Bias-Voltage Stabilizer for HVHF Amplifiers in VHF Pulse-Echo Measurement Systems.

Science.gov (United States)

Choi, Hojong; Park, Chulwoo; Kim, Jungsuk; Jung, Hayong

2017-10-23

The impact of high-voltage-high-frequency (HVHF) amplifiers on echo-signal quality is greater with very-high-frequency (VHF, ≥100 MHz) ultrasound transducers than with low-frequency (LF, ≤15 MHz) ultrasound transducers. Hence, the bias voltage of an HVHF amplifier must be stabilized to ensure stable echo-signal amplitudes. We propose a bias-voltage stabilizer circuit to maintain stable DC voltages over a wide input range, thus reducing the harmonic-distortion components of the echo signals in VHF pulse-echo measurement systems. To confirm the feasibility of the bias-voltage stabilizer, we measured and compared the deviations in the gain of the HVHF amplifier with and without a bias-voltage stabilizer. Between -13 and 26 dBm, the measured gain deviations of a HVHF amplifier with a bias-voltage stabilizer are less than that of an amplifier without a bias-voltage stabilizer. In order to confirm the feasibility of the bias-voltage stabilizer, we compared the pulse-echo responses of the amplifiers, which are typically used for the evaluation of transducers or electronic components used in pulse-echo measurement systems. From the responses, we observed that the amplitudes of the echo signals of a VHF transducer triggered by the HVHF amplifier with a bias-voltage stabilizer were higher than those of the transducer triggered by the HVHF amplifier alone. The second, third, and fourth harmonic-distortion components of the HVHF amplifier with the bias-voltage stabilizer were also lower than those of the HVHF amplifier alone. Hence, the proposed scheme is a promising method for stabilizing the bias voltage of an HVHF amplifier, and improving the echo-signal quality of VHF transducers.

GECM-Based Voltage Stability Assessment Using Wide-Area Synchrophasors

Directory of Open Access Journals (Sweden)

Heng-Yi Su

2017-10-01

Full Text Available Voltage instability is a crucial issue in the secure operation of power grids. Several methods for voltage stability assessment were presented. Some of them are highly computationally intensive, while others are reported not to work properly under all circumstances. This paper proposes a new methodology based on the generator equivalent circuit model (GECM and the phasor measurement unit (PMU technology for online voltage stability monitoring of a power grid. First, the proposed methodology utilizes synchronized phasor (synchrophasor measurements to determine the impedance parameters of a transmission grid by means of the recursive least squares (RLS algorithm. Furthermore, it incorporates the dynamic models of generators to handle the cases with generator reactive power limit violations. After that, an enhanced voltage stability index with GECMs incorporated is developed for reliable and accurate voltage stability assessment. The proposed methodology was first demonstrated on several standard IEEE power systems, and then applied to a practical power system, the Taiwan power (Taipower system. The test results demonstrate the flexibility and effectiveness of the proposed methodology.

A method of accurate determination of voltage stability margin

Energy Technology Data Exchange (ETDEWEB)

Wiszniewski, A.; Rebizant, W. [Wroclaw Univ. of Technology, Wroclaw (Poland); Klimek, A. [AREVA Transmission and Distribution, Stafford (United Kingdom)

2008-07-01

In the process of developing power system disturbance, voltage instability at the receiving substations often contributes to deteriorating system stability, which eventually may lead to severe blackouts. The voltage stability margin at receiving substations may be used to determine measures to prevent voltage collapse, primarily by operating or blocking the transformer tap changing device, or by load shedding. The best measure of the stability margin is the actual load to source impedance ratio and its critical value, which is unity. This paper presented an accurate method of calculating the load to source impedance ratio, derived from the Thevenin's equivalent circuit of the system, which led to calculation of the stability margin. The paper described the calculation of the load to source impedance ratio including the supporting equations. The calculation was based on the very definition of voltage stability, which says that system stability is maintained as long as the change of power, which follows the increase of admittance is positive. The testing of the stability margin assessment method was performed in a simulative way for a number of power network structures and simulation scenarios. Results of the simulations revealed that this method is accurate and stable for all possible events occurring downstream of the device location. 3 refs., 8 figs.

GECM-Based Voltage Stability Assessment Using Wide-Area Synchrophasors

OpenAIRE

Heng-Yi Su; Tzu-Yi Liu

2017-01-01

Voltage instability is a crucial issue in the secure operation of power grids. Several methods for voltage stability assessment were presented. Some of them are highly computationally intensive, while others are reported not to work properly under all circumstances. This paper proposes a new methodology based on the generator equivalent circuit model (GECM) and the phasor measurement unit (PMU) technology for online voltage stability monitoring of a power grid. First, the proposed methodology...

A new reconfiguration scheme for voltage stability enhancement of radial distribution systems

International Nuclear Information System (INIS)

Arun, M.; Aravindhababu, P.

2009-01-01

Network reconfiguration is an operation problem, which entails altering the topological structure of the distribution feeders by rearranging the status of switches in order to obtain an optimal configuration in order to minimise the system losses. This paper presents a new reconfiguration algorithm that enhances voltage stability and improves the voltage profile besides minimising losses without incurring any additional cost for installation of capacitors, tap changing transformers and related switching equipment in the distribution system. Test results on a 69 node distribution system reveal the superiority of this algorithm.

Robust Frequency and Voltage Stability Control Strategy for Standalone AC/DC Hybrid Microgrid

Directory of Open Access Journals (Sweden)

Furqan Asghar

2017-05-01

Full Text Available The microgrid (MG concept is attracting considerable attention as a solution to energy deficiencies, especially in remote areas, but the intermittent nature of renewable sources and varying loads cause many control problems and thereby affect the quality of power within a microgrid operating in standalone mode. This might cause large frequency and voltage deviations in the system due to unpredictable output power fluctuations. Furthermore, without any main grid support, it is more complex to control and manage the system. In past, droop control and various other coordination control strategies have been presented to stabilize the microgrid frequency and voltages, but in order to utilize the available resources up to their maximum capacity in a positive way, new and robust control mechanisms are required. In this paper, a standalone microgrid is presented, which integrates renewable energy-based distributed generations and local loads. A fuzzy logic-based intelligent control technique is proposed to maintain the frequency and DC (direct current-link voltage stability for sudden changes in load or generation power. Also from a frequency control perspective, a battery energy storage system (BESS is suggested as a replacement for a synchronous generator to stabilize the nominal system frequency as a synchronous generator is unable to operate at its maximum efficiency while being controlled for stabilization purposes. Likewise, a super capacitor (SC and BESS is used to stabilize DC bus voltages even though maximum possible energy is being extracted from renewable generated sources using maximum power point tracking. This newly proposed control method proves to be effective by reducing transient time, minimizing the frequency deviations, maintaining voltages even though maximum power point tracking is working and preventing generators from exceeding their power ratings during disturbances. However, due to the BESS limited capacity, load switching

Dispatching power system for preventive and corrective voltage collapse problem in a deregulated power system

Science.gov (United States)

Alemadi, Nasser Ahmed

Deregulation has brought opportunities for increasing efficiency of production and delivery and reduced costs to customers. Deregulation has also bought great challenges to provide the reliability and security customers have come to expect and demand from the electrical delivery system. One of the challenges in the deregulated power system is voltage instability. Voltage instability has become the principal constraint on power system operation for many utilities. Voltage instability is a unique problem because it can produce an uncontrollable, cascading instability that results in blackout for a large region or an entire country. In this work we define a system of advanced analytical methods and tools for secure and efficient operation of the power system in the deregulated environment. The work consists of two modules; (a) contingency selection module and (b) a Security Constrained Optimization module. The contingency selection module to be used for voltage instability is the Voltage Stability Security Assessment and Diagnosis (VSSAD). VSSAD shows that each voltage control area and its reactive reserve basin describe a subsystem or agent that has a unique voltage instability problem. VSSAD identifies each such agent. VS SAD is to assess proximity to voltage instability for each agent and rank voltage instability agents for each contingency simulated. Contingency selection and ranking for each agent is also performed. Diagnosis of where, why, when, and what can be done to cure voltage instability for each equipment outage and transaction change combination that has no load flow solution is also performed. A security constrained optimization module developed solves a minimum control solvability problem. A minimum control solvability problem obtains the reactive reserves through action of voltage control devices that VSSAD determines are needed in each agent to obtain solution of the load flow. VSSAD makes a physically impossible recommendation of adding reactive

Development of a terminal voltage stabilization system for the FOTIA ...

Indian Academy of Sciences (India)

Abstract. A terminal voltage stabilization system for the folded tandem ion accelerator (FOTIA) was developed and is in continuous use. The system achieves good voltage stabilization, eliminates ground loops and noise interference. It incorporates a correcting circuit for compensating the mains frequency variations in the ...

Angle Stability Analysis for Voltage-Controlled Converters

DEFF Research Database (Denmark)

Lin, Hengwei; Jia, Chenxi; Guerrero, Josep M.

2017-01-01

a criterion to analyze the quasi-steady angle stability and the direct current (DC) side stability for VSCs. The operating limit and the angle instability mechanism are revealed, which is generally applicable to the voltage-controlled converters. During the analysis, the influence of the parameters on angle...... stability is studied. Further, the difference on instability mechanism between power electronic converters and synchronous generators are explained in detail. Finally, experiment results with corrective actions verify the analysis....

Distributed stability control using intelligent voltage-margin relay

Energy Technology Data Exchange (ETDEWEB)

Wiszniewski, A.; Rebizant, W. [Wroclaw Univ. of Technology (Poland); Klimek, A. [Powertech Labs Inc., Surrey, BC (Canada)

2010-07-01

This paper presented an intelligent relay that operates if the load to source impedance ratio decreases to a level that is dangerously close to the stability limit, which leads to power system blackouts. The intelligent voltage-margin/difference relay installed at receiving substations automatically initiates action if the voltage stability margin drops to a dangerously low level. The relay decides if the tap changing devices are to be blocked and if under-voltage load shedding should be initiated, thereby mitigating an evolving instability. The intelligent relay has two levels of operation. At the first stage, which corresponds to the higher load to source impedance ratio, the relay initiates blocking of the tap changer. At the second stage, corresponding to the lower source to load impedance ratio, load shedding is initiated. The relay operates when the load to source impedance ratio reaches a certain predetermined level, but it does not depend either on the level of the source voltage or on the difference of source and load impedance phase angles. The algorithm for the relay is relatively simple and uses only locally available signals. Consequently, the transformer is well controlled to eliminate the cases of voltage instability. 6 refs., 7 figs.

Temperature Stabilized Characterization of High Voltage Power Supplies

CERN Document Server

Krarup, Ole

2017-01-01

High precision measurements of the masses of nuclear ions in the ISOLTRAP experiment relies on an MR-ToF. A major source of noise and drift is the instability of the high voltage power supplies employed. Electrical noise and temperature changes can broaden peaks in time-of-flight spectra and shift the position of peaks between runs. In this report we investigate how the noise and drift of high-voltage power supplies can be characterized. Results indicate that analog power supplies generally have better relative stability than digitally controlled ones, and that the high temperature coefficients of all power supplies merit efforts to stabilize them.

A comparative study of voltage stability indices in a power system

Energy Technology Data Exchange (ETDEWEB)

Sinha, A.K. [I.I.T., Kharagpur (India). Dept. of Electrical Engineering; Hazarika, D. [Assam Engineering College (India)

2000-11-01

The paper compares the effectiveness of voltage stability indices in providing information about the proximity of voltage instability of a power system. Three simple voltage stability indices are proposed and their effectiveness is compared with some of the recently proposed indices. The comparison is carried out over a wide range of system operating conditions by changing the load power factor and feeder X/R ratios. Test results for the IEEE 57 bus and IEEE 118 bus system are presented. (author)

A 600kV 15mA Cockcroft-Walton high-voltage power supply with high stability and low-ripple voltage

International Nuclear Information System (INIS)

Su Tongling; Zhang Yimin; Chen Shangwen; Liu Yantong; Lv Huiyi; Liu Jiangtao

2006-01-01

A Cockcroft-Walton high-voltage power supply with high stability and low-ripple voltage has been developed. This power supply has been operated in a ns pulse neutron generator. The maximum non-load voltage is 600kV while the working voltage and load current are 550kV and 15mA, respectively. The tested results indicate that when the power supply is operated at 300kV, 6.7mA and the input voltage varies +/-10%, the long-term stability of the output voltage is S=(0.300-1.006)x10 -3 . The ripple voltage is δU P-P =6.2V at 300kV, 6.8-8.3mA and the ratio of δU P-P to the output voltage V H is δU P-P /V H =2.1x10 -5

Analysis on voltage stability of PFN in modulator using De-Qing network

International Nuclear Information System (INIS)

Wang Dong; Zhang Yongming; Zhu Fuquan

1987-01-01

Using the numerical simulation of PFN charging circuit and De-Qing network, a study of voltage stability of BEPC 80 MW klystron pulse modulator has been carried out. The results presented in the paper indicate the quantitative correlation between leakage inductance and voltage stability

Harmonics and voltage stability analysis in power systems including ...

Indian Academy of Sciences (India)

R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

two parameters affecting power quality – harmonics and voltage stability. ... is necessary to pay attention to energy system stability in the planning, management, and ... where k ∈ {m, m + 1,... ,n} and n is total number of the buses in the system.

Power system voltage stability and agent based distribution automation in smart grid

Science.gov (United States)

Nguyen, Cuong Phuc

2011-12-01

Our interconnected electric power system is presently facing many challenges that it was not originally designed and engineered to handle. The increased inter-area power transfers, aging infrastructure, and old technologies, have caused many problems including voltage instability, widespread blackouts, slow control response, among others. These problems have created an urgent need to transform the present electric power system to a highly stable, reliable, efficient, and self-healing electric power system of the future, which has been termed "smart grid". This dissertation begins with an investigation of voltage stability in bulk transmission networks. A new continuation power flow tool for studying the impacts of generator merit order based dispatch on inter-area transfer capability and static voltage stability is presented. The load demands are represented by lumped load models on the transmission system. While this representation is acceptable in traditional power system analysis, it may not be valid in the future smart grid where the distribution system will be integrated with intelligent and quick control capabilities to mitigate voltage problems before they propagate into the entire system. Therefore, before analyzing the operation of the whole smart grid, it is important to understand the distribution system first. The second part of this dissertation presents a new platform for studying and testing emerging technologies in advanced Distribution Automation (DA) within smart grids. Due to the key benefits over the traditional centralized approach, namely flexible deployment, scalability, and avoidance of single-point-of-failure, a new distributed approach is employed to design and develop all elements of the platform. A multi-agent system (MAS), which has the three key characteristics of autonomy, local view, and decentralization, is selected to implement the advanced DA functions. The intelligent agents utilize a communication network for cooperation and

Application of SMES in wind farm to improve voltage stability

International Nuclear Information System (INIS)

Shi, J.; Tang, Y.J.; Ren, L.; Li, J.D.; Chen, S.J.

2008-01-01

For the wind farms introducing doubly fed induction generators (DFIGs), voltage stability is an essential issue which influences their widely integration into the power grid. This paper proposes the application of superconducting magnetic energy storage (SMES) in the power system integrated with wind farms. SMES can control the active and reactive power flow, realizing the operation in four quadrants independently. The introducing of SMES can smooth the output power flow of the wind farms, and supply dynamic voltage support. Using MATLAB/SIMULINK, the models of the DFIG, the power grid connected and the SMES are created. Simulation results show that the voltage stability of the power system integrated with wind farms can be improved considerably

Synchrophasor-Based Online Coherency Identification in Voltage Stability Assessment

Directory of Open Access Journals (Sweden)

ADEWOLE, A. C.

2015-11-01

Full Text Available This paper presents and investigates a new measurement-based approach in the identification of coherent groups in load buses and synchronous generators for voltage stability assessment application in large interconnected power systems. A hybrid Calinski-Harabasz criterion and k-means clustering algorithm is developed for the determination of the cluster groups in the system. The proposed method is successfully validated by using the New England 39-bus test system. Also, the performance of the voltage stability assessment algorithm using wide area synchrophasor measurements from the key synchronous generator in each respective cluster was tested online for the prediction of the system's margin to voltage collapse using a testbed comprising of a Programmable Logic Controller (PLC in a hardware-in-the-loop configuration with the Real-Time Digital Simulator (RTDS and Phasor Measurement Units (PMUs.

Influence of dump voltage and allowable temperature rise on stabilizer requirements in superconducting coils

International Nuclear Information System (INIS)

Schwenterly, S.W.

1988-01-01

A superconducting winding must have enough stabilizer to satisfy two sets of criteria. During normal operation, the amount of stabilizer must be large enough either to make the coil unconditionally stable or to give a certain desired stability margin. Once a dump occurs, the amount of stabilizer must be large enough to carry the current without generating excessive dump voltages or allowing the winding to exceed a certain maximum temperature (and maximum pressure, in the case of force-cooled coils). The voltage criterion often dominates for very large coil systems, but it is frequently ignored in initial design studies. This paper gives some simple relations between the dump voltage and the stored energy, temperature rise, and coil geometry that are useful in scooping the required amount of stabilizer. Comparison with some recently proposed fusion magnet system designs indicates that excessive dump voltages could result in some cases. High-temperature superconductors may require more stabilizer than the conventional alloys. Calculations with simple model coil systems indicate how trade-offs between various coil parameters affect the dump voltage. 12 refs., 1 fig., 1 tab

Stability of DC Voltage Droop Controllers in VSC HVDC Systems

DEFF Research Database (Denmark)

Thams, Florian; Suul, Jon Are; D’Arco, Salvatore

2015-01-01

Future multi-terminal HVDC systems are expected to utilize dc voltage droop controllers and several control implementations have been proposed in literature. This paper first classifies possible dc droop implementations in a simple framework. Then, the small-signal stability of a VSC-based conver......Future multi-terminal HVDC systems are expected to utilize dc voltage droop controllers and several control implementations have been proposed in literature. This paper first classifies possible dc droop implementations in a simple framework. Then, the small-signal stability of a VSC...

Reactive power dispatch considering voltage stability with seeker optimization algorithm

Energy Technology Data Exchange (ETDEWEB)

Dai, Chaohua; Chen, Weirong; Zhang, Xuexia [The School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Zhu, Yunfang [Department of Computer and Communication Engineering, E' mei Campus, Southwest Jiaotong University, E' mei 614202 (China)

2009-10-15

Optimal reactive power dispatch (ORPD) has a growing impact on secure and economical operation of power systems. This issue is well known as a non-linear, multi-modal and multi-objective optimization problem where global optimization techniques are required in order to avoid local minima. In the last decades, computation intelligence-based techniques such as genetic algorithms (GAs), differential evolution (DE) algorithms and particle swarm optimization (PSO) algorithms, etc., have often been used for this aim. In this work, a seeker optimization algorithm (SOA) based method is proposed for ORPD considering static voltage stability and voltage deviation. The SOA is based on the concept of simulating the act of human searching where search direction is based on the empirical gradient by evaluating the response to the position changes and step length is based on uncertainty reasoning by using a simple Fuzzy rule. The algorithm's performance is studied with comparisons of two versions of GAs, three versions of DE algorithms and four versions of PSO algorithms on the IEEE 57 and 118-bus power systems. The simulation results show that the proposed approach performed better than the other listed algorithms and can be efficiently used for the ORPD problem. (author)

Available transfer capability calculation considering voltage stability margin

International Nuclear Information System (INIS)

Pan, Xiong; Xu, Guoyu

2005-01-01

To make the electricity trades carry out successfully, the calculation of available transfer capability (ATC) must coordinate the relationship between the security and economic benefits. In this paper, a model for ATC calculations accorded with trade-off mechanism in electricity market was set up. The impact of branch outage contingency on the static voltage stability margin was analyzed, and contingency ranking was performed through sensitivity indices of branch flows with respect to the loading margin. Optimal power flow based on primal-dual interior point method was applied to obtain ATC when the N-1 security constraints were included. The calculation results of IEEE 30-bus and IEEE 118-bus systems show that the proposed model and method are valid. (author) (N-1 security constraints; Electricity market; Available transfer capability; Optimal power flow; Voltage stability)

Dynamic voltage stability constrained congestion management framework for deregulated electricity markets

International Nuclear Information System (INIS)

Amjady, Nima; Hakimi, Mahmood

2012-01-01

Highlights: ► A new congestion management method for electricity markets is proposed. ► The proposed method includes dynamic models of generators and loads. ► Dynamic voltage stability limits are properly modeled in the proposed method. ► The proposed method is compared with several other congestion management methods. ► It leads to a more robust power system with a lower congestion management cost. - Abstract: Congestion management is an important part of power system operation in today deregulated electricity markets. However, congestion management is traditionally performed based on static analysis tools, while these tools may not correctly capture dynamic voltage stability limits of a power system. In this paper, a new congestion management framework considering dynamic voltage stability boundary of power system is proposed. For this purpose, precise dynamic modeling of power system equipment, including generators and loads, is incorporated into the proposed congestion management framework. The proposed method alleviates congestion with a lower congestion management cost and more dynamic voltage stability margin, resulting in a more robust power system, compared with the previous congestion management methods. The validity of proposed congestion management framework is studied based on the New England 39-bus power system. The obtained results confirm the validity of the developed approach.

Fuzzy Load-Shedding Strategy Considering Photovoltaic Output Fluctuation Characteristics and Static Voltage Stability

Directory of Open Access Journals (Sweden)

Sheng Li

2018-03-01

Full Text Available Based on the equilibrium point equations of a classic three-node system integrated with a large-scale photovoltaic cell (PV power plant, the impact of PV output fluctuation on the saddle-node bifurcation (SNB was derived and analyzed. When PV runs in a unity power factor and the PV output active power Ppv is not too large (several hundred MW and below, the PV output fluctuation has little effect on the SNB point position and load margin index, so that the load margin index can be calculated online using the SNB point at Ppv = 0 pu. On the other hand, the local reactive power compensation in the load center can effectively raise the load bus voltage and make the voltage stability problem become more concealed; the traditional under-voltage load-shedding (UVLS strategy only carries out load shedding when the bus voltage amplitude is below the specified value and cannot effectively maintain the system static voltage stability in some occasions. In this paper, a fuzzy load-shedding strategy considering the impact of PV output fluctuations for the large-scale PV grid-connected system was designed, taking the load bus voltage amplitude and load margin index as fuzzy input variables, and the load-shedding command as a fuzzy output variable. Nine fuzzy IF-THEN rules were extracted for the fuzzy controller and the corresponding practical calculation method of load-shedding quantity was put forward. The simulation results of the classic three-node system and IEEE 14-bus system, both with a 100 MW PV power plant, verified the effectiveness of the fuzzy load-shedding controller whose input variable load margin index was calculated using the SNB point when the PV active power output was 0. The designed fuzzy load-shedding strategy can compensate for the defect—that the traditional UVLS strategy cannot effectively guarantee the system static voltage stability—and it can be widely used in power grids integrated with PV power plants whose scales are at a

Stability of high current diode under 100-nanosecond-pulse voltage

International Nuclear Information System (INIS)

Lai Dingguo; Qiu Aici; Zhang Yongmin; Huang Jianjun; Ren Shuqing; Yang Li

2012-01-01

Stability of high current diode under pulse voltage with 80 ns and 34 ns rise time was studied on the flash Ⅱ accelerator. Influence of rise time of diode voltage on startup time and cathode emission uniformity and repeatability of diode impedance was analyzed by comparing the experimental results with numerically simulated results, and the influence mechanism was discussed. The startup time of diode increases with the increasing of rise time of voltage, and the repeatability of diode impedance decreases. Discal plane cathode is prone to emit rays intensely in the center area, the time that plasma covers the surface of the cathode increases and the shielding effect has more impact on cathode emission according to the increase of rise time. Local intense emission on the cathode increases expansion speed of plasma and reduces the effective emission area. The stability of characteristic impedance of diode under a pulse voltage with slow rise time is decreased by the combined action of expansion speed of plasma and the effective emission area. (authors)

Development of real-time voltage stability monitoring tool for power system transmission network using Synchrophasor data

Science.gov (United States)

Pulok, Md Kamrul Hasan

Intelligent and effective monitoring of power system stability in control centers is one of the key issues in smart grid technology to prevent unwanted power system blackouts. Voltage stability analysis is one of the most important requirements for control center operation in smart grid era. With the advent of Phasor Measurement Unit (PMU) or Synchrophasor technology, real time monitoring of voltage stability of power system is now a reality. This work utilizes real-time PMU data to derive a voltage stability index to monitor the voltage stability related contingency situation in power systems. The developed tool uses PMU data to calculate voltage stability index that indicates relative closeness of the instability by producing numerical indices. The IEEE 39 bus, New England power system was modeled and run on a Real-time Digital Simulator that stream PMU data over the Internet using IEEE C37.118 protocol. A Phasor data concentrator (PDC) is setup that receives streaming PMU data and stores them in Microsoft SQL database server. Then the developed voltage stability monitoring (VSM) tool retrieves phasor measurement data from SQL server, performs real-time state estimation of the whole network, calculate voltage stability index, perform real-time ranking of most vulnerable transmission lines, and finally shows all the results in a graphical user interface. All these actions are done in near real-time. Control centers can easily monitor the systems condition by using this tool and can take precautionary actions if needed.

Online Voltage Stability Assessment for Load Areas Based on the Holomorphic Embedding Method

DEFF Research Database (Denmark)

Liu, Chengxi; Wang, Bin; Hu, Fengkai

2018-01-01

This paper proposes an online steady-state voltage stability assessment scheme to evaluate the proximity to voltage collapse at each bus of a load area. Using a non-iterative holomorphic embedding method (HEM) with a proposed physical germ solution, an accurate loading limit at each load bus can...... be calculated based on online state estimation on the entire load area and a measurement-based equivalent for the external system. The HEM employs a power series to calculate an accurate Power-Voltage (P-V) curve at each load bus and accordingly evaluates the voltage stability margin considering load variations...... and then demonstrated on a load area of the Northeast Power Coordinating Council (NPCC) 48-generator, 140-bus power system....

Dynamic Voltage Stability Studies using a Modified IEEE 30-Bus System

Directory of Open Access Journals (Sweden)

Oluwafemi Emmanuel Oni

2016-09-01

Full Text Available Power System stability is an essential study in the planning and operation of an efficient, economic, reliable and secure electric power system because it encompasses all the facet of power systems operations, from planning, to conceptual design stages of the project as well as during the systems operating life span. This paper presents different scenario of power system stability studies on a modified IEEE 30-bus system which is subjected to different faults conditions. A scenario whereby the longest high voltage alternating current (HVAC line is replaced with a high voltage direct current (HVDC line was implemented. The results obtained show that the HVDC line enhances system stability more compared to the contemporary HVAC line. Dynamic analysis using RMS simulation tool was used on DigSILENT PowerFactory.

Technical and economic considerations of extra high voltage power transmission

Energy Technology Data Exchange (ETDEWEB)

Kahnt, R

1966-09-01

The reasons for the employment of higher transmission voltages are listed and the points decisive for the selection of three phase ac or dc systems are reviewed. The technical and economic problems arising in three phase extra high voltage transmission are discussed. These include selection of voltage, economical design of power lines, insulation problems, power supply dependability, equipment rating and reactive power and stability problems.

Voltage stability issues for a benchmark grid model including large scale wind power

DEFF Research Database (Denmark)

Eek, J.; Lund, T.; Marzio, G. Di

2006-01-01

The objective of the paper is to investigate how the voltage stability of a relatively weak network after a grid fault is affected by the connection of a large wind park. A theoretical discussion of the stationary and dynamic characteristics of the Short Circuit Induction Generator and the Doubly...... Fed Induction Generator is given. Further, a case study of a wind park connected to the transmission system through an existing regional 132 kV regional distribution line is presented. For the SCIG it is concluded that a stationary torque curve calculated under consideration of the impedance...... of the network and saturation of the external reactive power compensation units provides a good basis for evaluation of the voltage stability. For the DFIG it is concluded that the speed stability limit is mainly determined by the voltage limitation of the rotor converter...

A pragmatic approach to voltage stability analysis of large power systems

Energy Technology Data Exchange (ETDEWEB)

Sarmiento, H.G.; Pampin, G. [Inst. de Investigaciones Electricas, Morelos (Mexico); Diaz de Leon, J.A. [American Superconductor, Middleton, WI (United States)

2008-07-01

A methodology for performing voltage stability analyses for large power systems was presented. Modal and time-domain analyses were used for selection and siting solutions for potential voltage instability and collapse. Steady state systems were used to compute the smallest eigenvalues and associated eigenvalues of a reduced Jacobean matrix. The eigenvalues were used to provide a relative measure of proximity to voltage instability. The analysis was applied to provide an indication of a network's proximity to voltage collapse. Negative eigenvalues were representative of voltage instability conditions, while small positive values indicated proximity to voltage instability. The analysis technique was used to identify buses, lines, and generators prone to voltage instabilities for a 10-node network. A comparative analysis of results obtained from modal and time domain analyses were used to identify areas vulnerable to voltage instability conditions. Pre-fault, fault, and post-fault conditions were analyzed statically and dynamically. Results of the study showed that the combined method can be used to identify and place reactive power compensation solutions for voltage collapses in electric networks. 20 refs., 5 tabs., 7 figs.

Strategies for Voltage Control and Transient Stability Assessment

Energy Technology Data Exchange (ETDEWEB)

Hiskens, Ian A.

2013-09-25

As wind generation grows, its influence on power system performance will becoming increasingly noticeable. Wind generation di ffers from traditional forms of generation in numerous ways though, motivating the need to reconsider the usual approaches to power system assessment and performance enhancement. The project has investigated the impact of wind generation on transient stability and voltage control, identifying and addressing issues at three distinct levels of the power system: 1) at the device level, the physical characteristics of wind turbine generators (WTGs) are quite unlike those of synchronous machines, 2) at the wind-farm level, the provision of reactive support is achieved through coordination of numerous dissimilar devices, rather than straightforward generator control, and 3) from a systems perspective, the location of wind-farms on the sub-transmission network, coupled with the variability inherent in their power output, can cause complex voltage control issues. The project has sought to develop a thorough understanding of the dynamic behaviour of type-3 WTGs, and in particular the WECC generic model. The behaviour of such models is governed by interactions between the continuous dynamics of state variables and discrete events associated with limits. It was shown that these interactions can be quite complex, and may lead to switching deadlock that prevents continuation of the trajectory. Switching hysteresis was proposed for eliminating deadlock situations. Various type-3 WTG models include control blocks that duplicate integrators. It was shown that this leads to non-uniqueness in the conditions governing steady-state, and may result in pre- and post-disturbance equilibria not coinciding. It also gives rise to a zero eigenvalue in the linearized WTG model. In order to eliminate the anomalous behaviour revealed through this investigation, WECC has now released a new generic model for type-3 WTGs. Wind-farms typically incorporate a variety of

Technical and economic considerations of extra high voltage power transmission

Energy Technology Data Exchange (ETDEWEB)

Kahnt, R

1966-09-01

The reasons for the employment of higher transmission voltages are listed and the points decisive for the selection of three phase ac or dc systems are reviewed. This is followed by treatment of the technical and economic problems arising in three phase-extra high voltage transmission. These include selection of voltage, economical design of power lines, insulation problems, power supply dependability, equipment rating, and reactive power and stability problems.

Stability Boundaries for Offshore Wind Park Distributed Voltage Control

DEFF Research Database (Denmark)

Gryning, Mikkel P.S.; Wu, Qiuwei; Kocewiak, Lukasz

2017-01-01

pilot control. Using data from the actual wind power plant, all stabilizing subsystem voltage proportional-integral controller parameters are first characterized based on their Hurwitz signature. Inner loop current control is then designed using Internal Mode Control principles, and guidelines for feed......In order to identify mechanisms causing slow reactive power oscillations observed in an existing offshore wind power plant, and be able to avoid similar events in the future, voltage control is studied in this paper for a plant with a static synchronous compensator, type-4 wind turbines and a park...... forward filter design are given to obtain required disturbance rejection properties. The paper contributes by providing analytical relations between power plant control, droop, sampling time, electrical parameters and voltage control characteristics, and by assessing frequencies and damping of reactive...

On Stability of Voltage Source Inverters in Weak Grids

DEFF Research Database (Denmark)

Adib, Aswad; Mirafza, Behrooz; Wang, Xiongfei

2018-01-01

As the number of inverters increases in the power grid, the stability of grid-tied inverters becomes an important concern for the power industry. In particular, a weak grid can lead to voltage fluctuations at the inverter terminals and consequently cause inverter instability. In this paper, impac...

Identification of voltage stability condition of a power system using measurements of bus variables

Directory of Open Access Journals (Sweden)

Durlav Hazarika

2014-12-01

Full Text Available Several online methods were proposed for investigating the voltage stability condition of an interconnected power system using the measurements of voltage and current phasors at a bus. For this purpose, phasor measurement units (PMUs are used. A PMU is a device which measures the electrical waves on an electrical network, using a common time source (reference bus for synchronisation. This study proposes a method for online monitoring of voltage stability condition of a power system using measurements of bus variables namely – (i real power, (ii reactive power and (iii bus voltage magnitude at a bus. The measurements of real power, reactive power and bus voltage magnitude could be extracted/captured from a smart energy meter. The financial involvement for implementation of the proposed method would significantly lower compared with the PMU-based method.

New challenge for the Norwegian electric power market: A free market of power creates stability problems

International Nuclear Information System (INIS)

Gjengedal, T.; Rabbe, O.; Ongstad, E.; Uhlen, K.; Hauger, B.; Vormedal, L.; Lysheim, D.

1997-01-01

The article relates to problems of grid stability as a consequence of market-based power turnover. In combination with special hydrologic conditions, new approaches are formed concerning power production and transmission. Efficient counter-acting efforts must be initiated at an early stage for power system stabilization also concerning future innovations from the year of 2000. Examples on the development of systems of static magnetization and damping, problems concerning dampers, power grid testing, digital regulators, faults in high voltage 3-phase systems, and evaluation of measures of improvement are discussed. 10 figs

Small disturbance voltage stability assessment of power systems by modal analysis and dynamic simulation

International Nuclear Information System (INIS)

Amjady, Nima; Ansari, Mohammad Reza

2008-01-01

The introduction of liberalized electricity markets in many countries has resulted in more highly stressed power systems. On the other hand, operating points of a power system are acceptable in the feasible region, which is surrounded by the borders of different stabilities. Power system instability is critical for all participants of the electricity market. Determination of different stability margins can result in the optimum utilization of power system with minimum risk. This paper focuses on the small disturbance voltage stability, which is an important subset of the power system global stability. This kind of voltage stability is usually evaluated by static analysis tools such as continuation power flow, while it essentially has dynamic nature. Besides, a combination of linear and nonlinear analysis tools is required to correctly analyze it. In this paper, a hybrid evaluation method composed of static, dynamic, linear, and nonlinear analysis tools is proposed for this purpose. Effect of load scenario, generation pattern, branch and generator contingency on the small disturbance voltage stability are evaluated by the hybrid method. The test results are given for New England and IEEE68 bus test systems. (author)

Voltage Stability Bifurcation Analysis for AC/DC Systems with VSC-HVDC

Directory of Open Access Journals (Sweden)

Yanfang Wei

2013-01-01

Full Text Available A voltage stability bifurcation analysis approach for modeling AC/DC systems with VSC-HVDC is presented. The steady power model and control modes of VSC-HVDC are briefly presented firstly. Based on the steady model of VSC-HVDC, a new improved sequential iterative power flow algorithm is proposed. Then, by use of continuation power flow algorithm with the new sequential method, the voltage stability bifurcation of the system is discussed. The trace of the P-V curves and the computation of the saddle node bifurcation point of the system can be obtained. At last, the modified IEEE test systems are adopted to illustrate the effectiveness of the proposed method.

Harmonics and voltage stability analysis in power systems including

Indian Academy of Sciences (India)

In this study, non-sinusoidal quantities and voltage stability, both known as power quality criteria, are examined together in detail. The widespread use of power electronics elements cause the existence of significant non-sinusoidal quantities in the system. These non-sinusoidal quantities can create serious harmonic ...

Stability Analysis of a Voltage-Based Controller for Robot Manipulators

Directory of Open Access Journals (Sweden)

Jorge Orrante-Sakanassi

2013-01-01

Full Text Available A voltage-based control scheme for robot manipulators has been presented in recent literature, where feedback linearization is applied in the electrical equations of the DC motors in order to cancel the electrical current terms. However, in this paper we show that this control technique generates a system of the form Ex = Ax + Bu, where E is a singular matrix, that is to say, a generalized state-space system or singular system. This paper introduces a formal stability analysis of the respective system by considering the state-space equation as a singular system. Furthermore, in order to avoid the singularity of the closed-loop system, modified voltage-based control schemes are proposed, whose Lyapunov stability analyses conclude semiglobal asymptotic stability for the set-point control case and uniform boundedness of the solutions and semiglobal convergence of the position, as well as velocity errors for the tracking control case. The proposed control systems are simulated for the tracking and set-point cases using the CICESE Pelican robot driven by DC motors.

Evaluation of HVDC interconnection models for considering its impact in real-time voltage stability assessment

DEFF Research Database (Denmark)

Perez, Angel; Jóhannsson, Hjörtur; Lund, P.

2015-01-01

An approach to evaluate the HVDC interconnectionsmodels to be used in real-time voltage stability assessment is proposed.The existing models for the HVDC interconnections, thatare based on voltage source converter, were studied selecting theones that are suitable for its application in Thevenin...... equivalent ´methods for voltage stability assessment. The proposed methodis to evaluate the validity of the models by using synthetizedPMU measurements from simulations and from PMUs connectedto the danish system. Wide-area measurements are used toestimate the HVDC model parameters which are needed...

Some problems relating to the transmission of electrical power at very high voltage

Energy Technology Data Exchange (ETDEWEB)

Goldstein, A

1965-01-01

Some of the technical and economic factors which influence the choice of a transmission system, particularly a very high voltage one, are discussed. The stability of transmission overvoltages at mains frequency and their control by means of compensating reactances is described. Overvoltages due to circuit-breaker operation and those of atmospheric origin, and appropriate protective devices, the behaviour of equipment at 750 kV, and problems of testing are included. Finally, the 735 kV network now being installed to carry 5300 MW of hydroelectric power 650 km from the Manicouagan River to Quebec and Montreal is described.

Improvement of stability of sinusoidally driven atmospheric pressure plasma jet using auxiliary bias voltage

Directory of Open Access Journals (Sweden)

Hyun-Jin Kim

2015-12-01

Full Text Available In this study, we have proposed the auxiliary bias pulse scheme to improve the stability of atmospheric pressure plasma jets driven by an AC sinusoidal waveform excitation source. The stability of discharges can be significantly improved by the compensation of irregular variation in memory voltage due to the effect of auxiliary bias pulse. From the parametric study, such as the width, voltage, and onset time of auxiliary bias pulse, it has been demonstrated that the auxiliary bias pulse plays a significant role in suppressing the irregular discharges caused by the irregular variation in memory voltage and stable discharge can be initiated with the termination of the auxiliary bias pulse. As a result of further investigating the effects of the auxiliary pulse scheme on the jet stability under various process conditions such as the distance between the jet head and the counter electrode, and carrier gas flow, the jet stability can be improved by adjusting the amplitude and number of the bias pulse depending on the variations in the process conditions.

Dynamic voltage stability of a distribution system with high penetration of grid-connected photovoltaic type solar generators

Directory of Open Access Journals (Sweden)

Zetty Adibah Kamaruzzaman

2016-06-01

Full Text Available This paper presents the impact of grid-connected photovoltaic (PV generator on dynamic voltage stability of a power distribution system by considering solar intermittency, PV penetration level, and contingencies such as line outage and load increase. The IEEE 13 node test feeder is used as a test system, and a solar PV of 0.48 kV/0.5 MVA is integrated into the test system. Test results show that system voltage is stable at high PV penetration levels. Increase in load causes voltage instability, in which voltage drops below its allowable operating limit. Thus, increase in PV penetration level does not improve system voltage stability because the system experiences voltage collapse during line outage.

Enhanced Dynamic Voltage Stability Support by VSC-HVDC for Offshore Wind Applications using Trajectory Sensitivity Analysis

DEFF Research Database (Denmark)

Liu, Hongzhi; Chen, Zhe; Liu, Leo

2013-01-01

The integration of large-scale wind power plants changes the structure, configuration and operation of conventional power systems and brings challenges to the security and stability of power systems. Dynamic voltage stability of power systems with high wind penetration is one of the critical issues....... In this paper, VSC-HVDC transmission system is used to integrate a large-scale wind power plant into the onshore power grid. For different voltage support strategies of VSC-HVDC, a trajectory sensitivity analysisbased approach is proposed to find the minimum onshore VSC capacity with which the VSC-HVDC can...... provide enough support for the improvement of system voltage stability after a disturbance. Sensitivities of reactive power output of VSC to its capacity increase are calculated instead of the sensitivities of bus voltage magnitude towards the reactive power injection variation of VSC. Simulation results...

Transient Voltage Stability Analysis and Improvement of A Network with different HVDC Systems

DEFF Research Database (Denmark)

Liu, Yan; Chen, Zhe

2011-01-01

This paper presents transient voltage stability analysis of an AC system with multi-infeed HVDC links including a traditional LCC HVDC link and a VSC HVDC link. It is found that the voltage supporting capability of the VSC-HVDC link is significantly influenced by the tie-line distance between the...

Multi-Objective Differential Evolution for Voltage Security Constrained Optimal Power Flow in Deregulated Power Systems

Science.gov (United States)

Roselyn, J. Preetha; Devaraj, D.; Dash, Subhransu Sekhar

2013-11-01

Voltage stability is an important issue in the planning and operation of deregulated power systems. The voltage stability problems is a most challenging one for the system operators in deregulated power systems because of the intense use of transmission line capabilities and poor regulation in market environment. This article addresses the congestion management problem avoiding offline transmission capacity limits related to voltage stability by considering Voltage Security Constrained Optimal Power Flow (VSCOPF) problem in deregulated environment. This article presents the application of Multi Objective Differential Evolution (MODE) algorithm to solve the VSCOPF problem in new competitive power systems. The maximum of L-index of the load buses is taken as the indicator of voltage stability and is incorporated in the Optimal Power Flow (OPF) problem. The proposed method in hybrid power market which also gives solutions to voltage stability problems by considering the generation rescheduling cost and load shedding cost which relieves the congestion problem in deregulated environment. The buses for load shedding are selected based on the minimum eigen value of Jacobian with respect to the load shed. In the proposed approach, real power settings of generators in base case and contingency cases, generator bus voltage magnitudes, real and reactive power demands of selected load buses using sensitivity analysis are taken as the control variables and are represented as the combination of floating point numbers and integers. DE/randSF/1/bin strategy scheme of differential evolution with self-tuned parameter which employs binomial crossover and difference vector based mutation is used for the VSCOPF problem. A fuzzy based mechanism is employed to get the best compromise solution from the pareto front to aid the decision maker. The proposed VSCOPF planning model is implemented on IEEE 30-bus system, IEEE 57 bus practical system and IEEE 118 bus system. The pareto optimal

Voltage stability evaluation of the Paraguayan system; Evaluacion de la estabilidad de tension del sistema paraguayo

Energy Technology Data Exchange (ETDEWEB)

Cardozo Sanchez, Freddy [Mirant Americas (United States); Fernandez Krekeler, Ubaldo [Administracion Nacional de Electricidad (ANDE), Asuncion (Paraguay)

2001-07-01

This document presents analyses of permanent status of the ANDE transmission system, seeking to evaluate the voltage stability and impact that would have possible reinforcements in 500 kV. The transmission under this new voltage level, besides to be a reinforcement to the system for satisfying the national demand, will permit the increase of energy exportation to Brazil, depending on the adopted reinforcement. The system current status and its evolution according to the planning of short and medium period are analysed. In the voltage stability evolution, static analysis techniques to draw the Q-V and P-V curves were used, as well as for determination of the system self-values and stability margins.

A fuzzy genetic approach for network reconfiguration to enhance voltage stability in radial distribution systems

International Nuclear Information System (INIS)

Sahoo, N.C.; Prasad, K.

