Comparison of high-voltage ac and pulsed operation of a surface dielectric barrier discharge

International Nuclear Information System (INIS)

Williamson, James M; Trump, Darryl D; Bletzinger, Peter; Ganguly, Biswa N

2006-01-01

A surface dielectric barrier discharge (DBD) in atmospheric pressure air was excited either by low frequency (0.3-2 kHz) high-voltage ac or by short, high-voltage pulses at repetition rates from 50 to 600 pulses s -1 . The short-pulse excited discharge was more diffuse and did not have the pronounced bright multiple cathode spots observed in the ac excited discharge. The discharge voltage, current and average power deposited into the discharge were calculated for both types of excitation. As a measure of plasma-chemical efficiency, the ozone number density was measured by UV absorption as a function of average deposited power. The density of ozone produced by ac excitation did not increase so rapidly as that produced by short-pulse excitation as a function of average power, with a maximum measured density of ∼3 x 10 15 cm -3 at 25 W. The maximum ozone production achieved by short-pulse excitation was ∼8.5 x 10 15 cm -3 at 20 W, which was four times greater than that achieved by ac excitation at the same power level

An AMOLED AC-Biased Pixel Design Compensating the Threshold Voltage and I-R Drop

Directory of Open Access Journals (Sweden)

Ching-Lin Fan

2011-01-01

Full Text Available We propose a novel pixel design and an AC bias driving method for active-matrix organic light-emitting diode (AM-OLED displays using low-temperature polycrystalline silicon thin-film transistors (LTPS-TFTs. The proposed threshold voltage and I-R drop compensation circuit, which comprised three transistors and one capacitor, have been verified to supply uniform output current by simulation work using the Automatic Integrated Circuit Modeling Simulation Program with Integrated Circuit Emphasis (AIM-SPICE simulator. The simulated results demonstrate excellent properties such as low error rate of OLED anode voltage variation (<0.7% and low voltage drop of VDD power line. The proposed pixel circuit effectively enables threshold-voltage-deviation correction of driving TFT and compensates for the voltage drop of VDD power line using AC bias on OLED cathode.

A Switched Capacitor Based AC/DC Resonant Converter for High Frequency AC Power Generation

Directory of Open Access Journals (Sweden)

Cuidong Xu

2015-09-01

Full Text Available A switched capacitor based AC-DC resonant power converter is proposed for high frequency power generation output conversion. This converter is suitable for small scale, high frequency wind power generation. It has a high conversion ratio to provide a step down from high voltage to low voltage for easy use. The voltage conversion ratio of conventional switched capacitor power converters is fixed to n, 1/n or −1/n (n is the switched capacitor cell. In this paper, A circuit which can provide n, 1/n and 2n/m of the voltage conversion ratio is presented (n is stepping up the switched capacitor cell, m is stepping down the switching capacitor cell. The conversion ratio can be changed greatly by using only two switches. A resonant tank is used to assist in zero current switching, and hence the current spike, which usually exists in a classical switching switched capacitor converter, can be eliminated. Both easy operation and efficiency are possible. Principles of operation, computer simulations and experimental results of the proposed circuit are presented. General analysis and design methods are given. The experimental result verifies the theoretical analysis of high frequency AC power generation.

Approaches to building single-stage AC/AC conversion switch-mode audio power amplifiers

Energy Technology Data Exchange (ETDEWEB)

Ljusev, P.; Andersen, Michael A.E.

2005-07-01

This paper discusses the possible topologies and promising approaches towards direct single-phase AC-AC conversion of the mains voltage for audio applications. When compared to standard Class-D switching audio power amplifiers with a separate power supply, it is expected that direct conversion will provide better efficiency and higher level of integration, leading to lower component count, volume and cost, but at the expense of a minor performance deterioration. (au)

A Low-input-voltage Wireless Power Transfer for Biomedical Implants

DEFF Research Database (Denmark)

Jiang, Hao; Bai, Kangjun; Zhu, Weijie

2015-01-01

Wireless power transfer is an essential technology to increase implants' longevity. A pair of inductivelycoupled coils operating at radio-frequency is extensively used to deliver electrical power to implants wirelessly. In this system, a power conditioning circuit is required convert the induced...... in the rectifier for the efficient AC to DC conversion. This requirement results in larger coil size, shorter operating distance or more stringent geometrical alignment between the two coils. In this paper, a low-input-voltage wireless power transfer has been demonstrated. In this system, the opencircuit voltage...... time-varying AC power harvested by the receiving coil to a stable DC power that is needed for powering circuits and sensors. Most existing power conditioning circuits require the induced voltage of the receiving coil to be significantly higher than the turn-on voltage of the diodes used...

Induced AC voltages on pipelines may present a serious hazard

International Nuclear Information System (INIS)

Kirkpatrick, E.L.

1997-01-01

The problem of induced AC voltages on pipelines has always been with us. Early pipeline construction consisted of bare steel or cast iron pipe, which was very well grounded. Bell and spigot, mechanical, or dresser-style joint couplings often were used, creating electrically discontinuous pipelines which are less susceptible to AC induction. Although induced AC affects any pipeline parallel to a high-voltage alternating current (HVAC) power line, the effects were not noticeable on bare pipelines. With the advent of welded steel pipelines, modern cathodic protection (CP) methods and materials, and the vastly improved quality of protective coatings, induced AC effects on pipelines have become a significant consideration on many pipeline rights-of-way. In the last two to three decades, one has been seeing much more joint occupancy of the same right-of-way by one or more pipelines and power lines. As the cost of right-of-way and the difficulty in acquisition, particularly in urban areas, have risen, the concept of joint occupancy rights-of-way has become more attractive to many utility companies. Federal and state regulations usually insist on joint-use right-of-way when a utility proposes crossing regulated or publicly owned lands, wherever there is an existing easement. Such joint use allows the induced AC phenomena to occur and may create electrical hazards and interference to pipeline facilities. Underground pipelines are especially susceptible if they are well-coated and electrically isolated for CP

Autonomous power management for interlinked AC-DC microgrids

DEFF Research Database (Denmark)

Nutkani, Inam Ullah; Meegahapola, Lasantha; Andrew, Loh Poh Chiang

2018-01-01

of the DC micro-grid before importing power from the interlinked AC microgrid. This strategy enables voltage regulation in the DC microgrid, and also reduces the number of converters in operation. The proposed scheme is fully autonomous while it retains the plug-n-play features for generators and tie......The existing power management schemes for inter-linked AC-DC microgrids have several operational drawbacks. Some of the existing control schemes are designed with the main objective of sharing power among the interlinked microgrids based on their loading conditions, while other schemes regulate...... the voltage of the interlinked microgrids without considering the specific loading conditions. However, the existing schemes cannot achieve both objectives efficiently. To address these issues, an autonomous power management scheme is proposed, which explicitly considers the specific loading condition...

Power Electronic Transformer based Three-Phase PWM AC Drives

Science.gov (United States)

Basu, Kaushik

A Transformer is used to provide galvanic isolation and to connect systems at different voltage levels. It is one of the largest and most expensive component in most of the high voltage and high power systems. Its size is inversely proportional to the operating frequency. The central idea behind a power electronic transformer (PET) also known as solid state transformer is to reduce the size of the transformer by increasing the frequency. Power electronic converters are used to change the frequency of operation. Steady reduction in the cost of the semiconductor switches and the advent of advanced magnetic materials with very low loss density and high saturation flux density implies economic viability and feasibility of a design with high power density. Application of PET is in generation of power from renewable energy sources, especially wind and solar. Other important application include grid tied inverters, UPS e.t.c. In this thesis non-resonant, single stage, bi-directional PET is considered. The main objective of this converter is to generate adjustable speed and magnitude pulse width modulated (PWM) ac waveforms from an ac or dc grid with a high frequency ac link. The windings of a high frequency transformer contains leakage inductance. Any switching transition of the power electronic converter connecting the inductive load and the transformer requires commutation of leakage energy. Commutation by passive means results in power loss, decrease in the frequency of operation, distortion in the output voltage waveform, reduction in reliability and power density. In this work a source based partially loss-less commutation of leakage energy has been proposed. This technique also results in partial soft-switching. A series of converters with novel PWM strategies have been proposed to minimize the frequency of leakage inductance commutation. These PETs achieve most of the important features of modern PWM ac drives including 1) Input power factor correction, 2) Common

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)

Reconfigurable DC Links for Restructuring Existing Medium Voltage AC Distribution Grids

NARCIS (Netherlands)

Shekhar, A.; Ramirez Elizondo, L.M.; Feng, Xianyong; Kontos, E.; Bauer, P.

2018-01-01

While the scientific community recognizes the benefits of DC power transfer, the distribution network operators point out the practical and economic constraints in refurbishing the existing AC network at a medium-voltage level. Some apprehensions like reliability, cost of ownership, and safety in

A Secondary Voltage Control Method for an AC/DC Coupled Transmission System Based on Model Predictive Control

DEFF Research Database (Denmark)

Xu, Fengda; Guo, Qinglai; Sun, Hongbin

2015-01-01

For an AC/DC coupled transmission system, the change of transmission power on the DC lines will significantly influence the AC systems’ voltage. This paper describes a method to coordinated control the reactive power of power plants and shunt capacitors at DC converter stations nearby, in order t...

An AC/AC Direct Power Conversion Topology Having Multiple Power Grid Connections with Adjustable Loading

DEFF Research Database (Denmark)

Klumpner, Christian; Blaabjerg, Frede

2004-01-01

independent producers/consumers to connect to multiple distribution grids in order to optimise the electricity price, as this will vary during the day from one power distribution company to another one. It will be needed to have a load that can smoothly adjust the power consumed from each power grid in order......Normally, a power converter has one supply port to connect to the power grid and one or multiple output ports to connect to AC loads that require variable voltage and variable frequency. As the trend on the energy market is towards deregulation, new converter topologies are needed to allow...... to minimize the overall energy cost or in case of special applications, to improve the system redundancy. Also, having a generator that can simultaneously feed fractions of its power into multiple grids which are not coupled (different voltage, frequency, displacement angle) and continuously adjust...

A multi-channel AC power supply controller

International Nuclear Information System (INIS)

Su Hong; Li Xiaogang; Ma Xiaoli; Zhou Bo; Yin Weiwei

2003-01-01

A multi-channel ac power supply controller developed recently by authors is introduced briefly in this paper. This controller is a computer controlled multi-electronic-switch device. This controller was developed for the automatic control and monitoring system of a 220 V ac power supply system, it is a key front-end device of the automatic control and monitoring system. There is an electronic switch in each channel, the rated load power is ≤1 kW/each channel. Another function is to sample the 220 V ac output voltage so that computer can monitor the operation state of each electronic switch. Through these switches, the 220 V ac power supply is applied to some device or apparatus that need to be powered by 220 V ac power supply. In the design, a solid-state relay was employed as an electronic switch. This controller can be connected in cascade mode. There are 8 boxes at most can be connected in cascade mode. The length of control word is 8 bit, which contains addressing information and electronic switch state setting information. The sampling output of the controller is multiplexed. It is only one bit that indicates the operating state of an electronic switch. This controller has been used in an automatic control and monitoring system for 220 V ac power supply system

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.

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.

An improved power control strategy for hybrid AC-DC microgrids

DEFF Research Database (Denmark)

Baharizadeh, Mehdi; Karshenas, Hamid Reza; Guerrero, Josep M.

2018-01-01

This paper presents a new droop-based control strategy for hybrid microgrids (HMG) with improved power sharing. When ac microgrids (AC-MG) and dc microgrids (DC-MG) are present in a distribution grid, there is an opportunity to interconnect them via an interlinking converter (IC) and form a HMG......, the possibility of participation of IC in AC-MG reactive power adds some complexity to a HMG control system. In this paper, a new decentralized control strategy is presented for a HMG which relies on regulating the voltage magnitude of a common bus in each microgrid. In this regard, new droop characteristics...... for sources across both microgrids as well as IC are proposed. The proposed droop characteristics result in better active/reactive power sharing across both microgrids and at the same time results in better voltage regulation. The derivation of new droop characteristics is thoroughly discussed in this paper...

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.

A Circulating-Current Suppression Method for Parallel-Connected Voltage-Source Inverters With Common DC and AC Buses

DEFF Research Database (Denmark)

Wei, Baoze; Guerrero, Josep M.; Quintero, Juan Carlos Vasquez

2017-01-01

This paper presents a theoretical study with experimental validation of a circulating-current suppression method for parallel operation of three-phase voltage source inverters (VSI), which may be suitable for modular parallel uninterruptible power supply systems or hybrid AC/DC microgrid applicat......This paper presents a theoretical study with experimental validation of a circulating-current suppression method for parallel operation of three-phase voltage source inverters (VSI), which may be suitable for modular parallel uninterruptible power supply systems or hybrid AC/DC microgrid......, and added into the conventional droop plus virtual impedance control. In the control architecture, the reference voltages of the inverters are generated by the primary control loop which consists of a droop control and a virtual impedance. The secondary control is used to compensate the voltage drop...

Improved transistorized AC motor controller for battery powered urban electric passenger vehicles

Science.gov (United States)

Peak, S. C.

1982-01-01

An ac motor controller for an induction motor electric vehicle drive system was designed, fabricated, tested, evaluated, and cost analyzed. A vehicle performance analysis was done to establish the vehicle tractive effort-speed requirements. These requirements were then converted into a set of ac motor and ac controller requirements. The power inverter is a three-phase bridge using power Darlington transistors. The induction motor was optimized for use with an inverter power source. The drive system has a constant torque output to base motor speed and a constant horsepower output to maximum speed. A gear shifting transmission is not required. The ac controller was scaled from the base 20 hp (41 hp peak) at 108 volts dec to an expanded horsepower and battery voltage range. Motor reversal was accomplished by electronic reversal of the inverter phase sequence. The ac controller can also be used as a boost chopper battery charger. The drive system was tested on a dynamometer and results are presented. The current-controlled pulse width modulation control scheme yielded improved motor current waveforms. The ac controller favors a higher system voltage.

Transmission Technologies and Operational Characteristic Analysis of Hybrid UHV AC/DC Power Grids in China

Science.gov (United States)

Tian, Zhang; Yanfeng, Gong

2017-05-01

In order to solve the contradiction between demand and distribution range of primary energy resource, Ultra High Voltage (UHV) power grids should be developed rapidly to meet development of energy bases and accessing of large-scale renewable energy. This paper reviewed the latest research processes of AC/DC transmission technologies, summarized the characteristics of AC/DC power grids, concluded that China’s power grids certainly enter a new period of large -scale hybrid UHV AC/DC power grids and characteristics of “strong DC and weak AC” becomes increasingly pro minent; possible problems in operation of AC/DC power grids was discussed, and interaction or effect between AC/DC power grids was made an intensive study of; according to above problems in operation of power grids, preliminary scheme is summarized as fo llows: strengthening backbone structures, enhancing AC/DC transmission technologies, promoting protection measures of clean energ y accessing grids, and taking actions to solve stability problems of voltage and frequency etc. It’s valuable for making hybrid UHV AC/DC power grids adapt to operating mode of large power grids, thus guaranteeing security and stability of power system.

Moderately nonlinear diffuse-charge dynamics under an ac voltage.

Science.gov (United States)

Stout, Robert F; Khair, Aditya S

2015-09-01

The response of a symmetric binary electrolyte between two parallel, blocking electrodes to a moderate amplitude ac voltage is quantified. The diffuse charge dynamics are modeled via the Poisson-Nernst-Planck equations for a dilute solution of point-like ions. The solution to these equations is expressed as a Fourier series with a voltage perturbation expansion for arbitrary Debye layer thickness and ac frequency. Here, the perturbation expansion in voltage proceeds in powers of V_{o}/(k_{B}T/e), where V_{o} is the amplitude of the driving voltage and k_{B}T/e is the thermal voltage with k_{B} as Boltzmann's constant, T as the temperature, and e as the fundamental charge. We show that the response of the electrolyte remains essentially linear in voltage amplitude at frequencies greater than the RC frequency of Debye layer charging, D/λ_{D}L, where D is the ion diffusivity, λ_{D} is the Debye layer thickness, and L is half the cell width. In contrast, nonlinear response is predicted at frequencies below the RC frequency. We find that the ion densities exhibit symmetric deviations from the (uniform) equilibrium density at even orders of the voltage amplitude. This leads to the voltage dependence of the current in the external circuit arising from the odd orders of voltage. For instance, the first nonlinear contribution to the current is O(V_{o}^{3}) which contains the expected third harmonic but also a component oscillating at the applied frequency. We use this to compute a generalized impedance for moderate voltages, the first nonlinear contribution to which is quadratic in V_{o}. This contribution predicts a decrease in the imaginary part of the impedance at low frequency, which is due to the increase in Debye layer capacitance with increasing V_{o}. In contrast, the real part of the impedance increases at low frequency, due to adsorption of neutral salt from the bulk to the Debye layer.

Moderately nonlinear diffuse-charge dynamics under an ac voltage

Science.gov (United States)

Stout, Robert F.; Khair, Aditya S.

2015-09-01

The response of a symmetric binary electrolyte between two parallel, blocking electrodes to a moderate amplitude ac voltage is quantified. The diffuse charge dynamics are modeled via the Poisson-Nernst-Planck equations for a dilute solution of point-like ions. The solution to these equations is expressed as a Fourier series with a voltage perturbation expansion for arbitrary Debye layer thickness and ac frequency. Here, the perturbation expansion in voltage proceeds in powers of Vo/(kBT /e ) , where Vo is the amplitude of the driving voltage and kBT /e is the thermal voltage with kB as Boltzmann's constant, T as the temperature, and e as the fundamental charge. We show that the response of the electrolyte remains essentially linear in voltage amplitude at frequencies greater than the RC frequency of Debye layer charging, D /λDL , where D is the ion diffusivity, λD is the Debye layer thickness, and L is half the cell width. In contrast, nonlinear response is predicted at frequencies below the RC frequency. We find that the ion densities exhibit symmetric deviations from the (uniform) equilibrium density at even orders of the voltage amplitude. This leads to the voltage dependence of the current in the external circuit arising from the odd orders of voltage. For instance, the first nonlinear contribution to the current is O (Vo3) which contains the expected third harmonic but also a component oscillating at the applied frequency. We use this to compute a generalized impedance for moderate voltages, the first nonlinear contribution to which is quadratic in Vo. This contribution predicts a decrease in the imaginary part of the impedance at low frequency, which is due to the increase in Debye layer capacitance with increasing Vo. In contrast, the real part of the impedance increases at low frequency, due to adsorption of neutral salt from the bulk to the Debye layer.

Power Controllability of Three-phase Converter with Unbalanced AC Source

DEFF Research Database (Denmark)

Ma, Ke; Liserre, Marco; Blaabjerg, Frede

2013-01-01

Three-phase DC-AC power converters suffer from power oscillation and overcurrentt problems in case of unbalanced AC source voltage that can be caused by grid/generator faults. Existing solutions to handle these problems are properly selecting and controlling the positive and negative sequence...... currents. In this work a new series of control strategies which utilize the zero-sequence components are proposed to enhance the power control ability under this adverse conditions. It is concluded that by introducing proper zero sequence current controls and corresponding circuit configurations, the power...... converter can enable more flexible control targets, achieving better performances in the delivered power and load current when suffering from unbalanced AC sources....

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

DEFF Research Database (Denmark)

Zhao, Xin; Meng, Lexuan; Dragicevic, Tomislav

2015-01-01

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

DC injection into low voltage AC networks

Energy Technology Data Exchange (ETDEWEB)

NONE

2005-07-01

This report summarises the results of a study investigating the impact of levels of injected DC current injections on a low voltage AC distribution network systems in order to recommend acceptable limits of DC from microgeneration. Relevant literature is reviewed, and the impact of DC levels in distribution transformers, transformer modelling, and instrumental transformers are discussed. The impact of DC in residual current devices (RCD) and in domestic electricity watt hour meters is examined along with DC enhanced corrosion, corrosion failure, and the measurement of DC current injection. Sources of DC injection outlined include DC from computer power supplies, network faults, geomagnetic phenomena, lighting circuits/dimmers, and embedded generators.

Common-mode Voltage Reduction in a Motor Drive System with a Power Factor Correction

DEFF Research Database (Denmark)

Adabi, J.; Boora, A.A.; Zare, F.

2012-01-01

Common-mode voltage generated by a power converter in combination with parasitic capacitive couplings is a potential source of shaft voltage in an AC motor drive system. In this study, a three-phase motor drive system supplied with a single-phase AC-DC diode rectifier is investigated in order...... to reduce shaft voltage in a three-phase AC motor drive system. In this topology, the AC-DC diode rectifier influences the common-mode voltage generated by the inverter because the placement of the neutral point is changing in different rectifier circuit states. A pulse width modulation technique...

High Operating Voltage Supercapacitor Using PPy/AC Composite Electrode Based on Simple Dipping Method

Directory of Open Access Journals (Sweden)

Kyoungho Kim

2015-01-01

Full Text Available As various wearable devices are emerging, self-generated power sources, such as piezoelectric generators, triboelectric generators, and thermoelectric generators, are of interest. To adapt self-generated power sources for application devices, a supercapacitor is necessary because of the short generation times (1–10 ms and low generated power (1–100 μW of self-generated power sources. However, to date, supercapacitors are too large to be adapted for wearable devices. There have been many efforts to reduce the size of supercapacitors by using polypyrrole (PPy for high energy supercapacitor electrodes. However, these supercapacitors have several disadvantages, such as a low operating voltage due to the use of an aqueous electrolyte, and complex manufacturing methods, such as the hydrogel and aerosol methods. In particular, the low operating voltage (~1.0 V is a significant issue because most electronic components operate above 3.0 V. In this study, we successfully demonstrated the high operating voltage (3.0 V of a supercapacitor using a PPy/activated carbon (AC composite electrode based on the chemical polymerization of the PPy by simple dipping. In addition, a twofold enhancement of its energy density was achieved compared with conventional supercapacitors using AC electrodes.

Improving Power Quality in AC Supply Grids

Directory of Open Access Journals (Sweden)

Piotr Fabijański

2015-12-01

Full Text Available This paper describes a digital and actual model of the UPQC (Unified Power Quality Conditioner integrated system for power quality improvement. The UPQC’s design and its connection to an AC supply grid, 1-phase and 3-phase alike, provide effective compensation of unwanted interferences in the waveforms of load supply voltages and non-linear load currents. This article presents an overview of topologies and control strategies. The study of the UPQC confirmed its positive impact on the power quality. The electricity parameters were significantly improved. Total harmonic distortion in supply voltage THDu decreased six-fold to 1.89%, and total harmonic distortion in load current THDi decreased more than ten-fold to 2.38% for a non-linear load (uncontrolled bridge rectifier with load L. Additionally, symmetrisation of supply voltages and reactive power compensation Q of linear load was obtained. The UPQC integrated system for power quality improvement can be used wherever high-quality and PN-EN 50160 standard – compliant electricity is required.

Improved Design Methods for Robust Single- and Three-Phase ac-dc-ac Power Converters

DEFF Research Database (Denmark)

Qin, Zian

. The approaches for improving their performance, in terms of the voltage stress, efficiency, power density, cost, loss distribution, and temperature, will be studied. The structure of the thesis is as follows, Chapter 1 presents the introduction and motivation of the whole project as well as the background...... becomes a emerging challenge. Accordingly, installation of sustainable power generators like wind turbines and solar panels has experienced a large increase during the last decades. Meanwhile, power electronics converters, as interfaces in electrical system, are delivering approximately 80 % electricity...... back-to-back, and meanwhile improve the harmonics, control flexibility, and thermal distribution between the switches. Afterwards, active power decoupling methods for single-phase inverters or rectifiers that are similar to the single-phase ac-dc-ac converter, are studied in Chapter 4...

Safe-commutation principle for direct single-phase AC-AC converters for use in audio power amplification

Energy Technology Data Exchange (ETDEWEB)

Ljusev, P.; Andersen, Michael A.E.

2005-07-01

This paper presents an alternative safe commutation principle for a single phase bidirectional bridge, for use in the new generation of direct single-stage AC-AC audio power amplifiers. As compared with the bridge commutation with load current or source voltage sensing, in this approach it is not required to do any measurements, thus making it more reliable. Initial testing made on the prototype prove the feasibility of the approach. (au)

AC Voltage Control of DC/DC Converters Based on Modular Multilevel Converters in Multi-Terminal High-Voltage Direct Current Transmission Systems

Directory of Open Access Journals (Sweden)

Rui Li

2016-12-01

Full Text Available The AC voltage control of a DC/DC converter based on the modular multilevel converter (MMC is considered under normal operation and during a local DC fault. By actively setting the AC voltage according to the two DC voltages of the DC/DC converter, the modulation index can be near unity, and the DC voltage is effectively utilized to output higher AC voltage. This significantly decreases submodule (SM capacitance and conduction losses of the DC/DC converter, yielding reduced capital cost, volume, and higher efficiency. Additionally, the AC voltage is limited in the controllable range of both the MMCs in the DC/DC converter; thus, over-modulation and uncontrolled currents are actively avoided. The AC voltage control of the DC/DC converter during local DC faults, i.e., standby operation, is also proposed, where only the MMC connected on the faulty cable is blocked, while the other MMC remains operational with zero AC voltage output. Thus, the capacitor voltages can be regulated at the rated value and the decrease of the SM capacitor voltages after the blocking of the DC/DC converter is avoided. Moreover, the fault can still be isolated as quickly as the conventional approach, where both MMCs are blocked and the DC/DC converter is not exposed to the risk of overcurrent. The proposed AC voltage control strategy is assessed in a three-terminal high-voltage direct current (HVDC system incorporating a DC/DC converter, and the simulation results confirm its feasibility.

High Voltage AC underground cable systems for power transmission

DEFF Research Database (Denmark)

Bak, Claus Leth; Silva, Filipe Miguel Faria da

2016-01-01

researching electrical engineering topics related to using underground cables for power transmission at EHV level and including the 420 kV level. The research topics were laid down by ET/AAU and Energinet.dk in the DANPAC (DANish Power systems with AC Cables) research project. The main topics are discussed...... on the basis of 39 references published by ET/AAU and Energinet.dk. Part I of the paper explains the events that lead to the research project, reactive power compensation, modelling for transient studies, including field measurements and improvements to the existing models, and temporary overvoltages due...... to resonances. Part II covers transient phenomena, harmonics in cables, system modelling for different phenomena, main and backup protections in cable-based networks, online fault detection and future trends....

High Voltage AC underground cable systems for power transmission

DEFF Research Database (Denmark)

Bak, Claus Leth; Silva, Filipe Miguel Faria da

2016-01-01

researching electrical engineering topics related to using underground cables for power transmission at EHV level and including the 420 kV level. The research topics were laid down by ET/AAU and Energinet.dk in the DANPAC (DANish Power systems with Ac Cables) research project. The main topics are discussed...... on the basis of 39 references published by ET/AAU and Energinet.dk. Part I of the paper explains the events that lead to the research project, reactive power compensation, modelling for transient studies, including field measurements and improvements to the existing models, and temporary overvoltages due...... to resonances. Part II covers transient phenomena, harmonics in cables, system modelling for different phenomena, main and backup protections in cable-based networks, online fault detection and future trends....

Mitigating voltage lead errors of an AC Josephson voltage standard by impedance matching

Science.gov (United States)

Zhao, Dongsheng; van den Brom, Helko E.; Houtzager, Ernest

2017-09-01

A pulse-driven AC Josephson voltage standard (ACJVS) generates calculable AC voltage signals at low temperatures, whereas measurements are performed with a device under test (DUT) at room temperature. The voltage leads cause the output voltage to show deviations that scale with the frequency squared. Error correction mechanisms investigated so far allow the ACJVS to be operational for frequencies up to 100 kHz. In this paper, calculations are presented to deal with these errors in terms of reflected waves. Impedance matching at the source side of the system, which is loaded with a high-impedance DUT, is proposed as an accurate method to mitigate these errors for frequencies up to 1 MHz. Simulations show that the influence of non-ideal component characteristics, such as the tolerance of the matching resistor, the capacitance of the load input impedance, losses in the voltage leads, non-homogeneity in the voltage leads, a non-ideal on-chip connection and inductors between the Josephson junction array and the voltage leads, can be corrected for using the proposed procedures. The results show that an expanded uncertainty of 12 parts in 106 (k  =  2) at 1 MHz and 0.5 part in 106 (k  =  2) at 100 kHz is within reach.

Multi-phase AC/AC step-down converter for distribution systems

Science.gov (United States)

Aeloiza, Eddy C.; Burgos, Rolando P.

2017-10-25

A step-down AC/AC converter for use in an electric distribution system includes at least one chopper circuit for each one of a plurality of phases of the AC power, each chopper circuit including a four-quadrant switch coupled in series between primary and secondary sides of the chopper circuit and a current-bidirectional two-quadrant switch coupled between the secondary side of the chopper circuit and a common node. Each current-bidirectional two-quadrant switch is oriented in the same direction, with respect to the secondary side of the corresponding chopper circuit and the common node. The converter further includes a control circuit configured to pulse-width-modulate control inputs of the switches, to convert a first multiphase AC voltage at the primary sides of the chopper circuits to a second multiphase AC voltage at the secondary sides of the chopper circuits, the second multiphase AC voltage being lower in voltage than the first multiphase AC voltage.

Power sharing algorithm for vector controlled six-phase AC motor with four customary three-phase voltage source inverter drive

DEFF Research Database (Denmark)

Padmanaban, Sanjeevikumar; Grandi, Gabriele; Blaabjerg, Frede

2015-01-01

This paper considered a six-phase (asymmetrical) induction motor, kept 30 phase displacement between two set of three-phase open-end stator windings configuration. The drive system consists of four classical three-phase voltage inverters (VSIs) and all four dc sources are deliberately kept isolated......) by nearest three vectors (NTVs) approach is adopted to regulate each couple of VSIs. The proposed power sharing algorithm is verified by complete numerical simulation modeling (Matlab/ Simulink-PLECS software) of whole ac drive system by observing the dynamic behaviors in different designed condition. Set...

Development of software to improve AC power quality on large spacecraft

Science.gov (United States)

Kraft, L. Alan

1991-01-01

To insure the reliability of a 20 kHz, alternating current (AC) power system on spacecraft, it is essential to analyze its behavior under many adverse operating conditions. Some of these conditions include overloads, short circuits, switching surges, and harmonic distortions. Harmonic distortions can become a serious problem. It can cause malfunctions in equipment that the power system is supplying, and, during distortions such as voltage resonance, it can cause equipment and insulation failures due to the extreme peak voltages. To address the harmonic distortion issue, work was begun under the 1990 NASA-ASEE Summer Faculty Fellowship Program. Software, originally developed by EPRI, called HARMFLO, a power flow program capable of analyzing harmonic conditions on three phase, balanced, 60 Hz AC power systems, was modified to analyze single phase, 20 kHz, AC power systems. Since almost all of the equipment used on spacecraft power systems is electrically different from equipment used on terrestrial power systems, it was also necessary to develop mathematical models for the equipment to be used on the spacecraft. The modelling was also started under the same fellowship work period. Details of the modifications and models completed during the 1990 NASA-ASEE Summer Faculty Fellowship Program can be found in a project report. As a continuation of the work to develop a complete package necessary for the full analysis of spacecraft AC power system behavior, deployment work has continued through NASA Grant NAG3-1254. This report details the work covered by the above mentioned grant.

Conventional P-ω/Q-V Droop Control in Highly Resistive Line of Low-Voltage Converter-Based AC Microgrid

Directory of Open Access Journals (Sweden)

Xiaochao Hou

2016-11-01

Full Text Available In low-voltage converter-based alternating current (AC microgrids with resistive distribution lines, the P-V droop with Q-f boost (VPD/FQB is the most common method for load sharing. However, it cannot achieve the active power sharing proportionally. To overcome this drawback, the conventional P-ω/Q-V droop control is adopted in the low-voltage AC microgrid. As a result, the active power sharing among the distributed generators (DGs is easily obtained without communication. More importantly, this study clears up the previous misunderstanding that conventional P-ω/Q-V droop control is only applicable to microgrids with highly inductive lines, and lays a foundation for the application of conventional droop control under different line impedances. Moreover, in order to guarantee the accurate reactive power sharing, a guide for designing Q-V droop gains is given, and virtual resistance is adopted to shape the desired output impedance. Finally, the effects of power sharing and transient response are verified through simulations and experiments in converter-based AC Microgrid.

On-Site Measurements for Voltage Unbalance Studies Associated with the AC Railway Operation

DEFF Research Database (Denmark)

Stamatopoulos, Athanasios; Silva, Filipe Miguel Faria da; Bak, Claus Leth

2017-01-01

unbalance with regards to traction loads has been augmented since the decision to expand the electric railway. Towards this direction, and on the occasion of a newly built electrified line, voltage unbalance measurements were carried out and are presented in this paper. The information from the extracted......On-site measurements in Electrical Power Systems can provide valuable information about the performance of the network and also, can be of great assistance to the validation and assessment of simulation models developed for power system studies. Lately, the noticeable increase of non......-conventional types of loads, such as the AC railway, has raised concerns regarding the secure operation of power transmission networks. This renders the monitoring and reporting of various aspects of system’s power quality even more necessary. For the Danish transmission grid, in particular, the relevance of voltage...

Surge currents and voltages at the low voltage power mains during lightning strike to a GSM tower

Energy Technology Data Exchange (ETDEWEB)

Markowska, Renata [Bialystok Technical University (Poland)], E-mail: remark@pb.edu.pl

2007-07-01

The paper presents the results of numerical calculations of lightning surge currents and voltages in the low voltage power mains system connected to a free standing GSM base station. Direct lightning strike to GSM tower was studied. The analysis concerned the current that flows to the transformer station through AC power mains, the potential difference between the grounding systems of the GSM and the transformer stations and the voltage differences between phase and PE conductors of the power mains underground cable at both the GSM and the transformer sides. The calculations were performed using a numerical program based on the electromagnetic field theory and the method of moments. (author)

Isolated PWM DC-AC SICAM with an active capacitive voltage clamp[Pulse Density Modulated; Pulse Width Modulation

Energy Technology Data Exchange (ETDEWEB)

Ljusev, P.

