage shows obvious vertical migration signs; ② liquid hydrocarbons associated with natural gas there are derived from source rock of the Enping & Zhuhai Formation, whereas natural gas comes mainly from source rock of the Enping Formation, and source rock of the Wenchang Formation made a little contribution during the early Eocene period as well; ③ although there was gas migration and accumulation, yet most of the natural gas mainly scattered and dispersed due to the stronger activity of faults in the early period; later as fault activity gradually weakened, gas started to accumulate into reservoirs in the Baiyun sag; ④ there is stronger vertical migration of oil and gas than lateral migration, and the places where fault links effective source rocks with reservoirs are most likely for gas accumulation; ⑤ effective temporal-spatial coupling of source-fault-reservoir in late stage is the key to gas reservoir formation in the Baiyun sag; ⑥ the nearer the distance from a trap to a large-scale fault and hydrocarbon source kitchen, the more likely gas may accumulate in the trap in late stage, therefore gas accumulation efficiency is much lower for the traps which are far away from large-scale faults and hydrocarbon source

  3. Capacitor Voltages Measurement and Balancing in Flying Capacitor Multilevel Converters Utilizing a Single Voltage Sensor

    DEFF Research Database (Denmark)

    Farivar, Glen; Ghias, Amer M. Y. M.; Hredzak, Branislav

    2017-01-01

    This paper proposes a new method for measuring capacitor voltages in multilevel flying capacitor (FC) converters that requires only one voltage sensor per phase leg. Multiple dc voltage sensors traditionally used to measure the capacitor voltages are replaced with a single voltage sensor at the ac...

  4. Two Generations of Detachment System in an Aborted Hyper-extended Rift Basin: A Case in the Baiyun Sag, northern South China Sea

    Science.gov (United States)

    Zhou, Z.; Mei, L.; Liu, J.; Chen, L.; Zheng, J.

    2016-12-01

    Three episodes of rifting started from the latest Cretaceous and contributed to final breakup of the South China Sea in Early Oligocene. The Baiyun Sag developed in the continental slope of northern South China Sea was supposed to be only affected by the second and third rifting events and defined as a hyper-extended rift basin with extremely thinned crust through a deep seismic reflection profile by former researchers. In this paper, 19 supplementary deep seismic images were used to investigate the deep crustal structure. The results suggest that only 4-km-thick continental crust is preserved in the middle of the Baiyun Sag, whereas about 26-km-thick in the adjacent relatively unextended regions, such as Panyu Low Uplift in the north and Shunhe Uplift in the southwest. Furthermore, recently gathered 2D/3D offshore seismic data almost cover the whole research region, allowing us to recognize a Cenozoic detachment system which consists of six major detachment faults. In contrast to the performance of the distal domains in the Iberia and Mid-Norway rifted margins, all of these detachment faults dipped toward the continent and thinned the crust effectively, indicating that the extension of the Baiyun Sag was independent of the future lithospheric breakup zone. Consequently, we define the Baiyun Sag as an aborted hyper-extended rift basin formed during Paleocene to Early Oligocene. The inherited basement structures will clearly influence the evolution process of new born rift basin. Under the top basement, a pre-Cenozoic detachment system is also well described in our research area and act as a series of surface with strong amplitude in seismic imaging. We argue that the Cenozoic detachment system was built on the basis of the pre-rift detachment system which is speculated to have formed in the Late Cretaceous. Extensional style of a conveyor belt is recognized in this sediment-rich, aborted hyper-extended supra-detachment basin, showing that the breakaway blocks or

  5. Physical simulation of gas reservoir formation in the Liwan 3-1 deep-water gas field in the Baiyun sag, Pearl River Mouth Basin

    OpenAIRE

    Gao, Gang; Gang, Wenzhe; Zhang, Gongcheng; He, Wenjun; Cui, Xin; Shen, Huailei; Miao, Shunde

    2015-01-01

    To figure out the process and controlling factors of gas reservoir formation in deep-waters, based on an analysis of geological features, source of natural gas and process of reservoir formation in the Liwan 3-1 gas field, physical simulation experiment of the gas reservoir formation process has been performed, consequently, pattern and features of gas reservoir formation in the Baiyun sag has been found out. The results of the experiment show that: ① the formation of the Liwan 3-1 faulted an...

  6. FLC based adjustable speed drives for power quality enhancement

    Directory of Open Access Journals (Sweden)

    Sukumar Darly

    2010-01-01

    Full Text Available This study describes a new approach based on fuzzy algorithm to suppress the current harmonic contents in the output of an inverter. Inverter system using fuzzy controllers provide ride-through capability during voltage sags, reduces harmonics, improves power factor and high reliability, less electromagnetic interference noise, low common mode noise and extends output voltage range. A feasible test is implemented by building a model of three-phase impedance source inverter, which is designed and controlled on the basis of proposed considerations. It is verified from the practical point of view that these new approaches are more effective and acceptable to minimize the harmonic distortion and improves the quality of power. Due to the complex algorithm, their realization often calls for a compromise between cost and performance. The proposed optimizing strategies may be applied in variable-frequency dc-ac inverters, UPSs, and ac drives.

  7. Voltage control of ferromagnetic resonance

    Directory of Open Access Journals (Sweden)

    Ziyao Zhou

    2016-06-01

    Full Text Available Voltage control of magnetism in multiferroics, where the ferromagnetism and ferroelectricity are simultaneously exhibiting, is of great importance to achieve compact, fast and energy efficient voltage controllable magnetic/microwave devices. Particularly, these devices are widely used in radar, aircraft, cell phones and satellites, where volume, response time and energy consumption is critical. Researchers realized electric field tuning of magnetic properties like magnetization, magnetic anisotropy and permeability in varied multiferroic heterostructures such as bulk, thin films and nanostructure by different magnetoelectric (ME coupling mechanism: strain/stress, interfacial charge, spin–electromagnetic (EM coupling and exchange coupling, etc. In this review, we focus on voltage control of ferromagnetic resonance (FMR in multiferroics. ME coupling-induced FMR change is critical in microwave devices, where the electric field tuning of magnetic effective anisotropic field determines the tunability of the performance of microwave devices. Experimentally, FMR measurement technique is also an important method to determine the small effective magnetic field change in small amount of magnetic material precisely due to its high sensitivity and to reveal the deep science of multiferroics, especially, voltage control of magnetism in novel mechanisms like interfacial charge, spin–EM coupling and exchange coupling.

  8. Nonlinear electrokinetics at large voltages

    Energy Technology Data Exchange (ETDEWEB)

    Bazant, Martin Z [Department of Chemical Engineering and Institute for Soldier Nanotechnologies, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Sabri Kilic, Mustafa; Ajdari, Armand [Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Storey, Brian D [Franklin W Olin College of Engineering, Needham, MA 02492 (United States)], E-mail: bazant@mit.edu

    2009-07-15

    The classical theory of electrokinetic phenomena assumes a dilute solution of point-like ions in chemical equilibrium with a surface whose double-layer voltage is of order the thermal voltage, k{sub B}T/e=25 mV. In nonlinear 'induced-charge' electrokinetic phenomena, such as ac electro-osmosis, several volts {approx}100k{sub B}T/e are applied to the double layer, and the theory breaks down and cannot explain many observed features. We argue that, under such a large voltage, counterions 'condense' near the surface, even for dilute bulk solutions. Based on simple models, we predict that the double-layer capacitance decreases and the electro-osmotic mobility saturates at large voltages, due to steric repulsion and increased viscosity of the condensed layer, respectively. The former suffices to explain observed high-frequency flow reversal in ac electro-osmosis; the latter leads to a salt concentration dependence of induced-charge flows comparable to experiments, although a complete theory is still lacking.

  9. High-Voltage Droplet Dispenser

    Science.gov (United States)

    Eichenberg, Dennis J.

    2003-01-01

    An apparatus that is extremely effective in dispensing a wide range of droplets has been developed. This droplet dispenser is unique in that it utilizes a droplet bias voltage, as well as an ionization pulse, to release a droplet. Apparatuses that deploy individual droplets have been used in many applications, including, notably, study of combustion of liquid fuels. Experiments on isolated droplets are useful in that they enable the study of droplet phenomena under well-controlled and simplified conditions. In this apparatus, a syringe dispenses a known value of liquid, which emerges from, and hangs onto, the outer end of a flat-tipped, stainless steel needle. Somewhat below the needle tip and droplet is a ring electrode. A bias high voltage, followed by a high-voltage pulse, is applied so as to attract the droplet sufficiently to pull it off the needle. The voltages are such that the droplet and needle are negatively charged and the ring electrode is positively charged.

  10. Voltage Weak DC Distribution Grids

    NARCIS (Netherlands)

    Hailu, T.G.; Mackay, L.J.; Ramirez Elizondo, L.M.; Ferreira, J.A.

    2017-01-01

    This paper describes the behavior of voltage weak DC distribution systems. These systems have relatively small system capacitance. The size of system capacitance, which stores energy, has a considerable effect on the value of fault currents, control complexity, and system reliability. A number of

  11. (SPWM) Voltage Source Inverter (VSI)

    African Journals Online (AJOL)

    The quest to achieve less-distorted dc-ac power conversion has resulted in the proliferation of many multilevel inverter configurations. This paper presents an experimental report of a simplified topology for single-phase, SPWM, three-level voltage source inverter wit R-L load. To keep the power circuit component count to a ...

  12. High voltage MOSFET switching circuit

    Science.gov (United States)

    McEwan, Thomas E.

    1994-01-01

    The problem of source lead inductance in a MOSFET switching circuit is compensated for by adding an inductor to the gate circuit. The gate circuit inductor produces an inductive spike which counters the source lead inductive drop to produce a rectangular drive voltage waveform at the internal gate-source terminals of the MOSFET.

  13. Voltage-gated Proton Channels

    Science.gov (United States)

    DeCoursey, Thomas E.

    2014-01-01

    Voltage-gated proton channels, HV1, have vaulted from the realm of the esoteric into the forefront of a central question facing ion channel biophysicists, namely the mechanism by which voltage-dependent gating occurs. This transformation is the result of several factors. Identification of the gene in 2006 revealed that proton channels are homologues of the voltage-sensing domain of most other voltage-gated ion channels. Unique, or at least eccentric, properties of proton channels include dimeric architecture with dual conduction pathways, perfect proton selectivity, a single-channel conductance ~103 smaller than most ion channels, voltage-dependent gating that is strongly modulated by the pH gradient, ΔpH, and potent inhibition by Zn2+ (in many species) but an absence of other potent inhibitors. The recent identification of HV1 in three unicellular marine plankton species has dramatically expanded the phylogenetic family tree. Interest in proton channels in their own right has increased as important physiological roles have been identified in many cells. Proton channels trigger the bioluminescent flash of dinoflagellates, facilitate calcification by coccolithophores, regulate pH-dependent processes in eggs and sperm during fertilization, secrete acid to control the pH of airway fluids, facilitate histamine secretion by basophils, and play a signaling role in facilitating B-cell receptor mediated responses in B lymphocytes. The most elaborate and best-established functions occur in phagocytes, where proton channels optimize the activity of NADPH oxidase, an important producer of reactive oxygen species. Proton efflux mediated by HV1 balances the charge translocated across the membrane by electrons through NADPH oxidase, minimizes changes in cytoplasmic and phagosomal pH, limits osmotic swelling of the phagosome, and provides substrate H+ for the production of H2O2 and HOCl, reactive oxygen species crucial to killing pathogens. PMID:23798303

  14. Biological Mechanisms Underlying the Ultraviolet Radiation-Induced Formation of Skin Wrinkling and Sagging II: Over-Expression of Neprilysin Plays an Essential Role

    Directory of Open Access Journals (Sweden)

    Genji Imokawa

    2015-04-01

    Full Text Available Our previous studies strongly indicated that the up-regulated activity of skin fibroblast-derived elastase plays a pivotal role in wrinkling and/or sagging of the skin via the impairment of elastic fiber configuration and the subsequent loss of skin elasticity. Fortunately, we succeeded in identifying human skin fibroblast-derived elastase as a previously known enzyme, neprilysin or neutral endopeptidase (NEP. We have also characterized epithelial-mesenchymal paracrine cytokine interactions between UVB-exposed-keratinocytes and dermal fibroblasts and found that interleukin-1α and granulocyte macrophage colony stimulatory factor (GM-CSF are intrinsic cytokines secreted by UVB-exposed keratinocytes that stimulate the expression of neprilysin by fibroblasts. On the other hand, direct UVA exposure of human fibroblasts significantly stimulates the secretion of IL-6 and also elicits a significant increase in the gene expression of matrix metallo-protease(MMP-1 as well as neprilysin (to a lesser extent, which is followed by distinct increases in their protein and enzymatic activity levels. Direct UVA exposure of human keratinocytes also stimulates the secretion of IL-6, IL-8 and GM-CSF but not of IL-1 and endothelin-1. These findings suggest that GM-CSF secreted by UVA-exposed keratinocytes as well as IL-6 secreted by UVA-exposed dermal fibroblasts play important and additional roles in UVA-induced sagging and wrinkling by up-regulation of neprilysin and MMP-1, respectively, in dermal fibroblasts.