2006-01-01

This paper presents a fuzzy genetic approach for reconfiguration of radial distribution systems (RDS) so as to maximize the voltage stability of the network for a specific set of loads. The network reconfiguration involves a mechanism for selection of the best set of branches to be opened, one from each loop, such that the reconfigured RDS possesses desired performance characteristics. This discrete solution space is better handled by the proposed scheme, which maximizes a suitable optimizing function (computed using two different approaches). In the first approach, this function is chosen as the average of a voltage stability index of all the buses in the RDS, while in the second approach, the complete RDS is reduced to a two bus equivalent system and the optimizing function is the voltage stability index of this reduced two bus system. The fuzzy genetic algorithm uses a suitable coding and decoding scheme for maintaining the radial nature of the network at every stage of genetic evolution, and it also uses a fuzzy rule based mutation controller for efficient search of the solution space. This method, tested on 69 bus and 33 bus RDSs, shows promising results for the both approaches. It is also observed that the network losses are reduced when the voltage stability is enhanced by the network reconfiguration

The development of high-voltage repetitive low-jitter corona stabilized triggered switch

Science.gov (United States)

Geng, Jiuyuan; Yang, Jianhua; Cheng, Xinbing; Yang, Xiao; Chen, Rong

2018-04-01

The high-power switch plays an important part in a pulse power system. With the trend of pulse power technology toward modularization, miniaturization, and accuracy control, higher requirements on electrical trigger and jitter of the switch have been put forward. A high-power low-jitter corona-stabilized triggered switch (CSTS) is designed in this paper. This kind of CSTS is based on corona stabilized mechanism, and it can be used as a main switch of an intense electron-beam accelerator (IEBA). Its main feature was the use of an annular trigger electrode instead of a traditional needle-like trigger electrode, taking main and side trigger rings to fix the discharging channels and using SF6/N2 gas mixture as its operation gas. In this paper, the strength of the local field enhancement was changed by a trigger electrode protrusion length Dp. The differences of self-breakdown voltage and its stability, delay time jitter, trigger requirements, and operation range of the switch were compared. Then the effect of different SF6/N2 mixture ratio on switch performance was explored. The experimental results show that when the SF6 is 15% with the pressure of 0.2 MPa, the hold-off voltage of the switch is 551 kV, the operating range is 46.4%-93.5% of the self-breakdown voltage, the jitter is 0.57 ns, and the minimum trigger voltage requirement is 55.8% of the peak. At present, the CSTS has been successfully applied to an IEBA for long time operation.

A novel tarantula toxin stabilizes the deactivated voltage sensor of bacterial sodium channel.

Science.gov (United States)

Tang, Cheng; Zhou, Xi; Nguyen, Phuong Tran; Zhang, Yunxiao; Hu, Zhaotun; Zhang, Changxin; Yarov-Yarovoy, Vladimir; DeCaen, Paul G; Liang, Songping; Liu, Zhonghua

2017-07-01

Voltage-gated sodium channels (Na V s) are activated by transiting the voltage sensor from the deactivated to the activated state. The crystal structures of several bacterial Na V s have captured the voltage sensor module (VSM) in an activated state, but structure of the deactivated voltage sensor remains elusive. In this study, we sought to identify peptide toxins stabilizing the deactivated VSM of bacterial Na V s. We screened fractions from several venoms and characterized a cystine knot toxin called JZTx-27 from the venom of tarantula Chilobrachys jingzhao as a high-affinity antagonist of the prokaryotic Na V s Ns V Ba (nonselective voltage-gated Bacillus alcalophilus ) and NaChBac (bacterial sodium channel from Bacillus halodurans ) (IC 50 = 112 nM and 30 nM, respectively). JZTx-27 was more efficacious at weaker depolarizing voltages and significantly slowed the activation but accelerated the deactivation of Ns V Ba, whereas the local anesthetic drug lidocaine was shown to antagonize Ns V Ba without affecting channel gating. Mutation analysis confirmed that JZTx-27 bound to S3-4 linker of Ns V Ba, with F98 being the critical residue in determining toxin affinity. All electrophysiological data and in silico analysis suggested that JZTx-27 trapped VSM of Ns V Ba in one of the deactivated states. In mammalian Na V s, JZTx-27 preferably inhibited the inactivation of Na V 1.5 by targeting the fourth transmembrane domain. To our knowledge, this is the first report of peptide antagonist for prokaryotic Na V s. More important, we proposed that JZTx-27 stabilized the Ns V Ba VSM in the deactivated state and may be used as a probe to determine the structure of the deactivated VSM of Na V s.-Tang, C., Zhou, X., Nguyen, P. T., Zhang, Y., Hu, Z., Zhang, C., Yarov-Yarovoy, V., DeCaen, P. G., Liang, S., Liu, Z. A novel tarantula toxin stabilizes the deactivated voltage sensor of bacterial sodium channel. © FASEB.

Technical and economic aspects of the transmission of energy at extra high voltages

Energy Technology Data Exchange (ETDEWEB)

Kahnt, R

1967-01-01

The reasons for the employment of higher transmission voltages are listed and the points decisive for the selection of three phase ac or dc systems are reviewed. A treatment of the technical and economic problems arising in three phase extra high voltage transmission is presented. These include selection of voltage, economical design of power lines, insulation problems, power supply dependability, equipment rating and reactive power and stability problems.

Voltage stability analysis considering the load dynamic characteristics and the voltage control devices; Analisis de estabilidad de voltaje considerando las caracteristicas dinamicas de la carga y dispositivos de control de voltaje

Energy Technology Data Exchange (ETDEWEB)

Hernandez Alvarez, Enrique

2001-09-15

The research work presented in this thesis, is centered in the voltage stability analysis of medium term considering the effect of the load characteristics and its interaction with the voltage control device models in the transmission network. More concretely, a type of load model is defined and studied with desirable characteristics for the study of the voltage stability, the generic load models derived from field tests and from the application of identification techniques and it is analyzed the influence of the application of control systems to improve the system stability margins. Also, alternatives to the power system modeling for the voltage stability study in complex systems are reviewed. In the first place a fundamental analysis of the voltage characteristics and stability in a simplified power system is presented and the method of adopted analysis is introduced. It is shown that the instability phenomenon is manifested as a singular type bifurcation induced from the critical way of voltage when the system is operated under stress conditions. Next, the contribution of the action of the control devices to the stability margin is analyzed and criteria of the stability analyses are deducted based on the study of such mode. Following a linear model of the power system with desirable characteristics for the study of the voltage stability of medium term is proposed and the characteristics of stability in the context of the study of complex systems are interpreted. The proposed analysis tool is based on the physical notion that the behavior of the voltage control systems in the generators is very rapid with regard to the behavior of the load and has its main application in the preliminary study of the voltage stability of medium and long term. From this model, an analytical tool based on the application of techniques of linear analysis is proposed to approach the problem of determination of critical voltage areas and the contribution of control devices to the

A fuzzy genetic approach for network reconfiguration to enhance voltage stability in radial distribution systems

Energy Technology Data Exchange (ETDEWEB)

Sahoo, N.C. [Faculty of Engineering and Technology, Multimedia University, Jalan Ayer Keroh Lama, Bukit Beruang, 75450 Melaka (Malaysia); Prasad, K. [Faculty of Information Science and Technology, Multimedia University, Jalan Ayer Keroh Lama, Bukit Beruang, 75450 Melaka (Malaysia)

2006-11-15

This paper presents a fuzzy genetic approach for reconfiguration of radial distribution systems (RDS) so as to maximize the voltage stability of the network for a specific set of loads. The network reconfiguration involves a mechanism for selection of the best set of branches to be opened, one from each loop, such that the reconfigured RDS possesses desired performance characteristics. This discrete solution space is better handled by the proposed scheme, which maximizes a suitable optimizing function (computed using two different approaches). In the first approach, this function is chosen as the average of a voltage stability index of all the buses in the RDS, while in the second approach, the complete RDS is reduced to a two bus equivalent system and the optimizing function is the voltage stability index of this reduced two bus system. The fuzzy genetic algorithm uses a suitable coding and decoding scheme for maintaining the radial nature of the network at every stage of genetic evolution, and it also uses a fuzzy rule based mutation controller for efficient search of the solution space. This method, tested on 69 bus and 33 bus RDSs, shows promising results for the both approaches. It is also observed that the network losses are reduced when the voltage stability is enhanced by the network reconfiguration. (author)

Vibrations and Stability: Solved Problems

DEFF Research Database (Denmark)

Thomsen, Jon Juel

Worked out solutions for exercise problems in J. J. Thomsen 'Vibrations and Stability: Advanced Theory, Analysis, and Tools', Springer, Berlin - Heidelberg, 2003.......Worked out solutions for exercise problems in J. J. Thomsen 'Vibrations and Stability: Advanced Theory, Analysis, and Tools', Springer, Berlin - Heidelberg, 2003....

Enhancement of Voltage Stability of DC Smart Grid During Islanded Mode by Load Shedding Scheme

Science.gov (United States)

Nassor, Thabit Salim; Senjyu, Tomonobu; Yona, Atsushi

2015-10-01

This paper presents the voltage stability of a DC smart grid based on renewable energy resources during grid connected and isolated modes. During the islanded mode the load shedding, based on the state of charge of the battery and distribution line voltage, was proposed for voltage stability and reservation of critical load power. The analyzed power system comprises a wind turbine, a photovoltaic generator, storage battery as controllable load, DC loads, and power converters. A fuzzy logic control strategy was applied for power consumption control of controllable loads and the grid-connected dual active bridge series resonant converters. The proposed DC Smart Grid operation has been verified by simulation using MATLAB® and PLECS® Blockset. The obtained results show the effectiveness of the proposed method.

Active Power Filter DC Bus Voltage Piecewise Reaching Law Variable Structure Control

Directory of Open Access Journals (Sweden)

Baolian Liu

2014-01-01

Full Text Available The DC bus voltage stability control is one key technology to ensure that Active Power Filter (APF operates stably. The external disturbances such as power grid and load fluctuation and the system parameters changing may affect the stability of APF DC bus voltage and the normal operation of APF. The mathematical model of DC bus voltage is established according to power balance principle and a DC bus voltage piecewise reaching law variable structure control algorithm is proposed to solve the above problem, and the design method is given. The simulation and experiment results proved that the proposed variable structure control algorithm can eliminate the chattering problem existing in traditional variable structure control effectively, is insensitive to system disturbance, and has good robustness and fast dynamic response speed and stable DC bus voltage with small fluctuation. The above advantages ensure the compensation effect of APF.

Research of the voltage and current stabilization processes by using the silicon field-effect transistor

International Nuclear Information System (INIS)

Karimov, A.V.; Yodgorova, D.M.; Kamanov, B.M.; Giyasova, F.A.; Yakudov, A.A.

2012-01-01

The silicon field-effect transistors were investigated to use in circuits for stabilization of current and voltage. As in gallium arsenide field-effect transistors, in silicon field-effect transistors with p-n-junction a new mechanism of saturation of the drain current is experimentally found out due to both transverse and longitudinal compression of channel by additional resistance between the source and the gate of the transistor. The criteria for evaluating the coefficients of stabilization of transient current suppressors and voltage stabilizator based on the field-effect transistor are considered. (authors)

Hybrid AC-High Voltage DC Grid Stability and Controls

Science.gov (United States)

Yu, Jicheng

The growth of energy demands in recent years has been increasing faster than the expansion of transmission facility construction. This tendency cooperating with the continuous investing on the renewable energy resources drives the research, development, and construction of HVDC projects to create a more reliable, affordable, and environmentally friendly power grid. Constructing the hybrid AC-HVDC grid is a significant move in the development of the HVDC techniques; the form of dc system is evolving from the point-to-point stand-alone dc links to the embedded HVDC system and the multi-terminal HVDC (MTDC) system. The MTDC is a solution for the renewable energy interconnections, and the MTDC grids can improve the power system reliability, flexibility in economic dispatches, and converter/cable utilizing efficiencies. The dissertation reviews the HVDC technologies, discusses the stability issues regarding the ac and HVDC connections, proposes a novel power oscillation control strategy to improve system stability, and develops a nonlinear voltage droop control strategy for the MTDC grid. To verify the effectiveness the proposed power oscillation control strategy, a long distance paralleled AC-HVDC transmission test system is employed. Based on the PSCAD/EMTDC platform simulation results, the proposed power oscillation control strategy can improve the system dynamic performance and attenuate the power oscillations effectively. To validate the nonlinear voltage droop control strategy, three droop controls schemes are designed according to the proposed nonlinear voltage droop control design procedures. These control schemes are tested in a hybrid AC-MTDC system. The hybrid AC-MTDC system, which is first proposed in this dissertation, consists of two ac grids, two wind farms and a five-terminal HVDC grid connecting them. Simulation studies are performed in the PSCAD/EMTDC platform. According to the simulation results, all the three design schemes have their unique salient

Tools for voltage stability analysis, including a probabilistic approach

Energy Technology Data Exchange (ETDEWEB)

Vieira Filho, X; Martins, N; Bianco, A; Pinto, H J.C.P. [Centro de Pesquisas de Energia Eletrica (CEPEL), Rio de Janeiro, RJ (Brazil); Pereira, M V.F. [Power System Research (PSR), Inc., Rio de Janeiro, RJ (Brazil); Gomes, P; Santos, M.G. dos [ELETROBRAS, Rio de Janeiro, RJ (Brazil)

1994-12-31

This paper reviews some voltage stability analysis tools that are being used or envisioned for expansion and operational planning studies in the Brazilian system, as well as, their applications. The paper also shows that deterministic tools can be linked together in a probabilistic framework, so as to provide complementary help to the analyst in choosing the most adequate operation strategies, or the best planning solutions for a given system. (author) 43 refs., 8 figs., 8 tabs.

Use of the Wire Cylindrical Device as Voltage Stabilizer and Regulator for Practical Purpose

International Nuclear Information System (INIS)

Abd EI-Maksoud, T.M.

2008-01-01

The present work, is intended to investigate the use of the Wire Cylindrical Corona device (WCCD) at atmospheric pressure as voltage stabilizer and regulator. In particular, it is devoted to the investigation of the dependence of the stabilization and the regulation on both cathode cylinder radius R and the limiting resistance R

An improved direct feedback linearization technique for transient stability enhancement and voltage regulation of power generators

Energy Technology Data Exchange (ETDEWEB)

Kenne, Godpromesse [Laboratoire d' Automatique et d' Informatique Appliquee (LAIA), Departement de Genie Electrique, Universite de Dschang, B.P. 134 Bandjoun, Cameroun; Goma, Raphael; Lamnabhi-Lagarrigue, Francoise [Laboratoire des Signaux et Systemes (L2S), CNRS-SUPELEC, Universite Paris XI, 3 Rue Joliot Curie, 91192 Gif-sur-Yvette (France); Nkwawo, Homere [Departement GEII, Universite Paris XIII, IUT Villetaneuse, 99 Avenue Jean Baptiste Clement, 93430 Villetaneuse (France); Arzande, Amir; Vannier, Jean Claude [Departement Energie, Ecole Superieure d' Electricite-SUPELEC, 3 Rue Joliot Curie, 91192 Gif-sur-Yvette (France)

2010-09-15

In this paper, a simple improved direct feedback linearization design method for transient stability and voltage regulation of power systems is discussed. Starting with the classical direct feedback linearization technique currently applied to power systems, an adaptive nonlinear excitation control of synchronous generators is proposed, which is new and effective for engineering. The power angle and mechanical power input are not assumed to be available. The proposed method is based on a standard third-order model of a synchronous generator which requires only information about the physical available measurements of angular speed, active electric power and generator terminal voltage. Experimental results of a practical power system show that fast response, robustness, damping, steady-state and transient stability as well as voltage regulation are all achieved satisfactorily. (author)

Stability problems for linear hyperbolic systems

International Nuclear Information System (INIS)

Eckhoff, K.S.

1975-05-01

The stability properties for the trivial solution of a general linear hyperbolic system of partial differential equations of the first order are studied. It is shown that results may be obtained by studying the stability properties of certain systems of ordinary differential equations which can be constructed from the hyperbolic system (the so-called transport equations). In some cases the associated stability problem for the transport equations can in fact be shown to be equivalent to the stability problem for the hyperbolic system, but in general the transport equations will only give the necessary conditions for stability. (Auth.)

Searching for Plausible N-k Contingencies Endangering Voltage Stability

DEFF Research Database (Denmark)

Weckesser, Johannes Tilman Gabriel; Van Cutsem, Thierry

2017-01-01

This paper presents a novel search algorithm using time-domain simulations to identify plausible N − k contingencies endangering voltage stability. Starting from an initial list of disturbances, progressively more severe contingencies are investigated. After simulation of a N − k contingency......, the simulation results are assessed. If the system response is unstable, a plausible harmful contingency sequence has been found. Otherwise, components affected by the contingencies are considered as candidate next event leading to N − (k + 1) contingencies. This implicitly takes into account hidden failures...

The Amalgamation of SVR and ANFIS Models with Synchronized Phasor Measurements for On-Line Voltage Stability Assessment

Directory of Open Access Journals (Sweden)

Mohammed Amroune

2017-10-01

Full Text Available This paper presents the application of support vector regression (SVR and adaptive neuro-fuzzy inference system (ANFIS models that are amalgamated with synchronized phasor measurements for on-line voltage stability assessment. As the performance of SVR model extremely depends on the good selection of its parameters, the recently developed ant lion optimizer (ALO is adapted to seek for the SVR’s optimal parameters. In particular, the input vector of ALO-SVR and ANFIS soft computing models is provided in the form of voltage magnitudes provided by the phasor measurement units (PMUs. In order to investigate the effectiveness of ALO-SVR and ANFIS models towards performing the on-line voltage stability assessment, in-depth analyses on the results have been carried out on the IEEE 30-bus and IEEE 118-bus test systems considering different topologies and operating conditions. Two statistical performance criteria of root mean square error (RMSE and correlation coefficient (R were considered as metrics to further assess both of the modeling performances in contrast with the power flow equations. The results have demonstrated that the ALO-SVR model is able to predict the voltage stability margin with greater accuracy compared to the ANFIS model.

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

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...... 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........ 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...

Exploration of a radiation hardening stabilized voltage power supply

International Nuclear Information System (INIS)

Xie Zeyuan; Xu Xianguo

2014-01-01

This paper mainly introduces the design method of radiation hardening stabilized voltage power supply that makes use of commercial radiation resistant electronic devices and the test results of radiation performance of the power supply and devices are presented in detail. The experiment results show that the hardened power supply can normally work until 1000 Gy (Si) total dose and 1 × 10 14 n/cm 2 neutron radiation, and it doesn't latchup at about 1 × l0 9 Gy (Si)/s gamma transient dose rate. (authors)

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

Stability and voltage rise at operating frequency in ehv networks at 500 to 700 kV

Energy Technology Data Exchange (ETDEWEB)

Glavitsch, H

1964-01-01

The importance of stability is stressed in the case of long transmission lines interconnecting different systems. To achieve better stability one requires improvement of network stability and generator stability. The methods of excitation and electric braking for improving the dynamic stability of generators are described. The stability of two networks connected by a line is examined theoretically. The various causes of voltage rises at operating frequency, e.g., loading, load dropping etc., and the usual types of transients are discussed.

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.

Diagnostic method for measuring plasma-induced voltages on the PBX-M [Princeton Beta Experiment-Modified] stabilizing shell

International Nuclear Information System (INIS)

Kugel, H.W.; Okabayashi, M.; Schweitzer, S.

1990-07-01

The Princeton Beta Experiment-Modified (PBX-M) has a close-fitting conducting, passive plate, stabilizing shell which nearly surrounds highly indented, bean-shaped plasmas. The proximity of this electrically isolated shell to a large fraction of the plasma surface allows measurements similar to previous work on other tokamaks using floating probes and limiters. Measurements were performed to characterize the plasma-induced voltages on the PBX-M passive plate stabilizing shell during high-β plasmas. Voltage differences were measured between the respective passive plate toroidal and poloidal gaps, the respective passive plates and the vessel, and an outer poloidal graphite limiter and its passive plate. The calibration and qualification testing procedures are discussed. The initial measurements found that the largest voltages were observed at plasma start-up and at the plasma current disruption and exhibited characteristics depending on operating conditions. The highest voltages observed have been at disruption and were less than 2 kV. 9 refs., 5 figs

Influence of Wind Plant Ancillary Voltage Control on System Small Signal Stability

DEFF Research Database (Denmark)

Su, Chi; Chen, Zhe

2012-01-01

As a common tendency, large-scale wind farms are increasingly connected to the transmission system of modern power grids. This introduces some new challenges to the connected power systems, and the transmission system operators (TSOs) have to put some new requirements as part of the grid codes...... on the integration of wind farms. One common requirement to wind farms is the function of system voltage control which can be implemented in the grid-side convertor controller of a variable speed wind turbine. This ancillary voltage control provided by wind farms could have some influence on the system small signal...... stability. This paper implements an ancillary voltage control strategy on a direct-drive-full-convertor-based wind farm and studies its influence on the damping ratio values of the dominant oscillation mode within the connected power system. All the calculations and simulations are conducted in DIg...

Emotional stability components of human performance problems

International Nuclear Information System (INIS)

Wexler, R.H.

1987-01-01

Over half of all significant events that occur in nuclear plants involve human performance problems. There is increasing worldwide recognition that human performance problems have a significant impact on the safety, cost, and efficiency of nuclear plant operations. Emotional stability components have an important direct and indirect impact on human performance problems. This paper examines emotional stability components that are currently incorporated into human performance evaluation systems (HPES) in nuclear plants. It describes HPES programs being developed around the world, the emotional stability components that are currently referred to in these programs, and suggestions for improving HPES programs through a greater understanding of emotion stability components. A review of emotional stability components that may hinder or promote a plant environment that encourages the voluntary reporting and correction of human error is also presented

The influence of the representation loads in the voltage stability; Influencia de la representacion de las cargas en la estabilidad de voltaje

Energy Technology Data Exchange (ETDEWEB)

Morales Gonzalez, Eduardo

2005-12-15

Environmental and economic reasons have been the main factors for limiting the growing of transmission power grids in many countries. In addition, the electric industry trend to de-regulation of electricity markets has forced to operate the transmission grids closer to their normal limits for secure operation. Since most of the time modern power networks operate under stressed conditions, voltage collapse has become a big concern in the daily operation of the systems. Thus, determination of reliable operating limits respect to voltage collapse is of utmost importance to guarantee an economical and secure system operation. With the aim of understanding the mechanisms of voltage stability and voltage collapse, a number of studying approaches have been proposed for the analysis of such problems. A common feature of those approaches is the importance of reliable models for representing load characteristics. As a result of this, the development of adequate mathematical models for reliable load representation has received a great deal of attention. Despite those efforts, load modeling remains as a big challenge in the analysis of power systems voltage stability. In this thesis, the influence of load modeling on voltage stability is addressed using a steady-state analysis approach. The voltage stability analysis of the system is performed from the P-V curves for different load representations and voltage sensitivity indices. Finally, numerical results from two test systems are reported and the close relationship between load modeling and voltage stability limits in a power system is highlighted. [Spanish] Las razones economicas y ambientales han sido los principales factores para limitar el crecimiento de los sistemas de transmision en muchos paises. Ademas, la tendencia a la desregulacion en la industria electrica ha forzado a operar las redes electricas mas cerca de sus limites de operacion. Debido a que la mayoria de los sistemas electricos modernos operan bajo

Mitigation of Voltage Sags in CIGRE Low Voltage Distribution Network

DEFF Research Database (Denmark)

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

2013-01-01

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 p....... 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...... 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...

Modelling, stability and control of voltage behaviour in power supply systems

Energy Technology Data Exchange (ETDEWEB)

Hill, David J [Sydney Univ., NSW (Australia). Dept. of Electrical Engineering; Hisken, Ian A [Newcastle Univ., NSW (Australia). Dept. of Electrical and Computer Engineering

1994-12-31

This paper gives an overview of a line of work on mid to long term voltages stability analysis and control in power systems. The results are based on use of a novel approach to dynamic load modelling using aggregate nonlinear structures. In general, the model for the transmission network and supply end dynamics is of the hybrid differential - algebraic - discrete kind. Various stability questions are precisely formulated and analysed in terms of network and load characteristics (steady-state and transient). The results are shown to be a useful framework for deriving criteria of the where, when and how much kind for various control actions such as load Thedding and tap-blocking. (author) 47 refs., 15 figs., 1 tab.

A new emergency control for voltage stability utilizing the time overvoltage capability of large shunt capacitor banks

Energy Technology Data Exchange (ETDEWEB)

Taylor, Carson W; Vanleuven, Allen L; Nordstrom, Jerry M [Bonneville Power Administration, Portland, OR (United States)

1994-12-31

Electric utilities have become increasing concerned with the possibility of voltage instability and voltage collapse. Although many countermeasures are a possible, control based countermeasures are often the most cost effective. Voltage collapse is often only a threat during unusual conditions such as very high load and major outages. For these low probability conditions, low cost emergency controls may be the only cost effective countermeasures. This paper provides details on a prototype installation by the Bonneville Power Administration of a new low cost emergency control for voltage stability named CAPS (CAPacitor bank series group Shorting). (author) 6 refs., 5 figs.

Plug-and-Play Voltage/Current Stabilization DC Microgrid Clusters with Grid-Forming/Feeding Converters

DEFF Research Database (Denmark)

Han, Renke; Tucci, Michele; Martinelli, Andrea

2018-01-01

In this paper, we propose a new decentralized control scheme for Microgrid (MG) clusters, given by the interconnection of atomic dc MGs, each composed by grid-forming and grid-feeding converters. In particular, we develop a new Plug-and-Play (PnP) voltage/current controller for each MG in order...... to achieve simultaneous voltage support and current feeding function with local references. The coefficients of each stabilizing controller are characterized by explicit inequalities, which are related only to local electrical parameters of the MG. With the proposed controller, each MG can plug...

Suitability of voltage stability study methods for real-time assessment

DEFF Research Database (Denmark)

Perez, Angel; Jóhannsson, Hjörtur; Vancraeyveld, Pieter

2013-01-01

This paper analyzes the suitability of existing methods for long-term voltage stability assessment for real-time operation. An overview of the relevant methods is followed with a comparison that takes into account the accuracy, computational efficiency and characteristics when used for security...... assessment. The results enable an evaluation of the run time of each method with respect to the number of inputs. Furthermore, the results assist in identifying which of the methods is most suitable for realtime operation in future power system with production based on fluctuating energy sources....

Interconnection and transportation networks: adjustments and stability; Reseaux d'interconnexion et de transport: reglages et stabilite

Energy Technology Data Exchange (ETDEWEB)

Bornard, P. [Reseau de Transport d' Electricite (RTE), Div. Systeme Electrique, 92 - Paris la Defense (France); Pavard, M. [Electricite de France (EDF), 75 - Paris (France); Testud, G. [Reseau de Transport d' Electricite (RTE), Dept. Exploitation du Systeme Electrique, 92 - Paris la Defense (France)

2005-10-01

Keeping the mastery of the safety of a power transportation system and respecting the contractual commitments with respect to the network users implies the implementation of efficient frequency and voltage adjustment systems. This article presents a synthetic overview of the methods and means implemented to ensure the adjustment of the voltage and frequency and the stability of very-high voltage power transportation networks: 1 - recalls of the general problem; 2 - frequency and active power adjustment: adapting generation to consumption, adapting consumption to generation; 3 - voltage and reactive power adjustment: duality of the voltage-reactive compensation adjustment, compensation of the reactive power, voltage adjustment chain, voltage adjustment of very high voltage networks, collapse of the voltage plan; 4 - alternators stability: static stability, transient stability, numerical simulation methods, stability improvement; 5 - conclusion. (J.S.)

Regulation of the Output Voltage of an Inverter in Case of Load Variation

Science.gov (United States)

Diouri, Omar; Errahimi, Fatima; Es-Sbai, Najia

2018-05-01

In a DC/AC photovoltaic application, the stability of the output voltage of the inverter plays a very important role in the electrical systems. Such a photovoltaic system is constituted by an inverter, which makes it possible to convert the continuous energy to the alternative energy used in systems which operate under a voltage of 230V. The output of this inverter can be connected to a single load or more, at which time a second load is added in parallel with the first load. In this case, it proves a voltage drop at the output of the inverter. This problem influences the proper functioning of the electrical loads. Therefore, our contribution is to give a solution to this by compensating this voltage drop using a boost converter at the input of the inverter. This boost converter will play the role of the compensator that will provide the necessary voltage to the inverter in order to increase the voltage across the loads. But the use of this boost without controlling it is not enough because it generates a voltage that depends on the duty cycle of the control signal. To stabilize the output voltage of the inverter, we used a Proportional, Integral, and Derivative control (PID), which makes it possible to generate the necessary control signal for the voltage boost in order to have a good regulation of the output voltage of the inverter. Finally, we have solved the problem of the voltage drop even though there is loads variation.

Stability identification for grid-connected inverters with LCL filters considering grid-voltage feedforward regulator

DEFF Research Database (Denmark)

Lu, Minghui; Blaabjerg, Frede

2017-01-01

This paper identifies stable resonance frequency range for grid-connected inverter with Grid-Voltage Feedforward Regulator (GVFR). Beginning with the current loop stability analysis without GVFR, system poles distribution is analytically studied in z-domain, the critical frequency is therefore...... calculated as well as the control gain limit. Then, this paper reveals the GVFR would change the system stability in the weak power system, two frequency boundaries and three typical resonance frequency ranges are identified and compared. System poles distribution shows that GVFR can offer damping effects...

On the specification of bus voltages and radial link transfer impedance modes

Energy Technology Data Exchange (ETDEWEB)

El-Sadik, F.M. [Khartoum Univ., Aljamaa, Khartoum (Sudan)

2010-07-01

No algebraic equation has been derived for the steady-state stability limit (SSSL) of radial power system components in terms of their resistive sectional impedance elements and associated scalar node voltage constraints. While many criterion have been developed in the literature for the steady state angle and voltage stability limits of systems with losses, speculation exists about certain advocated metrics for these systems in terms of stability reserve margins as a measure of the risk of blackout and the representation of reactance modes associated with Putman's model for synchronous machines. This paper presented the results of a generalized algebraic statement for the reactance modes under stability conditions in voltage-specified power system components cited in the single machine-infinite bus (SMIB) and the radial power link (RPL) systems. The direct analytical solution to the problem enabled the identification of 2 different constraint relations for the sending (E) and receiving-end voltage regulator (VR) voltages. The paper discussed the general SSSL function plan, conditions for SMIB system reactances, and index results for the voltage stability of radial lines. The results for the R2 influence and influence on radial compensation levels were also presented. Index results for non-operational reactance zones were provided. It was concluded that the algebraic solution in a full representation of system losses would enable identification of additional function discontinuities that might not reveal in a step-by-step numerical algorithm and that may account for the many unresolved transmission system phenomenon associated with SSSL predictions and capacitance compensation schemes. 11 refs., 1 tab., 5 figs., 3 appendices.

POWER STABILITY MONITORING BASED ON VOLTAGE INSTABILITY PREDICTION APPROACH THROUGH WIDE AREA SYSTEM

OpenAIRE

H. H. Goh; Q. S. Chua; S. W. Lee; B. C. Kok; K. C. Goh; K. T.K. Teo

2014-01-01

Nowadays, power systems are being forced to operate closer to its security limit due to current economic growth and the difficulties to upgrade the existing grid infrastructure. With the sudden increment of power demand, voltage instability problem has become a main concern to the power system operator because voltage instability has led or crucially contributed to some major blackouts throughout the world. Hence, methods for early warning and early prevention are required to prevent the powe...

Constant potential high-voltage generator

International Nuclear Information System (INIS)

Resnick, T.A.; Dupuis, W.A.; Palermo, T.

1980-01-01

An X-ray tube voltage generator with automatic stabilization circuitry is disclosed. The generator includes a source of pulsating direct current voltage such as from a rectified 3 phase transformer. This pulsating voltage is supplied to the cathode and anode of an X-ray tube and forms an accelerating potential for electrons within that tube. The accelerating potential is stabilized with a feedback signal which is provided by a feedback network. The network includes an error signal generator which compares an instantaneous accelerating potential with a preferred reference accelerating potential and generates an error function. This error function is transmitted to a control tube grid which in turn causes the voltage difference between X-ray tube cathode and anode to stabilize and thereby reduce the error function. In this way stabilized accelerating potentials are realized and uniform X-ray energy distributions produced. (Auth.)

Implementation of Particle Swarm Optimization Method for Voltage Stability Analysis in 150 kV Sub System Grati – Paiton East Java

Science.gov (United States)

Kusumaningtyas, A. B.; Hidayat, M. N.; Ronilaya, F.

2018-04-01

Based on the data from State Electric Company on 15 January 2013, the undistributed power in the 150 kV sub system Grati-Paiton Region IV, that consist of 26 bus 150 kV and 2 bus generation 500 kV system, was recorded 3.286,00 MW. At the same time, the frequency of the system was down to 49 Hz. This lead to a deficit generation and unstable voltage condition in the system. Fast Voltage Stability Index (FVSI) method is used in this research to analyze the voltage stability of the buses. For buses with unstable voltage condition, reactive power will be injected through capacitor installation. The site where the capacitor will be installed is determined using the Fast Voltage Stability Index (FVSI) method while the size of the capacitor is determined using the Particle Swarm Optimization (PSO) method. The PSO method has been applied in some researches, such as to determine optimal placement and sizing in radial distribution network as well as in transmission network.. In this research, the PSO method is used to find the Qloss of an interconnection transmission system, which in turn, the value of the Qloss is used to determine the capacitance of the capacitor needed by the system.

Simultaneous Stabilization of Gyrotron Frequency and Power by PID Double Feedback Control on the Acceleration and Anode Voltages

Science.gov (United States)

Khutoryan, E. M.; Idehara, T.; Kuleshov, A. N.; Tatematsu, Y.; Yamaguchi, Y.; Matsuki, Y.; Fujiwara, T.

2017-07-01

In this paper, we present the results of simultaneous stabilization of both the frequency and the output power by a double PID feedback control on the acceleration and anode voltages in the 460-GHz gyrotron FU CW GVI, also known as "Gyrotron FU CW GO-1" (according to the nomenclature adopted at Osaka University). The approach used in the experiments is based on the modulation of the cyclotron frequency and the pitch factor (velocity ratio) of the electron beam by varying the acceleration and the anode voltages, respectively. In a long-term experiment, the frequency and power stabilities were made to be better than ±10-6 and ±1%, respectively.

Unbalanced voltage control of virtual synchronous generator in isolated micro-grid

Science.gov (United States)

Cao, Y. Z.; Wang, H. N.; Chen, B.

2017-06-01

Virtual synchronous generator (VSG) control is recommended to stabilize the voltage and frequency in isolated micro-grid. However, common VSG control is challenged by widely used unbalance loads, and the linked unbalance voltage problem worsens the power quality of the micro-grid. In this paper, the mathematical model of VSG was presented. Based on the analysis of positive- and negative-sequence equivalent circuit of VSG, an approach was proposed to eliminate the negative-sequence voltage of VSG with unbalance loads. Delay cancellation method and PI controller were utilized to identify and suppress the negative-sequence voltages. Simulation results verify the feasibility of proposed control strategy.

Locational Pricing to Mitigate Voltage Problems Caused by High PV Penetration

Directory of Open Access Journals (Sweden)

Sam Weckx

2015-05-01

Full Text Available In this paper, a locational marginal pricing algorithm is proposed to control the voltage in unbalanced distribution grids. The increasing amount of photovoltaic (PV generation installed in the grid may cause the voltage to rise to unacceptable levels during periods of low consumption. With locational prices, the distribution system operator can steer the reactive power consumption and active power curtailment of PV panels to guarantee a safe network operation. Flexible loads also respond to these prices. A distributed gradient algorithm automatically defines the locational prices that avoid voltage problems. Using these locational prices results in a minimum cost for the distribution operator to control the voltage. Locational prices can differ between the three phases in unbalanced grids. This is caused by a higher consumption or production in one of the phases compared to the other phases and provides the opportunity for arbitrage, where power is transferred from a phase with a low price to a phase with a high price. The effect of arbitrage is analyzed. The proposed algorithm is applied to an existing three-phase four-wire radial grid. Several simulations with realistic data are performed.

Harmonic voltage excess problem test and analysis in UHV and EHV grid particular operation mode

Science.gov (United States)

Lv, Zhenhua; Shi, Mingming; Fei, Juntao

2018-02-01

The test and analysis of the power quality of some 1000kV UHV transmission lines and 500kV EHV transmission lines is carried out. It is found that there is harmonic voltage excess problems when the power supply of the UHV and EHV voltage line is single-ended or single-loop, the problem basically disappeared after the operation mode change, different operating conditions, the harmonic current has not been greatly affected, indicating that the harmonic voltage changes mainly caused by the system harmonic impedance. With the analysis of MATLAB Simulink system model, it can be seen that there are specific harmonic voltage excess in the system under the specific operating mode, which results in serious distortion of the specific harmonic voltage. Since such phenomena are found in 500kV and 1000kV systems, it is suggested that the test evaluation work should be done under the typical mode of operation in 500kV, 1000kV Planning and construction process to prevent the occurrence of serious distortion and the regional harmonic current monitoring and suppression work should be done.

Long term stability of power systems

Energy Technology Data Exchange (ETDEWEB)

Kundur, P; Gao, B [Powertech Labs. Inc., Surrey, BC (Canada)

1994-12-31

Power system long term stability is still a developing subject. In this paper we provide our perspectives and experiences related to long term stability. The paper begins with the description of the nature of the long term stability problem, followed by the discussion of issues related to the modeling and solution techniques of tools for long term stability analysis. Cases studies are presented to illustrate the voltage stability aspect and plant dynamics aspect of long term stability. (author) 20 refs., 11 figs.

Stabilizing inverse problems by internal data

International Nuclear Information System (INIS)

Kuchment, Peter; Steinhauer, Dustin

2012-01-01

Several newly developing hybrid imaging methods (e.g., those combining electrical impedance or optical imaging with acoustics) enable one to obtain some auxiliary interior information (usually some combination of the electrical conductivity and the current) about the parameters of the tissues. This information, in turn, happens to stabilize the exponentially unstable and thus low-resolution optical and electrical impedance tomography. Various known instances of this effect have been studied individually. We show that there is a simple general technique (covering all known cases) that shows what kinds of interior data stabilize the reconstruction, and why. Namely, we show when the linearized problem becomes an elliptic pseudo-differential one, and thus stable. Stability here is meant as the problem being Fredholm, so the local uniqueness is not shown and probably does not hold in such generality. (paper)

Stabilizing inverse problems by internal data

KAUST Repository

Kuchment, Peter

2012-07-30

Several newly developing hybrid imaging methods (e.g., those combining electrical impedance or optical imaging with acoustics) enable one to obtain some auxiliary interior information (usually some combination of the electrical conductivity and the current) about the parameters of the tissues. This information, in turn, happens to stabilize the exponentially unstable and thus low-resolution optical and electrical impedance tomography. Various known instances of this effect have been studied individually. We show that there is a simple general technique (covering all known cases) that shows what kinds of interior data stabilize the reconstruction, and why. Namely, we show when the linearized problem becomes an elliptic pseudo-differential one, and thus stable. Stability here is meant as the problem being Fredholm, so the local uniqueness is not shown and probably does not hold in such generality. © 2012 IOP Publishing Ltd.

Flexible low-voltage organic transistors with high thermal stability at 250 °C.

Science.gov (United States)

Yokota, Tomoyuki; Kuribara, Kazunori; Tokuhara, Takeyoshi; Zschieschang, Ute; Klauk, Hagen; Takimiya, Kazuo; Sadamitsu, Yuji; Hamada, Masahiro; Sekitani, Tsuyoshi; Someya, Takao

2013-07-19

Low-operating-voltage flexible organic thin-film transistors with high thermal stability using DPh-DNTT and SAM gate dielectrics are reported. The mobility of the transistors are decreased by 23% after heating to 250 °C for 30 min. Furthermore, flexible organic pseudo-CMOS inverter circuits, which are functional after heating to 200 °C, are demonstrated. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Long Lifetime DC-Link Voltage Stabilization Module for Smart Grid Application

DEFF Research Database (Denmark)

Wang, Huai; Chung, Henry; Liu, Wenchao

2012-01-01

Power converters enable efficient and flexible control and conversion of electric energy among different smart grid players (i.e. producers, energy storage systems, and loads). One of the expected features of smart grid is that it will be more reliable compared to conventional grid. However, power...... converters are one kind of the lifetime limiting components applied in smart grid. One of the major causes is the malfunction of electrolytic capacitors (E-Caps) which are widely used for stabilizing the dc-link voltage in various types of power converters applied in smart grid. A dc-link module is therefore...

A Novel Index for Online Voltage Stability Assessment Based on Correlation Characteristic of Voltage Profiles

Directory of Open Access Journals (Sweden)

M. R. Aghamohammadi

2011-06-01

Full Text Available Abstract: Voltage instability is a major threat for security of power systems. Preserving voltage security margin at a certain limit is a vital requirement for today’s power systems. Assessment of voltage security margin is a challenging task demanding sophisticated indices. In this paper, for the purpose of on line voltage security assessment a new index based on the correlation characteristic of network voltage profile is proposed. Voltage profile comprising all bus voltages contains the effect of network structure, load-generation patterns and reactive power compensation on the system behaviour and voltage security margin. Therefore, the proposed index is capable to clearly reveal the effect of system characteristics and events on the voltage security margin. The most attractive feature for this index is its fast and easy calculation from synchronously measured voltage profile without any need to system modelling and simulation and without any dependency on network size. At any instant of system operation by merely measuring network voltage profile and no further simulation calculation this index could be evaluated with respect to a specific reference profile. The results show that the behaviour of this index with respect to the change in system security is independent of the selected reference profile. The simplicity and easy calculation make this index very suitable for on line application. The proposed approach has been demonstrated on IEEE 39 bus test system with promising results showing its effectiveness and applicability.

Power Quality Problems Mitigation using Dynamic Voltage Restorer in Egypt Thermal Research Reactor (ETRR-2)

International Nuclear Information System (INIS)

Kandil, T.; Ayad, N.M.; Abdel Haleam, A.; Mahmoud, M.

2013-01-01

Egypt thermal research reactor (ETRR-2) was subjected to several Power Quality Problems such as voltage sags/swells, harmonics distortion, and short interruption. ETRR-2 encompasses a wide range of loads which are very sensitive to voltage variations and this leads to several unplanned shutdowns of the reactor due to trigger of the Reactor Protection System (RPS). The Dynamic Voltage Restorer (DVR) has recently been introduced to protect sensitive loads from voltage sags and other voltage disturbances. It is considered as one of the most efficient and effective solution. Its appeal includes smaller size and fast dynamic response to the disturbance. This paper describes a proposal of a DVR to improve power quality in ETRR-2 electrical distribution systems . The control of the compensation voltage is based on d-q-o algorithm. Simulation is carried out by Matlab/Simulink to verify the performance of the proposed method

Improved Thévenin equivalent methods for real-time voltage stability assessment

DEFF Research Database (Denmark)

Perez, Angel; Jóhannsson, Hjörtur; Østergaard, Jacob

2016-01-01

An improved Thévenin equivalent method for real-time voltage stability assessment that uses wide-area information from synchrophasors is proposed. The improvements are a better modeling of the limited synchronous generators, and a processing that anticipates the effect of field current limiters......, before the latter are activated. Several study cases using detailed dynamic simulations of the Nordic test system have been used to assess the performance of the proposed improvements. Their effectiveness is analyzed and, based on the results, their possible application in combination...

Controlling Voltage Levels of Distribution Network-Radial Feeder after Connecting Wind Turbines to the Network

Directory of Open Access Journals (Sweden)

Muhammad Al Badri

2017-11-01

Full Text Available Several factors in power generation and supply need to be taken into account such as shortages of energy supply, system stability, and energy quality and system disruption due to network losses, industrial development and population expansion. The addition of wind turbines to the distribution network is of great benefit in providing additional power and solving these problems, but this addition is accompanied by the problem of low voltage network. This research found optimal solutions to the problem of low voltage distribution network after connecting wind turbines. The main idea of this paper is to optimize the low-voltage problem as a result of connecting the wind turbines to the "far end" of the radial feeder for a distribution network and to obtain a voltage level within an acceptable and stable range. The problem of low voltage solved by using the load-drop compensation, capacitor-bank and “doubly-fed” induction generators. The results of this study were based on the operation of the entire design of the simulation system which would be compatible with the reality of the energy flow of all network components by using the PSCAD program. The present analysis program revealed an optimum solution for the low voltage profile of the distribution network after connecting the wind turbine.

Stability Analysis of a Matrix Converter Drive: Effects of Input Filter Type and the Voltage Fed to the Modulation Algorithm

Directory of Open Access Journals (Sweden)

M. Hosseini Abardeh

2015-03-01

Full Text Available The matrix converter instability can cause a substantial distortion in the input currents and voltages which leads to the malfunction of the converter. This paper deals with the effects of input filter type, grid inductance, voltage fed to the modulation algorithm and the synchronous rotating digital filter time constant on the stability and performance of the matrix converter. The studies are carried out using eigenvalues of the linearized system and simulations. Two most common schemes for the input filter (LC and RLC are analyzed. It is shown that by a proper choice of voltage input to the modulation algorithm, structure of the input filter and its parameters, the need for the digital filter for ensuring the stability can be resolved. Moreover, a detailed model of the system considering the switching effects is simulated and the results are used to validate the analytical outcomes. The agreement between simulation and analytical results implies that the system performance is not deteriorated by neglecting the nonlinear switching behavior of the converter. Hence, the eigenvalue analysis of the linearized system can be a proper indicator of the system stability.