2004-03-15

In this report an isolated PWM DC-AC SICAM with an active capacitive voltage clamp is presented. AC-DC power supply is implemented in its simplest form: diode rectifier followed by a medium-size charge-storage capacitors and possibly with an EMC filter on the mains entrance. Isolation from the AC mains is achieved using a high frequency (HF) transformer, whose voltages are not audio-modulated. The latter simplifies the design and is expected to have many advantages over the approach where the transformer voltages are modulated in regards to the audio signal reference. Input stage is built as a DC-AC inverter (push-pull, half-bridge or a full-bridge) and operated with 50% duty cycle, with all the challenges to avoid transformer saturation and obtain symmetrical operation. On the secondary side the output section is implemented as rectifier+inverter AC-AC stage, i.e. a true bidirectional bridge, which operation is aimed towards amplification of the audio signal. In order to solve the problem with the commutation of the load current, a dead time between the incoming and outgoing bidirectional switch is implemented, while a capacitive voltage clamp is used to keep the induced overvoltage to reasonable levels. The energy stored in the clamping capacitor is not wasted as in the dissipative clamps, but is rather transferred back to the primary side for further processing using an auxiliary isolated single-switch converter, i.e. an active clamping technique is used. (au)

Intertied ac–ac microgrids with autonomous power import and export

DEFF Research Database (Denmark)

Nutkani, Inam Ullah; Loh, Poh Chiang; Wang, Peng

2015-01-01

Intertied ac–ac microgrids offer many potential benefits like flexible frequency and voltage selection, reserve sharing and enhanced supply reliability. Operating them is however challenging due to their larger size and presence of more power converters with different responsibilities. These comp...

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)

A novel wireless power and data transmission AC to DC converter for an implantable device.

Science.gov (United States)

Liu, Jhao-Yan; Tang, Kea-Tiong

2013-01-01

This article presents a novel AC to DC converter implemented by standard CMOS technology, applied for wireless power transmission. This circuit combines the functions of the rectifier and DC to DC converter, rather than using the rectifier to convert AC to DC and then supplying the required voltage with regulator as in the transitional method. This modification can reduce the power consumption and the area of the circuit. This circuit also transfers the loading condition back to the external circuit by the load shift keying(LSK), determining if the input power is not enough or excessive, which increases the efficiency of the total system. The AC to DC converter is fabricated with the TSMC 90nm CMOS process. The circuit area is 0.071mm(2). The circuit can produce a 1V DC voltage with maximum output current of 10mA from an AC input ranging from 1.5V to 2V, at 1MHz to 10MHz.

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

Design study of an AC power supply system in JT-60SA

International Nuclear Information System (INIS)

Shimada, Katsuhiro; Baulaigue, Olivier; Cara, Philippe; Coletti, Alberto; Coletti, Roberto; Matsukawa, Makoto; Terakado, Tsunehisa; Yamauchi, Kunihito

2011-01-01

In the initial research phase of JT-60SA, which is the International Thermonuclear Experimental Reactor (ITER) satellite Tokamak with superconducting toroidal and poloidal magnetic field coils, the plasma heating operation of 30 MW-60 s or 20 MW-100 s is planned for 5.5 MA single null divertor plasmas. To achieve this operation, AC power source of the medium voltage of 18 kV and ∼7 GJ has to be provided in total to the poloidal field coil power supplies and additional heating devices such as neutral beam injection (NBI) and electron cyclotron radio frequency (ECRF). In this paper, the proposed AC power supply system in JT-60SA was estimated from the view point of available power, and harmonic currents based on the standard plasma operation scenario during the initial research phase. This AC power supply system consists of the reused JT-60 power supply facilities including motor generators with flywheel, AC breakers, harmonic filters, etc., to make it cost effective. In addition, the conceptual design of the upgraded AC power supply system for the ultimate heating power of 41 MW-100 s in the extended research phase is also described.

Electrical actuation of electrically conducting and insulating droplets using ac and dc voltages

International Nuclear Information System (INIS)

Kumari, N; Bahadur, V; Garimella, S V

2008-01-01

Electrical actuation of liquid droplets at the microscale offers promising applications in the fields of microfluidics and lab-on-chip devices. Much prior research has targeted the electrical actuation of electrically conducting liquid droplets using dc voltages (classical electrowetting). Electrical actuation of conducting droplets using ac voltages and the actuation of insulating droplets (using dc or ac voltages) has remained relatively unexplored. This paper utilizes an energy-minimization-based analytical framework to study the electrical actuation of a liquid droplet (electrically conducting or insulating) under ac actuation. It is shown that the electromechanical regimes of classical electrowetting, electrowetting under ac actuation and insulating droplet actuation can be extracted from the generic electromechanical actuation framework, depending on the electrical properties of the droplet, the underlying dielectric layer and the frequency of the actuation voltage. This paper also presents experiments which quantify the influence of the ac frequency and the electrical properties of the droplet on its velocity under electrical actuation. The velocities of droplets moving between two parallel plates under ac actuation are experimentally measured; these velocities are then related to the actuation force on the droplet which is predicted by the electromechanical model developed in this work. It is seen that the droplet velocities are strongly dependent on the frequency of the ac actuation voltage; the cut-off ac frequency, above which the droplet fails to actuate, is experimentally determined and related to the electrical conductivity of the liquid. This paper then analyzes and directly compares the various electromechanical regimes for the actuation of droplets in microfluidic applications

Conventional P-ω/Q-V Droop Control in Highly Resistive Line of Low-Voltage Converter-Based AC Microgrid

DEFF Research Database (Denmark)

Hou, Xiaochao; Sun, Yao; Yuan, Wenbin

2016-01-01

-ω/Q-V droop control is adopted in the low-voltage AC microgrid. As a result, the active power sharing among the distributed generators (DGs) is easily obtained without communication. More importantly, this study clears up the previous misunderstanding that conventional P-ω/Q-V droop control is only applicable...... to microgrids with highly inductive lines, and lays a foundation for the application of conventional droop control under different line impedances. Moreover, in order to guarantee the accurate reactive power sharing, a guide for designing Q-V droop gains is given, and virtual resistance is adopted to shape......In low-voltage converter-based alternating current (AC) microgrids with resistive distribution lines, the P-V droop with Q-f boost (VPD/FQB) is the most common method for load sharing. However, it cannot achieve the active power sharing proportionally. To overcome this drawback, the conventional P...

Analysis and Assessment of Operation Risk for Hybrid AC/DC Power System based on the Monte Carlo Method

Science.gov (United States)

Hu, Xiaojing; Li, Qiang; Zhang, Hao; Guo, Ziming; Zhao, Kun; Li, Xinpeng

2018-06-01

Based on the Monte Carlo method, an improved risk assessment method for hybrid AC/DC power system with VSC station considering the operation status of generators, converter stations, AC lines and DC lines is proposed. According to the sequential AC/DC power flow algorithm, node voltage and line active power are solved, and then the operation risk indices of node voltage over-limit and line active power over-limit are calculated. Finally, an improved two-area IEEE RTS-96 system is taken as a case to analyze and assessment its operation risk. The results show that the proposed model and method can intuitively and directly reflect the weak nodes and weak lines of the system, which can provide some reference for the dispatching department.

Analysis and Assessment of Operation Risk for Hybrid AC/DC Power System based on the Monte Carlo Method

Directory of Open Access Journals (Sweden)

Hu Xiaojing

2018-01-01

Full Text Available Based on the Monte Carlo method, an improved risk assessment method for hybrid AC/DC power system with VSC station considering the operation status of generators, converter stations, AC lines and DC lines is proposed. According to the sequential AC/DC power flow algorithm, node voltage and line active power are solved, and then the operation risk indices of node voltage over-limit and line active power over-limit are calculated. Finally, an improved two-area IEEE RTS-96 system is taken as a case to analyze and assessment its operation risk. The results show that the proposed model and method can intuitively and directly reflect the weak nodes and weak lines of the system, which can provide some reference for the dispatching department.

Space Charge Modulated Electrical Breakdown of Oil Impregnated Paper Insulation Subjected to AC-DC Combined Voltages

Directory of Open Access Journals (Sweden)

Yuanwei Zhu

2018-06-01

Full Text Available Based on the existing acknowledgment that space charge modulates AC and DC breakdown of insulating materials, this investigation promotes the related investigation into the situations of more complex electrical stress, i.e., AC-DC combined voltages. Experimentally, the AC-DC breakdown characteristics of oil impregnated paper insulation were systematically investigated. The effects of pre-applied voltage waveform, AC component ratio, and sample thickness on AC-DC breakdown characteristics were analyzed. After that, based on an improved bipolar charge transport model, the space charge profiles and the space charge induced electric field distortion during AC-DC breakdown were numerically simulated to explain the differences in breakdown characteristics between the pre-applied AC and pre-applied DC methods under AC-DC combined voltages. It is concluded that large amounts of homo-charges are accumulated during AC-DC breakdown, which results in significantly distorted inner electric field, leading to variations of breakdown characteristics of oil impregnated paper insulation. Therefore, space charges under AC-DC combined voltages must be considered in the design of converter transformers. In addition, this investigation could provide supporting breakdown data for insulation design of converter transformers and could promote better understanding on the breakdown mechanism of insulating materials subjected to AC-DC combined voltages.

Coordinated Reactive Power and Voltage Management for Offshore Wind Farms with AC-connection

DEFF Research Database (Denmark)

Heussen, Kai

2008-01-01

This paper analyzes voltage and reactive power in a wind farm in dependence on switchable shunt and tap-changer settings in connection with the control ranges of flexible reactive power sources. Attention is paid to their interdependent effects on central control variables, such as voltage...... in the collection grid, reactive power exported to the grid and internal active power losses. An aggregated steady-state model of an offshore wind farm is presented and a reduced mathematical representation suitable for symbolic analysis is developed. A coordination scheme is proposed to coordinate fast continuous...... control inputs with slow tap-changing devices using a short-term prediction. The proposed scheme is aimed at balancing cost factors such as wear of switching components, active power loss within the wind farm and STATCOM capacity....

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

Directory of Open Access Journals (Sweden)

M.R. Banaei

2014-09-01

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

Optimum voltage of auxiliary systems for thermal and nuclear power plants

International Nuclear Information System (INIS)

Tokumitsu, Iwao; Segawa, Motomichi

1979-01-01

In the power plants in Japan, their unit power output has been greatly enhanced since the introduction of new powerful thermal power plants from 1950's to 1960's. In both thermal and nuclear power plants, 1,000 MW machines have been already in operation. The increase of unit power output results in the increase of in-plant load capacity. Of these the voltage adopted for in-plant low voltage systems is now mainly 440 V at load terminals, and the voltage for in-plant high voltage systems has been changing to 6 kV level via 3 kV and 4 kV levels. As plant capacity increases, the load of low voltage systems significantly increases, and it is required to raise the voltage of 400 V level. By the way, the low voltage in AC is specified to be not higher than 600 V. This makes the change within the above range comparatively easy. Considering these conditions, it is recommended to change the voltage for low voltage systems to 575 V at power source terminals and 550 V at load terminals. Some merits in constructing power systems and in economy by raising the voltage were examined. Though demerits are also found, they are only about 15% of total merits. The most advantageous point in raising the voltage is to be capable of increasing the supplying range to low voltage system loads. (Wakatsuki, Y.)

Multilayered Functional Insulation System (MFIS) for AC Power Transmission in High Voltage Hybrid Electrical Propulsion

Science.gov (United States)

Lizcano, Maricela

2017-01-01

High voltage hybrid electric propulsion systems are now pushing new technology development efforts for air transportation. A key challenge in hybrid electric aircraft is safe high voltage distribution and transmission of megawatts of power (>20 MW). For the past two years, a multidisciplinary materials research team at NASA Glenn Research Center has investigated the feasibility of distributing high voltage power on future hybrid electric aircraft. This presentation describes the team's approach to addressing this challenge, significant technical findings, and next steps in GRC's materials research effort for MW power distribution on aircraft.

A Generalised Fault Protection Structure Proposed for Uni-grounded Low-Voltage AC Microgrids

Science.gov (United States)

Bui, Duong Minh; Chen, Shi-Lin; Lien, Keng-Yu; Jiang, Jheng-Lun

2016-04-01

This paper presents three main configurations of uni-grounded low-voltage AC microgrids. Transient situations of a uni-grounded low-voltage (LV) AC microgrid (MG) are simulated through various fault tests and operation transition tests between grid-connected and islanded modes. Based on transient simulation results, available fault protection methods are proposed for main and back-up protection of a uni-grounded AC microgrid. In addition, concept of a generalised fault protection structure of uni-grounded LVAC MGs is mentioned in the paper. As a result, main contributions of the paper are: (i) definition of different uni-grounded LVAC MG configurations; (ii) analysing transient responses of a uni-grounded LVAC microgrid through line-to-line faults, line-to-ground faults, three-phase faults and a microgrid operation transition test, (iii) proposing available fault protection methods for uni-grounded microgrids, such as: non-directional or directional overcurrent protection, under/over voltage protection, differential current protection, voltage-restrained overcurrent protection, and other fault protection principles not based on phase currents and voltages (e.g. total harmonic distortion detection of currents and voltages, using sequence components of current and voltage, 3I0 or 3V0 components), and (iv) developing a generalised fault protection structure with six individual protection zones to be suitable for different uni-grounded AC MG configurations.

Coordinated Control Scheme for Ancillary Services from Offshore Wind Power Plants to AC and DC Grids

DEFF Research Database (Denmark)

Sakamuri, Jayachandra N.; Altin, Müfit; Hansen, Anca Daniela

2016-01-01

This paper proposes a new approach of providing ancillary services to AC and DC grids from offshore wind power plants (OWPPs), connected through multi-terminal HVDC network. A coordinated control scheme where OWPP’s AC grid frequency modulated according to DC grid voltage variations is used...... to detect and provide the ancillary service requirements of both AC and DC grids, is proposed in this paper. In particular, control strategies for onshore frequency control, fault ridethrough support in the onshore grid, and DC grid voltage control are considered. The proposed control scheme involves only...

Analytical solution of the PNP equations at AC applied voltage

International Nuclear Information System (INIS)

Golovnev, Anatoly; Trimper, Steffen

2012-01-01

A symmetric binary polymer electrolyte subjected to an AC voltage is considered. The analytical solution of the Poisson–Nernst–Planck equations (PNP) is found and analyzed for small applied voltages. Three distinct time regimes offering different behavior can be discriminated. The experimentally realized stationary behavior is discussed in detail. An expression for the external current is derived. Based on the theoretical result a simple method is suggested of measuring the ion mobility and their concentration separately. -- Highlights: ► Analytical solution of Poisson–Nernst–Planck equations. ► Binary polymer electrolyte subjected to an external AC voltage. ► Three well separated time scales exhibiting different behavior. ► The experimentally realized stationary behavior is discussed in detail. ► A method is proposed measuring the mobility and the concentration separately.

Voltage-probe-position dependence and magnetic-flux contribution to the measured voltage in ac transport measurements: which measuring circuit determines the real losses?

International Nuclear Information System (INIS)

Pe, T.; McDonald, J.; Clem, J.R.

1995-01-01

The voltage V ab measured between two voltage taps a and b during magnetic flux transport in a type-II superconductor carrying current I is the sum of two contributions, the line integral from a to b of the electric field along an arbitrary path C s through the superconductor and a term proportional to the time rate of change of magnetic flux through the area bounded by the path C s and the measuring circuit leads. When the current I(t) is oscillating with time t, the apparent ac loss (the time average of the product IV ab ) depends upon the measuring circuit used. Only when the measuring-circuit leads are brought out far from the surface does the apparent power dissipation approach the real (or true) ac loss associated with the length of sample probed. Calculations showing comparisons between the apparent and real ac losses in a flat strip of rectangular cross section will be presented, showing the behavior as a function of the measuring-circuit dimensions. Corresponding calculations also are presented for a sample of elliptical cross section

New internal multi-range resistors for ac voltage calibration by using TVC

International Nuclear Information System (INIS)

Ali, Rasha S M

2015-01-01

Accurate calibration of ac voltages up to 1000 V by using thermal converters requires range resistors connected in series with the converter. The combination of a thermal converter and range resistor is known as the thermal voltage converter. In this paper, multi-range internal range resistors are designed and implemented in the National Institute for Standards (NIS), Egypt to cover the ac voltage ranges from 10 V to 750 V. The range resistor values are 2 kΩ, 10 kΩ, 20 kΩ, 40 kΩ, 100 kΩ, and 150 kΩ to cover the voltage ranges 10 V, 50 V, 100 V, 200 V, 500 V, and 750 V, respectively. The six range resistors are mounted in series with a single-junction thermo-element in the same box to provide a new thermal voltage converter. The required range resistor is selected by using a six-pin selector switch. Each resistor is connected to a selector pin. The new thermal voltage converter ranges are automatically calibrated against other standard thermal voltage converters at different frequencies by using a LabVIEW program to determine their ac–dc transfer difference at each range. The expanded uncertainties are estimated according to the GUM for all ranges at different frequencies. The performance of the new thermal voltage converter is also evaluated by comparing its ac–dc differences and its accuracy in measuring the ac voltage at different frequencies with a traditional thermal voltage converter. (paper)

An isolated bridgeless AC-DC PFC converter using a LC resonant voltage doubler rectifier

Science.gov (United States)

Lee, Sin-woo; Do, Hyun-Lark

2016-12-01

This paper proposed an isolated bridgeless AC-DC power factor correction (PFC) converter using a LC resonant voltage doubler rectifier. The proposed converter is based on isolated conventional single-ended primary inductance converter (SEPIC) PFC converter. The conduction loss of rectification is reduced than a conventional one because the proposed converter is designed to eliminate a full-bridge rectifier at an input stage. Moreover, for zero-current switching (ZCS) operation and low voltage stresses of output diodes, the secondary of the proposed converter is designed as voltage doubler with a LC resonant tank. Additionally, an input-output electrical isolation is provided for safety standard. In conclusion, high power factor is achieved and efficiency is improved. The operational principles, steady-state analysis and design equations of the proposed converter are described in detail. Experimental results from a 60 W prototype at a constant switching frequency 100 kHz are presented to verify the performance of the proposed converter.

A decomposition method for network-constrained unit commitment with AC power flow constraints

International Nuclear Information System (INIS)

Bai, Yang; Zhong, Haiwang; Xia, Qing; Kang, Chongqing; Xie, Le

2015-01-01

To meet the increasingly high requirement of smart grid operations, considering AC power flow constraints in the NCUC (network-constrained unit commitment) is of great significance in terms of both security and economy. This paper proposes a decomposition method to solve NCUC with AC power flow constraints. With conic approximations of the AC power flow equations, the master problem is formulated as a MISOCP (mixed integer second-order cone programming) model. The key advantage of this model is that the active power and reactive power are co-optimised, and the transmission losses are considered. With the AC optimal power flow model, the AC feasibility of the UC result of the master problem is checked in subproblems. If infeasibility is detected, feedback constraints are generated based on the sensitivity of bus voltages to a change in the unit reactive power generation. They are then introduced into the master problem in the next iteration until all AC violations are eliminated. A 6-bus system, a modified IEEE 30-bus system and the IEEE 118-bus system are used to validate the performance of the proposed method, which provides a satisfactory solution with approximately 44-fold greater computational efficiency. - Highlights: • A decomposition method is proposed to solve the NCUC with AC power flow constraints • The master problem considers active power, reactive power and transmission losses. • OPF-based subproblems check the AC feasibility using parallel computing techniques. • An effective feedback constraint interacts between the master problem and subproblem. • Computational efficiency is significantly improved with satisfactory accuracy

Distributed Primary and Secondary Power Sharing in a Droop-Controlled LVDC Microgrid with Merged AC and DC Characteristics

DEFF Research Database (Denmark)

Peyghami, Saeed; Mokhtari, Hossein; Loh, Poh Chiang

2018-01-01

In an ac microgrid, a common frequency exists for coordinating active power sharing among droop-controlled sources. A common frequency is absent in a dc microgrid, leaving only the dc source voltages for coordinating active power sharing. That causes sharing error and poorer voltage regulation in...

An estimator-based distributed voltage-predictive control strategy for ac islanded microgrids

DEFF Research Database (Denmark)

Wang, Yanbo; Chen, Zhe; Wang, Xiongfei

2015-01-01

This paper presents an estimator-based voltage predictive control strategy for AC islanded microgrids, which is able to perform voltage control without any communication facilities. The proposed control strategy is composed of a network voltage estimator and a voltage predictive controller for each...... and has a good capability to reject uncertain perturbations of islanded microgrids....

Marine High Voltage Power Conditioning and Transmission System with Integrated Storage DE-EE0003640 Final Report

Energy Technology Data Exchange (ETDEWEB)

Frank Hoffmann, PhD; Aspinall, Rik

2012-12-10

Design, Development, and test of the three-port power converter for marine hydrokinetic power transmission. Converter provides ports for AC/DC conversion of hydrokinetic power, battery storage, and a low voltage to high voltage DC port for HVDC transmission to shore. The report covers the design, development, implementation, and testing of a prototype built by PPS.

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

A Multi-Functional Fully Distributed Control Framework for AC Microgrids

DEFF Research Database (Denmark)

Shafiee, Qobad; Nasirian, Vahidreza; Quintero, Juan Carlos Vasquez

2018-01-01

This paper proposes a fully distributed control methodology for secondary control of AC microgrids. The control framework includes three modules: voltage regulator, reactive power regulator, and active power/frequency regulator. The voltage regulator module maintains the average voltage of the mi......This paper proposes a fully distributed control methodology for secondary control of AC microgrids. The control framework includes three modules: voltage regulator, reactive power regulator, and active power/frequency regulator. The voltage regulator module maintains the average voltage...... of the microgrid distribution line at the rated value. The reactive power regulator compares the local normalized reactive power of an inverter with its neighbors’ powers on a communication graph and, accordingly, fine-tunes Q-V droop coefficients to mitigate any reactive power mismatch. Collectively, these two....../reactive power sharing. An AC microgrid is prototyped to experimentally validate the proposed control methodology against the load change, plug-and-play operation, and communication constraints such as delay, packet loss, and limited bandwidth....

Design of a Solid-State Fast Voltage Compensator for klystron modulators requiring constant AC power consumption

CERN Document Server

Aguglia, Davide; Viarouge, Philippe; Cros, Jerome

2014-01-01

This paper proposes a novel topological solution for klystron modulators integrating a Fast Voltage Compensator which allows an operation at constant power consumption from the utility grid. This kind of solution is mandatory for the CLIC project under study, which requires several hundreds of synchronously operated klystron modulators for a total pulsed power of 39 GW. The topology is optimized for the challenging CLIC specifications, which require a very precise output voltage flat-top as well as fast rise and fall times (3µs). The Fast Voltage Compensator is integrated in the modulator such that it only has to manage the capacitor charger current and a fraction of the charging voltage. Consequently, its dimensioning power and cost is minimized.

Modeling generalized interline power-flow controller (GIPFC using 48-pulse voltage source converters

Directory of Open Access Journals (Sweden)

Amir Ghorbani

2018-05-01

Full Text Available Generalized interline power-flow controller (GIPFC is one of the voltage-source controller (VSC-based flexible AC transmission system (FACTS controllers that can independently regulate the power-flow over each transmission line of a multiline system. This paper presents the modeling and performance analysis of GIPFC based on 48-pulsed voltage-source converters. This paper deals with a cascaded multilevel converter model, which is a 48-pulse (three levels voltage source converter. The voltage source converter described in this paper is a harmonic neutralized, 48-pulse GTO converter. The GIPFC controller is based on d-q orthogonal coordinates. The algorithm is verified using simulations in MATLAB/Simulink environment. Comparisons between unified power flow controller (UPFC and GIPFC are also included. Keywords: Generalized interline power-flow controller (GIPFC, Voltage source converter (VCS, 48-pulse GTO converter

Power Quality Assessment in Real Shipboard Microgrid Systems under Unbalanced and Harmonic AC Bus Voltage

DEFF Research Database (Denmark)

Liu, Wenzhao; Tarasiuk, Tomasz; Gorniak, Mariusz

2018-01-01

were proposed and carried out in a real ship under sea-going conditions to address this problem. The ship experimental results were presented and discussed considering non-linear bow thruster load and high power ballast pump loads under unbalanced and harmonic voltage conditions. In addition......, the analysis of voltage transient dips during ballast pump starting up is presented. Further, the voltage/current distortions of working generator, bow thruster and pump loads are analyzed. The paper provides a valuable analysis for coping with PQ issues in the real ship power system....

Load Flow Analysis of Hybrid AC-DC Power System with Offshore Wind Power

DEFF Research Database (Denmark)

Dhua, Debasish; Huang, Shaojun; Wu, Qiuwei

2017-01-01

The offshore wind power has received immense attention because of higher wind speed and lower opposition for construction. A wide range of combinations of high-voltage ACDC transmission have been proposed for integrating offshore wind farms and long-distance power transmission. This paper...... is to model such hybrid AC-DC systems including the interfacing converters, which have several control parameters that can change the load flow of the hybrid systems. Then, the paper proposes a Load Flow algorithm based on the Newton-Raphson method, which covers three different section types...

AC losses for the various voltage-leads in a semi-triple layer BSCCO conductor

International Nuclear Information System (INIS)

Li, Z.; Ryu, K.; Hwang, S.D.; Cha, G.; Song, H.J.

2011-01-01

Two voltage-leads (inner-lead, outer-lead) were soldered to the wires in each layer. Voltage-lead (total-lead) was soldered to the inner layer and arranged on the surface of the outer layer. The loss from the total-lead significantly differs from the sum of the wire losses. In order to investigate the AC loss of the multilayer conductor in a high temperature superconductor cable, a voltage-lead was generally attached to the outermost layer of the conductor. But the conductor's AC loss has not been completely cleared due to the various contact positions and arrangements of the voltage-lead. In this paper, we prepared a semi-triple layer conductor consisting of an inner layer and an outer layer with double layer structure. To measure the AC loss of the conductor, two voltage-leads (inner-lead, outer-lead) were soldered to the wires in each layer and arranged along their surfaces, as well as another voltage-lead (total-lead) was soldered to the inner layer and arranged on the surface of the outer layer. The results show that the AC losses for each layer measured from the inner-lead and the outer-lead, respectively, are identical to the sum of the wire losses. The AC losses in the semi-triple layer conductor measured from the total-lead and the outer-lead are identical for the uniform layer current density, and similar to the sum of the wire losses in both layers. However, the losses measured for the non-uniform layer current density from three voltage-leads are unequal to each other, and the loss from the total-lead significantly differs from the sum of the wire losses.

A single-phase PWM controlled AC to DC converter based on control of unity displacement power factor

OpenAIRE

Funabiki, Shigeyuki

1990-01-01

A modified pulse-width modulation (PWM) technique that improves the displacement power factor and the input power factor of a single-phase AC to DC converter is discussed. The modified converter is shown to have a high input power factor and allows the of DC voltage from zero to more than the maximum value of the source voltage. The displacement power factor is unity, and the input power factor is almost unity in the wide range of current command

Control of VSC-HVDC in offshore AC islands with wind power plants: Comparison of two alternatives

DEFF Research Database (Denmark)

Zeni, Lorenzo; Hesselbæk, Bo; Sørensen, Poul Ejnar

2015-01-01

The subject of this paper is the control of offshore AC collection and export networks behind a voltage source converter based high voltage direct current transmission system. The inertia-less nature of such grids makes the control of voltages and power flows potentially more flexible......, but at the same time more prone to instabilities. Focus in this paper is on a voltage source converter based high voltage direct current connected wind power plant. Two state-of-art controllers for the offshore high voltage direct current converter station are compared, both at no-load and when wind turbine...... converters are producing power and controlled with usual vector current control. Sensitivity analyses help identify critical factors influencing stability. The influence of lumping the wind power plant into one converter is assessed by comparison with the full model. The conclusions identify the preferred...

Power sharing algorithm for vector controlled six-phase AC motor with four customary three-phase voltage source inverter drive

Directory of Open Access Journals (Sweden)

Sanjeevikumar Padmanaban

2015-09-01

Full Text Available This paper considered a six-phase (asymmetrical induction motor, kept 30° phase displacement between two set of three-phase open-end stator windings configuration. The drive system consists of four classical three-phase voltage inverters (VSIs and all four dc sources are deliberately kept isolated. Therefore, zero-sequence/homopolar current components cannot flow. The original and effective power sharing algorithm is proposed in this paper with three variables (degree of freedom based on synchronous field oriented control (FOC. A standard three-level space vector pulse width modulation (SVPWM by nearest three vectors (NTVs approach is adopted to regulate each couple of VSIs. The proposed power sharing algorithm is verified by complete numerical simulation modeling (Matlab/Simulink-PLECS software of whole ac drive system by observing the dynamic behaviors in different designed condition. Set of results are provided in this paper, which confirms a good agreement with theoretical development.

Discreteness-induced resonances and ac voltage amplitudes in long one-dimensional Josephson junction arrays

International Nuclear Information System (INIS)

Duwel, A.E.; Watanabe, S.; Trias, E.; Orlando, T.P.; van der Zant, H.S.; Strogatz, S.H.

1997-01-01

New resonance steps are found in the experimental current-voltage characteristics of long, discrete, one-dimensional Josephson junction arrays with open boundaries and in an external magnetic field. The junctions are underdamped, connected in parallel, and dc biased. Numerical simulations based on the discrete sine-Gordon model are carried out, and show that the solutions on the steps are periodic trains of fluxons, phase locked by a finite amplitude radiation. Power spectra of the voltages consist of a small number of harmonic peaks, which may be exploited for possible oscillator applications. The steps form a family that can be numbered by the harmonic content of the radiation, the first member corresponding to the Eck step. Discreteness of the arrays is shown to be essential for appearance of the higher order steps. We use a multimode extension of the harmonic balance analysis, and estimate the resonance frequencies, the ac voltage amplitudes, and the theoretical limit on the output power on the first two steps. copyright 1997 American Institute of Physics

Coordinated Voltage Control in Offshore HVDC Connected Cluster of Wind Power Plants

DEFF Research Database (Denmark)

Sakamuri, Jayachandra N.; Rather, Zakir Hussain; Rimez, Johan

2016-01-01

This paper presents a coordinated voltage control scheme (CVCS) for a cluster of offshore wind power plants (OWPPs) connected to a VSC HVDC system. The primary control point of the proposed voltage control scheme is the introduced Pilot bus, which is having the highest short circuit capacity...... in the offshore AC grid. The developed CVCS comprehends an optimization algorithm, aiming for minimum active power losses in the offshore grid, to generate voltage reference to the Pilot bus. During steady state operation, the Pilot bus voltage is controlled by dispatching reactive power references to each wind...... turbine (WT) in the WPP cluster based on their available reactive power margin and network sensitivity based participation factors, which are derived from the dV/dQ sensitivity of a WT bus w.r.t the Pilot bus. This method leads to minimization of the risk of undesired effects, particularly overvoltage...

Model Predictive Control of Power Converters for Robust and Fast Operation of AC Microgrids

DEFF Research Database (Denmark)

Dragicevic, Tomislav

2018-01-01

the load power at the same time. Those functionalities are conventionally achieved by hierarchical linear control loops. However, they have limited transient response and high sensitivity to parameter variations. This paper aims to mitigate these problems by firstly introducing an improvement of the FCS......This paper proposes the application of a finite control set model predictive control (FCS-MPC) strategy in standalone ac microgrids (MGs). AC MGs are usually built from two or more voltage source converters (VSCs) which can regulate the voltage at the point of common coupling, while sharing......-MPC strategy for a single VSC based on tracking of derivative of the voltage reference trajectory. Using only a single step prediction horizon, the proposed strategy exhibits low computational expense but provides steady state performance comparable to PWM, while its transient response and robustness...

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

DC-bus voltage control of grid-connected voltage source converter by using space vector modulated direct power control under unbalanced network conditions

DEFF Research Database (Denmark)

Xiao, Lei; Huang, Shoudao; Lu, Kaiyuan

2013-01-01

Unbalanced grid voltage will cause large dc-bus voltage ripple and introduce high harmonic current components on the grid side. This will severely threaten the safety of the grid-connected voltage source converter (VSC) and consequently, affect the healthy operation condition of the load. In this......Unbalanced grid voltage will cause large dc-bus voltage ripple and introduce high harmonic current components on the grid side. This will severely threaten the safety of the grid-connected voltage source converter (VSC) and consequently, affect the healthy operation condition of the load....... In this study, a new proportional-integral-resonant (PI-RES) controller-based, space vector modulated direct power control topology is proposed to suppress the dc-bus voltage ripple and in the same time, controlling effectively the instantaneous power of the VSC. A special ac reactive power reference component...... is introduced in the controller, which is necessary in order to reduce the dc-bus voltage ripple and active power harmonics at the same time. The proposed control topology is implemented in the lab. Simulation and experimental results are provided to validate its performance and the analysis presented...

Adaptive Sliding Mode Control of MEMS AC Voltage Reference Source

Directory of Open Access Journals (Sweden)

Ehsan Ranjbar

2017-01-01

Full Text Available The accuracy of physical parameters of a tunable MEMS capacitor, as the major part of MEMS AC voltage reference, is of great importance to achieve an accurate output voltage free of the malfunctioning noise and disturbance. Even though strenuous endeavors are made to fabricate MEMS tunable capacitors with desiderated accurate physical characteristics and ameliorate exactness of physical parameters’ values, parametric uncertainties ineluctably emerge in fabrication process attributable to imperfections in micromachining process. First off, this paper considers applying an adaptive sliding mode controller design in the MEMS AC voltage reference source so that it is capable of giving off a well-regulated output voltage in defiance of jumbling parametric uncertainties in the plant dynamics and also aggravating external disturbance imposed on the system. Secondly, it puts an investigatory comparison with the designed model reference adaptive controller and the pole-placement state feedback one into one’s prospective. Not only does the tuned adaptive sliding mode controller show remarkable robustness against slow parameter variation and external disturbance being compared to the pole-placement state feedback one, but also it immensely gets robust against the external disturbance in comparison with the conventional adaptive controller. The simulation results are promising.