  15. Over-voltage protection system and method

    Science.gov (United States)

    Chi, Song; Dong, Dong; Lai, Rixin

    2017-05-02

    An over-voltage protection system includes an electronic valve connected across two terminals of a circuit and an over-voltage detection circuit connected across one of the plurality of semiconductor devices for detecting an over-voltage across the circuit. The electronic valve includes a plurality of semiconductor devices connected in series. The over-voltage detection circuit includes a voltage divider circuit connected to a break-over diode in a way to provide a representative low voltage to the break-over diode and an optocoupler configured to receive a current from the break-over diode when the representative low voltage exceeds a threshold voltage of the break-over diode indicating an over-voltage condition. The representative low voltage provided to the break-over diode represents a voltage across the one semiconductor device. A plurality of self-powered gate drive circuits are connected to the plurality of semiconductor devices, wherein the plurality of self-powered gate drive circuits receive over-voltage triggering pulses from the optocoupler during the over-voltage condition and switch on the plurality of semiconductor devices to bypass the circuit.

  16. TRANSISTOR HIGH VOLTAGE POWER SUPPLY

    Science.gov (United States)

    Driver, G.E.

    1958-07-15

    High voltage, direct current power supplies are described for use with battery powered nuclear detection equipment. The particular advantages of the power supply described, are increased efficiency and reduced size and welght brought about by the use of transistors in the circuit. An important feature resides tn the employment of a pair of transistors in an alternatefiring oscillator circuit having a coupling transformer and other circuit components which are used for interconnecting the various electrodes of the transistors.

  17. Advances in high voltage engineering

    CERN Document Server

    Haddad, A

    2005-01-01

    This book addresses the very latest research and development issues in high voltage technology and is intended as a reference source for researchers and students in the field, specifically covering developments throughout the past decade. This unique blend of expert authors and comprehensive subject coverage means that this book is ideally suited as a reference source for engineers and academics in the field for years to come.

  18. VOLTAGE REGULATORS OF SYNCHRONOUS GENERATORS

    OpenAIRE

    Grigorash O. V.; Korzenkov P. G.; Popuchieva M. A.

    2015-01-01

    Synchronous generators are the primary source of electrical power autonomous electrosupply systems, including backup systems. They are also used in a structure of rotating electricity converters and are widely used in renewable energy as part of wind power plants of small, mini and micro hydroelectric plants. Increasing the speed and the accuracy of the system of the voltage regulation of synchronous generators is possible due to the development of combined systems containing more stabilizers...

  19. Low voltage electron beam accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Ochi, Masafumi [Iwasaki Electric Co., Ltd., Tokyo (Japan)

    2003-02-01

    Widely used electron accelerators in industries are the electron beams with acceleration voltage at 300 kV or less. The typical examples are shown on manufactures in Japan, equipment configuration, operation, determination of process parameters, and basic maintenance requirement of the electron beam processors. New electron beam processors with acceleration voltage around 100 kV were introduced maintaining the relatively high dose speed capability of around 10,000 kGy x mpm at production by ESI (Energy Science Inc. USA, Iwasaki Electric Group). The application field like printing and coating for packaging requires treating thickness of 30 micron or less. It does not require high voltage over 110 kV. Also recently developed is a miniature bulb type electron beam tube with energy less than 60 kV. The new application area for this new electron beam tube is being searched. The drive force of this technology to spread in the industries would be further development of new application, process and market as well as the price reduction of the equipment, upon which further acknowledgement and acceptance of the technology to societies and industries would entirely depend. (Y. Tanaka)

  20. 49 CFR 234.221 - Lamp voltage.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Lamp voltage. 234.221 Section 234.221 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION..., Inspection, and Testing Maintenance Standards § 234.221 Lamp voltage. The voltage at each lamp shall be...

  1. Neuro-fuzzy-wavelet network for detection and classification of the voltage disturbances in electrical power system; Rede neuro-fuzzy-wavelet para deteccao e classificacao de anomalias de tensao em sistemas eletricos de potencia

    Energy Technology Data Exchange (ETDEWEB)

    Malange, Fernando C.V. [Universidade do Estado de Mato Grosso (UEMT), Caceres, MT (Brazil). Dept. de Computacao], E-mail: fmalange@gmail.com; Minussi, Carlos R. [Universidade Estadual Paulista (UNESP), Ilha Solteira, SP (Brazil). Dept. de Engenharia Eletrica], E-mail: minussi@dee.feis.unesp.br

    2009-07-01

    A methodology for identifying and classifying voltage disturbances (harmonics, voltage sag, etc.) using fuzzy ARTMAP neural networks is presented. It is an ART (adaptive resonance theory) architecture family neural network that presents the stability and plasticity properties, which are fundamental requests for developing a reliable electrical systems with reduced processing time. Stability means a guarantee of good solutions; plasticity allows realize the training without restart the system every time there are new patterns to be stored in a weight matrix of the neural network. The training is realized from the wave forms provided by the acquisition data system, using the wavelets theory to generate the coefficients that constitute the input patterns of the neural network. Results from simulations show that the accuracy index is nearly 100%. (author)

  2. 76 FR 70721 - Voltage Coordination on High Voltage Grids; Notice of Staff Workshop

    Science.gov (United States)

    2011-11-15

    ... Energy Regulatory Commission Voltage Coordination on High Voltage Grids; Notice of Staff Workshop Take notice that the Federal Energy Regulatory Commission will hold a Workshop on Voltage Coordination on High Voltage Grids on Thursday, December 1, 2011 from 9 a.m. to 4:30 p.m. This staff-led workshop will be held...

  3. 76 FR 72203 - Voltage Coordination on High Voltage Grids; Notice of Reliability Workshop Agenda

    Science.gov (United States)

    2011-11-22

    ... Energy Regulatory Commission Voltage Coordination on High Voltage Grids; Notice of Reliability Workshop... between voltage control, reliability, and economic dispatch. In addition, the Commission will consider how improvements to dispatch and voltage control software could improve reliability and market efficiency. This...

  4. Improving transition voltage spectroscopy of molecular junctions

    DEFF Research Database (Denmark)

    Markussen, Troels; Chen, Jingzhe; Thygesen, Kristian Sommer

    2011-01-01

    Transition voltage spectroscopy (TVS) is a promising spectroscopic tool for molecular junctions. The principles in TVS is to find the minimum on a Fowler-Nordheim plot where ln(I/V2) is plotted against 1/V and relate the voltage at the minimum Vmin to the closest molecular level. Importantly, Vmin...... is approximately half the voltage required to see a peak in the dI/dV curve. Information about the molecular level position can thus be obtained at relatively low voltages. In this work we show that the molecular level position can be determined at even lower voltages, Vmin(α), by finding the minimum of ln...

  5. Investigation of the physico-chemical and mechanical properties of hard brittle shales from the Shahejie Formation in the Nanpu Sag, northern China

    Science.gov (United States)

    Xiangjun, Liu; Jian, Xiong; Lixi, Liang; Yi, Ding

    2017-06-01

    With increasing demand for energy and advances in exploration and development technologies, more attention is being devoted to exploration and development of deep oil and gas reservoirs. The Nanpu Sag contains huge reserves in deep oil and gas reservoirs and is a promising area. In this paper, the physico-chemical and mechanical properties of hard brittle shales from the Shahejie Formation in the Nanpu Sag in the Bohai Bay Basin of northern China were investigated using a variety of methods, including x-ray diffraction analysis, cation exchange capacity (CEC) analysis, contact angle measurements, scanning electron microscope observations, immersion experiments, ultrasonic testing and mechanical testing. The effects of the physico-chemical properties of the shales on wellbore instability were observed, and the effects of hydration of the shales on wellbore instability were also examined. The results show that the major mineral constituents of the investigated shales are quartz and clay minerals. The clay mineral contents range from 25.33% to 52.03%, and the quartz contents range from 20.03% to 46.45%. The clay minerals do not include montmorillonite, but large amounts of mixed-layer illite/smectite were observed. The CEC values of the shales range from 90 to 210 mmol kg-1, indicating that the shales are partly hydrated. The wettability of the shales is strongly water-wetted, indicating that water would enter the shales due to the capillary effect. Hydration of hard brittle shales can generate cracks, leading to changes in microstructure and increases in the acoustic value, which could generate damage in the shales and reduce their strength. With increasing hydration time, the shale hydration effect gradually becomes stronger, causing an increase in the range of the acoustic travel time and decreases in the ranges of cohesion and internal friction angles. For the hard brittle shales of the Nanpu Sag, drilling fluid systems should aim to enhance sealing ability

  6. Fluids in the Palaeogene Formation of Gaoyou Sag in the Southern Part of North Jiangsu Basin, China: Evidence for Hydrocarbon Migration and Accumulation

    Science.gov (United States)

    LI, M.; Lou, Z.; Zhu, R.; Jin, A.

    2013-12-01

    Gaoyou Sag, lying in the middle of the Dongtai Depression in the North Jiangsu basin, China, has a well developed fault system and is characterised by structurally complicated oil and gas fields. Its oil-water relationship is very complicated. In the present study, we present the distribution of formation water chemistry, crude oil density, formation pressures and fluid potential in the Palaeogene formation of the Gaoyou Sag . The purpose of this article is to: (1) analyse the cause of hydrochemical diversity; (2) identify the flow pattern and evolution; and (3) understand the interplay between the flow of formation water and hydrocarbon migration and accumulation. The results showed that large variances in formation water chemistry occur in different oilfields of the Gaoyou Sag (Figure 1) due to dilution by meteoric water recharge, concentration by membrane filtration and complexity of geological structure. The low salinity (mean values from 8.53 g/L to 9.67 g/L) of the formation water and heavy crude oil density (up to 0.94g/cm3) in the Xuchuang oilfield indicate influence from meteoric water infiltration; the deep depression areas are mainly of connate origin. Geofluids in the Xuchuang, Zhenwu and Yang'an oilfields mainly flow vertically through the Zhenwu and Hanliu faults, while geofluids in the Shanian oilfield mainly migrate laterally through the reservoirs and are adjusted vertically along some cutting faults. Palaeo-hydrodynamic evolution had an affinity with the generation, migration, accumulation and preservation of hydrocarbons. In the depositional stages of the Dainan and Sanduo formations, formation water was expelled outward and upward from lacustrine mudstones of the deep depression into shallow sands of nearby oilfields, driven by compaction and overpressure. Hydrocarbon migrated with formation water and gathered in appropriate traps, forming primary reservoirs. During the Zhenwu and Sanduo movements, there were tectonic uplifts and the strata

  7. Low power, scalable multichannel high voltage controller

    Science.gov (United States)

    Stamps, James Frederick [Livermore, CA; Crocker, Robert Ward [Fremont, CA; Yee, Daniel Dadwa [Dublin, CA; Dils, David Wright [Fort Worth, TX

    2008-03-25

    A low voltage control circuit is provided for individually controlling high voltage power provided over bus lines to a multitude of interconnected loads. An example of a load is a drive for capillary channels in a microfluidic system. Control is distributed from a central high voltage circuit, rather than using a number of large expensive central high voltage circuits to enable reducing circuit size and cost. Voltage is distributed to each individual load and controlled using a number of high voltage controller channel switches connected to high voltage bus lines. The channel switches each include complementary pull up and pull down photo isolator relays with photo isolator switching controlled from the central high voltage circuit to provide a desired bus line voltage. Switching of the photo isolator relays is further controlled in each channel switch using feedback from a resistor divider circuit to maintain the bus voltage swing within desired limits. Current sensing is provided using a switched resistive load in each channel switch, with switching of the resistive loads controlled from the central high voltage circuit.

  8. Voltage Management in Unbalanced Low Voltage Networks Using a Decoupled Phase-Tap-Changer Transformer

    OpenAIRE

    Coppo, Massimiliano; Turri, Roberto; Marinelli, Mattia; Han, Xue

    2014-01-01

    The paper studies a medium voltage-low voltage transformer with a decoupled on load tap changer capability on each phase. The overall objective is the evaluation of the potential benefits on a low voltage network of such possibility. A realistic Danish low voltage network is used for the analysis. The load profiles are characterized by using single phase measurement data on voltages, currents and active powers with a 10 minutes resolution. Different scenarios are considered: no tap action, th...

  9. Determinación de la relación entre descargas atmosféricas y perturbaciones de corta duración (sags y sobretensiones)

    OpenAIRE

    Murillo Sánchez, Oscar Javier

    2012-01-01

    Se muestra el desarrollo y los resultados de una metodología propuesta para la determinación de la correlación entre descargas eléctricas atmosféricas detectadas y registradas en una zona y los hundimientos de tensión (sags) registrados en el sistema de distribución asociado. Como ejemplo de aplicación se usa información del sistema de localización de rayos WWLLN (wwlln.net), el Sistema de información de Descarga SID (propiedad de ISA. S.A. E.S.P.) y las mediciones de calidad de potencia de C...

  10. 49 CFR 236.551 - Power supply voltage; requirement.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Power supply voltage; requirement. 236.551 Section... supply voltage; requirement. The voltage of power supply shall be maintained within 10 percent of rated voltage. ...