Real-time transient stabilization and voltage regulation of power generators with unknown mechanical power input

International Nuclear Information System (INIS)

Kenne, Godpromesse; Goma, Raphael; Nkwawo, Homere; Lamnabhi-Lagarrigue, Francoise; Arzande, Amir; Vannier, Jean Claude

2010-01-01

A nonlinear adaptive excitation controller is proposed to enhance the transient stability and voltage regulation of synchronous generators with unknown power angle and mechanical power input. The proposed method is based on a standard third-order model of a synchronous generator which requires only information about the physical available measurements of relative angular speed, active electric power, infinite bus and generator terminal voltages. The operating conditions are computed online using the above physical available measurements, the terminal voltage reference value and the estimate of the mechanical power input. The proposed design is therefore capable of providing satisfactory voltage in the presence of unknown variations of the power system operating conditions. Using the concept of sliding mode equivalent control techniques, a robust decentralized adaptive controller which insures the exponential convergence of the outputs to the desired ones, is obtained. Real-time experimental results are reported, comparing the performance of the proposed adaptive nonlinear control scheme to one of the conventional AVR/PSS controller. The high simplicity of the overall adaptive control scheme and its robustness with respect to line impedance variation including critical unbalanced operating condition and temporary turbine fault, constitute the main positive features of the proposed approach.

Real-time transient stabilization and voltage regulation of power generators with unknown mechanical power input

Energy Technology Data Exchange (ETDEWEB)

Kenne, Godpromesse, E-mail: gokenne@yahoo.co [Laboratoire d' Automatique et d' Informatique Appliquee (LAIA), Departement de Genie Electrique, Universite de Dschang, B.P. 134 Bandjoun (Cameroon); Goma, Raphael, E-mail: raphael.goma@lss.supelec.f [Laboratoire des Signaux et Systemes (L2S), CNRS-SUPELEC, Universite Paris XI, 3 Rue Joliot Curie, 91192 Gif-sur-Yvette (France); Nkwawo, Homere, E-mail: homere.nkwawo@iutv.univ-paris13.f [Departement GEII, Universite Paris XIII, 99 Avenue Jean Baptiste Clement, 93430 Villetaneuse (France); Lamnabhi-Lagarrigue, Francoise, E-mail: lamnabhi@lss.supelec.f [Laboratoire des Signaux et Systemes (L2S), CNRS-SUPELEC, Universite Paris XI, 3 Rue Joliot Curie, 91192 Gif-sur-Yvette (France); Arzande, Amir, E-mail: Amir.arzande@supelec.f [Departement Energie, Ecole Superieure d' Electricite-SUPELEC, 3 Rue Joliot Curie, 91192 Gif-sur-Yvette (France); Vannier, Jean Claude, E-mail: Jean-claude.vannier@supelec.f [Departement Energie, Ecole Superieure d' Electricite-SUPELEC, 3 Rue Joliot Curie, 91192 Gif-sur-Yvette (France)

2010-01-15

A nonlinear adaptive excitation controller is proposed to enhance the transient stability and voltage regulation of synchronous generators with unknown power angle and mechanical power input. The proposed method is based on a standard third-order model of a synchronous generator which requires only information about the physical available measurements of relative angular speed, active electric power, infinite bus and generator terminal voltages. The operating conditions are computed online using the above physical available measurements, the terminal voltage reference value and the estimate of the mechanical power input. The proposed design is therefore capable of providing satisfactory voltage in the presence of unknown variations of the power system operating conditions. Using the concept of sliding mode equivalent control techniques, a robust decentralized adaptive controller which insures the exponential convergence of the outputs to the desired ones, is obtained. Real-time experimental results are reported, comparing the performance of the proposed adaptive nonlinear control scheme to one of the conventional AVR/PSS controller. The high simplicity of the overall adaptive control scheme and its robustness with respect to line impedance variation including critical unbalanced operating condition and temporary turbine fault, constitute the main positive features of the proposed approach.

Benchmarking of Voltage Sag Generators

DEFF Research Database (Denmark)

Yang, Yongheng; Blaabjerg, Frede; Zou, Zhixiang

2012-01-01

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...

Temporal and voltage stress stability of high performance indium-zinc-oxide thin film transistors

Science.gov (United States)

Song, Yang; Katsman, Alexander; Butcher, Amy L.; Paine, David C.; Zaslavsky, Alexander

2017-10-01

Thin film transistors (TFTs) based on transparent oxide semiconductors, such as indium zinc oxide (IZO), are of interest due to their improved characteristics compared to traditional a-Si TFTs. Previously, we reported on top-gated IZO TFTs with an in-situ formed HfO2 gate insulator and IZO active channel, showing high performance: on/off ratio of ∼107, threshold voltage VT near zero, extracted low-field mobility μ0 = 95 cm2/V·s, and near-perfect subthreshold slope at 62 mV/decade. Since device stability is essential for technological applications, in this paper we report on the temporal and voltage stress stability of IZO TFTs. Our devices exhibit a small negative VT shift as they age, consistent with an increasing carrier density resulting from an increasing oxygen vacancy concentration in the channel. Under gate bias stress, freshly annealed TFTs show a negative VT shift during negative VG gate bias stress, while aged (>1 week) TFTs show a positive VT shift during negative VG stress. This indicates two competing mechanisms, which we identify as the field-enhanced generation of oxygen vacancies and the field-assisted migration of oxygen vacancies, respectively. A simplified kinetic model of the vacancy concentration evolution in the IZO channel under electrical stress is provided.

Improvement of high voltage cycling performance and thermal stability of lithium-ion cells by use of a thiophene additive

Energy Technology Data Exchange (ETDEWEB)

Lee, Ki-Soo; Sun, Yang-Kook; Kim, Dong-Won [Department of Chemical Engineering, Hanyang University, Seungdong-gu, Seoul 133-791 (Korea); Noh, Jaegeun [Department of Chemistry, Hanyang University, Seungdong-gu, Seoul 133-791 (Korea); Song, Kwang Soup [Advanced Medical Device Center, Korea Electrotechnology, Research Institute, Ansan, Gyeonggi-do 426-170 (Korea)

2009-10-15

This study demonstrates that the addition of thiophene improves the cycle life of lithium-ion cells at high voltage. Electrochemical impedance spectroscopy results suggest that addition of thiophene significantly suppresses the increase of the charge transfer resistance that occurs during cycling up to high voltage. Differential scanning calorimetric studies showed that the thermal stability of fully charged LiCoO{sub 2} cathode was also enhanced in the presence of thiophene. (author)

High voltage transmission of electrical energy over long distances

Energy Technology Data Exchange (ETDEWEB)

Tewari, S W

1962-07-01

Technical aspects of ac transmission lines, additional means of improving stability ac transmisson lines, insulation problems, ac transmission by cables, high voltage dc transmission, advantages of dc over ac transmission, disadvantages of dc transmission, use of underground cables for dc transmission, history of the development of conversion equipment; transmission schemes adopted on Gotland Island, Sweden; and economics of ac and dc transmission are discussed.

Performance, stability and operation voltage optimization of screen-printed aqueous supercapacitors.

Science.gov (United States)

Lehtimäki, Suvi; Railanmaa, Anna; Keskinen, Jari; Kujala, Manu; Tuukkanen, Sampo; Lupo, Donald

2017-04-06

Harvesting micropower energy from the ambient environment requires an intermediate energy storage, for which printed aqueous supercapacitors are well suited due to their low cost and environmental friendliness. In this work, a systematic study of a large set of devices is used to investigate the effect of process variability and operating voltage on the performance and stability of screen printed aqueous supercapacitors. The current collectors and active layers are printed with graphite and activated carbon inks, respectively, and aqueous NaCl used as the electrolyte. The devices are characterized through galvanostatic discharge measurements for quantitative determination of capacitance and equivalent series resistance (ESR), as well as impedance spectroscopy for a detailed study of the factors contributing to ESR. The capacitances are 200-360 mF and the ESRs 7.9-12.7 Ω, depending on the layer thicknesses. The ESR is found to be dominated by the resistance of the graphite current collectors and is compatible with applications in low-power distributed electronics. The effects of different operating voltages on the capacitance, leakage and aging rate of the supercapacitors are tested, and 1.0 V found to be the optimal choice for using the devices in energy harvesting applications.

Modelling voltage sag mitigation using dynamic voltage restorer and analyzing power quality issue

Science.gov (United States)

Ismail, Nor Laili; Hidzir, Hizrin Dayana Mohd; Thanakodi, Suresh; Nazar, Nazatul Shiema Moh; Ibrahim, Pungut; Ali, Che Ku Muhammad Sabri Che Ku

2018-02-01

Power quality problem which are arise due to a fault or a pulsed load can have caused an interruption of critical load. The modern power systems are becoming more sensitive to the quality of the power supplied by the utility company. Voltage sags and swells, flicker, interruptions, harmonic distortion and other distortion to the sinusoidal waveform are the examples of the power quality problems. The most affected due to these problems is industrial customers who use a lot of sensitive equipment. There has suffered a huge loss to these problems. Resulting of broken or damage equipment if voltage sag exceeds the sensitive threshold of the equipment. Thus, device such as Static Synchronous Compensator (STATCOM) and Dynamic Voltage Restorer (DVR) has been created to solve this problem among users. DVR is a custom power device that most effective and efficient. This paper intended to report the DVR operations during voltage sag compensation.

An Efficient Approach for Fast and Accurate Voltage Stability Margin Computation in Large Power Grids

Directory of Open Access Journals (Sweden)

Heng-Yi Su

2016-11-01

Full Text Available This paper proposes an efficient approach for the computation of voltage stability margin (VSM in a large-scale power grid. The objective is to accurately and rapidly determine the load power margin which corresponds to voltage collapse phenomena. The proposed approach is based on the impedance match-based technique and the model-based technique. It combines the Thevenin equivalent (TE network method with cubic spline extrapolation technique and the continuation technique to achieve fast and accurate VSM computation for a bulk power grid. Moreover, the generator Q limits are taken into account for practical applications. Extensive case studies carried out on Institute of Electrical and Electronics Engineers (IEEE benchmark systems and the Taiwan Power Company (Taipower, Taipei, Taiwan system are used to demonstrate the effectiveness of the proposed approach.

ROBUST ALGORITHMS OF PARAMETRIC ESTIMATION IN SOME STABILIZATION PROBLEMS

Directory of Open Access Journals (Sweden)

A.A. Vedyakov

2016-07-01

Full Text Available Subject of Research.The tasks of dynamic systems provision in the stable state by means of ensuring of trite solution stability for various dynamic systems in the education regime with the aid of their parameters tuning are considered. Method. The problems are solved by application of ideology of the robust finitely convergent algorithms creation. Main Results. The concepts of parametric algorithmization of stability and steady asymptotic stability are introduced and the results are presented on synthesis of coarsed gradient algorithms solving the proposed tasks for finite number of iterations with the purpose of the posed problems decision. Practical Relevance. The article results may be called for decision of practical stabilization tasks in the process of various engineering constructions and devices operation.

Neural-net based calculation of voltage dips at maximum angular swing in direct transient stability analysis [of power systems

Energy Technology Data Exchange (ETDEWEB)

Djukanovic, M [Inst. ' Nikola Tesla' , Belgrade (Yugoslavia); Sobajic, D J; Pao, Yohhan [Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Electrical Engineering and Applied Physics Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Computer Engineering and Science AI WARE inc., Cleveland, OH (United States)

1992-10-01

In heavily stressed power systems, post-fault transient voltage dips can lead to undesired tripping of industrial drives and large induction motors. The lowest transient voltage dips occur when fault clearing times are less than critical ones. In this paper, we propose a new iterative analytical methodology to obtain more accurate estimates of voltage dips at maximum angular swing in direct transient stability analysis. We also propose and demonstrate the possibility of storing the results of these computations in the associative memory (AM) system, which exhibits remarkable generalization capabilities. Feature-based models stored in the AM can be utilized for fast and accurate prediction of the location, duration and the amount of the worst voltage dips, thereby avoiding the need and cost for lengthy time-domain simulations. Numerical results obtained using the example of the New England power system are presented to illustrate our approach. (Author)

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

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...... 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...

Evaluation of enhancements to Thevenin equivalent based methods for real-time voltage stability assessment

DEFF Research Database (Denmark)

Perez, Angel; Jóhannsson, Hjörtur; Østergaard, Jacob

2014-01-01

The possibilities offered by the use of Phasor Measurement Units (PMU) in real - time monitoring provide interesting ways to ensure secure operation of power systems. This paper studies the specific case of voltage stability and the possible improvements to the Thevenin equivalent methods, which...... is applied generally with local measurements. This paper uses the PMU measurements to calculate the grid transformation coefficients to obtain wide - area information. This is achieved by studying the generator's electromo tive force estimated using values in the coefficient transformation matrix...

Effects of switching frequency and leakage inductance on slow-scale stability in a voltage controlled flyback converter

International Nuclear Information System (INIS)

Wang Fa-Qiang; Ma Xi-Kui

2013-01-01

The effects of both the switching frequency and the leakage inductance on the slow-scale stability in a voltage controlled flyback converter are investigated in this paper. Firstly, the system description and its mathematical model are presented. Then, the improved averaged model, which covers both the switching frequency and the leakage inductance, is established, and the effects of these two parameters on the slow-scale stability in the system are analyzed. It is found that the occurrence of Hopf bifurcation in the system is the main reason for losing its slow-scale stability and both the switching frequency and the leakage inductance have an important effect on this slow-scale stability. Finally, the effectiveness of the improved averaged model and that of the corresponding theoretical analysis are confirmed by the simulation results and the experimental results. (general)

Low cost concepts to reduce the voltage ripple of the DC power supply

International Nuclear Information System (INIS)

Cheng, Y.; Liu, K.B.

1993-01-01

If the gain of current feedback is low, the short term stability of magnet power supply will be affected by a soft power line. Typically, the step-charge and the imbalance of the three phase power line cause the most serious voltage ripple. Usually, the voltage feedback with a coupling transformer is considered to reduce the voltage ripple. However, for the high current power supply, the space and cooling problem of the coupling transformer become inconvenient. In this paper, the authors suggest to use the toroidal core with the compensation winding, working like a DCCT, as the coupling transformer. Then, a high speed detector of the AC line level is developed. It restricts the voltage ripple passing to the coupling transformer. These methods have the advantage of small size, low power consumption and low cost

Evaluation of the actual model of transformers with Variable Tap in voltage stability studies; Avaliacao do modelo atual de transformadores com tap variavel em estudos de estabilidade de tensao

Energy Technology Data Exchange (ETDEWEB)

Ferreira, C.A. [Centrais Eletricas Brasileiras S.A. (ELETROBRAS), Rio de Janeiro, RJ (Brazil)], E-mail: carlosaparecido@eletrobras.com; Prada, R.B. [Pontificia Universidade Catolica (PUC-Rio), Rio de Janeiro, RJ (Brazil)], E-mail: prada@ele.puc-rio.br; Costa, V.M. da [Universidade Federal de Juiz de Fora (UFJF), MG (Brazil). Programa de Pos-Graduacao em Engenharia Eletrica], E-mail: vander@lacee.ufjf.br

2009-07-01

This paper addresses the impacts of the world-wide used model of load tap changer transformers - LTCs in voltage stability analysis. Two fundamental questions will be examined: the voltage stability margin and the effect of voltage control actions in the abnormal operation region. It may be easily observed that, in a 2-bus system, the point of collapse and the equivalent impedance which represents the load, will or will not vary, according to the direction of the flow, when the tap is changed. Intuitively, however, it was imagined that this dependence with the flow direction would not occur in a real transformer. It was confirmed through laboratory tests, so it can be concluded that the LCT model, used all over the world, is not adequate to be used in voltage stability analysis. By using the usual model, it is also shown that there are signs that incorrect information regarding voltage control actions can be provided to the operators if the system is operating in the abnormal region. (author)

Voltage control of a power-frequency E-beam irradiator

International Nuclear Information System (INIS)

Zhou Zhizhong; Hu Shouming; Wang Jun; Guo Honglei; Su Haijun

2012-01-01

Voltage stability and precision are key specifications of an electron beam irradiator. A voltage control system was developed for smooth high voltage regulating on a power frequency electron accelerator. Pillar variac driven by servo motor was used as the regulating device, with a programmable logic controller as the control unit. An industrial PC was employed to realize human-machine interaction. Open-loop and closed-loop modes were employed to regulate the high voltage. Experimental results show that the speed, stability and precision for high voltage regulating were improved greatly, hence a much better performance of the electron accelerator. (authors)

Modernization of the Light generators voltage regulation systems and evaluation of the necessity of stabilizers

Energy Technology Data Exchange (ETDEWEB)

Barros, Paulo R.G.M. de; Oliveira Aires, Joao C. de; Nascimento, Anselmo R; Almeida, Antonio J.B. de [Light Servicos de Eletricidade SA, Rio de Janeiro, RJ (Brazil); Souza Pedroso, Alquindar de [Centro de Pesquisas de Energia Eletrica, Rio de Janeiro, RJ (Brazil)

1988-12-31

This paper presents the studies and solutions adopted by Light to mitigate the problems relative to the lack of power and voltage oscillation damping in the Rio de Janeiro area (Southeast Brazil) for the contingencies of South/Southeast interconnection loss and 500 kV transmission line loss. The characteristics of Light generating system, comprised of the Fontes Velha, Fontes Nova, Ilha dos Pombos, Nilo Pecanha, and Pereira Passos hydroelectric plants are shown. Excitation/Voltage regulation alternatives are also presented. The performance of proposed equipment is discussed based on some simulation analysis. Finally, some alternatives for improvement of Rio de Janeiro area dynamic performance are suggested. 4 refs., 3 tabs., 5 figs.

Wind energy systems solutions for power quality and stabilization

CERN Document Server

Ali, Mohd Hasan

2012-01-01

Unlike conventional power plants, wind plants emit no air pollutants or greenhouse gases--and wind energy is a free, renewable resource. However, the induction machines commonly used as wind generators have stability problems similar to the transient stability of synchronous machines. To minimize power, frequency, and voltage fluctuations caused by network faults or random wind speed variations, control mechanisms are necessary. Wind Energy Systems: Solutions for Power Quality and Stabilization clearly explains how to solve stability and power quality issues of wind generator systems. Covering

Diagrams of ion stability in radio-frequency mass spectrometry

International Nuclear Information System (INIS)

Sudakov, M.Yu.

1994-01-01

For solving radio-frequency mass spectrometry problems and dynamic ion containment are studied and systematized different ways for constructing the ion stability diagrams. A new universal set of parameters is proposed for diagram construction-angular variables, which are the phase raid of ion oscillational motion during positive and negative values of the supplying voltage. An effective analytical method is proposed for optimization of the parameters of the pulsed supplying voltage, in particular its repetition rate

Two types of photomultiplier voltage dividers for high and changing count rates

International Nuclear Information System (INIS)

Reiter, W.L.; Stengl, G.

1980-01-01

We report on the design of two types of voltage distribution circuits for high stability photomultiplier operation. 'Type A' voltage divider is an ohmic voltage divider with high bleeder current (up to 10 mA) and the resistor chain split at one of the last dynodes, usually the dynode where the analog signal is derived from. This simple constructive measure improves the stability of the dynode voltage by a factor of 5 compared with an unsplit conventional resistor chain. 'Type B' is a novel active voltage divider using cold cathode tubes ar regulating elements. This voltage divider exhibits excellent temperature stability (about 10 -4 / 0 C). With 'type B' an equal stability compared with conventional ohmic dividers can be achieved at a bleeder current smaller by one order of magnitude. Of course both concepts, 'type A' and 'type B', can be combined. (orig.)

Nash equilibrium strategies of generating companies (Gencos) in the simultaneous operation of active and reactive power market, with considering voltage stability margin

International Nuclear Information System (INIS)

Soleymani, S.

2013-01-01

Highlights: ► We model the behavior of Gencos in the active and reactive power markets. ► Genco’s strategy is modeled as a bi-level optimization problem. ► The ISO’s market clearing model is modified with applying generator APFs. ► Good forecast of Genco’s information will increase the accuracy of proposed method. ► Obtained profit of Gencos depend on their bidding strategy. - Abstract: As Gencos are responsible for providing active and reactive power generation, they should devise good bidding strategies for energy and reactive power market. The paper describes a method for analyzing the competition among transmission-constrained Gencos with incomplete information. The proposed methodology employs the Supply Function Equilibrium (SFE) for modeling a Genco’s bidding strategy in energy market and uses Expected Payment Function (EPF) to construct a bidding framework in the reactive power market. The problem of finding the optimum strategy of Gencos is modeled as a bi-level optimization problem, where the upper sub-problem represents individual Genco’s payoff and the lower sub-problem solves the ISO’s market clearing problem. The ISO’s market clearing model is modified with applying generator Active Participation Factors to improve the voltage stability margin. The IEEE 39 bus test system is used to verify the effectiveness of the proposed method.

An adaptive recurrent neural-network controller using a stabilization matrix and predictive inputs to solve a tracking problem under disturbances.

Science.gov (United States)

Fairbank, Michael; Li, Shuhui; Fu, Xingang; Alonso, Eduardo; Wunsch, Donald

2014-01-01

We present a recurrent neural-network (RNN) controller designed to solve the tracking problem for control systems. We demonstrate that a major difficulty in training any RNN is the problem of exploding gradients, and we propose a solution to this in the case of tracking problems, by introducing a stabilization matrix and by using carefully constrained context units. This solution allows us to achieve consistently lower training errors, and hence allows us to more easily introduce adaptive capabilities. The resulting RNN is one that has been trained off-line to be rapidly adaptive to changing plant conditions and changing tracking targets. The case study we use is a renewable-energy generator application; that of producing an efficient controller for a three-phase grid-connected converter. The controller we produce can cope with the random variation of system parameters and fluctuating grid voltages. It produces tracking control with almost instantaneous response to changing reference states, and virtually zero oscillation. This compares very favorably to the classical proportional integrator (PI) controllers, which we show produce a much slower response and settling time. In addition, the RNN we propose exhibits better learning stability and convergence properties, and can exhibit faster adaptation, than has been achieved with adaptive critic designs. Copyright © 2013 Elsevier Ltd. All rights reserved.

Voltage stability index based optimal placement of static VAR compensator and sizing using Cuckoo search algorithm

Science.gov (United States)

Venkateswara Rao, B.; Kumar, G. V. Nagesh; Chowdary, D. Deepak; Bharathi, M. Aruna; Patra, Stutee

2017-07-01

This paper furnish the new Metaheuristic algorithm called Cuckoo Search Algorithm (CSA) for solving optimal power flow (OPF) problem with minimization of real power generation cost. The CSA is found to be the most efficient algorithm for solving single objective optimal power flow problems. The CSA performance is tested on IEEE 57 bus test system with real power generation cost minimization as objective function. Static VAR Compensator (SVC) is one of the best shunt connected device in the Flexible Alternating Current Transmission System (FACTS) family. It has capable of controlling the voltage magnitudes of buses by injecting the reactive power to system. In this paper SVC is integrated in CSA based Optimal Power Flow to optimize the real power generation cost. SVC is used to improve the voltage profile of the system. CSA gives better results as compared to genetic algorithm (GA) in both without and with SVC conditions.

Boiling heat transfer and stability problems. Final report, November 1, 1976--March 31, 1979

International Nuclear Information System (INIS)

Hsieh, D.Y.

1979-03-01

Substantial progress has been made in two areas relating to the boiling heat transfer: the stability of a vapor-liquid system and the dynamics of bubbles. For the stability problem, a simplified formulation retaining the essential feature of the interfacial mass transfer has been established for the complex interfacial stability problem with mass and heat transfer. The simplified version was first applied to the linear Rayleigh-Taylor and Kelvin--Helmholtz stability problems. General agreement with results from previous more comprehensive treatment is obtained. Then the simplified formulation is utilized to study the nonlinear Rayleigh-Taylor stability problem. It is found that the combined effects of finite amplitude and the heat and mass transfer can stabilize the system in a regime which is linearly unstable. A single non-dimensional parameter can be found to characterize the stability criterion for certain configuration relevant to the problem of boiling heat transfer. For the problem of bubble dynamics, the investigation of the nonlinear coupling between the subharmonic spherical oscillation and the nonspherical oscillation has been carried out

Program for analysis of permanent status and voltage stability; Programa para analisis de estado permanente y estabilidad de tension

Energy Technology Data Exchange (ETDEWEB)

Fernandez Krekeler, Ubaldo [Administracion Nacional de Electricidad (ANDE), Asuncion (Paraguay)]. E-mail: ufernandez@ieee.org; Cardozo Sanchez, Freddy [Mirant Americas (United States)

2001-07-01

In this work is presented a computational tool to evaluate voltage stability based on statistical analysis techniques. This tool was developed in MATLAB and implements routines through which the Q-V y P-V curves can be obtained, as well as the system self-values in relation to a determined operation point.

Reassessment of problems affecting stabilized layers in roads in South Africa

CSIR Research Space (South Africa)

Paige-Green, P

2009-11-01

Full Text Available of stabilization problems. It is concluded that, although there is indubitable proven field and laboratory evidence for carbonation of stabilized layers, there is no solid scientific evidence for the occurrence of the “water driven reactions” in soil stabilization...

Improvement of Voltage Stability in Electrical Network by Using a STATCOM

Directory of Open Access Journals (Sweden)

Kamel MERINI

2014-02-01

Full Text Available This paper aims to clarify power flow without and with static synchronous compensator (STATCOM and searching the best location of STATCOM to improve voltage in the Algerian network. In daily operation where there are all kinds of disturbances such as voltage fluctuations, voltage sags, swells, voltage unbalances and harmonics. STATCOM is modeled as a controllable voltage source. To validate the effectiveness of the Newton-Raphson method algorithm was implemented to solve power flow equations in presence of STATCOM. Case studies are carried out on 59-bus Algerian network test to demonstrate the performance of proposed models. Simulation results show the effectiveness and capability of STATCOM in improving voltage regulation in transmission systems; moreover the power solution using the Newton-Raphson algorithm developed. The STATCOM and the detailed simulation are performed using Matlab program.

Distributed Monitoring of Voltage Collapse Sensitivity Indices

OpenAIRE

Simpson-Porco, John W.; Bullo, Francesco

2016-01-01

The assessment of voltage stability margins is a promising direction for wide-area monitoring systems. Accurate monitoring architectures for long-term voltage instability are typically centralized and lack scalability, while completely decentralized approaches relying on local measurements tend towards inaccuracy. Here we present distributed linear algorithms for the online computation of voltage collapse sensitivity indices. The computations are collectively performed by processors embedded ...

To the problem of reliability of high-voltage accelerators for industrial purposes

International Nuclear Information System (INIS)

Al'bertinskij, B.I.; Svin'in, M.P.; Tsepakin, S.G.

1979-01-01

Statistical data characterizing the reliability of ELECTRON and AVRORA-2 type accelerators are presented. Used as a reliability index was the mean time to failure of the main accelerator units. The analysis of accelerator failures allowed a number of conclusions to be drawn. The high failure rate level is connected with inadequate training of the servicing personnel and a natural period of equipment adjustment. The mathematical analysis of the failure rate showed that the main responsibility for insufficient high reliability rests with selenium diodes which are employed in the high voltage power supply. Substitution of selenium diodes by silicon ones increases time between failures. It is shown that accumulation and processing of operational statistical data will permit more accurate prediction of the reliability of produced high-voltage accelerators, make it possible to cope with the problems of planning optimal, in time, preventive inspections and repair, and to select optimal safety factors and test procedures n time, preventive inspections and repair, and to select optimal safety factors and test procedures n time, prevent

Quasi-stability of a vector trajectorial problem with non-linear partial criteria

Directory of Open Access Journals (Sweden)

Vladimir A. Emelichev

2003-10-01

Full Text Available Multi-objective (vector combinatorial problem of finding the Pareto set with four kinds of non-linear partial criteria is considered. Necessary and sufficient conditions of that kind of stability of the problem (quasi-stability are obtained. The problem is a discrete analogue of the lower semicontinuity by Hausdorff of the optimal mapping. Mathematics Subject Classification 2000: 90C10, 90C05, 90C29, 90C31.

Bin-packing problems with load balancing and stability constraints

DEFF Research Database (Denmark)

Trivella, Alessio; Pisinger, David

apper in a wide range of disciplines, including transportation and logistics, computer science, engineering, economics and manufacturing. The problem is well-known to be N P-hard and difficult to solve in practice, especially when dealing with the multi-dimensional cases. Closely connected to the BPP...... realistic constraints related to e.g. load balancing, cargo stability and weight limits, in the multi-dimensional BPP. The BPP poses additional challenges compared to the CLP due to the supplementary objective of minimizing the number of bins. In particular, in section 2 we discuss how to integrate bin......-packing and load balancing of items. The problem has only been considered in the literature in simplified versions, e.g. balancing a single bin or introducing a feasible region for the barycenter. In section 3 we generalize the problem to handle cargo stability and weight constraints....

PMU-Aided Voltage Security Assessment for a Wind Power Plant: Preprint

Energy Technology Data Exchange (ETDEWEB)

Jiang, H.; Zhang, Y. C.; Zhang, J. J.; Muljadi, E.

2015-04-08

Because wind power penetration levels in electric power systems are continuously increasing, voltage stability is a critical issue for maintaining power system security and operation. The traditional methods to analyze voltage stability can be classified into two categories: dynamic and steady-state. Dynamic analysis relies on time-domain simulations of faults at different locations; however, this method needs to exhaust faults at all locations to find the security region for voltage at a single bus. With the widely located phasor measurement units (PMUs), the Thevenin equivalent matrix can be calculated by the voltage and current information collected by the PMUs. This paper proposes a method based on a Thevenin equivalent matrix to identify system locations that will have the greatest impact on the voltage at the wind power plant’s point of interconnection. The number of dynamic voltage stability analysis runs is greatly reduced by using the proposed method. The numerical results demonstrate the feasibility, effectiveness, and robustness of the proposed approach for voltage security assessment for a wind power plant.

Multiple-Time-Scales Hierarchical Frequency Stability Control Strategy of Medium-Voltage Isolated Microgrid

DEFF Research Database (Denmark)

Zhao, Zhuoli; Yang, Ping; Guerrero, Josep M.

2016-01-01

In this paper, an islanded medium-voltage (MV) microgrid placed in Dongao Island is presented, which integrates renewable-energy-based distributed generations (DGs), energy storage system (ESS), and local loads. In an isolated microgrid without connection to the main grid to support the frequency......, it is more complex to control and manage. Thus in order to maintain the frequency stability in multiple-time-scales, a hierarchical control strategy is proposed. The proposed control architecture divides the system frequency in three zones: (A) stable zone, (B) precautionary zone and (C) emergency zone...... of Zone B. Theoretical analysis, time-domain simulation and field test results under various conditions and scenarios in the Dongao Island microgrid are presented to prove the validity of the introduced control strategy....

Size-dependent dynamic stability analysis of microbeams actuated by piezoelectric voltage based on strain gradient elasticity theory

Energy Technology Data Exchange (ETDEWEB)

Sahmani, Saeid; Bahrami, Mohsen [Amirkabir University of Technology, Tehran (Iran, Islamic Republic of)

2015-01-15

In the current paper, dynamic stability analysis of microbeams subjected to piezoelectric voltage is presented in which the microbeam is integrated with piezoelectric layers on the lower and upper surfaces. Both of the flutter and divergence instabilities of microbeams with clamped-clamped and clamped-free boundary conditions are predicted corresponding to various values of applied voltage. To take size effect into account, the classical Timoshenko beam theory in conjunction with strain gradient elasticity theory is utilized to develop nonclassical beam model containing three additional internal length scale parameters. By using Hamilton's principle, the higher-order governing differential equations and associated boundary conditions are derived. Afterward, generalized differential quadrature method is employed to discretize the size-dependent governing differential equations along with clamped-clamped and clamped-free end supports. The critical piezoelectric voltages corresponding to various values dimensionless length scale parameter are evaluated and compared with those predicted by the classical beam theory. It is revealed that in the case of clamped-free boundary conditions, the both of flutter and divergence instabilities occur. However, for the clamped-clamped microbeams, only divergence instability takes place.

Effects of high voltage electrical stimulation on the rate of pH decline, meat quality and color stability in chilled beef carcasses

OpenAIRE

Mombeni, Ehsan Gharib; Mombeini, Manoochehr Gharib; Figueiredo, Lucas Chaves; Siqueira, Luciano Soares Jacintho; Dias, Debora Testoni

2013-01-01

Objective: To determine the effects of high voltage electrical stimulation (HVES, 800 Voltage) on rapid decreases in pH values and improvements in meat quality. Methods: A total of 50 beef carcasses were applied, divided into two groups, one as a control and another for HVES. Meat quality was evaluated based on M. longissimus dorsi by examining pH and temperature levels at 1, 2, 5, 10 and 24 h, while color stability was examined seven days after slaughter. Results: HVES decreased the pH...

The Problems and Prospects of Rating Assessment of Political Stability

Directory of Open Access Journals (Sweden)

Ирина Анатольевна Белоусова

2015-12-01

Full Text Available The article is devoted to the analysis of principles of qualitative and quantitative approaches to measurement of political stability. The author gives a detailed analysis of the problems and prospects of ratings and indices as tools of political analysis and measurement of political stability.

Stability analysis of a three-phase grid-connected DC power supply with small DC-link capacitor and voltage feed-forward compensation

DEFF Research Database (Denmark)

Török, Lajos; Mathe, L.

2017-01-01

The purpose of this work was to investigate effect of the DC-link voltage feed-forward compensation on the stability of the three-phase-grid connected DC power supply, used for electrolysis application, equipped with small DC link capacitor. In case of weak grid condition, the system...

Resonance analysis in parallel voltage-controlled Distributed Generation inverters

DEFF Research Database (Denmark)

Wang, Xiongfei; Blaabjerg, Frede; Chen, Zhe

2013-01-01

Thanks to the fast responses of the inner voltage and current control loops, the dynamic behaviors of parallel voltage-controlled Distributed Generation (DG) inverters not only relies on the stability of load sharing among them, but subjects to the interactions between the voltage control loops...

Open Problems Related to the Hurwitz Stability of Polynomials Segments

Directory of Open Access Journals (Sweden)

Baltazar Aguirre-Hernández

2018-01-01

Full Text Available In the framework of robust stability analysis of linear systems, the development of techniques and methods that help to obtain necessary and sufficient conditions to determine stability of convex combinations of polynomials is paramount. In this paper, knowing that Hurwitz polynomials set is not a convex set, a brief overview of some results and open problems concerning the stability of the convex combinations of Hurwitz polynomials is then provided.

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......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...... 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....

11th International Seminar on Stability Problems for Stochastic Models

CERN Document Server

Zolotarev, Vladimir

1989-01-01

Traditionally the Stability seminar, organized in Moscow but held in different locations, has dealt with a spectrum of topics centering around characterization problems and their stability, limit theorems, probabil- ity metrics and theoretical robustness. This volume likewise focusses on these main topics in a series of original and recent research articles.

Adaptive Voltage Stability Protection Based on Load Identification Using Phasor Measurement Units

DEFF Research Database (Denmark)

Liu, Leo; Bak, Claus Leth; Chen, Zhe

2011-01-01

collapse. In this paper, the online load identification using measurement-based approach based on Phasor Measurement Units (PMU) was proposed to evaluate the proximity to voltage instability in order to prevent voltage collapse. In the scenarios of disturbances, the proximity to voltage collapse...... scheme based on PMUs is promising, as it prevented the voltage collapse and minimized the load shedding area....

Active Power Filter DC Bus Voltage Piecewise Reaching Law Variable Structure Control

OpenAIRE

Liu, Baolian; Ding, Zujun; Zhao, Huanyu; Jin, Defei

2014-01-01

The DC bus voltage stability control is one key technology to ensure that Active Power Filter (APF) operates stably. The external disturbances such as power grid and load fluctuation and the system parameters changing may affect the stability of APF DC bus voltage and the normal operation of APF. The mathematical model of DC bus voltage is established according to power balance principle and a DC bus voltage piecewise reaching law variable structure control algorithm is proposed to solve the ...

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

Some problems in the technique of high-voltage testing of the accelerating tube gaps in electrostatic accelerators

International Nuclear Information System (INIS)

Romanov, V.A.; Ivanov, V.V.; Mukhametshin, V.I.; Dmitriev, E.P.; Kidalov, A.I.

1983-01-01

Problems arising during high-voltage testing and training of accelerating taubes of electrostatic accelrators are discussed. A rig and technique of the accelerating tube testing and program designed for the processing of the data obtained and sorting out of the samples investigated are described

Digital voltage discriminator

International Nuclear Information System (INIS)

Zhou Zhicheng

1992-01-01

A digital voltage discriminator is described, which is synthesized by digital comparator and ADC. The threshold is program controllable with high stability. Digital region of confusion is approximately equal to 1.5 LSB. This discriminator has a single channel analyzer function model with channel width of 1.5 LSB

MAIA, Eigenvalues for MHD Equation of Tokamak Plasma Stability Problems

International Nuclear Information System (INIS)

Tanaka, Y.; Azumi, M.; Kurita, G.; Tsunematsu, T.; Takeda, T.

1986-01-01

1 - Description of program or function: This program solves an eigenvalue problem zBx=Ax where A and B are real block tri-diagonal matrices. This eigenvalue problem is derived from a reduced set of linear resistive MHD equations which is often employed to study tokamak plasma stability problem. 2 - Method of solution: Both the determinant and inverse iteration methods are employed. 3 - Restrictions on the complexity of the problem: The eigenvalue z must be real

Investigation of voltage swell mitigation using STATCOM

International Nuclear Information System (INIS)

Razak, N A Abdul; Jaafar, S; Hussain, I S

2013-01-01

STATCOM is one of the best applications of a self commutated FACTS device to control power quality problems in the distribution system. This project proposed a STATCOM model with voltage control mechanism. DQ transformation was implemented in the controller system to achieve better estimation. Then, the model was used to investigate and analyse voltage swell problem in distribution system. The simulation results show that voltage swell could contaminate distribution network with unwanted harmonic frequencies. Negative sequence frequencies give harmful effects to the network. System connected with proposed STATCOM model illustrates that it could mitigate this problems efficiently.

TOPICAL REVIEW: The stability for the Cauchy problem for elliptic equations

Science.gov (United States)

Alessandrini, Giovanni; Rondi, Luca; Rosset, Edi; Vessella, Sergio

2009-12-01

We discuss the ill-posed Cauchy problem for elliptic equations, which is pervasive in inverse boundary value problems modeled by elliptic equations. We provide essentially optimal stability results, in wide generality and under substantially minimal assumptions. As a general scheme in our arguments, we show that all such stability results can be derived by the use of a single building brick, the three-spheres inequality. Due to the current absence of research funding from the Italian Ministry of University and Research, this work has been completed without any financial support.

Uncertainty in real-time voltage stability assessment methods based on Thevenin equivalent due to PMU’s accuracy

DEFF Research Database (Denmark)

Perez, Angel; Møller, Jakob Glarbo; Jóhannsson, Hjörtur

2014-01-01

This article studies the influence of PMU’s accuracy in voltage stability assessment, considering the specific case of Th ́ evenin equivalent based methods that include wide-area information in its calculations. The objective was achieved by producing a set of synthesized PMU measurements from...... a time domain simulation and using the Monte Carlo method to reflect the accuracy for the PMUs. This is given by the maximum value for the Total Vector Error defined in the IEEE standard C37.118. Those measurements allowed to estimate the distribution pa- rameters (mean and standard deviation...

Voltage and capacity stability of the Hubble telescope nickel-hydrogen battery

Energy Technology Data Exchange (ETDEWEB)

Vaidyanathan, H. [Communications Satellite Corp., Clarksburg, MD (United States). COMSAT Labs.; Wajsgras, H. [NASA Goddard Space Flight Center, Greenbelt, MD (United States); Rao, G.M. [NASA Goddard Space Flight Center, Greenbelt, MD (United States)

1996-01-01

The power system of the Ubble Space Telescope includes two orbital replacement units, each containing three nickel-hydrogen (Ni-H{sub 2}) batteries of 88 Ah capacity. Since launch in April 1990, the batteries have completed 23 000 charge and discharge cycles and continue to meet the power demands of the satellite. The voltage, capacity, and pressure characteristics of all six batteries were analyzed to determine the state of health of the battery and to identify any signs of performance degradation. The battery pressures have changed to varying degrees. The end-of-charge pressure for battery 4 increased by 96 psi, while that for battery 3 decreased by 37 psi. The voltages of the individual cells show a decay rate of 0.69 mV per 1000 cycles, and the capacity of the batteries has apparently decreased, possibly due to the system being operated at a lower stage of charge. Autonomous battery operation involving charge termination at a preselected voltage continues to restore the energy dissipated during each orbit. The accumulated data on voltages and recharge ratios can be used to design new temperature-compensated voltage levels for similar missions that employ Ni-H{sub 2} batteries. (orig.)

Existence and Stability of Solutions for Implicit Multivalued Vector Equilibrium Problems

Directory of Open Access Journals (Sweden)

Li Qiuying

2011-01-01

Full Text Available A class of implicit multivalued vector equilibrium problems is studied. By using the generalized Fan-Browder fixed point theorem, some existence results of solutions for the implicit multivalued vector equilibrium problems are obtained under some suitable assumptions. Moreover, a stability result of solutions for the implicit multivalued vector equilibrium problems is derived. These results extend and unify some recent results for implicit vector equilibrium problems, multivalued vector variational inequality problems, and vector variational inequality problems.

The Model and Quadratic Stability Problem of Buck Converter in DCM

Directory of Open Access Journals (Sweden)

Li Xiaojing

2016-01-01

Full Text Available Quadratic stability is an important performance for control systems. At first, the model of Buck Converter in DCM is built based on the theories of hybrid systems and switched linear systems primarily. Then quadratic stability of SLS and hybrid feedback switching rule are introduced. The problem of Buck Converter’s quadratic stability is researched afterwards. In the end, the simulation analysis and verification are provided. Both experimental verification and theoretical analysis results indicate that the output of Buck Converter in DCM has an excellent performance via quadratic stability control and switching rules.

Power System Stability Using Decentralized Under Frequency and Voltage Load Shedding

DEFF Research Database (Denmark)

Hoseinzadeh, Bakhtyar; Silva, Filipe Faria Da; Bak, Claus Leth

2014-01-01

information to shed the loads with higher voltage decay first. Therefore, this approach deals with coordination of voltage and frequency information instead of independent methods. Numerical simulations which are carried out in DigSilent PowerFactory software confirm the efficiency of proposed methodology...

DC-Voltage Fluctuation Elimination Through a DC-Capacitor Current Control for DFIG Converters Under Unbalanced Grid Voltage Conditions

DEFF Research Database (Denmark)

Liu, Changjin; Xu, Dehong; Zhu, Nan

2013-01-01

Unbalanced grid voltage causes a large second-order harmonic current in the dc-link capacitors as well as dc-voltage fluctuation, which potentially will degrade the lifespan and reliability of the capacitors in voltage source converters. This paper proposes a novel dc-capacitor current control...... method for a grid-side converter (GSC) to eliminate the negative impact of unbalanced grid voltage on the dc-capacitors. In this method, a dc-capacitor current control loop, where a negative-sequence resonant controller is used to increase the loop gain, is added to the conventional GSC current control...... loop. The rejection capability to the unbalanced grid voltage and the stability of the proposed control system are discussed. The second-order harmonic current in the dc capacitor as well as dc-voltage fluctuation is very well eliminated. Hence, the dc capacitors will be more reliable under unbalanced...