Method and system for a gas tube switch-based voltage source high voltage direct current transmission system

Science.gov (United States)

She, Xu; Chokhawala, Rahul Shantilal; Zhou, Rui; Zhang, Di; Sommerer, Timothy John; Bray, James William

2016-12-13

A voltage source converter based high-voltage direct-current (HVDC) transmission system includes a voltage source converter (VSC)-based power converter channel. The VSC-based power converter channel includes an AC-DC converter and a DC-AC inverter electrically coupled to the AC-DC converter. The AC-DC converter and a DC-AC inverter include at least one gas tube switching device coupled in electrical anti-parallel with a respective gas tube diode. The VSC-based power converter channel includes a commutating circuit communicatively coupled to one or more of the at least one gas tube switching devices. The commutating circuit is configured to "switch on" a respective one of the one or more gas tube switching devices during a first portion of an operational cycle and "switch off" the respective one of the one or more gas tube switching devices during a second portion of the operational cycle.

A novel power control strategy of Modular Multi-level Converter in HVDC-AC hybrid transmission systems for passive networks

DEFF Research Database (Denmark)

Hu, Zhenda; Wu, Rui; Yang, Xiaodong

2014-01-01

With the development of High Voltage DC Transmission (HVDC) technology, there will be more and more HVDC-AC hybrid transmission system in the world. A basic challenge in HVDC-AC hybrid transmission systems is to optimize the power sharing between DC and AC lines, which become more severe when sup...... control strategy of Modular Multi-level Converter in VSC-HVDC, which can optimize converter output power according to passive network loading variation. Proposal method is studied with a case study of a VSC-HVDC AC hybrid project by PSCAD/EMTDC simulations....

Integral Plus Resonant Sliding Mode Direct Power Control for VSC-HVDC Systems under Unbalanced Grid Voltage Conditions

Directory of Open Access Journals (Sweden)

Weipeng Yang

2017-10-01

Full Text Available An integral plus resonant sliding mode direct power control (IRSMC DPC strategy for voltage source converter high voltage direct current (VSC-HVDC systems under unbalanced grid voltage conditions is proposed in this paper. Through detailed instantaneous power flow analysis, a generalized power compensation method, by which the ratio between the amplitude of active and reactive power ripples can be controlled continuously, is obtained. This enables the system to provide flexible power control, so that the desired performance of the system on both the ac and dc sides can be attained under different operating conditions. When the grid voltage is unbalanced, one or both of the active and reactive power terms contain ripples, oscillating at twice the grid frequency, to obtain non-distorted ac current. A power controller consisting of the proportional, integral and resonant control laws is designed using the sliding mode control approach, to achieve accurate power control objective. Simulation studies on a two-terminal VSC-HVDC system using MATLAB/SIMULINK (R2013b, Mathworks, Natick, MA, USA are conducted to verify the effectiveness of the IRSMC DPC strategy. The results show that this strategy ensures satisfactory performance of the system over a wide range of operating conditions.

Ion peak narrowing by applying additional AC voltage (ripple voltage) to FAIMS extractor electrode.

Science.gov (United States)

Pervukhin, Viktor V; Sheven, Dmitriy G

2010-01-01

The use of a non-uniform electric field in a high-field asymmetric waveform ion mobility spectrometry (FAIMS) analyzer increases sensitivity but decreases resolution. The application of an additional AC voltage to the extractor electrode ("ripple" voltage, U(ripple)) can overcome this effect, which decreases the FAIMS peak width. In this approach, the diffusion ion loss remains minimal in the non-uniform electric field in the cylindrical part of the device, and all ion losses under U(ripple) occur in a short portion of their path. Application of the ripple voltage to the extractor electrode is twice as efficient as the applying of U(ripple) along the total length of the device. 2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.

A Coordinated Control for Photovoltaic Generators and Energy Storages in Low-Voltage AC/DC Hybrid Microgrids under Islanded Mode

Directory of Open Access Journals (Sweden)

Yao Liu

2016-08-01

Full Text Available The increasing penetration of renewable generators can be a significant challenge due to the fluctuation of their power generation. Energy storage (ES units are one solution to improve power supply quality and guarantee system stability. In this paper, a hybrid microgrid is built based on photovoltaic (PV generator and ES; and coordinated control is proposed and developed to achieve power management in a decentralized manner. This control scheme contains three different droop strategies according to characteristics of PV and ES. First, the modified droop control is proposed for PV, which can take full utilization of renewable energy and avoid regulating output active power frequently. Second, to maintain the direct current (DC bus voltage stability, a novel droop control incorporating a constant power band is presented for DC-side ES. Third, a cascade droop control is designed for alternating current (AC-side ES. Thus, the ES lifetime is prolonged. Moreover, interlinking converters (ICs provide a bridge between AC/DC buses in a hybrid microgrid. The power control of IC is enabled when the AC- or DC-side suffer from active power demand shortage. In particular, if the AC microgrid does not satisfy the reactive power demand, IC then acts as a static synchronous compensator (STATCOM. The effectiveness of the proposed strategies is verified by simulations.

Simultaneous distribution of AC and DC power

Science.gov (United States)

Polese, Luigi Gentile

2015-09-15

A system and method for the transport and distribution of both AC (alternating current) power and DC (direct current) power over wiring infrastructure normally used for distributing AC power only, for example, residential and/or commercial buildings' electrical wires is disclosed and taught. The system and method permits the combining of AC and DC power sources and the simultaneous distribution of the resulting power over the same wiring. At the utilization site a complementary device permits the separation of the DC power from the AC power and their reconstruction, for use in conventional AC-only and DC-only devices.

21 CFR 886.4440 - AC-powered magnet.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false AC-powered magnet. 886.4440 Section 886.4440 Food... DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4440 AC-powered magnet. (a) Identification. An AC-powered magnet is an AC-powered device that generates a magnetic field intended to find and remove...

Engineering Design of the ITER AC/DC Power Supplies

International Nuclear Information System (INIS)

Oh, B. H.; Lee, K. W.; Hwang, C. K.; Jin, J. T.; Chang, D. S.; Kim, T. S.

2009-02-01

To design high power pulse power supplies, especially in huge power supplies have not designed till now, it is necessary to analyze a system's characteristics and relations with another systems as well as to know high voltage, high current control technologies. Contents of this project are; - Study for the engineering designs changed recently by ITER Organization(IO) and writing specifications for the power supplies to reduce project risk. - Detailed analysis of the AC/DC Converters and writing subtask reports on the Task Agreement. - Study for thyristor numbers, DCR's specifications for Korea-China sharing meetings. - Study for the grounding systems of the ITER power supply system. The results may used as one of reference for practical designs of the high power coil power supplies and also may used in various field such as electroplating, plasma arc furnaces, electric furnaces

Enhanced DC-Link Capacitor Voltage Balancing Control of DC–AC Multilevel Multileg Converters

DEFF Research Database (Denmark)

Busquets-Monge, Sergio; Maheshwari, Ram Krishan; Nicolas-Apruzzese, Joan

2015-01-01

This paper presents a capacitor voltage balancing control applicable to any multilevel dc–ac converter formed by a single set of series-connected capacitors implementing the dc link and semiconductor devices, such as the diode-clamped topology. The control is defined for any number of dc-link vol......This paper presents a capacitor voltage balancing control applicable to any multilevel dc–ac converter formed by a single set of series-connected capacitors implementing the dc link and semiconductor devices, such as the diode-clamped topology. The control is defined for any number of dc...

Ac-dc converter firing error detection

International Nuclear Information System (INIS)

Gould, O.L.

1996-01-01

Each of the twelve Booster Main Magnet Power Supply modules consist of two three-phase, full-wave rectifier bridges in series to provide a 560 VDC maximum output. The harmonic contents of the twelve-pulse ac-dc converter output are multiples of the 60 Hz ac power input, with a predominant 720 Hz signal greater than 14 dB in magnitude above the closest harmonic components at maximum output. The 720 Hz harmonic is typically greater than 20 dB below the 500 VDC output signal under normal operation. Extracting specific harmonics from the rectifier output signal of a 6, 12, or 24 pulse ac-dc converter allows the detection of SCR firing angle errors or complete misfires. A bandpass filter provides the input signal to a frequency-to-voltage converter. Comparing the output of the frequency-to-voltage converter to a reference voltage level provides an indication of the magnitude of the harmonics in the ac-dc converter output signal

Improved Power Control Using Optimal Adjustable Coefficients for Three-Phase Photovoltaic Inverter under Unbalanced Grid Voltage

Science.gov (United States)

Wang, Qianggang; Zhou, Niancheng; Lou, Xiaoxuan; Chen, Xu

2014-01-01

Unbalanced grid faults will lead to several drawbacks in the output power quality of photovoltaic generation (PV) converters, such as power fluctuation, current amplitude swell, and a large quantity of harmonics. The aim of this paper is to propose a flexible AC current generation method by selecting coefficients to overcome these problems in an optimal way. Three coefficients are brought in to tune the output current reference within the required limits of the power quality (the current harmonic distortion, the AC current peak, the power fluctuation, and the DC voltage fluctuation). Through the optimization algorithm, the coefficients can be determined aiming to generate the minimum integrated amplitudes of the active and reactive power references with the constraints of the inverter current and DC voltage fluctuation. Dead-beat controller is utilized to track the optimal current reference in a short period. The method has been verified in PSCAD/EMTDC software. PMID:25243215

Improved power control using optimal adjustable coefficients for three-phase photovoltaic inverter under unbalanced grid voltage.

Science.gov (United States)

Wang, Qianggang; Zhou, Niancheng; Lou, Xiaoxuan; Chen, Xu

2014-01-01

Unbalanced grid faults will lead to several drawbacks in the output power quality of photovoltaic generation (PV) converters, such as power fluctuation, current amplitude swell, and a large quantity of harmonics. The aim of this paper is to propose a flexible AC current generation method by selecting coefficients to overcome these problems in an optimal way. Three coefficients are brought in to tune the output current reference within the required limits of the power quality (the current harmonic distortion, the AC current peak, the power fluctuation, and the DC voltage fluctuation). Through the optimization algorithm, the coefficients can be determined aiming to generate the minimum integrated amplitudes of the active and reactive power references with the constraints of the inverter current and DC voltage fluctuation. Dead-beat controller is utilized to track the optimal current reference in a short period. The method has been verified in PSCAD/EMTDC software.

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.

Development of anode high voltage power supply system for ECRH of HL-2A tokamak

International Nuclear Information System (INIS)

Chen Wenguang

2009-01-01

The anode high voltage power supply system consist of DC high-voltage power supply (HVPS) and pulse modulator. SCR is used to vary AC input voltage of the step-up transformer by controlling the trigger phase in the HVPS, and regulate the DC output voltage linearly at the potential of low-end via BJT, Dual closed-loop control technology is applied in the controller, and its maximum output is at 30kV and 130mA. Tetrode is the core component of the modulator. The circuit design is optimized by using the simulation software. Test and HL-2A discharge experimental results show that the power supply system is designed with some characteristics of output scale widely, low ripple and modulate quickly. (authors)

Three-Phase AC Optimal Power Flow Based Distribution Locational Marginal Price: Preprint

Energy Technology Data Exchange (ETDEWEB)

Yang, Rui; Zhang, Yingchen

2017-05-17

Designing market mechanisms for electricity distribution systems has been a hot topic due to the increased presence of smart loads and distributed energy resources (DERs) in distribution systems. The distribution locational marginal pricing (DLMP) methodology is one of the real-time pricing methods to enable such market mechanisms and provide economic incentives to active market participants. Determining the DLMP is challenging due to high power losses, the voltage volatility, and the phase imbalance in distribution systems. Existing DC Optimal Power Flow (OPF) approaches are unable to model power losses and the reactive power, while single-phase AC OPF methods cannot capture the phase imbalance. To address these challenges, in this paper, a three-phase AC OPF based approach is developed to define and calculate DLMP accurately. The DLMP is modeled as the marginal cost to serve an incremental unit of demand at a specific phase at a certain bus, and is calculated using the Lagrange multipliers in the three-phase AC OPF formulation. Extensive case studies have been conducted to understand the impact of system losses and the phase imbalance on DLMPs as well as the potential benefits of flexible resources.

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.

DC-link Voltage Control to Compensate Voltage Deviation for PV–BESSs Integrated System in Low-Voltage (LV Networks

Directory of Open Access Journals (Sweden)

Lee Gyu-sub

2016-01-01

Full Text Available The exhaustion of fossil fuel and the greenhouse gas emission are one of the most significant energy and environmental issues, respectively. Photovoltaic (PV generators and battery energy storage systems (BESSs have been significantly increased for recent years. The BESSs are mainly used for smoothing active power fluctuation of the PV. In this paper, PV–BESSs integration of two DC/DC converters and one AC/DC converter is investigated and DC-link voltage control to compensate the AC voltage deviation is proposed for the PV‒BESS system in low-voltage (LV networks.

Planning aspects of ac extra high voltage lines

Energy Technology Data Exchange (ETDEWEB)

Engelhardt, H

1964-01-01

The technical points arising in any project for application of higher voltages on power grids in Europe are discussed. The cost aspects of two alternative ways of extending the voltage level of existing systems are discussed in detail. The short-circuit current in a high-power system with isolated or grounded neutral point and its relation to the mode of grounding is examined. For a transmission distance of 200 kVm, operating cost for each kWh transmitted are shown on curves for voltages of 220, 380 and 700 kV against transmitted energy. This shows that for any rated voltage there is a range of energy values which can be transmitted economically. Factors to be considered in maintaining, selecting or rejecting transformers and switchgear of other systems for higher voltage purposes are mentioned.

Investigation on discharge characteristics of a coaxial dielectric barrier discharge reactor driven by AC and ns power sources

Science.gov (United States)

Qian, WANG; Feng, LIU; Chuanrun, MIAO; Bing, YAN; Zhi, FANG

2018-03-01

A coaxial dielectric barrier discharge (DBD) reactor with double layer dielectric barriers has been developed for exhaust gas treatment and excited either by AC power or nanosecond (ns) pulse to generate atmospheric pressure plasma. The comparative study on the discharge characteristics of the discharge uniformity, power deposition, energy efficiency, and operation temperature between AC and ns pulsed coaxial DBD is carried out in terms of optical and electrical characteristics and operation temperature for optimizing the coaxial DBD reactor performance. The voltages across the air gap and dielectric layer and the conduction and displacement currents are extracted from the applied voltages and measured currents of AC and ns pulsed coaxial DBDs for the calculation of the power depositions and energy efficiencies through an equivalent electrical model. The discharge uniformity and operating temperature of the coaxial DBD reactor are monitored and analyzed by optical images and infrared camera. A heat conduction model is used to calculate the temperature of the internal quartz tube. It is found that the ns pulsed coaxial DBD has a much higher instantaneous power deposition in plasma, a lower total power consumption, and a higher energy efficiency compared with that excited by AC power and is more homogeneous and stable. The temperature of the outside wall of the AC and ns pulse excited coaxial DBD reaches 158 °C and 64.3 °C after 900 s operation, respectively. The experimental results on the comparison of the discharge characteristics of coaxial DBDs excited by different powers are significant for understanding of the mechanism of DBDs, reducing energy loss, and optimizing the performance of coaxial DBD in industrial applications.

Low voltage powering of on-detector electronics for HL-LHC experiments upgrades

CERN Document Server

Bobillier, Vincent; Vasey, Francois; Karmakar, Sabyasachi; Maity, Manas; Roy, Subhasish; Kundu, Tapas Kumar

2018-01-01

All LHC experiments will be upgraded during the next LHC long shutdowns (LS2 and LS3). The increase in resolution and luminosity and the use of more advanced CMOS technology nodes typically implies higher current consumption of the on-detector electronics. In this context, and in view of limiting the cable voltage drop, point-of-load DC-DC converters will be used on detector. This will have a direct impact on the existing powering scheme, implying new AC-DC and/or DC-DC stages as well as changes in the power cabling infrastructure. This paper presents the first results obtained while evaluating different LV powering schemes and distribution layouts for HL-LHC trackers. The precise low voltage power source requirements are being assessed and understood using the CMS tracker upgrade as a use-case.

Distributed AC power flow method for AC and AC-DC hybrid ...

African Journals Online (AJOL)

... on voltage level and R/X ratio in the formulation itself. DPFM is applied on a 10 bus, low voltage, microgrid system giving a better voltage profile.. Keywords: Microgrid (MG), Distributed Energy Resources (DER), Particle Swarm Optimization (OPF), Time varying inertia weight (TVIW), Distributed power flow method (DPFM) ...

Design and power management of an offshore medium voltage DC microgrid realized through high voltage power electronics technologies and control

Science.gov (United States)

Grainger, Brandon Michael

The growth in the electric power industry's portfolio of Direct Current (DC) based generation and loads have captured the attention of many leading research institutions. Opportunities for using DC based systems have been explored in electric ship design and have been a proven, reliable solution for transmitting bulk power onshore and offshore. To integrate many of the renewable resources into our existing AC grid, a number of power conversions through power electronics are required to condition the equipment for direct connection. Within the power conversion stages, there is always a requirement to convert to or from DC. The AC microgrid is a conceptual solution proposed for integrating various types of renewable generation resources. The fundamental microgrid requirements include the capability of operating in islanding mode and/or grid connected modes. The technical challenges associated with microgrids include (1) operation modes and transitions that comply with IEEE1547 without extensive custom engineering and (2) control architecture and communication. The Medium Voltage DC (MVDC) architecture, explored by the University of Pittsburgh, can be visualized as a special type of DC microgrid. This dissertation is multi-faceted, focused on many design aspects of an offshore DC microgrid. The focal points of the discussion are focused on optimized high power, high frequency magnetic material performance in electric machines, transformers, and DC/DC power converters---all components found within offshore, power system architectures. A new controller design based upon model reference control is proposed and shown to stabilize the electric motor drives (modeled as constant power loads), which serve as the largest power consuming entities in the microgrid. The design and simulation of a state-of-the-art multilevel converter for High Voltage DC (HVDC) is discussed and a component sensitivity analysis on fault current peaks is explored. A power management routine is

Investigating Enhancement Mode Gallium Nitride Power FETs in High Voltage, High Frequency Soft Switching Converters

DEFF Research Database (Denmark)

Nour, Yasser; Knott, Arnold; Jørgensen, Ivan Harald Holger

2016-01-01

An increased attention has been detected to develop smaller and lighter high voltage power converters in the range of 50V to 400V domain. The main applications for these converters are mainly focused for Power over Ethernet (PoE), LED lighting and AC adapters. This work will discuss a study...

Interior point algorithm-based power flow optimisation of a combined AC and DC multi-terminal grid

Directory of Open Access Journals (Sweden)

Farhan Beg

2015-01-01

Full Text Available The high cost of power electronic equipment, lower reliability and poor power handling capacity of the semiconductor devices had stalled the deployment of systems based on DC (multi-terminal direct current system (MTDC networks. The introduction of voltage source converters (VSCs for transmission has renewed the interest in the development of large interconnected grids based on both alternate current (AC and DC transmission networks. Such a grid platform also realises the added advantage of integrating the renewable energy sources into the grid. Thus a grid based on DC MTDC network is a possible solution to improve energy security and check the increasing supply demand gap. An optimal power solution for combined AC and DC grids obtained by the solution of the interior point algorithm is proposed in this study. Multi-terminal HVDC grids lie at the heart of various suggested transmission capacity increases. A significant difference is observed when MTDC grids are solved for power flows in place of conventional AC grids. This study deals with the power flow problem of a combined MTDC and an AC grid. The AC side is modelled with the full power flow equations and the VSCs are modelled using a connecting line, two generators and an AC node. The VSC and the DC losses are also considered. The optimisation focuses on several different goals. Three different scenarios are presented in an arbitrary grid network with ten AC nodes and five converter stations.

Index-based reactive power compensation scheme for voltage regulation

Science.gov (United States)

Dike, Damian Obioma

2008-10-01

Increasing demand for electrical power arising from deregulation and the restrictions posed to the construction of new transmission lines by environment, socioeconomic, and political issues had led to higher grid loading. Consequently, voltage instability has become a major concern, and reactive power support is vital to enhance transmission grid performance. Improved reactive power support to distressed grid is possible through the application of relatively unfamiliar emerging technologies of "Flexible AC Transmission Systems (FACTS)" devices and "Distributed Energy Resources (DERS)." In addition to these infrastructure issues, a lack of situational awareness by system operators can cause major power outages as evidenced by the August 14, 2003 widespread North American blackout. This and many other recent major outages have highlighted the inadequacies of existing power system indexes. In this work, a novel "Index-based reactive compensation scheme" appropriate for both on-line and off-line computation of grid status has been developed. A new voltage stability index (Ls-index) suitable for long transmission lines was developed, simulated, and compared to the existing two-machine modeled L-index. This showed the effect of long distance power wheeling amongst regional transmission organizations. The dissertation further provided models for index modulated voltage source converters (VSC) and index-based load flow analysis of both FACTS and microgrid interconnected power systems using the Newton-Raphson's load flow model incorporated with multi-FACTS devices. The developed package has been made user-friendly through the embodiment of interactive graphical user interface and implemented on the IEEE 14, 30, and 300 bus systems. The results showed reactive compensation has system wide-effect, provided readily accessible system status indicators, ensured seamless DERs interconnection through new islanding modes and enhanced VSC utilization. These outcomes may contribute

Low voltage ride-through capability control for single-stage inverter-based grid-connected photovoltaic power plant

DEFF Research Database (Denmark)

Al-Shetwi, Ali Q.; Sujod, Muhamad Zahim; Blaabjerg, Frede

2018-01-01

and current limiter are used to absorb the excessive dc-voltage and limits excessive ac current, respectively. This control strategy can also ensure the reactive power support through the injection of reactive current according to the standard requirements as soon as the voltage sag is detected. Furthermore...... to improve the capability of ride-through fault safely and keep the inverter connected, but also to provide grid support through active and reactive power control at different type of faults....

Droop-free Distributed Control for AC Microgrids

DEFF Research Database (Denmark)

Nasirian, Vahidreza; Shafiee, Qobad; Guerrero, Josep M.

2016-01-01

A cooperative distributed secondary/primary control paradigm for AC microgrids is proposed. This solution replaces the centralized secondary control and the primary-level droop mechanism of each inverter with three separate regulators: voltage, reactive power, and active power regulators. A sparse...... guidelines are provided. Steady-state performance analysis shows that the proposed controller can accurately handle the global voltage regulation and proportional load sharing. An AC microgrid prototype is set up, where the controller performance, plug-and-play capability, and resiliency to the failure...

Study of Power Flow Algorithm of AC/DC Distribution System including VSC-MTDC

Directory of Open Access Journals (Sweden)

Haifeng Liang

2015-08-01

Full Text Available In recent years, distributed generation and a large number of sensitive AC and DC loads have been connected to distribution networks, which introduce a series of challenges to distribution network operators (DNOs. In addition, the advantages of DC distribution networks, such as the energy conservation and emission reduction, mean that the voltage source converter based multi-terminal direct current (VSC-MTDC for AC/DC distribution systems demonstrates a great potential, hence drawing growing research interest. In this paper, considering losses of the reactor, the filter and the converter, a mathematical model of VSC-HVDC for the load flow analysis is derived. An AC/DC distribution network architecture has been built, based on which the differences in modified equations of the VSC-MTDC-based network under different control modes are analyzed. In addition, corresponding interface functions under five control modes are provided, and a back/forward iterative algorithm which is applied to power flow calculation of the AC/DC distribution system including VSC-MTDC is proposed. Finally, by calculating the power flow of the modified IEEE14 AC/DC distribution network, the efficiency and validity of the model and algorithm are evaluated. With various distributed generations connected to the network at appropriate locations, power flow results show that network losses and utilization of transmission networks are effectively reduced.

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.

A Communication-Less Distributed Voltage Control Strategy for a Multi-Bus AC Islanded Microgrid

DEFF Research Database (Denmark)

Wang, Yanbo; Tan, Yongdong; Chen, Zhe

2014-01-01

This paper presents a communication-less distributed voltage control strategy for a multi-bus AC islanded microgrid. First, a Kalman Filter-based network voltage estimator is proposed to obtain voltage responses without communication links in the presence of load disturbances. Then, a voltage...... and reliability is improved for islanded microgrids due to communication-less operation. The simulations and experimental results are presented to validate the proposed distributed voltage control strategy....... optimal controller using MPC (Model Predictive Control) are developed to implement voltage optimal control. The contributions of this paper are demonstrated: (1) The proposed voltage estimator can dynamically obtain network voltage responses just through local voltage and current associated with each DG...

A Direct Power Conversion Topology for Grid Integration of Hybrid AC/DC Energy Resources

DEFF Research Database (Denmark)

Liu, Xiong; Loh, Poh Chiang; Wang, Peng

2013-01-01

This paper proposes a multiple-input versatile matrix converter (VMC) for integrating hybrid ac/dc energy resources and storages to the power grid. The VMC is developed from the traditional indirect matrix converter but operates in the reverse-boost mode rather than in the forward-buck mode....... The reverse-boost mode is more relevant here since most renewable sources and energy storages have lower voltages than the grid. The eventual VMC developed uses an alternative nine-switch converter, rather than usual six-switch voltage-source converter, for providing six input terminals in total. One three...

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.)

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...

Wind-powered asynchronous AC/DC/AC converter system. [for electric power supply regulation

Science.gov (United States)

Reitan, D. K.

1973-01-01

Two asynchronous ac/dc/ac systems are modelled that utilize wind power to drive a variable or constant hertz alternator. The first system employs a high power 60-hertz inverter tie to the large backup supply of the power company to either supplement them from wind energy, storage, or from a combination of both at a preset desired current; rectifier and inverter are identical and operate in either mode depending on the silicon control rectifier firing angle. The second system employs the same rectification but from a 60-hertz alternator arrangement; it provides mainly dc output, some sinusoidal 60-hertz from the wind bus and some high harmonic content 60-hertz from an 800-watt inverter.

Adapting AC Lines to DC Grids for Large-Scale Renewable Power Transmission

Directory of Open Access Journals (Sweden)

D. Marene Larruskain

2014-10-01

Full Text Available All over the world, governments of different countries are nowadays promoting the use of clean energies in order to achieve sustainable energy systems. In this scenario, since the installed capacity is continuously increasing, renewable sources can play an important role. Notwithstanding that, some important problems may appear when connecting these sources to the grid, being the overload of distribution lines one of the most relevant. In fact, renewable generation is usually connected to the nearest AC grid, although this HV system may not have been designed considering distributed generation. In the particular case of large wind farms, the electrical grid has to transmit all the power generated by wind energy and, as a consequence, the AC system may get overloaded. It is therefore necessary to determine the impact of wind power transmission so that appropriate measures can be taken. Not only are these measures influenced by the amount of power transmitted, but also by the quality of the transmitted power, due to the output voltage fluctuation caused by the highly variable nature of wind. When designing a power grid, although AC systems are usually the most economical solution because of its highly proven technology, HVDC may arise in some cases (e.g. offshore wind farms as an interesting alternative, offering some added values such as lower losses and better controllability. This way, HVDC technology can solve most of the aforementioned problems and has a good potential for future use. Additionally, the fast development of power electronics based on new and powerful semiconductor devices allow the spread of innovative technologies, such as VSC-HVDC, which can be applied to create DC grids. This paper focuses on the main aspects involved in adapting the existing overhead AC lines to DC grids, with the objective of improving the transmission of distributed renewable energy to the centers of consumption.

A comparative study of different transformer connections for railway power supply- mitigation of voltage unbalance

DEFF Research Database (Denmark)

Firat, Gurkan; Yang, Guangya; Ali Hussain Al-Ali, Haider

2015-01-01

The railway represents a large power consumer that can cause uneven loading of the phases in the high voltage grid. These unbalanced loads supplied by the utility may lead to voltage unbalance problems in the system and thereby affects the other consumers connected to the same network. It is fact...... that, voltage unbalance appears mainly as a result of unbalanced currents at the points of common coupling drawn by unevenly distributed loads. Because of a significant amount of negative sequence current injected to the system, the power system components will suffer from consequent negative effects...... such as overheating, additional losses of lines and transformers, interference with communication systems etc. This paper presents a comparative study of some transformer connections which commonly used in railway supplying AC traction loads, for voltage unbalance mitigations. Simulations for comparison...

21 CFR 880.6320 - AC-powered medical examination light.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false AC-powered medical examination light. 880.6320... Miscellaneous Devices § 880.6320 AC-powered medical examination light. (a) Identification. An AC-powered medical examination light is an AC-powered device intended for medical purposes that is used to illuminate body...

Team-oriented Adaptive Droop Control for Autonomous AC Microgrids

DEFF Research Database (Denmark)

Shafiee, Qobad; Nasirian, Vahidreza; Guerrero, Josep M.

2014-01-01

This paper proposes a distributed control strategy for voltage and reactive power regulation in ac Microgrids. First, the control module introduces a voltage regulator that maintains the average voltage of the system on the rated value, keeping all bus voltages within an acceptable range. Dynamic...

Characterization and assessment of voltage and power constraints of DFIG WT connected to a weak network

DEFF Research Database (Denmark)

Abulanwar, Elsayed; Hu, Weihao; Iov, Florin

2014-01-01

This article thoroughly investigates the challenges and constraints raised by the integration of a Doubly-fed Induction generator wind turbine, DFIG WT, into an ac network of extensively varying parameters and very weak conditions. The objective is to mitigate the voltage variations at the point...... of common coupling, PCC, and maximize the wind power penetration into weak networks. As a basis of investigation, a simplified system model is utilized and the respective PCC voltage, active and reactive power stability issues are identified. Besides, a steady-state study for DFIG WT connected to a weak...

Non-sparking anodization process of AZ91D magnesium alloy under low AC voltage

International Nuclear Information System (INIS)

Li, Weiping; Li, Wen; Zhu, Liqun; Liu, Huicong; Wang, Xiaofang

2013-01-01

Highlights: ► Four different processes appear on magnesium alloys with applied voltage increase. ► Non-sparking film formation process occurred in the range of 6–10 V AC. ► The film was composed of Mg 2 SiO 4 with a stable growth rate in 30 min. ► Film growth was a balance of electrochemical dissolution and chemical deposition. -- Abstract: Anodization is widely recognized as one of the most important surface treatments for magnesium alloys. However, since high voltage oxidation films are limited in some applications due to porosity and brittleness, it is worthwhile to explore the non-sparking oxidizing process. In this work, AZ91D was electrochemically anodized at different AC voltages in an electrolyte containing 120 g/L NaOH and 80 g/L Na 2 SiO 3 ·9H 2 O. The effects of voltage on the surface morphology, composition and reaction process, especially the non-sparking discharge anodic film formation process, were investigated. The results showed that four different processes would appear according to the applied voltage variation from 6 V to 40 V, and that the non-sparking film formation process occurred in the range of 6–10 V. The film formed on the AZ91D surface under 10 V AC was mainly composed of Mg 2 SiO 4 with a lamellar structure. The horizontal and vertical expansion of the lamellar structure resulted in the formation of a multi-layered structure with a stable, linear growth rate for 30 min. The non-sparking film formation process can be considered to be the result of a balance of electrochemical dissolution and chemical deposition reaction

SNS AC Power Distribution and Reliability of AC Power Supply

CERN Document Server

Holik, Paul S

2005-01-01

The SNS Project has 45MW of installed power. A design description under the Construction Design and Maintenance (CDM) with regard to regulations (OSHA, NFPA, NEC), reliability issues and maintenance of the AC power distribution system are herewith presented. The SNS Project has 45MW of installed power. The Accelerator Systems are Front End (FE)and LINAC KLYSTRON Building (LK), Central Helium Liquefier (CHL), High Energy Beam Transport (HEBT), Accumulator Ring and Ring to Target Beam Transport (RTBT) Support Buildings have 30MW installed power. FELK has 16MW installed, majority of which is klystron and magnet power supply system. CHL, supporting the super conducting portion of the accelerator has 7MW installed power and the RING Systems (HEBT, RING and RTBT) have also 7MW installed power.*

PV Power-Generation System with a Phase-Shift PWM Technique for High Step-Up Voltage Applications

Directory of Open Access Journals (Sweden)

Cheng-Tao Tsai

2012-01-01

Full Text Available A PV power-generation system with a phase-shift pulse-width modulation (PWM technique for high step-up voltage applications is proposed. The proposed power-generation system consists of two stages. In the input stage, all power switches of the full-bridge converter with phase-shift technique can be operated with zero-current switching (ZCS at turn-on or turn-off transition. Hence, the switching losses of the power switches can be reduced. Then, in the DC output stage, a voltage-doubler circuit is used to boost a high dc-link bus voltage. To supply a utility power, a dc/ac inverter is connected to induce a sinusoidal source. In order to draw a maximum power from PV arrays source, a microcontroller is incorporated with the perturbation and observation method to implement maximum power point tracking (MPPT algorithm and power regulating scheme. In this study, a full load power of 300 W prototype has been built. Experimental results are presented to verify the performance and feasibility of the proposed PV power-generation system.

Non-isolated DC-AC converter with high voltage gain for autonomous systems of electric power; Conversor CC-CA nao isolado com alto ganho de tensao para aplicacao em sistemas autonomos de energia eletrica

Energy Technology Data Exchange (ETDEWEB)

Silveira, George Cajazeiras [Centro Federal de Educacao Tecnologica do Ceara (CEFET/CE), Fortaleza, CE (Brazil); Torrico-Bascope, Rene P. [Universidade Federal do Ceara (PPGEE/UFC), Fortaleza, CE (Brazil). Programa de Pos Graduacao em Engenharia Eletrica; Borges Neto, Manuel Rangel [Centro Federal de Educacao Tecnologica de Petrolina (CEFET-PET), PE (Brazil)

2008-07-01

A non-isolated DC-AC converter with high voltage gain with two output sinusoidal voltage - 110 V and 220 V - and frequency 60 Hz for application in autonomous systems of electric power is proposed in this work. This topology consists of a boost converter with high voltage gain, based on three-state switching cell combined with a double half bridge inverter. This configuration type the size and the cost are reduced and the efficiency is gotten better, due to the reduced number of switches. The converters that compose this topology operate with high frequency, reducing the volume of the magnetic materials. can be mention as important characteristics: the voltage stress across the switches of the boost converter are low, due they be naturally clamped by one output filter capacitor, which allows the utilization of switches with lower conduction resistances, and the waveforms of the output voltage of the double half bridge inverter supplies for the load it is sinusoidal and it possesses low harmonic content. (author)

Flexible AC transmission systems modelling and control

CERN Document Server

Zhang, Xiao-Ping; Pal, Bikash

2012-01-01

The extended and revised second edition of this successful monograph presents advanced modeling, analysis and control techniques of Flexible AC Transmission Systems (FACTS). The book covers comprehensively a range of power-system control problems: from steady-state voltage and power flow control, to voltage and reactive power control, to voltage stability control, to small signal stability control using FACTS controllers. In the six years since the first edition of the book has been published research on the FACTS has continued to flourish while renewable energy has developed into a mature and

Reliability of emergency ac power systems at nuclear power plants

International Nuclear Information System (INIS)

Battle, R.E.; Campbell, D.J.