  11. Wrench related faults and their control on the tectonics and Eocene sedimentation in the L13-L15 sub-sag area, Pearl River Mouth basin, China

    Science.gov (United States)

    Chen, Shuping; Xu, Shunshan; Cai, Yu; Ma, Xiaodan

    2017-09-01

    Recent oil discoveries in the L13-L15 sub-sag area in the Pearl River Mouth basin have inspired interest in Paleogene hydrocarbon targets. However, the structures and their control on reservoirs have not been completely studied. The aim of this paper is to address the tectonics and Eocene sedimentation based on 3D seismic data. We documented characteristics from four aspects of the faults in the study area: (a) fault arrangement; (b) fault segmentation; (c) flower structures; and (d) distribution of the depocenters along the faults. Based on the above data, we propose that the structures in the studied area were formed by a right-handed wrench. The principal shear for this model was caused by NNE- to NE-ward motion of the eastern part of the Eurasia plate due to the collision of the Indian-Australian and Eurasian plates starting approximately 49 Ma ago. The L13-L15 sub-sag area underwent early Eocene rifting, a late Eocene rifting-depression transition and an Oligocene-Quaternary thermal depression. The rift phase included three stages: the initial rifting, intensive rifting and late rifting. The deep lake mudstone deposited during the intensive rifting stage is the source rock with the most potential for oil generation. Shallow lake source rocks formed in the late rifting and transition stages are the secondary source rocks. Reservoir sweet spots were formed in the early period of the intensive rifting and late rifting stages. The junction sites between the front of the meandering river delta plain and fault steps are favorable places for good reservoirs. The sediments in the transition stage are rich in sandstone, making them perfect sites for prospecting reservoirs.

  12. Silicone elastomers with aromatic voltage stabilizers

    DEFF Research Database (Denmark)

    A Razak, Aliff Hisyam; Skov, Anne Ladegaard

    elastomers with high relative permittivity and low Young’s modulus in order to increase the actuation performance at a given voltage, but the optimised elastomers often possess relatively low electrical breakdown strength. On the other hand, increasing the electrical breakdown strength of DEs allows...... modifications. In order to increase the electrical breakdown strength of polymers for e.g. the cable industry, additives like aromatic voltage stabilizers are used. Earlier works on using voltage stabilizers in polymers have mainly focused on polyethylene with the purpose of reducing power loss for high voltage...... insulation cables.3–5 As an alternative to utilise additives as voltage stabilizers, grafting aromatic compounds to silicone backbones may overcome the common problem of insolubility of the aromatic voltage stabilizer in the silicone elastomers due to phase separation. Preventing phase separation during...

  13. Voltage-Controlled Floating Resistor Using DDCC

    Directory of Open Access Journals (Sweden)

    M. Kumngern

    2011-04-01

    Full Text Available This paper presents a new simple configuration to realize the voltage-controlled floating resistor, which is suitable for integrated circuit implementation. The proposed resistor is composed of three main components: MOS transistor operating in the non-saturation region, DDCC, and MOS voltage divider. The MOS transistor operating in the non-saturation region is used to configure a floating linear resistor. The DDCC and the MOS transistor voltage divider are used for canceling the nonlinear component term of MOS transistor in the non-saturation region to obtain a linear current/voltage relationship. The DDCC is employed to provide a simple summer of the circuit. This circuit offers an ease for realizing the voltage divider circuit and the temperature effect that includes in term of threshold voltage can be compensated. The proposed configuration employs only 16 MOS transistors. The performances of the proposed circuit are simulated with PSPICE to confirm the presented theory.

  14. Utility Test Results of a 2-Megawatt, 10-Second Reserve-Power System

    Energy Technology Data Exchange (ETDEWEB)

    BALL,GREG J.; NORRIS,BENJAMIN L.

    1999-10-01

    This report documents the 1996 evaluation by Pacific Gas and Electric Company of an advanced reserve-power system capable of supporting 2 MW of load for 10 seconds. The system, developed under a DOE Cooperative Agreement with AC Battery Corporation of East Troy, Wisconsin, contains battery storage that enables industrial facilities to ''ride through'' momentary outages. The evaluation consisted of tests of system performance using a wide variety of load types and operating conditions. The tests, which included simulated utility outages and voltage sags, demonstrated that the system could provide continuous power during utility outages and other disturbances and that it was compatible with a variety of load types found at industrial customer sites.

  15. High-voltage power supply unit

    CERN Document Server

    Garipov, G K; Silaev, A A; Shirokov, A V

    2002-01-01

    A unit comprising four high-voltage power sources (HPS) is designed for power supply of four independent photomultipliers. Each HPS comprises a pulse-width modulator, digital-to-analog converter, base voltage source and digital interface. HPS unit supplies up to 2000 V output voltage, up to 2.5 mA current and long-term stability equal to +- 0.03%

  16. Technical feasibility study of Voltage Optimization Unit

    DEFF Research Database (Denmark)

    Hu, Junjie; Marinelli, Mattia; Coppo, Massimiliano

    is performed using the soft-wares DigSilent PowerFactory and Matlab. In this simulation study, a real low voltage network from Dong Eldistribution is modeled in Powerfactory. The measured data of the real low voltage network is analyzed and the resulting loading profiles including active and reactive power...... are used as load basics for the analysis. In term of PV genera-tion profiles, a realistic PV output power is assumed. Four relevant indicies such as phase neutral voltage, netural potential voltage, unbalanced factor (VUF), and power losses are evaluated in the present study. The simulation tests include...

  17. Excitation of voltage oscillations in an induction voltage adder

    Directory of Open Access Journals (Sweden)

    Nichelle Bruner

    2009-07-01

    Full Text Available The induction voltage adder is an accelerator architecture used in recent designs of pulsed-power driven x-ray radiographic systems such as Sandia National Laboratories’ Radiographic Integrated Test Stand (RITS, the Atomic Weapons Establishment’s planned Hydrus Facility, and the Naval Research Laboratory’s Mercury. Each of these designs relies on magnetic insulation to prevent electron loss across the anode-cathode gap in the vicinity of the adder as well as in the coaxial transmission line. Particle-in-cell simulations of the RITS adder and transmission line show that, as magnetic insulation is being established during a pulse, some electron loss occurs across the gap. Sufficient delay in the cavity pulse timings provides an opportunity for high-momentum electrons to deeply penetrate the cavities of the adder cells where they can excite radio-frequency resonances. These oscillations may be amplified in subsequent gaps, resulting in oscillations in the output power. The specific modes supported by the RITS-6 accelerator and details of the mechanism by which they are excited are presented in this paper.

  18. Enhancement of AC high voltage measurements’ uncertainty using a high voltage divider calibration method

    Directory of Open Access Journals (Sweden)

    El-Rifaie Ali M.

    2015-01-01

    Full Text Available This paper discusses enhancing of the measurements’ uncertainty for AC high voltage up to 100 kV. This is achieved by using a high voltage divider calibration method. Voltage measurements have been carried out at the Egyptian national institute for standards (NIS, using a high voltage measuring system (Phenix-KVM100, that consists of a high voltage divider and a voltage display. The voltage divider and display have been calibrated in low and high voltage ranges. Reference standard digital voltmeter and a multifunction calibrator have been used to calibrate the KVM100 for achieving accurate and traceable results. All calibrations have been performed automatically using Laboratory Virtual Instrument Engineering Workbench (LabVIEW programs specially designed for this task. Uncertainty budget has been evaluated to get the measurements’ expanded uncertainties.

  19. Effects of Capcitor Bank on Fault Ride Through Capibility of Induction Generator Based Wind Turbines

    DEFF Research Database (Denmark)

    Hu, Y; Chen, Zhe

    2010-01-01

    power system stability and supply security. Some existing wind turbines are still based on fixed speed induction generators, the effects of capacitor bank on such generators are discussed in this paper. The simulation study shows the capacitor bank may costeffectively improve the dynamic performance......Wind turbine installation is increasing rapidly. In some networks, wind power penetration is significantly high and the performance of wind turbine plays an important role in power system operation and control. Especially, the behavior of wind turbines during a power system disturbance would affect...... of the induction generators....

  20. Aeroservoelastic analysis of storm-ride-through control strategies for wind turbines

    DEFF Research Database (Denmark)

    Tibaldi, Carlo; Hansen, Morten Hartvig

    2016-01-01

    An investigation of a control strategy to allow wind turbines to operate at high wind speeds by derating the rotor speed and generator torque set-points is presented. The investigation analyzes the wind turbine aeroservoelastic behavior in the above rated operational range by computing the aerody...

  1. Evaluation of the Voltage Support Strategies for the Low Voltage Grid Connected PV

    DEFF Research Database (Denmark)

    Demirok, Erhan; Sera, Dezso; Teodorescu, Remus

    2010-01-01

    Admissible range of grid voltage is one of the strictest constraints for the penetration of distributed photovoltaic (PV) generators especially connection to low voltage (LV) public networks. Voltage limits are usually fulfilled either by network reinforcements or limiting of power injections fro...

  2. Voltage-Sensitive Load Controllers for Voltage Regulation and Increased Load Factor in Distribution Systems

    DEFF Research Database (Denmark)

    Douglass, Philip James; Garcia-Valle, Rodrigo; Østergaard, Jacob

    2014-01-01

    This paper presents a novel controller design for controlling appliances based on local measurements of voltage. The controller finds the normalized voltage deviation accounting for the sensitivity of voltage measurements to appliance state. The controller produces a signal indicating desired pow...

  3. Voltage stability in low voltage microgrids in aspects of active and reactive power demand

    Directory of Open Access Journals (Sweden)

    Parol Mirosław

    2016-03-01

    Full Text Available Low voltage microgrids are autonomous subsystems, in which generation, storage and power and electrical energy consumption appear. In the paper the main attention has been paid to the voltage stability issue in low voltage microgrid for different variants of its operation. In the introduction a notion of microgrid has been presented, and also the issue of influence of active and reactive power balance on node voltage level has been described. Then description of voltage stability issue has been presented. The conditions of voltage stability and indicators used to determine voltage stability margin in the microgrid have been described. Description of the low voltage test microgrid, as well as research methodology along with definition of considered variants of its operation have been presented further. The results of exemplary calculations carried out for the daily changes in node load of the active and reactive power, i.e. the voltage and the voltage stability margin indexes in nodes have been presented. Furthermore, the changes of voltage stability margin indexes depending on the variant of the microgrid operation have been presented. Summary and formulation of conclusions related to the issue of voltage stability in microgrids have been included at the end of the paper.

  4. High-voltage engineering and testing

    CERN Document Server

    Ryan, Hugh M

    2013-01-01

    This 3rd edition of High Voltage Engineering Testing describes strategic developments in the field and reflects on how they can best be managed. All the key components of high voltage and distribution systems are covered including electric power networks, UHV and HV. Distribution systems including HVDC and power electronic systems are also considered.

  5. Reduced Voltage Scaling in Clock Distribution Networks

    Directory of Open Access Journals (Sweden)

    Khader Mohammad

    2009-01-01

    Full Text Available We propose a novel circuit technique to generate a reduced voltage swing (RVS signals for active power reduction on main buses and clocks. This is achieved without performance degradation, without extra power supply requirement, and with minimum area overhead. The technique stops the discharge path on the net that is swinging low at a certain voltage value. It reduces active power on the target net by as much as 33% compared to traditional full swing signaling. The logic 0 voltage value is programmable through control bits. If desired, the reduced-swing mode can also be disabled. The approach assumes that the logic 0 voltage value is always less than the threshold voltage of the nMOS receivers, which eliminate the need of the low to high voltage translation. The reduced noise margin and the increased leakage on the receiver transistors using this approach have been addressed through the selective usage of multithreshold voltage (MTV devices and the programmability of the low voltage value.

  6. Modeling and Simulation of Low Voltage Arcs

    NARCIS (Netherlands)

    Ghezzi, L.; Balestrero, A.

    2010-01-01

    Modeling and Simulation of Low Voltage Arcs is an attempt to improve the physical understanding, mathematical modeling and numerical simulation of the electric arcs that are found during current interruptions in low voltage circuit breakers. An empirical description is gained by refined electrical

  7. Low-Voltage Continuous Electrospinning Patterning.

    Science.gov (United States)

    Li, Xia; Li, Zhaoying; Wang, Liyun; Ma, Guokun; Meng, Fanlong; Pritchard, Robyn H; Gill, Elisabeth L; Liu, Ye; Huang, Yan Yan Shery

    2016-11-30

    Electrospinning is a versatile technique for the construction of microfibrous and nanofibrous structures with considerable potential in applications ranging from textile manufacturing to tissue engineering scaffolds. In the simplest form, electrospinning uses a high voltage of tens of thousands volts to draw out ultrafine polymer fibers over a large distance. However, the high voltage limits the flexible combination of material selection, deposition substrate, and control of patterns. Prior studies show that by performing electrospinning with a well-defined "near-field" condition, the operation voltage can be decreased to the kilovolt range, and further enable more precise patterning of fibril structures on a planar surface. In this work, by using solution dependent "initiators", we demonstrate a further lowering of voltage with an ultralow voltage continuous electrospinning patterning (LEP) technique, which reduces the applied voltage threshold to as low as 50 V, simultaneously permitting direct fiber patterning. The versatility of LEP is shown using a wide range of combination of polymer and solvent systems for thermoplastics and biopolymers. Novel functionalities are also incorporated when a low voltage mode is used in place of a high voltage mode, such as direct printing of living bacteria; the construction of suspended single fibers and membrane networks. The LEP technique reported here should open up new avenues in the patterning of bioelements and free-form nano- to microscale fibrous structures.