Voltage stability evaluation facing small disturbances by means of the modal analysis technique; Evaluacion de la estabilidad de voltaje ante disturbios pequenos mediante la tecnica de analisis modal

Energy Technology Data Exchange (ETDEWEB)

Leon Rodriguez, Daniel

2000-12-15

The economic development of the countries has taken implicit a growing industrialization the one which, joined to those every time bigger resident's necessities, it has caused a constant and progressive increment in the electric power demand. However, in the last years the growth of the electric network of these systems has been more and more limited for diverse such factors as the ecology and the economy, as well as for the social and political costs that implies each new construction in the system. With the presence of these restrictions the electric systems in many cases, have been forced to satisfy the increments in the demand making a more exhaustive use of the infrastructure that they have available and the incorporation of only a few new system elements or constructions. These aspects have caused such systems to operate with more limited security margins and that their stability has to be analyzed in a reliable and precise way. Taking into account the previously mentioned aspects, as the electric systems have had the necessity of operating under forced conditions to satisfy the load demand, voltage stability problems have been presented with more frequency causing serious disturbances and in some cases, total blackouts. With these problems, the voltage stability analysis has taken bigger importance in the studies that the electric utilities carry out. This issue has caused that bigger resources are dedicated for the investigation of this phenomenon with the purpose of understanding and developing tools that allow studying it in a more complete and more truthful way. Modal analysis is one of the most recent and popular steady techniques the one that, from its appearance has had a great peak due to the valuable and quick information that provides, besides its implementation easiness and the little effort computational that it requires. In this work is carried out the voltage stability evaluation of a real electric system applying in a combined way the

Stability results for the parameter identification inverse problem in cardiac electrophysiology

Science.gov (United States)

Lassoued, Jamila; Mahjoub, Moncef; Zemzemi, Néjib

2016-11-01

In this paper we prove a stability estimate of the parameter identification problem in cardiac electrophysiology modeling. We use the monodomain model which is a reaction diffusion parabolic equation where the reaction term is obtained by solving an ordinary differential equation (ODE). We are interested in proving the stability of the identification of the parameter {τ }{in}, which is the parameter that multiplies the cubic term in the reaction term. The proof of the result is based on a new Carleman-type estimate for both partial differential equation (PDE) and ODE problems. As a consequence of the stability result we prove the uniqueness of the parameter {τ }{in} giving some observations of both state variables at a given time t 0 in the whole domain and in the PDE variable in a non empty open subset w 0 of the domain.

Successful application of Low Voltage Electron Microscopy to practical materials problems

International Nuclear Information System (INIS)

Bell, David C.; Mankin, Max; Day, Robert W.; Erdman, Natasha

2014-01-01

Low-voltage High-Resolution Electron Microscopy (LVHREM) has several advantages, including increased cross-sections for inelastic and elastic scattering, increased contrast per electron, decreased delocalization effects and reduced knock-on damage. Imaging at differing voltages has shown advantages for imaging materials that are knock-on damage sensitive. We show experimentally that different materials systems benefit from low voltage high-resolution microscopy. There are advantages for imaging single layer materials such as graphene at below the knock-on threshold; we present an example of imaging a graphene sheet at 40 kV. We have also examined mesoporous silica decorated with Pd nanoparticles and carbon black functionalized with Pd/Pt nanoparticles. In these cases we show that the lower voltage imaging maintains the structure of the surrounding matrix during imaging, whereas aberration correction provides the higher resolution for imaging the nanoparticle lattice. Perhaps surprisingly we show that zeolites damage preferentially by ionization effects (radiolysis). The current literature suggests that below incident energies of 40 kV the damage is mainly radiolitic, whereas at incident energies above 200 kV the knock-on damage and material sputtering will be the dominant effect. Our experimental observations support this conclusion and the effects we have observed at 40 kV are not indicative of knock-on damage. Other nanoscale materials such as thin silicon nanowires also benefit from lower voltage imaging. LVHREM imaging provides an excellent option to avoid beam damage to nanowires; our results suggest that LVHREM is suitable for nanowire-biological composites. Our experimental observations serve as a clear demonstration that even at 40 keV accelerating voltage, LVHREM can be used without inducing beam damage to locate dislocations and other crystalline defects, which may have adverse effects on nanowire device performance. Low voltage operation will likely

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...

Stabilization Algorithms for Large-Scale Problems

DEFF Research Database (Denmark)

Jensen, Toke Koldborg

2006-01-01

The focus of the project is on stabilization of large-scale inverse problems where structured models and iterative algorithms are necessary for computing approximate solutions. For this purpose, we study various iterative Krylov methods and their abilities to produce regularized solutions. Some......-curve. This heuristic is implemented as a part of a larger algorithm which is developed in collaboration with G. Rodriguez and P. C. Hansen. Last, but not least, a large part of the project has, in different ways, revolved around the object-oriented Matlab toolbox MOORe Tools developed by PhD Michael Jacobsen. New...

Voltage Balancing Method on Expert System for 51-Level MMC in High Voltage Direct Current Transmission

Directory of Open Access Journals (Sweden)

Yong Chen

2016-01-01

Full Text Available The Modular Multilevel Converters (MMC have been a spotlight for the high voltage and high power transmission systems. In the VSC-HVDC (High Voltage Direct Current based on Voltage Source Converter transmission system, the energy of DC link is stored in the distributed capacitors, and the difference of capacitors in parameters and charge rates causes capacitor voltage balance which affects the safety and stability of HVDC system. A method of MMC based on the expert system for reducing the frequency of the submodules (SMs of the IGBT switching frequency is proposed. Firstly, MMC with 51 levels for HVDC is designed. Secondly, the nearest level control (NLC for 51-level MMC is introduced. Thirdly, a modified capacitor voltage balancing method based on expert system for MMC-based HVDC transmission system is proposed. Finally, a simulation platform for 51-level Modular Multilevel Converter is constructed by using MATLAB/SIMULINK. The results indicate that the strategy proposed reduces the switching frequency on the premise of keeping submodule voltage basically identical, which greatly reduces the power losses for MMC-HVDC system.

Voltage Stability Control of Electrical Network Using Intelligent Load Shedding Strategy Based on Fuzzy Logic

Directory of Open Access Journals (Sweden)

Houda Jouini

2010-01-01

Full Text Available As a perspective to ensure the power system stability and to avoid the vulnerability leading to the blackouts, several preventive and curative means are adopted. In order to avoid the voltage collapse, load shedding schemes represent a suitable action to maintain the power system service quality and to control its vulnerability. In this paper, we try to propose an intelligent load shedding strategy as a new approach based on fuzzy controllers. This strategy was founded on the calculation of generated power sensitivity degree related to those injected at different network buses. During the fault phase, fuzzy controller algorithms generate monitor vectors ensuring a precalculated load shedding ratio in the purpose to reestablish the power balance and conduct the network to a new steady state.

Numerical Investigations on Several Stabilized Finite Element Methods for the Stokes Eigenvalue Problem

Directory of Open Access Journals (Sweden)

Pengzhan Huang

2011-01-01

Full Text Available Several stabilized finite element methods for the Stokes eigenvalue problem based on the lowest equal-order finite element pair are numerically investigated. They are penalty, regular, multiscale enrichment, and local Gauss integration method. Comparisons between them are carried out, which show that the local Gauss integration method has good stability, efficiency, and accuracy properties, and it is a favorite method among these methods for the Stokes eigenvalue problem.

Stability-index based method for optimal Var planning in distribution feeders

International Nuclear Information System (INIS)

Hamouda, Abdellatif; Zehar, Khaled

2011-01-01

Research highlights: → Optimal Var planning is modelled using heuristic methods. → Capacitor sizes and location are determined by a two stage method. → Capacitor locations are determined using nodes stability-indices. → Their sizes are calculated subject to a new constraint on the branches reactive currents. → The solution is fast and leads to better results without over compensation. -- Abstract: The problem of the reactive energy optimal planning can be solved in a fast and efficient way using heuristic techniques. The latter reduce the number of the control variables to be determined and lead to a near global optimal solution. The capacitor appropriate locations are firstly determined by decisive indices then, their optimal sizes are calculated. In this paper a stability-index based method is presented. The nodes stability-indices are calculated for identifying the most sensitive nodes to be candidate for receiving near optimal standard capacitors that, reduce the feeder power losses, improve the voltage profile and maximise the economic saving (objective function). In this multi-objective optimisation problem, the commonly used voltage constraint is substituted by a new constraint on the branch reactive currents. This new constraint, allows overcoming the over compensation phenomenon by setting positive branch reactive currents. The solution is further improved by regulating the source node voltage. The proposed approach has been tested on several feeder examples and its effectiveness has been demonstrated through comparative studies. The obtained results have shown that the proposed approach leads to a promising and feasible solution.

Stability-index based method for optimal Var planning in distribution feeders

Energy Technology Data Exchange (ETDEWEB)

Hamouda, Abdellatif, E-mail: a_hamouda1@yahoo.f [QUERE Laboratory, Optics and Mechanics Institut, University Ferhat Abbas, Setif 19000 (Algeria); Zehar, Khaled [QUERE Laboratory, Department of Electrical and Electronics Engineering, University of Bahrain, Isa Town (Bahrain)

2011-05-15

Research highlights: {yields} Optimal Var planning is modelled using heuristic methods. {yields} Capacitor sizes and location are determined by a two stage method. {yields} Capacitor locations are determined using nodes stability-indices. {yields} Their sizes are calculated subject to a new constraint on the branches reactive currents. {yields} The solution is fast and leads to better results without over compensation. -- Abstract: The problem of the reactive energy optimal planning can be solved in a fast and efficient way using heuristic techniques. The latter reduce the number of the control variables to be determined and lead to a near global optimal solution. The capacitor appropriate locations are firstly determined by decisive indices then, their optimal sizes are calculated. In this paper a stability-index based method is presented. The nodes stability-indices are calculated for identifying the most sensitive nodes to be candidate for receiving near optimal standard capacitors that, reduce the feeder power losses, improve the voltage profile and maximise the economic saving (objective function). In this multi-objective optimisation problem, the commonly used voltage constraint is substituted by a new constraint on the branch reactive currents. This new constraint, allows overcoming the over compensation phenomenon by setting positive branch reactive currents. The solution is further improved by regulating the source node voltage. The proposed approach has been tested on several feeder examples and its effectiveness has been demonstrated through comparative studies. The obtained results have shown that the proposed approach leads to a promising and feasible solution.

Stability Analysis of Discontinuous Galerkin Approximations to the Elastodynamics Problem

KAUST Repository

Antonietti, Paola F.

2015-11-21

We consider semi-discrete discontinuous Galerkin approximations of both displacement and displacement-stress formulations of the elastodynamics problem. We prove the stability analysis in the natural energy norm and derive optimal a-priori error estimates. For the displacement-stress formulation, schemes preserving the total energy of the system are introduced and discussed. We verify our theoretical estimates on two and three dimensions test problems.

Stability Analysis of Discontinuous Galerkin Approximations to the Elastodynamics Problem

KAUST Repository

Antonietti, Paola F.; Ayuso de Dios, Blanca; Mazzieri, Ilario; Quarteroni, Alfio

2015-01-01

We consider semi-discrete discontinuous Galerkin approximations of both displacement and displacement-stress formulations of the elastodynamics problem. We prove the stability analysis in the natural energy norm and derive optimal a-priori error estimates. For the displacement-stress formulation, schemes preserving the total energy of the system are introduced and discussed. We verify our theoretical estimates on two and three dimensions test problems.

Congestion management considering voltage security of power systems

International Nuclear Information System (INIS)

Esmaili, Masoud; Shayanfar, Heidar Ali; Amjady, Nima

2009-01-01

Congestion in a power network is turned up due to system operating limits. To relieve congestion in a deregulated power market, the system operator pays to market participants, GENCOs and DISCOs, to alter their active powers considering their bids. After performing congestion management, the network may be operated with a low security level because of hitting some flows their upper limit and some voltages their lower limit. In this paper, a novel congestion management method based on the voltage stability margin sensitivities is introduced. Using the proposed method, the system operator so alleviates the congestion that the network can more retain its security. The proposed method not only makes the system more secure after congestion management than other methods already presented for this purpose but also its cost of providing security is lower than the earlier methods. Test results of the proposed method along with the earlier ones on the New-England test system elaborate the efficiency of the proposed method from the viewpoint of providing a better voltage stability margin and voltage profile as well as a lower security cost. (author)

A Decentralized Multivariable Robust Adaptive Voltage and Speed Regulator for Large-Scale Power Systems

Science.gov (United States)

Okou, Francis A.; Akhrif, Ouassima; Dessaint, Louis A.; Bouchard, Derrick

2013-05-01

This papter introduces a decentralized multivariable robust adaptive voltage and frequency regulator to ensure the stability of large-scale interconnnected generators. Interconnection parameters (i.e. load, line and transormer parameters) are assumed to be unknown. The proposed design approach requires the reformulation of conventiaonal power system models into a multivariable model with generator terminal voltages as state variables, and excitation and turbine valve inputs as control signals. This model, while suitable for the application of modern control methods, introduces problems with regards to current design techniques for large-scale systems. Interconnection terms, which are treated as perturbations, do not meet the common matching condition assumption. A new adaptive method for a certain class of large-scale systems is therefore introduces that does not require the matching condition. The proposed controller consists of nonlinear inputs that cancel some nonlinearities of the model. Auxiliary controls with linear and nonlinear components are used to stabilize the system. They compensate unknown parametes of the model by updating both the nonlinear component gains and excitation parameters. The adaptation algorithms involve the sigma-modification approach for auxiliary control gains, and the projection approach for excitation parameters to prevent estimation drift. The computation of the matrix-gain of the controller linear component requires the resolution of an algebraic Riccati equation and helps to solve the perturbation-mismatching problem. A realistic power system is used to assess the proposed controller performance. The results show that both stability and transient performance are considerably improved following a severe contingency.

Stability, pseudostability and quasistability of vector trajectorial lexicographic optimization problem

Directory of Open Access Journals (Sweden)

R. Berdysheva

1998-03-01

Full Text Available Lower bounds of stability, pseudostability and quasistability radii of lexicographic set in vector combinatorial problem on systems of subsets of finite set with partial criteria of more general kinds have been found.

Calibration of the ISOLDE acceleration voltage using a high-precision voltage divider and applying collinear fast beam laser spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Krieger, A., E-mail: kriegea@uni-mainz.d [Institut fuer Kernchemie, Johannes Gutenberg, Universitaet Mainz, Fritz-Strassmann-Weg 2, 55128 Mainz (Germany); Geppert, Ch. [Institut fuer Kernchemie, Johannes Gutenberg, Universitaet Mainz, Fritz-Strassmann-Weg 2, 55128 Mainz (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung, 64291 Darmstadt (Germany); Catherall, R. [CERN, CH-1211 Geneve 23 (Switzerland); Hochschulz, F. [Institut fuer Kernphysik, Universitaet Muenster, 48149 Muenster (Germany); Kraemer, J.; Neugart, R. [Institut fuer Kernchemie, Johannes Gutenberg, Universitaet Mainz, Fritz-Strassmann-Weg 2, 55128 Mainz (Germany); Rosendahl, S. [Institut fuer Kernphysik, Universitaet Muenster, 48149 Muenster (Germany); Schipper, J.; Siesling, E. [CERN, CH-1211 Geneve 23 (Switzerland); Weinheimer, Ch. [Institut fuer Kernphysik, Universitaet Muenster, 48149 Muenster (Germany); Yordanov, D.T. [Max-Planck-Institut fuer Kernphysik, 69117 Heidelberg (Germany); Noertershaeuser, W. [Institut fuer Kernchemie, Johannes Gutenberg, Universitaet Mainz, Fritz-Strassmann-Weg 2, 55128 Mainz (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung, 64291 Darmstadt (Germany)

2011-03-11

A high-voltage divider with accuracy at the ppm level and collinear laser spectroscopy were used to calibrate the high-voltage installation at the radioactive ion beam facility ISOLDE at CERN. The accurate knowledge of this voltage is particularly important for collinear laser spectroscopy measurements. Beam velocity measurements using frequency-comb based collinear laser spectroscopy agree with the new calibration. Applying this, one obtains consistent results for isotope shifts of stable magnesium isotopes measured using collinear spectroscopy and laser spectroscopy on laser-cooled ions in a trap. The long-term stability and the transient behavior during recovery from a voltage dropout were investigated for the different power supplies currently applied at ISOLDE.

The stability problem in the Kaldor-Kalecki business cycle model

International Nuclear Information System (INIS)

SzydIowski, Marek; Krawiec, Adam

2005-01-01

We consider the Kaldor-Kalecki model of the business cycle which is the modified Kaldor model with the Kalecki time delay in investment. The model is formulated in terms of a second-order nonlinear delay differential equation with a negative feedback. We investigate the problem of stability of cycles caused by retarded action. The method of a centre manifold is used to find the conditions for the Hopf bifurcation. The conditions for stability of limit cycles on the centre manifold is given

Structural mechanism of voltage-dependent gating in an isolated voltage-sensing domain.

Science.gov (United States)

Li, Qufei; Wanderling, Sherry; Paduch, Marcin; Medovoy, David; Singharoy, Abhishek; McGreevy, Ryan; Villalba-Galea, Carlos A; Hulse, Raymond E; Roux, Benoît; Schulten, Klaus; Kossiakoff, Anthony; Perozo, Eduardo

2014-03-01

The transduction of transmembrane electric fields into protein motion has an essential role in the generation and propagation of cellular signals. Voltage-sensing domains (VSDs) carry out these functions through reorientations of positive charges in the S4 helix. Here, we determined crystal structures of the Ciona intestinalis VSD (Ci-VSD) in putatively active and resting conformations. S4 undergoes an ~5-Å displacement along its main axis, accompanied by an ~60° rotation. This movement is stabilized by an exchange in countercharge partners in helices S1 and S3 that generates an estimated net charge transfer of ~1 eo. Gating charges move relative to a ''hydrophobic gasket' that electrically divides intra- and extracellular compartments. EPR spectroscopy confirms the limited nature of S4 movement in a membrane environment. These results provide an explicit mechanism for voltage sensing and set the basis for electromechanical coupling in voltage-dependent enzymes and ion channels.

Stability analysis of transmission system with high penetration of distributed generation

Energy Technology Data Exchange (ETDEWEB)

Reza, M.

2006-12-21

Nowadays, interest in generating electricity using decentralized generators of relatively small scale ('distributed generation', DG) is increasing. This work deals with the impact of implementing DG on the transmission system transient stability, with the emphasis on a potential transition from a 'vertical power system' to a 'horizontal power system. A problem in power systems is maintaining synchronous operation of all (centralized) synchronous machines. This stability problem associated is called rotor angle stability. In this work, the impact of the DG implementation on this is investigated. The impact of DG levels on the system transient stability when the increasing DG level is followed by a reduction of centralized generators in service resulting in a 'vertical to horizontal' transformation of the power system is also investigated. Furthermore, a stochastic analysis is used to study the transient stability of the power systems. The results show that including the stochastic behavior of DG leads to a more complete and detailed view of the system performance. Finally, the situation when the power system is pushed towards a scenario, where DG penetration reaches a level that covers the total load of the original power system (100% DG level) is investigated. The research performed in this work indicates that from the transmission system stability point of view, if higher DG penetration levels are coming up, sufficient inertia and voltage support must be installed. Furthermore, one should be aware of the fact that the system behaves stochastically, especially with DG. To a certain extent regional balancing of power can be performed by local voltage control.

A Comprehensive Strategy for Accurate Reactive Power Distribution, Stability Improvement, and Harmonic Suppression of Multi-Inverter-Based Micro-Grid

Directory of Open Access Journals (Sweden)

Henan Dong

2018-03-01

Full Text Available Among the issues of accurate power distribution, stability improvement, and harmonic suppression in micro-grid, each has been well studied as an individual, and most of the strategies about these issues aim at one inverter-based micro-grid, hence there is a need to establish a model to achieve these functions as a whole, aiming at a multi-inverter-based micro-grid. This paper proposes a comprehensive strategy which achieves this goal successfully; since the output voltage and frequency of micro-grid all consist of fundamental and harmonic components, the strategy contains two parts accordingly. On one hand, a fundamental control strategy is proposed upon the conventional droop control. The virtual impedance is introduced to solve the problem of accurate allocation of reactive power between inverters. Meanwhile, a secondary power balance controller is added to improve the stability of voltage and frequency while considering the aggravating problem of stability because of introducing virtual impedance. On the other hand, the fractional frequency harmonic control strategy is proposed. It can solve the influence of nonlinear loads, micro-grid inverters, and the distribution network on output voltage of inverters, which is focused on eliminating specific harmonics caused by the nonlinear loads, micro-grid converters, and the distribution network so that the power quality of micro-grid can be improved effectively. Finally, small signal analysis is used to analyze the stability of the multi-converter parallel system after introducing the whole control strategy. The simulation results show that the strategy proposed in this paper has a great performance on distributing reactive power, regulating and stabilizing output voltage of inverters and frequency, eliminating harmonic components, and improving the power quality of multi-inverter-based micro-grid.

The motion planning problem and exponential stabilization of a heavy chain. Part II

OpenAIRE

Piotr Grabowski

2008-01-01

This is the second part of paper [P. Grabowski, The motion planning problem and exponential stabilization of a heavy chain. Part I, to appear in International Journal of Control], where a model of a heavy chain system with a punctual load (tip mass) in the form of a system of partial differential equations was interpreted as an abstract semigroup system and then analysed on a Hilbert state space. In particular, in [P. Grabowski, The motion planning problem and exponential stabilization of a h...

Time scales of bias voltage effects in FE/MgO-based magnetic tunnel junctions with voltage-dependent perpendicular anisotropy

International Nuclear Information System (INIS)

Lytvynenko, Ia.M.; Hauet, T.; Montaigne, F.; Bibyk, V.V.; Andrieu, S.

2015-01-01

Interplay between voltage-induced magnetic anisotropy transition and voltage-induced atomic diffusion is studied in epitaxial V/Fe (0.7 nm)/ MgO/ Fe(5 nm)/Co/Au magnetic tunnel junction where thin Fe soft electrode has in-plane or out-of-plane anisotropy depending on the sign of the bias voltage. We investigate the origin of the slow resistance variation occurring when switching bias voltage in opposite polarity. We demonstrate that the time to reach resistance stability after voltage switching is reduced when increasing the voltage amplitude or the temperature. A single energy barrier of about 0.2 eV height is deduced from temperature dependence. Finally, we demonstrate that the resistance change is not correlated to a change in soft electrode anisotropy. This conclusion contrasts with observations recently reported on analogous systems. - Highlights: • Voltage-induced time dependence of resistance is studied in epitaxial Fe/MgO/Fe. • Resistance change is not related to the bottom Fe/MgO interface. • The effect is thermally activated with an energy barrier of the order of 0.2 eV height

Voltage magnitude and margin controller for remote industrial microgrid with high wind penetration

DEFF Research Database (Denmark)

Cai, Yu; Lin, Jin; Song, Yonghua

2013-01-01

It is well known that the remote industrial microgrid is located at the periphery of the grid, which is weakly connected to the main grid. In order to enhance the voltage stability and ensure a good power quality for industries, a voltage magnitude and margin controller based on wind turbines...... is proposed in this paper. This controller includes two parts to improve voltage stability in different time scales by using local measurements. Case studies conducted for a remote microgrid with high wind penetration have proved the effectiveness of the proposed control scheme....

A novel current mode controller for a static compensator utilizing Goertzel algorithm to mitigate voltage sags

International Nuclear Information System (INIS)

Najafi, E.; Yatim, A.H.M.

2011-01-01

Research highlights: → We proposed a new current control method for STATCOM. → The current control method maintains a fixed switching frequency. → It also produces fewer harmonics compared to conventional hysteresis method. → A new voltage dip (sag) detection method was used in STATCOM. → The control method can mitigate voltage sag in each phase separately. -- Abstract: Static compensator (STATCOM) has been widely proposed for power quality and network stability improvement. It is easily connected in parallel to the electric network and has many advantages for electrical grids. It can improve network stability; power factor, power transfer rating and can avoid some disturbances such as sags and swells. Most of STATCOM controllers are based on voltage controllers that are based on balanced d-q transform. However, they are not thorough solutions for network disturbances since in most cases single-phase disturbances occur in electrical networks that cannot be avoided by the conventional controllers. Voltage mode controllers are also not capable of responding fast enough to the changes expected of a network system. This paper proposes a new current mode controller to overcome the mentioned problem. The approach uses a fixed frequency current controller to maintain voltage levels in voltage sags (dips). This approach is also simple and can be easily implemented by digitally. It has superior performance over conventional methods in terms of harmonic reduction in STATCOM output current. Another important factor for STATCOM effectiveness in sag mitigation is its sag detection method. This paper also introduces a new sag detection method based on Goertzel algorithm which is both effective and simple for practical applications. The simulation results presented illustrate the superiority of the proposed controller and sag detection algorithm to be utilized in the STATCOM.

Optimum distributed generation placement with voltage sag effect minimization

International Nuclear Information System (INIS)

Biswas, Soma; Goswami, Swapan Kumar; Chatterjee, Amitava

2012-01-01

Highlights: ► A new optimal distributed generation placement algorithm is proposed. ► Optimal number, sizes and locations of the DGs are determined. ► Technical factors like loss, voltage sag problem are minimized. ► The percentage savings are optimized. - Abstract: The present paper proposes a new formulation for the optimum distributed generator (DG) placement problem which considers a hybrid combination of technical factors, like minimization of the line loss, reduction in the voltage sag problem, etc., and economical factors, like installation and maintenance cost of the DGs. The new formulation proposed is inspired by the idea that the optimum placement of the DGs can help in reducing and mitigating voltage dips in low voltage distribution networks. The problem is configured as a multi-objective, constrained optimization problem, where the optimal number of DGs, along with their sizes and bus locations, are simultaneously obtained. This problem has been solved using genetic algorithm, a traditionally popular stochastic optimization algorithm. A few benchmark systems radial and networked (like 34-bus radial distribution system, 30 bus loop distribution system and IEEE 14 bus system) are considered as the case study where the effectiveness of the proposed algorithm is aptly demonstrated.

Numerical stability in problems of linear algebra.

Science.gov (United States)

Babuska, I.

1972-01-01

Mathematical problems are introduced as mappings from the space of input data to that of the desired output information. Then a numerical process is defined as a prescribed recurrence of elementary operations creating the mapping of the underlying mathematical problem. The ratio of the error committed by executing the operations of the numerical process (the roundoff errors) to the error introduced by perturbations of the input data (initial error) gives rise to the concept of lambda-stability. As examples, several processes are analyzed from this point of view, including, especially, old and new processes for solving systems of linear algebraic equations with tridiagonal matrices. In particular, it is shown how such a priori information can be utilized as, for instance, a knowledge of the row sums of the matrix. Information of this type is frequently available where the system arises in connection with the numerical solution of differential equations.

Transmission of power at high voltages

Energy Technology Data Exchange (ETDEWEB)

Lane, F J

1963-01-01

High voltage transmission is considered to be concerned with circuits and systems operating at or above 132 kV. While the general examination is concerned with ac transmission, dc systems are also included. The choice of voltage for a system will usually involve hazardous assessments of the future requirements of industry, commerce and a changing population. Experience suggests that, if the estimated economic difference between two voltages is not significant, there is good reason to choose the higher voltage, as this will make the better provision for unexpected future expansion. Two principal functions served by transmission circuits in a supply system are: (a) the transportation of energy in bulk from the generator to the reception point in the distribution system; and (b) the interconnection and integration of the generating plant and associated loads. These functions are considered and various types of system are discussed in terms of practicability, viability, quality and continuity of supply. Future developments requiring transmission voltages up to 750 kV will raise many problems which are in the main empirical. Examples are given of the type of problem envisaged and it is suggested that these can only be partially solved by theory and model operation.

Influencing Power Flow and Transient Stability by Static Synchronous Series Compensator

Directory of Open Access Journals (Sweden)

Md. Imran Azim

2015-04-01

Full Text Available In the present world, modern power system networks, being a complicated combination of generators, transmission lines, transformers, circuit breakers and other devices, are more vulnerable to various types of faults causing stability problems. Among these faults, transient fault is believed to be a major disturbance as it causes large damage to a sound system within a certain period of time. Therefore, the protection against transient faults, better known as transient stability control is one of the major considerations for the power system engineers. This paper presents the control approach in the transmission line during transient faults by means of Static Synchronous Series Compensator (SSSC in order to stabilize Single Machine Infinite Bus (SMIB system.  In this paper, SSSC is represented by variable voltage injection associated with the transformer leakage reactance and the voltage source. The comparative results depict that the swing curve of a system increases monotonically after the occurrence of transient faults However, SSSC is effective enough to make it stable after a while.

Synthesis of Li{sub 2}MnO{sub 3}-stabilized LiCoO{sub 2} cathode material by spray-drying method and its high-voltage performance

Energy Technology Data Exchange (ETDEWEB)

Wang, Zhiguo; Wang, Zhixing, E-mail: zxwang.csu@hotmail.com; Guo, Huajun; Peng, Wenjie; Li, Xinhai

2015-03-25

Highlights: • Li{sub 2}MnO{sub 3} is introduced to stabilize the structure of LiCoO{sub 2} at high voltages. • xLi{sub 2}MnO{sub 3}·(1−x)LiCoO{sub 2} with fine particles prepared by a simple spray-drying method. • The modified sample exhibits enhanced high-voltage electrochemical performance. • Possible kinetic behaviors of the electrode surface are discussed. - Abstract: xLi{sub 2}MnO{sub 3}⋅(1 − x)LiCoO{sub 2} (x = 0, 0.02, 0.05, 0.1) as a cathode material for lithium ion batteries has been prepared by a spray-drying assisted solid-state method. The effects of Li{sub 2}MnO{sub 3} content on crystal structure, morphology, and high-voltage electrochemical performance of LiCoO{sub 2} have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and galvanostatic charge–discharge test. XRD results reveal that all samples have a well-ordered layered structure. SEM and EDS analyses confirm that homogeneous powders with a primary particle size of about 2 μm are observed and the elementals distribute uniformly in the particles. Electrochemical tests demonstrate that the modified samples exhibit obviously enhanced cycling stability in the voltage ranges of 3.0–4.5 V and 3.0–4.6 V, although they deliver somewhat lower discharge capacity. Specifically, 0.02Li{sub 2}MnO{sub 3}⋅0.98LiCoO{sub 2} delivers the initial discharge capacity of 189.0, 216.8 mA h g{sup −1} at 0.1 C in the voltage range of 3.0–4.5 V and 3.0–4.6 V, respectively, and excellent cycling behaviors at 1 C are achieved.

A technique for simultaneously improving the product of cutoff frequency–breakdown voltage and thermal stability of SOI SiGe HBT

International Nuclear Information System (INIS)

Fu Qiang; Zhang Wan-Rong; Jin Dong-Yue; Zhao Yan-Xiao; Wang Xiao

2016-01-01

The product of the cutoff frequency and breakdown voltage ( f T ×BV CEO ) is an important figure of merit (FOM) to characterize overall performance of heterojunction bipolar transistor (HBT). In this paper, an approach to introducing a thin N + -buried layer into N collector region in silicon-on-insulator (SOI) SiGe HBT to simultaneously improve the FOM of f T ×BV CEO and thermal stability is presented by using two-dimensional (2D) numerical simulation through SILVACO device simulator. Firstly, in order to show some disadvantages of the introduction of SOI structure, the effects of SOI insulation layer thickness ( T BOX ) on f T , BV CEO , and the FOM of f T ×BV CEO are presented. The introduction of SOI structure remarkably reduces the electron concentration in collector region near SOI substrate insulation layer, obviously reduces f T , slightly increases BV CEO to some extent, but ultimately degrades the FOM of f T ×BV CEO . Although the f T , BV CEO , and the FOM of f T ×BV CEO can be improved by increasing SOI insulator SiO 2 layer thickness T BOX in SOI structure, the device temperature and collector current are increased due to lower thermal conductivity of SiO 2 layer, as a result, the self-heating effect of the device is enhanced, and the thermal stability of the device is degraded. Secondly, in order to alleviate the foregoing problem of low electron concentration in collector region near SOI insulation layer and the thermal stability resulting from thick T BOX , a thin N + -buried layer is introduced into collector region to not only improve the FOM of f T ×BV CEO , but also weaken the self-heating effect of the device, thus improving the thermal stability of the device. Furthermore, the effect of the location of the thin N + -buried layer in collector region is investigated in detail. The result show that the FOM of f T ×BV CEO is improved and the device temperature decreases as the N + -buried layer shifts toward SOI substrate insulation layer

Cavity Voltage Phase Modulation MD

CERN Document Server

Mastoridis, Themistoklis; Molendijk, John; Timko, Helga; CERN. Geneva. ATS Department

2016-01-01

The LHC RF/LLRF system is currently configured for extremely stable RF voltage to minimize transient beam loading effects. The present scheme cannot be extended beyond nominal beam current since the demanded power would exceed the peak klystron power and lead to saturation. A new scheme has therefore been proposed: for beam currents above nominal (and possibly earlier), the cavity phase modulation by the beam will not be corrected (transient beam loading), but the strong RF feedback and One-Turn Delay feedback will still be active for loop and beam stability in physics. To achieve this, the voltage set point will be adapted for each bunch. The goal of this MD was to test a new algorithm that would adjust the voltage set point to achieve the cavity phase modulation that would minimize klystron forward power.

Calibration of the ISOLDE acceleration voltage using a high-precision voltage divider and applying collinear fast beam laser spectroscopy

CERN Document Server

Krieger, A.; Catherall, R.; Hochschulz, F.; Kramer, J.; Neugart, R.; Rosendahl, S.; Schipper, J.; Siesling, E.; Weinheimer, Ch.; Yordanov, D.T.; Nortershauser, W.

2011-01-01

A high-voltage divider with accuracy at the ppm level and collinear laser spectroscopy were used to calibrate the highvoltage installation at the radioactive ion beam facility ISOLDE at CERN. The accurate knowledge of this voltage is particularly important for collinear laser spectroscopy measurements. Beam velocity measurements using frequencycomb based collinear laser spectroscopy agree with the new calibration. Applying this, one obtains consistent results for isotope shifts of stable magnesium isotopes measured using collinear spectroscopy and laser spectroscopy on laser-cooled ions in a trap. The long-term stability and the transient behavior during recovery from a voltage dropout were investigated for the different power supplies currently applied at ISOLDE.

Effective stability around the Cassini state in the spin-orbit problem

Science.gov (United States)

Sansottera, Marco; Lhotka, Christoph; Lemaître, Anne

2014-05-01

We investigate the long-time stability in the neighborhood of the Cassini state in the conservative spin-orbit problem. Starting with an expansion of the Hamiltonian in the canonical Andoyer-Delaunay variables, we construct a high-order Birkhoff normal form and give an estimate of the effective stability time in the Nekhoroshev sense. By extensively using algebraic manipulations on a computer, we explicitly apply our method to the rotation of Titan. We obtain physical bounds of Titan's latitudinal and longitudinal librations, finding a stability time greatly exceeding the estimated age of the Universe. In addition, we study the dependence of the effective stability time on three relevant physical parameters: the orbital inclination, , the mean precession of the ascending node of Titan orbit, , and the polar moment of inertia,.

The Problem of the Instrument Stabilization During Hydrographic Measurements

Directory of Open Access Journals (Sweden)

Felski Andrzej

2016-06-01

Full Text Available Performing any measurement on watercraft is connected with many additional difficulties caused by the sea-environment. The most important is the problem of spatial stabilization of measurement systems, which are usually fastened to craft body. As soon as usually these measurement are executed during the move of the craft additional question is the accuracy of execution the planed trajectory.

On-Line Voltage Stability Assessment based on PMU Measurements

DEFF Research Database (Denmark)

Garcia-Valle, Rodrigo; P. Da Silva, Luiz C.; Nielsen, Arne Hejde

2009-01-01

This paper presents a method for on-line monitoring of risk voltage collapse based on synchronised phasor measurement. As there is no room for intensive computation and analysis in real-time, the method is based on the combination of off-line computation and on-line monitoring, which are correlat...

Problems support economic stability

OpenAIRE

Tkach, Ivan

2012-01-01

. The article is devoted to summarizing the approaches to the classification of the stability of the state's economy, identifying the main characteristics, and offers the author's vision for the classification of the stability of the economy of the state under various conditions of operation.

"Water-in-salt" electrolytes enable the use of cost-effective aluminum current collectors for aqueous high-voltage batteries.

Science.gov (United States)

Kühnel, R-S; Reber, D; Remhof, A; Figi, R; Bleiner, D; Battaglia, C

2016-08-16

The extended electrochemical stability window offered by highly concentrated electrolytes allows the operation of aqueous batteries at voltages significantly above the thermodynamic stability limit of water, at which the stability of the current collector potentially limits the cell voltage. Here we report the observation of suppressed anodic dissolution of aluminum in "water-in-salt" electrolytes enabling roll-to-roll electrode fabrication for high-voltage aqueous lithium-ion batteries on cost-effective light-weight aluminum current collectors using established lithium-ion battery technology.

Degraded voltage protection at nuclear plant safety buses

International Nuclear Information System (INIS)

Haddad, S.Z.; Berger, W.E.

1989-01-01

This paper reviews the events that led to the NRC's degraded voltage protection requirement and outlines the related NRC positions. It describes problems that have occurred with the protection scheme and identifies the measures required to minimize the occurrence of these problems. The paper recommends new guidelines for degraded voltage protection and proposes a protection scheme logic that aims at enhancing the reliability of the safety systems

The moduli and gravitino (non)-problems in models with strongly stabilized moduli

International Nuclear Information System (INIS)

Evans, Jason L.; Olive, Keith A.; Garcia, Marcos A.G.

2014-01-01

In gravity mediated models and in particular in models with strongly stabilized moduli, there is a natural hierarchy between gaugino masses, the gravitino mass and moduli masses: m 1/2 << m 3/2 << m φ . Given this hierarchy, we show that 1) moduli problems associated with excess entropy production from moduli decay and 2) problems associated with moduli/gravitino decays to neutralinos are non-existent. Placed in an inflationary context, we show that the amplitude of moduli oscillations are severely limited by strong stabilization. Moduli oscillations may then never come to dominate the energy density of the Universe. As a consequence, moduli decay to gravitinos and their subsequent decay to neutralinos need not overpopulate the cold dark matter density

Transmission congestion and voltage profile management coordination in competitive electricity markets

International Nuclear Information System (INIS)

Yamin, H.Y.; Shahidehpour, S.M.

2003-01-01

This paper describes a generalized active/reactive iterative coordination process between GENCOs and the Independent System Operator (ISO) for active (transmission congestion) and reactive (voltage profile) management in the day-ahead market. GENCOs apply priced-based unit commitment without transmission and voltage security constraints, schedule their units and submit their initial bids to the ISO. The ISO executes congestion and voltage profile management for eliminating transmission and voltage profile violations. If violations are not eliminated, the ISO minimizes the transmission and voltage profile violations and sends a signal via the Internet to GENCOs. GENCOs reschedule their units taking into account the ISO signals and submit modified bids to the ISO. The voltage problem is addressed and a linear model is formulated and used in the proposed method. The voltage problem is formulated as a linear programming with a block-angular structure and Dantzig-Wolfe decomposition is applied to generate several smaller problems for a faster and easier solution of large-scale power systems. Two 36 unit GENCOs are used to demonstrate the performance of the proposed generalized active/reactive coordination algorithm. (author)

Locational Pricing to Mitigate Voltage Problems Caused by High PV Penetration

OpenAIRE

Sam Weckx; Reinhilde D'hulst; Johan Driesen

2015-01-01

In this paper, a locational marginal pricing algorithm is proposed to control the voltage in unbalanced distribution grids. The increasing amount of photovoltaic (PV) generation installed in the grid may cause the voltage to rise to unacceptable levels during periods of low consumption. With locational prices, the distribution system operator can steer the reactive power consumption and active power curtailment of PV panels to guarantee a safe network operation. Flexible loads also respond to...

Stabilized x-ray generator power supply

International Nuclear Information System (INIS)

Saha, Subimal; Purushotham, K.V.; Bose, S.K.

1986-01-01

X-ray diffraction and X-ray fluorescence analysis are very much adopted in laboratories to determine the type and structure of the constituent compounds in solid materials, chemical composition of materials, stress developed on metals etc. These experiments need X-ray beam of fixed intensity and wave length. This can only be achieved by X-ray generator having highly stabilized tube voltage and tube current. This paper describes how X-ray tube high voltage and electron beam current are stabilized. This paper also highlights generation of X-rays, diffractometry and X-ray fluorescence analysis and their wide applications. Principle of operation for stabilizing the X-ray tube voltage and current, different protection circuits adopted, special features of the mains H.V. transformer and H.T. tank are described in this report. (author)

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.

A novel approach for voltage secure operation using Probabilistic Neural Network in transmission network

Directory of Open Access Journals (Sweden)

Santi Behera

2016-05-01

Full Text Available This work proposes a unique approach for improving voltage stability limit using a Probabilistic Neural Network (PNN classifier that gives corrective controls available in the system in the scenario of contingencies. The sensitivity of system is analyzed to identify weak buses with ENVCI evaluation approaching zero. The input to the classifier, termed as voltage stability enhancing neural network (VSENN classifier, for training are line flows and bus voltages near the notch point of the P–V curve and the output of the VSENN is a control variable. For various contingencies the control action that improves the voltage profile as well as stability index is identified and trained accordingly. The trained VSENN is finally tested for its robustness to improve load margin and ENVCI as well, apart from trained set of operating condition of the system along with contingencies. The proposed approach is verified in IEEE 39-bus test system.

Voltage control in the future power transmission systems

DEFF Research Database (Denmark)

Qin, Nan

Wind energy in Denmark covers 42% of the total power consumption in 2015, and will share up to 50% by 2020. Consequently, the conventional power plants are decommissioning. Under the progress of the green transition, the national decision leads to underground many overhead lines in the future...... stages. The voltage uncertainty caused by the wind power forecasting errors is estimated, which is applied as a voltage security margin to further constrain the voltage magnitude in the optimization problem. The problem under the uncertainty is therefore converted to a deterministic problem, which...... to ensure a highly reliable transmission, e.g. balancing the generation and the consumption in large geographic regions, the exchange capacities will be enlarged by upgrading the interconnections. The Danish power system, the electricity transportation hub between the Nordic and continental European systems...

Voltage regulation in distribution networks with distributed generation

Science.gov (United States)

Blažič, B.; Uljanić, B.; Papič, I.

2012-11-01

The paper deals with the topic of voltage regulation in distribution networks with relatively high distributed energy resources (DER) penetration. The problem of voltage rise is described and different options for voltage regulation are given. The influence of DER on voltage profile and the effectiveness of the investigated solutions are evaluated by means of simulation in DIgSILENT. The simulated network is an actual distribution network in Slovenia with a relatively high penetration of distributed generation. Recommendations for voltage control in networks with DER penetration are given at the end.

Efficient augmented Lagrangian-type preconditioning for the Oseen problem using Grad-Div stabilization

KAUST Repository

Heister, Timo

2012-01-29

Efficient preconditioning for Oseen-type problems is an active research topic. We present a novel approach leveraging stabilization for inf-sup stable discretizations. The Grad-Div stabilization shares the algebraic properties with an augmented Lagrangian-type term. Both simplify the approximation of the Schur complement, especially in the convection-dominated case. We exploit this for the construction of the preconditioner. Solving the discretized Oseen problem with an iterative Krylov-type method shows that the outer iteration numbers are retained independent of mesh size, viscosity, and finite element order. Thus, the preconditioner is very competitive. © 2012 John Wiley & Sons, Ltd.

Efficient augmented Lagrangian-type preconditioning for the Oseen problem using Grad-Div stabilization

KAUST Repository

Heister, Timo; Rapin, Gerd

2012-01-01

Efficient preconditioning for Oseen-type problems is an active research topic. We present a novel approach leveraging stabilization for inf-sup stable discretizations. The Grad-Div stabilization shares the algebraic properties with an augmented Lagrangian-type term. Both simplify the approximation of the Schur complement, especially in the convection-dominated case. We exploit this for the construction of the preconditioner. Solving the discretized Oseen problem with an iterative Krylov-type method shows that the outer iteration numbers are retained independent of mesh size, viscosity, and finite element order. Thus, the preconditioner is very competitive. © 2012 John Wiley & Sons, Ltd.

Temperature stabilization of injection lasers

International Nuclear Information System (INIS)

Albanese, A.

1987-01-01

Apparatus which stabilizes the temperature, and thereby the output wavelength, of an injection laser. Means monitor the laser terminal voltage across a laser and derive a voltage therefrom which is proportional to the junction voltage of the laser. Means compares the voltage to a reference value from source and a temperature controller adjusts the laser temperature in response to the results of the comparison. Further embodiments of the present invention vary the output wavelength of the laser by varying the reference value from source against which the laser junction voltage is compared. (author)

Voltage stability issues in a distribution grid with large scale PV plant

Energy Technology Data Exchange (ETDEWEB)

Perez, Alvaro Ruiz; Marinopoulos, Antonios; Reza, Muhamad; Srivastava, Kailash [ABB AB, Vaesteraas (Sweden). Corporate Research Center; Hertem, Dirk van [Katholieke Univ. Leuven, Heverlee (Belgium). ESAT-ELECTA

2011-07-01

Solar photovoltaics (PV) has become a competitive renewable energy source. The production of solar PV cells and panels has increased significantly, while the cost is reduced due to economics of scale and technological achievements in the field. At the same time, the increase in efficiency of PV power systems and high energy prices are expected to lead PV systems to grid parity in the coming decade. This is expected to boost even more the large scale implementation of PV power plants (utility scale PV) and therefore the impact of such large scale PV plants to power system needs to be studies. This paper investigates the voltage stability issues arising from the connection of a large PV power plant to the power grid. For this purpose, a 15 MW PV power plant was implemented into a distribution grid, modeled and simulated using DIgSILENT Power Factory. Two scenarios were developed: in the first scenario, active power injected into the grid by the PV power plants was varied and the resulted U-Q curve was analyzed. In the second scenario, the impact of connecting PV power plants to different points in the grid - resulting in different strength of the connection - was investigated. (orig.)