1983-07-01

Reliability of emergency onsite ac power systems at nuclear power plants has been questioned within the Nuclear Regulatory Commission (NRC) because of the number of diesel generator failures reported by nuclear plant licensees and the reactor core damage that could result from diesel failure during an emergency. This report contains the results of a reliability analysis of the onsite ac power system, and it uses the results of a separate analysis of offsite power systems to calculate the expected frequency of station blackout. Included is a design and operating experience review. Eighteen plants representative of typical onsite ac power systems and ten generic designs were selected to be modeled by fault trees. Operating experience data were collected from the NRC files and from nuclear plant licensee responses to a questionnaire sent out for this project

Non-sparking anodization process of AZ91D magnesium alloy under low AC voltage

Energy Technology Data Exchange (ETDEWEB)

Li, Weiping, E-mail: liweiping@buaa.edu.cn [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Li, Wen [AVIC Beijing Aeronautical Manufacturing Technology Research Institue, Beijing 100024 (China); Zhu, Liqun; Liu, Huicong; Wang, Xiaofang [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)

2013-04-20

Highlights: ► Four different processes appear on magnesium alloys with applied voltage increase. ► Non-sparking film formation process occurred in the range of 6–10 V AC. ► The film was composed of Mg{sub 2}SiO{sub 4} with a stable growth rate in 30 min. ► Film growth was a balance of electrochemical dissolution and chemical deposition. -- Abstract: Anodization is widely recognized as one of the most important surface treatments for magnesium alloys. However, since high voltage oxidation films are limited in some applications due to porosity and brittleness, it is worthwhile to explore the non-sparking oxidizing process. In this work, AZ91D was electrochemically anodized at different AC voltages in an electrolyte containing 120 g/L NaOH and 80 g/L Na{sub 2}SiO{sub 3}·9H{sub 2}O. The effects of voltage on the surface morphology, composition and reaction process, especially the non-sparking discharge anodic film formation process, were investigated. The results showed that four different processes would appear according to the applied voltage variation from 6 V to 40 V, and that the non-sparking film formation process occurred in the range of 6–10 V. The film formed on the AZ91D surface under 10 V AC was mainly composed of Mg{sub 2}SiO{sub 4} with a lamellar structure. The horizontal and vertical expansion of the lamellar structure resulted in the formation of a multi-layered structure with a stable, linear growth rate for 30 min. The non-sparking film formation process can be considered to be the result of a balance of electrochemical dissolution and chemical deposition reaction.

Modeling of HVDC System to Improve Estimation of Transient DC Current and Voltages for AC Line-to-Ground Fault—An Actual Case Study in Korea

Directory of Open Access Journals (Sweden)

Dohoon Kwon

2017-10-01

Full Text Available A new modeling method for high voltage direct current (HVDC systems and associated controllers is presented for the power system simulator for engineering (PSS/E simulation environment. The aim is to improve the estimation of the transient DC voltage and current in the event of an AC line-to-ground fault. The proposed method consists primary of three interconnected modules for (a equation conversion; (b control-mode selection; and (c DC-line modeling. Simulation case studies were carried out using PSS/E and a power systems computer aided design/electromagnetic transients including DC (PSCAD/EMTDC model of the Jeju– Haenam HVDC system in Korea. The simulation results are compared with actual operational data and the PSCAD/EMTDC simulation results for an HVDC system during single-phase and three-phase line-to-ground faults, respectively. These comparisons show that the proposed PSS/E modeling method results in the improved estimation of the dynamic variation in the DC voltage and current in the event of an AC network fault, with significant gains in computational efficiency, making it suitable for real-time analysis of HVDC systems.

An Annotated Bibliography of High-Voltage Direct-Current Transmission and Flexible AC Transmission (FACTS) Devices, 1991-1993.

Energy Technology Data Exchange (ETDEWEB)

Litzenberger, Wayne; Lava, Val

1994-08-01

References are contained for HVDC systems, converter stations and components, overhead transmission lines, cable transmission, system design and operations, simulation of high voltage direct current systems, high-voltage direct current installations, and flexible AC transmission system (FACTS).

21 CFR 880.5100 - AC-powered adjustable hospital bed.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false AC-powered adjustable hospital bed. 880.5100 Section 880.5100 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... Therapeutic Devices § 880.5100 AC-powered adjustable hospital bed. (a) Identification. An AC-powered...

Methods, systems and apparatus for controlling operation of two alternating current (AC) machines

Science.gov (United States)

Gallegos-Lopez, Gabriel [Torrance, CA; Nagashima, James M [Cerritos, CA; Perisic, Milun [Torrance, CA; Hiti, Silva [Redondo Beach, CA

2012-02-14

A system is provided for controlling two AC machines. The system comprises a DC input voltage source that provides a DC input voltage, a voltage boost command control module (VBCCM), a five-phase PWM inverter module coupled to the two AC machines, and a boost converter coupled to the inverter module and the DC input voltage source. The boost converter is designed to supply a new DC input voltage to the inverter module having a value that is greater than or equal to a value of the DC input voltage. The VBCCM generates a boost command signal (BCS) based on modulation indexes from the two AC machines. The BCS controls the boost converter such that the boost converter generates the new DC input voltage in response to the BCS. When the two AC machines require additional voltage that exceeds the DC input voltage required to meet a combined target mechanical power required by the two AC machines, the BCS controls the boost converter to drive the new DC input voltage generated by the boost converter to a value greater than the DC input voltage.

AC power flow importance measures considering multi-element failures

International Nuclear Information System (INIS)

Li, Jian; Dueñas-Osorio, Leonardo; Chen, Changkun; Shi, Congling

2017-01-01

Quantifying the criticality of individual components of power systems is essential for overall reliability and management. This paper proposes an AC-based power flow element importance measure, while considering multi-element failures. The measure relies on a proposed AC-based cascading failure model, which captures branch overflow, bus load shedding, and branch failures, via AC power flow and optimal power flow analyses. Taking the IEEE 30, 57 and 118-bus power systems as case studies, we find that N-3 analyses are sufficient to measure the importance of a bus or branch. It is observed that for a substation bus, its importance is statistically proportional to its power demand, but this trend is not observed for power plant buses. While comparing with other reliability, functionality, and topology-based importance measures popular today, we find that a DC power flow model, although better correlated with the benchmark AC model as a whole, still fails to locate some critical elements. This is due to the focus of DC-based models on real power that ignores reactive power. The proposed importance measure is aimed to inform decision makers about key components in complex systems, while improving cascading failure prevention, system backup setting, and overall resilience. - Highlights: • We propose a novel importance measure based on joint failures and AC power flow. • A cascading failure model considers both AC power flow and optimal power flow. • We find that N-3 analyses are sufficient to measure the importance of an element. • Power demand impacts the importance of substations but less so that of generators. • DC models fail to identify some key elements, despite correlating with AC models.

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

Model, Characterization, and Analysis of Steady-State Security Region in AC/DC Power System with a Large Amount of Renewable Energy

Directory of Open Access Journals (Sweden)

Zhong Chen

2017-08-01

Full Text Available A conventional steady-state power flow security check only implements point-by-point assessment, which cannot provide a security margin for system operation. The concept of a steady-state security region is proposed to effectively tackle this problem. Considering that the commissioning of the increasing number of HVDC (High Voltage Direct Current and the fluctuation of renewable energy have significantly affected the operation and control of a conventional AC system, the definition of the steady-state security region of the AC/DC power system is proposed in this paper based on the AC/DC power flow calculation model including LCC/VSC (Line Commutated Converter/Voltage Sourced Converter-HVDC transmission and various AC/DC constraints, and hence the application of the security region is extended. In order to ensure that the proposed security region can accurately provide global security information of the power system under the fluctuations of renewable energy, this paper presents four methods (i.e., a screening method of effective boundary surfaces, a fitting method of boundary surfaces, a safety judging method, and a calculation method of distances and corrected distance between the steady-state operating point and the effective boundary surfaces based on the relation analysis between the steady-state security region geometry and constraints. Also, the physical meaning and probability analysis of the corrected distance are presented. Finally, a case study is demonstrated to test the feasibility of the proposed methods.

Power conditioning system for energy sources

Science.gov (United States)

Mazumder, Sudip K [Chicago, IL; Burra, Rajni K [Chicago, IL; Acharya, Kaustuva [Chicago, IL

2008-05-13

Apparatus for conditioning power generated by an energy source includes an inverter for converting a DC input voltage from the energy source to a square wave AC output voltage, and a converter for converting the AC output voltage from the inverter to a sine wave AC output voltage.

Design and implementation of co-operative control strategy for hybrid AC/DC microgrids

Science.gov (United States)

Mahmud, Rasel

This thesis is mainly divided in two major sections: 1) Modeling and control of AC microgrid, DC microgrid, Hybrid AC/DC microgrid using distributed co-operative control, and 2) Development of a four bus laboratory prototype of an AC microgrid system. At first, a distributed cooperative control (DCC) for a DC microgrid considering the state-of-charge (SoC) of the batteries in a typical plug-in-electric-vehicle (PEV) is developed. In DC microgrids, this methodology is developed to assist the load sharing amongst the distributed generation units (DGs), according to their ratings with improved voltage regulation. Subsequently, a DCC based control algorithm for AC microgrid is also investigated to improve the performance of AC microgrid in terms of power sharing among the DGs, voltage regulation and frequency deviation. The results validate the advantages of the proposed methodology as compared to traditional droop control of AC microgrid. The DCC-based control methodology for AC microgrid and DC microgrid are further expanded to develop a DCC-based power management algorithm for hybrid AC/DC microgrid. The developed algorithm for hybrid microgrid controls the power flow through the interfacing converter (IC) between the AC and DC microgrids. This will facilitate the power sharing between the DGs according to their power ratings. Moreover, it enables the fixed scheduled power delivery at different operating conditions, while maintaining good voltage regulation and improved frequency profile. The second section provides a detailed explanation and step-by-step design and development of an AC/DC microgrid testbed. Controllers for the three-phase inverters are designed and tested on different generation units along with their corresponding inductor-capacitor-inductor (LCL) filters to eliminate the switching frequency harmonics. Electric power distribution line models are developed to form the microgrid network topology. Voltage and current sensors are placed in the proper

Enhancing the Capacity of the AC Distribution System Using DC Interlinks - A Step Towards Future DC Grid

DEFF Research Database (Denmark)

Chaudhary, Sanjay; Guerrero, Josep M.; Teodorescu, Remus

2015-01-01

The development of distributed generation system and electric vehicles is bound to strain the distribution network. A typical radial distribution feeder suffers from the voltage fluctuation and feeder overload in the presence of a large amount of variable renewable generation. This paper presents...... a concept of enhancing the power handling capacity of distribution networks using dc grid interconnections. Control of both the active and reactive power exchange between the ac feeder and the interconnecting power converter has been proposed for the voltage regulation at the ac feeder terminal. Besides......, the dc grid interconnection also allows the introduction of a common storage system which can be shared by the connected ac feeders, and the dc grid connection to other renewable energy resources. The increased power handling capacity and improved voltage profile of the ac distribution feeder using...

21 CFR 880.5500 - AC-powered patient lift.

Science.gov (United States)

2010-04-01

...) MEDICAL DEVICES GENERAL HOSPITAL AND PERSONAL USE DEVICES General Hospital and Personal Use Therapeutic Devices § 880.5500 AC-powered patient lift. (a) Identification. An AC-powered lift is an electrically powered device either fixed or mobile, used to lift and transport patients in the horizontal or other...

Investigation of plate-type barrier ozonizers with AC and pulse power supplies

International Nuclear Information System (INIS)

Krasnij, V.V.; Gubarev, S.P.; Pogoghev, D.P.; Sokolova, O.T.

2002-01-01

In this paper the experimental results on the investigation of plate-type reactors operated on the base of barrier discharge have been presented. Different reactors with planar, strip, and trench electrodes were investigated. Such reactors operated under atmospheric pressure with ac and pulse power sources with voltage of up to 10 kV, frequency up to 12 kHz. Using atomized spectroscopy system the measurements of the main specifications of the reactors such as ozone yielding rate, the temperature in the reactor and the air flow rate were carried out

Control of hybrid AC/DC microgrid under islanding operational conditions

DEFF Research Database (Denmark)

Ding, G.; Gao, F.; Zhang, S.

2014-01-01

This paper presents control methods for hybrid AC/DC microgrid under islanding operation condition. The control schemes for AC sub-microgrid and DC sub-microgrid are investigated according to the power sharing requirement and operational reliability. In addition, the key control schemes...... of interlinking converter with DC-link capacitor or energy storage, which will devote to the proper power sharing between AC and DC sub-microgrids to maintain AC and DC side voltage stable, is reviewed. Combining the specific control methods developed for AC and DC sub-microgrids with interlinking converter......, the whole hybrid AC/DC microgrid can manage the power flow transferred between sub-microgrids for improving on the operational quality and efficiency....

A Control Strategy of DC Building Microgrid Connected to the Neighborhood and AC Power Network

Directory of Open Access Journals (Sweden)

Thi Thuong Huyen Ma

2017-05-01

Full Text Available Recently, the use of DC microgrid distribution system has become more attractive than traditional AC systems due to their energy efficiency and ability to easily integrate with renewable energy sources and batteries. This paper proposes a 500 V DC microgrid which consists of a 20 kWp photovoltaic panel, batteries, and DC loads. A hierarchical control strategy to ensure balance power of the DC microgrid and the maintenance of common DC bus voltage is presented. The capability of exchanging power energy of the microgrid with the power system of neighborhood buildings is also considered. Typical operation modes are simulated in the Matlab/simulink environment to confirm the good performance of the controllers and the efficiency of appropriately controlling the charge–discharge of the battery system. This research is expected to bring benefits to the design and operation of the system, such as reducing the capacity of batteries, increasing the self-supply of buildings, and decreasing the electricity demand from the AC grid.

Dynamics of the resistive state of a narrow superconducting channel in the ac voltage-driven regime

International Nuclear Information System (INIS)

Yerin, Yu.S.; Fenchenko, V.N.

2013-01-01

Within the time-dependent Ginzburg-Landau equations the dynamics of the order parameter in superconducting narrow channels of different lengths is investigated in the ac voltage-driven regime. The resistive state of the system at low frequencies of the applied voltage is characterized by the formation of periodic-in-time groups of oscillating phase-slip centers (PSC). An increase in frequency reduces the duration of the existence of these periodic groups. Depending on the length of the channel the ac voltage either tends to revert the channel to the state with one central PSC in periodic groups or minimizes the number of forming PSCs and orders their pattern in the system. A further increase in frequency for rather short channels leads to suppression of the order parameter without any creation of PSCs. For systems, whose length exceeds the specified limit, the formation of PSC occurs after a certain time which increases rapidly with frequency. The current-voltage characteristics of rather short channels at different applied voltage frequencies are calculated too. It is found that the current-voltage characteristics have a step-like structure, and the height of the first step is determined by the quadruple value of the Josephson frequency.

Control of Power Converters in AC Microgrids

DEFF Research Database (Denmark)

Rocabert, Joan; Luna, Alvaro; Blaabjerg, Frede

2012-01-01

The enabling of ac microgrids in distribution networks allows delivering distributed power and providing grid support services during regular operation of the grid, as well as powering isolated islands in case of faults and contingencies, thus increasing the performance and reliability of the ele......The enabling of ac microgrids in distribution networks allows delivering distributed power and providing grid support services during regular operation of the grid, as well as powering isolated islands in case of faults and contingencies, thus increasing the performance and reliability...

Piezoelectric power converter with bi-directional power transfer

DEFF Research Database (Denmark)

2014-01-01

The present invention relates to a bi-directional piezoelectric power converter com¬ prising a piezoelectric transformer. The piezoelectric transformer comprises an input electrode electrically coupled to a primary section of the piezoelectric transformer and an output electrode electrically...... coupled to an output section of the piezoelectric transformer to provide a transformer output signal. A bi-directional switching circuit is coupled between the output electrode and a DC or AC output voltage of the power converter. Forward and reverse current conducting periods of the bi......, a reverse current is conducted through the bi-directional switching circuit from the DC or AC output voltage to the output electrode to discharge the DC or AC output voltage and return power to the primary section of the piezoelectric transformer....

Ultra-long-pulse microwave negative high voltage power supply with fast protection

International Nuclear Information System (INIS)

Xu Weihua; Wu Junshuan; Zheng Guanghua; Huang Qiaolin; Yang Chunsheng; Zhou Yuanwei; Chen Yonghao

1998-01-01

Two 1.4 MW high voltage power supply (HVPS) modules with 3-5 s pulse duration have been developed for LHCD experiment in the HT-7 tokamak. The power source consists of a pulsed generator and the electric circuit. Duration of the ultra-long-pulse is controlled by switching-on dc relay immediately and switching-off ac contactor after a given time, and the fast protection is executed by a crowbar. Due to the soft starting of the power source, the problem of overvoltage induced by dc relay switching-on has been solved. Each power supply module outputs a rated power (-35 kV, 40 A) on the dummy load. With the klystrons connected as the load of the power supply modules, LHCD experiments have been conducted successfully in the HT-7 tokamak

Control of a Two-Stage Direct Power Converter with a Single Voltage Sensor Mounted in the Intermediary Circuit

DEFF Research Database (Denmark)

Klumpner, Christian; Wheeler, P.; Blaabjerg, Frede

2004-01-01

Controlling a converter requires not only a powerful processors but also accurate voltage and current sensors and fast and precise analogue-digital converters, which increase the cost per kW of the assembly, especially in the low power range. A matrix converter requires less transducers than a back...... converters but in two stages (AC/DC/AC) without using energy storage in the intermediary circuit. They also offer the possibility to reduce the number of switches compared to the standard single-stage matrix converter. This paper presents a new method to control a two-stage DPC providing sine-wave in sine...

Reliability of the emergency AC power system at nuclear power plants

International Nuclear Information System (INIS)

Battle, R.E.; Campbell, D.J.; Baranowsky, P.W.

1983-01-01

The reliability of the emergency ac power systems typical of most nuclear power plants was estimated, and the cost and increase in reliability for several improvements were estimated. Fault trees were constructed based on a detailed design review of the emergency ac power systems of 18 nuclear plants. The failure probabilities used in the fault trees were calculated from extensive historical data collected from Licensee Event Reports (LERs) and from operating experience information obtained from nuclear plant licensees. No one or two improvements can be made at all plants to significantly increase the industry-average emergency ac power system reliability; rather the most beneficial improvements are varied and plant specific. Improvements in reliability and the associated costs are estimated using plant specific designs and failure probabilities

Comparison of the converter systems for a high-voltage variable-frequency AC drive

Directory of Open Access Journals (Sweden)

G.G. Zhemerov

2013-12-01

Full Text Available Matlab-models of two converter systems of an 8 MW AC drive are developed, one based on a self-contained current inverter with cut-off diodes, the other based on a multilevel cascade voltage inverter. By applying virtual simulation, qualitative characteristics of these systems are compared.

Autonomous Operation of a Hybrid AC/DC Microgrid with Multiple Interlinking Converters

DEFF Research Database (Denmark)

Peyghami, Saeed; Mokhtari, Hossein; Blaabjerg, Frede

2018-01-01

Applying conventional dc-voltage based droop approaches for hybrid ac/dc microgrids interconnected by a single interlinking converter (IC) can properly manage the power flow among ac and dc subgrids. However, due to the effect of line resistances, these approaches may create a circulating power a...

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

Reliability of the emergency ac-power system at nuclear power plants

International Nuclear Information System (INIS)

Battle, R.E.; Campbell, D.J.; Baranowsky, P.W.

1982-01-01

The reliability of the emergency ac-power systems typical of several nuclear power plants was estimated, the costs of several possible improvements was estimated. Fault trees were constructed based on a detailed design review of the emergency ac-power systems of 18 nuclear plants. The failure probabilities used in the fault trees were calculated from extensive historical data collected from Licensee Event Reports (LERs) and from operating experience information obtained from nuclear plant licensees. It was found that there are not one or two improvements that can be made at all plants to significantly increase the industry-average emergency ac-power-system reliability, but the improvements are varied and plant-specific. Estimates of the improvements in reliability and the associated cost are estimated using plant-specific designs and failure probabilities

Overmodulation of n-level three-leg DC-AC diode-clamped converters with comprehensive capacitor voltage balance

DEFF Research Database (Denmark)

Busquets-Monge, S.; Maheshwari, Ram Krishan; Munk-Nielsen, Stig

2013-01-01

This paper presents a novel PWM strategy for nlevel three-leg semiconductor-clamped dc-ac converters in the overmodulation region, with dc-link capacitor voltage balance in every switching cycle. The strategy is based on the virtual-vector concept. Suitable reference vector trajectories are selec......This paper presents a novel PWM strategy for nlevel three-leg semiconductor-clamped dc-ac converters in the overmodulation region, with dc-link capacitor voltage balance in every switching cycle. The strategy is based on the virtual-vector concept. Suitable reference vector trajectories...

Triple Line-Voltage Cascaded VIENNA Converter Applied as the Medium-Voltage AC Drive

Directory of Open Access Journals (Sweden)

Jia Zou

2018-04-01

Full Text Available A novel rectifier based on a triple line-voltage cascaded VIENNA converter (LVC-VC was proposed. Compared to the conventional cascaded H-bridge converters, the switch voltage stress is lower, and the numbers of switches and dc capacitors are fewer under similar operating conditions in the proposed new multilevel converter. The modeling and control for the LVC-VC ware presented. Based on the analysis of the operation principle of the new converter, the power factor correction of the proposed converter was realized by employing a traditional one-cycle control strategy. The minimum average value and maximum harmonic components of the dc-link voltages of the three VIENNA rectifier modules ware calculated. Three VIENNA dc-link voltages were unbalanced under the unbalanced load conditions, so the zero sequence current was injected to the three inner currents for balancing three VIENNA dc-link voltages. Simulation and the results of the experiment verified the availability of the new proposed multilevel converter and the effectiveness of the corresponding control strategy applied.

Self-field AC losses in Bi-2223 superconducting tapes

International Nuclear Information System (INIS)

Mueller, K. H.; Leslie, K.E.

1996-01-01

Full text: The self-field AC loss in Bi-2223 silver sheathed tapes for AC currents of up to 100 A was measured at 77 K and frequencies of 60 Hz and 600 Hz using a lock-in amplifier. The frequency dependence indicated a purely hysteretic loss which can be well described in terms of the critical state model for a flat superconducting strip. The only parameter needed to predict the self-field AC loss is the critical current of the critical state. Because the loss voltage is extremely small compared with the inductive voltage, a very high accuracy of the lock-in amplifier phase setting is required. Unlike in loss measurements on cylindrical superconducting samples, in the case of the tape the measuring circuit leads have to be brought out from the surface forming a loop where the changing magnetic field induces an additional voltage. Only if the loop formed by the leads at the voltage tabs is large enough will the apparent power dissipation approach the real AC loss associated with the length of the sample probed

Benchmark of AC and DC Active Power Decoupling Circuits for Second-Order Harmonic Mitigation in Kilowatt-Scale Single-Phase Inverters

DEFF Research Database (Denmark)

Qin, Zian; Tang, Yi; Loh, Poh Chiang

2016-01-01

efficiency and high power density is identified and comprehensively studied, and the commercially available film capacitors, the circuit topologies, and the control strategies adopted for active power decoupling are all taken into account. Then, an adaptive decoupling voltage control method is proposed...... to further improve the performance of dc decoupling in terms of efficiency and reliability. The feasibility and superiority of the identified solution for active power decoupling together with the proposed adaptive decoupling voltage control method are finally verified by both the simulation and experimental......This paper presents the benchmark study of ac and dc active power decoupling circuits for second order harmonic mitigation in kW scale single-phase inverters. First of all, a brief comparison of recently reported active power decoupling circuits is given, and the best solution that can achieve high...

Plasma antennas driven by 5–20 kHz AC power supply

Energy Technology Data Exchange (ETDEWEB)

Zhao, Jiansen, E-mail: 67093058@qq.com; Chen, Yuli; Sun, Yang; Wu, Huafeng; Liu, Yue; Yuan, Qiumeng [Merchant Marine College, Shanghai Maritime University, Shanghai, 201306 (China)

2015-12-15

The experiments described in this work were performed with the aim of introducing a new plasma antenna that was excited by a 5–20 kHz alternating current (AC) power supply, where the antenna was transformed into a U-shape. The results show that the impedance, voltage standing-wave ratio (VSWR), radiation pattern and gain characteristics of the antenna can be controlled rapidly by varying not only the discharge power, but also by varying the discharge frequency in the range from 5 to 20 kHz. When the discharge frequency is adjusted from 10 to 12 kHz, the gain is higher within a relatively broad frequency band and the switch-on time is less than 1 ms when the discharge power is less than 5 W, meaning that the plasma antenna can be turned on and off rapidly.

Corona Onset Characteristics of Bundle Conductors in UHV AC Power Lines at 2200 m Altitude

Directory of Open Access Journals (Sweden)

Shilong Huang

2018-04-01

Full Text Available The corona onset characteristic of bundle conductors is an important limiting factor for the design of UHV AC power lines in high-altitude areas. An experimental study on the corona characteristics of 8 × LGJ630, 6 × LGJ720, 8 × LGJ720 and 10 × LGJ720 bundle conductors commonly used in UHV power lines under dry and wet conductor conditions, as well as artificial moderate and heavy rain conditions, was conducted in Ping’an County, Xining City (elevation 2200 m. By using the tangent line method, the corona onset voltages and onset electric field of four types of conductors at high altitudes are obtained for the first time. In addition, the calculation model of corona onset voltage considering the outer strands’ effect on the electric field and the geometric factor in the corona cage in high altitude areas is established. The comparison of the calculation results and experimental results under dry conditions verifies the model’s correctness. Based on the results, an optimal selection scheme for high altitudes is proposed. The roughness coefficient was also calculated and analysed: the roughness coefficient of bundled conductors was between 0.59 and 0.77, and the roughness coefficient of the wet conductor was between the dry and rainy conditions. Both the experimental data and the calculation model can provide a reference for conductor selection for UHV AC power lines for use in high-altitude areas.

Analysis of Input and Output Ripples of PWM AC Choppers

Directory of Open Access Journals (Sweden)

Pekik Argo Dahono

2008-11-01

Full Text Available This paper presents an analysis of input and output ripples of PWM AC choppers. Expressions of input and output current and voltage ripples of single-phase PWM AC choppers are first derived. The derived expressions are then extended to three-phase PWM AC choppers. As input current and output voltage ripples specification alone cannot be used to determine the unique values of inductance and capacitance of the LC filters, an additional criterion based on the minimum reactive power is proposed. Experimental results are included in this paper to show the validity of the proposed analysis method.

AC Transmission Emulation Control Strategies for the BTB VSC HVDC System in the Metropolitan Area of Seoul

Directory of Open Access Journals (Sweden)

Sungyoon Song

2017-08-01

Full Text Available In the Korean power system, growing power loads have recently created the problems of voltage instability and fault current in the Seoul Capital Area (SCA. Accordingly, the back-to-back (BTB voltage source converter (VSC high-voltage direct-current (HVDC system is emerging to resolve such problems with grid segmentation. However, non-convergence problems occur in this metropolitan area, due to the large change of power flow in some contingencies. Therefore, this paper proposes two kinds of AC transmission emulation control (ATEC strategies to improve the metropolitan transient stability, and to resolve the non-convergence problem. The proposed ATEC strategies are able to mitigate possible overloading of adjacent AC transmission, and maintain power balance between metropolitan regions. The first ATEC strategy uses a monitoring system that permits the reverse power flow of AC transmission, and thus effectively improves the grid stability based on the power transfer equation. The second ATEC strategy emulates AC transmission with DC link capacitors in a permissible DC-link voltage range according to angle difference, and securely improves the gird stability, without requiring grid operator schedule decisions. This paper compares two kinds of ATEC schemes: it demonstrates the first ATEC strategy with specific fault scenario with PSS/E (Power Transmission System Planning Software, and evaluates the second ATEC strategy with internal controller performance with PSCAD/EMTDC (Power System Electromagnetic Transients Simulation Software.

Line voltage distortions due to operation of the power supply devices required for plasma heating and magnetic field generation in the W7X thermonuclear fusion experiment

International Nuclear Information System (INIS)

Werner, F.

1997-03-01

The operation of the W7-X plasma heating devices requires high voltage DC power supplies with a total electrical power of 40 MVA. For this purpose twelve-pulse AC/DC converters are projected. These converters enforce a non sinusoidal line current, whose harmonics are causing corresponding line voltage distortions. To evaluate the extent of these distortions, the reaction of the harmonic currents on the AC line, is investigated by numerical network analysis. This is done for both, the 20 kV-junction point of the converters and the 110 kV-line terminal of the electricity supply company. Furthermore the design of LC series-resonant circuits, projected for power factor correction and damping of the harmonic content of the line voltage, has been verified. The additional operation of the 1.5 MVA magnet power supplies also contributes, even though to a much smaller extent, to the line voltage distortion. The influence of these twelve-pulse AC/DC converters was investigated too. The numerical calculations have been done with the aid of the network simulation program 'Pspice'. In an equivalent circuit the transmission line network and the transformers are represented by their inductances respectively equivalent inductances. The rectifier units are simulated by a number of current sources, producing the current harmonics in amplitude, frequency and phase. The harmonics amplitudes of the plasma heating power supplies are frequency and phase. The harmonics amplitudes of the plasma heating power supplies are measured values given by the manufacturer. For the magnet power supplies, the harmonics are derived from the theoretical step like I(t) current shape by Fourier series decomposition. Due to the action of the LC circuits the achieved characteristic voltage quality values are far below the permissible values corresponding to the recommendations of VDE 0160. (orig.) [de

21 CFR 880.5510 - Non-AC-powered patient lift.

Science.gov (United States)

2010-04-01

...) MEDICAL DEVICES GENERAL HOSPITAL AND PERSONAL USE DEVICES General Hospital and Personal Use Therapeutic Devices § 880.5510 Non-AC-powered patient lift. (a) Identification. A non-AC-powered patient lift is a hydraulic, battery, or mechanically powered device, either fixed or mobile, used to lift and transport a...

Wind Power Plant Voltage Stability Evaluation: Preprint

Energy Technology Data Exchange (ETDEWEB)

Muljadi, E.; Zhang, Y. C.

2014-09-01

Voltage stability refers to the ability of a power system to maintain steady voltages at all buses in the system after being subjected to a disturbance from a given initial operating condition. Voltage stability depends on a power system's ability to maintain and/or restore equilibrium between load demand and supply. Instability that may result occurs in the form of a progressive fall or rise of voltages of some buses. Possible outcomes of voltage instability are the loss of load in an area or tripped transmission lines and other elements by their protective systems, which may lead to cascading outages. The loss of synchronism of some generators may result from these outages or from operating conditions that violate a synchronous generator's field current limit, or in the case of variable speed wind turbine generator, the current limits of power switches. This paper investigates the impact of wind power plants on power system voltage stability by using synchrophasor measurements.

Final design of the Korean AC/DC converters for the ITER coil power supply system

Energy Technology Data Exchange (ETDEWEB)

Oh, Jong-Seok, E-mail: jsoh@nfri.re.kr [ITER Korea, National Fusion Research Institute, Daejeon 305-806 (Korea, Republic of); Choi, Jungwan; Suh, Jae-Hak; Choi, Jihyun [ITER Korea, National Fusion Research Institute, Daejeon 305-806 (Korea, Republic of); Lee, Lacksang; Kim, Changwoo; Park, Hyungjin; Jo, Seongman; Lee, Seungyun; Hwang, Kwangcheol; Liu, Hyoyol [Dawonsys Corp., Siheung 429-450 (Korea, Republic of); Hong, Ki-Don; Sim, Dong-Joon; Lee, Jang-Soo [Hyosung Corp., Gongdeok-Dong, Seoul 121-720 (Korea, Republic of); Lee, Eui-Jae; Kwon, Yang-Hae; Lee, Dae-Yeol; Ko, Ki-Won; Kim, Jong-Min [Mobiis Corp., Yangjae-dong, Seoul 137-888 (Korea, Republic of); Song, Inho [ITER Organization, Route de Vinon sur Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France); and others

2015-10-15

The final design of the ITER TF, CS, CC and VS AC/DC converters has been completed to implement ITER requirements following the detailed design and refinements of the preliminary design. The number of parallel thyristors and the rating of fuses are coordinated to keep those devices within the explosion limit even under most severe fault conditions. The impedance of the converter transformer has been optimized taking into account the energization inrush current, short circuit current, reactive power consumption and the available DC voltage. To ensure system integrity, AC/DC converters are mechanically divided into transformers, AC busbars, 6-pulse bridges, DC interconnecting busbars and DC reactors, and then all subsystems are decoupled by flexible links. To provide stable real time network communication down to the converters, a one GbE link is deployed between master controllers and local controllers. IEEE 1588 is implemented to the embedded controllers for precision time synchronization. This paper describes the detailed solutions implemented in the final design for the ITER AC/DC converters with R&D results of converter prototypes.

High Efficiency Power Converter for Low Voltage High Power Applications

DEFF Research Database (Denmark)

Nymand, Morten

The topic of this thesis is the design of high efficiency power electronic dc-to-dc converters for high-power, low-input-voltage to high-output-voltage applications. These converters are increasingly required for emerging sustainable energy systems such as fuel cell, battery or photo voltaic based......, and remote power generation for light towers, camper vans, boats, beacons, and buoys etc. A review of current state-of-the-art is presented. The best performing converters achieve moderately high peak efficiencies at high input voltage and medium power level. However, system dimensioning and cost are often...

Benchmark of AC and DC active power decoupling circuits for second-order harmonic mitigation in kW-scale single-phase inverters

DEFF Research Database (Denmark)

Qin, Zian; Tang, Yi; Loh, Poh Chiang

2015-01-01

studied, where the commercially available film capacitors, circuit topologies, and control strategies for active power decoupling are all taken into account. Then, an adaptive decoupling voltage control method is proposed to further improve the performance of dc decoupling in terms of efficiency...... and reliability. The feasibility and superiority of the identified solution for active power decoupling together with the proposed adaptive decoupling voltage control method are finally verified by both the experimental results obtained on a 2 kW single-phase inverter.......This paper presents the benchmark study of ac and dc active power decoupling circuits for second-order harmonic mitigation in kW-scale single-phase inverters. First of all, the best solutions of active power decoupling to achieve high efficiency and power density are identified and comprehensively...