  8. Voltage-gated lipid ion channels

    DEFF Research Database (Denmark)

    Blicher, Andreas; Heimburg, Thomas Rainer

    2013-01-01

    probability as a function of voltage. The voltage-dependence of the lipid pores is found comparable to that of protein channels. Lifetime distributions of open and closed events indicate that the channel open distribution does not follow exponential statistics but rather power law behavior for long open times......Synthetic lipid membranes can display channel-like ion conduction events even in the absence of proteins. We show here that these events are voltage-gated with a quadratic voltage dependence as expected from electrostatic theory of capacitors. To this end, we recorded channel traces and current...... histograms in patch-experiments on lipid membranes. We derived a theoretical current-voltage relationship for pores in lipid membranes that describes the experimental data very well when assuming an asymmetric membrane. We determined the equilibrium constant between closed and open state and the open...

  9. Coordinated Voltage Control of Active Distribution Network

    Directory of Open Access Journals (Sweden)

    Xie Jiang

    2016-01-01

    Full Text Available This paper presents a centralized coordinated voltage control method for active distribution network to solve off-limit problem of voltage after incorporation of distributed generation (DG. The proposed method consists of two parts, it coordinated primal-dual interior point method-based voltage regulation schemes of DG reactive powers and capacitors with centralized on-load tap changer (OLTC controlling method which utilizes system’s maximum and minimum voltages, to improve the qualified rate of voltage and reduce the operation numbers of OLTC. The proposed coordination has considered the cost of capacitors. The method is tested using a radial edited IEEE-33 nodes distribution network which is modelled using MATLAB.

  10. Non-contact current and voltage sensor

    Science.gov (United States)

    Carpenter, Gary D; El-Essawy, Wael; Ferreira, Alexandre Peixoto; Keller, Thomas Walter; Rubio, Juan C; Schappert, Michael A

    2014-03-25

    A detachable current and voltage sensor provides an isolated and convenient device to measure current passing through a conductor such as an AC branch circuit wire, as well as providing an indication of an electrostatic potential on the wire, which can be used to indicate the phase of the voltage on the wire, and optionally a magnitude of the voltage. The device includes a housing that contains the current and voltage sensors, which may be a ferrite cylinder with a hall effect sensor disposed in a gap along the circumference to measure current, or alternative a winding provided through the cylinder along its axis and a capacitive plate or wire disposed adjacent to, or within, the ferrite cylinder to provide the indication of the voltage.

  11. Practical considerations in voltage stability assessment

    Energy Technology Data Exchange (ETDEWEB)

    Kundur, P.; Gao, B. [Powertech Labs. Inc., Surrey, BC (Canada)

    1994-12-31

    This paper deals with some of the most important practical issues related to voltage stability assessment of large practical systems. A brief discussion of the practical aspects of voltage stability problem and prevention of voltage instability is given first, followed by descriptions of different analytical techniques and tools for voltage stability analysis. Presentations of analytical tools is focused on the VSTAB program which incorporates the modal analysis, continuation power flow, and shortest distance to instability techniques, Finally, an example case study of a practical large system is presented. The case study illustrates how modal analysis is used to determine the most effective load shedding scheme for preventing voltage instability. (author) 15 refs., 2 figs., 2 tabs.

  12. Los huevos falsos (SAGs facilitan el comportamiento social de emergencia en las crías de la tortuga laúd Dermochelys coriacea (Testudines: Dermochelyidae

    Directory of Open Access Journals (Sweden)

    Juan Patiño-Martinez

    2010-09-01

    Full Text Available La emergencia de las crías de tortuga laúd eclosionadas en los nidos profundos desde la arena hasta la superficie de la playa ocurre sin ayuda parental y es el primer gran desafío de supervivencia en su ciclo de vida. Este estudio, desarrollado en la costa Caribe colombiana, describe el comportamiento social de emergencia de neonatos y evalúa el efecto de la traslocación de los nidos en los patrones temporales de emergencia. Se propone por primera vez que el espacio liberado por la deshidratación de falsos huevos (SAGs en la nidada, representa una ventaja reproductiva al facilitar el agrupamiento de los neonatos en un espacio muy limitado y favorecer la sincronía de la emergencia. El tiempo medio registrado para la emergencia en grupo fue de 3.3 días, variando entre uno y seis días. La traslocación de los nidos no afectó el patrón temporal de emergencia que fue predominantemente nocturno (77.77% en nidos naturales y 81.65% en trasladados. Los picos máximos de emergencias a la superficie coincidieron con los periodos de menor temperatura ambiental exterior (22:00h-06:00h. La ventaja selectiva de este patrón temporal y de la emergencia sincrónica está probablemente relacionada con las mayores tasas de depredación y mortalidad por hipertermia observadas durante el día.False eggs (SAGs facilitate social post-hatching emergence behaviour in Leatherback turtles Dermochelys coriacea (Testudines: Dermochelyidae nests. Hatchling emergence to the beach surface from deep sand nests occurs without parental care. Social behaviour among siblings is crucial to overcome this first challenge in sea turtles life. This study, carried out at the Caribbean coast of Colombia, describes the emergence social behaviour of hatchlings from eight nests, and assess the nests translocation effects on temporal patterns of emergence. For the first time, we propose that space released by dehydration of shelled albumen globes (SAGs at the top of the clutch

  13. Mécano-Stimulation™ of the skin improves sagging score and induces beneficial functional modification of the fibroblasts: clinical, biological, and histological evaluations

    Directory of Open Access Journals (Sweden)

    Humbert P

    2015-02-01

    Full Text Available Philippe Humbert,1,2 Ferial Fanian,1,2 Thomas Lihoreau,1,2 Adeline Jeudy,1,2 Ahmed Elkhyat,1,2 Sophie Robin,3 Carol Courderot-Masuyer,3 Hélène Tauzin,3 Christine Lafforgue,1,2,4 Marek Haftek5 1Research and Studies Center on the Integument (CERT, Department of Dermatology, Clinical Investigation Center (CIC 1431, Besançon University Hospital; 2INSERM UMR1098, FED4234 IBCT, University of Franche-Comté, Besançon, France; 3SARL BIOEXIGENCE, Besançon, France; 4Dermopharmacology and Cosmetology Unit, University of Paris Sud, France; 5University of Lyon 1, EA4169, Experimental, clinical and therapeutic aspects of the skin barrier function, INSERM US7 – CNRS UMS3453, Lyon, France Background: Loss of mechanical tension appears to be the major factor underlying decreased collagen synthesis in aged skin. Numerous in vitro studies have shown the impact of mechanical forces on fibroblasts through mechanotransduction, which consists of the conversion of mechanical signals to biochemical responses. Such responses are characterized by the modulation of gene expression coding not only for extracellular matrix components (collagens, elastin, etc. but also for degradation enzymes (matrix metalloproteinases [MMPs] and their inhibitors (tissue inhibitors of metalloproteinases [TIMPs]. A new device providing a mechanical stimulation of the cutaneous and subcutaneous tissue has been used in a simple, blinded, controlled, and randomized study. Materials and methods: Thirty subjects (aged between 35 years and 50 years, with clinical signs of skin sagging, were randomly assigned to have a treatment on hemiface. After a total of 24 sessions with Mécano-Stimulation™, biopsies were performed on the treated side and control area for in vitro analysis (dosage of hyaluronic acid, elastin, type I collagen, MMP9; equivalent dermis retraction; GlaSbox®; n=10 and electron microscopy (n=10. Furthermore, before and after the treatment, clinical evaluations and self

  14. Hysteresis in voltage-gated channels.

    Science.gov (United States)

    Villalba-Galea, Carlos A

    2017-03-04

    Ion channels constitute a superfamily of membrane proteins found in all living creatures. Their activity allows fast translocation of ions across the plasma membrane down the ion's transmembrane electrochemical gradient, resulting in a difference in electrical potential across the plasma membrane, known as the membrane potential. A group within this superfamily, namely voltage-gated channels, displays activity that is sensitive to the membrane potential. The activity of voltage-gated channels is controlled by the membrane potential, while the membrane potential is changed by these channels' activity. This interplay produces variations in the membrane potential that have evolved into electrical signals in many organisms. These signals are essential for numerous biological processes, including neuronal activity, insulin release, muscle contraction, fertilization and many others. In recent years, the activity of the voltage-gated channels has been observed not to follow a simple relationship with the membrane potential. Instead, it has been shown that the activity of voltage-gated channel displays hysteresis. In fact, a growing number of evidence have demonstrated that the voltage dependence of channel activity is dynamically modulated by activity itself. In spite of the great impact that this property can have on electrical signaling, hysteresis in voltage-gated channels is often overlooked. Addressing this issue, this review provides examples of voltage-gated ion channels displaying hysteretic behavior. Further, this review will discuss how Dynamic Voltage Dependence in voltage-gated channels can have a physiological role in electrical signaling. Furthermore, this review will elaborate on the current thoughts on the mechanism underlying hysteresis in voltage-gated channels.

  15. Voltage Management in Unbalanced Low Voltage Networks Using a Decoupled Phase-Tap-Changer Transformer

    DEFF Research Database (Denmark)

    Coppo, Massimiliano; Turri, Roberto; Marinelli, Mattia

    2014-01-01

    The paper studies a medium voltage-low voltage transformer with a decoupled on load tap changer capability on each phase. The overall objective is the evaluation of the potential benefits on a low voltage network of such possibility. A realistic Danish low voltage network is used for the analysis....... The load profiles are characterized by using single phase measurement data on voltages, currents and active powers with a 10 minutes resolution. Different scenarios are considered: no tap action, three-phase coordinated tap action, single phase discrete step and single phase continuous tap action...

  16. Fuel Cell/Electrochemical Cell Voltage Monitor

    Science.gov (United States)

    Vasquez, Arturo

    2012-01-01

    A concept has been developed for a new fuel cell individual-cell-voltage monitor that can be directly connected to a multi-cell fuel cell stack for direct substack power provisioning. It can also provide voltage isolation for applications in high-voltage fuel cell stacks. The technology consists of basic modules, each with an 8- to 16-cell input electrical measurement connection port. For each basic module, a power input connection would be provided for direct connection to a sub-stack of fuel cells in series within the larger stack. This power connection would allow for module power to be available in the range of 9-15 volts DC. The relatively low voltage differences that the module would encounter from the input electrical measurement connection port, coupled with the fact that the module's operating power is supplied by the same substack voltage input (and so will be at similar voltage), provides for elimination of high-commonmode voltage issues within each module. Within each module, there would be options for analog-to-digital conversion and data transfer schemes. Each module would also include a data-output/communication port. Each of these ports would be required to be either non-electrical (e.g., optically isolated) or electrically isolated. This is necessary to account for the fact that the plurality of modules attached to the stack will normally be at a range of voltages approaching the full range of the fuel cell stack operating voltages. A communications/ data bus could interface with the several basic modules. Options have been identified for command inputs from the spacecraft vehicle controller, and for output-status/data feeds to the vehicle.

  17. High voltage electricity installations a planning perspective

    CERN Document Server

    Jay, Stephen Andrew

    2006-01-01

    The presence of high voltage power lines has provoked widespread concern for many years. High Voltage Electricity Installations presents an in-depth study of policy surrounding the planning of high voltage installations, discussing the manner in which they are percieved by the public, and the associated environmental issues. An analysis of these concerns, along with the geographical, environmental and political influences that shape their expression, is presented. Investigates local planning policy in an area of the energy sector that is of highly topical environmental and public concern Cover

  18. Dolomitization of felsic volcaniclastic rocks in continental strata: A study from the Lower Cretaceous of the A'nan Sag in Er'lian Basin, China

    Science.gov (United States)

    Zhu, Shifa; Yue, Hui; Zhu, Xiaomin; Sun, Shuyang; Wei, Wei; Liu, Xin; Jia, Ye

    2017-05-01

    Dolomitization of fine-grained volcaniclastic rocks is common in the Lower Cretaceous of the A'nan Sag in the Er'lian Basin of China. Analysis of core samples shows that the organic-rich volcaniclastic rocks are mainly composed of reworked felsic volcanic materials and terrigenous clay minerals. The fine-grained volcaniclastic rocks can be divided into four types: volcaniclastic rocks without carbonatization, volcaniclastic rocks with ferroan dolomites, dolomitized and calcified volcaniclastic rocks, and calcified volcaniclastic rocks. The parent rocks of the volcaniclastic rocks have high silicon and potassium contents and low iron and magnesium contents, and are probably felsic magma of the calc-alkaline series. The average values of δ13CPDB of the carbonate minerals are about 3.13‰; the average values of δ18OPDB are about - 16.74‰. The compositions of C and O isotopes are probably influenced by bacterial methanogenesis. Iron, magnesium, and calcium are probably derived from illitization of terrigenous smectite. A model for dolomitization of felsic volcaniclastic rock is proposed, including three stages: 1) mixed sedimentation and bacterial methanogenesis ( 70 °C) and dolomitization (75 to 97 °C); and 3) dissolution. Late dissolution of authigenic carbonate minerals, creating abundant secondary pores, is significant for hydrocarbon accumulation.

  19. Direct observation of voltage barriers in ZnO varistors

    Science.gov (United States)

    Krivanek, O. L.; Williams, P.; Lin, Y.-C.

    1979-01-01

    Voltage barriers in a ZnO varistor have been imaged by voltage-contrast scanning electron microscopy. They are due to grain boundaries and are capable of supporting voltage differences of up to about 4 V.