PC-based control of a high-voltage injector

International Nuclear Information System (INIS)

Constantin, F.

1998-01-01

The stability of high voltage injectors is one of the major problems in any accelerator system. Most of the troubles encountered in the normal operation of an accelerator are connected with the ion source and associated high voltage platforms, regardless of the source or high voltage generator type. The quality of the ion beam injected in the accelerator strongly depends on the power supplies used in the injector and on the ability to control the non-electrical parameters (gas-flow, temperature, etc.). A wide used method in controlling is based on optical links between high-voltage platform and computer, the adjustments being more or less automated. Although the method mentioned above can be still useful in injector control, a different approach is presented in this work, i.e., the computer itself is placed inside the high-voltage terminal. Only one optical link is still necessary to connect this computer with an user-friendly host at ground potential. Requirements: - varying and monitoring the filament current; - gas flow control in the ion source; - reading the vacuum values; - current and voltage control for the anodic, magnet, extraction, suppression and lens' sources. Even in the high voltage terminal there are compartments with different voltages regardless the floating ground. In our injector the extraction voltage is applied on the top of the ion source including the filament and the anodic voltage. The extraction voltage is of maximum 30 kV. In this situation a second optical link is required to transfer the control for the anodic and magnet source power supply assuming the dedicated computer on the floating ground. One PC is placed inside the high voltage terminal and one PC outside the injector. The optical link (more precisely two optical wires) connects the serial ports. The inside computer is equipped with two multipurpose ADC/DAC and digital I/O card. They permit to read or output DC levels ranging between 0 to 10 volts or TTL signals. The filament

Pseudodifferential Perturbations and Stabilization of Distributed Parameter Systems: Dirichlet Feedback Control Problems

DEFF Research Database (Denmark)

Pedersen, Michael

1991-01-01

The stabilization problems for parabolic and hyperbolic partial differential equations with Dirichlet boundary condition are considered. The systems are stabilized by a boundary feedback in(1) The operator equation,(2) The boundary condition,(3) Both the operator equation and the boundary condition...... turns out to be a shortcut to some of the stabilization results of Lasiecka and Triggiani in [J. Differential Equations, 47 (1983), pp. 245-272], [SIAM J. Control Optim., 21(1983), pp. 766-802], and [Appl. Math. Optim., 8(1981), pp. 1-37], and it illuminates to some extent how a change of boundary...

Solutions Stability of Initial Boundary Problem, Modeling of Dynamics of Some Discrete Continuum Mechanical System

Directory of Open Access Journals (Sweden)

D. A. Eliseev

2015-01-01

Full Text Available The solution stability of an initial boundary problem for a linear hybrid system of differential equations, which models the rotation of a rigid body with two elastic rods located in the same plane is studied in the paper. To an axis passing through the mass center of the rigid body perpendicularly to the rods location plane is applied the stabilizing moment proportional to the angle of the system rotation, derivative of the angle, integral of the angle. The external moment provides a feedback. A method of studying the behavior of solutions of the initial boundary problem is proposed. This method allows to exclude from the hybrid system of differential equations partial differential equations, which describe the dynamics of distributed elements of a mechanical system. It allows us to build one equation for an angle of the system rotation. Its characteristic equation defines the stability of solutions of all the system. In the space of feedback-coefficients the areas that provide the asymptotic stability of solutions of the initial boundary problem are built up.

White OLED with high stability and low driving voltage based on a novel buffer layer MoOx

Energy Technology Data Exchange (ETDEWEB)

Jiang Xueyin [School of Materials Science and Engineering, Shanghai University, Jiading, Shanghai 201800 (China); Zhang Zhilin [School of Materials Science and Engineering, Shanghai University, Jiading, Shanghai 201800 (China); Cao Jin [Key Laboratory of Advanced Display and System Application, Ministry of Education, Shanghai University, Shanghai 200072 (China); Khan, M A [School of Materials Science and Engineering, Shanghai University, Jiading, Shanghai 201800 (China); Khizar-ul-Haq [School of Materials Science and Engineering, Shanghai University, Jiading, Shanghai 201800 (China); Zhu Wenqing [School of Materials Science and Engineering, Shanghai University, Jiading, Shanghai 201800 (China)

2007-09-21

White organic light emitting diodes (WOLEDs) with copper phthalocyanine (CuPc), 4,4',4-prime-tris(N-3-methylphenyl-N-phenyl-amino) triphenylamine (m-MTDATA), tungsten oxide (WO{sub 3}) and molybdenum oxide (MoOx) as buffer layers have been investigated. The MoOx based device shows superior performance with low driving voltage, high power efficiency and much longer lifetime than those with other buffer layers. For the Cell using MoOx as buffer layer and 4,7-diphenyl-1,10-phenanthroline (Bphen) as electron transporting layer (ETL), at the luminance of 1000 cd m{sup -2}, the driving voltage is 4.9 V, which is 4.2 V, 2 V and 0.7 V lower than that of the devices using CuPc (Cell-CuPc), m-MTDATA (Cell-m-MTDATA) and WO{sub 3} (Cell-WO{sub 3}) as buffer layers, respectively. Its power efficiency is 7.67 Lm W{sup -1}, which is 2.37 times higher than that of Cell-CuPc and a little higher than that of Cell-m-MTDATA. The projected half-life under the initial luminance of 100 cd m{sup -2} is 55 260 h, which is more than 4.6 times longer than that of Cell-m-MTDATA and Cell-CuPc. The superior performance of Cell-MoOx is attributed to its high hole injection ability and the stable interface between MoOx and organic material. The work function of MoOx has been measured by the contact potential difference method. The J-V curves of 'hole-only' devices indicate that a small hole injection barrier between MoOx/N,'-bis(naphthalene-1-y1)-N, N'-bis(phenyl)-benzidine (NPB) leads to a strong hole injection, resulting in a low driving voltage and a high stability.

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.

The NH2 terminus regulates voltage-dependent gating of CALHM ion channels.

Science.gov (United States)

Tanis, Jessica E; Ma, Zhongming; Foskett, J Kevin

2017-08-01

Calcium homeostasis modulator protein-1 (CALHM1) and its Caenorhabditis elegans (ce) homolog, CLHM-1, belong to a new family of physiologically important ion channels that are regulated by voltage and extracellular Ca 2+ (Ca 2+ o ) but lack a canonical voltage-sensing domain. Consequently, the intrinsic voltage-dependent gating mechanisms for CALHM channels are unknown. Here, we performed voltage-clamp experiments on ceCLHM-1 chimeric, deletion, insertion, and point mutants to assess the role of the NH 2 terminus (NT) in CALHM channel gating. Analyses of chimeric channels in which the ceCLHM-1 and human (h)CALHM1 NH 2 termini were interchanged showed that the hCALHM1 NT destabilized channel-closed states, whereas the ceCLHM-1 NT had a stabilizing effect. In the absence of Ca 2+ o , deletion of up to eight amino acids from the ceCLHM-1 NT caused a hyperpolarizing shift in the conductance-voltage relationship with little effect on voltage-dependent slope. However, deletion of nine or more amino acids decreased voltage dependence and induced a residual conductance at hyperpolarized voltages. Insertion of amino acids into the NH 2 -terminal helix also decreased voltage dependence but did not prevent channel closure. Mutation of ceCLHM-1 valine 9 and glutamine 13 altered half-maximal activation and voltage dependence, respectively, in 0 Ca 2+ In 2 mM Ca 2+ o , ceCLHM-1 NH 2 -terminal deletion and point mutant channels closed completely at hyperpolarized voltages with apparent affinity for Ca 2+ o indistinguishable from wild-type ceCLHM-1, although the ceCLHM-1 valine 9 mutant exhibited an altered conductance-voltage relationship and kinetics. We conclude that the NT plays critical roles modulating voltage dependence and stabilizing the closed states of CALHM channels. Copyright © 2017 the American Physiological Society.

Design of shielded voltage divider for impulse voltage measurement

International Nuclear Information System (INIS)

Kato, Shohei; Kouno, Teruya; Maruyama, Yoshio; Kikuchi, Koji.

1976-01-01

The dividers used for the study of the insulation and electric discharge phenomena in high voltage equipments have the problems of the change of response characteristics owing to adjacent bodies and of induced noise. To improve the characteristics, the enclosed type divider shielded with metal has been investigated, and the divider of excellent response has been obtained by adopting the frequency-separating divider system, which is divided into two parts, resistance divider (lower frequency region) and capacitance divider (higher frequency region), for avoiding to degrade the response. Theoretical analysis was carried out in the cases that residual inductance can be neglected or can not be neglected in the small capacitance divider, and that the connecting wires are added. Next, the structure of the divider and the design of the electric field for the divider manufactured on the basis of the theory are described. The response characteristics were measured. The results show that 1 MV impulse voltage can be measured within the response time of 10 ns. Though this divider aims at the impulse voltage, the duration time of which is about that of standard lightning impulse, in view of the heat capacity because of the input resistance of 10.5 kΩ, it is expected that the divider can be applied to the voltage of longer duration time by increasing the input resistance in future. (Wakatsuki, Y.)

Dual Regulation of Voltage-Sensitive Ion Channels by PIP2

Directory of Open Access Journals (Sweden)

Aldo A Rodríguez Menchaca

2012-09-01

Full Text Available Over the past 16 years, there has been an impressive number of ion channels shown to be sensitive to the major phosphoinositide in the plasma membrane, phosphatidilinositol 4,5-bisphosphate (PIP2. Among them are voltage-gated channels, which are crucial for both neuronal and cardiac excitability. Voltage-gated calcium (Cav channels were shown to be regulated bidirectionally by PIP2. On one hand, PIP2 stabilized their activity by reducing current rundown but on the other hand it produced a voltage-dependent inhibition by shifting the activation curve to more positive voltages. For voltage-gated potassium (Kv channels PIP2 was first shown to prevent N-type inactivation. Careful examination of the effects of PIP2 on the activation mechanism of Kv1.2 has shown a similar bidirectional regulation as in the Cav channels. The two effects could be distinguished kinetically, in terms of their sensitivities to PIP2 and by distinct molecular determinants. The rightward shift of the Kv1.2 voltage dependence implicated basic residues in the S4-S5 linker and was consistent with stabilization of the inactive state of the voltage sensor. A third type of a voltage-gated ion channel modulated by PIP2 is the hyperpolarization-activated cyclic nucleotide-gated (HCN channel. PIP2 has been shown to enhance the opening of HCN channels by shifting their voltage-dependent activation toward depolarized potentials. The sea urchin HCN channel, SpIH, showed again a PIP2-mediated bidirectional effect but in reverse order than the depolarization-activated Cav and Kv channels: a voltage-dependent potentiation, like the mammalian HCN channels, but also an inhibition of the cGMP-induced current activation. Just like the Kv1.2 channels, distinct molecular determinants underlied the PIP2 dual effects on SpIH channels. The dual regulation of these very different ion channels, all of which are voltage dependent, points to conserved mechanisms of regulation of these channels by PIP2.

Number-to-voltage converter on commutated condensers

International Nuclear Information System (INIS)

Grekhov, Yu.N.

1975-01-01

A code-voltage converter using precision voltage dividers based on commutated capacitors [1] is described which is distinguished by the absence of precision elements. Each digit includes eight field-effect transistors in two 1KT682 microcircuit assemblies and three microcapacitors with a conventional unstable capacitance 6200 pF +- 50%. The converter has a speed of response that is not inferior to that of converters based on R-2R matrices, while in time stability of the characteristics, low interference level, and low output impedance it is superior to such converters

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.

Solving ill-posed control problems by stabilized finite element methods: an alternative to Tikhonov regularization

Science.gov (United States)

Burman, Erik; Hansbo, Peter; Larson, Mats G.

2018-03-01

Tikhonov regularization is one of the most commonly used methods for the regularization of ill-posed problems. In the setting of finite element solutions of elliptic partial differential control problems, Tikhonov regularization amounts to adding suitably weighted least squares terms of the control variable, or derivatives thereof, to the Lagrangian determining the optimality system. In this note we show that the stabilization methods for discretely ill-posed problems developed in the setting of convection-dominated convection-diffusion problems, can be highly suitable for stabilizing optimal control problems, and that Tikhonov regularization will lead to less accurate discrete solutions. We consider some inverse problems for Poisson’s equation as an illustration and derive new error estimates both for the reconstruction of the solution from the measured data and reconstruction of the source term from the measured data. These estimates include both the effect of the discretization error and error in the measurements.

A technique for simultaneously improving the product of cutoff frequency-breakdown voltage and thermal stability of SOI SiGe HBT

Science.gov (United States)

Fu, Qiang; Zhang, Wan-Rong; Jin, Dong-Yue; Zhao, Yan-Xiao; Wang, Xiao

2016-12-01

The product of the cutoff frequency and breakdown voltage (fT×BVCEO) is an important figure of merit (FOM) to characterize overall performance of heterojunction bipolar transistor (HBT). In this paper, an approach to introducing a thin N+-buried layer into N collector region in silicon-on-insulator (SOI) SiGe HBT to simultaneously improve the FOM of fT×BVCEO and thermal stability is presented by using two-dimensional (2D) numerical simulation through SILVACO device simulator. Firstly, in order to show some disadvantages of the introduction of SOI structure, the effects of SOI insulation layer thickness (TBOX) on fT, BVCEO, and the FOM of fT×BVCEO are presented. The introduction of SOI structure remarkably reduces the electron concentration in collector region near SOI substrate insulation layer, obviously reduces fT, slightly increases BVCEO to some extent, but ultimately degrades the FOM of fT×BVCEO. Although the fT, BVCEO, and the FOM of fT×BVCEO can be improved by increasing SOI insulator SiO2 layer thickness TBOX in SOI structure, the device temperature and collector current are increased due to lower thermal conductivity of SiO2 layer, as a result, the self-heating effect of the device is enhanced, and the thermal stability of the device is degraded. Secondly, in order to alleviate the foregoing problem of low electron concentration in collector region near SOI insulation layer and the thermal stability resulting from thick TBOX, a thin N+-buried layer is introduced into collector region to not only improve the FOM of fT×BVCEO, but also weaken the self-heating effect of the device, thus improving the thermal stability of the device. Furthermore, the effect of the location of the thin N+-buried layer in collector region is investigated in detail. The result show that the FOM of fT×BVCEO is improved and the device temperature decreases as the N+-buried layer shifts toward SOI substrate insulation layer. The approach to introducing a thin N+-buried layer

Voltage-dependent gating of hERG potassium channels

Directory of Open Access Journals (Sweden)

Yen May eCheng

2012-05-01

Full Text Available The mechanisms by which voltage-gated channels sense changes in membrane voltage and energetically couple this with opening of the ion conducting pore has been the source of significant interest. In voltage-gated potassium (Kv channels, much of our knowledge in this area comes from Shaker-type channels, for which voltage-dependent gating is quite rapid. In these channels, activation and deactivation are associated with rapid reconfiguration of the voltage-sensing domain unit that is electromechanically coupled, via the S4-S5 linker helix, to the rate-limiting opening of an intracellular pore gate. However, fast voltage-dependent gating kinetics are not typical of all Kv channels, such as Kv11.1 (human ether-a-go-go related gene, hERG, which activates and deactivates very slowly. Compared to Shaker channels, our understanding of the mechanisms underlying slow hERG gating is much poorer. Here, we present a comparative review of the structure-function relationships underlying voltage-dependent gating in Shaker and hERG channels, with a focus on the roles of the voltage sensing domain and the S4-S5 linker that couples voltage sensor movements to the pore. Measurements of gating current kinetics and fluorimetric analysis of voltage sensor movement are consistent with models suggesting that the hERG activation pathway contains a voltage independent step, which limits voltage sensor transitions. Constraints upon hERG voltage sensor movement may result from loose packing of the S4 helices and additional intra-voltage sensor counter charge interactions. More recent data suggest that key amino acid differences in the hERG voltage sensing unit and S4-S5 linker, relative to fast activating Shaker-type Kv channels, may also contribute to the increased stability of the resting state of the voltage sensor.

Plasmas in saline solutions sustained using rectified ac voltages: polarity and frequency effects on the discharge behaviour

International Nuclear Information System (INIS)

Chang Hungwen; Hsu Chengche

2012-01-01

In this work, three major problems, namely severe electrode damage, poor plasma stability and excess power consumption, arising in ac-driven plasmas in saline solutions are solved using a rectified power source. Diagnostic studies on the effects of power source polarity and frequency on the plasma behaviour are performed. Examination of I-V characteristics and temporally resolved light emission shows that the polarity significantly influences the current amplitude when the plasma exists, while the frequency alters the bubble dynamics, which in turn affects the plasma ignition voltage. When the plasma is driven by a rectified ac power source, the electrode erosion is reduced substantially. With a low frequency, moderate applied voltage and positively rectified ac power source (e.g. 100 Hz and 350 V), a stable plasma is ignited in nearly every power cycle. (paper)

F John's stability conditions versus A Carasso's SECB constraint for backward parabolic problems

International Nuclear Information System (INIS)

Lee, Jinwoo; Sheen, Dongwoo

2009-01-01

In order to solve backward parabolic problems John (1960 Commun. Pure. Appl. Math.13 551–85) introduced the two constraints ||u(T)|| ≤ M and ||u(0) − g|| ≤ δ where u(t) satisfies the backward heat equation for t in (0, T) with the initial data u(0). The slow evolution from the continuation boundary (SECB) constraint was introduced by Carasso (1994 SIAM J. Numer. Anal. 31 1535–57) to attain continuous dependence on data for backward parabolic problems even at the continuation boundary t = T. The additional 'SECB constraint' guarantees a significant improvement in stability up to t = T. In this paper, we prove that the same type of stability can be obtained by using only two constraints among the three. More precisely, we show that the a priori boundedness condition ||u(T)|| ≤ M is redundant. This implies that Carasso's SECB condition can be used to replace the a priori boundedness condition of John with an improved stability estimate. Also, a new class of regularized solutions is introduced for backward parabolic problems with an SECB constraint. The new regularized solutions are optimally stable and we also provide a constructive scheme to compute. Finally, numerical examples are provided

Voltage-Dependent Gating of hERG Potassium Channels

Science.gov (United States)

Cheng, Yen May; Claydon, Tom W.

2012-01-01

The mechanisms by which voltage-gated channels sense changes in membrane voltage and energetically couple this with opening of the ion conducting pore has been the source of significant interest. In voltage-gated potassium (Kv) channels, much of our knowledge in this area comes from Shaker-type channels, for which voltage-dependent gating is quite rapid. In these channels, activation and deactivation are associated with rapid reconfiguration of the voltage-sensing domain unit that is electromechanically coupled, via the S4–S5 linker helix, to the rate-limiting opening of an intracellular pore gate. However, fast voltage-dependent gating kinetics are not typical of all Kv channels, such as Kv11.1 (human ether-à-go-go related gene, hERG), which activates and deactivates very slowly. Compared to Shaker channels, our understanding of the mechanisms underlying slow hERG gating is much poorer. Here, we present a comparative review of the structure–function relationships underlying activation and deactivation gating in Shaker and hERG channels, with a focus on the roles of the voltage-sensing domain and the S4–S5 linker that couples voltage sensor movements to the pore. Measurements of gating current kinetics and fluorimetric analysis of voltage sensor movement are consistent with models suggesting that the hERG activation pathway contains a voltage independent step, which limits voltage sensor transitions. Constraints upon hERG voltage sensor movement may result from loose packing of the S4 helices and additional intra-voltage sensor counter-charge interactions. More recent data suggest that key amino acid differences in the hERG voltage-sensing unit and S4–S5 linker, relative to fast activating Shaker-type Kv channels, may also contribute to the increased stability of the resting state of the voltage sensor. PMID:22586397

A new type of accelerator power supply based on voltage-type space vector PWM rectification technology

International Nuclear Information System (INIS)

Wu, Fengjun; Gao, Daqing; Shi, Chunfeng; Huang, Yuzhen; Cui, Yuan; Yan, Hongbin; Zhang, Huajian; Wang, Bin; Li, Xiaohui

2016-01-01

To solve the problems such as low input power factor, a large number of AC current harmonics and instable DC bus voltage due to the diode or thyristor rectifier used in an accelerator power supply, particularly in the Heavy Ion Research Facility in Lanzhou-Cooler Storage Ring (HIRFL-CSR), we designed and built up a new type of accelerator power supply prototype base on voltage-type space vector PWM (SVPWM) rectification technology. All the control strategies are developed in TMS320C28346, which is a digital signal processor from TI. The experimental results indicate that an accelerator power supply with a SVPWM rectifier can solve the problems above well, and the output performance such as stability, tracking error and ripple current meet the requirements of the design. The achievement of prototype confirms that applying voltage-type SVPWM rectification technology in an accelerator power supply is feasible; and it provides a good reference for design and build of this new type of power supply. - Highlights: • Applying SVPWM rectification technology in an accelerator power supply improves its grid-side performance. • New Topology and its control strategies make an accelerator power supply have bidirectional power flow ability. • Hardware and software of controller provide a good reference for design of this new type of power supply.

A new type of accelerator power supply based on voltage-type space vector PWM rectification technology

Energy Technology Data Exchange (ETDEWEB)

Wu, Fengjun, E-mail: wufengjun@impcas.ac.cn [Institute of Modern Physics, CAS, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Gao, Daqing; Shi, Chunfeng; Huang, Yuzhen [Institute of Modern Physics, CAS, Lanzhou 730000 (China); Cui, Yuan [Institute of Modern Physics, CAS, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Yan, Hongbin [Institute of Modern Physics, CAS, Lanzhou 730000 (China); Zhang, Huajian [Institute of Modern Physics, CAS, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Wang, Bin [University of Chinese Academy of Sciences, Beijing 100049 (China); Li, Xiaohui [Institute of Modern Physics, CAS, Lanzhou 730000 (China)

2016-08-01

To solve the problems such as low input power factor, a large number of AC current harmonics and instable DC bus voltage due to the diode or thyristor rectifier used in an accelerator power supply, particularly in the Heavy Ion Research Facility in Lanzhou-Cooler Storage Ring (HIRFL-CSR), we designed and built up a new type of accelerator power supply prototype base on voltage-type space vector PWM (SVPWM) rectification technology. All the control strategies are developed in TMS320C28346, which is a digital signal processor from TI. The experimental results indicate that an accelerator power supply with a SVPWM rectifier can solve the problems above well, and the output performance such as stability, tracking error and ripple current meet the requirements of the design. The achievement of prototype confirms that applying voltage-type SVPWM rectification technology in an accelerator power supply is feasible; and it provides a good reference for design and build of this new type of power supply. - Highlights: • Applying SVPWM rectification technology in an accelerator power supply improves its grid-side performance. • New Topology and its control strategies make an accelerator power supply have bidirectional power flow ability. • Hardware and software of controller provide a good reference for design of this new type of power supply.

Direct model-based predictive control scheme without cost function for voltage source inverters with reduced common-mode voltage

Science.gov (United States)

Kim, Jae-Chang; Moon, Sung-Ki; Kwak, Sangshin

2018-04-01

This paper presents a direct model-based predictive control scheme for voltage source inverters (VSIs) with reduced common-mode voltages (CMVs). The developed method directly finds optimal vectors without using repetitive calculation of a cost function. To adjust output currents with the CMVs in the range of -Vdc/6 to +Vdc/6, the developed method uses voltage vectors, as finite control resources, excluding zero voltage vectors which produce the CMVs in the VSI within ±Vdc/2. In a model-based predictive control (MPC), not using zero voltage vectors increases the output current ripples and the current errors. To alleviate these problems, the developed method uses two non-zero voltage vectors in one sampling step. In addition, the voltage vectors scheduled to be used are directly selected at every sampling step once the developed method calculates the future reference voltage vector, saving the efforts of repeatedly calculating the cost function. And the two non-zero voltage vectors are optimally allocated to make the output current approach the reference current as close as possible. Thus, low CMV, rapid current-following capability and sufficient output current ripple performance are attained by the developed method. The results of a simulation and an experiment verify the effectiveness of the developed method.

Stochastic Dual Algorithm for Voltage Regulation in Distribution Networks with Discrete Loads: Preprint

Energy Technology Data Exchange (ETDEWEB)

Dall-Anese, Emiliano [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Zhou, Xinyang [University of Colorado; Liu, Zhiyuan [University of Colorado; Chen, Lijun [University of Colorado

2017-10-03

This paper considers distribution networks with distributed energy resources and discrete-rate loads, and designs an incentive-based algorithm that allows the network operator and the customers to pursue given operational and economic objectives, while concurrently ensuring that voltages are within prescribed limits. Four major challenges include: (1) the non-convexity from discrete decision variables, (2) the non-convexity due to a Stackelberg game structure, (3) unavailable private information from customers, and (4) different update frequency from two types of devices. In this paper, we first make convex relaxation for discrete variables, then reformulate the non-convex structure into a convex optimization problem together with pricing/reward signal design, and propose a distributed stochastic dual algorithm for solving the reformulated problem while restoring feasible power rates for discrete devices. By doing so, we are able to statistically achieve the solution of the reformulated problem without exposure of any private information from customers. Stability of the proposed schemes is analytically established and numerically corroborated.

The development of a very high stability electrostatic generator (1962)

International Nuclear Information System (INIS)

Jonckheere, R.E.L.

1962-01-01

This thesis deals with the study of an electrostatic high voltage generator having a voltage stability of the order of 10 -6 per minute. This equipment should be very useful in electron microscopy. The electrostatic generator is studied as a control system element: transfer function, parasitic signals and noise are determined and a mathematical model is proposed. A theoretical study of the open loop transfer function, stability, transient response, voltage stabilization of five different control systems shows which one should be able to fulfill the requirements There follows a detailed study of drift, a description of the actual system and performance data. (author) [fr

Storage Solutions for Power Quality Problems in Cyprus Electricity Distribution Network

Directory of Open Access Journals (Sweden)

Andreas Poullikkas

2014-01-01

Full Text Available In this work, a prediction of the effects of introducing energy storage systems on the network stability of the distribution network of Cyprus and a comparison in terms of cost with a traditional solution is carried out. In particular, for solving possible overvoltage problems, several scenarios of storage units' installation are used and compared with the alternative solution of extra cable connection between the node with the lowest voltage and the node with the highest voltage of the distribution network. For the comparison, a case study of a typical LV distribution feeder in the power system of Cyprus is used. The results indicated that the performance indicator of each solution depends on the type, the size and the position of installation of the storage unit. Also, as more storage units are installed the better the performance indicator and the more attractive is the investment in storage units to solve power quality problems in the distribution network. In the case where the technical requirements in voltage limitations according to distribution regulations are satisfied with one storage unit, the installation of an additional storage unit will only increase the final cost. The best solution, however, still remains the alternative solution of extra cable connection between the node with the lowest voltage and the node with the highest voltage of the distribution network, due to the lower investment costs compared to that of the storage units.

Impacts of Wind Power on Power System Stability

NARCIS (Netherlands)

Vittal, E.; Keane, A.; Slootweg, J.G.; Kling, W.L.; Ackermann, T.

2012-01-01

This chapter examines how wind power will impact the stability of power systems. It focuses on the three aspects of power system stability: voltage stability, rotor angle stability and frequency stability. It completes a detailed analysis as to how wind power in power systems will impact the

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

International Nuclear Information System (INIS)

Muyeen, S.M.; Al-Durra, Ahmed; Tamura, J.

2011-01-01

highlights: → Current controlled voltage source inverter scheme for wind power application. → Low voltage ride through of wind farm. → 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.

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.

Stability and periodicity in the Sitnikov three-body problem when primaries are oblate spheroids

Science.gov (United States)

Rahman, M. A.; Garain, D. N.; Hassan, M. R.

2015-05-01

This paper deals with the effect of oblateness of the primaries of equal masses on the series solutions of the Sitnikov problem of three bodies. Effects of oblateness have also been shown on the stability of libration points and Poincare surface of section. Here series solutions have been developed with the help of iteration process of Green's function and by the Lindstedt-Poincare method. Following Murray and Dermott (Solar System Dynamics, Cambridge University Press, Cambridge, 1999) we have checked the stability of the equilibrium points in the Sitnikov problem. Periodicity and quasi-periodicity have been examined by drawing the Poincare surfaces of section using the mathematical software.

Nonlinear control of voltage source converters in AC-DC power system.

Science.gov (United States)

Dash, P K; Nayak, N

2014-07-01

This paper presents the design of a robust nonlinear controller for a parallel AC-DC power system using a Lyapunov function-based sliding mode control (LYPSMC) strategy. The inputs for the proposed control scheme are the DC voltage and reactive power errors at the converter station and the active and reactive power errors at the inverter station of the voltage-source converter-based high voltage direct current transmission (VSC-HVDC) link. The stability and robust tracking of the system parameters are ensured by applying the Lyapunov direct method. Also the gains of the sliding mode control (SMC) are made adaptive using the stability conditions of the Lyapunov function. The proposed control strategy offers invariant stability to a class of systems having modeling uncertainties due to parameter changes and exogenous inputs. Comprehensive computer simulations are carried out to verify the proposed control scheme under several system disturbances like changes in short-circuit ratio, converter parametric changes, and faults on the converter and inverter buses for single generating system connected to the power grid in a single machine infinite-bus AC-DC network and also for a 3-machine two-area power system. Furthermore, a second order super twisting sliding mode control scheme has been presented in this paper that provides a higher degree of nonlinearity than the LYPSMC and damps faster the converter and inverter voltage and power oscillations. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Aetiological influences on stability and change in emotional and behavioural problems across development: a systematic review.

Science.gov (United States)

Hannigan, L J; Walaker, N; Waszczuk, M A; McAdams, T A; Eley, T C

2017-01-01

Emotional and behavioural problems in childhood and adolescence can be chronic and are predictive of future psychiatric problems. Understanding what factors drive the development and maintenance of these problems is therefore crucial. Longitudinal behavioural genetic studies using twin, sibling or adoption data can be used to explore the developmental aetiology of stability and change in childhood and adolescent psychopathology. We present a systematic review of longitudinal, behavioural genetic analyses of emotional and behavioural problems between ages 0 to 18 years. We identified 58 studies, of which 19 examined emotional problems, 30 examined behavioural problems, and 9 examined both. In the majority of studies, stability in emotional and behavioural problems was primarily genetically influenced. Stable environmental factors were also widely found, although these typically played a smaller role. Both genetic and environmental factors were involved in change across development. We discuss the findings in the context of the wider developmental literature and make recommendations for future research.

Control and Protection Cooperation Strategy for Voltage Instability

DEFF Research Database (Denmark)

Liu, Zhou; Chen, Zhe; Sun, Haishun

2012-01-01

Most cascaded blackouts are caused by unexpected backup relay operations due to low voltage or overload state caused by post fault load restoration dynamics. If such state can be sensed and adjusted appropriately prior to those relay actions, system stability might be sustained. This paper proposed...... a control and protection cooperation strategy to prevent post fault voltage instability. The multi-agent technology is applied for the strategy implementation; the criteria based on wide area measured apparent impedances are defined to choose the control strategy, such as tap changer adjusting or load...

Intermediate state trapping of a voltage sensor

DEFF Research Database (Denmark)

Lacroix, Jérôme J; Pless, Stephan Alexander; Maragliano, Luca

2012-01-01

Voltage sensor domains (VSDs) regulate ion channels and enzymes by undergoing conformational changes depending on membrane electrical signals. The molecular mechanisms underlying the VSD transitions are not fully understood. Here, we show that some mutations of I241 in the S1 segment of the Shaker...... Kv channel positively shift the voltage dependence of the VSD movement and alter the functional coupling between VSD and pore domains. Among the I241 mutants, I241W immobilized the VSD movement during activation and deactivation, approximately halfway between the resting and active states......, and drastically shifted the voltage activation of the ionic conductance. This phenotype, which is consistent with a stabilization of an intermediate VSD conformation by the I241W mutation, was diminished by the charge-conserving R2K mutation but not by the charge-neutralizing R2Q mutation. Interestingly, most...

Influence of Load Modes on Voltage Stability of Receiving Network at DC/AC System

Directory of Open Access Journals (Sweden)

Mao Chizu

2016-01-01

Full Text Available This paper analyses influence of load modes on DC/AC system. Because of widespread use of HVDC, DC/AC system become more complex than before and the present modes used in dispatch and planning departments are not fit in simulation anymore. So it is necessary to find load modes accurately reflecting characteristics of the system. For the sake of the voltage stability, commutation failure, etc. the practical example of the receiving network in a large DC/AC system in China is simulated with BPA, and the influence of Classical Load Mode (CLM and Synthesis load model (SLM on simulation results is studies. Furthermore, some important parameters of SLM are varied respectively among an interval to analyse how they affect the system. According to this practical examples, the result is closely related to load modes and their parameters, and SLM is more conservative but more reasonable than the present modes. The consequences indicate that at critical states, micro variation in parameters may give rise to change in simulation results radically. Thus, correct mode and parameters are important to enhance simulation accuracy of DC/AC system and researches on how they affect the system make senses.

A model for voltage collapse study considering load characteristics

Energy Technology Data Exchange (ETDEWEB)

Aguiar, L B [Companhia de Energia Eletrica da Bahia (COELBA), Salvador, BA (Brazil)

1994-12-31

This paper presents a model for analysis of voltage collapse and instability problem considering the load characteristics. The model considers fundamentally the transmission lines represented by exact from through the generalized constants A, B, C, D and the loads as function of the voltage, emphasizing the cases of constant power, constant current and constant impedance. the study treats of the system behavior on steady state and presents illustrative graphics about the problem. (author) 12 refs., 4 figs.

Short-Term State Forecasting-Based Optimal Voltage Regulation in Distribution Systems: Preprint

Energy Technology Data Exchange (ETDEWEB)

Yang, Rui; Jiang, Huaiguang; Zhang, Yingchen

2017-05-17

A novel short-term state forecasting-based optimal power flow (OPF) approach for distribution system voltage regulation is proposed in this paper. An extreme learning machine (ELM) based state forecaster is developed to accurately predict system states (voltage magnitudes and angles) in the near future. Based on the forecast system states, a dynamically weighted three-phase AC OPF problem is formulated to minimize the voltage violations with higher penalization on buses which are forecast to have higher voltage violations in the near future. By solving the proposed OPF problem, the controllable resources in the system are optimally coordinated to alleviate the potential severe voltage violations and improve the overall voltage profile. The proposed approach has been tested in a 12-bus distribution system and simulation results are presented to demonstrate the performance of the proposed approach.

Effects of oxidation potential and retention time on electrochromic stability of poly (3-hexyl thiophene) films

Science.gov (United States)

Kim, Tae-Ho; Hyun Song, Seok; Kim, Hyo-Jae; Oh, Seong-Hyeon; Han, Song-Yi; Kim, Goung; Nah, Yoon-Chae

2018-06-01

Herein, we report the effects of applied voltage on the electrochromic (EC) stability of poly(3-hexylthiophene) (P3HT) films during EC reactions. The transmittance difference and cycling stability of these films were monitored to optimize the oxidation voltage, and their chemical compositions were analyzed by X-ray photoelectron spectroscopy after long-term electrochemical cycling. High oxidation voltages increased the color contrast of P3HT films but decreased their cycling stability due to facilitating chemical degradation. Furthermore, at an optimized oxidation voltage, the retention time during potential pulsing was adjusted utilizing the optical memory of P3HT, revealing that the decreased voltage application time reduced power consumption by 9.6% and enhanced EC stability without loss of color contrast.

New Requirements of the Voltage/VAR Function for Smart Inverter in Distributed Generation Control

Directory of Open Access Journals (Sweden)

Yun-Su Kim

2016-11-01

Full Text Available International Electronical Committee (IEC 61850-90-7 is a part of the IEC 61850 series which specifies the advanced functions and object models for power converter based Distributed Energy Resources (DERs. One of its functions, the Voltage/VAR (V/V control function, is used to enhance the stability and the reliability of the voltage in the distribution system. The conventional V/V function acts mainly for flattening the voltage profile as for a basic grid support function. Currently, other objectives such as the minimization of line loss and the operational costs reduction are coming into the spotlight. In order to attain these objectives, the V/V function and hence the DER units shall actively respond to the change of distribution system conditions. In this paper, the modification of V/V function and new requirements are proposed. To derive new requirements of V/V function, loss minimization is applied to a particle swarm optimization (PSO algorithm where the condition of voltage constraint is considered not to deteriorate the voltage stability of the distribution system.

Precise generator of stability amplitude pulses

International Nuclear Information System (INIS)

Zhuk, N.A.; Zdesenko, Yu.G.; Kuts, V.N.

1989-01-01

A generator of stability amplitude pulses, designed for stabilization of a low-noise semiconducting spectrometer, used in investigations of 76 Ge2β-decay, is described. The generator contains a permanent-voltage source, a storage element and a switch based on a Hg relay. A thermostatic source provides a relative voltage instability less than ±5x10 -6 per 80h (standard deviation). The Hg relay is placed into a separate thermostat. The relative instability of output generator pulse amplitude does not exceed ±1.5x10 -5 per 24h

Dependence of stability of metastable superconductors on copper fraction

International Nuclear Information System (INIS)

Elrod, S.A.; Lue, J.W.; Miller, J.R.; Dresner, L.

1980-12-01

The stability of composite superconductors operating in the metastable regime depends upon such factors as matrix resistivity, cooled surface dimensions, fraction of critical current, and volume fraction of stabilizer. By assuming constant thermophysical properties, we developed analytic expressions for the energy and voltage of the minimum propagating zone (MPZ). With other factors held constant, these expressions have been used to predict composite superconductor stability as a function of copper fraction: lower copper fractions lead to higher MPZ energies. MPZ voltages have been measured for three NbTi/Cu composites having different copper fractions and different critical current densities for several magnetic fields and transport currents. Experimental MPZ voltages have been used to calculate an effective heat transfer coefficient, which is subsequently used to calculate the MPZ energy. The experimental MPZ energies support the theoretical expectation that lower copper fractions lead to higher stability in the metastable regime

CONTRIBUTIONS OF INTRACELLULAR IONS TO Kv CHANNEL VOLTAGE SENSOR DYNAMICS.

Directory of Open Access Journals (Sweden)

Samuel eGoodchild

2012-06-01

Full Text Available Voltage sensing domains of Kv channels control ionic conductance through coupling of the movement of charged residues in the S4 segment to conformational changes at the cytoplasmic region of the pore domain, that allow K+ ions to flow. Conformational transitions within the voltage sensing domain caused by changes in the applied voltage across the membrane field are coupled to the conducting pore region and the gating of ionic conductance. However, several other factors not directly linked to the voltage dependent movement of charged residues within the voltage sensor impact the dynamics of the voltage sensor, such as inactivation, ionic conductance, intracellular ion identity and block of the channel by intracellular ligands. The effect of intracellular ions on voltage sensor dynamics is of importance in the interpretation of gating current measurements and the physiology of pore/voltage sensor coupling. There is a significant amount of variability in the reported kinetics of voltage sensor deactivation kinetics of Kv channels attributed to different mechanisms such as open state stabilization, immobilization and relaxation processes of the voltage sensor. Here we separate these factors and focus on the causal role that intracellular ions can play in allosterically modulating the dynamics of Kv voltage sensor deactivation kinetics. These considerations are of critical importance in understanding the molecular determinants of the complete channel gating cycle from activation to deactivation.

Voltage Scheduling Droop Control for State-of-Charge Balance of Distributed Energy Storage in DC Microgrids

DEFF Research Database (Denmark)

Li, Chendan; Dragicevic, Tomislav; Aldana, Nelson Leonardo Diaz

2014-01-01

Due to higher power quality, lower conversion loss, and more DC loads, there has been an increasing awareness on DC microgrid. Previous emphasis has been on equal power sharing among different units in the DC microgrid, while overlooking the coordination of the energy storage units to maintain...... the State-of-Charge balance. In this paper, a new droop method based on voltage scheduling for State-of-Charge balance is proposed to keep the SoC balance for the energy storage units. The proposed method has the advantage of avoiding the stability problem existed in traditional methods based on droop gain...... scheduling. Simulation experiment is taken in Matlab on a DC microgrid with two distributed energy storage units. The simulation results show that the proposed method has successfully achieved SoC balance during the load changes while maintaining the DC bus voltage within the allowable range....

Controlled phase stability of highly Na-active triclinic structure in nanoscale high-voltage Na2-2xCo1+xP2O7 cathode for Na-ion batteries

Science.gov (United States)

Song, Hee Jo; Kim, Jae-Chan; Dar, Mushtaq Ahmad; Kim, Dong-Wan

2018-02-01

With the increasing demand for high energy density in energy-storage systems, a high-voltage cathode is essential in rechargeable Li-ion and Na-ion batteries. The operating voltage of a triclinic-polymorph Na2CoP2O7, also known as the rose form, is above 4.0 V (vs. Na/Na+), which is relatively high compared to that of other cathode materials. Thus, it can be employed as a potential high-voltage cathode material in Na-ion batteries. However, it is difficult to synthesize a pure rose phase because of its low phase stability, thus limiting its use in high-voltage applications. Herein, compositional-engineered, rose-phase Na2-2xCo1+xP2O7/C (x = 0, 0.1 and 0.2) nanopowder are prepared using a wet-chemical method. The Na2-2xCo1+xP2O7/C cathode shows high electrochemical reactivity with Na ions at 4.0 V, delivering high capacity and high energy density.

Physicochemical assessment criteria for high-voltage pulse capacitors

Energy Technology Data Exchange (ETDEWEB)

Darian, L. A., E-mail: LDarian@rambler.ru; Lam, L. Kh. [National Research University, Moscow Power Engineering Institute (Russian Federation)

2016-12-15

In the paper, the applicability of decomposition products of internal insulation of high-voltage pulse capacitors is considered (aging is the reason for decomposition products of internal insulation). Decomposition products of internal insulation of high-voltage pulse capacitors can be used to evaluate their quality when in operation and in service. There have been three generations of markers of aging of insulation as in the case with power transformers. The area of applicability of markers of aging of insulation for power transformers has been studied and the area can be extended to high-voltage pulse capacitors. The research reveals that there is a correlation between the components and quantities of markers of aging of the first generation (gaseous decomposition products of insulation) dissolved in insulating liquid and the remaining life of high-voltage pulse capacitors. The application of markers of aging to evaluate the remaining service life of high-voltage pulse capacitor is a promising direction of research, because the design of high-voltage pulse capacitors keeps stability of markers of aging of insulation in high-voltage pulse capacitors. It is necessary to continue gathering statistical data concerning development of markers of aging of the first generation. One should also carry out research aimed at estimation of the remaining life of capacitors using markers of the second and the third generation.

Physicochemical assessment criteria for high-voltage pulse capacitors

International Nuclear Information System (INIS)

Darian, L. A.; Lam, L. Kh.

2016-01-01

In the paper, the applicability of decomposition products of internal insulation of high-voltage pulse capacitors is considered (aging is the reason for decomposition products of internal insulation). Decomposition products of internal insulation of high-voltage pulse capacitors can be used to evaluate their quality when in operation and in service. There have been three generations of markers of aging of insulation as in the case with power transformers. The area of applicability of markers of aging of insulation for power transformers has been studied and the area can be extended to high-voltage pulse capacitors. The research reveals that there is a correlation between the components and quantities of markers of aging of the first generation (gaseous decomposition products of insulation) dissolved in insulating liquid and the remaining life of high-voltage pulse capacitors. The application of markers of aging to evaluate the remaining service life of high-voltage pulse capacitor is a promising direction of research, because the design of high-voltage pulse capacitors keeps stability of markers of aging of insulation in high-voltage pulse capacitors. It is necessary to continue gathering statistical data concerning development of markers of aging of the first generation. One should also carry out research aimed at estimation of the remaining life of capacitors using markers of the second and the third generation.

Modeling, analysis, and design of stationary reference frame droop controlled parallel three-phase voltage source inverters

DEFF Research Database (Denmark)

Vasquez, Juan Carlos; Guerrero, Josep M.; Savaghebi, Mehdi

2013-01-01

Power electronics based MicroGrids consist of a number of voltage source inverters (VSIs) operating in parallel. In this paper, the modeling, control design, and stability analysis of parallel connected three-phase VSIs are derived. The proposed voltage and current inner control loops and the mat......Power electronics based MicroGrids consist of a number of voltage source inverters (VSIs) operating in parallel. In this paper, the modeling, control design, and stability analysis of parallel connected three-phase VSIs are derived. The proposed voltage and current inner control loops...... control restores the frequency and amplitude deviations produced by the primary control. Also, a synchronization algorithm is presented in order to connect the MicroGrid to the grid. Experimental results are provided to validate the performance and robustness of the parallel VSI system control...