Risk Assessment Method of UHV AC/DC Power System under Serious Disasters

Directory of Open Access Journals (Sweden)

Rishang Long

2016-12-01

Full Text Available Based on the theory of risk assessment, the risk assessment method for an ultra-high voltage (UHV AC/DC hybrid power system under severe disaster is studied. Firstly, considering the whole process of cascading failure, a fast failure probability calculation method is proposed, and the whole process risk assessment model is established considering the loss of both fault stage and recovery stage based on Monte Carlo method and BPA software. Secondly, the comprehensive evaluation index system is proposed from the aspects of power system structure, fault state and economic loss, and the quantitative assessment of system risk is carried out by an entropy weight model. Finally, the risk assessment of two UHV planning schemes are carried out and compared, which proves the effectiveness of the research work.

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.

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.

Design and development of microcontroller based programmable ramp generator for AC-DC converter for simulating decay power transient in experimental facility for nuclear power plants

International Nuclear Information System (INIS)

Srivastava, Gaurava Deep; Kulkarni, R.D.

2015-01-01

In nuclear power plants, fuel is subjected to a wide range of power and temperature transients during normal and abnormal conditions. The reactor setback and step-back power pattern, fast temperature profile occurred during Loss of Coolant Accident and decay power followed by shutdown of power plant are the typical transients in nuclear power plant. For a variety of reactor engineering and reactor safety related study, one needs to simulate these transients in experimental facility. In experimental facilities, high response AC-DC converters are used to handle these power and temperature transients safely in a controlled manner for generating a database which is utilized for design of thermal hydraulic system, development of computer codes, study of reliability of reactor safety system, etc. for nuclear power plants. The paper presents the methodology developed for simulating the typical reactor decay power transient in an experimental facility. The design and simulation of AC-DC power electronic converter of 3 MW capacity is also presented. The microcontroller based programmable ramp generator is designed and hardware implemented for feeding reference voltage to the closed loop control system of AC-DC converter for obtaining the decay power profile at the converter output. The typical decay power transient of the nuclear power plant is divided into several small power ramps for simulating the transient. The signal corresponding to each power ramp is generated by programmable ramp generator and fed to the comparator for generating control signal for the converter. The actual decay power transient obtained from the converter is compared with the theoretical decay power transient. (author)

Study on emergency power control strategy for AC/DC hybrid power system containing VSC-HVDC

Science.gov (United States)

Liu, Lin; Hu, Zhenda; Ye, Rong; Lin, Zhangsui; Yang, Xiaodong; Yi, Yang

2018-04-01

This paper presents a comprehensive emergency power control strategy for AC/DC hybrid power systems containing VSC-HVDC. Firstly, the paper analyzes the power support of the VSC-HVDC to the AC lines using the Power Transferring Relativity Factor (PTRF). Then the power adjustment of the VSC-HVDC in several different circumstances are calculated. Finally, the online power control strategies of VSC-HVDC are designed, which could rapidly control the power of the VSC-HVDC, keeping the power flow of AC lines below the upper limit. Furthermore, the strategy is proven to be effective by the simulations with EMTDC/PSCAD.

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

Science.gov (United States)

Khoshkbar Sadigh, Arash

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

Proposal and Development of a High Voltage Variable Frequency Alternating Current Power System for Hybrid Electric Aircraft

Science.gov (United States)

Sadey, David J.; Taylor, Linda M.; Beach, Raymond F.

2017-01-01

The development of ultra-efficient commercial vehicles and the transition to low-carbon emission propulsion are seen as strategic thrust paths within NASA Aeronautics. A critical enabler to these paths comes in the form of hybrid electric propulsion systems. For megawatt-class systems, the best power system topology for these hybrid electric propulsion systems is debatable. Current proposals within NASA and the Aero community suggest using a combination of alternating current (AC) and direct current (DC) for power generation, transmission, and distribution. This paper proposes an alternative to the current thought model through the use of a primarily high voltage AC power system, supported by the Convergent Aeronautics Solutions (CAS) Project. This system relies heavily on the use of doubly-fed induction machines (DFIMs), which provide high power densities, minimal power conversion, and variable speed operation. The paper presents background on the activity along with the system architecture, development status, and preliminary results.

Development of AC-DC power system simulator

International Nuclear Information System (INIS)

Ichikawa, Tatsumi; Ueda, Kiyotaka; Inoue, Toshio

1984-01-01

A modeling and realization technique is described for realtime plant dynamics simulation of nuclear power generating unit in AC-DC power system simulator. Dynamic behavior of reactor system and steam system is important for investigation a further adequate unit control and protection system to system faults in AC and DC power system. Each unit of two nuclear power generating unit in the power system simulator consists of micro generator, DC motors, flywheels and process computer. The DC motor and flywheel simulates dynamic characteristics of steam turbine, and process computer simulates plant dynamics by digital simulation. We have realized real-time plant dynamics simulation by utilizing a high speed process I/O and a high speed digital differential analyzing processor (DDA) in which we builted a newly developed simple plant model. (author)

A Case Study of Wind-PV-Thermal-Bundled AC/DC Power Transmission from a Weak AC Network

Science.gov (United States)

Xiao, H. W.; Du, W. J.; Wang, H. F.; Song, Y. T.; Wang, Q.; Ding, J.; Chen, D. Z.; Wei, W.

2017-05-01

Wind power generation and photovoltaic (PV) power generation bundled with the support by conventional thermal generation enables the generation controllable and more suitable for being sent over to remote load centre which are beneficial for the stability of weak sending end systems. Meanwhile, HVDC for long-distance power transmission is of many significant technique advantages. Hence the effects of wind-PV-thermal-bundled power transmission by AC/DC on power system have become an actively pursued research subject recently. Firstly, this paper introduces the technical merits and difficulties of wind-photovoltaic-thermal bundled power transmission by AC/DC systems in terms of meeting the requirement of large-scale renewable power transmission. Secondly, a system model which contains a weak wind-PV-thermal-bundled sending end system and a receiving end system in together with a parallel AC/DC interconnection transmission system is established. Finally, the significant impacts of several factors which includes the power transmission ratio between the DC and AC line, the distance between the sending end system and receiving end system, the penetration rate of wind power and the sending end system structure on system stability are studied.

Voltage Flicker Mitigation in Electric Arc Furnace using D-STATCOM

OpenAIRE

Deepthisree Madathil; Ilango Karuppasamy; Kirthika Devi V S; Manjula G Nair

2014-01-01

The major power quality issue of voltage flicker has resulted as a serious concern for the customers and heavy power companies. Voltage flicker is an impression of unsteadiness of visual sensation induced by a light source whose luminance fluctuates with time. This phenomenon is experienced when an Electric Arc Furnace (EAF) as load is connected to the power system. Flexible AC transmission devices (FACTS) devices were gradually utilized for voltage flicker reduction. In this paper the FACTS ...

Combined operation of AC and DC distribution system with distributed generation units

International Nuclear Information System (INIS)

Noroozian, R.; Abedi, M.; Gharehpetian, G.

2010-01-01

This paper presents a DC distribution system which has been supplied by external AC systems as well as local DG units in order to demonstrate an overall solution to power quality issue. In this paper, the proposed operation method is demonstrated by simulation of power transfer between external AC systems, DG units, AC and DC loads. The power flow control in DC distribution system has been achieved by network converters and DG converters. Also, the mathematical model of the network, DG and load converters are obtained by using the average technique, which allows converter systems accurately simulated and control strategies for this converters is achieved. A suitable control strategy for network converters has been proposed that involves DC voltage droop regulator and novel instantaneous power regulation scheme. Also, a novel control technique has been proposed for DG converters. In this paper, a novel control system based on stationary and synchronously rotating reference frame has been proposed for load converters for supplying AC loads connected to the DC bus by balanced voltages. The several case studies have been studied based on proposed methods. The simulation results show that DC distribution systems including DG units can improve the power quality at the point of common coupling (PCC) in the power distribution system or industrial power system. (authors)

AC Power Local Network with Multiple Power Routers

Directory of Open Access Journals (Sweden)

Ryo Takahashi

2013-12-01

Full Text Available Controlling power flow and achieving appropriate matching between power sources and loads according to the quality of energy is expected to be one of the approaches to reduce wasted energy consumption. A power router, proposed recently, has the capability of realizing circuit switching in a power distribution network. This study focuses on the feasibility of an AC power routing network system composed of multiple power routers. To evaluate the feasibility, we experimentally confirm the circuit switching operation of the parallel and series configurations of the power routers, so that the network system can be designed by the combination of parallel and series configurations.

Characterization and snubbing of a bidirectional MCT in a resonant ac link converter

Science.gov (United States)

Lee, Tony; Elbuluk, Malik E.; Zinger, Donald S.

1993-01-01

The MOS-Controlled Thyristor (MCT) is emerging as a powerful switch that combines the better characteristics of existing power devices. A study of switching stresses on an MCT switch under zero voltage resonant switching is presented. The MCT is used as a bidirectional switch in an ac/ac pulse density modulated inverter for induction motor drive. Current and voltage spikes are observed and analyzed with variations in the timing of the switching. Different snubber circuit configurations are under investigation to minimize the effect of these transients. The results will be extended to study and test the MCT switching in a medium power (5 hp) induction motor drive.

Power Quality Control and Design of Power Converter for Variable-Speed Wind Energy Conversion System with Permanent-Magnet Synchronous Generator

Directory of Open Access Journals (Sweden)

Yüksel Oğuz

2013-01-01

Full Text Available The control strategy and design of an AC/DC/AC IGBT-PMW power converter for PMSG-based variable-speed wind energy conversion systems (VSWECS operation in grid/load-connected mode are presented. VSWECS consists of a PMSG connected to a AC-DC IGBT-based PWM rectifier and a DC/AC IGBT-based PWM inverter with LCL filter. In VSWECS, AC/DC/AC power converter is employed to convert the variable frequency variable speed generator output to the fixed frequency fixed voltage grid. The DC/AC power conversion has been managed out using adaptive neurofuzzy controlled inverter located at the output of controlled AC/DC IGBT-based PWM rectifier. In this study, the dynamic performance and power quality of the proposed power converter connected to the grid/load by output LCL filter is focused on. Dynamic modeling and control of the VSWECS with the proposed power converter is performed by using MATLAB/Simulink. Simulation results show that the output voltage, power, and frequency of VSWECS reach to desirable operation values in a very short time. In addition, when PMSG based VSWECS works continuously with the 4.5 kHz switching frequency, the THD rate of voltage in the load terminal is 0.00672%.

Power quality control and design of power converter for variable-speed wind energy conversion system with permanent-magnet synchronous generator.

Science.gov (United States)

Oğuz, Yüksel; Güney, İrfan; Çalık, Hüseyin

2013-01-01

The control strategy and design of an AC/DC/AC IGBT-PMW power converter for PMSG-based variable-speed wind energy conversion systems (VSWECS) operation in grid/load-connected mode are presented. VSWECS consists of a PMSG connected to a AC-DC IGBT-based PWM rectifier and a DC/AC IGBT-based PWM inverter with LCL filter. In VSWECS, AC/DC/AC power converter is employed to convert the variable frequency variable speed generator output to the fixed frequency fixed voltage grid. The DC/AC power conversion has been managed out using adaptive neurofuzzy controlled inverter located at the output of controlled AC/DC IGBT-based PWM rectifier. In this study, the dynamic performance and power quality of the proposed power converter connected to the grid/load by output LCL filter is focused on. Dynamic modeling and control of the VSWECS with the proposed power converter is performed by using MATLAB/Simulink. Simulation results show that the output voltage, power, and frequency of VSWECS reach to desirable operation values in a very short time. In addition, when PMSG based VSWECS works continuously with the 4.5 kHz switching frequency, the THD rate of voltage in the load terminal is 0.00672%.

Modular high voltage power supply for chemical analysis

Science.gov (United States)

Stamps, James F [Livermore, CA; Yee, Daniel D [Dublin, CA

2008-07-15

A high voltage power supply for use in a system such as a microfluidics system, uses a DC-DC converter in parallel with a voltage-controlled resistor. A feedback circuit provides a control signal for the DC-DC converter and voltage-controlled resistor so as to regulate the output voltage of the high voltage power supply, as well as, to sink or source current from the high voltage supply.

Offshore wind power plants with VSC-HVDC transmission : Grid code compliance optimization and the effect on high voltage ac transmission system

NARCIS (Netherlands)

Ndreko, M.

2017-01-01

The development of large offshore wind power generation in the North Sea has been significantly accelerated in the last years. The large distance from shore in combination with the need for large transmission capacity has raised the interest for the voltage source converter high voltage direct

E-beam high voltage switching power supply

Science.gov (United States)

Shimer, Daniel W.; Lange, Arnold C.

1997-01-01

A high power, solid state power supply is described for producing a controllable, constant high voltage output under varying and arcing loads suitable for powering an electron beam gun or other ion source. The present power supply is most useful for outputs in a range of about 100-400 kW or more. The power supply is comprised of a plurality of discrete switching type dc-dc converter modules, each comprising a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, and an output rectifier for producing a dc voltage at the output of each module. The inputs to the converter modules are fed from a common dc rectifier/filter and are linked together in parallel through decoupling networks to suppress high frequency input interactions. The outputs of the converter modules are linked together in series and connected to the input of the transmission line to the load through a decoupling and line matching network. The dc-dc converter modules are phase activated such that for n modules, each module is activated equally 360.degree./n out of phase with respect to a successive module. The phased activation of the converter modules, combined with the square current waveforms out of the step up transformers, allows the power supply to operate with greatly reduced output capacitance values which minimizes the stored energy available for discharge into an electron beam gun or the like during arcing. The present power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle using simulated voltage feedback signals and voltage feedback loops. Circuitry is also provided for sensing incipient arc currents reflected at the output of the power supply and for simultaneously decoupling the power supply circuitry from the arcing load.

E-beam high voltage switching power supply

International Nuclear Information System (INIS)

Shimer, D.W.; Lange, A.C.

1997-01-01

A high power, solid state power supply is described for producing a controllable, constant high voltage output under varying and arcing loads suitable for powering an electron beam gun or other ion source. The present power supply is most useful for outputs in a range of about 100-400 kW or more. The power supply is comprised of a plurality of discrete switching type dc-dc converter modules, each comprising a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, and an output rectifier for producing a dc voltage at the output of each module. The inputs to the converter modules are fed from a common dc rectifier/filter and are linked together in parallel through decoupling networks to suppress high frequency input interactions. The outputs of the converter modules are linked together in series and connected to the input of the transmission line to the load through a decoupling and line matching network. The dc-dc converter modules are phase activated such that for n modules, each module is activated equally 360 degree/n out of phase with respect to a successive module. The phased activation of the converter modules, combined with the square current waveforms out of the step up transformers, allows the power supply to operate with greatly reduced output capacitance values which minimizes the stored energy available for discharge into an electron beam gun or the like during arcing. The present power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle using simulated voltage feedback signals and voltage feedback loops. Circuitry is also provided for sensing incipient arc currents reflected at the output of the power supply and for simultaneously decoupling the power supply circuitry from the arcing load. 7 figs

Direct current power delivery system and method

Science.gov (United States)

Zhang, Di; Garces, Luis Jose; Dai, Jian; Lai, Rixin

2016-09-06

A power transmission system includes a first unit for carrying out the steps of receiving high voltage direct current (HVDC) power from an HVDC power line, generating an alternating current (AC) component indicative of a status of the first unit, and adding the AC component to the HVDC power line. Further, the power transmission system includes a second unit for carrying out the steps of generating a direct current (DC) voltage to transfer the HVDC power on the HVDC power line, wherein the HVDC power line is coupled between the first unit and the second unit, detecting a presence or an absence of the added AC component in the HVDC power line, and determining the status of the first unit based on the added AC component.

Influence of the electrolyte distribution near the micropores of the activated carbon (AC) electrode on high rate performance of high voltage capacitors

International Nuclear Information System (INIS)

Lee, Chung ho; Xu, Fan; Jung, Cheolsoo

2014-01-01

Highlights: • TFB can enhance the rate performance of high voltage capacitors. • TFB can suppress to increase the discharge slope to improve the cell performance. • TFB decreases the charge transfer resistance of an AC cell. • TFB affects the distribution of the electrolyte components near the microporous AC. - Abstract: This paper presents a method to enhance the rate performance of high voltage capacitors using an electrolyte additive, 1,3,5-trifluorobenzene (TFB). With increasing discharge rate, the capacity of the activated carbon (AC)/lithium (Li) cell decreases with increasing the slope of the discharge curve and its potential drop at 4.6 V. By adding TFB, the discharge slope improves to increase the rate performance of the cell, and EIS showed that the charge transfer resistance (Rc) of the AC cell decreases. These results suggest that TFB affects the distribution of the electrolyte components near the microporous AC and improves the rate performance of the AC cell

Power flow controller with a fractionally rated back-to-back converter

Science.gov (United States)

Divan, Deepakraj M.; Kandula, Rajendra Prasad; Prasai, Anish

2016-03-08

A power flow controller with a fractionally rated back-to-back (BTB) converter is provided. The power flow controller provide dynamic control of both active and reactive power of a power system. The power flow controller inserts a voltage with controllable magnitude and phase between two AC sources at the same frequency; thereby effecting control of active and reactive power flows between the two AC sources. A transformer may be augmented with a fractionally rated bi-directional Back to Back (BTB) converter. The fractionally rated BTB converter comprises a transformer side converter (TSC), a direct-current (DC) link, and a line side converter (LSC). By controlling the switches of the BTB converter, the effective phase angle between the two AC source voltages may be regulated, and the amplitude of the voltage inserted by the power flow controller may be adjusted with respect to the AC source voltages.

Proportional-Integral-Resonant AC Current Controller

Directory of Open Access Journals (Sweden)

STOJIC, D.

2017-02-01

Full Text Available In this paper an improved stationary-frame AC current controller based on the proportional-integral-resonant control action (PIR is proposed. Namely, the novel two-parameter PIR controller is applied in the stationary-frame AC current control, accompanied by the corresponding parameter-tuning procedure. In this way, the proportional-resonant (PR controller, common in the stationary-frame AC current control, is extended by the integral (I action in order to enable the AC current DC component tracking, and, also, to enable the DC disturbance compensation, caused by the voltage source inverter (VSI nonidealities and by nonlinear loads. The proposed controller parameter-tuning procedure is based on the three-phase back-EMF-type load, which corresponds to a wide range of AC power converter applications, such as AC motor drives, uninterruptible power supplies, and active filters. While the PIR controllers commonly have three parameters, the novel controller has two. Also, the provided parameter-tuning procedure needs only one parameter to be tuned in relation to the load and power converter model parameters, since the second controller parameter is directly derived from the required controller bandwidth value. The dynamic performance of the proposed controller is verified by means of simulation and experimental runs.

High Current, Low Voltage Power Converter [20kA, 6V] LHC Converter Prototype

CERN Document Server

Jørgensen, H E; Dupaquier, A; Fernqvist, G

1998-01-01

The superconducting LHC accelerator requires high currents (~12.5kA) and relatively low voltages (~10 V) for its magnets. The need to install the power converters underground is the driving force for reduced volume and high efficiency. Moreover, the LHC machine will require a very high level of performance from the power converters, particularly in terms of DC stability, dynamic response and also in matters of EMC. To meet these requirements soft-switching techniques will be used. This paper describes the development of a [20kA,6V] power converter intended as a stable high-current source for D CCT calibration and an evaluation prototype for the future LHC converters. The converter is made with a modular concept with five current sources [4kA,6V] in parallel. The 4kA sources are built as plu g-in modules: a diode rectifier on the AC mains with a damped L-C passive filter, a Zero Voltage Switching inverter working at 20 kHz and an output stage (high frequency transformers, Schottky rectifi ers and output filter...

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.

Voltage sags impact on CAR and SOR of HANARO

International Nuclear Information System (INIS)

Kim, Hyung Kyoo; Jung, Hoan Sung; Wu, Jong Sup

2004-01-01

The combination of the unstable electric power and sensitive equipment may cause the nuisance of reactor trip. The reactor is tripped by the RRS and RPS during the occurrence of the voltage sags or momentary interruptions. We tested the components of RRS and RPS for the immunity from voltage sags and momentary interruptions. The tested components are DC power supply for CAR (control absorbed rod) of RRS and AC coil contactor for SOR (shut off rod) of RPS. We briefly describe the power quality standard for the voltage sags. This paper summarizes the magnitudes and durations of the voltage sags which impact on the CAR and SOR system

High Efficiency Power Converter for Low Voltage High Power Applications

DEFF Research Database (Denmark)

Nymand, Morten

The topic of this thesis is the design of high efficiency power electronic dc-to-dc converters for high-power, low-input-voltage to high-output-voltage applications. These converters are increasingly required for emerging sustainable energy systems such as fuel cell, battery or photo voltaic based...

An Examination of AC/HVDC Power Circuits for Interconnecting Bulk Wind Generation with the Electric Grid

Directory of Open Access Journals (Sweden)

Daniel Ludois

2010-06-01

Full Text Available The application of high voltage dc (HVDC transmission for integrating large scale and/or off-shore wind generation systems with the electric grid is attractive in comparison to extra high voltage (EHV ac transmission due to a variety of reasons. While the technology of classical current sourced converters (CSC using thyristors is well established for realization of large HVDC systems, the technology of voltage sourced converters (VSC is emerging to be an alternative approach, particularly suitable for multi-terminal interconnections. More recently, a more modular scheme that may be termed ‘bridge of bridge’ converters (BoBC has been introduced to realize HVDC systems. While all these three approaches are functionally capable of realizing HVDC systems, the converter power circuit design trade-offs between these alternatives are not readily apparent. This paper presents an examination of these topologies from the point of view of power semiconductor requirements, reactive component requirements, operating losses, fault tolerance, multi-terminal operation, modularity, complexity, etc. Detailed analytical models will be used along with a benchmark application to develop a comparative evaluation of the alternatives that maybe used by wind energy/bulk transmission developers for performing engineering trade-off studies.

Efficiency estimation method of three-wired AC to DC line transfer

Science.gov (United States)

Solovev, S. V.; Bardanov, A. I.

2018-05-01

The development of power semiconductor converters technology expands the scope of their application to medium voltage distribution networks (6-35 kV). Particularly rectifiers and inverters of appropriate power capacity complement the topology of such voltage level networks with the DC links and lines. The article presents a coefficient that allows taking into account the increase of transmission line capacity depending on the parameters of it. The application of the coefficient is presented by the example of transfer three-wired AC line to DC in various methods. Dependences of the change in the capacity from the load power factor of the line and the reactive component of the resistance of the transmission line are obtained. Conclusions are drawn about the most efficient ways of converting a three-wired AC line to direct current.

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 in low voltage microgrids in aspects of active and reactive power demand

Directory of Open Access Journals (Sweden)

Parol Mirosław

2016-03-01

Full Text Available Low voltage microgrids are autonomous subsystems, in which generation, storage and power and electrical energy consumption appear. In the paper the main attention has been paid to the voltage stability issue in low voltage microgrid for different variants of its operation. In the introduction a notion of microgrid has been presented, and also the issue of influence of active and reactive power balance on node voltage level has been described. Then description of voltage stability issue has been presented. The conditions of voltage stability and indicators used to determine voltage stability margin in the microgrid have been described. Description of the low voltage test microgrid, as well as research methodology along with definition of considered variants of its operation have been presented further. The results of exemplary calculations carried out for the daily changes in node load of the active and reactive power, i.e. the voltage and the voltage stability margin indexes in nodes have been presented. Furthermore, the changes of voltage stability margin indexes depending on the variant of the microgrid operation have been presented. Summary and formulation of conclusions related to the issue of voltage stability in microgrids have been included at the end of the paper.

EHV AC undergrounding electrical power performance and planning

CERN Document Server

Benato, Roberto

2014-01-01

Analytical methods of cable performance in EHV AC electrical power are discussed in this comprehensive reference. Descriptions of energization, power quality, cable safety constraints and more, guide readers in cable planning and power network operations.

Flow reversal at low voltage and low frequency in a microfabricated ac electrokinetic pump

DEFF Research Database (Denmark)

Gregersen, Misha Marie; Olesen, Laurits Højgaard; Brask, Anders

2007-01-01

measured in a regime, where both the applied voltage and the frequency are low, Vrms1.5 V and f20 kHz, compared to previously investigated parameter ranges. The impedance spectrum has been thoroughly measured and analyzed in terms of an equivalent circuit diagram to rule out trivial circuit explanations......Microfluidic chips have been fabricated in Pyrex glass to study electrokinetic pumping generated by a low-voltage ac bias applied to an in-channel asymmetric metallic electrode array. A measurement procedure has been established and followed carefully resulting in a high degree of reproducibility...... of the measurements over several days. A large coverage fraction of the electrode array in the microfluidic channels has led to an increased sensitivity allowing for pumping measurements at low bias voltages. Depending on the ionic concentration a hitherto unobserved reversal of the pumping direction has been...

Analysis and implementation of power managment and control strategy for six-phase multilevel ac drive system in fault condition

DEFF Research Database (Denmark)

Sanjeevikumar, P.; Grandi, Gabriele; Blaabjerg, Frede

2016-01-01

sources. The developed post-fault algorithm is applied when there is a fault by one VSI and the load is fed from the remaining three healthy VSIs. In faulty conditions the multilevel outputs are reduced from 3-level to 2-level, but still the system propagates with degraded power. Numerical simulation......This research article exploits the power management algorithm in post-fault conditions for a six-phase (quad) multilevel inverter. The drive circuit consists of four 2-level, three-phase voltage source inverter (VSI) supplying a six-phase open-end windings motor or/impedance load......, with circumstantial failure of one VSI investigated. A simplified level-shifted pulse-width modulation (PWM) algorithm is developed to modulate each couple of three-phase VSI as 3-level output voltage generators in normal operation. The total power of the whole ac drive is shared equally among the four isolated DC...

Coordinated system services from offshore wind power plants connected through HVDC networks

DEFF Research Database (Denmark)

Zeni, Lorenzo; Glasdam, Jakob; Hesselbæk, Bo

2014-01-01

This paper presents an overview of power system services in networks involving multiple onshore power systems, a voltage sourced converter (VSC) based high voltage direct current (HVDC) offshore network and an offshore wind power plant (OWPP). A comprehensive list of services regarding onshore...... as well as offshore network operation – both AC and DC – will be discussed from a state of the art perspective. Among them, the most interesting have been selected and will be treated in more detail and the main contribution of this paper will be to shed light on the most relevant aspects related...... to their implementation. For example, new findings on onshore AC voltage control are reported, that help the characterisation of potential AC voltage control that a VSC-HVDC station may offer to an onshore AC grid. The HVDC system behind the VSC-HVDC station may connect, through other converters, to another AC power...

Synchronverter-Enabled DC Power Sharing Approach for LVDC Microgrids

DEFF Research Database (Denmark)

Peyghami, Saeed; Davari, Pooya; Mokhtari, Hossein

2017-01-01

by introducing a small ac voltage superimposed onto the output dc voltage of converters. Therefore, dc sources can be coordinated together with the frequency of the ac voltage, without any communication network like Synchronous Generators (SGs) in conventional power systems. Small signal stability analysis......In a classical ac Micro-Grid (MG), a common frequency exists for coordinating active power sharing among droop-controlled sources. Like the frequency droop method, a voltage based droop approach has been employed to control the converters in dc MGs. However, voltage variation due to the droop gains...... and line resistances causes poor power sharing and voltage regulation in dc MG, which in most cases are solved by a secondary controller using a communication network. To avoid such an infrastructure and its accompanied complications, this paper proposes a new droop scheme to control dc sources...

A new on-chip all-digital three-phase full-bridge dc/ac power inverter with feedforward and frequency control techniques.

Science.gov (United States)

Chen, Jiann-Jong; Kung, Che-Min

2010-09-01

The communication speed between components is far from satisfactory. To achieve high speed, simple control system configuration, and low cost, a new on-chip all-digital three-phase dc/ac power inverter using feedforward and frequency control techniques is proposed. The controller of the proposed power inverter, called the shift register, consists of six-stage D-latch flip-flops with a goal of achieving low-power consumption and area efficiency. Variable frequency is achieved by controlling the clocks of the shift register. One advantage regarding the data signal (D) and the common clock (CK) is that, regardless of the phase difference between the two, all of the D-latch flip-flops are capable of delaying data by one CK period. To ensure stability, the frequency of CK must be six times higher than that of D. The operation frequency of the proposed power inverter ranges from 10 Hz to 2 MHz, and the maximum output loading current is 0.8 A. The prototype of the proposed circuit has been fabricated with TSMC 0.35 μm 2P4M CMOS processes. The total chip area is 2.333 x 1.698 mm2. The three-phase dc/ac power inverter is applicable in uninterrupted power supplies, cold cathode fluorescent lamps, and motors, because of its ability to convert the dc supply voltage into the three-phase ac power sources.

THE MATHEMATIC STIMULATION OF TRANSIENT PROCESS IN A.C. – SYSTEM “ELECTRIC-TRACTION NETWORK – LOCOMOTIVE” 3. SWITCHING ON MAIN POWER CONVERTER IN “FREE PLAY” MODE; THE ANALYSIS OF VOLTS AND CURRENTS IN THE POWER SUPPLY INPUT SYSTEM

OpenAIRE

T. M. Mischenko

2011-01-01

The article is a continuation of analysis of the electric equivalent AC circuit «traction substation − device of transversal compensation − electric-traction network − electric locomotive DS 3» and the influence on a power transformer in the idle mode, depending on the feeder voltage and the distance of an electric locomotive from a traction substation. The numeral calculations are performed and the voltage and current values in the electric power supply system are analyzed.

Capturing power at higher voltages from arrays of microbial fuel cells without voltage reversal

KAUST Repository

Kim, Younggy

2011-01-01

Voltages produced by microbial fuel cells (MFCs) cannot be sustainably increased by linking them in series due to voltage reversal, which substantially reduces stack voltages. It was shown here that MFC voltages can be increased with continuous power production using an electronic circuit containing two sets of multiple capacitors that were alternately charged and discharged (every one second). Capacitors were charged in parallel by the MFCs, but linked in series while discharging to the circuit load (resistor). The parallel charging of the capacitors avoided voltage reversal, while discharging the capacitors in series produced up to 2.5 V with four capacitors. There were negligible energy losses in the circuit compared to 20-40% losses typically obtained with MFCs using DC-DC converters to increase voltage. Coulombic efficiencies were 67% when power was generated via four capacitors, compared to only 38% when individual MFCs were operated with a fixed resistance of 250 Ω. The maximum power produced using the capacitors was not adversely affected by variable performance of the MFCs, showing that power generation can be maintained even if individual MFCs perform differently. Longer capacitor charging and discharging cycles of up to 4 min maintained the average power but increased peak power by up to 2.6 times. These results show that capacitors can be used to easily obtain higher voltages from MFCs, allowing for more useful capture of energy from arrays of MFCs. © 2011 The Royal Society of Chemistry.

A Three-Phase Dual-Input Matrix Converter for Grid Integration of Two AC Type Energy Resources

DEFF Research Database (Denmark)

Liu, Xiong; Wang, Peng; Chiang Loh, Poh

2013-01-01

This paper proposes a novel dual-input matrix converter (DIMC) to integrate two three-phase ac type energy resources to a power grid. The proposed matrix converter is developed based on the traditional indirect matrix converter under reverse power flow operation mode, but with its six......-to-output voltage boost capability since power flows from the converter’s voltage source side to its current source side. Commanded currents can be extracted from the two input sources to the grid. The proposed control and modulation schemes guarantee sinusoidal input and output waveforms as well as unity input......-switch voltage source converter replaced by a nine-switch configuration. With the additional three switches, the proposed DIMC can provide six in put terminals, which make it possible to integrate two independent ac sources into a single grid-tied power electronics interface. The proposed converter has input...

Electrical power inverter having a phase modulated, twin-inverter, high frequency link and an energy storage module

Science.gov (United States)

Pitel, I.J.

1987-02-03

The present invention provides an electrical power inverter method and apparatus, which includes a high frequency link, for converting DC power into AC power. Generally stated, the apparatus includes a first high frequency module which produces an AC voltage at a first output frequency, and a second high frequency inverter module which produces an AC voltage at a second output frequency that is substantially the same as the first output frequency. The second AC voltage is out of phase with the first AC voltage by a selected angular phase displacement. A mixer mixes the first and second output voltages to produce a high frequency carrier which has a selected base frequency impressed on the sidebands thereof. A rectifier rectifies the carrier, and a filter filters the rectified carrier. An output inverter inverts the filtered carrier to produce an AC line voltage at the selected base frequency. A phase modulator adjusts the relative angular phase displacement between the outputs of the first and second high frequency modules to control the base frequency and magnitude of the AC line voltage. 19 figs.

Electrical power inverter having a phase modulated, twin-inverter, high frequency link and an energy storage module

Science.gov (United States)

Pitel, Ira J.

1987-02-03

The present invention provides an electrical power inverter method and apparatus, which includes a high frequency link, for converting DC power into AC power. Generally stated, the apparatus includes a first high frequency module which produces an AC voltage at a first output frequency, and a second high frequency inverter module which produces an AC voltage at a second output frequency that is substantially the same as the first output frequency. The second AC voltage is out of phase with the first AC voltage by a selected angular phase displacement. A mixer mixes the first and second output voltages to produce a high frequency carrier which has a selected base frequency impressed on the sidebands thereof. A rectifier rectifies the carrier, and a filter filters the rectified carrier. An output inverter inverts the filtered carrier to produce an AC line voltage at the selected base frequency. A phase modulator adjusts the relative angular phase displacement between the outputs of the first and second high frequency modules to control the base frequency and magnitude of the AC line voltage.

LOW-POWER AC LOADS AND ELECTRICAL POWER QUALITY

Directory of Open Access Journals (Sweden)

EPURE S.