  20. High voltage and electrical insulation engineering

    CERN Document Server

    Arora, Ravindra

    2011-01-01

    "The book is written for students as well as for teachers and researchers in the field of High Voltage and Insulation Engineering. It is based on the advance level courses conducted at TU Dresden, Germany and Indian Institute of Technology Kanpur, India. The book has a novel approach describing the fundamental concept of field dependent behavior of dielectrics subjected to high voltage. There is no other book in the field of high voltage engineering following this new approach in describing the behavior of dielectrics. The contents begin with the description of fundamental terminology in the subject of high voltage engineering. It is followed by the classification of electric fields and the techniques of field estimation. Performance of gaseous, liquid and solid dielectrics under different field conditions is described in the subsequent chapters. Separate chapters on vacuum as insulation and the lightning phenomenon are included"--

  1. Pyrotechnic Simulator/Stray-Voltage Detector

    Science.gov (United States)

    Greenfield, Terry

    2009-01-01

    The concept for a dual test item has been developed for use in simulating live initiators/detonators during ground testing to verify the proper operation of the safing and firing circuitry for ground and flight systems ordnance as well as continuous monitoring for any stray voltages. Previous ordnance simulators have consisted of fuses, flash bulbs, inert devices with bridge wires, and actual live ordnance items mounted in test chambers. Stray voltage detectors have included devices connected to the firing circuits for continuous monitoring and a final no-voltage test just prior to ordnance connection. The purpose of this combined ordnance simulation and stray-voltage detection is to provide an improved and comprehensive method to ensure the ordnance circuitry is verified safe and operational.

  2. Compact, Lightweight, High Voltage Propellant Isolators Project

    Data.gov (United States)

    National Aeronautics and Space Administration — TA&T, Inc. proposes an enabling fabrication process for high voltage isolators required in high power solar electric and nuclear electric propulsion (SEP and...

  3. Cascode-based voltage-amplifier stage

    Directory of Open Access Journals (Sweden)

    Pospisilik Martin

    2017-01-01

    Full Text Available Voltage-amplifier stages are the basic components of commonly used high gain amplifiers the bias and other parameters of whose are set by the external negative feedback. The typical device that uses the voltage-amplifier stage is the operational amplifier. Similar constructions can also be created on the basis of discrete transistors. From the circuit designer’s point of view, the voltage-amplifier stage defines the crucial parameters of the whole unit - the amplification factor, dominant pole of its transfer function and the slew rate. In this paper the proposal on construction of the voltage-amplifier stage based on discrete transistors is described. When connected between the input differential amplifier and the output stage, it allows creating of cheap amplifier for HiFi applications with considerable performance.

  4. Modular high voltage power supply for chemical analysis

    Science.gov (United States)

    Stamps, James F [Livermore, CA; Yee, Daniel D [Dublin, CA

    2008-07-15

    A high voltage power supply for use in a system such as a microfluidics system, uses a DC-DC converter in parallel with a voltage-controlled resistor. A feedback circuit provides a control signal for the DC-DC converter and voltage-controlled resistor so as to regulate the output voltage of the high voltage power supply, as well as, to sink or source current from the high voltage supply.

  5. Ultra-low Voltage CMOS Cascode Amplifier

    DEFF Research Database (Denmark)

    Lehmann, Torsten; Cassia, Marco

    2000-01-01

    In this paper, we design a folded cascode operational transconductance amplifier in a standard CMOS process, which has a measured 69 dB DC gain, a 2 MHz bandwidth and compatible input- and output voltage levels at a 1 V power supply. This is done by a novel Current Driven Bulk (CDB) technique......, which reduces the MOST threshold voltage by forcing a constant current though the transistor bulk terminal. We also look at limitations and improvements of this CDB technique....

  6. Voltage, Temperature, Frequency Margin Test Report

    DEFF Research Database (Denmark)

    Denver, Troelz

    1999-01-01

    The purpose of the tests is to establish the camera functionality when it is exposed to an extreme environment for prolonged periods, thus simulating the end of life performance. This environment covers temperature, input clock frequency and supply voltage variation......The purpose of the tests is to establish the camera functionality when it is exposed to an extreme environment for prolonged periods, thus simulating the end of life performance. This environment covers temperature, input clock frequency and supply voltage variation...

  7. RF Voltage Measurements on ICRF Antennas

    Science.gov (United States)

    Bell, G. L.; Goulding, R. H.; Hoffman, D. J.; Wilgen, J. B.; Zhang, H. M.; Ryan, P. M.; Syed, G. M. S.; Kaye, A. S.

    1996-11-01

    Particle and heat flux on the plasma facing surfaces of high-power RF antennas used in fusion devices can result in damage to the antenna structures. High impedance capacitive probe measurements of the RF voltages on Faraday shields of several loop antennas indicate that voltages as high as 30% of the drive voltage can exist for 0/0 phasing (D.J. Hoffman, et al., AIP Conf. Proc. 355), 368 (Palm Spgs., CA, 1995).. These voltages can contribute to increased energy deposition on the antenna owing to increased RF sheath voltages. We report on continued efforts to understand the source and to control these RF voltages. E and B field distributions have been measured on the mock-up of the JET A2 antenna using standard B-dot probes and novel E-field probes positioned with a new automated scanning system. These data are compared with calculated fields from 3-D antenna models. The measurements demonstrate the dependency of the surface E-fields on the phasing of the strap currents and show the charge accumulation at the antenna top and bottom predicted by the models.

  8. VKCDB: Voltage-gated potassium channel database

    Directory of Open Access Journals (Sweden)

    Gallin Warren J

    2004-01-01

    Full Text Available Abstract Background The family of voltage-gated potassium channels comprises a functionally diverse group of membrane proteins. They help maintain and regulate the potassium ion-based component of the membrane potential and are thus central to many critical physiological processes. VKCDB (Voltage-gated potassium [K] Channel DataBase is a database of structural and functional data on these channels. It is designed as a resource for research on the molecular basis of voltage-gated potassium channel function. Description Voltage-gated potassium channel sequences were identified by using BLASTP to search GENBANK and SWISSPROT. Annotations for all voltage-gated potassium channels were selectively parsed and integrated into VKCDB. Electrophysiological and pharmacological data for the channels were collected from published journal articles. Transmembrane domain predictions by TMHMM and PHD are included for each VKCDB entry. Multiple sequence alignments of conserved domains of channels of the four Kv families and the KCNQ family are also included. Currently VKCDB contains 346 channel entries. It can be browsed and searched using a set of functionally relevant categories. Protein sequences can also be searched using a local BLAST engine. Conclusions VKCDB is a resource for comparative studies of voltage-gated potassium channels. The methods used to construct VKCDB are general; they can be used to create specialized databases for other protein families. VKCDB is accessible at http://vkcdb.biology.ualberta.ca.

  9. Prediction of breakdown voltages in novel gases for high voltage insulation

    Energy Technology Data Exchange (ETDEWEB)

    Koch, M.

    2015-07-01

    This thesis submitted to the Swiss Federal Institute of Technology ETH in Zurich examines the use of sulphur hexafluoride (SF{sub 6}) and similar gases as important insulation media for high voltage equipment. Due to its superior insulation properties, SF{sub 6} is widely used in gas-insulated switchgear. However, the gas also has a very high global warming potential and the content of SF{sub 6} in the atmosphere is constantly increasing. The search for new insulation gases using classical breakdown experiments is discussed. A model for SF{sub 6} based on the stepped leader model is described. This calculates the breakdown voltages in arbitrary electrode configurations and under standard voltage waveforms. Thus, the thesis provides a method for the prediction of breakdown voltages of arbitrary field configurations under standard voltage waveforms for gases with electron-attaching properties. With this, further gases can be characterized for usage as high voltage insulation media.

  10. Voltage Unbalance Compensation with Smart Three-phase Loads

    DEFF Research Database (Denmark)

    Douglass, Philip; Trintis, Ionut; Munk-Nielsen, Stig

    2016-01-01

    This paper describes the design, proof-of-concept simulations and laboratory test of an algorithm for controlling active front-end rectifiers to reduce voltage unbalance. Using inputs of RMS voltage, the rectifier controller allocates load unevenly on its 3 phases to compensate for voltage...... unbalance originating in the power supply network. Two variants of the algorithm are tested: first, using phase-neutral voltage as input, second, using phase-phase voltage. The control algorithm is described, and evaluated in simulations and laboratory tests. Two metrics for quantifying voltage unbalance...... are evaluated: one metric based on the maximum deviation of RMS phaseneutral voltage from the average voltage and one metric based on negative sequence voltage. The tests show that controller that uses phase-neutral voltage as input can in most cases eliminate the deviations of phase voltage from the average...

  11. Overview of HVRT technical measures for DFIG

    Science.gov (United States)

    Yu, Haiyang

    2017-05-01

    A With the rapid increase of the proportion of double-fed induction wind turbines generator (DFIG), higher requirements are proposed for the continuous operation ability under external power grid failure. The paper first analysed the transient process of DFIG in cases of power grid voltage surge, proposed the related standard requirements for high voltage ride-through ability of several countries, including China, and then summarized and evaluated the various high voltage ride-through technical measures suitable for DFIG, and finally forecasted the high voltage ride-through technology development trend.

  12. Los huevos falsos (SAGs facilitan el comportamiento social de emergencia en las crías de la tortuga laúd Dermochelys coriacea (Testudines: Dermochelyidae

    Directory of Open Access Journals (Sweden)

    Juan Patiño-Martinez

    2010-09-01

    Full Text Available La emergencia de las crías de tortuga laúd eclosionadas en los nidos profundos desde la arena hasta la superficie de la playa ocurre sin ayuda parental y es el primer gran desafío de supervivencia en su ciclo de vida. Este estudio, desarrollado en la costa Caribe colombiana, describe el comportamiento social de emergencia de neonatos y evalúa el efecto de la traslocación de los nidos en los patrones temporales de emergencia. Se propone por primera vez que el espacio liberado por la deshidratación de falsos huevos (SAGs en la nidada, representa una ventaja reproductiva al facilitar el agrupamiento de los neonatos en un espacio muy limitado y favorecer la sincronía de la emergencia. El tiempo medio registrado para la emergencia en grupo fue de 3.3 días, variando entre uno y seis días. La traslocación de los nidos no afectó el patrón temporal de emergencia que fue predominantemente nocturno (77.77% en nidos naturales y 81.65% en trasladados. Los picos máximos de emergencias a la superficie coincidieron con los periodos de menor temperatura ambiental exterior (22:00h-06:00h. La ventaja selectiva de este patrón temporal y de la emergencia sincrónica está probablemente relacionada con las mayores tasas de depredación y mortalidad por hipertermia observadas durante el día.

  13. Production of refolded Toxoplasma gondii recombinant SAG1-related sequence 3 (SRS3) and its use for serodiagnosis of human toxoplasmosis.

    Science.gov (United States)

    Mirzadeh, Abolfazl; Saadatnia, Geita; Golkar, Majid; Babaie, Jalal; Noordin, Rahmah

    2017-05-01

    SAG1-related sequence 3 (SRS3) is one of the major Toxoplasma gondii tachyzoite surface antigens and has been shown to be potentially useful for the detection of toxoplasmosis. This protein is highly conformational due to the presence of six disulfide bonds. To achieve solubility and antigenicity, SRS3 depends on proper disulfide bond formation. The aim of this study was to over-express the SRS3 protein with correct folding for use in serodiagnosis of the disease. To achieve this, a truncated SRS3 fusion protein (rtSRS3) was produced, containing six histidyl residues at both terminals and purified by immobilized metal affinity chromatography. The refolding process was performed through three methods, namely dialysis in the presence of chemical additives along with reduced/oxidized glutathione and drop-wise dilution methods with reduced/oxidized glutathione or reduced DTT/oxidized glutathione. Ellman's assay and ELISA showed that the protein folding obtained by the dialysis method was the most favorable, probably due to the correct folding. Subsequently, serum samples from individuals with chronic infection (n = 76), probable acute infection (n = 14), and healthy controls (n = 81) were used to determine the usefulness of the refolded rtSRS3 for Toxoplasma serodiagnosis. The results of the developed IgG-ELISA showed a diagnostic specificity of 91% and a sensitivity of 82.89% and 100% for chronic and acute serum samples, respectively. In conclusion, correctly folded rtSRS3 has the potential to be used as a soluble antigen for the detection of human toxoplasmosis. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. Ensaio terapêutico com glucantime em sagüis (Callithrix jacchus infectados com uma cepa de Leishmania donovani aparentemente resistente ao tratamento

    Directory of Open Access Journals (Sweden)

    R. Dietze

    1985-03-01

    Full Text Available Os autores relatam o resultado de um ensaio terapêutico em sagüis com uma cepa de Leishmania donovani isolada de um caso humano fatal de calazar, clinicamente resistente aos antimoniais (Glucantime e Pentostam, Anfotericina B ePentamidina. Os testes cutâneos realizados no paciente para avaliação da imunidade celular foram negativos à exceção do DNCB a 2%. Quatro sangüis adultos (Callithrix jacchus foram inoculados por via intraperitoneal com uma suspensão deformas amastigotas de L. donovani. Duzentos e dez dias após, todos os animais mostravam formas amastigotas do protozoário, evidenciadas através de punção hepática por aspiração. Iniciou-se então um esquema terapêutico com glucantime (28 mgSb v/kg/dia em três séries de 10 dias com cinco dias de intervalo entre elas em três dosprimatas,ficando o quarto animal como controle. Nos três animais tratados houve curaparasitológica da doença, o mesmo não ocorrehdo com o controle. O fato de a amostra de L. donovani ter sido, no paciente, resistente aos vários tratamentos e ter sido sensível em modelo experimental à terapêutica com glucantime, sugere a possibilidade de que fatores imunológicos do paciente possam ter contribuído para a evolução fatal da doença.