The development of long pulse high voltage power supply for MNI-1U neutral beam injector

International Nuclear Information System (INIS)

Detai Wang

1989-01-01

A high power long pulse high voltage power supply (HVPS) for MNI- 1 U neutral beam injector (NBI) is described. This HVPS is used as a switching regulator with a duty cycle of 1/100, the specifications of circuit are as follows, output pulse voltage 50kv, pulse current 30A, pulse width 50ms, rise-time and fall-time of the voltage are less than 25 μs, stability of the pulse flat is better than 0.5%, regulation response time of the pulse voltage less than 30 μs can be attained. It is also used as a stable DC HVPS, output voltage is 1 to 100kv, current is 1 to 5A. If regulation tube is shunted with high power resistor in parallel, the current can be extended to 10 A, stability of the output voltage or current is better than 0.1%. Now, the HVPS has been put into operation for MNI- 1 U NBI and PIG ion source made in French. 3 refs., 5 figs

Transient stability improvement by nonlinear controllers based on tracking

Energy Technology Data Exchange (ETDEWEB)

Ramirez, Juan M. [Centro de Investigacion y Estudios Avanzados, Guadalajara, Mexico. Av. Cientifica 1145. Col. El Bajio. Zapopan, Jal. 45015 (Mexico); Arroyave, Felipe Valencia; Correa Gutierrez, Rosa Elvira [Universidad Nacional de Colombia, Sede Medellin. Facultad de Minas, Escuela de Mecatronica (Colombia)

2011-02-15

This paper deals with the control problem in multi-machine electric power systems, which represent complex great scale nonlinear systems. Thus, the controller design is a challenging problem. These systems are subjected to different perturbations, such as short circuits, connection and/or disconnection of loads, lines, or generators. Then, the utilization of controllers which guarantee good performance under those perturbations is required in order to provide electrical energy to the loads with admissible stability margins. The proposed controllers are based on a systematic strategy, which calculate nonlinear controllers for generating units in a power plant, both for voltage and velocity regulation. The formulation allows designing controllers in a multi-machine power system without intricate calculations. Results on a power system of the open research indicate the proposition's suitability. The problem is formulated as a tracking problem. The designed controllers may be implemented in any electric power system. (author)

A new method for compensation of the effect of charging transformer's leakage inductance on PFN voltage regulation in Klystron pulse modulators

Energy Technology Data Exchange (ETDEWEB)

Patel, Akhil, E-mail: akhilpatel@rrcat.gov.in; Kale, Umesh; Shrivastava, Purushottam

2017-04-21

The Line type modulators have been widely used to generate high voltage rectangular pulses to power the klystron for high power RF generation. In Line type modulator, the Pulse Forming Network (PFN) which is a cascade combination of lumped capacitors and inductors is used to store the electrical energy. The charged PFN is then discharged into a klystron by firing a high voltage Thyratron switch. This discharge generates a high voltage rectangular pulse across the klystron electrodes. The amplitude and phase of Klystron's RF output is governed by the high voltage pulse amplitude. The undesired RF amplitude and phase stability issues arises at the klystron's output due to inter-pulse and during the pulse amplitude variations. To reduce inter-pulse voltage variations, the PFN is required to be charged at the same voltage after every discharge cycle. At present, the combination of widely used resonant charging and deQing method is used to regulate the pulse to pulse PFN voltage variations but the charging transformer's leakage inductance puts an upper bound on the regulation achievable by this method. Here we have developed few insights of the deQing process and devised a new compensation method to compensate this undesired effect of charging transformer's leakage inductance on the pulse to pulse PFN voltage stability. This compensation is accomplished by the controlled partial discharging of the split PFN capacitor using a low voltage MOSFET switch. Theoretically, very high values of pulse to pulse voltage stability may be achieved using this method. This method may be used in deQing based existing modulators or in new modulators, to increase the pulse to pulse voltage stability, without having a very tight bound on charging transformer's leakage inductance. Given a stable charging power supply, this method may be used to further enhance the inter-pulse voltage stability of modulators which employ the direct charging, after replacing the

An optical fiber Bragg grating and piezoelectric ceramic voltage sensor

Science.gov (United States)

Yang, Qing; He, Yanxiao; Sun, Shangpeng; Luo, Mandan; Han, Rui

2017-10-01

Voltage measurement is essential in many fields like power grids, telecommunications, metallurgy, railways, and oil production. A voltage-sensing unit, consisting of fiber Bragg gratings (FBGs) and piezoelectric ceramics, based on which an optical over-voltage sensor was proposed and fabricated in this paper. No demodulation devices like spectrometer or Fabry-Perot filter were needed to gain the voltage signal, and a relatively large sensing frequency range was acquired in this paper; thus, the cost of the sensing system is more acceptable in engineering application. The voltage to be measured was directly applied to the piezoelectric ceramic, and deformation of the ceramics and the grating would be caused because of the inverse piezoelectric effect. With a reference grating, the output light intensity change will be caused by the FBG center wavelength change; thus, the relationship between the applied voltage and the output light intensity was established. Validation of the sensor was accomplished in the frequency range from 50 Hz to 20 kHz and switching impulse waves with a test platform; good linearity of the input-output characteristic was achieved. A temperature validation test was completed, showing that the sensor maintains good temperature stability. Experimental results show that the optical over-voltage sensor can be used for voltage monitoring, and if applied with a voltage divider, the sensor can be used to measure high voltage.

An optical fiber Bragg grating and piezoelectric ceramic voltage sensor.

Science.gov (United States)

Yang, Qing; He, Yanxiao; Sun, Shangpeng; Luo, Mandan; Han, Rui

2017-10-01

Voltage measurement is essential in many fields like power grids, telecommunications, metallurgy, railways, and oil production. A voltage-sensing unit, consisting of fiber Bragg gratings (FBGs) and piezoelectric ceramics, based on which an optical over-voltage sensor was proposed and fabricated in this paper. No demodulation devices like spectrometer or Fabry-Perot filter were needed to gain the voltage signal, and a relatively large sensing frequency range was acquired in this paper; thus, the cost of the sensing system is more acceptable in engineering application. The voltage to be measured was directly applied to the piezoelectric ceramic, and deformation of the ceramics and the grating would be caused because of the inverse piezoelectric effect. With a reference grating, the output light intensity change will be caused by the FBG center wavelength change; thus, the relationship between the applied voltage and the output light intensity was established. Validation of the sensor was accomplished in the frequency range from 50 Hz to 20 kHz and switching impulse waves with a test platform; good linearity of the input-output characteristic was achieved. A temperature validation test was completed, showing that the sensor maintains good temperature stability. Experimental results show that the optical over-voltage sensor can be used for voltage monitoring, and if applied with a voltage divider, the sensor can be used to measure high voltage.

Comparison of two voltage control strategies for a wind power plant

DEFF Research Database (Denmark)

Martinez, Jorge; Kjær, Philip C.; Rodriguez, Pedro

2011-01-01

plants. This paper addresses the analysis of two different voltage control strategies for a wind power plant, i.e. decentralized and centralized voltage control schemes. The analysis has been performed using the equivalent and simplified transfer functions of the system. Using this representation......Larger percentages of wind power penetration translate to more demanding requirements from grid codes. Recently, voltage support at the point of connection has been introduced by several grid codes from around the world, thus, making it important to analyze this control when applied to wind power......, it is possible to investigate the influence of the plant control gain, short circuit ratio, and time delays on the system stability, as well as the fulfillment of the design requirements. The implemented plant voltage control is based on a slope voltage controller, which calculates the references to be sent...

Ionization smoke detectors - the high-voltage issues

International Nuclear Information System (INIS)

Anon.

1992-01-01

Production of high-voltage ionization smoke detectors ceased in 1978 following the development of lower voltage models which used much smaller amounts of radioactive material. Despite this fact, thousands of high-voltage detectors are still in use today in many large UK companies. The major users argue that there is no reason to stop using their detectors if they are still fit for their purpose - many could last for another 15 to 20 years if properly maintained. But pressure has been mounting on businesses to replace all their high-voltage detectors with new low-voltage models within the next couple of years. This could place a huge financial burden on the companies concerned, with costs possibly running into millions of pounds. Traditionally, the major detector installers offered cleaning and maintenance services for high-voltage detectors to their customers but these have now been withdrawn. The installers give no clear reasons for this decision except that the detectors are outmoded and should be disposed of as soon as possible. Most users would agree that conversion to low-voltage types is inevitable but their main worry is the financial strain of replacing all their detectors - and associated equipment - in one go. They would prefer to phase out their high-voltage detectors in stages over a number of years to spread the costs of conversion. The problems of maintenance is discussed. A dual voltage fire alarm panel which allows the high-voltage detectors to be phased out is mentioned. (Author)

Application of Multipoint DC Voltage Control in VSC-MTDC System

Directory of Open Access Journals (Sweden)

Yang Xi

2013-01-01

Full Text Available The voltage-source-converter- (VSC- based multiterminal VSC-HVDC power transmission system (VSC-MTDC is an ideal approach to connect wind farm with power grid. Analyzing the characteristics of doubly fed induction generators as well as the basic principle and the control strategy of VSC-MTDC, a multiterminal DC voltage control strategy suitable for wind farm connected with VSC-MTDC is proposed. By use of PSCAD/EMTDC, the proposed control strategy is simulated, and simulation results show that using the proposed control strategy the conversion between constant power control mode and constant DC voltage control mode can be automatically implemented; thus the DC voltage stability control and reliable power output of wind farm can be ensured after the fault-caused outage of converter station controlled by constant DC voltage and under other faults. The simulation result shows that the model can fulfill multiterminal power transmission and fast response control.

Cavity Voltage Phase Modulation MD blocks 3 and 4

CERN Document Server

Mastoridis, T; Butterworth, A; Molendijk, J; Tuckmantel, J

2013-01-01

The LHC RF/LLRF system is currently setup for extremely stable RF voltage to minimize transient beam loading effects. The present scheme cannot be extended beyond nominal beam current since the demanded power would push the klystrons to saturation. For beam currents above nominal (and possibly earlier), the cavity phase modulation by the beam (transient beam loading) will not be corrected, but the strong RF feedback and One-Turn Delay feedback will still be active for RF loop and beam stability in physics. To achieve this, the voltage set point should be adapted for each bunch. The goal of these MDs was to test thefirmware version of an iterative algorithm that adjusts the voltage set point to achieve the optimal phase modulation for klystron forward power considerations.

Neutron flux stabilization in the NG-150 neutron generators

International Nuclear Information System (INIS)

Kuz'min, L.E.; Makarov, S.A.; Pronman, I.M.

1986-01-01

Problem of metal tritium target lifetime increase and neutron flux stabilization in the NG-150 neutron generators is studied. Possibility on neutron flux stabilization using the mass analyzer for low-angle (4 deg and 41 deg) mass separation of a beam in thre components, which fall on a target simultaneously, is confirmed experimentally. Basic generator parameters are: accelerating voltage of 150 kV, total beam current on a target of 1.5 mA, beam current density of 0.3-1.6 mA/cm 2 , beam diameter of 8 mm. The initial neutron flux on the targets of 0.73 mg/cm 2 thick constituted 1.1x10 11 ssup(-1). The neutron flux monitoring was accomplished from recoil proton recording by a plastic scintillator. Flux decrease by more than 5% served as a signel for measuring mass analyzer magnetic field providing beam displacement on a target and restoration of the given flux. The NG-150 generator neutron flux stabilization was attained during 2h

Legendre condition and the stabilization problem for classical soliton solutions in generalized Skyrme models

International Nuclear Information System (INIS)

Kiknadze, N.A.; Khelashvili, A.A.

1990-01-01

The problem on stability of classical soliton solutions is studied from the unique point of view: the Legendre condition - necessary condition of existence of weak local minimum for energy functional (term soliton is used here in the wide sense) is used. Limits to parameters of the model Lagrangians are obtained; it is shown that there is no soliton stabilization in some of them despite the phenomenological achievements. The Jacoby sufficient condition is discussed

Operational stability of a compact 600-W KrF laser

International Nuclear Information System (INIS)

Borisov, V M; Vinokhodov, A Yu; Vodchits, V A; El'tsov, A V; Basting, D; Stamm, U; Voss, F

1998-01-01

The problem of the operational stability of a KrF laser with an average output power of at least 600 W was investigated. An experimental study was made of the dependences of the rms deviation σ of the output energy on the charging voltage, on the pulse repetition rate, and on the operating time. The value of σ varied from 1.2% to 6.0%, depending on the experimental conditions. For an average power of ∼ 600 W, the deviation σ did not exceed 3.2%. (lasers and amplifiers)

Selective virtual capacitive impedance loop for harmonics voltage compensation in islanded microgrids

DEFF Research Database (Denmark)

Micallef, Alexander; Apap, Maurice; Spiteri-Staines, Cyril

2013-01-01

Parallel inverters having LCL output filters cause voltage distortions at the point of common coupling (PCC) in islanded microgrids when non-linear loads are present. A capacitive virtual impedance loop could be used to provide selective harmonic compensation in islanded microgrids, instead of in...... resistance for selective harmonic compensation in islanded microgrids. Simulation results were given to show the suitability of the proposed algorithms in reducing the voltage harmonics at the PCC.......Parallel inverters having LCL output filters cause voltage distortions at the point of common coupling (PCC) in islanded microgrids when non-linear loads are present. A capacitive virtual impedance loop could be used to provide selective harmonic compensation in islanded microgrids, instead...... of introducing additional active or passive filters into the system that could compromise the stability of the microgrid. However, the performance of these compensation loops becomes degraded when a virtual resistance is introduced with the aim to improve the overall stability of the parallel inverters...

Gambling Problem Symptom Patterns and Stability across Individual and Timeframe

DEFF Research Database (Denmark)

Nelson, Sarah; Josefsen, Line Gebauer; LaBrie, Richard

2009-01-01

Few studies investigate gambling problems at the symptom level; even fewer investigate how symptom patterns change throughout the course of a gambling disorder. The current study utilized the National Epidemiological Survey on Alcohol and Related Conditions (NESARC; Grant et al., 2004) to investi...... of progression to PG among participants at-risk for PG. The differential diagnostic value of various reported symptoms, as well as their lack of stability, has implications for both researchers and clinicians. 2009 APA, all rights reserved....

Large Signal Stabilization of Hybrid AC/DC Micro-Grids Using Nonlinear Robust Controller

Directory of Open Access Journals (Sweden)

Reza Pejmanfar

2017-12-01

Full Text Available This paper presents a robust nonlinear integrated controller to improve stability of hybrid AC/DC micro-grids under islanding mode. The proposed controller includes two independent controllers where each one is responsible to control one part of the system. First controller will improve the stability of input DC/DC converter. Using this controller, the voltage of DC bus is fully stabilized such that when a large disturbance occurs, its voltage will become constant without any significant dynamic. The necessity of DC bus regulation which has not been considered in previous studies, is imminent as it not only improves voltage stability of the micro-grid but also protects consumers which are directly connected to the DC bus, against voltage variations. Frequency stability of the micro-grid is provided by the second proposed controller which is applied to output DC/AC converter of the micro-grid. Adaptive method is used to make the controllers proposed in this paper, robust. Duty cycle of converters switches are adjusted such that voltage and frequency of the micro-grid are set on the desired value in minimum possible time under transient disturbances and uncertainty of the loads as well as micro-sources characteristics.

Control voltage and power fluctuations when connecting wind farms

Science.gov (United States)

Berinde, Ioan; Bǎlan, Horia; Oros Pop, Teodora Susana

2015-12-01

Voltage, frequency, active power and reactive power are very important parameters in terms of power quality. These parameters are followed when connecting any power plant, the more the connection of wind farms. Connecting wind farms to the electricity system must not cause interference outside the limits set by regulations. Modern solutions for fast and automatic voltage control and power fluctuations using electronic control systems of reactive power flows. FACTS (Flexible Alternating Current Transmision System) systems, established on the basis of power electronic circuits ensure control of electrical status quantities to achieve the necessary transfer of power to the power grid. FACTS devices can quickly control parameters and sizes of state power lines, such as impedance line voltages and phase angles of the voltages of the two ends of the line. Their use can lead to improvement in power system operation by increasing the transmission capacity of power lines, power flow control lines, improved static and transient stability reserve.

Control voltage and power fluctuations when connecting wind farms

International Nuclear Information System (INIS)

Berinde, Ioan; Bălan, Horia; Oros, Teodora Susana

2015-01-01

Voltage, frequency, active power and reactive power are very important parameters in terms of power quality. These parameters are followed when connecting any power plant, the more the connection of wind farms. Connecting wind farms to the electricity system must not cause interference outside the limits set by regulations. Modern solutions for fast and automatic voltage control and power fluctuations using electronic control systems of reactive power flows. FACTS (Flexible Alternating Current Transmision System) systems, established on the basis of power electronic circuits ensure control of electrical status quantities to achieve the necessary transfer of power to the power grid. FACTS devices can quickly control parameters and sizes of state power lines, such as impedance line voltages and phase angles of the voltages of the two ends of the line. Their use can lead to improvement in power system operation by increasing the transmission capacity of power lines, power flow control lines, improved static and transient stability reserve

Control voltage and power fluctuations when connecting wind farms

Energy Technology Data Exchange (ETDEWEB)

Berinde, Ioan, E-mail: ioan-berinde@yahoo.com; Bălan, Horia, E-mail: hbalan@mail.utcluj.ro; Oros, Teodora Susana, E-mail: teodoraoros-87@yahoo.com [Technical University of Cluj-Napoca, Romania, Faculty of Electrical Engineering, Department of Power Engineering and Management (Romania)

2015-12-23

Voltage, frequency, active power and reactive power are very important parameters in terms of power quality. These parameters are followed when connecting any power plant, the more the connection of wind farms. Connecting wind farms to the electricity system must not cause interference outside the limits set by regulations. Modern solutions for fast and automatic voltage control and power fluctuations using electronic control systems of reactive power flows. FACTS (Flexible Alternating Current Transmision System) systems, established on the basis of power electronic circuits ensure control of electrical status quantities to achieve the necessary transfer of power to the power grid. FACTS devices can quickly control parameters and sizes of state power lines, such as impedance line voltages and phase angles of the voltages of the two ends of the line. Their use can lead to improvement in power system operation by increasing the transmission capacity of power lines, power flow control lines, improved static and transient stability reserve.

Application of a Modal Approach in Solving the Static Stability Problem for Electric Power Systems

Science.gov (United States)

Sharov, J. V.

2017-12-01

Application of a modal approach in solving the static stability problem for power systems is examined. It is proposed to use the matrix exponent norm as a generalized transition function of the power system disturbed motion. Based on the concept of a stability radius and the pseudospectrum of Jacobian matrix, the necessary and sufficient conditions for existence of the static margins were determined. The capabilities and advantages of the modal approach in designing centralized or distributed control and the prospects for the analysis of nonlinear oscillations and rendering the dynamic stability are demonstrated.

Reliable and Low-Voltage Electrowetting on Thin Parylene Films

NARCIS (Netherlands)

Dhindsa, M.S.; Kuiper, S.; Kumar, R.; Heikenfeld, J.

2011-01-01

The stability of an electrowetting system is dependent upon the choice of liquids, the dielectric material and the operating voltage.Substantial progress is reported herein on use of 300 nm thick poly-tetrafluoro-para-xylylene) (Parylene HT) films for almost 100° of reliable electrowetting

Thermal instability and current-voltage scaling in superconducting fault current limiters

Energy Technology Data Exchange (ETDEWEB)

Zeimetz, B [Department of Materials Science and Metallurgy, Cambridge University, Pembroke Street, Cambridge CB1 3QZ (United Kingdom); Tadinada, K [Department of Engineering, Cambridge University, Trumpington Road, Cambridge CB2 1PZ (United Kingdom); Eves, D E [Department of Engineering, Cambridge University, Trumpington Road, Cambridge CB2 1PZ (United Kingdom); Coombs, T A [Department of Engineering, Cambridge University, Trumpington Road, Cambridge CB2 1PZ (United Kingdom); Evetts, J E [Department of Materials Science and Metallurgy, Cambridge University, Pembroke Street, Cambridge CB1 3QZ (United Kingdom); Campbell, A M [Department of Engineering, Cambridge University, Trumpington Road, Cambridge CB2 1PZ (United Kingdom)

2004-04-01

We have developed a computer model for the simulation of resistive superconducting fault current limiters in three dimensions. The program calculates the electromagnetic and thermal response of a superconductor to a time-dependent overload voltage, with different possible cooling conditions for the surfaces, and locally variable superconducting and thermal properties. We find that the cryogen boil-off parameters critically influence the stability of a limiter. The recovery time after a fault increases strongly with thickness. Above a critical thickness, the temperature is unstable even for a small applied AC voltage. The maximum voltage and maximum current during a short fault are correlated by a simple exponential law.

METHOD FOR STABILIZING KLYSTRONS

Science.gov (United States)

Magnuson, D.W.; Smith, D.F.

1959-04-14

High-frequency oscillators for the generation of microwaves, particularly a system for stabilizing frequency-modulated klystron oscillators of the reflex type, are described. The system takos advantage of the fact that a change in oscillator frequency will alter the normal phase displacement between the cavity and its modulator, creating an error voltage which is utilized to regulate the frequency of the oscillator and stabilize it.

DFIG turbine representation for small signal voltage control studies

DEFF Research Database (Denmark)

Garcia, Jorge Martinez; Kjær, Philip Carne; Teodorescu, Remus

2010-01-01

This paper addresses the representation of a wind power plant, based on wound rotor asynchronous generators, with a centralized voltage controller, by an equivalent transfer function, valid for small signal voltage control studies. This representation allows to investigate the influence...... introduced recently by several grid codes from around the world, making important to analyze this control when applied to wind power plants. The performance of the equivalent transfer function has been evaluated and compared using an equivalent grid with different short circuit ratios and active power...... of the centralized plant control gain and short circuit ratio on the system stability, for instance, by analyzing the zero-pole placement. Larger percentages of wind power penetration translate to more demanding requirements coming from the grid codes, for example voltage support at the point of connection has been...

Grid Integration of Offshore Wind Farms via VSC-HVDC – Dynamic Stability Study

DEFF Research Database (Denmark)

Liu, Hongzhi

farms could seriously impact the operation and stability of their interconnected power system. To assist in maintaining the power system stability when large disturbances occur in the grid, modern offshore wind farms consisting of variable-speed wind turbines are required to provide ancillary services...... such as voltage and frequency control. The greater distance to shore makes commonly used high voltage AC (HVAC) connection unsuitable economically and technically for large offshore wind farms. Alternatively, voltage source converter (VSC)-based high voltage DC (HVDC) transmission becomes more attractive...... and practical to integrate large-scale offshore wind farms into the onshore power grid, owing to its high capacity, advanced controllability and stabilization potential for AC networks etc. In this dissertation, some of the key technical issues with grid integration of large-scale offshore wind farms via VSC...

Stability of stationary solutions for inflow problem on the micropolar fluid model

Science.gov (United States)

Yin, Haiyan

2017-04-01

In this paper, we study the asymptotic behavior of solutions to the initial boundary value problem for the micropolar fluid model in a half-line R+:=(0,∞). We prove that the corresponding stationary solutions of the small amplitude to the inflow problem for the micropolar fluid model are time asymptotically stable under small H1 perturbations in both the subsonic and degenerate cases. The microrotation velocity brings us some additional troubles compared with Navier-Stokes equations in the absence of the microrotation velocity. The proof of asymptotic stability is based on the basic energy method.

Stability, Optimality and Manipulation in Matching Problems with Weighted Preferences

Directory of Open Access Journals (Sweden)

Maria Silvia Pini

2013-11-01

Full Text Available The stable matching problem (also known as the stable marriage problem is a well-known problem of matching men to women, so that no man and woman, who are not married to each other, both prefer each other. Such a problem has a wide variety of practical applications, ranging from matching resident doctors to hospitals, to matching students to schools or, more generally, to any two-sided market. In the classical stable marriage problem, both men and women express a strict preference order over the members of the other sex, in a qualitative way. Here, we consider stable marriage problems with weighted preferences: each man (resp., woman provides a score for each woman (resp., man. Such problems are more expressive than the classical stable marriage problems. Moreover, in some real-life situations, it is more natural to express scores (to model, for example, profits or costs rather than a qualitative preference ordering. In this context, we define new notions of stability and optimality, and we provide algorithms to find marriages that are stable and/or optimal according to these notions. While expressivity greatly increases by adopting weighted preferences, we show that, in most cases, the desired solutions can be found by adapting existing algorithms for the classical stable marriage problem. We also consider the manipulability properties of the procedures that return such stable marriages. While we know that all procedures are manipulable by modifying the preference lists or by truncating them, here, we consider if manipulation can occur also by just modifying the weights while preserving the ordering and avoiding truncation. It turns out that, by adding weights, in some cases, we may increase the possibility of manipulating, and this cannot be avoided by any reasonable restriction on the weights.

High-frequency high-voltage high-power DC-to-DC converters

Science.gov (United States)

Wilson, T. G.; Owen, H. A.; Wilson, P. M.

1982-09-01

A simple analysis of the current and voltage waveshapes associated with the power transistor and the power diode in an example current-or-voltage step-up (buck-boost) converter is presented. The purpose of the analysis is to provide an overview of the problems and design trade-offs which must be addressed as high-power high-voltage converters are operated at switching frequencies in the range of 100 kHz and beyond. Although the analysis focuses on the current-or-voltage step-up converter as the vehicle for discussion, the basic principles presented are applicable to other converter topologies as well.

High-voltage transistor converter for pulsed x-ray sources

International Nuclear Information System (INIS)

Krasil'nikov, S.B.; Kristalinskii, A.L.; Lozovoi, L.N.; Markov, S.N.; Sindalovskii, E.I.

1986-01-01

A 24-V/12-kV converter for MIRA-2D and NORA pulsed x-ray sources is described. When the low-voltage supply varies within 20-26 V, the frequency stability of the x-ray pulses is higher by a factor of 3 ≅ 3 than when the PRIMA converter is used. For 14-24 V, the average output power of the converter is independent of the load impedance and increases linearly with an increase in supply voltage. The efficiency of the converter reaches 60%. The converter operates in the temperature range of -40 to +60 0 C

Influence of Distributed Residential Energy Storage on Voltage in Rural Distribution Network and Capacity Configuration

Science.gov (United States)

Liu, Lu; Tong, Yibin; Zhao, Zhigang; Zhang, Xuefen

2018-03-01

Large-scale access of distributed residential photovoltaic (PV) in rural areas has solved the voltage problem to a certain extent. However, due to the intermittency of PV and the particularity of rural residents’ power load, the problem of low voltage in the evening peak remains to be resolved. This paper proposes to solve the problem by accessing residential energy storage. Firstly, the influence of access location and capacity of energy storage on voltage distribution in rural distribution network is analyzed. Secondly, the relation between the storage capacity and load capacity is deduced for four typical load and energy storage cases when the voltage deviation meets the demand. Finally, the optimal storage position and capacity are obtained by using PSO and power flow simulation.

An implantable neurostimulator with an integrated high-voltage inductive power-recovery frontend

International Nuclear Information System (INIS)

Wang Yuan; Zhang Xu; Liu Ming; Li Peng; Chen Hongda

2014-01-01

This paper present a highly-integrated neurostimulator with an on-chip inductive power-recovery frontend and high-voltage stimulus generator. In particular, the power-recovery frontend includes a high-voltage full-wave rectifier (up to 100 V AC input), high-voltage series regulators (24/5 V outputs) and a linear regulator (1.8/3.3 V output) with bandgap voltage reference. With the high voltage output of the series regulator, the proposed neurostimulator could deliver a considerably large current in high electrode-tissue contact impedance. This neurostimulator has been fabricated in a CSMC 1 μm 5/40/700 V BCD process and the total silicon area including pads is 5.8 mm 2 . Preliminary tests are successful as the neurostimulator shows good stability under a 13.56 MHz AC supply. Compared to previously reported works, our design has advantages of a wide induced voltage range (26–100 V), high output voltage (up to 24 V) and high-level integration, which are suitable for implantable neurostimulators. (semiconductor integrated circuits)

Incentive-Based Voltage Regulation in Distribution Networks

Energy Technology Data Exchange (ETDEWEB)

Dall-Anese, Emiliano [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Baker, Kyri A [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Zhou, Xinyang [University of Colorado; Chen, Lijun [University of Colorado

2017-07-03

This paper considers distribution networks fea- turing distributed energy resources, and designs incentive-based mechanisms that allow the network operator and end-customers to pursue given operational and economic objectives, while concurrently ensuring that voltages are within prescribed limits. Two different network-customer coordination mechanisms that require different amounts of information shared between the network operator and end-customers are developed to identify a solution of a well-defined social-welfare maximization prob- lem. Notably, the signals broadcast by the network operator assume the connotation of prices/incentives that induce the end- customers to adjust the generated/consumed powers in order to avoid the violation of the voltage constraints. Stability of the proposed schemes is analytically established and numerically corroborated.

Modeling and simulation of dynamic voltage restorer in power system

International Nuclear Information System (INIS)

Abdel Aziz, M.A.A.M.

2012-01-01

There are many loads subjected to several Power Quality Problems such as voltage sags/swells, unbalance, harmonics distortion, and short interruption. These loads encompass a wide range of equipment which are very sensitive to voltage disturbances. The Dynamic Voltage Restorer (DVR) has recently been introduced to protect sensitive loads from voltage sags and other voltage disturbances in addition to this, it mitigates current harmonics distortion. It is a series connected power electronic based device. It is considered as one of the most efficient and effective solutions. Its appeal includes smaller size and fast dynamic response to disturbances. This work describes a proposal of the DVR to improve power quality distribution (medium voltage) system. The control of the compensation voltage and harmonics cancellation in the DVR is based on Adaptive Noise Canceling (ANC) technique. Simulation results carried out by PSCAD/EMTDC to investigate the performance of the proposed method.

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.

Numerical Study on Several Stabilized Finite Element Methods for the Steady Incompressible Flow Problem with Damping

Directory of Open Access Journals (Sweden)

Jilian Wu

2013-01-01

Full Text Available We discuss several stabilized finite element methods, which are penalty, regular, multiscale enrichment, and local Gauss integration method, for the steady incompressible flow problem with damping based on the lowest equal-order finite element space pair. Then we give the numerical comparisons between them in three numerical examples which show that the local Gauss integration method has good stability, efficiency, and accuracy properties and it is better than the others for the steady incompressible flow problem with damping on the whole. However, to our surprise, the regular method spends less CPU-time and has better accuracy properties by using Crout solver.

Current regulator for stabilizing electrostatic generators; Regulateur de courant pour stabilisation de generateur electrostatique

Energy Technology Data Exchange (ETDEWEB)

Gabet, A; Taieb, J

1950-07-01

An instrument consisting of two electronic tubes, a triode and a pentode, connected in series, serves as a stabilizer of the current that charges a working model of a van de Graaff generator. The current is maintained at a level corresponding to an auxiliary variable voltage. The triode maintains that voltage, while the pentode regulates the current. Another application of the circuit, viz., the stabilizing of the generator voltage, will be described elsewhere. (author)

A Voltage Instability Predictor Using Local Area Measurements. VIP++

Energy Technology Data Exchange (ETDEWEB)

Warland, Leif

2002-07-01

There has been a pressure to operate power systems closer to their security limits. This has partially been due to financial imperatives following the deregulating of markets. Other practical difficulties have been obtaining authorization from regulatory bodies to build power plants and transmission lines. In this situation it is essential to monitor the system and to have tools that can predict the distance to the point of collapse (PoC). Much effort has been put into research of the phenomenon voltage collapse, and many approaches have been explored. Both dynamic and steady-state behavior have been studied thoroughly, though very few protection and control schemes have been implemented. In this dissertation the possibility of an index based on local area measurements have been explored. Voltage stability can be classified as either a transient or a long-term stability problem, and the index proposed in this dissertation is based on long-term dynamics. The VIP algorithm is a method that uses the maximum load ability of a transmission network as the PoC, thus by estimating a Thevenin equivalent the method can track the distance to the PoC as this occurs when the two impedances are equal in absolute value. The problem of the VIP algorithm is that it is based on a system with two equations and four unknowns, thus it is not observable. In order to make it observable the assumption of constant Thevenin equivalent between two sets of measurements is made. When this is not the case the method will estimate a Thevenin impedance of the same size as the measured load impedance, but with a negative sign. Changes in the Thevenin equivalent can be traced to both angle variation in a remote generator area or to variations in load impedances on nearby buses. The problem of angle variations can be mitigated by the selection of an appropriate reference bus. A method to solve the second problem, of variation in load admittances, has been proposed in this dissertation and given the

Voltage regulation in MV networks with dispersed generations by a neural-based multiobjective methodology

Energy Technology Data Exchange (ETDEWEB)

Galdi, Vincenzo [Dipartimento di Ingegneria dell' Informazione e Ingegneria Elettrica, Universita degli studi di Salerno, Via Ponte Don Melillo 1, 84084 Fisciano (Italy); Vaccaro, Alfredo; Villacci, Domenico [Dipartimento di Ingegneria, Universita degli Studi del Sannio, Piazza Roma 21, 82100 Benevento (Italy)

2008-05-15

This paper puts forward the role of learning techniques in addressing the problem of an efficient and optimal centralized voltage control in distribution networks equipped with dispersed generation systems (DGSs). The proposed methodology employs a radial basis function network (RBFN) to identify the multidimensional nonlinear mapping between a vector of observable variables describing the network operating point and the optimal set points of the voltage regulating devices. The RBFN is trained by numerical data generated by solving the voltage regulation problem for a set of network operating points by a rigorous multiobjective solution methodology. The RBFN performance is continuously monitored by a supervisor process that notifies when there is the need of a more accurate solution of the voltage regulation problem if nonoptimal network operating conditions (ex post monitoring) or excessive distances between the actual network state and the neuron's centres (ex ante monitoring) are detected. A more rigorous problem solution, if required, can be obtained by solving the voltage regulation problem by a conventional multiobjective optimization technique. This new solution, in conjunction with the corresponding input vector, is then adopted as a new train data sample to adapt the RBFN. This online training process allows RBFN to (i) adaptively learn the more representative domain space regions of the input/output mapping without needing a prior knowledge of a complete and representative training set, and (ii) manage effectively any time varying phenomena affecting this mapping. The results obtained by simulating the regulation policy in the case of a medium-voltage network are very promising. (author)

Flexible Compensation of Voltage and Current Unbalance and Harmonics in Microgrids

Directory of Open Access Journals (Sweden)

Seyyed Yousef Mousazadeh Mousavi

2017-10-01

Full Text Available In recent years, the harmonics and unbalance problems endanger the voltage and current quality of power systems, due to increasing usage of nonlinear and unbalanced loads. Use of Distributed Generation (DG-interfacing inverters is proposed for voltage or current compensation. In this paper, a flexible control method is proposed to compensate voltage and current unbalance and harmonics using the distributed generation (DG-interfacing inverters. This method is applicable to both grid-connected and islanded Microgrids (MGs. In the proposed method, not only the proper control of active and reactive powers can be achieved, but also there is flexibility in compensating the voltage or current quality problems at DG terminals or Points of Common Coupling (PCCs. This control strategy consists of active and reactive power controllers and a voltage/current quality-improvement block. The controller is designed in a stationary (αβ frame. An extensive simulation study has been performed and the results demonstrate the effectiveness of the proposed control scheme. Depending on the compensation modes, the harmonics and unbalance compensation of DG output current, MG-injected current to the grid, as well as PCC and DG voltages, can be achieved in grid-connected operation of MG while in the islanded operation, and the PCC and DG voltages compensation can be obtained through the proposed control scheme.

Power supply and stabilization of the supply system on board using decentralized voltage rectifiers

Energy Technology Data Exchange (ETDEWEB)

Grueb, W; Wegerer, K

1987-04-01

The functionally redundant power supply system of the Transrapid 06 II maglev train is described; it comprises four independent, battery-buffered networks and 30 linear generators per train section. Voltage rectifiers adapt the velocity- and load-dependent linear generator voltage to the 440 V d.c. networks and assure dynamic stabilisation as well as buffer battery loading. The result is a high-reliability power supply system on board with optimum utilisation of the power supplied by the linear generators while the train is running.

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...

Synchrophasor-Assisted Prediction of Stability/Instability of a Power System

Science.gov (United States)

Saha Roy, Biman Kumar; Sinha, Avinash Kumar; Pradhan, Ashok Kumar

2013-05-01

This paper presents a technique for real-time prediction of stability/instability of a power system based on synchrophasor measurements obtained from phasor measurement units (PMUs) at generator buses. For stability assessment the technique makes use of system severity indices developed using bus voltage magnitude obtained from PMUs and generator electrical power. Generator power is computed using system information and PMU information like voltage and current phasors obtained from PMU. System stability/instability is predicted when the indices exceeds a threshold value. A case study is carried out on New England 10-generator, 39-bus system to validate the performance of the technique.

Simple economical stabilizer for electromagnet field

International Nuclear Information System (INIS)

Vas'kov, O.S.; Domanevskij, D.S.; Zinkevich, Yu.V.; Soroka, E.V.; Shavel', N.N.

1988-01-01

Field stabilizer within high-power electromagnet gap at direct current up to 75 A and up to 100 V voltage in the winding is described. 15 parallel-connected KT 945A transistors, operation mode of which allows to do without radiators and forced cooling are used as controlling element of pulsed stabilizer

Automatic Voltage Control (AVC) System under Uncertainty from Wind Power

DEFF Research Database (Denmark)

Qin, Nan; Abildgaard, Hans; Flynn, Damian

2016-01-01

An automatic voltage control (AVC) system maintains the voltage profile of a power system in an acceptable range and minimizes the operational cost by coordinating the regulation of controllable components. Typically, all of the parameters in the optimization problem are assumed to be certain...... and constant in the decision making process. However, for high shares of wind power, uncertainty in the decision process due to wind power variability may result in an infeasible AVC solution. This paper proposes a voltage control approach which considers the voltage uncertainty from wind power productions....... The proposed method improves the performance and the robustness of a scenario based approach by estimating the potential voltage variations due to fluctuating wind power production, and introduces a voltage margin to protect the decision against uncertainty for each scenario. The effectiveness of the proposed...

Parallel Optimization of Polynomials for Large-scale Problems in Stability and Control

Science.gov (United States)

Kamyar, Reza

In this thesis, we focus on some of the NP-hard problems in control theory. Thanks to the converse Lyapunov theory, these problems can often be modeled as optimization over polynomials. To avoid the problem of intractability, we establish a trade off between accuracy and complexity. In particular, we develop a sequence of tractable optimization problems --- in the form of Linear Programs (LPs) and/or Semi-Definite Programs (SDPs) --- whose solutions converge to the exact solution of the NP-hard problem. However, the computational and memory complexity of these LPs and SDPs grow exponentially with the progress of the sequence - meaning that improving the accuracy of the solutions requires solving SDPs with tens of thousands of decision variables and constraints. Setting up and solving such problems is a significant challenge. The existing optimization algorithms and software are only designed to use desktop computers or small cluster computers --- machines which do not have sufficient memory for solving such large SDPs. Moreover, the speed-up of these algorithms does not scale beyond dozens of processors. This in fact is the reason we seek parallel algorithms for setting-up and solving large SDPs on large cluster- and/or super-computers. We propose parallel algorithms for stability analysis of two classes of systems: 1) Linear systems with a large number of uncertain parameters; 2) Nonlinear systems defined by polynomial vector fields. First, we develop a distributed parallel algorithm which applies Polya's and/or Handelman's theorems to some variants of parameter-dependent Lyapunov inequalities with parameters defined over the standard simplex. The result is a sequence of SDPs which possess a block-diagonal structure. We then develop a parallel SDP solver which exploits this structure in order to map the computation, memory and communication to a distributed parallel environment. Numerical tests on a supercomputer demonstrate the ability of the algorithm to

Voltage and frequency control of wind-powered islanded microgrids based on induction generator and STATCOM

DEFF Research Database (Denmark)

Bouzid, Allal; Sicard, Pierre; Guerrero, Josep M.

2015-01-01

This paper presents a comprehensive modeling of a three-phase cage induction machine used as a self-excited squirrel-cage induction generator (SEIG), and discusses the regulation of the voltage and frequency of a self-excited SEIG based on the action of the static synchronous Compensator (STATCOM......). The STATCOM with the proposed controller consists of a three-phase voltage-sourced inverter and a DC voltage. The compensator can provide the active and reactive powers and regulate AC system bus voltage and the frequency, but also may enhance the load stability. Moreover, a feed forward control method...

Reactive power and voltage control strategy based on dynamic and adaptive segment for DG inverter

Science.gov (United States)

Zhai, Jianwei; Lin, Xiaoming; Zhang, Yongjun

2018-03-01

The inverter of distributed generation (DG) can support reactive power to help solve the problem of out-of-limit voltage in active distribution network (ADN). Therefore, a reactive voltage control strategy based on dynamic and adaptive segment for DG inverter is put forward to actively control voltage in this paper. The proposed strategy adjusts the segmented voltage threshold of Q(U) droop curve dynamically and adaptively according to the voltage of grid-connected point and the power direction of adjacent downstream line. And then the reactive power reference of DG inverter can be got through modified Q(U) control strategy. The reactive power of inverter is controlled to trace the reference value. The proposed control strategy can not only control the local voltage of grid-connected point but also help to maintain voltage within qualified range considering the terminal voltage of distribution feeder and the reactive support for adjacent downstream DG. The scheme using the proposed strategy is compared with the scheme without the reactive support of DG inverter and the scheme using the Q(U) control strategy with constant segmented voltage threshold. The simulation results suggest that the proposed method has a significant improvement on solving the problem of out-of-limit voltage, restraining voltage variation and improving voltage quality.

Voltage-regulating constant-current sources in a linear induction accelerator

International Nuclear Information System (INIS)

Zhao Juan; Cao Kefeng; Deng Jianjun; Zhu Lijun; Yang Jia; Ye Chao; Huang Bin; Cao Ningxiang; Dong Jinxuan; Zhang Jichang; Yu Zhiguo; Chen Min

2002-01-01

Constant-current Sources are one of key units in a linear induction accelerator. The requirements for the sources are to supply stable direct current of high power for the induction coil, be easy to computer-control and highly stable and reliable. Applying the technique of linear current source regulating in series, the primary voltage of the power transformer is regulated through an MJYS-JL-350A type three-phase alterative voltage-regulating module. The output current variation is 300-500 A when the load variation is 0.06-0.1 Ω and the voltage drop of the regulator tube is controlled within 8 V±2V when the variation of mains voltage is in ±10%. Both the current ripple and stability meet the technical requirements. The constant-current sources are controlled through an industrial controller. For each of the constant-current sources has a smallest system comprised of 8051 which is communication-controlled through a RS-485 interface, the sources can be controlled remotely

Development of Electromechanical Architectures for AC Voltage Metrology

Directory of Open Access Journals (Sweden)

Alexandre BOUNOUH

2010-12-01

Full Text Available This paper presents results of work undertaken for exploring MEMS capabilities to fabricate AC voltage references for electrical metrology and high precision instrumentation through the mechanical-electrical coupling in MEMS. From first MEMS test structures previously realized, a second set of devices with improved characteristics has been developed and fabricated with Silicon on Insulator (SOI Surface Micromachining process. These MEMS exhibit pull-in voltages of 5 V and 10 V to match with the best performance of the read-out electronics developed for driving the MEMS. Deep Level Transient Spectroscopy measurements carried out on the new design show resonance frequencies of about only some kHz, and the stability of the MEMS output voltage measured at 100 kHz has been found very promising for the best samples where the relative deviation from the mean value over almost 12 hours showed a standard deviation of about 6.3 ppm.

A new VME-based high voltage power supply for large photomultiplier systems

International Nuclear Information System (INIS)

Neumaier, S.; Hubbeling, T.; Kolb, B.W.; Purschke, M.L.; Ippolitov, M.; Blume, C.; Bohne, E.M.; Bucher, D.; Claussen, A.; Peitzmann, T.; Schepers, G.; Schlagheck, H.

1995-01-01

We describe a new high voltage power supply, developed for the leadglass calorimeter of the WA98 experiment at CERN. The high voltage is produced for each of the 10,080 photomultiplier tubes of the detector individually, by the same number of active bases with on-board Greinacher voltage multipliers. The full VME-based HV controller system, which addresses each base via bus cables once per second, is miniaturized and fits into a single VME crate. The main advantages of this approach are the low heat dissipation, the considerably reduced amount of cabling and cost, as well as the high stability and low noise of the system. (orig.)