2016-12-01

Full Text Available This paper deals with experimental study and numerical simulation of single phase AC low power loads: artificial light sources, personal computers, refrigeration units, air conditioning units and TV receivers. These loads are in such large numbers that represents the main source of disturbances (harmonic current, reactive power and unbalanced three-phase network. The obtained simulation models, verified by comparison with experimental results may be used in larger simulation models for testing and sizing the optimum parameters of active power filters. Models can also be used to study the interactions between grid elements and various loads or situations.

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.

Mixed Inter Second Order Cone Programming Taking Appropriate Approximation for the Unit Commitment in Hybrid AC-DC Grid

DEFF Research Database (Denmark)

Zhou, Bo; Ai, Xiaomeng; Fang, Jiakun

2017-01-01

With the rapid development and deployment of voltage source converter (VSC) based HVDC, the traditional power system is evolving to the hybrid AC-DC grid. New optimization methods are urgently needed for these hybrid AC-DC power systems. In this paper, mixed-integer second order cone programming...... (MISOCP) for the hybrid AC-DC power systems is proposed. The second order cone (SOC) relaxation is adopted to transform the AC and DC power flow constraints to MISOCP. Several IEEE test systems are used to validate the proposed MISCOP formulation of the optimal power flow (OPF) and unit commitment (UC...

KEY COMPARISONS: Final report: SIM regional comparison of ac-dc voltage transfer difference (SIM.EM.K6a, SIM.EM-K9 and SIM.EM-K11)

Science.gov (United States)

Campos, Sara; Filipski, Piotr; Izquierdo, Daniel; Afonso, Edson; Landim, Régis P.; Di Lillo, Lucas; Lipe, Thomas

2009-01-01

Three comparisons of ac-dc voltage transfer difference held from January to December 2004 are reported. Six NMIs in the SIM region took part: NRC (Canada), NIST (United States of America), CENAM (Mexico), INTI (Argentina), UTE (Uruguay) and INMETRO (Brazil). The comparisons were proposed to assess the measurement capabilities in ac-dc voltage transfer difference of the NMIs in the SIM region. The test points were selected to link the results with the equivalent CCEM Key Comparisons, through three NMIs participating in both SIM and CCEM key comparisons. Additionally, a SIM.EM-Supplementary comparison was proposed, in support of the SIM NMIs' power/energy meter calibration capabilities. One technical protocol and one travelling standard were used, to economize on time and resources. The report shows the degree of equivalence in the SIM region and also the degree of equivalence with the corresponding CCEM reference value. The results of all participants support the values and uncertainties of the applicable CMC entries for ac-dc voltage transfer difference in the Key Comparison Database held at the BIPM. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

THE MATHEMATIC STIMULATION OF TRANSIENT PROCESS IN A.C. – SYSTEM “ELECTRIC-TRACTION NETWORK – LOCOMOTIVE” 3. SWITCHING ON MAIN POWER CONVERTER IN “FREE PLAY” MODE; THE ANALYSIS OF VOLTS AND CURRENTS IN THE POWER SUPPLY INPUT SYSTEM

Directory of Open Access Journals (Sweden)

T. M. Mischenko

2011-05-01

Full Text Available The article is a continuation of analysis of the electric equivalent AC circuit «traction substation − device of transversal compensation − electric-traction network − electric locomotive DS 3» and the influence on a power transformer in the idle mode, depending on the feeder voltage and the distance of an electric locomotive from a traction substation. The numeral calculations are performed and the voltage and current values in the electric power supply system are analyzed.

Low voltage ride-through capability control for single-stage inverter-based grid-connected photovoltaic power plant

DEFF Research Database (Denmark)

Al-Shetwi, Ali Q.; Sujod, Muhamad Zahim; Blaabjerg, Frede

2018-01-01

to enhance the LVRT capability based on the Malaysian standards and modern grid codes connection requirements. The proposed control overcomes the problems of dc-link over-voltage and ac over-current that may cause disconnection or damage to the inverter. For this purpose, dc-chopper brake controller...... to improve the capability of ride-through fault safely and keep the inverter connected, but also to provide grid support through active and reactive power control at different type of faults....

Modeling and reliability analysis of three phase z-source AC-AC converter

Directory of Open Access Journals (Sweden)

Prasad Hanuman

2017-12-01

Full Text Available This paper presents the small signal modeling using the state space averaging technique and reliability analysis of a three-phase z-source ac-ac converter. By controlling the shoot-through duty ratio, it can operate in buck-boost mode and maintain desired output voltage during voltage sag and surge condition. It has faster dynamic response and higher efficiency as compared to the traditional voltage regulator. Small signal analysis derives different control transfer functions and this leads to design a suitable controller for a closed loop system during supply voltage variation. The closed loop system of the converter with a PID controller eliminates the transients in output voltage and provides steady state regulated output. The proposed model designed in the RT-LAB and executed in a field programming gate array (FPGA-based real-time digital simulator at a fixedtime step of 10 μs and a constant switching frequency of 10 kHz. The simulator was developed using very high speed integrated circuit hardware description language (VHDL, making it versatile and moveable. Hardware-in-the-loop (HIL simulation results are presented to justify the MATLAB simulation results during supply voltage variation of the three phase z-source ac-ac converter. The reliability analysis has been applied to the converter to find out the failure rate of its different components.

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.

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.

Centralized vs decentralized lunar power system study

Science.gov (United States)

Metcalf, Kenneth; Harty, Richard B.; Perronne, Gerald E.

1991-09-01

Three power-system options are considered with respect to utilization on a lunar base: the fully centralized option, the fully decentralized option, and a hybrid comprising features of the first two options. Power source, power conditioning, and power transmission are considered separately, and each architecture option is examined with ac and dc distribution, high and low voltage transmission, and buried and suspended cables. Assessments are made on the basis of mass, technological complexity, cost, reliability, and installation complexity, however, a preferred power-system architecture is not proposed. Preferred options include transmission based on ac, transmission voltages of 2000-7000 V with buried high-voltage lines and suspended low-voltage lines. Assessments of the total cost associated with the installations are required to determine the most suitable power system.

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

DEFF Research Database (Denmark)

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

2014-01-01

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

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

Design of a DC-AC Link Converter for 500W Residential Wind Generator

Directory of Open Access Journals (Sweden)

Riza Muhida

2012-12-01

Full Text Available  As one of alternative sources of renewable energy, wind energy has an excellence prospect in Indonesia, particularly in coastal and hilly areas which have potential wind to generate electricity for residential uses. There is urgent need to locally develop low cost inverter of wind generator system for residential use. Recent developments in power electronic converters and embedded computing allow improvement of power electronic converter devices that enable integration of microcontrollers in its design. In this project, an inverter circuit with suitable control scheme design was developed. The circuit was to be used with a selected topology of Wind Energy Conversion System (WECS to convert electricity generated by a 500W direct-drive permanent magnet type wind generator which is typical for residential use. From single phase AC output of the generator, a rectifier circuit is designed to convert AC to DC voltage. Then a DC-DC boost converter is used to step up the voltage to a nominal DC voltage suitable for domestic use. The proposed inverter then will convert the DC voltage to sinusoidal AC. The duty cycle of sinusoidal Pulse-Width Modulated (SPWM signal controlling switches in the inverter was generated by a microcontroller. The lab-scale experimental rig involves simulation of wind generator by running a geared DC motor coupled with 500W wind generator where the prototype circuit was connected at the generator output. The experimental circuit produced single phase 240V sinusoidal AC voltage with frequency of 50Hz. Measured total harmonics distortion (THD of the voltage across load was 4.0% which is within the limit of 5% as recommended by IEEE Standard 519-1992.

A single-phase embedded Z-source DC-AC inverter.

Science.gov (United States)

Kim, Se-Jin; Lim, Young-Cheol

2014-01-01

In the conventional DC-AC inverter consisting of two DC-DC converters with unipolar output capacitors, the output capacitor voltages of the DC-DC converters must be higher than the DC input voltage. To overcome this weakness, this paper proposes a single-phase DC-AC inverter consisting of two embedded Z-source converters with bipolar output capacitors. The proposed inverter is composed of two embedded Z-source converters with a common DC source and output AC load. Though the output capacitor voltages of the converters are relatively low compared to those of a conventional inverter, an equivalent level of AC output voltages can be obtained. Moreover, by controlling the output capacitor voltages asymmetrically, the AC output voltage of the proposed inverter can be higher than the DC input voltage. To verify the validity of the proposed inverter, experiments were performed with a DC source voltage of 38 V. By controlling the output capacitor voltages of the converters symmetrically or asymmetrically, the proposed inverter can produce sinusoidal AC output voltages. The experiments show that efficiencies of up to 95% and 97% can be achieved with the proposed inverter using symmetric and asymmetric control, respectively.

Voltage generators of high voltage high power accelerators

International Nuclear Information System (INIS)

Svinin, M.P.

1981-01-01

High voltage electron accelerators are widely used in modern radiation installations for industrial purposes. In the near future further increasing of their power may be effected, which enables to raise the efficiency of the radiation processes known and to master new power-consuming production in industry. Improvement of HV generators by increasing their power and efficiency is one of many scientific and engineering aspects the successful solution of which provides further development of these accelerators and their technical parameters. The subject is discussed in detail. (author)

DC Voltage Control and Power-Sharing of Multi-Terminal DC Grids Based on Optimal DC Power Flow and Flexible Voltage Droop Strategy

Directory of Open Access Journals (Sweden)

F. Azma

2015-06-01

Full Text Available This paper develops an effective control framework for DC voltage control and power-sharing of multi-terminal DC (MTDC grids based on an optimal power flow (OPF procedure and the voltage-droop control. In the proposed approach, an OPF algorithm is executed at the secondary level to find optimal reference of DC voltages and active powers of all voltage-regulating converters. Then, the voltage droop characteristics of voltage-regulating converters, at the primary level, are tuned based on the OPF results such that the operating point of the MTDC grid lies on the voltage droop characteristics. Consequently, the optimally-tuned voltage droop controller leads to the optimal operation of the MTDC grid. In case of variation in load or generation of the grid, a new stable operating point is achieved based on the voltage droop characteristics. By execution of a new OPF, the voltage droop characteristics are re-tuned for optimal operation of the MTDC grid after the occurrence of the load or generation variations. The results of simulation on a grid inspired by CIGRE B4 DC grid test system demonstrate efficient grid performance under the proposed control strategy.

High voltage traction power supply; Ein- und Mehrspannungssysteme in der Bahnenergieversorgung mit hohen Spannungen

Energy Technology Data Exchange (ETDEWEB)

Borchard, Ludwig O. [Transnet freight rail, (Technology Management), Braamfontein (South Africa); Lehmann, Michael [Technische Univ. Dresden (Germany). Professur Elektrische Bahnen

2009-04-15

Raising the nominal voltage of electric railway systems implies many advantages, therefore several concepts can be presented and compared. Detailed studies on two systems with high contact line voltages were performed for the upgrade of the 1 AC 50 kV railway line in South Africa. Finally requirements for high voltage locomotives are derived and illustrated by examples. (orig.)

Frequency and voltage dependent profile of dielectric properties, electric modulus and ac electrical conductivity in the PrBaCoO nanofiber capacitors

Directory of Open Access Journals (Sweden)

S. Demirezen

Full Text Available In this study, praseodymium barium cobalt oxide nanofiber interfacial layer was sandwiched between Au and n-Si. Frequency and voltage dependence of ε′, ε′, tanδ, electric modulus (M′ and M″ and σac of PrBaCoO nanofiber capacitor have been investigated by using impedance spectroscopy method. The obtained experimental results show that the values of ε′, ε′, tanδ, M′, M″ and σac of the PrBaCoO nanofiber capacitor are strongly dependent on frequency of applied bias voltage. The values of ε′, ε″ and tanδ show a steep decrease with increasing frequency for each forward bias voltage, whereas the values of σac and the electric modulus increase with increasing frequency. The high dispersion in ε′ and ε″ values at low frequencies may be attributed to the Maxwell–Wagner and space charge polarization. The high values of ε′ may be due to the interfacial effects within the material, PrBaCoO nanofibers interfacial layer and electron effect. The values of M′ and M″ reach a maximum constant value corresponding to M∞ ≈ 1/ε∞ due to the relaxation process at high frequencies, but both the values of M′ and M″ approach almost to zero at low frequencies. The changes in the dielectric and electrical properties with frequency can be also attributed to the existence of Nss and Rs of the capacitors. As a result, the change in the ε′, ε″, tanδ, M′, M″ and ac electric conductivity (σac is a result of restructuring and reordering of charges at the PrBaCoO/n-Si interface under an external electric field or voltage and interface polarization. Keywords: Thin films, Electrical properties, Interface/interphase

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

DEFF Research Database (Denmark)

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

2015-01-01

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

Direct AC–AC grid interface converter for ocean wave energy system

International Nuclear Information System (INIS)

Tsang, K.M.; Chan, W.L.

2015-01-01

Highlights: • Novel power grid interface converter for ocean wave energy system. • Unlike conventional approach, generator output is directly converted into fixed frequency AC for synchronous connection. • High conversion efficient and power quality could be achieved. - Abstract: Ocean wave energy is very promising. However, existing systems are using rectifying circuits to convert variable voltage and variable frequency output of electric generator into DC voltage and then use grid-tied inverter to connect to the power grid. Such arrangement will not only reduce the overall efficient but also increase the cost of the system. A direct AC–AC converter is a desirable solution. In this paper, a six-switch AC–AC converter has been proposed as a single phase grid-connected interface. New switching scheme has been derived for the converter such that the virtual input AC–DC conversion and the output DC–AC conversion can be decoupled. State-space averaging model and pulse width modulation scheme have been derived for the converter. As the input and the output operations can be decoupled, two independent controllers have been designed to handle the input AC–DC regulation and the output DC–AC regulation. The proposed scheme demands for two separate duty ratios and novel switching scheme has been derived to realize the combined duty ratios in one switching cycle. Power regulation, harmonics elimination and power factor correction control algorithms have also been derived for the converter when it is connected to the supply grid. Experimental results of a small scale model are included to demonstrate the effectiveness of the proposed switching and control schemes

Three-Phase and Six-Phase AC at the Lab Bench

Science.gov (United States)

Caplan, George M.

2009-01-01

Utility companies generate three-phase electric power, which consists of three sinusoidal voltages with phase angles of 0 degrees, 120 degrees, and 240 degrees. The ac generators described in most introductory textbooks are single-phase generators, so physics students are not likely to learn about three-phase power. I have developed a simple way…

Application of Newton's optimal power flow in voltage/reactive power control

Energy Technology Data Exchange (ETDEWEB)

Bjelogrlic, M.; Babic, B.S. (Electric Power Board of Serbia, Belgrade (YU)); Calovic, M.S. (Dept. of Electrical Engineering, University of Belgrade, Belgrade (YU)); Ristanovic, P. (Institute Nikola Tesla, Belgrade (YU))

1990-11-01

This paper considers an application of Newton's optimal power flow to the solution of the secondary voltage/reactive power control in transmission networks. An efficient computer program based on the latest achievements in the sparse matrix/vector techniques has been developed for this purpose. It is characterized by good robustness, accuracy and speed. A combined objective function appropriate for various system load levels with suitable constraints, for treatment of the power system security and economy is also proposed. For the real-time voltage/reactive power control, a suboptimal power flow procedure has been derived by using the reduced set of control variables. This procedure is based on the sensitivity theory applied to the determination of zones for the secondary voltage/reactive power control and corresponding reduced set of regulating sources, whose reactive outputs represent control variables in the optimal power flow program. As a result, the optimal power flow program output becomes a schedule to be used by operators in the process of the real-time voltage/reactive power control in both normal and emergency operating states.

Cable Insulation Breakdowns in the Modulator with a Switch Mode High Voltage Power Supply

CERN Document Server

Cours, A

2004-01-01

The Advanced Photon Source modulators are PFN-type pulsers with 40 kV switch mode charging power supplies (PSs). The PS and the PFN are connected to each other by 18 feet of high-voltage (HV) cable. Another HV cable connects two separate parts of the PFN. The cables are standard 75 kV x-ray cables. All four cable connectors were designed by the PS manufacturer. Both cables were operating at the same voltage level (about 35 kV). The PS’s output connector has never failed during five years of operation. One of the other three connectors failed approximately five times more often than the others. In order to resolve the failure problem, a transient analysis was performed for all connectors. It was found that transient voltage in the connector that failed most often was subjected to more high-frequency, high-amplitude AC components than the other three connectors. It was thought that these components caused partial discharge in the connector insulation and led to the insulation breakdown. Modification o...

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...

Investigation of Hybrid Pseudo Bipolar HVDC Performances Supply Power to Passive AC Network

Directory of Open Access Journals (Sweden)

Kuan Li

2014-07-01

Full Text Available The traditional HVDC plays an important role in the development of power grid. But the traditional HVDC cannot supply power either to entirely passive AC network or to weak AC system. In fact, an entirely passive AC network can be effectively powered through VSC-HVDC. However, the cost of investment in VSC-HVDC is amazingly high due to the limitation of power electronics technology. Based on CSC and VSC, this paper proposes a method to build Hybrid HVDC, which makes the power supply to the passive AC network come true and, at the same time, lowers the investment cost. The effect of topology, steady mathematical model, startup characteristic, steady and transient characteristics in Hybrid HVDC system are systematically studied in this paper. The simulation result shows that Hybrid HVDC can supply power to the passive AC network with high stability. This study provides a theoretical basis for the further development of HVDC.

Reduction technique of drop voltage and power losses to improve power quality using ETAP Power Station simulation model

Science.gov (United States)

Satrio, Reza Indra; Subiyanto

2018-03-01

The effect of electric loads growth emerged direct impact in power systems distribution. Drop voltage and power losses one of the important things in power systems distribution. This paper presents modelling approach used to restructrure electrical network configuration, reduce drop voltage, reduce power losses and add new distribution transformer to enhance reliability of power systems distribution. Restructrure electrical network was aimed to analyse and investigate electric loads of a distribution transformer. Measurement of real voltage and real current were finished two times for each consumer, that were morning period and night period or when peak load. Design and simulation were conduct by using ETAP Power Station Software. Based on result of simulation and real measurement precentage of drop voltage and total power losses were mismatch with SPLN (Standard PLN) 72:1987. After added a new distribution transformer and restructrured electricity network configuration, the result of simulation could reduce drop voltage from 1.3 % - 31.3 % to 8.1 % - 9.6 % and power losses from 646.7 watt to 233.29 watt. Result showed, restructrure electricity network configuration and added new distribution transformer can be applied as an effective method to reduce drop voltage and reduce power losses.

Voltage-current characteristics of multiterminal HVDC-VSC for offshore wind farms

Energy Technology Data Exchange (ETDEWEB)

Gomis-Bellmunt, Oriol [Centre d' Innovacio Tecnologica en Convertidors Estatics i Accionaments (CITCEA-UPC), Universitat Politecnica de Catalunya UPC, Av. Diagonal, 647, Pl. 2., 08028 Barcelona (Spain); IREC Catalonia Institute for Energy Research, Barcelona (Spain); Liang, Jun; Ekanayake, Janaka; Jenkins, Nicholas [School of Engineering, Cardiff University, Queen' s Buildings, The Parade, Cardiff CF24 3AA, Wales (United Kingdom)

2011-02-15

Voltage-current characteristics and equilibrium points for the DC voltages of multiterminal HVDC systems using voltage source converters are discussed. The wind farm rectifiers and grid connected inverters are analyzed through their operating modes, governing equations and graphical characteristics. Using the converter equations and the HVDC grid conductance matrix the equilibrium voltages and currents are found. Case studies are presented considering wind power generation, loss of a converter and voltage sags in the AC grid. (author)

Reactive power management and voltage control in deregulated power markets

Science.gov (United States)

Spangler, Robert G.

The research that is the subject of this dissertation is about the management of reactive power and voltage support in the wholesale open access power markets in the United States (US). The purpose of this research is to place decisions about open access market structures, as they relate to reactive power and voltage control, on a logical and consistent economic basis, given the engineering needs of a commercial electric power system. An examination of the electricity markets operating in the US today reveals that current approaches to reactive power management and voltage support are extensions of those based on historical, regulated monopoly electric service. A case for change is built by first looking at the subject of reactive power from an engineering viewpoint and then from an economic perspective. Ultimately, a set of market rules for managing reactive power and voltage support is proposed. The proposal suggests that cost recovery for static and dynamic VARs is appropriately accomplished through the regulated transmission cost of service. Static VAR cost recovery should follow traditional rate recovery methodologies. In the case of dynamic VARs, this work provides a methodology based on the microeconomic theory of the firm for determining such cost. It further suggests that an operational strategy that reduces and limits the use of dynamic VARs, during normal operations, is appropriate. This latter point leads to an increase in the fixed cost of the transmission network but prevents price spikes and short supply situations from affecting, or being affected by, the reactive capability limitations associated with dynamic VARs supplied from synchronous generators. The rules are consistent with a market structure that includes competitive generation and their application will result in the communication of a clear understanding of the responsibilities, related to voltage control, of each type of market entity. In this sense, their application will contribute to

A Three-Level Quasi-Two-Stage Single-Phase PFC Converter with Flexible Output Voltage and Improved Conversion Efficiency

DEFF Research Database (Denmark)

Tang, Yi; Zhu, Dexuan; Jin, Chi

2015-01-01

voltages, and it will be very suitable for high-power applications where the output voltage can be either lower or higher than the peak ac input voltage, e.g., plug-in hybrid electric vehicle charging systems. Moreover, the involved dc/dc buck conversion stage may only need to process partial input power...

Dynamic Reactive Power Control in Offshore HVDC Connected Wind Power Plants

DEFF Research Database (Denmark)

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

2016-01-01

This paper presents a coordinated reactive power control for a HVDC connected cluster of offshore wind power plants (WPPs). The reactive power reference for the WPP cluster is estimated by an optimization algorithm aiming at minimum active power losses in the offshore AC Grid. For each optimal......, such as wind turbine (WT) terminal, collector cable, and export cable, on the dynamic voltage profile of the offshore grid is investigated. Furthermore, the dynamic reactive power contribution from WTs from different WPPs of the cluster for such faults has also been studied....... reactive power set point, the OWPP cluster controller generates reactive power references for each WPP which further sends the AC voltage/ reactive power references to the associated WTs based on their available reactive power margin. The impact of faults at different locations in the offshore grid...

Fuzzy Controller for a Voltage-Regulated Solar-Powered MPPT System for Hybrid Power System Applications

Directory of Open Access Journals (Sweden)

Jaw-Kuen Shiau

2015-04-01

Full Text Available This paper presents the design of a fuzzy-logic-based voltage-regulated solar power maximum power point tracking (MPPT system for applications involving hybrid power systems. The system contains a solar power system and battery as the primary and secondary power sources, respectively. The solar system alone supplies power to the electric motor and maintains the output voltage at a predetermined level when it has sufficient power. When the solar power is insufficient, the solar system is operated at its maximum power point (MPP and the battery is engaged to compensate for the insufficiency. First, a variant of the incremental conductance MPP condition was established. Under the MPP condition, the voltage-regulated MPPT system was formulated as a feedback control system, where the MPP condition and voltage regulation requirements were used as the system inputs. Next, a fuzzy controller was developed to perform the voltage-regulated MPPT function for the hybrid power system. A simulation model based on Matrix laboratory (MATLAB/SIMULINK (a block diagram environment for multi-domain simulation and model-based design and a piecewise linear electric circuit simulation (PLECS tool for controlling the dc motor velocity was developed to verify the voltage-regulated solar power MPPT system.

High Voltage Hybrid Electric Propulsion - Multilayered Functional Insulation System (MFIS) NASA-GRC

Science.gov (United States)

Lizcano, M.

2017-01-01

High power transmission cables pose a key challenge in future Hybrid Electric Propulsion Aircraft. The challenge arises in developing safe transmission lines that can withstand the unique environment found in aircraft while providing megawatts of power. High voltage AC, variable frequency cables do not currently exist and present particular electrical insulation challenges since electrical arcing and high heating are more prevalent at higher voltages and frequencies. Identifying and developing materials that maintain their dielectric properties at high voltage and frequencies is crucial.

Advanced High Voltage Power Device Concepts

CERN Document Server

Baliga, B Jayant

2012-01-01

Advanced High Voltage Power Device Concepts describes devices utilized in power transmission and distribution equipment, and for very high power motor control in electric trains and steel-mills. Since these devices must be capable of supporting more than 5000-volts in the blocking mode, this books covers operation of devices rated at 5,000-V, 10,000-V and 20,000-V. Advanced concepts (the MCT, the BRT, and the EST) that enable MOS-gated control of power thyristor structures are described and analyzed in detail. In addition, detailed analyses of the silicon IGBT, as well as the silicon carbide MOSFET and IGBT, are provided for comparison purposes. Throughout the book, analytical models are generated to give a better understanding of the physics of operation for all the structures. This book provides readers with: The first comprehensive treatment of high voltage (over 5000-volts) power devices suitable for the power distribution, traction, and motor-control markets;  Analytical formulations for all the device ...

Dual voltage power supply with 48 volt

Energy Technology Data Exchange (ETDEWEB)

Froeschl, Joachim; Proebstle, Hartmut; Sirch, Ottmar [BMW Group, Muenchen (Germany)

2012-11-01

Automotive electrics/electronics have just reached a period of tremendous change. High voltage systems for Hybrid, Plug-In Hybrid or Battery Electric Vehicles with high power electric motors, high energy accumulators and electric climate compressors will be introduced in order to achieve the challenging targets for CO{sub 2} emissions and energy efficiency and to anticipate the mobility of the future. Additionally, innovations and the continuous increase of functionality for comfort, safety, driver assistance and infotainment systems require more and more electrical power of the vehicle power supply at all. On the one hand side electrified vehicles will certainly achieve a significant market share, on the other hand side they will increase the pressure to conventional vehicles with combustion engines for fuel consumption and CO{sub 2} emissions. These vehicles will be enabled to keep their competitiveness by new functions and the optimization of their electric systems. A dual voltage power supply with 48 Volt and 12 Volt will be one of the key technologies to realize these requirements. The power capability of the existing 12 Volt power supply has reached its limits. Further potentials can only be admitted by the introduction of 48 Volt. For this reason the car manufacturers Audi, BMW, Daimler, Porsche and Volkswagen started very early on this item and developed a common specification of the new voltage range. Now, it is necessary to identify the probable systems at this voltage range and to start the developments. (orig.)

Current-voltage characteristics of a superconducting slab under a superimposed small AC magnetic field

International Nuclear Information System (INIS)

Matsushita, Teruo; Yamafuji, Kaoru; Sakamoto, Nobuyoshi.

1977-01-01

In case of applying superconductors to electric machinery or high intensity field magnets for fusion reactors, the superconductors are generally expected to be sensible to small field fluctuation besides DC magnetic field. The behavior of superconductors in DC magnetic field superimposed with small AC magnetic field has been investigated often experimentally, and the result has been obtained that the critical current at which DC flow voltage begins to appear extremely decreased or disappeared. Some theoretical investigations have been carried out on this phenomenon so far, however, their application has been limited to the region where frequency is sufficiently low or which is close to the critical magnetic field. Purpose of this report is to deal with the phenomenon in more unified way by analyzing the behavior of magnetic flux lines in a superconductor under a superimposed small AC field using the criticalstate model including viscous force. In order to solve the fundamental equation in this report, first the solution has been obtained in the quasi-static state neglecting viscous force, then about the cases that current density J is not more than Jc and J is larger than Jc, concerning the deviation from the quasi-static limit by employing successive approximation. Current-voltage characteristics have been determined by utilizing the above results. This method seems to be most promising at present except the case of extremely high frequency. (Wakatsuki, Y.)

Research & Implementation of AC - DC Converter with High Power Factor & High Efficiency

Directory of Open Access Journals (Sweden)

Hsiou-Hsian Nien

2014-05-01

Full Text Available In this paper, we design and develop a high power factor, high efficiency two-stage AC - DC power converter. This paper proposes a two-stage AC - DC power converter. The first stage is boost active power factor correction circuit. The latter stage is near constant frequency LLC resonant converter. In addition to traditional LLC high efficiency advantages, light-load conversion efficiency of this power converter can be improved. And it possesses high power factor and near constant frequency operating characteristics, can significantly reduce the electromagnetic interference. This paper first discusses the main structure and control manner of power factor correction circuit. And then by the LLC resonant converter equivalent model proceed to circuit analysis to determine the important parameters of the converter circuit elements. Then design a variable frequency resonant tank. The resonant frequency can change automatically on the basis of the load to reach near constant frequency operation and a purpose of high efficiency. Finally, actually design and produce an AC – DC power converter with output of 190W to verify the characteristics and feasibility of this converter. The experimental results show that in a very light load (9.5 W the efficiency is as high as 81%, the highest efficiency of 88% (90 W. Full load efficiency is 87%. At 19 W ~ 190 W power changes, the operating frequency change is only 0.4 kHz (AC 110 V and 0.3 kHz (AC 220 V.

Modelling a single phase voltage controlled rectifier using Laplace transforms

Science.gov (United States)

Kraft, L. Alan; Kankam, M. David

1992-01-01

The development of a 20 kHz, AC power system by NASA for large space projects has spurred a need to develop models for the equipment which will be used on these single phase systems. To date, models for the AC source (i.e., inverters) have been developed. It is the intent of this paper to develop a method to model the single phase voltage controlled rectifiers which will be attached to the AC power grid as an interface for connected loads. A modified version of EPRI's HARMFLO program is used as the shell for these models. The results obtained from the model developed in this paper are quite adequate for the analysis of problems such as voltage resonance. The unique technique presented in this paper uses the Laplace transforms to determine the harmonic content of the load current of the rectifier rather than a curve fitting technique. Laplace transforms yield the coefficient of the differential equations which model the line current to the rectifier directly.

High Input Voltage, Silicon Carbide Power Processing Unit Performance Demonstration

Science.gov (United States)

Bozak, Karin E.; Pinero, Luis R.; Scheidegger, Robert J.; Aulisio, Michael V.; Gonzalez, Marcelo C.; Birchenough, Arthur G.

2015-01-01

A silicon carbide brassboard power processing unit has been developed by the NASA Glenn Research Center in Cleveland, Ohio. The power processing unit operates from two sources: a nominal 300 Volt high voltage input bus and a nominal 28 Volt low voltage input bus. The design of the power processing unit includes four low voltage, low power auxiliary supplies, and two parallel 7.5 kilowatt (kW) discharge power supplies that are capable of providing up to 15 kilowatts of total power at 300 to 500 Volts (V) to the thruster. Additionally, the unit contains a housekeeping supply, high voltage input filter, low voltage input filter, and master control board, such that the complete brassboard unit is capable of operating a 12.5 kilowatt Hall effect thruster. The performance of the unit was characterized under both ambient and thermal vacuum test conditions, and the results demonstrate exceptional performance with full power efficiencies exceeding 97%. The unit was also tested with a 12.5kW Hall effect thruster to verify compatibility and output filter specifications. With space-qualified silicon carbide or similar high voltage, high efficiency power devices, this would provide a design solution to address the need for high power electric propulsion systems.

Lower-Order Compensation Chain Threshold-Reduction Technique for Multi-Stage Voltage Multipliers.

Science.gov (United States)

Dell' Anna, Francesco; Dong, Tao; Li, Ping; Wen, Yumei; Azadmehr, Mehdi; Casu, Mario; Berg, Yngvar

2018-04-17

This paper presents a novel threshold-compensation technique for multi-stage voltage multipliers employed in low power applications such as passive and autonomous wireless sensing nodes (WSNs) powered by energy harvesters. The proposed threshold-reduction technique enables a topological design methodology which, through an optimum control of the trade-off among transistor conductivity and leakage losses, is aimed at maximizing the voltage conversion efficiency (VCE) for a given ac input signal and physical chip area occupation. The conducted simulations positively assert the validity of the proposed design methodology, emphasizing the exploitable design space yielded by the transistor connection scheme in the voltage multiplier chain. An experimental validation and comparison of threshold-compensation techniques was performed, adopting 2N5247 N-channel junction field effect transistors (JFETs) for the realization of the voltage multiplier prototypes. The attained measurements clearly support the effectiveness of the proposed threshold-reduction approach, which can significantly reduce the chip area occupation for a given target output performance and ac input signal.

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.

Experimental Investigation of the Corona Discharge in Electrical Transmission due to AC/DC Electric Fields

Directory of Open Access Journals (Sweden)

Fuangpian Phanupong

2016-01-01

Full Text Available Nowadays, using of High Voltage Direct Current (HVDC transmission to maximize the transmission efficiency, bulk power transmission, connection of renewable power source from wind farm to the grid is of prime concern for the utility. However, due to the high electric field stress from Direct Current (DC line, the corona discharge can easily be occurred at the conductor surface leading to transmission loss. Therefore, the polarity effect of DC lines on corona inception and breakdown voltage should be investigated. In this work, the effect of DC polarity and Alternating Current (AC field stress on corona inception voltage and corona discharge is investigated on various test objects, such as High Voltage (HV needle, needle at ground plane, internal defect, surface discharge, underground cable without cable termination, cable termination with simulated defect and bare overhead conductor. The corona discharge is measured by partial discharge measurement device with high-frequency current transformer. Finally, the relationship between supply voltage and discharge intensity on each DC polarity and AC field stress can be successfully determined.

Voltage harmonics mitigation through hybrid active power filer

International Nuclear Information System (INIS)

Sahito, A.A.; Tunio, S.M.; Khizer, A.N.