  15. Investigation of phase-wise voltage regulator control logics for compensating voltage deviations in an experimental low voltage network

    DEFF Research Database (Denmark)

    Hu, Junjie; Zecchino, Antonio; Marinelli, Mattia

    2016-01-01

    This paper investigates the control logics of an on-load tap-changer (OLTC) transformer by means of an experimental system validation. The experimental low-voltage unbalanced system consists of a decoupled single-phase OLTC transformer, a 75-metre 16 mm2 cable, a controllable single-phase resistive...... load and an electric vehicle, which has the vehicle-to-grid function. Three control logics of the OLTC transformer are described in the study. The three control logics are classified based on their control objectives and control inputs, which include network currents and voltages, and can be measured...... either locally or remotely. To evaluate and compare the control performances of the three control logics, all the tests use the same loading profiles. The experimental results indicate that the modified line compensation control can regulate voltage in a safe band in the case of various load...

  16. High voltage testing for the Majorana Demonstrator

    Energy Technology Data Exchange (ETDEWEB)

    Abgrall, N.; Arnquist, Isaac J.; Avignone, F. T.; Barabash, A.; Bertrand, F.; Bradley, A. W.; Brudanin, V.; Busch, Matthew; Buuck, M.; Byram, D.; Caldwell, A. S.; Chan, Yuen-Dat; Christofferson, C. D.; Chu, Pamela M.; Cuesta, C.; Detwiler, Jason A.; Doe, P. J.; Dunagan, C.; Efremenko, Yuri; Ejiri, H.; Elliott, S. R.; Fu, Z.; Galindo-Uribarri, A.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guinn, I.; Guiseppe, V. E.; Henning, R.; Hoppe, Eric W.; Howard, S.; Howe, M. A.; Jasinski, B. R.; Keeter, K.; Kidd, M. F.; Konovalov, S.; Kouzes, Richard T.; Laferriere, Brian D.; Leon, Jonathan D.; Li, Alexander D.; MacMullin, J.; Martin, R. D.; Massarcyk, R.; Meijer, S. J.; Mertens, S.; Orrell, John L.; O' Shaughnessy, C.; Poon, Alan W.; Radford, D. C.; Rager, J.; Rielage, Keith; Robertson, R. G. H.; Romero Romo, M.; Shanks, B.; Shirchenko, M.; Snyder, N.; Suriano, Anne-Marie E.; Tedeschi, D.; Thompson, Andrew; Ton, K. T.; Trimble, J. E.; Varner, R. L.; Vasilyev, Sergey; Vetter, Kai; Vorren, Kris R.; White, Brandon R.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yakushev, E.; Yu, Chang-Hong; Yumatov, V.

    2016-07-01

    The Majorana Collaboration is constructing theMajorana Demonstrator, an ultra-low background, 44-kg modular high-purity Ge (HPGe) detector array to search for neutrinoless double-beta decay in 76Ge. The phenomenon of surface micro-discharge induced by high-voltage has been studied in the context of theMajorana Demonstrator. This effect can damage the front-end electronics or mimic detector signals. To ensure the correct performance, every high-voltage cable and feedthrough must be capable of supplying HPGe detector operating voltages as high as 5 kV without exhibiting discharge. R&D measurements were carried out to understand the testing system and determine the optimum design configuration of the high-voltage path, including different improvements of the cable layout and feedthrough flange model selection. Every cable and feedthrough to be used at the Majorana Demonstrator was characterized and the micro-discharge effects during theMajorana Demonstrator commissioning phase were studied. A stable configuration has been achieved, and the cables and connectors can supply HPGe detector operating voltages without exhibiting discharge.

  17. Induced Voltage in an Open Wire

    Science.gov (United States)

    Morawetz, K.; Gilbert, M.; Trupp, A.

    2017-07-01

    A puzzle arising from Faraday's law has been considered and solved concerning the question which voltage will be induced in an open wire with a time-varying homogeneous magnetic field. In contrast to closed wires where the voltage is determined by the time variance of the magnetic field and the enclosed area, in an open wire we have to integrate the electric field along the wire. It is found that the longitudinal electric field with respect to the wave vector contributes with 1/3 and the transverse field with 2/3 to the induced voltage. In order to find the electric fields the sources of the magnetic fields are necessary to know. The representation of a spatially homogeneous and time-varying magnetic field implies unavoidably a certain symmetry point or symmetry line which depend on the geometry of the source. As a consequence the induced voltage of an open wire is found to be the area covered with respect to this symmetry line or point perpendicular to the magnetic field. This in turn allows to find the symmetry points of a magnetic field source by measuring the voltage of an open wire placed with different angles in the magnetic field. We present exactly solvable models of the Maxwell equations for a symmetry point and for a symmetry line, respectively. The results are applicable to open circuit problems like corrosion and for astrophysical applications.

  18. Low-Voltage Consumption Coordination for Loss Minimization and Voltage Control

    DEFF Research Database (Denmark)

    Juelsgaard, Morten; Sloth, Christoffer; Wisniewski, Rafal

    2014-01-01

    This work presents a strategy for minimizing active power losses in low-voltage grids, by coordinating the consumption of electric vehicles and power generation from solar panels. We show that minimizing losses, also reduces voltage variations, and illustrate how this may be employed for increasing...

  19. Synchronised Voltage Space Vector Modulation for Three-level Inverters with Common-mode Voltage Elimination

    DEFF Research Database (Denmark)

    Oleschuk, Valentin; Blaabjerg, Frede

    2002-01-01

    A novel method of direct synchronous pulse-width modulation (PWM) is disseminated to three-level voltage source inverters with control algorithms with elimination of the common-mode voltages in three-phase drive systems with PWM. It provides smooth pulses-ratio changing and a quarter-wave symmetry...

  20. Voltage-gated proton (H(v)1) channels, a singular voltage sensing domain.

    Science.gov (United States)

    Castillo, Karen; Pupo, Amaury; Baez-Nieto, David; Contreras, Gustavo F; Morera, Francisco J; Neely, Alan; Latorre, Ramon; Gonzalez, Carlos

    2015-11-14

    The main role of voltage-gated proton channels (Hv1) is to extrude protons from the intracellular milieu when, mediated by different cellular processes, the H(+) concentration increases. Hv1 are exquisitely selective for protons and their structure is homologous to the voltage sensing domain (VSD) of other voltage-gated ion channels like sodium, potassium, and calcium channels. In clear contrast to the classical voltage-dependent channels, Hv1 lacks a pore domain and thus permeation necessarily occurs through the voltage sensing domain. Hv1 channels are activated by depolarizing voltages, and increases in internal proton concentration. It has been proposed that local conformational changes of the transmembrane segment S4, driven by depolarization, trigger the molecular rearrangements that open Hv1. However, it is still unclear how the electromechanical coupling is achieved between the VSD and the potential pore, allowing the proton flux from the intracellular to the extracellular side. Here we provide a revised view of voltage activation in Hv1 channels, offering a comparative scenario with other voltage sensing channels domains. Copyright © 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

  1. On Secondary Control Approaches for Voltage Regulation in DC Microgrids

    DEFF Research Database (Denmark)

    Peyghami Akhuleh, Saeed; Mokhtari, Hossein; Davari, Pooya

    2017-01-01

    regulation on the load busses within a suitable range. Therefore, in addition to compensate the voltage drop of the primary controller, it is necessary to regulate the voltage of critical loads. In this paper, a new voltage regulation strategy is proposed to regulate the voltage of Micro-Grid (MG...

  2. 30 CFR 75.804 - Underground high-voltage cables.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Underground high-voltage cables. 75.804 Section... AND HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Underground High-Voltage Distribution § 75.804 Underground high-voltage cables. (a) Underground high-voltage cables used in resistance...

  3. 46 CFR 120.324 - Dual voltage generators.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Dual voltage generators. 120.324 Section 120.324... INSTALLATION Power Sources and Distribution Systems § 120.324 Dual voltage generators. (a) A dual voltage generator installed on a vessel shall be of the grounded type, where: (1) The neutral of a dual voltage...

  4. 30 CFR 77.810 - High-voltage equipment; grounding.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false High-voltage equipment; grounding. 77.810... COAL MINES Surface High-Voltage Distribution § 77.810 High-voltage equipment; grounding. Frames, supporting structures, and enclosures of stationary, portable, or mobile high-voltage equipment shall be...

  5. 47 CFR 17.54 - Rated lamp voltage.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Rated lamp voltage. 17.54 Section 17.54... voltage. To insure the necessary lumen output by obstruction lights, the rated voltage of incandescent lamps used shall correspond to be within 3 percent higher than the voltage across the lamp socket during...

  6. 46 CFR 129.326 - Dual-voltage generators.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Dual-voltage generators. 129.326 Section 129.326... INSTALLATIONS Power Sources and Distribution Systems § 129.326 Dual-voltage generators. If a dual-voltage generator is installed on an OSV— (a) The neutral of the dual-voltage system must be solidly grounded at the...

  7. Voltage control in active, intelligent low-voltage distribution networks; Spannungshaltung in aktiven, intelligenten Niederspannungsnetzen

    Energy Technology Data Exchange (ETDEWEB)

    Buelo, Thorsten; Mende, Denis [SMA Solar Technology AG, Niestetal (Germany); Geibel, Dominik [Fraunhofer Institut fuer Windenergie und Energiesystemtechnik (IWES), Kassel (Germany)] [and others

    2012-07-01

    This paper describes approaches for the voltage control in low-voltage distribution networks with a high share of distributed energy resources (DER). Taken into account are devices such as distribution transformers with on-load tap changer (OLTC), photovoltaic-inverters with reactive power capability and electronic voltage controllers (EVC). After a short description regarding voltage control, the devices and selected system concepts as well as the advantages and disadvantages of the different devices are described. Finally, the system-concepts are compared using the example of a real low voltage network, taking into account the possible increase of hosting capacity of the network, curtailing losses and the amount of reactive energy to be provided. (orig.)

  8. Energy Storage Options for Voltage Support in Low-Voltage Grids with High Penetration of Photovoltaic

    DEFF Research Database (Denmark)

    Marra, Francesco; Tarek Fawzy, Y.; Bülo, Thorsten

    2012-01-01

    The generation of power by photovoltaic (PV) systems is constantly increasing in low-voltage (LV) distribution grids, in line with the European environmental targets. To cope with the effects on grid voltage profiles during high generation and low demand periods, new solutions need to be establis......The generation of power by photovoltaic (PV) systems is constantly increasing in low-voltage (LV) distribution grids, in line with the European environmental targets. To cope with the effects on grid voltage profiles during high generation and low demand periods, new solutions need...... to be established. In the long term, these solutions should also aim to allow further more PV installed capacity, while meeting the power quality requirements. In this paper, different concepts of energy storage are proposed to ensure the voltage quality requirements in a LV grid with high PV penetration...

  9. Determination of the cathode fall voltage in fluorescent lamps by measurement of the operating voltage

    Energy Technology Data Exchange (ETDEWEB)

    Hilscher, A. [OSRAM GmbH, Augsburg (Germany)

    2002-07-21

    A new method for the determination of the cathode fall voltage of fluorescent lamps is shown. The cathode fall voltage can be determined by measurement of the lamp operating voltage at constant lamp wall temperature, constant discharge current and variation of the electrode heating current. Commercial lamps, which do not need to be specially prepared, can be used for the measurement. The results show good correlation to other measurements of the cathode fall voltage at various discharge currents by means of capacitive coupling. The measured values of the cathode fall voltage are used for determining the minimum, target and maximum setting of the sum of the squares of the pin currents of one electrode (the so-called SOS value) as a function of the discharge current in fluorescent lamp dimming. (author)

  10. Electrocardiogram voltage discordance: Interpretation of low QRS voltage only in the precordial leads.

    Science.gov (United States)

    Kim, Diana H; Verdino, Ralph J

    To define clinical correlates of low voltage isolated to precordial leads on the surface electrocardiogram (ECG). Low voltage (V) on the ECG is defined as QRS Vvoltage isolated to the precordial leads with normal limb lead voltages is unclear. Twelve-lead ECGs with QRS V>5mm in one or more limb leads and voltage was found in 256 of 150,000 ECGs (~0.2%). 50.4% of patients had discordant ECGs that correlated with classic etiologies, with a higher incidence of LV dilation in those with classic etiologies than those without. Low precordial voltage is associated with classic etiologies and LV dilation. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. On Secondary Control Approaches for Voltage Regulation in DC Microgrids

    DEFF Research Database (Denmark)

    Peyghami, Saeed; Mokhtari, Hossein; Davari, Pooya

    2017-01-01

    regulation on the load busses within a suitable range. Therefore, in addition to compensate the voltage drop of the primary controller, it is necessary to regulate the voltage of critical loads. In this paper, a new voltage regulation strategy is proposed to regulate the voltage of Micro-Grid (MG......Centralized or decentralized secondary controller is commonly employed to regulate the voltage drop raised by the primary controller. However, in the case of high capacity MGs and long feeders with much voltage drop on the line resistances, the conventional methods may not guarantee the voltage...