Effects of Electrode Material on the Voltage of a Tree-Based Energy Generator.

Science.gov (United States)

Hao, Zhibin; Wang, Guozhu; Li, Wenbin; Zhang, Junguo; Kan, Jiangming

2015-01-01

The voltage between a standing tree and its surrounding soil is regarded as an innovative renewable energy source. This source is expected to provide a new power generation system for the low-power electrical equipment used in forestry. However, the voltage is weak, which has caused great difficulty in application. Consequently, the development of a method to increase the voltage is a key issue that must be addressed in this area of applied research. As the front-end component for energy harvesting, a metal electrode has a material effect on the level and stability of the voltage obtained. This study aimed to preliminarily ascertain the rules and mechanisms that underlie the effects of electrode material on voltage. Electrodes of different materials were used to measure the tree-source voltage, and the data were employed in a comparative analysis. The results indicate that the conductivity of the metal electrode significantly affects the contact resistance of the electrode-soil and electrode-trunk contact surfaces, thereby influencing the voltage level. The metal reactivity of the electrode has no significant effect on the voltage. However, passivation of the electrode materials markedly reduces the voltage. Suitable electrode materials are demonstrated and recommended.

Low-Cost Voltage Zero-Crossing Detector for AC-Grid Applications

Directory of Open Access Journals (Sweden)

Vorobyov Maxim

2014-10-01

Full Text Available Renewable energy sources and energy storage devices are becoming more popular. Some of them like small hydropower turbines, wind turbines and diesel generators produce AC voltage with different frequency and voltage than the main grid. For them power electronics converters are necessary. Power electronics converters presented in industry use two or three level energy conversion, although direct AC to AC converters exist, but one of the main problems is the switch commutation when current or voltage is crossing the zero point. Zero crossing sensors are used to solve this problem. They consist of current or voltage measurement unit and zero crossing detector. Different approaches are used for zero crossing: hardware or software. Hardware approach is simple but it has low precision. Software approach has high precision but it is complicated and expensive. In this paper a simple low cost high precision approach is presented. It takes all advantages from both approaches. While tested with two types of microcontrollers the precision of experimental measurement is 25 μs - 40 μs.

Design of high voltage power supply of miniature X-ray tube based on resonant Royer

International Nuclear Information System (INIS)

Liu Xiyao; Zeng Guoqiang; Tan Chengjun; Luo Qun; Gong Chunhui; Huang Rui

2013-01-01

Background: In recent years, X rays are widely used in various fields. With the rapid development of national economy, the demand of high quality, high reliability, and high stability miniature X-ray tube has grown rapidly. As an important core component of miniature X-ray tube, high voltage power supply has attracted wide attention. Purpose: To match miniature, the high voltage power supply should be small, lightweight, good quality, etc. Based on the basic performance requirements of existing micro-X-ray tube high voltage power supply, this paper designs an output from 0 to -30 kV adjustable miniature X-ray tube voltage DC power supply. Compared to half-bridge and full-bridge switching-mode power supply, its driving circuit is simple. With working on the linear condition, it has no switching noise. Methods: The main circuit makes use of DC power supply to provide the energy. The resonant Royer circuit supplies sine wave which drives to the high frequency transformer's primary winding with resultant sine-like high voltage appearing across the secondary winding. Then, the voltage doubling rectifying circuit would achieve further boost. In the regulator circuit, a feedback control resonant transistor base current is adopted. In order to insulate air, a silicone rubber is used for high pressure part packaging, and the output voltage is measured by the dividing voltage below -5 kV. Results: The stability of circuit is better than 0.2%/6 h and the percent of the output ripple voltage is less than 0.3%. Keeping the output voltage constant, the output current can reach 57 μA by changing the size of load resistor. This high voltage power supply based on resonant Royer can meet the requirement of miniature X-ray tube. Conclusions: The circuit can satisfy low noise, low ripple, low power and high voltage regulator power supply design. However, its efficiency is not high enough because of the linear condition. In the next design, to further reduce power consumption, we

Time varying voltage combustion control and diagnostics sensor

Science.gov (United States)

Chorpening, Benjamin T [Morgantown, WV; Thornton, Jimmy D [Morgantown, WV; Huckaby, E David [Morgantown, WV; Fincham, William [Fairmont, WV

2011-04-19

A time-varying voltage is applied to an electrode, or a pair of electrodes, of a sensor installed in a fuel nozzle disposed adjacent the combustion zone of a continuous combustion system, such as of the gas turbine engine type. The time-varying voltage induces a time-varying current in the flame which is measured and used to determine flame capacitance using AC electrical circuit analysis. Flame capacitance is used to accurately determine the position of the flame from the sensor and the fuel/air ratio. The fuel and/or air flow rate (s) is/are then adjusted to provide reduced flame instability problems such as flashback, combustion dynamics and lean blowout, as well as reduced emissions. The time-varying voltage may be an alternating voltage and the time-varying current may be an alternating current.

Lyapunov vs. geometrical stability analysis of the Kepler and the restricted three body problems

International Nuclear Information System (INIS)

Yahalom, A.; Levitan, J.; Lewkowicz, M.; Horwitz, L.

2011-01-01

In this Letter we show that although the application of standard Lyapunov analysis predicts that completely integrable Kepler motion is unstable, the geometrical analysis of Horwitz et al. predicts the observed stability. This seems to us to provide evidence for both the incompleteness of the standard Lyapunov analysis and the strength of the geometrical analysis. Moreover, we apply this approach to the three body problem in which the third body is restricted to move on a circle of large radius which induces an adiabatic time dependent potential on the second body. This causes the second body to move in a very interesting and intricate but periodic trajectory; however, the standard Lyapunov analysis, as well as methods based on the parametric variation of curvature associated with the Jacobi metric, incorrectly predict chaotic behavior. The geometric approach predicts the correct stable motion in this case as well. - Highlights: → Lyapunov analysis predicts Kepler motion to be unstable. → Geometrical analysis predicts the observed stability. → Lyapunov analysis predicts chaotic behavior in restricted three body problem. → The geometric approach predicts the correct stable motion in restricted three body problem.

250 kV 6 mA compact Cockcroft-Walton high-voltage power supply

Energy Technology Data Exchange (ETDEWEB)

Ma, Zhan-Wen; Su, Xiao-Dong; Wei, Zhen; Huang, Zhi-Wu; Miao, Tian-You; Su, Tong-Ling [School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China); Lu, Xiao-Long; Wang, Jun-Run; Yao, Ze-En, E-mail: zeyao@lzu.edu.cn [School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China); Engineering Research Center for Neutron Application, Ministry of Education, Lanzhou University, Lanzhou 730000 (China)

2016-08-15

A compact power supply system for a compact neutron generator has been developed. A 4-stage symmetrical Cockcroft-Walton circuit is adopted to produce 250 kV direct current high-voltage. A 2-stage 280 kV isolation transformer system is used to drive the ion source power supply. For a compact structure, safety, and reliability during the operation, the Cockcroft-Walton circuit and the isolation transformer system are enclosed in an epoxy vessel containing the transformer oil whose size is about ∅350 mm × 766 mm. Test results indicate that the maximum output voltage of the power supply is 282 kV, and the stability of the output voltage is better than 0.63% when the high voltage power supply is operated at 250 kV, 6.9 mA with the input voltage varying ±10%.

Assessing Power System Stability Following Load Changes and Considering Uncertainty

Directory of Open Access Journals (Sweden)

D. V. Ngo

2018-04-01

Full Text Available An increase in load capacity during the operation of a power system usually causes voltage drop and leads to system instability, so it is necessary to monitor the effect of load changes. This article presents a method of assessing the power system stability according to the load node capacity considering uncertainty factors in the system. The proposed approach can be applied to large-scale power systems for voltage stability assessment in real-time.

SVPWM Technique with Varying DC-Link Voltage for Common Mode Voltage Reduction in a Matrix Converter and Analytical Estimation of its Output Voltage Distortion

Science.gov (United States)

Padhee, Varsha

Common Mode Voltage (CMV) in any power converter has been the major contributor to premature motor failures, bearing deterioration, shaft voltage build up and electromagnetic interference. Intelligent control methods like Space Vector Pulse Width Modulation (SVPWM) techniques provide immense potential and flexibility to reduce CMV, thereby targeting all the afore mentioned problems. Other solutions like passive filters, shielded cables and EMI filters add to the volume and cost metrics of the entire system. Smart SVPWM techniques therefore, come with a very important advantage of being an economical solution. This thesis discusses a modified space vector technique applied to an Indirect Matrix Converter (IMC) which results in the reduction of common mode voltages and other advanced features. The conventional indirect space vector pulse-width modulation (SVPWM) method of controlling matrix converters involves the usage of two adjacent active vectors and one zero vector for both rectifying and inverting stages of the converter. By suitable selection of space vectors, the rectifying stage of the matrix converter can generate different levels of virtual DC-link voltage. This capability can be exploited for operation of the converter in different ranges of modulation indices for varying machine speeds. This results in lower common mode voltage and improves the harmonic spectrum of the output voltage, without increasing the number of switching transitions as compared to conventional modulation. To summarize it can be said that the responsibility of formulating output voltages with a particular magnitude and frequency has been transferred solely to the rectifying stage of the IMC. Estimation of degree of distortion in the three phase output voltage is another facet discussed in this thesis. An understanding of the SVPWM technique and the switching sequence of the space vectors in detail gives the potential to estimate the RMS value of the switched output voltage of any

Decision Optimization for Power Grid Operating Conditions with High- and Low-Voltage Parallel Loops

Directory of Open Access Journals (Sweden)

Dong Yang

2017-05-01

Full Text Available With the development of higher-voltage power grids, the high- and low-voltage parallel loops are emerging, which lead to energy losses and even threaten the security and stability of power systems. The multi-infeed high-voltage direct current (HVDC configurations widely appearing in AC/DC interconnected power systems make this situation even worse. Aimed at energy saving and system security, a decision optimization method for power grid operating conditions with high- and low-voltage parallel loops is proposed in this paper. Firstly, considering hub substation distribution and power grid structure, parallel loop opening schemes are generated with GN (Girvan-Newman algorithms. Then, candidate opening schemes are preliminarily selected from all these generated schemes based on a filtering index. Finally, with the influence on power system security, stability and operation economy in consideration, an evaluation model for candidate opening schemes is founded based on analytic hierarchy process (AHP. And a fuzzy evaluation algorithm is used to find the optimal scheme. Simulation results of a New England 39-bus system and an actual power system validate the effectiveness and superiority of this proposed method.

Voltage Profile Enhancement and Reduction of Real Power loss by Hybrid Biogeography Based Artificial Bee Colony algorithm

Directory of Open Access Journals (Sweden)

K. Lenin

2014-04-01

Full Text Available This paper presents Hybrid Biogeography algorithm for solving the multi-objective reactive power dispatch problem in a power system. Real Power Loss minimization and maximization of voltage stability margin are taken as the objectives. Artificial bee colony optimization (ABC is quick and forceful algorithm for global optimization. Biogeography-Based Optimization (BBO is a new-fangled biogeography inspired algorithm. It mainly utilizes the biogeography-based relocation operator to share the information among solutions. In this work, a hybrid algorithm with BBO and ABC is projected, and named as HBBABC (Hybrid Biogeography based Artificial Bee Colony Optimization, for the universal numerical optimization problem. HBBABC merge the searching behavior of ABC with that of BBO. Both the algorithms have different solution probing tendency like ABC have good exploration probing tendency while BBO have good exploitation probing tendency.  HBBABC used to solve the reactive power dispatch problem and the proposed technique has been tested in standard IEEE30 bus test system.

Assessment of voltage dips based on field measurements in MV networks

NARCIS (Netherlands)

Weldemariam, L.E.; Papathanasiou, F.; Cuk, V.; Cobben, J.F.G.; Kling, W.L.

Voltage dip is considered as the PQ problem related to the highest financial losses for the customers. It occurs unpredictably mainly due to short-circuit faults in the networks. Network operators and customers want to know more about the occurrence and the potential impact of voltage dips. PQ

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.

Structure of Voltage-gated Two-pore Channel TPC1 from Arabidopsis thaliana

Science.gov (United States)

Guo, Jiangtao; Zeng, Weizhong; Chen, Qingfeng; Lee, Changkeun; Chen, Liping; Yang, Yi; Cang, Chunlei; Ren, Dejian; Jiang, Youxing

2015-01-01

Two-pore channels (TPCs) contain two copies of a Shaker-like six-transmembrane (6-TM) domain in each subunit and are ubiquitously expressed in both animals and plants as organellar cation channels. Here, we present the first crystal structure of a vacuolar two-pore channel from Arabidopsis thaliana, AtTPC1, which functions as a homodimer. AtTPC1 activation requires both voltage and cytosolic Ca2+. Ca2+ binding to the cytosolic EF-hand domain triggers conformational changes coupled to the pair of pore-lining inner helices (IS6 helices) from the first 6-TM domains, whereas membrane potential only activates the second voltage-sensing domain (VSD2) whose conformational changes are coupled to the pair of inner helices (IIS6 helices) from the second 6-TM domains. Luminal Ca2+ or Ba2+ can modulate voltage activation by stabilizing VSD2 in the resting state and shifts voltage activation towards more positive potentials. Our Ba2+ bound AtTPC1 structure reveals a voltage sensor in the resting state, providing hitherto unseen structural insight into the general voltage-gating mechanism among voltage-gated channels. PMID:26689363

H∞ Robust Current Control for DFIG Based Wind Turbine subject to Grid Voltage Distortions

DEFF Research Database (Denmark)

Wang, Yun; Wu, Qiuwei; Gong, Wenming

2016-01-01

This paper proposes an H∞ robust current controller for doubly fed induction generator (DFIG) based wind turbines (WTs) subject to grid voltage distortions. The controller is to mitigate the impact of the grid voltage distortions on rotor currents with DFIG parameter perturbation. The grid voltage...... distortions considered include asymmetric voltage dips and grid background harmonics. An uncertain DFIG model is developed with uncertain factors originating from distorted stator voltage, and changed generator parameters due to the flux saturation effect, the skin effect, etc. Weighting functions...... are designed to efficiently track the unbalanced current components and the 5th and 7th background harmonics. The robust stability (RS) and robust performance (RP) of the proposed controller are verified by the structured singular value µ. The performance of the H∞ robust current controller was demonstrated...

Stability of transition to a world without nuclear weapons: Technical problems of verification

International Nuclear Information System (INIS)

Zhigalov, V.

1998-01-01

A serious psychological barrier to acceptance of the concept for achieving the nuclear-weapon-free world is fear of facing the prospect that one or more nations or extremist political groups might develop their own nuclear weapons. Actually this is a question of stability of the nuclear-weapon-free world. From this point of view the most effective system of verification is an absolute necessity. This system must ensure detection of so called undeclared nuclear activity at early stage. Scientists of Russian nuclear centers are working today on solving this problem. This paper is considered to be a comprehensive attempt to analyze the technical and organizational aspects of the problems of transition to a nuclear-weapons-free world, setting aside the difficulties of resolving purely political problems

Suppressing voltage transients in high voltage power supplies

International Nuclear Information System (INIS)

Lickel, K.F.; Stonebank, R.

1979-01-01

A high voltage power supply for an X-ray tubes includes voltage adjusting means, a high voltage transformer, switch means connected to make and interrupt the primary current of the transformer, and over-voltage suppression means to suppress the voltage transient produced when the current is switched on. In order to reduce the power losses in the suppression means, an impedance is connected in the transformer primary circuit on operation of the switch means and is subsequently short-circuited by a switch controlled by a timer after a period which is automatically adjusted to the duration of the transient overvoltage. (U.K.)

Methods of solving of the optimal stabilization problem for stationary smooth control systems. Part I

Directory of Open Access Journals (Sweden)

G. Kondrat'ev

1999-10-01

Full Text Available In this article some ideas of Hamilton mechanics and differential-algebraic Geometry are used to exact definition of the potential function (Bellman-Lyapunov function in the optimal stabilization problem of smooth finite-dimensional systems.

Voltage control on a train system

Science.gov (United States)

Gordon, Susanna P.; Evans, John A.

2004-01-20

The present invention provides methods for preventing low train voltages and managing interference, thereby improving the efficiency, reliability, and passenger comfort associated with commuter trains. An algorithm implementing neural network technology is used to predict low voltages before they occur. Once voltages are predicted, then multiple trains can be controlled to prevent low voltage events. Further, algorithms for managing inference are presented in the present invention. Different types of interference problems are addressed in the present invention such as "Interference During Acceleration", "Interference Near Station Stops", and "Interference During Delay Recovery." Managing such interference avoids unnecessary brake/acceleration cycles during acceleration, immediately before station stops, and after substantial delays. Algorithms are demonstrated to avoid oscillatory brake/acceleration cycles due to interference and to smooth the trajectories of closely following trains. This is achieved by maintaining sufficient following distances to avoid unnecessary braking/accelerating. These methods generate smooth train trajectories, making for a more comfortable ride, and improve train motor reliability by avoiding unnecessary mode-changes between propulsion and braking. These algorithms can also have a favorable impact on traction power system requirements and energy consumption.

Evaluation of Voltage Control Approaches for Future Smart Distribution Networks

Directory of Open Access Journals (Sweden)

Pengfei Wang

2017-08-01

Full Text Available This paper evaluates meta-heuristic and deterministic approaches for distribution network voltage control. As part of this evaluation, a novel meta-heuristic algorithm, Cuckoo Search, is applied for distribution network voltage control and compared with a deterministic voltage control algorithm, the oriented discrete coordinate decent method (ODCDM. ODCDM has been adopted in a state-of-the-art industrial product and applied in real distribution networks. These two algorithms have been evaluated under a set of test cases, which were generated to represent the voltage control problems in current and future distribution networks. Sampled test results have been presented, and findings have been discussed regarding the adoption of different optimization algorithms for current and future distribution networks.

Discrete-Time Domain Modelling of Voltage Source Inverters in Standalone Applications

DEFF Research Database (Denmark)

Federico, de Bosio; de Sousa Ribeiro, Luiz Antonio; Freijedo Fernandez, Francisco Daniel

2017-01-01

modelling of the LC plant with consideration of delay and sample-and-hold effects on the state feedback cross-coupling decoupling is derived. From this plant formulation, current controllers with wide bandwidth and good relative stability properties are developed. Two controllers based on lead compensation......The decoupling of the capacitor voltage and inductor current has been shown to improve significantly the dynamic performance of voltage source inverters in standalone applications. However, the computation and PWM delays still limit the achievable bandwidth. In this paper a discrete-time domain...

Posterior consistency for Bayesian inverse problems through stability and regression results

International Nuclear Information System (INIS)

Vollmer, Sebastian J

2013-01-01

In the Bayesian approach, the a priori knowledge about the input of a mathematical model is described via a probability measure. The joint distribution of the unknown input and the data is then conditioned, using Bayes’ formula, giving rise to the posterior distribution on the unknown input. In this setting we prove posterior consistency for nonlinear inverse problems: a sequence of data is considered, with diminishing fluctuations around a single truth and it is then of interest to show that the resulting sequence of posterior measures arising from this sequence of data concentrates around the truth used to generate the data. Posterior consistency justifies the use of the Bayesian approach very much in the same way as error bounds and convergence results for regularization techniques do. As a guiding example, we consider the inverse problem of reconstructing the diffusion coefficient from noisy observations of the solution to an elliptic PDE in divergence form. This problem is approached by splitting the forward operator into the underlying continuum model and a simpler observation operator based on the output of the model. In general, these splittings allow us to conclude posterior consistency provided a deterministic stability result for the underlying inverse problem and a posterior consistency result for the Bayesian regression problem with the push-forward prior. Moreover, we prove posterior consistency for the Bayesian regression problem based on the regularity, the tail behaviour and the small ball probabilities of the prior. (paper)

On increasing stability in the two dimensional inverse source scattering problem with many frequencies

Science.gov (United States)

Entekhabi, Mozhgan Nora; Isakov, Victor

2018-05-01

In this paper, we will study the increasing stability in the inverse source problem for the Helmholtz equation in the plane when the source term is assumed to be compactly supported in a bounded domain Ω with a sufficiently smooth boundary. Using the Fourier transform in the frequency domain, bounds for the Hankel functions and for scattering solutions in the complex plane, improving bounds for the analytic continuation, and the exact observability for the wave equation led us to our goals which are a sharp uniqueness and increasing stability estimate when the wave number interval is growing.

Study on Control Scheme for the Inverters in Low Voltage Microgrid with Nonlinear Loads

Science.gov (United States)

Xu, Jiqiang; Lu, Wenzhou; Wu, Lei

2017-05-01

There are a lot of nonlinear loads in real low voltage microgrid system. It will cause serious output voltage and grid current harmonic distortions problems in island and grid-connected modes, respectively. To solve this problem, this paper proposes a droop control scheme with quasi-proportion and resonant (quasi-PR) controller based on αβ stationary reference frame to make microgrid smoothly switch between grid-connected and island modes without changing control method. Moreover, in island mode, not only stable output voltage and frequency, but also reduced output voltage harmonics with added nonlinear loads can be achieved; In grid-connected mode, not only constant power, but also reduced grid current harmonics can be achieved. Simulation results verify the effectiveness of the proposed control scheme.

Incentive-Based Voltage Regulation in Distribution Networks: Preprint

Energy Technology Data Exchange (ETDEWEB)

Zhou, Xinyang; Chen, Lijun; Dall' Anese, Emiliano; Baker, Kyri

2017-03-03

This paper considers distribution networks fea- turing distributed energy resources, and designs incentive-based mechanisms that allow the network operator and end-customers to pursue given operational and economic objectives, while concurrently ensuring that voltages are within prescribed limits. Two different network-customer coordination mechanisms that require different amounts of information shared between the network operator and end-customers are developed to identify a solution of a well-defined social-welfare maximization prob- lem. Notably, the signals broadcast by the network operator assume the connotation of prices/incentives that induce the end- customers to adjust the generated/consumed powers in order to avoid the violation of the voltage constraints. Stability of the proposed schemes is analytically established and numerically corroborated.

Voltage scheduling for low power/energy

Science.gov (United States)

Manzak, Ali

2001-07-01

Power considerations have become an increasingly dominant factor in the design of both portable and desk-top systems. An effective way to reduce power consumption is to lower the supply voltage since voltage is quadratically related to power. This dissertation considers the problem of lowering the supply voltage at (i) the system level and at (ii) the behavioral level. At the system level, the voltage of the variable voltage processor is dynamically changed with the work load. Processors with limited sized buffers as well as those with very large buffers are considered. Given the task arrival times, deadline times, execution times, periods and switching activities, task scheduling algorithms that minimize energy or peak power are developed for the processors equipped with very large buffers. A relation between the operating voltages of the tasks for minimum energy/power is determined using the Lagrange multiplier method, and an iterative algorithm that utilizes this relation is developed. Experimental results show that the voltage assignment obtained by the proposed algorithm is very close (0.1% error) to that of the optimal energy assignment and the optimal peak power (1% error) assignment. Next, on-line and off-fine minimum energy task scheduling algorithms are developed for processors with limited sized buffers. These algorithms have polynomial time complexity and present optimal (off-line) and close-to-optimal (on-line) solutions. A procedure to calculate the minimum buffer size given information about the size of the task (maximum, minimum), execution time (best case, worst case) and deadlines is also presented. At the behavioral level, resources operating at multiple voltages are used to minimize power while maintaining the throughput. Such a scheme has the advantage of allowing modules on the critical paths to be assigned to the highest voltage levels (thus meeting the required timing constraints) while allowing modules on non-critical paths to be assigned

Complete characterization of voltage sags: an alternative to achieve energy quality

International Nuclear Information System (INIS)

Zuniga Medina, Edgar Andres; Vasco Garcia, Carlos Andres

1992-01-01

In this paper, the meaning of the power quality and its negative influence in the automation processes are presented. Voltage sags, the problems they cause and a methodology to characterize the phenomenon are also presented. Once the problems associated with the different sensible loads connected to a power system are identified, the cause of the bad quality of the electrical energy provided those loads is then established; voltage sags are one of the most common phenomenon that requires characterization in order to diminish their negative impact on the industrial processes

An Integrated Chip High-Voltage Power Receiver for Wireless Biomedical Implants

Directory of Open Access Journals (Sweden)

Vijith Vijayakumaran Nair

2015-06-01

Full Text Available In near-field wireless-powered biomedical implants, the receiver voltage largely overrides the compliance of low-voltage power receiver systems. To limit the induced voltage, generally, low-voltage topologies utilize limiter circuits, voltage clippers or shunt regulators, which are power-inefficient methods. In order to overcome the voltage limitation and improve power efficiency, we propose an integrated chip high-voltage power receiver based on the step down approach. The topology accommodates voltages as high as 30 V and comprises a high-voltage semi-active rectifier, a voltage reference generator and a series regulator. Further, a battery management circuit that enables safe and reliable implant battery charging based on analog control is proposed and realized. The power receiver is fabricated in 0.35-μm high-voltage Bipolar-CMOS-DMOStechnology based on the LOCOS0.35-μm CMOS process. Measurement results indicate 83.5% power conversion efficiency for a rectifier at 2.1 mA load current. The low drop-out regulator based on the current buffer compensation and buffer impedance attenuation scheme operates with low quiescent current, reduces the power consumption and provides good stability. The topology also provides good power supply rejection, which is adequate for the design application. Measurement results indicate regulator output of 4 ± 0.03 V for input from 5 to 30 V and 10 ± 0.05 V output for input from 11 to 30 V with load current 0.01–100 mA. The charger circuit manages the charging of the Li-ion battery through all if the typical stages of the Li-ion battery charging profile.

Effects of Electrode Material on the Voltage of a Tree-Based Energy Generator.

Directory of Open Access Journals (Sweden)

Zhibin Hao

Full Text Available The voltage between a standing tree and its surrounding soil is regarded as an innovative renewable energy source. This source is expected to provide a new power generation system for the low-power electrical equipment used in forestry. However, the voltage is weak, which has caused great difficulty in application. Consequently, the development of a method to increase the voltage is a key issue that must be addressed in this area of applied research. As the front-end component for energy harvesting, a metal electrode has a material effect on the level and stability of the voltage obtained. This study aimed to preliminarily ascertain the rules and mechanisms that underlie the effects of electrode material on voltage. Electrodes of different materials were used to measure the tree-source voltage, and the data were employed in a comparative analysis. The results indicate that the conductivity of the metal electrode significantly affects the contact resistance of the electrode-soil and electrode-trunk contact surfaces, thereby influencing the voltage level. The metal reactivity of the electrode has no significant effect on the voltage. However, passivation of the electrode materials markedly reduces the voltage. Suitable electrode materials are demonstrated and recommended.

Unequal Input Voltages Distribution Between the Serial Connected Halfbridges

Directory of Open Access Journals (Sweden)

Radovan Ovcarcik

2006-01-01

Full Text Available This paper describes a topology of DC-DC converter consisting in two serial connected half-bridges. Secondary circuit is realized like a conventional full-wave rectifier. The main advantage of this topology is the possibility of dividing the input voltage between the half-bridges. The converter is controlled using the phase-shift modulation, which allows a ZVSoperation mode. The voltage unbalance between the inputs causes an important problem of the presented topology. It is necessary to avoid it by the control algorithm, which is described in the text. The practical results show a zero voltage switching technique and the limits of the chosen topology and of the control.

Voltage-dependent gating in a "voltage sensor-less" ion channel.

Directory of Open Access Journals (Sweden)

Harley T Kurata

2010-02-01

Full Text Available The voltage sensitivity of voltage-gated cation channels is primarily attributed to conformational changes of a four transmembrane segment voltage-sensing domain, conserved across many levels of biological complexity. We have identified a remarkable point mutation that confers significant voltage dependence to Kir6.2, a ligand-gated channel that lacks any canonical voltage-sensing domain. Similar to voltage-dependent Kv channels, the Kir6.2[L157E] mutant exhibits time-dependent activation upon membrane depolarization, resulting in an outwardly rectifying current-voltage relationship. This voltage dependence is convergent with the intrinsic ligand-dependent gating mechanisms of Kir6.2, since increasing the membrane PIP2 content saturates Po and eliminates voltage dependence, whereas voltage activation is more dramatic when channel Po is reduced by application of ATP or poly-lysine. These experiments thus demonstrate an inherent voltage dependence of gating in a "ligand-gated" K+ channel, and thereby provide a new view of voltage-dependent gating mechanisms in ion channels. Most interestingly, the voltage- and ligand-dependent gating of Kir6.2[L157E] is highly sensitive to intracellular [K+], indicating an interaction between ion permeation and gating. While these two key features of channel function are classically dealt with separately, the results provide a framework for understanding their interaction, which is likely to be a general, if latent, feature of the superfamily of cation channels.

Switching phenomena in high-voltage circuit breakers

International Nuclear Information System (INIS)

Nakanishi, K.

1991-01-01

The topics covered in this book include: general problems concerning current interruption, the physical arc model, and miscellaneous types of modern switching apparatus, such as gas circuit breakers, gas-insulated switch-gear, vacuum circuit breakers and high-voltage direct-current circuit breakers

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.

The problem of the driverless vehicle specified path stability control

Science.gov (United States)

Buznikov, S. E.; Endachev, D. V.; Elkin, D. S.; Strukov, V. O.

2018-02-01

Currently the effort of many leading foreign companies is focused on creation of driverless transport for transportation of cargo and passengers. Among many practical problems arising while creating driverless vehicles, the problem of the specified path stability control occupies a central place. The purpose of this paper is formalization of the problem in question in terms of the quadratic functional of the control quality, the comparative analysis of the possible solutions and justification of the choice of the optimum technical solution. As square value of the integral of the deviation from the specified path is proposed as the quadratic functional of the control quality. For generation of the set of software and hardware solution variants the Zwicky “morphological box” method is used within the hardware and software environments. The heading control algorithms use the wheel steering angle data and the deviation from the lane centerline (specified path) calculated based on the navigation data and the data from the video system. Where the video system does not detect the road marking, the control is carried out based on the wheel navigation system data and where recognizable road marking exits - based on to the video system data. The analysis of the test results allows making the conclusion that the application of the combined navigation system algorithms that provide quasi-optimum solution of the problem while meeting the strict functional limits for the technical and economic indicators of the driverless vehicle control system under development is effective.

Passivity-Based Stability Assessment of Grid-Connected VSCs - An Overview

DEFF Research Database (Denmark)

Harnefors, Lennart; Wang, Xiongfei; Yepes, Alejandro G.

2016-01-01

The interconnection stability of a grid-connected voltage-source converter (VSC) can be assessed by the passivity properties of the VSC input admittance. If critical grid resonances fall within regions where the input admittance acts passively, i.e., has nonnegative real part, then their destabil......The interconnection stability of a grid-connected voltage-source converter (VSC) can be assessed by the passivity properties of the VSC input admittance. If critical grid resonances fall within regions where the input admittance acts passively, i.e., has nonnegative real part...

Coordinated Control of Multifunctional Inverters for Voltage Support and Harmonic Compensation in a Grid-Connected Microgrid

DEFF Research Database (Denmark)

Mousazadeh, Seyyed Yousef; Jalilian, Alireza; Savaghebi, Mehdi

2018-01-01

In this paper, a coordinated harmonic compensation and voltage support scheme is presented for distributed generations’ (DGs’) interface inverters in a resistive grid-connected microgrid. Voltage support is performed by reactive power compensation which can mitigate the over/under voltage problem...

Environmental Audits of High Voltage Objects from the View Point of Investors

International Nuclear Information System (INIS)

Marek Szuba, M.

2007-01-01

The localization of high voltage objects, e.g., overhead transmission lines, under the spatial planning and environmental protection regulations is discussed. The most important elements of the localization procedure concerning high voltage overhead lines are presented. One of the elements of this procedure is the assessment of the investment environmental impact. The environmental audit is an essential document, in which this impact is described. It seems that its scope specified in the Environmental Protection Act is not adjusted to the specificity of line investments. This gives rise to some problems in preparing environmental audits for overhead lines, e.g., possible influence of high voltage lines on the Natura 2000 area zones. Several other related problems are also highlighted in this paper. (author)

Microprocessor system for temperature regulation and stabilization

International Nuclear Information System (INIS)

Nguyen Nhi Dien; Rodionov, K.G.

1989-01-01

Microprocessor based system for temperature regulation and stabilization of an operation external object is described. The system has the direct current amplifier working according to modulator-demodulator principle. The overal gain is 100, 1000, 2000. The maximum output signal is ±10 V. The power amplifier is a thyristor one and its line voltage is 220 V, 50 Hz. The output power is 0-2 kVA. The microcontroller has a remote display terminal. Data input is 8 and data output is one. Input and output voltage is ±(0-10) V. The preselection time for stabilization is within 1 s - 18 h. The program algorithm is given. 5 figs.; 1 tab

AC transmission, with very high voltages and the 750 kV line

Energy Technology Data Exchange (ETDEWEB)

Bocker, H

1964-01-01

The economic case for adoption of extra-high voltages for transmitting electric power over distances of the order of 1000 km is discussed. Some special technical developments for solving the problems attached to such high voltages are briefly discussed, particularly in the fields of switching and transients suppression. The first 750-kV projects in Canada and Russia are mentioned. Equipment, e.g., bushings, transformers, etc., operating at such voltages are illustrated.

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.

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

OpenAIRE

Yoo, Cheol-Hee; Chung, Il-Yop; Yoo, Hyun-Jae; Hong, Sung-Soo

2014-01-01

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 (P...

Alternating voltage-induced electrochemical synthesis of colloidal Au nanoicosahedra

Energy Technology Data Exchange (ETDEWEB)

McCann, Kevin; Cloud, Jacqueline E.; Yang, Yongan, E-mail: yonyang@mines.edu [Colorado School of Mines, Department of Chemistry and Geochemistry (United States)

2013-11-15

A simple method of alternating voltage-induced electrochemical synthesis has been developed to synthesize highly dispersed colloidal Au nanoicosahedra of 14 ± 3 nm in size. This simple and effective method uses a common transformer to apply a zero-offset alternating voltage to a pair of identical Au electrodes that are immersed in an electrolyte solution containing ligands. The obtained Au nanoicosahedra in this work are among the smallest Au icosahedra synthesized in aqueous solutions. A series of experimental conditions have been studied, such as voltage, the electrolyte identity and concentration, stabilizer identity and concentration, and reaction temperature. The mechanistic study indicates that Au nanoicosahedra are produced on electrode surfaces through an intermediate state of AuO{sub x}. The kinetic rate constant of these Au icosahedra in catalyzing the reduction of 4-nitrophenol with sodium borohydride is found much larger than the literature values of similar Au nanocrystals. In addition, the synthesis of Au–Pd-alloyed NCs has also been attempted.Graphical Abstract.

Nonconservative stability problems of modern physics

CERN Document Server

Kirillov, Oleg N

2013-01-01

This work gives a complete overview on the subject of nonconservative stability from the modern point of view. Relevant mathematical concepts are presented, as well as rigorous stability results and numerous classical and contemporary examples from mechanics and physics.The book shall serve to present and prospective specialists providing the current state of knowledge in this actively developing field. The understanding of this theory is vital for many areas of technology, as dissipative effects in rotor dynamics orcelestial mechanics.

Observation of voltage fluctuations in a superconducting magnet during MHD power generation

International Nuclear Information System (INIS)

Smith, R.P.; Niemann, R.C.; Kraimer, M.R.; Zinneman, T.E.

1978-01-01

Fluctuating voltage signals on the potential taps of the ANL 5.0 T MHD Superconducting Dipole Magnet have been observed during MHD power generation at the U-25B Facility at the High Temperature Institute (IVTAN) Moscow, USSR. Various other thermodynamic and electrical parameters of the U-25B flow train have been recorded, and statistical analysis concerning correlations between the phenomena with a view of discerning causal interdependence is in progress. Voltage fluctuations observed at the magnet terminals are analyzed with special emphasis on magnet stability

Multi-Agent-Based Controller for Voltage Enhancement in AC/DC Hybrid Microgrid Using Energy Storages

Directory of Open Access Journals (Sweden)

Ahmadali Khatibzadeh

2017-02-01

Full Text Available Development of renewable energies and DC loads have led microgrids toward the creation of DC networks. The predictions show that the hybrid microgrids will be used widely in the future. This article has studied the voltage stability in the presence of sources of energy storage in AC/DC hybrid networks. However, because the different dynamics of hybrid networks applying centralized and distributed controllers will be faced with different problems, in this study, a multi-agent control for the microgrid has been used. A new structure referred to here as an event-driven microgrid control management (EDMCM has been developed to control the microgrid. This method increases response speed and accuracy of decision making. Hybrid Network Simulation results confirm the validity of the developed model.

The existence and the stability of solutions for equilibrium problems with lower and upper bounds

Directory of Open Access Journals (Sweden)

Congjun Zhang

2012-12-01

Full Text Available In this paper, we study a class of equilibrium problems with lower and upper bounds. We obtain some existence results of solutions for equilibrium problems with lower and upper bounds by employing some classical fixed-point theorems. We investigate the stability of the solution sets for the problems, and establish sufficient conditions for the upper semicontinuity, lower semicontinuity and continuity of the solution set mapping $S:Lambda_1imesLambda_2o2^{X}$ in a Hausdorff topological vector space, in the case where a set $K$ and a mapping $f$ are perturbed respectively by parameters $lambda$ and $mu.$

Study on the construction and its operating characteristics of Marx high voltage pulse generator

International Nuclear Information System (INIS)

Chung, W.K.; Yook, C.C.

1984-01-01

This study is to investigate the operating characteristics of a Marx high voltage pulse generator, which is designed and fabricated for the purpose of constructing a linear theta-pinch plasma generating facility. The Marx generator consists of a 2 kJ capacitor bank of maximum output voltage of 200kV, a set of main spark switch, a triggring system, and high voltage charging power supply. The experimental results show that the operating characteristics of the generator can be controlled through varying nitrogen pressure as a filling gas. The output pulse of the generator is achieved close to the estimated voltage with the rise time of 3*m seconds. The stability of the generator is also very satisfactory within operating range of main spark switch. (Author)

Uniformity and Stability of the CMS RPC Detector at the LHC

CERN Document Server

Costantini, S; Cimmino, A.; Garcia, G.; Lellouch, J.; Marinov, A.; Ocampo, A.; Strobbe, N.; Thyssen, F.; Tytgat, M.; Verwilligen, P.; Yazgan, E.; Zaganidis, N.; Dimitrov, A.; Hadjiiska, R.; Litov, L.; Pavlov, B.; Petkov, P.; Aleksandrov, A.; Genchev, V.; Iaydjiev, P.; Rodozov, M.; Shopova, M.; Sultanov, G.; Ban, Y.; Cai, J.; Ge, Y.; Li, Q.; Qian, S.; Xue, Z.; Avila, C.; Chaparro, L.F.; Gomez, J.P.; Gomez Moreno, B.; Osorio Oliveros, A.F.; Sanabria, J.C.; Assran, Y.; Sharma, A.; Abbrescia, M.; Calabria, C.; Colaleo, A.; Loddo, F.; Maggi, M.; Pugliese, G.; Benussi, L.; Bianco, S.; Colafranceschi, S.; Piccolo, D.; Buontempo, S.; Carrillo, C.; Iorio, O.; Paolucci, P.; Berzano, U.; Gabusi, M.; Vitulo, P.; Kang, M.; Lee, K.S.; Park, S.K.; Shin, S.; Choi, Y.; Goh, J.; Kim, M.S.; Seo, H.

2013-01-01

The Resistive Plate Chambers (RPCs) are employed in the CMS experiment at the LHC as dedicated trigger system both in the barrel and in the endcap. This note presents results of the RPC detector uniformity and stability during the 2011 data taking period, and preliminary results obtained with 2012 data. The detector uniformity has been ensured with a dedicated High Voltage scan with LHC collisions, in order to determine the optimal operating working voltage of each individual RPC chamber installed in CMS. Emphasis is given on the procedures and results of the High Voltage calibration. Moreover, an increased detector stability has been obtained by automatically taking into account temperature and atmospheric pressure variations in the CMS cavern.

A multi-mode operation control strategy for flexible microgrid based on sliding-mode direct voltage and hierarchical controls.

Science.gov (United States)

Zhang, Qinjin; Liu, Yancheng; Zhao, Youtao; Wang, Ning

2016-03-01

Multi-mode operation and transient stability are two problems that significantly affect flexible microgrid (MG). This paper proposes a multi-mode operation control strategy for flexible MG based on a three-layer hierarchical structure. The proposed structure is composed of autonomous, cooperative, and scheduling controllers. Autonomous controller is utilized to control the performance of the single micro-source inverter. An adaptive sliding-mode direct voltage loop and an improved droop power loop based on virtual negative impedance are presented respectively to enhance the system disturbance-rejection performance and the power sharing accuracy. Cooperative controller, which is composed of secondary voltage/frequency control and phase synchronization control, is designed to eliminate the voltage/frequency deviations produced by the autonomous controller and prepare for grid connection. Scheduling controller manages the power flow between the MG and the grid. The MG with the improved hierarchical control scheme can achieve seamless transitions from islanded to grid-connected mode and have a good transient performance. In addition the presented work can also optimize the power quality issues and improve the load power sharing accuracy between parallel VSIs. Finally, the transient performance and effectiveness of the proposed control scheme are evaluated by theoretical analysis and simulation results. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Advanced hybrid transient stability and EMT simulation for VSC-HVDC systems

NARCIS (Netherlands)

Van Der Meer, A.A.; Gibescu, M.; Van Der Meijden, M.A.M.M.; Kling, W.L.; Ferreira, J.A.

2015-01-01

This paper deals with advanced hybrid transient stability and electromagnetic-transient (EMT) simulation of combined ac/dc power systems containing large amounts of renewable energy sources interfaced through voltage-source converter-high-voltage direct current (VSC-HVDC). The concerning transient

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.

Mitigation of voltage sags in the distribution system with dynamic voltage restorer

International Nuclear Information System (INIS)

Viglas, D.; Belan, A.

2012-01-01

Dynamic voltage restorer is a custom power device that is used to improve voltage sags or swells in electrical distribution system. The components of the Dynamic Voltage Restorer consist of injection transformers, voltage source inverter, passive filters and energy storage. The main function of the Dynamic voltage restorer is used to inject three phase voltage in series and in synchronism with the grid voltages in order to compensate voltage disturbances. This article deals with mitigation of voltage sags caused by three-phase short circuit. Dynamic voltage restorer is modelled in MATLAB/Simulink. (Authors)

Mitigation of voltage fluctuations with an Adaptive Var Compensator (AVC)

Energy Technology Data Exchange (ETDEWEB)

Chan, F [TransAlta Utilities Corp., Calgary, AB (Canada); Castanheira, A

1997-04-01

The installation of an Adaptive Var Compensator (AVC) to remedy a voltage flicker problem at the TIMEU sawmill in Fort Assiniboine, Alberta, was described. The TIMEU sawmill is a 980 kVA load at the end of a 25 kV feeder. Two older style J bar type saws, each driven by a 200 Hp motor, are used to operate the wood processing services. The sawing and chipping process resulted in the generation of significant voltage flicker on the 25 kV distribution system. The AVC provided cycle per cycle reactive compensation and voltage support; no further complaints of flicker were received.

Modeling, analysis, and design of stationary reference frame droop controlled parallel three-phase voltage source inverters

DEFF Research Database (Denmark)

Vasquez, Juan Carlos; Guerrero, Josep M.; Savaghebi, Mehdi

2011-01-01

and discussed. Experimental results are provided to validate the performance and robustness of the VSIs functionality during Islanded and grid-connected operations, allowing a seamless transition between these modes through control hierarchies by regulating frequency and voltage, main-grid interactivity......Power electronics based microgrids consist of a number of voltage source inverters (VSIs) operating in parallel. In this paper, the modeling, control design, and stability analysis of three-phase VSIs are derived. The proposed voltage and current inner control loops and the mathematical models...

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.

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.

Voltage regulating circuit

NARCIS (Netherlands)

2005-01-01

A voltage regulating circuit comprising a rectifier (2) for receiving an AC voltage (Vmains) and for generating a rectified AC voltage (vrec), and a capacitor (3) connected in parallel with said rectified AC voltage for providing a DC voltage (VDC) over a load (5), characterized by a unidirectional

High Voltage Surface Degradation on Carbon Blacks in Lithium Ion Batteries

DEFF Research Database (Denmark)

Younesi, Reza

In order to increase the power density of Li-ion batteries, much research is focused on developing cathode materials that can operate at high voltages above 4.5 V with a high capacity, high cycling stability, and rate capability. However, at high voltages all the components of positive electrodes...... including carbon black (CB) additives have a potential risk of degradation. Though the weight percentage of CB in commercial batteries is generally very small, the volumetric amount and thus the surface area of CB compose a rather large part of a cathode due to its small particle size (≈ 50 nm) and high...