2016-01-01

Fast dynamic response, high efficiency, low cost and small size of power electronic converters have exponentially increased their use in modern power system which resulted in harmonically distorted voltage and currents. Voltage harmonics mainly caused by current harmonics are more dangerous as performance and expected operating life of other power system equipment are affected by harmonically distorted supply voltage. Electronic filter circuits are used to improve system power quality by mitigating adverse effects of harmonics. Hybrid filters having advantages of both passive and active filters are preferred to resolve the problem of harmonics efficiently and avoiding any chance of resonance. In this paper, a three phase three wire network is considered to supply an adjustable speed drive represented by a resistive load connected across a three phase bridge rectifier. Simulation of the considered system shows THD (Total Harmonic Distortion) of 18.91 and 7.61 percentage in supply current and voltage respectively. A HAPF (Hybrid Active Power Filter) is proposed to reduce these THD values below 5 percentage as recommended by IEEE Standard-519. P-Q theorem is used to calculate required parameters for proposed filter, which is implemented through hysteresis control. Simulation results confirm the effectiveness of the designed filter as THD for both current and voltage have reduced below allowable limit of 5 percentage. (author)

Voltage Harmonics Mitigation through Hybrid Active Power Filter

Directory of Open Access Journals (Sweden)

Anwer Ali Sahito

2016-01-01

Full Text Available Fast dynamic response, high efficiency, low cost and small size of power electronic converters have exponentially increased their use in modern power system which resulted in harmonically distorted voltage and currents. Voltage harmonics mainly caused by current harmonics are more dangerous as performance and expected operating life of other power system equipment are affected by harmonically distorted supply voltage. Electronic filter circuits are used to improve system power quality by mitigating adverse effects of harmonics. Hybrid filters having advantages of both passive and active filters are preferred to resolve the problem of harmonics efficiently and avoiding any chance of resonance. In this paper, a three phase three wire network is considered to supply an adjustable speed drive represented by a resistive load connected across a three phase bridge rectifier. Simulation of the considered system shows THD (Total Harmonic Distortion of 18.91 and 7.61% in supply current and voltage respectively. A HAPF (Hybrid Active Power Filter is proposed to reduce these THD values below 5% as recommended by IEEE Standard-519. P-Q theorem is used to calculate required parameters for proposed filter, which is implemented through hysteresis control. Simulation results confirm the effectiveness of the designed filter as THD for both current and voltage have reduced below allowable limit of 5%.

ac power control in the Core Flow Test Loop

International Nuclear Information System (INIS)

McDonald, D.W.

1980-01-01

This work represents a status report on a development effort to design an ac power controller for the Core Flow Test Loop. The Core Flow Test Loop will be an engineering test facility which will simulate the thermal environment of a gas-cooled fast-breeder reactor. The problems and limitations of using sinusoidal ac power to simulate the power generated within a nuclear reactor are addressed. The transformer-thyristor configuration chosen for the Core Flow Test Loop power supply is presented. The initial considerations, design, and analysis of a closed-loop controller prototype are detailed. The design is then analyzed for improved performance possibilities and failure modes are investigated at length. A summary of the work completed to date and a proposed outline for continued development completes the report

New trends in the development of high voltage technology

Energy Technology Data Exchange (ETDEWEB)

Aleksandrov, G N

1964-07-01

The question is raised as to what type of transmission should be developed to transfer power over long distances from the eastern to the western part of Russia, and what principles should be utilized to combine power transmission into single power system in the USSR. Aleksandrov indicates the need for higher voltage power transmission, and stresses that ac is more economical than dc. The author compares +-750 kV dc with 1000 kV ac. The economic comparison is conducted for the same level of insulation, and it is stated that it will result in the same amount of power transmitted. New insulation materials are mentioned, and wider use of fiberglass and other plastics is predicted.

On-chip high-voltage generator design design methodology for charge pumps

CERN Document Server

Tanzawa, Toru

2016-01-01

This book provides various design techniques for switched-capacitor on-chip high-voltage generators, including charge pump circuits, regulators, level shifters, references, and oscillators.  Readers will see these techniques applied to system design in order to address the challenge of how the on-chip high-voltage generator is designed for Flash memories, LCD drivers, and other semiconductor devices to optimize the entire circuit area and power efficiency with a low voltage supply, while minimizing the cost.  This new edition includes a variety of useful updates, including coverage of power efficiency and comprehensive optimization methodologies for DC-DC voltage multipliers, modeling of extremely low voltage Dickson charge pumps, and modeling and optimum design of AC-DC switched-capacitor multipliers for energy harvesting and power transfer for RFID.

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 control on TEG-inverter system with pulse width modulation

International Nuclear Information System (INIS)

Kimura, N.; Kinoshita, H.; Matsuura, K.

1984-01-01

An ocean thermoelectric generating system can be expected to supply cheap electric power in future. And it can be used as base power supply or isolated power source in developing areas. The authors propose to apply forced-commutation inverter to thermoelectric energy conversion system and construct an electric power station which can be operated without any other synchronous generator (S-G) and can control ac system as stable as S-G. This paper shows that inverters can control voltage constant, though within a range of 10% load change, by using pulse width modulation (PWM). It also describes the design of the voltage control system covering from 50% to 100% load with combination of PWM and output voltage tap changing of TEG

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

DEFF Research Database (Denmark)

Liu, Yan; Wang, Xiongfei; Chen, Zhe

2012-01-01

The Low-Voltage Ride-Through (LVRT) has become an important grid requirement for offshore wind farms connecting with Voltage Source Converter based High Voltage Direct Current (VSC-HVDC) links. In this paper, a cooperative control strategy with LVRT ability is proposed for a VSC-HVDC connected...... variable speed Squirrel-Cage Induction Generator (SCIG) wind farm. The approach employs a DC-link voltage versus offshore AC-bus frequency droop control on the offshore converter of VSC-HVDC link. Thus, the back-to-back converters of SCIG wind turbines can adjust the generated active power based on the AC......-bus frequency deviations, so that a fast power reduction on the wind farm side can be achieved. The EMTDC/PSCAD simulations are performed on a 300 MW offshore variable speed SCIG wind farm. Simulation results confirm the effectiveness of the proposed control method....

Barriers and solutions for AC low voltage fault ride-through on multi-terminal HVDC grids

Energy Technology Data Exchange (ETDEWEB)

Silva, B.; Moreira, C.L.; Leite, H.; Pecas Lopes, J.A. [Porto Univ. (Portugal). Dept. de Engenharia Electrotecnica e de Computadores (DEEC); Tecnologia e Ciencia, Porto (Portugal). Inst. de Engenharia de Sistemas e Computadores (INESCTEC)

2012-07-01

This work analyzes the multi-terminal DC grids dynamics under AC mainland grid fault events envisioning to assess the feasibility of fault ride-through provision. The major bottleneck related with the operation under AC fault consists on the DC side power imbalance that takes place due to the HVDC converter current limits and consequent incapability of delivering all the generated power to the grid. It was also verified that the power imbalance leads to a DC overvoltage occurrence. The mechanism of including chopper devices at the onshore converters DC terminals has been studied as a mean of power equilibrium promotion. Simulations comparing the both cases were performed and the comparison and the effectiveness of the adopted approach are also presented. (orig.)

Capacitor Voltages Measurement and Balancing in Flying Capacitor Multilevel Converters Utilizing a Single Voltage Sensor

DEFF Research Database (Denmark)

Farivar, Glen; Ghias, Amer M. Y. M.; Hredzak, Branislav

2017-01-01

This paper proposes a new method for measuring capacitor voltages in multilevel flying capacitor (FC) converters that requires only one voltage sensor per phase leg. Multiple dc voltage sensors traditionally used to measure the capacitor voltages are replaced with a single voltage sensor at the ac...... side of the phase leg. The proposed method is subsequently used to balance the capacitor voltages using only the measured ac voltage. The operation of the proposed measurement and balancing method is independent of the number of the converter levels. Experimental results presented for a five-level FC...

Programmable Power Supply for AC Switching Magnet of Proton Accelerator

CERN Document Server

Jeong, Seong-Hun; Kang Heung Sik; Lee, Chi-Hwan; Lee, Hong-Gi; Park, Ki-Hyeon; Ryu, Chun-Kil; Sik Han, Hong; Suck Suh, Hyung

2005-01-01

The 100-MeV PEFP proton linac has two proton beam extraction lines for user' experiment. Each extraction line has 5 beamlines and has 5 Hz operating frequency. An AC switching magnet is used to distribute the proton beam to the 5 beamlines, An AC switching magnet is powered by PWM-controlled bipolar switching-mode converters. This converter is designed to operate at ±350A, 5 Hz programmable step output. The power supply is employed IGBT module and has controlled by a DSP (Digital Signal Process). This paper describes the design and test results of the power supply.

The pulse-driven AC Josephson voltage normal

International Nuclear Information System (INIS)

Kieler, Oliver

2016-01-01

In this contribution quantum precise alternating-voltage sources are presented, which make the generation of arbitrary wave forms with highest spectral purity with a high bandwidth from DC up to the MHz range possible. Heartpiece of these Josephson voltage normals is a serial circuit of many thousand Josephson contacts, which make by irradiation with high-frequency radiation (microwaves) the generation of highly precise voltage values possible. Thereby in the current-voltage characteristics stages of constant voltage, so called Shapiro stages, occur. Illustratively these stages can be described by the transfer of a certain number of flux quanta through the Josephson contacts.

Modelling and Simulation of Single-Phase Series Active Compensator for Power Quality Improvement

Science.gov (United States)

Verma, Arun Kumar; Mathuria, Kirti; Singh, Bhim; Bhuvaneshwari, G.

2017-10-01

A single-phase active series compensator is proposed in this work to reduce harmonic currents at the ac mains and to regulate the dc link voltage of a diode bridge rectifier (DBR) that acts as the front end converter for a voltage source inverter feeding an ac motor. This ac motor drive is used in any of the domestic, commercial or industrial appliances. Under fluctuating ac mains voltages, the dc link voltage of the DBR depicts wide variations and hence the ac motor is used at reduced rating as compared to its name-plate rating. The active series compensator proposed here provides dual functions of improving the power quality at the ac mains and regulating the dc link voltage thus averting the need for derating of the ac motor.

Modelling and Control Design of a Dual Buck-Boost AC/DC Converter Used in the DC Nano-Grid

DEFF Research Database (Denmark)

Wu, Weimin; Liu, Yuan; Wang, Houqing

2016-01-01

Due to widely used DC characterized loads and more distributed power generation sources, the DC Nano-grid becomes more and more popular and seen as an alternative to the AC-grid in future. For the safety considerations, the DC Nano-grid should provide reliable grounding for the residential loads...... like the low voltage AC power system. In this paper, a dual Buck-Boost AC/DC converter for use in the united grounding configuration based DC Nano-grid with three terminal outputs is proposed. It will be much easy to construct an efficient DC Nano-grid based on the existing low AC power system by using...

The pulse-driven AC Josephson voltage normal; Das pulsgetriebene AC-Josephson-Spannungsnormal

Energy Technology Data Exchange (ETDEWEB)

Kieler, Oliver [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany). Arbeitsgruppe 2.43 ' ' Josephson-Schaltungen' '

2016-09-15

In this contribution quantum precise alternating-voltage sources are presented, which make the generation of arbitrary wave forms with highest spectral purity with a high bandwidth from DC up to the MHz range possible. Heartpiece of these Josephson voltage normals is a serial circuit of many thousand Josephson contacts, which make by irradiation with high-frequency radiation (microwaves) the generation of highly precise voltage values possible. Thereby in the current-voltage characteristics stages of constant voltage, so called Shapiro stages, occur. Illustratively these stages can be described by the transfer of a certain number of flux quanta through the Josephson contacts.

Modular High Voltage Power Supply

Energy Technology Data Exchange (ETDEWEB)

Newell, Matthew R. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-05-18

The goal of this project is to develop a modular high voltage power supply that will meet the needs of safeguards applications and provide a modular plug and play supply for use with standard electronic racks.

Voltage Stabilizer Based on SPWM technique Using Microcontroller

OpenAIRE

K. N. Tarchanidis; J. N. Lygouras; P. Botsaris

2013-01-01

This paper presents an application of the well known SPWM technique on a voltage stabilizer, using a microcontroller. The stabilizer is AC/DC/AC type. So, the system rectifies the input AC voltage to a suitable DC level and the intelligent control of an embedded microcontroller regulates the pulse width of the output voltage in order to produce through a filter a perfect sinusoidal AC voltage. The control program on the microcontroller has the ability to change the FET transistor ...

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.

Reducing AC-Winding Losses in High-Current High-Power Inductors

DEFF Research Database (Denmark)

Nymand, Morten; Madawala, Udaya K.; Andersen, Michael Andreas E.

2009-01-01

Foil windings are preferable in high-current high-power inductors to realize compact designs and to reduce dc-current losses. At high frequency, however, proximity effect will cause very significant increase in ac resistance in multi-layer windings, and lead to high ac winding losses. This paper ...

Parallel operation of voltage-source converters: issues and applications

Energy Technology Data Exchange (ETDEWEB)

Almeida, F.C.B.; Silva, D.S. [Federal University of Juiz de Fora (UFJF), MG (Brazil)], Emails: felipe.brum@engenharia.ufjf.br, salomaoime@yahoo.com.br; Ribeiro, P.F. [Calvin College, Grand Rapids, MI (United States); Federal University of Juiz de Fora (UFJF), MG (Brazil)], E-mail: pfribeiro@ieee.org

2009-07-01

Technological advancements in power electronics have prompted the development of advanced AC/DC conversion systems with high efficiency and flexible performance. Among these devices, the Voltage-Source Converter (VSC) has become an essential building block. This paper considers the parallel operation of VSCs under different system conditions and how they can assist the operation of highly complex power networks. A multi-terminal VSC-based High Voltage Direct Current (M-VSC-HVDC) system is chosen to be modeled, simulated and then analyzed as an example of VSCs operating in parallel. (author)

New three-phase ac-ac converter incorporating three-phase boost integrated ZVT bridge and single-phase HF link

International Nuclear Information System (INIS)

Abdelhamid, Tamer H.; Sabzali, Ahmad J.

2008-01-01

This paper presents a new zero voltage transition (ZVT), power factor corrected three phase ac-ac converter with single phase high frequency (HF) link. It is a two stage converter; the first stage is a boost integrated bridge converter (combination of a 3 ph boost converter and a bridge converter) operated at fixed frequency and that operates in two modes at ZVT for all switches and establishes a 1 ph square wave HF link. The second stage is a bi-directional pulse width modulation (PWM) 3 ph bridge that converts the 1 ph HF link to a 3 ph voltage using a novel switching strategy. The converter modes of operation and key equations are outlined. Simulation of the overall system is conducted using Simulink. The switching strategy and its corresponding control circuit are clearly described. Experimental verification of the simulation is conducted for a prototype of 100 V, 500 W at 10 kHz link frequency

Study of the Dependency on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter

Science.gov (United States)

Gottardi, L.; Bruijn, M.; denHartog, R.; Hoevers, H.; deKorte, P.; vanderKuur, J.; Linderman, M.; Adams, J.; Bailey, C.; Bandler, S.;

High-power converters and AC drives

CERN Document Server

Wu, Bin

2017-01-01

This new edition reflects the recent technological advancements in the MV drive industry, such as advanced multilevel converters and drive configurations. It includes three new chapters, Control of Synchronous Motor Drives, Transformerless MV Drives, and Matrix Converter Fed Drives. In addition, there are extensively revised chapters on Multilevel Voltage Source Inverters and Voltage Source Inverter-Fed Drives. This book includes a systematic analysis on a variety of high-power multilevel converters, illustrates important concepts with simulations and experiments, introduces various megawatt drives produced by world leading drive manufacturers, and addresses practical problems and their mitigations methods.

A cascaded three-phase symmetrical multistage voltage multiplier

International Nuclear Information System (INIS)

Iqbal, Shahid; Singh, G K; Besar, R; Muhammad, G

2006-01-01

A cascaded three-phase symmetrical multistage Cockcroft-Walton voltage multiplier (CW-VM) is proposed in this report. It consists of three single-phase symmetrical voltage multipliers, which are connected in series at their smoothing columns like string of batteries and are driven by three-phase ac power source. The smoothing column of each voltage multiplier is charged twice every cycle independently by respective oscillating columns and discharged in series through load. The charging discharging process completes six times a cycle and therefore the output voltage ripple's frequency is of sixth order of the drive signal frequency. Thus the proposed approach eliminates the first five harmonic components of load generated voltage ripples and sixth harmonic is the major ripple component. The proposed cascaded three-phase symmetrical voltage multiplier has less than half the voltage ripple, and three times larger output voltage and output power than the conventional single-phase symmetrical CW-VM. Experimental and simulation results of the laboratory prototype are given to show the feasibility of proposed cascaded three-phase symmetrical CW-VM

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.

Low Power/Low Voltage Interface Circuitry for Capacitive Sensors

DEFF Research Database (Denmark)

Furst, Claus Efdmann

This thesis focuses mainly on low power/low voltage interface circuits, implemented in CMOS, for capacitive sensors. A brief discussion of demands and possibilities for analog signal processing in the future is presented. Techniques for low power design is presented. This is done by analyzing power...... power consumption. It is shown that the Sigma-Delta modulator is advantageous when embedded in a feedback loop with a mechanical sensor. Here a micro mechanical capacitive microphone. Feedback and detection circuitry for a capacitive microphone is presented. Practical implementations of low power....../low voltage interface circuitry is presented. It is demonstrated that an amplifier optimized for a capacitive microphone implemented in a standard 0.7 micron CMOS technology competes well with a traditional JFET amplifier. Furthermore a low power/low voltage 3rd order Sigma-Delta modulator is presented...

Power system integration of VSC-HVDC connected offshore wind power plants

DEFF Research Database (Denmark)

Zeni, Lorenzo; Kjær, Philip Carne

This report presents an overview of challenges and solutions for the integration into the power system of offshore wind power plants (WPPs) connected to onshore grids through a voltage-source converter based high voltage direct current (VSC-HVDC) transmission system. Aspects that are touched upon...... of the network in the vicinity of the HVDC station and (iii) limiting characteristics of WPPs such as inherent control and communication delays, presence of mechanical resonances at the same frequency as POD and active power ramp-rate limitations. Clustering of wind power plants The proof of concept...... introduction to justify the study, describe the state-of-art and formulate the project’s objectives, the report is essentially divided into three parts, as follows. Control principles of offshore AC networks The control of offshore AC networks relies purely on power electronics, especially if Type 4 wind...

A New Generalized Two-Stage Direct Power Conversion Topology to Independently Supply Multiple AC Loads from Multiple Power Grids with Adjustable Power Loading

DEFF Research Database (Denmark)

Klumpner, Christian; Blaabjerg, Frede

2004-01-01

) and continuously adjust these power fractions will become a desired feature. This paper presents a generalized Direct Power Converter topology, which is able to connect to multiple AC supplies proving complete decoupling and no circulating power between the input ports and to independently control multiple AC...

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.

Method to predetermine current/power flow change in a dc grid

DEFF Research Database (Denmark)

2017-01-01

occurs at one of the AC/DC converters; establishing a generalized droop feedback gain matrix G; controlling current/power flow within DC grid towards predefined setpoints, by use of control law. The invention presents an analytical approach to derive the generalized feedback gain allowing......The invention relates to a method for controlling current/power flow within a power transmission system, comprising two or more interconnected converter stations. The method comprises the steps of: providing a DC admittance matrix given from the DC grid; providing a current distribution matrix...... for a number of, such as for all possible AC/DC converter outages; providing a DC bus voltage vector for the DC grid; the DC bus voltage vector being a vector containing the values of the voltage change at the AC/DC converters, measured at the AC/DC converters, before, during and after a forced current change...

A Low-Power and Low-Voltage Power Management Strategy for On-Chip Micro Solar Cells

Directory of Open Access Journals (Sweden)

Ismail Cevik

2015-01-01

Full Text Available Fundamental characteristics of on-chip micro solar cell (MSC structures were investigated in this study. Several MSC structures using different layers in three different CMOS processes were designed and fabricated. Effects of PN junction structure and process technology on solar cell performance were measured. Parameters for low-power and low-voltage implementation of power management strategy and boost converter based circuits utilizing fractional voltage maximum power point tracking (FVMPPT algorithm were determined. The FVMPPT algorithm works based on the fraction between the maximum power point operation voltage and the open circuit voltage of the solar cell structure. This ratio is typically between 0.72 and 0.78 for commercially available poly crystalline silicon solar cells that produce several watts of power under typical daylight illumination. Measurements showed that the fractional voltage ratio is much higher and fairly constant between 0.82 and 0.85 for on-chip mono crystalline silicon micro solar cell structures that produce micro watts of power. Mono crystalline silicon solar cell structures were observed to result in better power fill factor (PFF that is higher than 74% indicating a higher energy harvesting efficiency.

Lower-Order Compensation Chain Threshold-Reduction Technique for Multi-Stage Voltage Multipliers

Directory of Open Access Journals (Sweden)

Francesco Dell’ Anna

2018-04-01

Full Text Available This paper presents a novel threshold-compensation technique for multi-stage voltage multipliers employed in low power applications such as passive and autonomous wireless sensing nodes (WSNs powered by energy harvesters. The proposed threshold-reduction technique enables a topological design methodology which, through an optimum control of the trade-off among transistor conductivity and leakage losses, is aimed at maximizing the voltage conversion efficiency (VCE for a given ac input signal and physical chip area occupation. The conducted simulations positively assert the validity of the proposed design methodology, emphasizing the exploitable design space yielded by the transistor connection scheme in the voltage multiplier chain. An experimental validation and comparison of threshold-compensation techniques was performed, adopting 2N5247 N-channel junction field effect transistors (JFETs for the realization of the voltage multiplier prototypes. The attained measurements clearly support the effectiveness of the proposed threshold-reduction approach, which can significantly reduce the chip area occupation for a given target output performance and ac input signal.

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.

Analysis of Voltage Forming Methods for Multiphase Inverters

Directory of Open Access Journals (Sweden)

Tadas Lipinskis

2013-05-01

Full Text Available The article discusses advantages of the multiphase AC induction motor over three or less phase motors. It presents possible stator winding configurations for a multiphase induction motor. Various fault control strategies were reviewed for phases feeding the motor. The authors propose a method for quality evaluation of voltage forming algorithm in the inverter. Simulation of a six-phase voltage source inverter, voltage in which is formed using a simple SPWM control algorithm, was performed in Matlab Simulink. Simulation results were evaluated using the proposed method. Inverter’s power stage was powered by 400 V DC source. The spectrum of output currents was analysed and the magnitude of the main frequency component was at least 12 times greater than the next biggest-magnitude component. The value of rectified inverter voltage was 373 V.Article in Lithuanian

Interlink Converter with Linear Quadratic Regulator Based Current Control for Hybrid AC/DC Microgrid

Directory of Open Access Journals (Sweden)

Dwi Riana Aryani

2017-11-01

Full Text Available A hybrid alternate current/direct current (AC/DC microgrid consists of an AC subgrid and a DC subgrid, and the subgrids are connected through the interlink bidirectional AC/DC converter. In the stand-alone operation mode, it is desirable that the interlink bidirectional AC/DC converter manages proportional power sharing between the subgrids by transferring power from the under-loaded subgrid to the over-loaded one. In terms of system security, the interlink bidirectional AC/DC converter takes an important role, so proper control strategies need to be established. In addition, it is assumed that a battery energy storage system is installed in one subgrid, and the coordinated control of interlink bidirectional AC/DC converter and battery energy storage system converter is required so that the power sharing scheme between subgrids becomes more efficient. For the purpose of designing a tracking controller for the power sharing by interlink bidirectional AC/DC converter in a hybrid AC/DC microgrid, a droop control method generates a power reference for interlink bidirectional AC/DC converter based on the deviation of the system frequency and voltages first and then interlink bidirectional AC/DC converter needs to transfer the power reference to the over-loaded subgrid. For efficiency of this power transferring, a linear quadratic regulator with exponential weighting for the current regulation of interlink bidirectional AC/DC converter is designed in such a way that the resulting microgrid can operate robustly against various uncertainties and the power sharing is carried out quickly. Simulation results show that the proposed interlink bidirectional AC/DC converter control strategy provides robust and efficient power sharing scheme between the subgrids without deteriorating the secure system operation.

A CMOS AC/DC charge pump for a wireless sensor network

International Nuclear Information System (INIS)

Zhang Qiang; Ni Weining; Shi Yin; Yu Yude

2012-01-01

An AC/DC charge pump implemented with MOS FETs has been presented for wireless sensor network applications. The proposed AC/DC charge pump can generate a stable output with low power dissipation and high pumping efficiency, which has been implemented in 0.13 μm CMOS technology. The proposed charge pump employs MOSFET diodes with low thresholds, and improves the conversion efficiency. The analytical model of the voltage multiplier, the simulation results, and the chip testing results are presented.

Analysis and implementation of power management and control strategy for six-phase multilevel ac drive system in fault condition

Directory of Open Access Journals (Sweden)

Sanjeevikumar Padmanaban

2016-03-01

Full Text Available This research article exploits the power management algorithm in post-fault conditions for a six-phase (quad multilevel inverter. The drive circuit consists of four 2-level, three-phase voltage source inverter (VSI supplying a six-phase open-end windings motor or/impedance load, with circumstantial failure of one VSI investigated. A simplified level-shifted pulse-width modulation (PWM algorithm is developed to modulate each couple of three-phase VSI as 3-level output voltage generators in normal operation. The total power of the whole ac drive is shared equally among the four isolated DC sources. The developed post-fault algorithm is applied when there is a fault by one VSI and the load is fed from the remaining three healthy VSIs. In faulty conditions the multilevel outputs are reduced from 3-level to 2-level, but still the system propagates with degraded power. Numerical simulation modelling and experimental tests have been carried out with proposed post-fault control algorithm with three-phase open-end (asymmetrical induction motor/R-L impedance load. A complete set of simulation and experimental results provided in this paper shows close agreement with the developed theoretical background.

HVDC transmission preferred to 750 kV ac

Energy Technology Data Exchange (ETDEWEB)

1965-06-25

It is unlikely that there will be a need in Britain for ac transmission voltages above 400 kV. But with the growing load density in the large conurbations with no possibility of local generation, high voltage dc transmission is likely to be most useful. It was concluded that by 1971 the 400 kV supergrid would be nation-wide and 6,200 circuit miles should be in service. With the expansion to accommodate the large new generating stations, the 400 kV supergrid would become an extremely high power distribution network rather than a transmission system. A higher voltage for transmission is outside the rational limit of speculation for a country the size of Britain.

Design and Implementation of a High-Voltage Generator with Output Voltage Control for Vehicle ER Shock-Absorber Applications

Directory of Open Access Journals (Sweden)

Chih-Lung Shen

2013-01-01

Full Text Available A self-oscillating high-voltage generator is proposed to supply voltage for a suspension system in order to control the damping force of an electrorheological (ER fluid shock absorber. By controlling the output voltage level of the generator, the damping force in the ER fluid shock absorber can be adjusted immediately. The shock absorber is part of the suspension system. The high-voltage generator drives a power transistor based on self-excited oscillation, which converts dc to ac. A high-frequency transformer with high turns ratio is used to increase the voltage. In addition, the system uses the car battery as dc power supply. By regulating the duty cycle of the main switch in the buck converter, the output voltage of the buck converter can be linearly adjusted so as to obtain a specific high voltage for ER. The driving system is self-excited; that is, no additional external driving circuit is required. Thus, it reduces cost and simplifies system structure. A prototype version of the actual product is studied to measure and evaluate the key waveforms. The feasibility of the proposed system is verified based on experimental results.

Advances in high voltage power switching with GTOs

International Nuclear Information System (INIS)

Podlesak, T.F.

1990-01-01

The control of high voltage at high power, particularly opening switches, has been difficult in the past. Using gate turnoff thyristors (GTOs) arranged in series enables large currents to be switched at high voltage. The authors report a high voltage opening switch has been successfully demonstrated. This switch uses GTOs in series and successfully operates at voltages higher than the rated voltage of the individual devices. It is believed that this is the first time this has been successfully demonstrated, in that GTOs have been operated in series before, but always in a manner as to not exceed the voltage capability of the individual devices. In short, the devices have not worked together, sharing the voltage, but one device has been operated using several backup devices. Of particular interest is how well the individual devices share the voltage applied to them. Equal voltage sharing between devices is absolutely essential, in order to not exceed the voltage rating of any of the devices in the series chain. This is accomplished at high (microsecond) switching speeds. Thus, the system is useful for high frequency applications as well as high power, making for a flexible circuit system element. This demonstration system is rated at 5 KV and uses 1 KV devices. A larger 24 KV system is under design and will use 4.5 KV devices. In order to design the 24 KV switch, the safe operating area of the large devices must be known thoroughly

Priority Control Strategy of VSC-MTDC System for Integrating Wind Power

Directory of Open Access Journals (Sweden)

Wen-ning Yan

2015-01-01

Full Text Available For the obvious advantages in integrating wind power, multiterminal HVDC transmission system (VSC-MTDC is widely used. The priority control strategy is proposed in this paper considering the penetration rate of wind power for the AC grid. The strategy aims to solve the problems of power allocation and DC voltage control of the DC system. The main advantage of this strategy is that the demands for wind power of different areas can be satisfied and a power reference for the wind power trade can also be provided when wind farms transmit active power to several AC grids through the DC network. The objective is that power is well distributed according to the output power of wind farm with the demand of AC system and satisfactory control performance of DC voltage is obtained.

Stochastic Dynamic AC Optimal Power Flow Based on a Multivariate Short-Term Wind Power Scenario Forecasting Model

Directory of Open Access Journals (Sweden)

Wenlei Bai

2017-12-01

Full Text Available The deterministic methods generally used to solve DC optimal power flow (OPF do not fully capture the uncertainty information in wind power, and thus their solutions could be suboptimal. However, the stochastic dynamic AC OPF problem can be used to find an optimal solution by fully capturing the uncertainty information of wind power. That uncertainty information of future wind power can be well represented by the short-term future wind power scenarios that are forecasted using the generalized dynamic factor model (GDFM—a novel multivariate statistical wind power forecasting model. Furthermore, the GDFM can accurately represent the spatial and temporal correlations among wind farms through the multivariate stochastic process. Fully capturing the uncertainty information in the spatially and temporally correlated GDFM scenarios can lead to a better AC OPF solution under a high penetration level of wind power. Since the GDFM is a factor analysis based model, the computational time can also be reduced. In order to further reduce the computational time, a modified artificial bee colony (ABC algorithm is used to solve the AC OPF problem based on the GDFM forecasting scenarios. Using the modified ABC algorithm based on the GDFM forecasting scenarios has resulted in better AC OPF’ solutions on an IEEE 118-bus system at every hour for 24 h.

Analysis and control of induction generator supplying stand-alone AC loads employing a Matrix Converter

Directory of Open Access Journals (Sweden)

Sumedha Mahajan

2017-04-01

Full Text Available This paper proposes a Capacitor Excited Induction Generator (CEIG-Matrix Converter (MC system for feeding stand-alone AC loads. The variable output voltage magnitude and frequency from CEIG is converted into a constant voltage magnitude and frequency at the load terminals by controlling MC using Space Vector Modulation (SVM technique. This single-stage MC is turned up as a good alternative for the proposed system against commonly used AC/DC/AC two stage power converters. The configuration and implementation of the closed-loop control scheme employing dSPACE 1103 real time controller have been fully described in the paper. The proposed closed-loop controller regulates the AC load voltage irrespective of changes in the prime mover speed and load. A method for predetermining the steady-state performance of the proposed system has been developed and described with relevant analytical expressions. The effectiveness of the proposed system is exemplified through simulation results for various operating conditions. The proposed control technique is further validated using an experimental setup developed in the laboratory.

Fuzzy Controlled Parallel AC-DC Converter for PFC

Directory of Open Access Journals (Sweden)

M Subba Rao

2011-01-01

Full Text Available Paralleling of converter modules is a well-known technique that is often used in medium-power applications to achieve the desired output power by using smaller size of high frequency transformers and inductors. In this paper, a parallel-connected single-phase PFC topology using flyback and forward converters is proposed to improve the output voltage regulation with simultaneous input power factor correction (PFC and control. The goal of the control is to stabilize the output voltage of the converter against the load variations. The paper presents the derivation of fuzzy control rules for the dc/dc converter circuit and control algorithm for regulating the dc/dc converter. This paper presents a design example and circuit analysis for 200 W power supply. The proposed approach offers cost effective, compact and efficient AC/DC converter by the use of parallel power processing. MATLAB/SIMULINK is used for implementation and simulation results show the performance improvement.

Methods of computing steady-state voltage stability margins of power systems

Science.gov (United States)

Chow, Joe Hong; Ghiocel, Scott Gordon

2018-03-20

In steady-state voltage stability analysis, as load increases toward a maximum, conventional Newton-Raphson power flow Jacobian matrix becomes increasingly ill-conditioned so power flow fails to converge before reaching maximum loading. A method to directly eliminate this singularity reformulates the power flow problem by introducing an AQ bus with specified bus angle and reactive power consumption of a load bus. For steady-state voltage stability analysis, the angle separation between the swing bus and AQ bus can be varied to control power transfer to the load, rather than specifying the load power itself. For an AQ bus, the power flow formulation is only made up of a reactive power equation, thus reducing the size of the Jacobian matrix by one. This reduced Jacobian matrix is nonsingular at the critical voltage point, eliminating a major difficulty in voltage stability analysis for power system operations.

AC/DC/pulsed-power modulator for corona-plasma generation

NARCIS (Netherlands)

Ariaans, T.H.P.; Pemen, A.J.M.; Winands, G.J.J.; Heesch, van E.J.M.; Liu, Z.

2009-01-01

Gas-cleaning techniques using nonthermal plasma are slowly introduced into industry nowadays. In this paper, we present a novel power modulator for the efficient generation of large-volume corona plasma. No expensive high-voltage components are required. Switching is done at an intermediate voltage

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)

Impact of the Voltage Dips in Shipboard Microgrid Power Systems

DEFF Research Database (Denmark)

Liu, Wenzhao; Guerrero, Josep M.; Savaghebi, Mehdi

2017-01-01

Voltage and frequency transient variations are the most common power quality issues in a ship microgrid system. In this paper, the impacts of the voltage dips induced by the sudden-load of ballast pump are analyzed in detail for the ship power systems. Several relevant ship power quality standards...

Protective and control relays as coal-mine power-supply ACS subsystem

Science.gov (United States)

Kostin, V. N.; Minakova, T. E.

2017-10-01

The paper presents instantaneous selective short-circuit protection for the cabling of the underground part of a coal mine and central control algorithms as a Coal-Mine Power-Supply ACS Subsystem. In order to improve the reliability of electricity supply and reduce the mining equipment down-time, a dual channel relay protection and central control system is proposed as a subsystem of the coal-mine power-supply automated control system (PS ACS).