  12. A thermoelectric voltage effect in polyethylene oxide

    CERN Document Server

    Martin, B; Kliem, H

    2003-01-01

    The conductivity of polyethylene oxide (PEO) is described with a three-dimensional hopping model considering electrostatic interactions between the ions. Ions fluctuate over energy-barriers in a multi-well potential. To decide whether positive or negative charges are responsible for this conductivity, the thermoelectric voltage is measured. The samples are embedded between two aluminium-electrodes. The oxide on the interface between the electrodes and the PEO serves as a blocking layer. The temperature of each electrode is controlled by a Peltier element. A temperature step is applied to one electrode by changing the temperature of one of the Peltier elements. Due to this temperature gradient, the mobile charges fluctuate thermally activated from the warmer side to the colder side of the sample. The direction of the measured thermoelectric voltage indicates the type of mobile charges. It is found that positive charges are mobile. Further, it is shown that the absolute value of the thermoelectric voltage depen...

  13. Bias-voltage-controlled interlayer exchange coupling.

    Energy Technology Data Exchange (ETDEWEB)

    You, C.-Y.

    1999-03-29

    We propose a new system whose magnetization direction can be controlled by an applied bias voltage without an external magnetic field. The system consists of a four layered structure F{sub 1}/S/I/F{sub 2} (F{sub 1}, F{sub 2}: ferromagnets, S: spacer, I: insulator). An analytic expression for bias-voltage-controlled interlayer exchange coupling in this system is developed within a simple free-electron-like, one-dimensional approximation. According to the approach, the magnetic configurations of the two magnetic layers oscillate from antiferromagnetic to ferromagnetic with applied bias voltage. This implies that we can switch/rotate the magnetization direction without an external magnetic field. Possible applications of such a system are also discussed.

  14. Voltage control of cavity magnon polariton

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, S., E-mail: kaurs3@myumanitoba.ca; Rao, J. W.; Gui, Y. S.; Hu, C.-M., E-mail: hu@physics.umanitoba.ca [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada); Yao, B. M. [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada); National Laboratory for Infrared Physics, Chinese Academy of Sciences, Shanghai 200083 (China)

    2016-07-18

    We have experimentally investigated the microwave transmission of the cavity-magnon-polariton (CMP) generated by integrating a low damping magnetic insulator onto a 2D microwave cavity. The high tunability of our planar cavity allows the cavity resonance frequency to be precisely controlled using a DC voltage. By appropriately tuning the voltage and magnetic bias, we can observe the cavity photon magnon coupling and the magnetic coupling between a magnetostatic mode and the generated CMP. The dispersion of the generated CMP was measured by either tuning the magnetic field or the applied voltage. This electrical control of CMP may open up avenues for designing advanced on-chip microwave devices that utilize light-matter interaction.

  15. Semisupervised Community Detection by Voltage Drops

    Directory of Open Access Journals (Sweden)

    Min Ji

    2016-01-01

    Full Text Available Many applications show that semisupervised community detection is one of the important topics and has attracted considerable attention in the study of complex network. In this paper, based on notion of voltage drops and discrete potential theory, a simple and fast semisupervised community detection algorithm is proposed. The label propagation through discrete potential transmission is accomplished by using voltage drops. The complexity of the proposal is OV+E for the sparse network with V vertices and E edges. The obtained voltage value of a vertex can be reflected clearly in the relationship between the vertex and community. The experimental results on four real networks and three benchmarks indicate that the proposed algorithm is effective and flexible. Furthermore, this algorithm is easily applied to graph-based machine learning methods.

  16. Analysis of NSTX TF Joint Voltage Measurements

    Energy Technology Data Exchange (ETDEWEB)

    R, Woolley

    2005-10-07

    This report presents findings of analyses of recorded current and voltage data associated with 72 electrical joints operating at high current and high mechanical stress. The analysis goal was to characterize the mechanical behavior of each joint and thus evaluate its mechanical supports. The joints are part of the toroidal field (TF) magnet system of the National Spherical Torus Experiment (NSTX) pulsed plasma device operating at the Princeton Plasma Physics Laboratory (PPPL). Since there is not sufficient space near the joints for much traditional mechanical instrumentation, small voltage probes were installed on each joint and their voltage monitoring waveforms have been recorded on sampling digitizers during each NSTX ''shot''.

  17. Sensorless Control of IPMSM by Voltage Injection

    DEFF Research Database (Denmark)

    Matzen, Torben N.; Bech, Michael Møller

    2006-01-01

    In this paper a sensorless discrete current control of an Interior Permanent Magnet Synchrouns Motor (IPMSM) by voltage injection is designed and tested. The whole controller is operating in the dq-frame and for this reason the rotor position is essential to know, to transform between the station......In this paper a sensorless discrete current control of an Interior Permanent Magnet Synchrouns Motor (IPMSM) by voltage injection is designed and tested. The whole controller is operating in the dq-frame and for this reason the rotor position is essential to know, to transform between...... the stationary frame and the rotor xed dq-frame. To obtain the position even at standstill a sensorless scheme using voltage injection is added to the current controller....

  18. Voltage stability, bifurcation parameters and continuation methods

    Energy Technology Data Exchange (ETDEWEB)

    Alvarado, F.L. [Wisconsin Univ., Madison, WI (United States)

    1994-12-31

    This paper considers the importance of the choice of bifurcation parameter in the determination of the voltage stability limit and the maximum power load ability of a system. When the bifurcation parameter is power demand, the two limits are equivalent. However, when other types of load models and bifurcation parameters are considered, the two concepts differ. The continuation method is considered as a method for determination of voltage stability margins. Three variants of the continuation method are described: the continuation parameter is the bifurcation parameter the continuation parameter is initially the bifurcation parameter, but is free to change, and the continuation parameter is a new `arc length` parameter. Implementations of voltage stability software using continuation methods are described. (author) 23 refs., 9 figs.

  19. ESR melting under constant voltage conditions

    Energy Technology Data Exchange (ETDEWEB)

    Schlienger, M.E.

    1997-02-01

    Typical industrial ESR melting practice includes operation at a constant current. This constant current operation is achieved through the use of a power supply whose output provides this constant current characteristic. Analysis of this melting mode indicates that the ESR process under conditions of constant current is inherently unstable. Analysis also indicates that ESR melting under the condition of a constant applied voltage yields a process which is inherently stable. This paper reviews the process stability arguments for both constant current and constant voltage operation. Explanations are given as to why there is a difference between the two modes of operation. Finally, constant voltage process considerations such as melt rate control, response to electrode anomalies and impact on solidification will be discussed.

  20. CNFET Based Voltage Differencing Transconductance Amplifier

    Science.gov (United States)

    Laxya; Prasad, Dinesh; Mainuddin; Islam, S. S.

    2017-08-01

    In CMOS Technology basic Problem mainly includes dopant fluctuation, tunnelling effect and line edge roughness below 45nm technology. Carbon Nanotube based structures is better option for widen the Moore’s law due to its scalability channel electrostatics and higher mobility. In this manuscript we demonstrate an optimum design for linear property of CNTFET based VDTA at 32nm technology node. The proposed circuit consist of VDTA with CNTFET having two voltage input and two current outputs so that it works as voltage and transconductance operation to obtain the high performance. The minimum supply voltages of ±0.9V with 32nm technology mode are used. The CNTFET-VDTA performance is simulated on HSPICE. In this paper CNFET-based VDTA provides better results of DC transfer characteristics as compared with CMOS. All the simulation results are performed on HSPICE.

  1. Experimental validation of a high voltage pulse measurement method.

    Energy Technology Data Exchange (ETDEWEB)

    Cular, Stefan; Patel, Nishant Bhupendra; Branch, Darren W.

    2013-09-01

    This report describes X-cut lithium niobates (LiNbO3) utilization for voltage sensing by monitoring the acoustic wave propagation changes through LiNbO3 resulting from applied voltage. Direct current (DC), alternating current (AC) and pulsed voltage signals were applied to the crystal. Voltage induced shift in acoustic wave propagation time scaled quadratically for DC and AC voltages and linearly for pulsed voltages. The measured values ranged from 10 - 273 ps and 189 ps 2 ns for DC and non-DC voltages, respectively. Data suggests LiNbO3 has a frequency sensitive response to voltage. If voltage source error is eliminated through physical modeling from the uncertainty budget, the sensors U95 estimated combined uncertainty could decrease to ~0.025% for DC, AC, and pulsed voltage measurements.

  2. High-voltage test and measuring techniques

    CERN Document Server

    Hauschild, Wolfgang

    2014-01-01

    It is the intent of this book to combine high-voltage (HV) engineering with HV testing technique and HV measuring technique. Based on long-term experience gained by the authors as lecturer and researcher as well as member in international organizations, such as IEC and CIGRE, the book will reflect the state of the art as well as the future trends in testing and diagnostics of HV equipment to ensure a reliable generation, transmission and distribution of electrical energy. The book is intended not only for experts but also for students in electrical engineering and high-voltage engineering.

  3. Voltage control of DC islanded microgrids

    DEFF Research Database (Denmark)

    Tucci, Michele; Riverso, Stefano; Quintero, Juan Carlos Vasquez

    2015-01-01

    We propose a new decentralized control scheme for DC Islanded microGrids (ImGs) composed by several Distributed Generation Units (DGUs) with a general interconnection topology. Each local controller regulates to a reference value the voltage of the Point of Common Coupling (PCC) of the correspond......We propose a new decentralized control scheme for DC Islanded microGrids (ImGs) composed by several Distributed Generation Units (DGUs) with a general interconnection topology. Each local controller regulates to a reference value the voltage of the Point of Common Coupling (PCC...

  4. APPLICATION OF HIGH VOLTAGE DIVIDERS FOR POWER QUALITY INDICES MEASUREMENT

    Directory of Open Access Journals (Sweden)

    Y. L. Anokhin

    2017-12-01

    Full Text Available Introduction. Determination of power quality indices in high-voltage power grids allows to find the reasons for the deterioration of the power quality. The relevant national and International Standards for power quality contain relevant norms of quality indices and requirements for their accuracy measurement. Problem. The most complicated part in the process of measuring the power quality indices at high voltage is the selection of the corresponding high-voltage scale voltage converters. Therefore, comparing the requirements of IEC 61000-4-30 to high voltage scale voltage converters is an important task. Goal. Analysis of the International Standard IEC 61000-4-30 requirements feasibility for measuring the indices of power quality in high-voltage electrical networks using different types of high-voltage scale voltage converters. Methodology. Comparison of the requirements of IEC 61000-4-30 Standard to high-voltage scale voltage converters, when measuring power quality indices, with the characteristics of high voltage electromagnetic transformers used in Ukraine, and with promising developments of high-voltage converters of other types. Results. It is shown in the study that in order to fulfill some of the requirements for class A of IEC 61000-4-30, the characteristics of electromagnetic voltage transformers should be determined in the substation conditions using mobile calibration high-voltage laboratories. To meet all the requirements for Class A IEC 61000-4-30, it is recommended to use broadband high-voltage dividers of resistive-capacitive type. Originality. In study it is shown firstly that all the requirements of the IEC 61000-4-30 Standard for high-voltage scale voltage converters can be performed on the basis of the use of broadband resistive-capacitive damped voltage dividers. Practical value. Expositions of specific types of resistive-capacitive high-voltage dividers are presented, their parameters are confirmed by the results of state

  5. Optimal operation control of low-voltage grids with a high share of distributed power generation[Dissertation 17063]; Optimierte Betriebsfuehrung von Niederspannungsnetzen mit einem hohen Anteil an dezentraler Erzeugung

    Energy Technology Data Exchange (ETDEWEB)

    Malte, C. T.