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.

Response of dairy cattle to transient voltages and magnetic fields

International Nuclear Information System (INIS)

Reinemann, D.J.; Laughlin, N.K.; Stetson, L.E.

1995-01-01

Stray voltages in dairy facilities have been studied since the 1970's. Previous research using steady-state ac and dc voltages has defined cow-contact voltage levels which may cause behavior and associated production problems. This research was designed to address concerns over possible effects of transient voltages and magnetic fields on dairy cows. Dairy cows response to transient voltages and magnetic fields was measured. The waveforms of the transient voltages applied were: 5 cycles of 60-Hz ac with a total pulse time of 83 ms, 1 cycle of 60-Hz ac with a total pulse time of 16 ms, and 1 cycle of an ac square wave (spiking positive and negative) of 2-ms duration. Alternating magnetic fields were produced by passing 60-Hz ac fundamental frequency with 2nd and 3rd harmonic and random noise components in metal structures around the cows. The maximum magnetic field associated with this current flow was in excess of 4 G. A wide range of sensitivity to transient voltages was observed among cows. Response levels from 24 cows to each transient exposure were normally distributed. No responses to magnetic fields were observed

Lagrangian relative equilibria for a gyrostat in the three-body problem: bifurcations and stability

Energy Technology Data Exchange (ETDEWEB)

Guirao, Juan L G; Vera, Juan A, E-mail: juan.garcia@upct.e, E-mail: juanantonio.vera@upct.e [Departamento de Matematica Aplicada y EstadIstica, Universidad Politecnica de Cartagena, Hospital de Marina, 30203 Cartagena, Region de Murcia (Spain)

2010-05-14

In this paper we consider the non-canonical Hamiltonian dynamics of a gyrostat in the frame of the three-body problem. Using geometric/mechanic methods we study the approximate dynamics of the truncated Legendre series representation of the potential of an arbitrary order. Working in the reduced problem, we study the existence of relative equilibria that we refer to as Lagrange type following the analogy with the standard techniques. We provide necessary and sufficient conditions for the linear stability of Lagrangian relative equilibria if the gyrostat morphology form is close to a sphere. Thus, we generalize the classical results on equilibria of the three-body problem and many results on them obtained by the classic approach for the case of rigid bodies.

Influence of bias voltage on the stability of CsI photocathodes exposed to air

CERN Document Server

Nitti, M A; Nappi, E; Singh, B K; Valentini, A

2002-01-01

We describe a possible correlation between the bias voltage applied to the substrate during the growth of CsI photocathodes and the variation of quantum efficiency (QE) after one day exposure to humid air. It was found that fresh samples are much less sensitive to humid air when a high negative bias voltage was applied during film growth. A model based on surface film interaction with water molecules is presented for the observed effect. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements have been performed to examine, respectively, the bulk structure and the surface of fresh and exposed CsI samples. Also reported are transmittance measurements for fresh and aged CsI samples in the wavelength range 190-850 nm.

A New Approach to HVDC Grid Voltage Control Based on Generalized State Feedback

DEFF Research Database (Denmark)

Beerten, Jef; Eriksson, Robert; Van Hertem, Dirk

2014-01-01

in the system hamper a straight-forward definition of the power sharing. The use of a common DC voltage signal for the control can solve some of the problems. However, it disregards some of the benefits that are associated with the use of a local voltage control, such as the tendency of a controller using local...... by combining the local voltage signal available at the converter terminals with remote voltage signals at different locations in the DC system by means of communication. The local voltage feedback control is used for a fast, reliable system response. The introduction of the remote voltage signals...... in the control allows to differentiate the system response for different converter outages. Simulation results show the validity of the proposed control scheme....

Stability of recursive out-of-sequence measurement filters: an open problem

Science.gov (United States)

Chen, Lingji; Moshtagh, Nima; Mehra, Raman K.

2011-06-01

In many applications where communication delays are present, measurements with earlier time stamps can arrive out-of-sequence, i.e., after state estimates have been obtained for the current time instant. To incorporate such an Out-Of-Sequence Measurement (OOSM), many algorithms have been proposed in the literature to obtain or approximate the optimal estimate that would have been obtained if the OOSM had arrived in-sequence. When OOSM occurs repeatedly, approximate estimations as a result of incorporating one OOSM have to serve as the basis for incorporating yet another OOSM. The question of whether the "approximation of approximation" is well behaved, i.e., whether approximation errors accumulate in a recursive setting, has not been adequately addressed in the literature. This paper draws attention to the stability question of recursive OOSM processing filters, formulates the problem in a specific setting, and presents some simulation results that suggest that such filters are indeed well-behaved. Our hope is that more research will be conducted in the future to rigorously establish stability properties of these filters.

Controlling Chaos and Voltage Collapse using Layered Recurrent Network-based PID-SVC in Power Systems

Directory of Open Access Journals (Sweden)

I Made Ginarsa

2013-11-01

Full Text Available Chaos and voltage collapse occurred in critical power systems due to disturbing of energy. PID-SVC layered reccurrent neural network-based (LRN-based PID-SVC was proposed to solve this problem. A PID was used to control chaos and voltage collapse. Then, an SVC LRN-based to maintan the load voltage. By using the proposed controller, chaos and voltage collapse were able to suppress and maintain the load voltage around the setting value. Furthemore, the proposed controller gives better response than PI-SVC controller.

Revisión sobre métodos matemáticos para el estudio de la estabilidad del voltaje en los sistemas eléctricos de potencia; A review on mathematics methodo to study the voltage stability on electric power systems

Directory of Open Access Journals (Sweden)

Zaid García Sánchez

2011-05-01

Full Text Available En Cuba desde la década del 70 se empezaron a desarrollar algoritmos para realizar el estudio de los regímenes estacionarios y transitorios del Sistema Eléctrico Nacional (SEN. Particular énfasis se hizo sobre el desarrollo de algoritmos y programas para computadoras para realizar el estudio de la estabilidad transitoria. Actualmente se utiliza ampliamente el programa Power System Explorer (PSX, el que posee amplias facilidades para realizar estudios sobre regímenes estaciones y transitorios de los sistemas eléctricos de potencia. A través de los estudios realizados para la planificación y la experiencia alcanzada sobre la explotación del SEN, con su estructura actual, se ha revelado la necesidad de estudiar en detalles los problemas relacionados con el voltaje, en particular el problema de la estabilidad del voltaje del SEN. En este artículo se realiza una primera revisión sobre algunos de los métodos matemáticos estáticos y dinámicos que se han desarrollado y que recoge la bibliografía sobre el tema de la Estabilidad del Voltaje en los Sistemas Eléctricos de Potencia.  In Cuba, from the seventies of the past century, different algorithms to study stationary and transient regimes of the Cuban Electric System were developed. Those algorithms and computer programs were focused in the study of transient stability. Currently, we use widely the computer program “Power System Explorer” (PSX which have a lot of facilities to make studies about stationary and transient regimes of electric power systems. Due to the studies about planning of electric power systems and the accumulated experience working with Cuban Electric System, the need of study the problems related with voltage stability of Cuban Electric System has arisen. In this paper, we make a first review about some static and dynamic mathematical methods included in bibliography about voltage stability of electric power systems.

Mitigation of Grid Current Distortion for LCL-Filtered Voltage Source Inverter with Inverter Current Feedback Control

DEFF Research Database (Denmark)

Xin, Zhen; Mattavelli, Paolo; Yao, WenLi

2018-01-01

LCL filters feature low inductance; thus, the injected grid current from an LCL-filtered Voltage Source Inverter (VSI) can be easily distorted by grid voltage harmonics. This problem is especially tough for the control system with Inverter-side Current Feedback (ICF), since the grid current...... harmonics can freely flow into the filter capacitor. In this case, because of the loss of harmonic information, traditional harmonic controllers fail to mitigate the grid current distortion. Although this problem may be avoided using the grid voltage feedforward scheme, the required differentiators may...

A study of offshore wind HVDC system stability and control

Energy Technology Data Exchange (ETDEWEB)

Liu, Hanchao; Sun, Jian [Rensselaer Polytechnic Institute, Troy, NY (United States). Dept. of Electrical, Computer and Systems Engineering

2011-07-01

This work is concerned with the stability and control of ac power collection buses in offshore wind farms with high-voltage dc (HVDC) transmission connection to onshore power grid. The focus of the work is high-frequency interactions among the wind turbines, the ac collection bus and the filters, as well as the HVDC rectifier. Both voltage-source converter and line-commutated converter based HVDC systems are considered. To study high-frequency stability, particularly harmonic resonance in the ac bus, small-signal impedance models are developed for the wind inverters and the HVDC rectifier by using harmonic linearization techniques. An impedance-based stability criterion is applied to assess system stability in both positive- and negative-sequence domain. Small-signal stability conditions and requirements are developed from analytical impedance models. Detailed system-level simulation is used to validated the small-signal analysis. The goal of the study is to develop system design and control techniques that minimize the cost of the offshore infrastructure while guaranteeing system stability and power quality. (orig.)

Structure and hydration of membranes embedded with voltage-sensing domains.

Science.gov (United States)

Krepkiy, Dmitriy; Mihailescu, Mihaela; Freites, J Alfredo; Schow, Eric V; Worcester, David L; Gawrisch, Klaus; Tobias, Douglas J; White, Stephen H; Swartz, Kenton J

2009-11-26

Despite the growing number of atomic-resolution membrane protein structures, direct structural information about proteins in their native membrane environment is scarce. This problem is particularly relevant in the case of the highly charged S1-S4 voltage-sensing domains responsible for nerve impulses, where interactions with the lipid bilayer are critical for the function of voltage-activated ion channels. Here we use neutron diffraction, solid-state nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics simulations to investigate the structure and hydration of bilayer membranes containing S1-S4 voltage-sensing domains. Our results show that voltage sensors adopt transmembrane orientations and cause a modest reshaping of the surrounding lipid bilayer, and that water molecules intimately interact with the protein within the membrane. These structural findings indicate that voltage sensors have evolved to interact with the lipid membrane while keeping energetic and structural perturbations to a minimum, and that water penetrates the membrane, to hydrate charged residues and shape the transmembrane electric field.

Beyond voltage-gated ion channels: Voltage-operated membrane proteins and cellular processes.

Science.gov (United States)

Zhang, Jianping; Chen, Xingjuan; Xue, Yucong; Gamper, Nikita; Zhang, Xuan

2018-04-18

Voltage-gated ion channels were believed to be the only voltage-sensitive proteins in excitable (and some non-excitable) cells for a long time. Emerging evidence indicates that the voltage-operated model is shared by some other transmembrane proteins expressed in both excitable and non-excitable cells. In this review, we summarize current knowledge about voltage-operated proteins, which are not classic voltage-gated ion channels as well as the voltage-dependent processes in cells for which single voltage-sensitive proteins have yet to be identified. Particularly, we will focus on the following. (1) Voltage-sensitive phosphoinositide phosphatases (VSP) with four transmembrane segments homologous to the voltage sensor domain (VSD) of voltage-gated ion channels; VSPs are the first family of proteins, other than the voltage-gated ion channels, for which there is sufficient evidence for the existence of the VSD domain; (2) Voltage-gated proton channels comprising of a single voltage-sensing domain and lacking an identified pore domain; (3) G protein coupled receptors (GPCRs) that mediate the depolarization-evoked potentiation of Ca 2+ mobilization; (4) Plasma membrane (PM) depolarization-induced but Ca 2+ -independent exocytosis in neurons. (5) Voltage-dependent metabolism of phosphatidylinositol 4,5-bisphosphate (PtdIns[4,5]P 2 , PIP 2 ) in the PM. These recent discoveries expand our understanding of voltage-operated processes within cellular membranes. © 2018 Wiley Periodicals, Inc.

Multi-objective optimization control of plug-in electric vehicles in low voltage distribution networks

DEFF Research Database (Denmark)

García-Villalobos, J.; Zamora, I.; Knezovic, Katarina

2016-01-01

The massive introduction of plug-in electric vehicles (PEVs) into low voltage (LV) distribution networks will lead to several problems, such as: increase of energy losses, decrease of distribution transformer lifetime, lines and transformer overload issues, voltage drops and unbalances...

Research on a Hierarchical Dynamic Automatic Voltage Control System Based on the Discrete Event-Driven Method

Directory of Open Access Journals (Sweden)

Yong Min

2013-06-01

Full Text Available In this paper, concepts and methods of hybrid control systems are adopted to establish a hierarchical dynamic automatic voltage control (HD-AVC system, realizing the dynamic voltage stability of power grids. An HD-AVC system model consisting of three layers is built based on the hybrid control method and discrete event-driven mechanism. In the Top Layer, discrete events are designed to drive the corresponding control block so as to avoid solving complex multiple objective functions, the power system’s characteristic matrix is formed and the minimum amplitude eigenvalue (MAE is calculated through linearized differential-algebraic equations. MAE is applied to judge the system’s voltage stability and security and construct discrete events. The Middle Layer is responsible for management and operation, which is also driven by discrete events. Control values of the control buses are calculated based on the characteristics of power systems and the sensitivity method. Then control values generate control strategies through the interface block. In the Bottom Layer, various control devices receive and implement the control commands from the Middle Layer. In this way, a closed-loop power system voltage control is achieved. Computer simulations verify the validity and accuracy of the HD-AVC system, and verify that the proposed HD-AVC system is more effective than normal voltage control methods.

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.

Element diameter free stability parameters for stabilized methods applied to fluids

International Nuclear Information System (INIS)

Franca, L.P.; Madureira, A.L.

1992-08-01

Stability parameters for stabilized methods in fluids are suggested. The computation of the largest eigenvalue of a generalized eigenvalue problem replaces controversial definitions of element diameters and inverse estimate constants, used heretofore to compute these stability parameters. The design is employed in the advective-diffusive model, incompressible Navier-Stokes equations and the Stokes problem. (author)

Stability Constrained Efficiency Optimization for Droop Controlled DC-DC Conversion System

DEFF Research Database (Denmark)

Meng, Lexuan; Dragicevic, Tomislav; Guerrero, Josep M.

2013-01-01

implementing tertiary regulation. Moreover, system dynamic is affected when shifting VRs. Therefore, the stability is considered in optimization by constraining the eigenvalues arising from dynamic state space model of the system. Genetic algorithm is used in searching for global efficiency optimum while....... As the efficiency of each converter changes with output power, virtual resistances (VRs) are set as decision variables for adjusting power sharing proportion among converters. It is noteworthy that apart from restoring the voltage deviation, secondary control plays an important role to stabilize dc bus voltage when...

Effect of AC electric fields on the stabilization of premixed bunsen flames

KAUST Repository

Kim, Minkuk

2011-01-01

The stabilization characteristics of laminar premixed bunsen flames have been investigated experimentally for stoichiometric methane-air mixture by applying AC voltage to the nozzle with the single-electrode configuration. The detachment velocity either at blowoff or partial-detachment has been measured by varying the applied voltage and frequency of AC. The result showed that the detachment velocity increased with the applied AC electric fields, such that the flame could be nozzle-attached even over five times of the blowoff velocity without having electric fields. There existed four distinct regimes depending on applied AC voltage and frequency. In the low voltage regime, the threshold condition of AC electric fields was identified, below which the effect of electric fields on the detachment velocity is minimal. In the moderate voltage regime, the flame base oscillated with the frequency synchronized to AC frequency and the detachment velocity increased linearly with the applied AC voltage and nonlinearly with the frequency. In the high voltage regime, two different sub-regimes depending on AC frequency were observed. For relatively low frequency, the flame base oscillated with the applied AC frequency together with the half frequency and the variation of the detachment velocity was insensitive to the applied voltage. For relatively high frequency, the stabilization of the flame was significantly affected by the generation of streamers and the detachment velocity decreased with the applied voltage. © 2010 Published by Elsevier Inc. on behalf of The Combustion Institute. All rights reserved.

Design of auto-control high-voltage control system of pulsed neutron generator

International Nuclear Information System (INIS)

Lv Juntao

2008-01-01

It is difficult to produce multiple anode controlling time sequences under different logging mode for the high-voltage control system of the conventional pulsed neutron generator. It is also difficult realize sequential control among anode high-voltage, filament power supply and target voltage to make neutron yield stable. To these problems, an auto-control high-voltage system of neutron pulsed generator was designed. It not only can achieve anode high-voltage double blast time sequences, which can measure multiple neutron blast time sequences such as Σ, activated spectrum, etc. under inelastic scattering mode, but also can realize neutron generator real-time measurement of multi-state parameters and auto-control such as target voltage pulse width modulation (PWM), filament current, anode current, etc., there by it can produce stable neutron yield and realize stable and accurate measurement of the pulsed neutron full spectral loging tool. (authors)

Stabilization of synchrotron radiation x-ray beam by MOSTAB

CERN Document Server

Kudo, T P; Tanida, H; Furukawa, Y; Hirono, T; Ishikawa, T; Nishino, Y

2003-01-01

Monochromator stabilization (MOSTAB) is a feedback control system to stabilize an x-ray beam of synchrotron radiation. It applies a feedback voltage to a piezo electric transducer attached to a double-crystal monochromator. We developed MOSTAB modules and examined their performances using SPring-8 beamlines. The x-ray beam position stabilization using MOSTAB was realized simultaneously with the x-ray beam intensity stabilization. As an example of its application, we performed EXAFS measurement with MOSTAB. (author)

Improved modeling of new three-phase high voltage transformer with magnetic shunts

Directory of Open Access Journals (Sweden)

Chraygane M.

2015-03-01

Full Text Available This original paper deals with a new approach for the study of behavior in nonlinear regime of a new three-phase high voltage power supply for magnetrons, used for the microwave generators in industrial applications. The design of this system is composed of a new three-phase leakage flux transformer supplying by phase a cell, composed of a capacitor and a diode, which multiplies the voltage and stabilizes the current. Each cell. in turn, supplies a single magnetron. An equivalent model of this transformer is developed taking into account the saturation phenomenon and the stabilization process of each magnetron. Each inductance of the model is characterized by a non linear relation between flux and current. This model was tested by EMTP software near the nominal state. The theoretical results were compared to experimental measurements with a good agreement. Relative to the current device, the new systemprovides gains of size, volume, cost of implementation and maintenance which make it more economical.

Reliability of supply of switchgear for auxiliary low voltage in substations extra high voltage to high voltage

Directory of Open Access Journals (Sweden)

Perić Dragoslav M.

2015-01-01

Full Text Available Switchgear for auxiliary low voltage in substations (SS of extra high voltages (EHV to high voltage (HV - SS EHV/HV kV/kV is of special interest for the functioning of these important SS, as it provides a supply for system of protection and other vital functions of SS. The article addresses several characteristic examples involving MV lines with varying degrees of independence of their supply, and the possible application of direct transformation EHV/LV through special voltage transformers. Auxiliary sources such as inverters and diesel generators, which have limited power and expensive energy, are also used for the supply of switchgear for auxiliary low voltage. Corresponding reliability indices are calculated for all examples including mean expected annual engagement of diesel generators. The applicability of certain solutions of switchgear for auxiliary low voltage SS EHV/HV, taking into account their reliability, feasibility and cost-effectiveness is analyzed too. In particular, the analysis of applications of direct transformation EHV/LV for supply of switchgear for auxiliary low voltage, for both new and existing SS EHV/HV.

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.

High voltage systems

International Nuclear Information System (INIS)

Martin, M.

1991-01-01

Industrial processes usually require electrical power. This power is used to drive motors, to heat materials, or in electrochemical processes. Often the power requirements of a plant require the electric power to be delivered at high voltage. In this paper high voltage is considered any voltage over 600 V. This voltage could be as high as 138,000 V for some very large facilities. The characteristics of this voltage and the enormous amounts of power being transmitted necessitate special safety considerations. Safety must be considered during the four activities associated with a high voltage electrical system. These activities are: Design; Installation; Operation; and Maintenance

Low-cost wireless voltage & current grid monitoring

Energy Technology Data Exchange (ETDEWEB)

Hines, Jacqueline [SenSanna Inc., Arnold, MD (United States)

2016-12-31

This report describes the development and demonstration of a novel low-cost wireless power distribution line monitoring system. This system measures voltage, current, and relative phase on power lines of up to 35 kV-class. The line units operate without any batteries, and without harvesting energy from the power line. Thus, data on grid condition is provided even in outage conditions, when line current is zero. This enhances worker safety by detecting the presence of voltage and current that may appear from stray sources on nominally isolated lines. Availability of low-cost power line monitoring systems will enable widespread monitoring of the distribution grid. Real-time data on local grid operating conditions will enable grid operators to optimize grid operation, implement grid automation, and understand the impact of solar and other distributed sources on grid stability. The latter will enable utilities to implement eneygy storage and control systems to enable greater penetration of solar into the grid.

Accelerator System Development at High Voltage Engineering

International Nuclear Information System (INIS)

Klein, M. G.; Gottdang, A.; Haitsma, R. G.; Mous, D. J. W.

2009-01-01

Throughout the years, HVE has continuously extended the capabilities of its accelerator systems to meet the rising demands from a diverse field of applications, among which are deep level ion implantation, micro-machining, neutron production for biomedical research, isotope production or accelerator mass spectrometry. Characteristic for HVE accelerators is the coaxial construction of the all solid state power supply around the acceleration tubes. With the use of solid state technology, the accelerators feature high stability and very low ripple. Terminal voltages range from 1 to 6 MV for HVE Singletrons and Tandetrons. The high-current versions of these accelerators can provide ion beams with powers of several kW. In the last years, several systems have been built with terminal voltages of 1.25 MV, 2 MV and 5 MV. Recently, the first system based on a 6 MV Tandetron has passed the factory tests. In this paper we describe the characteristics of the HVE accelerator systems and present as example recent systems.

一种提高智能赛车速度和平稳性的方法%A Method of Accelerating Speed and Improving Stability of Intelligent Racing Car

Institute of Scientific and Technical Information of China (English)

牛宏侠; 侯涛

2011-01-01

针对智能车竟赛中赛车速度受电池电压影响较大的问题,提出一种提高智能赛车速度和平稳性的方法.通过对电池电压检测采样来修正占空比,达到了恒定每个周期平均电压的目的,从而保证了赛车速度不变.实验结果证明,该方法既可以保证赛车稳定,又可以提高比赛速度.%Aiming at the problem that the speed of intelligent racing car is influenced by car battery voltage, introduce a method to accelerate speed and improve stability. That is, modify duty cycle according to the sampling value of battery voltage,and realize the every cycle voltage is stable and average. Then, ensure the car speed is stable. The test result shows that the method can ensure stability and accelerate speed.

Comparative Study of Breakdown Voltage of Mineral, Synthetic and Natural Oils and Based Mineral Oil Mixtures under AC and DC Voltages

Directory of Open Access Journals (Sweden)

Abderrahmane Beroual

2017-04-01

Full Text Available This paper deals with a comparative study of AC and DC breakdown voltages of based mineral oil mixtures with natural and synthetic esters mainly used in high voltage power transformers. The goal was to analyze the performances of oil mixtures from the dielectric withstand point of view and to predict the behavior of transformers originally filled with mineral oil and re-filled with synthetic or natural ester oils when emptied for maintenance. The study concerns mixtures based on 20%, 50%, and 80% of natural and synthetic ester oils. AC breakdown voltages were measured using a sphere-sphere electrode system according to IEC 60156 specifications; the same specification was adopted for DC measurements since there is no standard specifications for this voltage waveform. A statistical analysis of the mean values, standard deviations, and histograms of breakdown voltage data was carried out. The Normal and Weibull distribution functions were used to analyze the experimental data and the best function that the data followed was used to estimate the breakdown voltage with risk of 1%, 10%, and 50% probability. It was shown that whatever the applied voltage waveforms, ester oils always have a significantly higher breakdown voltage than mineral oil. The addition of only 20% of natural or synthetic ester oil was sufficient to considerably increase the breakdown voltage of mineral oil. The dielectric strength of such a mixture is much higher than that of mineral oil alone and can reach that of ester oils. From the point of view of dielectric strength, the mixtures constitute an option for improving the performance of mineral oil. Thus, re-filling of transformers containing up to 20% mineral oil residues with ester oils, does not present any problem; it is even advantageous when considering only the breakdown voltage. Under AC, the mixtures with natural ester always follow the behavior of vegetable oil alone. With the exception of the 20% mixture of natural

Extended Stable Boundary of LCL-Filtered Grid-Connected Inverter Based on An Improved Grid-Voltage Feedforward Control

DEFF Research Database (Denmark)

Lu, Minghui; Xin, Zhen; Wang, Xiongfei

2016-01-01

should be designed under one-sixth of sampling frequency. However, the low resonance frequency leads to a comparatively large filter inductance or/and capacitance. To extend the stable boundary to the region above fs/6, this paper proposes a novel voltage feedforward scheme for the LCL-filtered inverter....... Theoretical analysis is then provided to validate its feasibility and stability. Compared to other widely used active damping strategies, no extra sensors are needed because the filter capacitor voltage, which is used for voltage feedforward control, is also sampled for phase-locked loop in this paper...

Dimethylacetamide as a film-forming additive for improving the cyclic stability of high voltage lithium-rich cathode at room and elevated temperature

International Nuclear Information System (INIS)

Tu, Wenqiang; Xing, Lidan; Xia, Pan; Xu, Mengqing; Liao, Youhao; Li, Weishan

2016-01-01

Highlights: • Addition of 1% DMAc improves the cyclic performances of LLO at room and elevated temperature. • DMAc oxidizes previously to the STD electrolyte and generates a protective film on the LLO surface. • The protective film is thin and uniform. - Abstract: In this work, dimethylacetamide (DMAc) was investigated as an electrolyte film-forming additive to improve the cyclic stability of high voltage Lithium-rich layered nickel manganese cobalt oxide (LLO) cathode at room (25 °C) and elevated (55 °C) temperature. At 0.5C rate, addition of 1% DMAc slightly decreases the initial discharge capacity of LLO from 187 to 179 mAh g −1 at room temperature and 255 to 246 mAh g −1 at elevated temperature, while significantly improves the capacity retention of LLO from 65.8% to 80.2% after 200 cycles at room temperature and from 21.1% to 66.7% after 150 cycles at elevated temperature. The mechanism of DMAc improving the cyclic stability of LLO was investigated via theoretical calculation and experimental characterizations, which demonstrated that DMAc oxidized preferential to the STD (1.0 M LiPF 6 in a mixed solvent of ethylene carbonate/ethyl methyl carbonate/diethyl carbonate) electrolyte, generating a thin and uniform film on the LLO surface. This film effectively suppresses the subsequent decomposition of STD electrolyte and further degradation of spinel phase converted from the layered structure of LLO, resulting in improved cyclic stability of LLO at room and elevated temperature.

Site selection of active damper for stabilizing power electronics based power distribution system

DEFF Research Database (Denmark)

Yoon, Changwoo; Wang, Xiongfei; Bak, Claus Leth

2015-01-01

electronics based power device, which provides an adjustable damping capability to the power system where the voltage harmonic instability is measured. It can stabilize by adjusting the equivalent node impedance with its plug and play feature. This feature gives many degrees of freedom of its installation......Stability in the nowadays distribution power system is endangered by interaction problems that may arise from newly added power-electronics based power devices. Recently, a new concept to deal with this higher frequency instability, the active damper, has been proposed. The active damper is a power...... point when the system has many nodes. Therefore, this paper addresses the proper placement of an active damper in an unstable small-scale power distribution system. A time-domain model of the Cigre benchmark low-vltage network is used as a test field. The result shows the active damper location...

Glycosylation of voltage-gated calcium channels in health and disease

Czech Academy of Sciences Publication Activity Database

Lazniewska, Joanna; Weiss, Norbert

2017-01-01

Roč. 1859, č. 5 (2017), s. 662-668 ISSN 0005-2736 R&D Projects: GA ČR GA15-13556S; GA MŠk 7AMB15FR015 Institutional support: RVO:61388963 Keywords : calcium channels * voltage-gated calcium channels * N-glycosylation * ancillary subunit * trafficking * stability Subject RIV: CE - Biochemistry OBOR OECD: Biochemistry and molecular biology Impact factor: 3.498, year: 2016

Coordinated Voltage Control of a Wind Farm based on Model Predictive Control

DEFF Research Database (Denmark)

Zhao, Haoran; Wu, Qiuwei; Guo, Qinglai

2016-01-01

This paper presents an autonomous wind farm voltage controller based on Model Predictive Control (MPC). The reactive power compensation and voltage regulation devices of the wind farm include Static Var Compensators (SVCs), Static Var Generators (SVGs), Wind Turbine Generators (WTGs) and On...... are calculated based on an analytical method to improve the computation efficiency and overcome the convergence problem. Two control modes are designed for both voltage violated and normal operation conditions. A wind farm with 20 wind turbines was used to conduct case studies to verify the proposed coordinated...

Energy harvesting in high voltage measuring techniques

International Nuclear Information System (INIS)

Żyłka, Pawel; Doliński, Marcin

2016-01-01

The paper discusses selected problems related to application of energy harvesting (that is, generating electricity from surplus energy present in the environment) to supply autonomous ultra-low-power measurement systems applicable in high voltage engineering. As a practical example of such implementation a laboratory model of a remote temperature sensor is presented, which is self-powered by heat generated in a current-carrying busbar in HV- switchgear. Presented system exploits a thermoelectric harvester based on a passively cooled Peltier module supplying micro-power low-voltage dc-dc converter driving energy-efficient temperature sensor, microcontroller and a fibre-optic transmitter. Performance of the model in laboratory simulated conditions are presented and discussed. (paper)

A voltage to frequency converter for astronomical photometry

Science.gov (United States)

Dunham, E.; Elliot, J. L.

1978-01-01

A voltage to frequency converter (VFC) for general use with photomultipliers is described. For high light levels, when the dead-time corrections for a photon counter would be excessive, the VFC maintains a linear response and allows the recording of data at high time resolution. Results of laboratory tests are given for the signal-to-noise characteristics, linearity, stability, and transient response of the VFC when used in conjunction with EMI 9658 and RCA C31034 photomultipliers.

Distribution state estimation based voltage control for distribution networks; Koordinierte Spannungsregelung anhand einer Zustandsschaetzung im Verteilnetz

Energy Technology Data Exchange (ETDEWEB)

Diwold, Konrad; Yan, Wei [Fraunhofer IWES, Kassel (Germany); Braun, Martin [Fraunhofer IWES, Kassel (Germany); Stuttgart Univ. (Germany). Inst. fuer Energieuebertragung und Hochspannungstechnik (IEH)

2012-07-01

The increased integration of distributed energy units creates challenges for the operators of distribution systems. This is due to the fact that distribution systems that were initially designed for distributed consumption and central generation now face decentralized feed-in. One imminent problem associated with decentralised fee-in are local voltage violations in the distribution system, which are hard to handle via conventional voltage control strategies. This article proposes a new voltage control framework for distribution system operation. The framework utilizes reactive power of distributed energy units as well on-load tap changers to mitigate voltage problems in the network. Using an optimization-band the control strategy can be used in situations where network information is derived from distribution state estimators and thus holds some error. The control capabilities in combination with a distribution state estimator are tested using data from a real rural distribution network. The results are very promising, as voltage control is achieved fast and accurate, preventing a majority of the voltage violations during system operation under realistic system conditions. (orig.)

Simple Moving Voltage Average Incremental Conductance MPPT Technique with Direct Control Method under Nonuniform Solar Irradiance Conditions

Directory of Open Access Journals (Sweden)

Amjad Ali

2015-01-01

Full Text Available A new simple moving voltage average (SMVA technique with fixed step direct control incremental conductance method is introduced to reduce solar photovoltaic voltage (VPV oscillation under nonuniform solar irradiation conditions. To evaluate and validate the performance of the proposed SMVA method in comparison with the conventional fixed step direct control incremental conductance method under extreme conditions, different scenarios were simulated. Simulation results show that in most cases SMVA gives better results with more stability as compared to traditional fixed step direct control INC with faster tracking system along with reduction in sustained oscillations and possesses fast steady state response and robustness. The steady state oscillations are almost eliminated because of extremely small dP/dV around maximum power (MP, which verify that the proposed method is suitable for standalone PV system under extreme weather conditions not only in terms of bus voltage stability but also in overall system efficiency.

Stability of orbits around a spinning body in a pseudo-Newtonian Hill problem

International Nuclear Information System (INIS)

Steklain, A.F.; Letelier, P.S.

2009-01-01

A pseudo-Newtonian Hill problem based on a potential proposed by Artemova et al. [I.A. Artemova, G. Bjoernsson, I.D. Novikov, Astrophys. J. 461 (1996) 565] is presented. This potential reproduces some of the general relativistic effects due to the spin angular momentum of the bodies, like the dragging of inertial frames. Poincare maps, Lyapunov exponents and fractal escape techniques are employed to study the stability of bounded and unbounded orbits for different spins of the central body

Feasibility of X-ray analysis of multi-layer thin films at a single beam voltage

International Nuclear Information System (INIS)

Statham, P J

2010-01-01

Multi-layer analysis using electron beam excitation and X-ray spectrometry is a powerful tool for characterising layers down to 1 nm thickness and with typically 1 μm lateral resolution but does not always work. Most published applications have used WDS with many measurements at different beam voltages and considerable experience has been needed to choose lines and voltages particularly for complex multi-layer problems. A new objective mathematical approach is described which demonstrates whether X-ray analysis can obtain reliable results for an arbitrary multi-layer problem. A new algorithm embodied in 'ThinFilmID' software produces a single plot that shows feasibility of achieving results with a single EDS spectrum and suggests the optimal beam voltage. Synthesis of EDS spectra allows the precision in results to be estimated and acquisition conditions modified before wasting valuable instrument time. Thus, practicality of multi-layer thin film analysis at a single beam voltage can now be established without the extensive experimentation that was previously required by a microanalysis expert. Examples are shown where the algorithm discovers viable single-voltage conditions for applications that experts previously thought could only be addressed using measurements at more than one beam voltage.

Small-Signal Stability Analysis of Full-Load Converter Interfaced Wind Turbines

DEFF Research Database (Denmark)

Knüppel, Thyge; Akhmatov, Vladislav; Nielsen, Jørgen Nygård

2009-01-01

focus since the share of wind power increases substituting power generation from conventional power plants. Here, a study based on modal analysis is presented which investigate the effect of large scale integration of full-load converter interfaced wind turbines on inter-area oscillations in a three...... generator network. A detailed aggregated wind turbine model is employed which includes all necessary control functions. It is shown that the wind urbines have very low participation in the inter-area power oscillation.......Power system stability investigations of wind farms often cover the tasks of low-voltage-fault-ride-through, voltage and reactive power control, and power balancing, but not much attention has yet been paid to the task of small-signal stability. Small-signal stability analysis needs increasing...

Economical stabilized scintillation detector

International Nuclear Information System (INIS)

Anshakov, O.M.; Chudakov, V.A.; Gurinovich, V.I.

1983-01-01

An economical scintillation detector with the stabilization system of an integral type is described. Power consumed by the photomultiplier high-voltage power source is 40 mW, energy resolution is not worse than 9%. The given detector is used in a reference detector of a digital radioisotope densimeter for light media which is successfully operating for several years

Contribution to high voltage matrix switches reliability

International Nuclear Information System (INIS)

Lausenaz, Yvan

2000-01-01

Nowadays, power electronic equipment requirements are important, concerning performances, quality and reliability. On the other hand, costs have to be reduced in order to satisfy the market rules. To provide cheap, reliability and performances, many standard components with mass production are developed. But the construction of specific products must be considered following these two different points: in one band you can produce specific components, with delay, over-cost problems and eventuality quality and reliability problems, in the other and you can use standard components in a adapted topologies. The CEA of Pierrelatte has adopted this last technique of power electronic conception for the development of these high voltage pulsed power converters. The technique consists in using standard components and to associate them in series and in parallel. The matrix constitutes high voltage macro-switch where electrical parameters are distributed between the synchronized components. This study deals with the reliability of these structures. It brings up the high reliability aspect of MOSFETs matrix associations. Thanks to several homemade test facilities, we obtained lots of data concerning the components we use. The understanding of defects propagation mechanisms in matrix structures has allowed us to put forwards the necessity of robust drive system, adapted clamping voltage protection, and careful geometrical construction. All these reliability considerations in matrix associations have notably allowed the construction of a new matrix structure regrouping all solutions insuring reliability. Reliable and robust, this product has already reaches the industrial stage. (author) [fr

A stabilized MFE reduced-order extrapolation model based on POD for the 2D unsteady conduction-convection problem.

Science.gov (United States)

Xia, Hong; Luo, Zhendong

2017-01-01

In this study, we devote ourselves to establishing a stabilized mixed finite element (MFE) reduced-order extrapolation (SMFEROE) model holding seldom unknowns for the two-dimensional (2D) unsteady conduction-convection problem via the proper orthogonal decomposition (POD) technique, analyzing the existence and uniqueness and the stability as well as the convergence of the SMFEROE solutions and validating the correctness and dependability of the SMFEROE model by means of numerical simulations.

A Hybrid Optimization Method for Reactive Power and Voltage Control Considering Power Loss Minimization

DEFF Research Database (Denmark)

Liu, Chengxi; Qin, Nan; Bak, Claus Leth

2015-01-01

This paper proposes a hybrid optimization method to optimally control the voltage and reactive power with minimum power loss in transmission grid. This approach is used for the Danish automatic voltage control (AVC) system which is typically a non-linear non-convex problem mixed with both...

Technical and economic evaluation of voltage level in transmission network expansion planning using GA

International Nuclear Information System (INIS)

Jalilzadeh, S.; Kazemi, A.; Shayeghi, H.; Madavi, M.

2008-01-01

Transmission network expansion planning is an important part of power system planning. Its task is to determine an optimal network configuration according to load growth. It determines where, when and how many new transmission lines should be installed. Up to now, various methods have been presented to solve the static transmission network expansion planning (STNEP) problem, but in all of these methods, the STNEP problem has been solved regardless of voltage level of the lines. In this paper, due to different voltage levels in the transmission network, which cause different annual losses, STNEP has been studied considering the voltage level of the transmission lines and the network loss using the genetic algorithm (GA). Finally, the proposed idea has been examined on Garvers 6 bus network. The results show that considering the loss in a network with different voltage levels decreases the operational costs considerably, and the network satisfies the requirement of delivering electric power more safely and reliably to load centers

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 ...

Design, fabrication and actuation of a MEMS-based image stabilizer for photographic cell phone applications

International Nuclear Information System (INIS)

Chiou, Jin-Chern; Hung, Chen-Chun; Lin, Chun-Ying

2010-01-01

This work presents a MEMS-based image stabilizer applied for anti-shaking function in photographic cell phones. The proposed stabilizer is designed as a two-axis decoupling XY stage 1.4 × 1.4 × 0.1 mm 3 in size, and adequately strong to suspend an image sensor for anti-shaking photographic function. This stabilizer is fabricated by complex fabrication processes, including inductively coupled plasma (ICP) processes and flip-chip bonding technique. Based on the special designs of a hollow handle layer and a corresponding wire-bonding assisted holder, electrical signals of the suspended image sensor can be successfully sent out with 32 signal springs without incurring damage during wire-bonding packaging. The longest calculated traveling distance of the stabilizer is 25 µm which is sufficient to resolve the anti-shaking problem in a three-megapixel image sensor. Accordingly, the applied voltage for the 25 µm moving distance is 38 V. Moreover, the resonant frequency of the actuating device with the image sensor is 1.123 kHz.

Power System Decomposition for Practical Implementation of Bulk-Grid Voltage Control Methods

Energy Technology Data Exchange (ETDEWEB)

Vallem, Mallikarjuna R.; Vyakaranam, Bharat GNVSR; Holzer, Jesse T.; Elizondo, Marcelo A.; Samaan, Nader A.

2017-10-19

Power system algorithms such as AC optimal power flow and coordinated volt/var control of the bulk power system are computationally intensive and become difficult to solve in operational time frames. The computational time required to run these algorithms increases exponentially as the size of the power system increases. The solution time for multiple subsystems is less than that for solving the entire system simultaneously, and the local nature of the voltage problem lends itself to such decomposition. This paper describes an algorithm that can be used to perform power system decomposition from the point of view of the voltage control problem. Our approach takes advantage of the dominant localized effect of voltage control and is based on clustering buses according to the electrical distances between them. One of the contributions of the paper is to use multidimensional scaling to compute n-dimensional Euclidean coordinates for each bus based on electrical distance to perform algorithms like K-means clustering. A simple coordinated reactive power control of photovoltaic inverters for voltage regulation is used to demonstrate the effectiveness of the proposed decomposition algorithm and its components. The proposed decomposition method is demonstrated on the IEEE 118-bus system.

Large-signal stability analysis of two power converters solutions for DC shipboard microgrid

NARCIS (Netherlands)

Bosich, Daniele; Gibescu, Madeleine; Sulligoi, Giorgio

2017-01-01

Bus voltage stability is an essential requirement in DC shipboard microgrids. In presence of Constant Power Loads, voltage instability is strictly dependent on RLC filters. This paper evaluates two power converter solutions (Thyristor Converters, TCs, and diode rectifiers + DC-DC Converters, DCs)

Resonance fluorescence revival in a voltage-controlled semiconductor quantum dot

Science.gov (United States)

Reigue, Antoine; Lemaître, Aristide; Gomez Carbonell, Carmen; Ulysse, Christian; Merghem, Kamel; Guilet, Stéphane; Hostein, Richard; Voliotis, Valia

2018-02-01

We demonstrate systematic resonance fluorescence recovery with near-unity emission efficiency in single quantum dots embedded in a charge-tunable device in a wave-guiding geometry. The quantum dot charge state is controlled by a gate voltage, through carrier tunneling from a close-lying Fermi sea, stabilizing the resonantly photocreated electron-hole pair. The electric field cancels out the charging/discharging mechanisms from nearby traps toward the quantum dots, responsible for the usually observed inhibition of the resonant fluorescence. Fourier transform spectroscopy as a function of the applied voltage shows a strong increase in the coherence time though not reaching the radiative limit. These charge controlled quantum dots can act as quasi-perfect deterministic single-photon emitters, with one laser pulse converted into one emitted single photon.

Spectrum analysis of a voltage source converter due to semiconductor voltage drops

DEFF Research Database (Denmark)

Rasmussen, Tonny Wederberg; Eltouki, Mustafa

2017-01-01

It is known that power electronic voltage source converters are non-ideal. This paper presents a state-of-the-art review on the effect of semiconductor voltage drop on the output voltage spectrum, using single-phase H-bridge two-level converter topology with natural sampled pulse width modulation....... The paper describes the analysis of output voltage spectrum, when the semiconductor voltage drop is added. The results of the analysis of the spectral contribution including and excluding semiconductor voltage drop reveal a good agreement between the theoretical results, simulations and laboratory...

A stabilized MFE reduced-order extrapolation model based on POD for the 2D unsteady conduction-convection problem

Directory of Open Access Journals (Sweden)

Hong Xia

2017-05-01

Full Text Available Abstract In this study, we devote ourselves to establishing a stabilized mixed finite element (MFE reduced-order extrapolation (SMFEROE model holding seldom unknowns for the two-dimensional (2D unsteady conduction-convection problem via the proper orthogonal decomposition (POD technique, analyzing the existence and uniqueness and the stability as well as the convergence of the SMFEROE solutions and validating the correctness and dependability of the SMFEROE model by means of numerical simulations.

Optimal dynamic voltage scaling for wireless sensor nodes with real-time constraints

Science.gov (United States)

Cassandras, Christos G.; Zhuang, Shixin

2005-11-01

Sensors are increasingly embedded in manufacturing systems and wirelessly networked to monitor and manage operations ranging from process and inventory control to tracking equipment and even post-manufacturing product monitoring. In building such sensor networks, a critical issue is the limited and hard to replenish energy in the devices involved. Dynamic voltage scaling is a technique that controls the operating voltage of a processor to provide desired performance while conserving energy and prolonging the overall network's lifetime. We consider such power-limited devices processing time-critical tasks which are non-preemptive, aperiodic and have uncertain arrival times. We treat voltage scaling as a dynamic optimization problem whose objective is to minimize energy consumption subject to hard or soft real-time execution constraints. In the case of hard constraints, we build on prior work (which engages a voltage scaling controller at task completion times) by developing an intra-task controller that acts at all arrival times of incoming tasks. We show that this optimization problem can be decomposed into two simpler ones whose solution leads to an algorithm that does not actually require solving any nonlinear programming problems. In the case of soft constraints, this decomposition must be partly relaxed, but it still leads to a scalable (linear in the number of tasks) algorithm. Simulation results are provided to illustrate performance improvements in systems with intra-task controllers compared to uncontrolled systems or those using inter-task control.

Voltage harmonics mitigation through hybrid active power filer