Coordinated control of three-phase AC and DC type EV–ESSs for efficient hybrid microgrid operations

International Nuclear Information System (INIS)

Rahman, Md Shamiur; Hossain, M.J.; Lu, Junwei

2016-01-01

Highlights: • A coordinated control is proposed for three-phase AC and DC type electric vehicles. • A four-quadrant interlinking converter is designed for hybrid microgrid operations. • Concurrent real irradiation data and commercial load profile are used for testing. • Unbalanced scenario due to single-phase electric vehicle charging is considered. • Improved AC and DC bus voltages and frequency regulations are achieved. - Abstract: This paper presents a three-layered coordinated control to incorporate three-phase (3P) alternating current (AC) and direct current (DC) type electric vehicle energy storage systems (EV–ESSs) for improved hybrid AC/DC microgrid operations. The first layer of the algorithm ensures DC subgrid management by regulating the DC bus voltage and DC side power management. The second and third layer manages AC subgrid by regulating the AC bus voltage and the frequency by managing reactive and active power respectively. The multi-layered coordination is embedded into the microgrid central controller (MGCC) which controls the interlinking controller in between AC and DC microgrid and the interfacing controllers of the participating electric vehicles (EVs) and distributed generation (DG) units. The whole system is designed in MATLAB/SIMULINK® environment resembling the under construction microgrid at Griffith University, Australia. Extensive case studies are performed using real life irradiation data and commercial loads of the campus buildings. Impacts of homogeneous and heterogeneous single-phase EV charging are investigated to observe both balanced and unbalanced scenarios. Synchronization during the transition from the islanded to grid-tied mode is tested considering a contingency situation. From the comparative simulation results it is evident that the proposed controller exhibits effective, reliable and robust performance for all the cases.

High voltage fast switches for nuclear applications

International Nuclear Information System (INIS)

Chatroux, D.; Lausenaz, Y.; Villard, J.F.; Lafore, D.

1999-01-01

SILVA process consists in a selective ionization of the 235 uranium isotope, using laser beams generated by dye lasers pumped by copper vapour laser (C.V.L.). SILVA involves power electronic for 3 power supplies: - copper vapour laser power supply, - extraction power supply to generate the electric field in the vapour, and - electron beam power supply for vapour generation. This article reviews the main switches that are proposed on the market or are on development and that could be used in SILVA power supplies. The SILVA technical requirements are: high power, high voltage and very short pulses (200 ns width). (A.C.)

Isolated and soft-switched power converter

Science.gov (United States)

Peng, Fang Zheng; Adams, Donald Joe

2002-01-01

An isolated and soft-switched power converter is used for DC/DC and DC/DC/AC power conversion. The power converter includes two resonant tank circuits coupled back-to-back through an isolation transformer. Each resonant tank circuit includes a pair of resonant capacitors connected in series as a resonant leg, a pair of tank capacitors connected in series as a tank leg, and a pair of switching devices with anti-parallel clamping diodes coupled in series as resonant switches and clamping devices for the resonant leg. The power converter is well suited for DC/DC and DC/DC/AC power conversion applications in which high-voltage isolation, DC to DC voltage boost, bidirectional power flow, and a minimal number of conventional switching components are important design objectives. For example, the power converter is especially well suited to electric vehicle applications and load-side electric generation and storage systems, and other applications in which these objectives are important. The power converter may be used for many different applications, including electric vehicles, hybrid combustion/electric vehicles, fuel-cell powered vehicles with low-voltage starting, remote power sources utilizing low-voltage DC power sources, such as photovoltaics and others, electric power backup systems, and load-side electric storage and generation systems.

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.

DC Vs AC - War Of Currents For Future Power Systems A HVDC Technology Overview

Directory of Open Access Journals (Sweden)

Anil K. Rai

2015-08-01

Full Text Available DC vs AC discussion began in 1880s with development of first commercial power transmission in Wall Street New York. Later when AC technology came into notice by efforts of inventor and researcher Sir Nicola Tesla soon the advantages of AC transmission and AC devices overtook the DC technology. It was hoped that DC technology had lost battle of currents. Today with researches going on FACTS devices and bulk power transmission HVDC has again gained a reputation in power sector. Solution of this centuries old debate is to develop HVDC systems that assists HVAC systems for better performance stability and control

AC Initiation System.

Science.gov (United States)

An ac initiation system is described which uses three ac transmission signals interlocked for safety by frequency, phase, and power discrimination...The ac initiation system is pre-armed by the application of two ac signals have the proper phases, and activates a load when an ac power signal of the proper frequency and power level is applied. (Author)

Induced voltages in metallic pipelines near power transmission lines

International Nuclear Information System (INIS)

Grcev, Leonid; Jankov, Voislav; Filiposki, Velimir

2002-01-01

With the continuous development of the electric power system and the pipeline networks used to convey oil or natural gas, cases of close proximity of high voltage structures and metallic pipelines become more and more frequent. Accordingly there is a growing concern about possible hazards resulting from voltages induced in the metallic pipelines by magnetic coupling with nearby power transmission lines. This paper presents a methodology for computation of the induced voltages in buried isolated metallic pipelines. A practical example of computation is also presented. (Author)

Coordinated Voltage Control Scheme for VSC-HVDC Connected Wind Power Plants

DEFF Research Database (Denmark)

Guo, Yifei; Gao, Houlei; Wu, Qiuwei

2017-01-01

This paper proposes a coordinated voltage control scheme based on model predictive control (MPC) for voltage source converter‐based high voltage direct current (VSC‐HVDC) connected wind power plants (WPPs). In the proposed scheme, voltage regulation capabilities of VSC and WTGs are fully utilized...... and optimally coordinated. Two control modes, namely operation optimization mode and corrective mode, are designed to coordinate voltage control and economic operation of the system. In the first mode, the control objective includes the bus voltages, power losses and dynamic Var reserves of wind turbine...

Power decoupling method for single phase differential buck converter

DEFF Research Database (Denmark)

Yao, Wenli; Tang, Yi; Zhang, Xiaobin

2015-01-01

inverter to improve the dc link power quality, and an improved active power decoupling method is proposed to achieve ripple power reduction for both AC-DC and DC-AC conversions. The ripple energy storage is realized by the filter capacitors, which are connected between the output terminal and the negative...... generation technique is proposed to provide accurate ripple power compensation, and closed-loop controllers are also designed based on small signal models. The effectiveness of this power decoupling method is verified by detailed simulation studies as well as laboratory prototype experimental results....... dc bus. By properly controlling the differential mode voltage of the capacitors, it is possible to transfer desired energy between the DC port and AC port. The common mode voltage is controlled in such a way that the ripple power on the dc side will be reduced. Furthermore, an autonomous reference...

Using a Voltage Domain Programmable Technique for Low-Power Management Cell-Based Design

Directory of Open Access Journals (Sweden)

Ching-Hwa Cheng

2011-09-01

Full Text Available The Multi-voltage technique is an effective way to reduce power consumption. In the proposed cell-based voltage domain programmable (VDP technique, the high and low voltages applied to logic gates are programmable. The flexible voltage domain reassignment allows the chip performance and power consumption to be dynamically adjusted. In the proposed technique, the power switches possess the feature of flexible programming after chip manufacturing. This VDP method does not use an external voltage regulator to regulate the supply voltage level from outside of the chip but can be easily integrated within the design. This novel technique is proven by use of a video decoder test chip, which shows 55% and 61% power reductions compared to conventional single-Vdd and low-voltage designs, respectively. This power-aware performance adjusting mechanism shows great power reduction with a good power-performance management mechanism.

Compensation methods applied in current control schemes for large AC drive systems

DEFF Research Database (Denmark)

Rus, D. C.; Preda, N. S.; Teodorescu, Remus

2012-01-01

The paper deals with modified PI current control structures for large AC drive systems which use surface mounted permanent magnet synchronous machines or squirrel-cage induction motors supplied with voltage source inverters. In order to reduce the power losses caused by high frequency switching...

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...

Impedance-Source Networks for Electric Power Conversion Part II

DEFF Research Database (Denmark)

Siwakoti, Yam P.; Peng, Fang Zheng; Blaabjerg, Frede

2015-01-01

Impedance-source networks cover the entire spectrum of electric power conversion applications (dc-dc, dc-ac, ac-dc, ac-ac) controlled and modulated by different modulation strategies to generate the desired dc or ac voltage and current at the output. A comprehensive review of various impedance......-source-network-based power converters has been covered in a previous paper and main topologies were discussed from an application point of view. Now Part II provides a comprehensive review of the most popular control and modulation strategies for impedance-source network-based power converters/inverters. These methods...

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

Statistical time lags in ac discharges

International Nuclear Information System (INIS)

Sobota, A; Kanters, J H M; Van Veldhuizen, E M; Haverlag, M; Manders, F

2011-01-01

The paper presents statistical time lags measured for breakdown events in near-atmospheric pressure argon and xenon. Ac voltage at 100, 400 and 800 kHz was used to drive the breakdown processes, and the voltage amplitude slope was varied between 10 and 1280 V ms -1 . The values obtained for the statistical time lags are roughly between 1 and 150 ms. It is shown that the statistical time lags in ac-driven discharges follow the same general trends as the discharges driven by voltage of monotonic slope. In addition, the validity of the Cobine-Easton expression is tested at an alternating voltage form.

Statistical time lags in ac discharges

Energy Technology Data Exchange (ETDEWEB)

Sobota, A; Kanters, J H M; Van Veldhuizen, E M; Haverlag, M [Eindhoven University of Technology, Department of Applied Physics, Postbus 513, 5600MB Eindhoven (Netherlands); Manders, F, E-mail: a.sobota@tue.nl [Philips Lighting, LightLabs, Mathildelaan 1, 5600JM Eindhoven (Netherlands)

2011-04-06

The paper presents statistical time lags measured for breakdown events in near-atmospheric pressure argon and xenon. Ac voltage at 100, 400 and 800 kHz was used to drive the breakdown processes, and the voltage amplitude slope was varied between 10 and 1280 V ms{sup -1}. The values obtained for the statistical time lags are roughly between 1 and 150 ms. It is shown that the statistical time lags in ac-driven discharges follow the same general trends as the discharges driven by voltage of monotonic slope. In addition, the validity of the Cobine-Easton expression is tested at an alternating voltage form.

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

Innovative application of AC-voltammetry in the characterization of oxides nanolayers formed on metals, under the effect of AC-perturbations

Energy Technology Data Exchange (ETDEWEB)

Bueno, V.; Lazzari, L.; Ormellesse, M. [Politecnico di Milano, Milan (Italy). Dept. of Chemistry, Materials and Chemical Engineering; Spinelli, P. [Politecnico di Torino, Torino (Italy). Dept. of Materials Science and Chemical Engineering

2008-07-01

Stray AC-currents have been reported to cause many cases of unwanted corrosion on metallic structures. This study characterized the formation and stability of the surface oxide film formed on mild steel under the effect of AC voltage in a very basic environment. The response of the system to DC signals was examined, along with its reversibility to AC perturbations. SEM analysis was used to complement AC-Voltammetry. Reaction mechanisms responsible for the AC-corrosion were formulated. AC-Voltammetry involves the application of a controlled sinusoidal voltage onto a solid working electrode while it is being swept in a DC-voltage range, with the faradaic or capacitative components of the resulting AC-current being recorded. The innovative aspect is the application of AC-V to characterize its nano-surface while it is being affected by AC-signals. It was concluded that the AC-V can be useful for the study of redox processes occurring at the surface of a reactive electrode and for the application of a considerable AC perturbation to the electrode in a potentiostatically controlled way. According to the electrochemistry of the double layer, there are 3 main reactions in the NaOH 1M media that are not reversible to DC nor to AC perturbations in the range of cathodic protection of mild steel. When designing metallic systems susceptible to stray currents, the AC-V could quantify the final faradaic, resistive and capacitative responses. 6 refs., 1 fig.

AC losses in horizontally parallel HTS tapes for possible wireless power transfer applications

Science.gov (United States)

Shen, Boyang; Geng, Jianzhao; Zhang, Xiuchang; Fu, Lin; Li, Chao; Zhang, Heng; Dong, Qihuan; Ma, Jun; Gawith, James; Coombs, T. A.

2017-12-01

This paper presents the concept of using horizontally parallel HTS tapes with AC loss study, and the investigation on possible wireless power transfer (WPT) applications. An example of three parallel HTS tapes was proposed, whose AC loss study was carried out both from experiment using electrical method; and simulation using 2D H-formulation on the FEM platform of COMSOL Multiphysics. The electromagnetic induction around the three parallel tapes was monitored using COMSOL simulation. The electromagnetic induction and AC losses generated by a conventional three turn coil was simulated as well, and then compared to the case of three parallel tapes with the same AC transport current. The analysis demonstrates that HTS parallel tapes could be potentially used into wireless power transfer systems, which could have lower total AC losses than conventional HTS coils.

Bi-directional power control system for voltage converter

Science.gov (United States)

Garrigan, Neil Richard; King, Robert Dean; Schwartz, James Edward

1999-01-01

A control system for a voltage converter includes: a power comparator for comparing a power signal on input terminals of the converter with a commanded power signal and producing a power comparison signal; a power regulator for transforming the power comparison signal to a commanded current signal; a current comparator for comparing the commanded current signal with a measured current signal on output terminals of the converter and producing a current comparison signal; a current regulator for transforming the current comparison signal to a pulse width modulator (PWM) duty cycle command signal; and a PWM for using the PWM duty cycle command signal to control electrical switches of the converter. The control system may further include: a command multiplier for converting a voltage signal across the output terminals of the converter to a gain signal having a value between zero (0) and unity (1), and a power multiplier for multiplying the commanded power signal by the gain signal to provide a limited commanded power signal, wherein power comparator compares the limited commanded power signal with the power signal on the input terminals.

High voltage power network construction

CERN Document Server

Harker, Keith

2018-01-01

This book examines the key requirements, considerations, complexities and constraints relevant to the task of high voltage power network construction, from design, finance, contracts and project management to installation and commissioning, with the aim of providing an overview of the holistic end to end construction task in a single volume.

Stochastic reactive power market with volatility of wind power considering voltage security

International Nuclear Information System (INIS)

Kargarian, A.; Raoofat, M.

2011-01-01

While wind power generation is growing rapidly around the globe; its stochastic nature affects the system operation in many different aspects. In this paper, the impact of wind power volatility on the reactive power market is taken into account. The paper presents a novel stochastic method for optimal reactive power market clearing considering voltage security and volatile nature of the wind. The proposed optimization algorithm uses a multiobjective nonlinear programming technique to minimize market payment and simultaneously maximize voltage security margin. Considering a set of probable wind speeds, in the first stage, the proposed algorithm seeks to minimize expected system payment which is summation of reactive power payment and transmission loss cost. The object of the second stage is maximization of expected voltage security margin to increase the system loadability and security. Finally, in the last stage, a multiobjective function is presented to schedule the stochastic reactive power market using results of two previous stages. The proposed algorithm is applied to IEEE 14-bus test system. As a benchmark, Monte Carlo Simulation method is utilized to simulate the actual market of given period of time to evaluate results of the proposed algorithm, and satisfactory results are achieved. -- Highlights: →The paper proposes a new algorithm for stochastic reactive power market clearing. →The stochastic nature of the wind which impacts the system operation and market clearing process, is taken into account. →The paper suggests an expected voltage stability margin and optimizes it in conjunction with expected total market payment. →To clear the market with two mentioned objective functions, a three-stage multiobjective nonlinear programming is implemented. →Also, a simple method is suggested to determine a suitable priority coefficient between two individual objective functions.

A study of Schwarz converters for nuclear powered spacecraft

Science.gov (United States)

Stuart, Thomas A.; Schwarze, Gene E.

1987-01-01

High power space systems which use low dc voltage, high current sources such as thermoelectric generators, will most likely require high voltage conversion for transmission purposes. This study considers the use of the Schwarz resonant converter for use as the basic building block to accomplish this low-to-high voltage conversion for either a dc or an ac spacecraft bus. The Schwarz converter has the important assets of both inherent fault tolerance and resonant operation; parallel operation in modular form is possible. A regulated dc spacecraft bus requires only a single stage converter while a constant frequency ac bus requires a cascaded Schwarz converter configuration. If the power system requires constant output power from the dc generator, then a second converter is required to route unneeded power to a ballast load.

Simulation comparison of proportional integral derivative and fuzzy logic in controlling AC-DC buck boost converter

Science.gov (United States)

Faisal, A.; Hasan, S.; Suherman

2018-03-01

AC-DC converter is widely used in the commercial industry even for daily purposes. The AC-DC converter is used to convert AC voltage into DC. In order to obtain the desired output voltage, the converter usually has a controllable regulator. This paper discusses buck boost regulator with a power MOSFET as switching component which is adjusted based on the duty cycle of pulse width modulation (PWM). The main problems of the buck boost converter at start up are the high overshoot, the long peak time and rise time. This paper compares the effectiveness of two control techniques: proportional integral derivative (PID) and fuzzy logic control in controlling the buck boost converter through simulations. The results show that the PID is more sensitive to voltage change than fuzzy logic. However, PID generates higher overshoot, long peak time and rise time. On the other hand, fuzzy logic generates no overshoot and shorter rise time.

Coordination of voltage and reactive power control in the extra high voltage substations based on the example of solutions applied in the national power system

Directory of Open Access Journals (Sweden)

Dariusz Kołodziej

2012-06-01

Full Text Available This paper presents examples of coordination between automatic voltage and reactive power control systems (ARST covering adjacent and strongly related extra high voltage substations. Included are conclusions resulting from the use of these solutions. The Institute of Power Engineering, Gdańsk Division has developed and deployed ARST systems in the national power system for a dozen or so years.

Coordinated voltage control in offshore HVDC connected cluster of wind power plants

DEFF Research Database (Denmark)

Sakamuri, Jayachandra Naidu; Rather, Zakir Hussain; Rimez, Johan

This paper presents a coordinated voltage control scheme (CVCS) for a cluster of offshore wind power plants connected to a voltage-source converter-based high-voltage direct current system. The primary control point of the proposed voltage control scheme is the introduced Pilot bus, which is having...... by dispatching reactive power references to each wind turbine (WT) in the wind power plant cluster based on their available reactive power margin and network sensitivity-based participation factors, which are derived from the dV/dQ sensitivity of a WT bus w.r.t. the Pilot bus. This method leads...

A direct power conversion topology for grid integrations of hybrid AC/DC resources

DEFF Research Database (Denmark)

Liu, Xiong; Loh, Poh Chiang; Wang, Peng

2012-01-01

and modulation schemes are proposed to extract the commanded current from the input ac/dc sources to the grid and guarantee high quality ac/dc inputs and ac output current waveforms with unity power factors. The proposed modulation scheme for sinusoidal outputs of the VMC is mathematically proved...

Study on AC loss measurements of HTS power cable for standardizing

Science.gov (United States)

Mukoyama, Shinichi; Amemiya, Naoyuki; Watanabe, Kazuo; Iijima, Yasuhiro; Mido, Nobuhiro; Masuda, Takao; Morimura, Toshiya; Oya, Masayoshi; Nakano, Tetsutaro; Yamamoto, Kiyoshi

2017-09-01

High-temperature superconducting power cables (HTS cables) have been developed for more than 20 years. In addition of the cable developments, the test methods of the HTS cables have been discussed and proposed in many laboratories and companies. Recently the test methods of the HTS cables is required to standardize and to common in the world. CIGRE made the working group (B1-31) for the discussion of the test methods of the HTS cables as a power cable, and published the recommendation of the test method. Additionally, IEC TC20 submitted the New Work Item Proposal (NP) based on the recommendation of CIGRE this year, IEC TC20 and IEC TC90 started the standardization work on Testing of HTS AC cables. However, the individual test method that used to measure a performance of HTS cables hasn’t been established as world’s common methods. The AC loss is one of the most important properties to disseminate low loss and economical efficient HTS cables in the world. We regard to establish the method of the AC loss measurements in rational and in high accuracy. Japan is at a leading position in the AC loss study, because Japanese researchers have studied on the AC loss technically and scientifically, and also developed the effective technologies for the AC loss reduction. The JP domestic commission of TC90 made a working team to discussion the methods of the AC loss measurements for aiming an international standard finally. This paper reports about the AC loss measurement of two type of the HTS conductors, such as a HTS conductor without a HTS shield and a HTS conductor with a HTS shield. The AC loss measurement method is suggested by the electrical method..

The electrical system of nuclear power plant

International Nuclear Information System (INIS)

Firman Silitonga; Gunarwan Prayitno

2009-01-01

In these system, electrical power system is supplied from two-offsite transmission system respective main transformer and house service transformer; and reserve transformer. The electrical load in these system consist of safety electrical system and non-safety electrical system, The safety electrical and non safety electrical systems consist of four 6,9 kV AC medium voltage bus and 480 V AC low voltage bus system. The DC power system consist of four safety 125 V DC power system and the two non-safety 125 DC power systems. The equipment in these electrical system is main turbine-generator; GTG safety; GTG alternate; uninterrupted power supply (UPS) and battery system. To protect electrical equipment and building to direct stroke and non direct stroke disturbances is installed netral grounding system and lightning protection and protection the personnel to touch-voltage is installed equipment grounding system and station grounding. The lightning arrester system is connected to station station grounding system. (author)

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 ...

A novel power converter for photovoltaic applications

Science.gov (United States)

Yuvarajan, S.; Yu, Dachuan; Xu, Shanguang

A simple and economical power conditioner to convert the power available from solar panels into 60 Hz ac voltage is described. The raw dc voltage from the solar panels is converted to a regulated dc voltage using a boost converter and a large capacitor and the dc output is then converted to 60 Hz ac using a bridge inverter. The ratio between the load current and the short-circuit current of a PV panel at maximum power point is nearly constant for different insolation (light) levels and this property is utilized in designing a simple maximum power point tracking (MPPT) controller. The controller includes a novel arrangement for sensing the short-circuit current without disturbing the operation of the PV panel and implementing MPPT. The switching losses in the inverter are reduced by using snubbers. The results obtained on an experimental converter are presented.

Active Power Regulation based on Droop for AC Microgrid

DEFF Research Database (Denmark)

Li, Chendan; Coelho, Ernane A. A.; Firoozabadi, Mehdi Savaghebi

2015-01-01

In this paper, two different control strategies are proposed to address the active power regulation issue in AC microgrids. The principle of power regulation in the droop controller is firstly introduced. Frequency scheduling and droop gain scheduling on top of droop control is proposed...... to successfully follow the active power command. The limitation of each method is discussed in term of small signal stability and light load sharing, respectively. Discussion on the effects of power command is also given. The simulation is carried out for both the strategies to verify the active power control...

Voltage resonant inverter as a power source

OpenAIRE

Lupenko, Anatoliy; Stakhiv, Petro

2014-01-01

The operation mode of a voltage resonant inverter as a power source with variable load is analyzed. In order to reduce load power variations, an approach to development of the inverter’s load power response based on providing similar positive and negative power deviations from its nominal value has been proposed. The design procedure for resonant inverter with open loop structure as a power source has been elaborated. For a high pressure sodium lamp as a load, the power deviation of about 4% ...

High-voltage, high-power architecture considerations

International Nuclear Information System (INIS)

Moser, R.L.

1985-01-01

Three basic EPS architectures, direct energy transfer, peak-power tracking, and a potential EPS architecture for a nuclear reactor are described and compared. Considerations for the power source and energy storage are discussed. Factors to be considered in selecting the operating voltage are pointed out. Other EPS architecture considerations are autonomy, solar array degrees of freedom, and EPS modularity. It was concluded that selection of the power source and energy storage has major impacts on the spacecraft architecture and mass

Improved SCR ac Motor Controller for Battery Powered Urban Electric Vehicles

Science.gov (United States)

Latos, T. S.

1982-01-01

An improved ac motor controller, which when coupled to a standard ac induction motor and a dc propulsion battery would provide a complete electric vehicle power train with the exception of the mechanical transmission and drive wheels was designed. In such a system, the motor controller converts the dc electrical power available at the battery terminals to ac electrical power for the induction motor in response to the drivers commands. The performance requirements of a hypothetical electric vehicle with an upper weight bound of 1590 kg (3500 lb) were used to determine the power rating of the controller. Vehicle acceleration capability, top speed, and gradeability requisites were contained in the Society of Automotive Engineers (SAE) Schedule 227a(d) driving cycle. The important capabilities contained in this driving cycle are a vehicle acceleration requirement of 0 to 72.4 kmph (0 to 45 mph) in 28 seconds a top speed of 88.5 kmph (55 mph), and the ability to negotiate a 10% grade at 48 kmph (30 mph). A 10% grade is defined as one foot of vertical rise per 10 feet of horizontal distance.

Impute DC link (IDCL) cell based power converters and control thereof

Science.gov (United States)

Divan, Deepakraj M.; Prasai, Anish; Hernendez, Jorge; Moghe, Rohit; Iyer, Amrit; Kandula, Rajendra Prasad

2016-04-26

Power flow controllers based on Imputed DC Link (IDCL) cells are provided. The IDCL cell is a self-contained power electronic building block (PEBB). The IDCL cell may be stacked in series and parallel to achieve power flow control at higher voltage and current levels. Each IDCL cell may comprise a gate drive, a voltage sharing module, and a thermal management component in order to facilitate easy integration of the cell into a variety of applications. By providing direct AC conversion, the IDCL cell based AC/AC converters reduce device count, eliminate the use of electrolytic capacitors that have life and reliability issues, and improve system efficiency compared with similarly rated back-to-back inverter system.

Utility Interfaced Pulse-Width Modulation of Solar Fed Voltage ...

African Journals Online (AJOL)

Utility Interfaced Pulse-Width Modulation of Solar Fed Voltage Source Inverter Using Fixed-Band Hysteresis Current Controller Method. ... with the conversion of solar energy into electrical energy; boosting the dc power; inversion of the dc to ac and then synchronization of the inverter output with the utility, and consequently, ...

High-Voltage, Low-Power BNC Feedthrough Terminator

Science.gov (United States)

Bearden, Douglas

2012-01-01

This innovation is a high-voltage, lowpower BNC (Bayonet Neill-Concelman) feedthrough that enables the user to terminate an instrumentation cable properly while connected to a high voltage, without the use of a voltage divider. This feedthrough is low power, which will not load the source, and will properly terminate the instrumentation cable to the instrumentation, even if the cable impedance is not constant. The Space Shuttle Program had a requirement to measure voltage transients on the orbiter bus through the Ground Lightning Measurement System (GLMS). This measurement has a bandwidth requirement of 1 MHz. The GLMS voltage measurement is connected to the orbiter through a DC panel. The DC panel is connected to the bus through a nonuniform cable that is approximately 75 ft (approximately equal to 23 m) long. A 15-ft (approximately equal to 5-m), 50-ohm triaxial cable is connected between the DC panel and the digitizer. Based on calculations and simulations, cable resonances and reflections due to mismatched impedances of the cable connecting the orbiter bus and the digitizer causes the output not to reflect accurately what is on the bus. A voltage divider at the DC panel, and terminating the 50-ohm cable properly, would eliminate this issue. Due to implementation issues, an alternative design was needed to terminate the cable properly without the use of a voltage divider. Analysis shows how the cable resonances and reflections due to the mismatched impedances of the cable connecting the orbiter bus and the digitizer causes the output not to reflect accurately what is on the bus. After simulating a dampening circuit located at the digitizer, simulations were performed to show how the cable resonances were dampened and the accuracy was improved significantly. Test cables built to verify simulations were accurate. Since the dampening circuit is low power, it can be packaged in a BNC feedthrough.

High voltage power supplies for INDUS-2 RF system

International Nuclear Information System (INIS)

Badapanda, M.K.; Hannurkar, P.R.

2003-01-01

The RF system of Indus-2 employs klystron amplifiers operating at 505.812 MHz. A precession controlled high voltage DC supply of appropriate rating is needed for each klystron amplifier, as its bias supply. Since internal flashover and arcing are common with the operation of these klystrons and stored energies beyond particular limit inside its bias power supply is detrimental to this device, a properly designed crowbar is incorporated between each klystron and its power supply. This crowbar bypass these stored energies and helps protecting klystron under any of these unfavorable conditions. In either case, power supply sees a near short circuit across its load. So, its power circuit is designed to reduce the fault current level and its various components are also designed to withstand these fault currents, as and when it appears. Finally, operation of these high voltage power supplies (HVPS) generates lot of harmonics on the source side, which distort the input waveform substantially and reduces the input power factor also. Source multiplication between two power supplies are planned to improve upon above parameters and suitable detuned line filters are incorporated to keep the input voltage total harmonics distortion (THD) below 5 % and input power factor (IFF) near unity. (author)

High voltage AC/AC electrochemical capacitor operating at low temperature in salt aqueous electrolyte

Science.gov (United States)

Abbas, Qamar; Béguin, François

2016-06-01

We demonstrate that an activated carbon (AC)-based electrochemical capacitor implementing aqueous lithium sulfate electrolyte in 7:3 vol:vol water/methanol mixture can operate down to -40 °C with good electrochemical performance. Three-electrode cell investigations show that the faradaic contributions related with hydrogen chemisorption in the negative AC electrode are thermodynamically unfavored at -40 °C, enabling the system to work as a typical electrical double-layer (EDL) capacitor. After prolonged floating of the AC/AC capacitor at 1.6 V and -40°C, the capacitance, equivalent series resistance and efficiency remain constant, demonstrating the absence of ageing related with side redox reactions at this temperature. Interestingly, when temperature is increased back to 24 °C, the redox behavior due to hydrogen storage reappears and the system behaves as a freshly prepared one.

A Dual-Buck–Boost AC/DC Converter for DC Nanogrid With Three Terminal Outputs

DEFF Research Database (Denmark)

Wu, Weimin; Wang, Houqing; Liu, Yuan

2017-01-01

Due to the widely used dc characterized loads and more distributed power generation sources, the dc nanogrid becomes more and more popular, and it is seen as an alternative to the ac grid. For safety considerations, the dc nanogrid should provide reliable grounding for the residential loads...... such as the low-voltage ac power system. There are three typical grounding configurations for a dc nanogrid: the united grounding, the unidirectional grounding, and the virtual isolated grounding. Each grounding configuration has its own specifications to ac/dc converters. In this paper, a dual-buck-boost ac/dc...... converter for use in the united-grounding-configuration-based dc nanogrid with three terminal outputs is proposed. The working principle of this converter is presented in detail through analyzing the equivalent circuits. Experiments are carried out to verify the theoretical analysis....

130 kV 130 A High voltage switching mode power supply for neutral beam plasma heating: design issues

International Nuclear Information System (INIS)

Ganuza, D.; Del Rio, J.M.; Garcia, I.; Garcia, F.; Garcia de Madinabeitia, P.; Perez, A.; Zabaleta, J.R.

2003-01-01

The company JEMA has designed and manufactured two High Voltage Switching Mode Power Supplies (HVSMPS), rated at 130 kV dc and 130 A, each of which will feed the accelerator grids of two Positive Ion Neutral Injector (PINI) loads, to be installed at the Joint European Torus (EFDA-JET facility located at Culham, UK). The solution designed by JEMA includes two matching transformers which adapt the 36 kV of the JET AC power distribution network to the required 670 V at the secondary side. Additionally, such transformers provide a 30 deg.phase shift which is required by a 30000 A 12 pulse thyristor rectifier. The obtained and stabilised 650 V feed 120 IGBT invertors, which operate at 2778 Hz with modulated square waveform. Each invertor feeds a High Insulation High Frequency Transformer. The 120 transformers corresponding to one power supply are arranged in three oil filled tanks and provide the main insulation from the low voltage to the high voltage side. The square waveform obtained at the secondary of each transformer is rectified by means of a diode bridge. The connection in series of the 120 diode bridges provides the required 130 kV d.c. at the output. In order to protect the load, a redundant solid state crowbar has been designed. Such short circuiting device is composed of 26 Light Triggered Thyristors (LTTs), connected in series. Electrical simulations have been carried out in order to ensure that the system complies with the requirements of high accuracy and adequate protection of the load. The critical design of the High Voltage-High Frequency Transformers has also required electrostatic simulations of the electric field distribution

Loss optimizing low power 50 Hz transformers intended for AC/DC standby power supplies

DEFF Research Database (Denmark)

Nielsen, Nils

2004-01-01

This paper presents the measured efficiency on selected low power conventional 50 Hz/230 V-AC transformers. The small transformers are intended for use in 1 W@5 V-DC series- or buck-regulated power supplies for standby purposes. The measured efficiency is compared for cheap off-the-self transformer...

Low-Power, Low-Voltage Analog to Digital ΣΔ

DEFF Research Database (Denmark)

Wismar, Ulrik Sørensen

2007-01-01

, and since long operation time is required, low supply voltage and low power consumption are of paramount importance. Consequently, various topologies have been compared to nd the most power ecient audio frequency modulator topology. Chapter 4 of this thesis compares power consumption of two of the most...... prevalent topologies, the single-loop modulator with integration in discrete time and the single-loop modulator with integration in continuous time. Both modulator topologies are with feedback, and all intermediate signals are in the voltage mode. Chapter 5 treats a modulator without feedback. Another...

Reduction of DC-link Capacitor in Case of Cascade Multilevel Converters by means of Reactive Power Control

DEFF Research Database (Denmark)

Gohil, Ghanshyamsinh Vijaysinh; Wang, Huai; Liserre, Marco

2014-01-01

A method to selectively control the amount of dc link voltage ripple by processing desired reactive power by a DC/DC converter in isolated AC/DC or AC/DC/AC system is proposed. The concept can reduce the dc link capacitors used for balancing the input and output power and thereby limiting...... the voltage ripple. It allows the use of smaller dc link capacitor and hence a longer lifetime and at the same time high power density and low cost can be achieved. The isolated DC/DC converter is controlled to process the desired reactive power in addition to the active power. The control system to achieve...

Modelling and Simulation of the SVC for Power System Flow Studies: Electrical Network in voltage drop

Directory of Open Access Journals (Sweden)

Narimen Aouzellag LAHAÇANI

2008-12-01

Full Text Available The goal of any Flexible AC Transmission Systems (FACTS devices study is to measure their impact on the state of the electrical networks into which they are introduced. Their principal function is to improve the static and dynamic properties of the electrical networks and that by increasing the margins of static and dynamic stability and to allow the power transit to the thermal limits of the lines.To study this impact, it is necessary to establish the state of the network (bus voltages and angles, powers injected and forwarded in the lines before and after the introduction of FACTS devices. This brings to calculate the powers transit by using an iterative method such as Newton-Raphson. Undertaking a calculation without the introduction of FACTS devices followed by a calculation with the modifications induced by the integration of FACTS devices into the network, makes it possible to compare the results obtained in both cases and thus assess the interest of the use of devices FACTS.