    2007-07-01

    targets during development were that the system is able to manage autonomously a selected low-voltage grid including the installed (controllable) grid devices in order to improve power quality as well as to guarantee an economically optimised operation of the grid. Therefore, this system simplifies the integration of more and more DG units into already existing distribution grids and generates at the same time an economical and technical benefit for the concerned grid operator. All essential algorithms for the operation of PoMS have been developed within this PhD thesis. The approaches used in this work have been designed specially to fit for the application in limited low-voltage grid segments, e.g. area grids or industrial grids. It is a big advantage that the algorithms have been designed in such a general and scalable way, so that they can be used in a slightly modified form also for the optimisation of larger grids. From the very beginning the aim of the project was not only to design the system theoretically but also to test it under real conditions in an existing low-voltage grid. For that a fix time slot was given that had to be met under all circumstances. Therefore, the big challenge in the framework of this PhD thesis was not only to develop appropriate algorithms, but also to do this in the given time. With the successful test of PoMS it could be demonstrated that the developed algorithms are practical and allow an economically optimised grid management under real conditions. Further, it could be shown that PoMS can be used even for the operation of permanently islanded grids as well as for the operation of temporary islanded grids due to faults or interruptions on higher voltage levels ('Fault Ride Through'). (author)

  6. Production and Evaluation of Toxoplasma gondii Recombinant Sur­face Antigen 1 (SAG1 for Serodiagnosis of Acute and ChronicToxop­lasma Infection in Human Sera

    Directory of Open Access Journals (Sweden)

    M(Monavar Selseleh

    2012-09-01

    Full Text Available Background: The assays currently available for the detection of specific anti-Toxoplasma antibodies may vary in their abilities to detect serum immunoglobulins, due to the Lack of a purified standardized antigen. The aim of this study was evaluation the recombinant Toxoplasma gondii SAG1 antigen for the serodiagnosis of acute and chronic toxoplasmosis. Methods: This study describes an ELISA using recombinant SAG1 for detection of IgM and IgG antibodies against Toxoplasma gondii in human sera. Genomic DNA of T. gondii (RH Strain was isolated and PCR reaction was performed. Recovered DNA was cloned into PTZ57R cloning vector. The recombinant plasmid was detected by restriction analysis. The SAG1 gene was subcloned in the pET- 28a expression vector. Protein production was then induced with 1 mM isopropyl-D - thiogalactopyrano­side (IPTG. A total of 204 sera were tested using a commercial IgG and IgM ELISA kit (Trinity, USA as gold standard prior to testing them with the recombinant antigen. Results: Tested sera were divided into the following groups:(a The 74 T. gondii IgG positive (b 70 T.gondii IgM positive (c 60 sera who had no serological evidence of toxoplasmosis as negative sera.To determine the specificity of the test, we used other parasitic diseases including echinococusis (N=5, malaria (N=14, leishmania­sis (N=7,fasciolasis (N=4 , sterengyloidiasis (N=1 . Sensitivity and specificity of the generated recombinant IgG ELISA in comparison with commercial ELISA (Com ELISA were 93% and 95%, and the sensitivity and specificity of the generated recombinant IgM ELISA were 87% and 95% respectively. Conclusion: The results acquired here show that this antigen is useful for diagnostic purposes and could be replaced by lysed, whole cell antigens for diagnosis of chronic toxoplasmosis.

  7. Low-voltage and high-voltage TEM observations on MWCNTs of rat in vivo.

    Science.gov (United States)

    Sakaguchi, Norihito; Watari, Fumio; Yokoyama, Atsuro; Nodasaka, Yoshinobu; Ichinose, Hideki

    2009-01-01

    In the present study, we focused on the optimal conditions for observation of morphology and atomic structure of carbon nanotube (CNT) in vivo by transmission electron microscopy (TEM). Either low-voltage or high-voltage TEMs was chosen for the high-contrast or high-resolution imaging of subcutaneous tissue and the multi-wall CNT (MWCNT). The morphology and structure of each cell organelle were well recognized using the low-voltage TEM at 75 kV. Individual MWCNTs forming the cluster were also visible by the low-voltage TEM. On the contrary, the high-voltage TEM image at 1250 kV shows poor contrast on both the cell organelles and MWCNTs. However, graphene layers of MWCNT were clearly visible in the HRTEM image using the high-voltage TEM. The influence of the surrounding biological tissue can be disregarded by the high-energy electrons due to their weak scattering/absorption effect in the tissue. It was indicated that the usage of the high-voltage TEM is quite effective to the atomic structure analysis of nano-crystalline materials in vivo.

  8. Capturing power at higher voltages from arrays of microbial fuel cells without voltage reversal

    KAUST Repository

    Kim, Younggy

    2011-01-01

    Voltages produced by microbial fuel cells (MFCs) cannot be sustainably increased by linking them in series due to voltage reversal, which substantially reduces stack voltages. It was shown here that MFC voltages can be increased with continuous power production using an electronic circuit containing two sets of multiple capacitors that were alternately charged and discharged (every one second). Capacitors were charged in parallel by the MFCs, but linked in series while discharging to the circuit load (resistor). The parallel charging of the capacitors avoided voltage reversal, while discharging the capacitors in series produced up to 2.5 V with four capacitors. There were negligible energy losses in the circuit compared to 20-40% losses typically obtained with MFCs using DC-DC converters to increase voltage. Coulombic efficiencies were 67% when power was generated via four capacitors, compared to only 38% when individual MFCs were operated with a fixed resistance of 250 Ω. The maximum power produced using the capacitors was not adversely affected by variable performance of the MFCs, showing that power generation can be maintained even if individual MFCs perform differently. Longer capacitor charging and discharging cycles of up to 4 min maintained the average power but increased peak power by up to 2.6 times. These results show that capacitors can be used to easily obtain higher voltages from MFCs, allowing for more useful capture of energy from arrays of MFCs. © 2011 The Royal Society of Chemistry.

  9. Performance evaluation of automatic voltage regulators ...

    African Journals Online (AJOL)

    Performance of various Automatic Voltage Regulators (AVR's) in Nigeria and the causes of their inability to regulate at their set points have been investigated. The result indicates that the imported AVRs fail to give the 220 volts as displayed on the name plate at the specified low set point (such as 100, 120 volts etc) on ...

  10. Pulsed high voltage discharge induce hematologic changes

    African Journals Online (AJOL)

    STORAGESEVER

    2009-10-19

    Oct 19, 2009 ... The aim of this work to examine the effect of the gas-liquid hybrid discharge treatment system on some hematological ... liquid phase. The high energy plasma arc produces a pressure shock wave, electromagnetic radiations, .... through a 50 kilo-ohm resistor by a negative dc high-voltage power supply and ...

  11. Intermediate state trapping of a voltage sensor

    DEFF Research Database (Denmark)

    Lacroix, Jérôme J; Pless, Stephan Alexander; Maragliano, Luca

    2012-01-01

    transition pathway determined using the string method. The experimental results and computational analysis suggest that the phenotype of I241W may originate in the formation of a hydrogen bond between the indole nitrogen atom and the backbone carbonyl of R2. This work provides new information on intermediate...... states in voltage-gated ion channels with an approach that produces minimum chemical perturbation....

  12. Protection of Low Voltage CIGRE distribution Network

    DEFF Research Database (Denmark)

    Mustafa, Ghullam; Bak-Jensen, Birgitte; Bak, Claus Leth

    2013-01-01

    the inverters used for Photovoltaic (PV) and battery applications. The disconnection of the PV solar panels when in island mode is made by proposing switch dis-connecting devices. ABB is currently using these kinds of disconnection devices for the purpose of protecting solar panels against over voltages...

  13. PREDICTION OF VOLTAGE FLUCTUATION IN ELECTRIC GRIDS

    Directory of Open Access Journals (Sweden)

    V.A. Sapryka

    2013-06-01

    Full Text Available A mathematical model of voltage fluctuation versus parameters of power quality and power consumption is developed to allow predicting parameters of the power quality in electric grids. Application of the model will result in an electrical complex functioning optimization

  14. Stray voltage and milk quality: a review.

    Science.gov (United States)

    Reinemann, Douglas J

    2012-07-01

    If animal contact voltage reaches sufficient levels, animals coming into contact with grounded devices may receive a mild electric shock that can cause a behavioral response. At voltage levels that are just perceptible to the animal, behaviors indicative of perception (eg, flinches) may result with little change in normal routines. At higher exposure levels, avoidance behaviors may result. The direct effect of animal contact with electrical current can range from: • Mild behavioral reactions indicative of sensation, to • Involuntary muscle contraction, or twitching, to • Intense behavioral responses indicative of pain. The indirect effects of these behaviors can vary considerably depending on the specifics of the contact location, level of current flow, body pathway, frequency of occurrence, and many other factors related to the daily activities of animals. There are several common situations of concern in animal environments: • Animals avoiding certain exposure locations, which may result in: X Reduced water intake if exposure is required for animals to access watering devices, X Reduced feed intake if exposure is required for animals to accesses feeding devices or locations. • Difficulty of moving or handling animals in areas of voltage/current exposure• The physiologic implications of the release of stress hormones produced by contact with painful stimuli. The severity of response will depend on the amount of electrical current (measured in milliamps) flowing through the animal’s body, the pathway it takes through the body, and the sensitivity of the individual animal. The results of the combined current dose-response experiments, voltage exposure response experiments, and measurements of body and contact resistances is consistent with the lowest (worst case) cow + contact resistance as low as 500 as estimated by Lefcourt that may occur in some unusual situations on farms (firm application of the muzzle to a wet metallic watering device and hoof

  15. An Inexpensive Source of High Voltage

    Science.gov (United States)

    Saraiva, Carlos

    2012-01-01

    As a physics teacher I like recycling old apparatus and using them for demonstrations in my classes. In physics laboratories in schools, sources of high voltage include induction coils or electronic systems that can be bought from companies that sell lab equipment. But these sources can be very expensive. In this article, I will explain how you…

  16. Alternating current breakdown voltage of ice electret

    Science.gov (United States)

    Oshika, Y.; Tsuchiya, Y.; Okumura, T.; Muramoto, Y.

    2017-09-01

    Ice has low environmental impact. Our research objectives are to study the availability of ice as a dielectric insulating material at cryogenic temperatures. We focus on ferroelectric ice (iceXI) at cryogenic temperatures. The properties of iceXI, including its formation, are not clear. We attempted to obtain the polarized ice that was similar to iceXI under the applied voltage and cooling to 77 K. The polarized ice have a wide range of engineering applications as electronic materials at cryogenic temperatures. This polarized ice is called ice electret. The structural difference between ice electret and normal ice is only the positions of protons. The effects of the proton arrangement on the breakdown voltage of ice electret were shown because electrical properties are influenced by the structure of ice. We observed an alternating current (ac) breakdown voltage of ice electret and normal ice at 77 K. The mean and minimum ac breakdown voltage values of ice electret were higher than those of normal ice. We considered that the electrically weak part of the normal ice was improved by applied a direct electric field.

  17. Energy storage system in medium-sized voltage lines for the integration of decentralized fluctuating energy sources; Energiespeicher im Niederspannungsnetz zur Integration dezentraler, fluktuierender Energiequellen

    Energy Technology Data Exchange (ETDEWEB)

    Bodach, M.

    2006-06-30

    The solar radiation fluctuates due to atmospheric and planetary influences. Concerning PV systems, the changes from dark clouds to clear sky result in fast and very deep fluctuations of the time behaviour of the power output fed into the low voltage (LV) network by DC-AC-Converters. On the example of a daily recorded global radiation curve with a very short sampling time (regular interval time 1 s) the paper shows that short-term sags of the solar radiation are possible up to 80% of the previous value as a result of sudden and intensive changes of the density of the clouds. These disturbances of the quality of the generated electric power are directly transformed into the LV grids. If the number of PV systems connected to existing LV networks rises essentially, the fluctuating photovoltaic energy generation will achieve a very high importance and therefore not only the well-known, but also a lot of new problems will occur. They have already been investigated theoretically in different papers and they have also been proven quantitatively by own simulations. Improvements of the energy quality at the point of common coupling will be possible if the grid-coupled PV power plants are supplemented with suitable intelligent storage systems bridging the short-term sags. So the influence of the fluctuating radiation on the generated power can be fundamentally reduced. The developed intelligent short-term storage system smoothes out the generated power of the PV system by means of a storage. It is based on the very high capacity of an electric double layer (UltraCap, produced by EPCOS) and includes a complex electronic control system. The UltraCap has the required storing characteristics and has been adjusted to the system voltage by a highly sophisticated microprocessor controlled DC/DC-converter system. Such an intelligent storage system can also be used for the connection of other decentralised power generation units (e.g. fuel cells, block-unit heating power plant) to the

  18. Analysis of Voltage Support by Electric Vehicles and Photovoltaic in a Real Danish Low Voltage Network

    DEFF Research Database (Denmark)

    Knezovic, Katarina; Marinelli, Mattia; Juul Møller, René

    2014-01-01

    With conventional generating units being replaced by renewable sources which are not required to provide same high level of ancillary services, there is an increasing need for additional resources to achieve certain standards regarding frequency and voltage. This paper investigates the potential ...... with addressing the issues regarding voltage control at the expense of increased loading. Analysed real Danish low voltage network has been modelled in Matlab SimPowerSystems and is based on consumption and PV production data measured individually for number of households....

  19. Grid Voltage Modulated Control of Grid-Connected Voltage Source Inverters under Unbalanced Grid Conditions

    DEFF Research Database (Denmark)

    Li, Mingshen; Gui, Yonghao; Quintero, Juan Carlos Vasquez

    2017-01-01

    In this paper, an improved grid voltage modulated control (GVM) with power compensation is proposed for grid-connected voltage inverters when the grid voltage is unbalanced. The objective of the proposed control is to remove the power ripple and to improve current quality. Three power compensation...... objectives are selected to eliminate the negative sequence components of currents. The modified GVM method is designed to obtain two separate second-order systems for not only the fast convergence rate of the instantaneous active and reactive powers but also the robust performance. In addition, this method...

  20. Simple and compact capacitive voltage probe for measuring voltage impulses up to 0.5 MV.

    Science.gov (United States)

    Pecquois, R; Pecastaing, L; de Ferron, A; Rivaletto, M; Pignolet, P; Novac, B M; Smith, I R; Adler, R J

    2012-03-01

    The paper describes a simple and compact 0.5 MV high-voltage capacitive probe developed in common by Université de Pau (France) and Loughborough University (UK). Design details are provided, together with a simple and straightforward methodology developed to assess the characteristics of high-voltage probes. The technique uses a 4 kV pulsed arrangement combined with results from a 2D electric field solver and a thorough PSpice circuit analysis. Finally, a practical example of high-voltage measurement performed using such a probe during the development phase of a high power microwave generator is provided.