Academic literature on the topic 'Reactive power compensation'

<p>This Master's thesis investigates a new application for the matrix converter: Shunt reactive power compensation. The suggested Matrix Converter-based Reactive power Compensation (MCRC) device is composed of a matrix converter, which input is connected to the grid and an electric machine at the output of the converter. The reactive power flowing in or out of the grid can be regulated with the matrix converter by controlling the magnitude and/or phase angle of the current at the input of the converter. The matrix converter has no bulky DC link capacitor like traditional AC-DC-AC converters. The thought electric machine is a Permanent Magnet (PM) synchronous machine which is compact as well, yielding an overall compact device. The main focus of the thesis is to evaluate the reactive power range that the MCRC device can offer. The reactive power range depends mainly on the modulation of the matrix converter. Two different modulation techniques are studied: the indirect virtual space vector modulation and the three-vector-scheme. The indirect space vector modulation can provide or draw reactive power at the input of the matrix converter as long as there is an active power flow through the converter that is different from zero. For pure reactive power compensation the indirect space vector modulation cannot be used and the three-vector-scheme must be used instead. Both modulation techniques are presented in details as well as their reactive power compensation range. To verify the reactive power capabilities of the device, three different simulation models are built in MATLAB Simulink. The first simulation model represents the MCRC device with the matrix converter modulated with the indirect space vector modulation. The second model represents also the MCRC device with the matrix converter modulated with the three-vector-scheme. In both model the PM machine is represented by a simple equivalent circuit. Simulations done with both models show a good accordance between the theoretical analysis of the device and the experimental results. The last simulation model features a simplified version of the MCRC system connected to a grid where a symmetrical fault occurs. The MCRC proves to be efficient in re-establishing the voltage to its pre-fault value.</p>

Approved for public release; distribution is unlimited<br>A significant contributor to higher energy costs and reduced energy efficiency is the reactive power demand on the grid. Inductive power demand reduces power factor, increases energy losses during transmission, limits real power supplied to the consumer, and results in higher costs to the consumer. Compensating for a reactive power demand on the grid by providing reactive power support to the power distribution system creates energy efficiency gains and improves cost savings. One method of compensating for reactive power is by incorporating an energy management system (EMS) into the power distribution system. An EMS can monitor reactive power requirements on the grid and provide reactive power support at the point of common coupling (PCC) in the power distribution system in order to increase energy efficiency. The use of an EMS as a current source to achieve a unity power factor at the grid is demonstrated in this thesis. The power factor angle was determined using a zero-crossing detection algorithm. The appropriate amount of compensating reactive current was then injected into the system at the PCC and controlled using closed-loop current control. The process was simulated using Simulink and then validated in the laboratory using the actual EMS hardware.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010.<br>ENGLISH ABSTRACT: The use of power electronic converters provides a more efficient, accurate and dynamic solution to reactive compensation. In this thesis the application of power electronic converters to shunt reactive compensation will be discussed. In particular voltage dips and voltage unbalance are considered as both can be mitigated by means of shunt reactive compensation. A pre-existing uninterruptible power supply is adapted to operate as a shunt reactive compensator. The uninterruptible power supply consists of a 250 kVA three phase voltage source inverter. The modifications are limited to software and control algorithms that do not alter the normal operation of the uninterruptible power supply. Control algorithms are designed and discussed in detail. A typical double loop control strategy is implemented on the power electronic converter. The inner loop consists of a dead-beat current controller. The outer loop consists of three proportional and integral controllers controlling the DC-bus voltage, AC voltage and voltage unbalance respectively. Voltage dips and unbalance are compensated for using only reactive power. Focus is placed on producing a result can be used easily in practice.<br>AFRIKAANSE OPSOMMING: Drywings elektroniese omsetters wat gebruik word vir newe reaktiewe kompensasie lewer meer effektiewe, akkurate en dinamiese resultate. In hierdie tesis word die toepassing van drywings elektroniese omsetters vir newe reaktiewe kompensasie bespreek. Daar word meer spesifiek na spannings duike en spannings wanbalans gekyk aangesien albei met newe reaktiewe kompensasie verminder kan word. ’n Bestaande nood kragbron is aangepas om as n newe reaktiewe kompenseerder te funksioneer. Die nood kragbron bestaan hoofsaaklik uit ’n 250 kVA drie fase omsetter spanningsbron. Die aanpassings is beperk tot sagteware en beheer algoritmes wat nie die oorspronklike funksionaliteit van die nood krag bron beinvloed nie. Beheer algoritmes word ontwerp en deeglik bespreek. ’n Tipiese dubbel lus beheer strategie word op die drywings elektroniese omsetter toegepas. Die binnelus bestaan uit ’n voorspellende stroom beheerder. Die buite-lus bestaan uit drie proportioneel en integraal beheerders wat onderskeidelik die GS-bus spanning, WS spanning en spanning wanbalans reguleer. Spannings duike en wanbalans is verminder deur slegs reaktiewe drywing te gebruik. Die doel was ook om ’n prakties bruikbare resultaat te lewer.

This research work focuses on the reactive power compensation of the permanent magnet synchronous generator (PSG) in wind power plants. PSG feeds a fixed voltage dc grid through a rectifier bridge. In variable speed operation, the PSG will be able to build torque only in small speed range. This is due to the fixed magnet of the PSG. External reactive power compensation provides an attractive solution to overcome this problem. Different reactive power compensation configurations were examined. Statics synchronous series compensation and a shunt passive filter were chosen as a compensation method. Simulation and implementation of small wind power plant were performed. The wind power plant consists of the synchronous generator, inverter, rectifier, coupling transformers and shunt passive filter. The experimental results agree to the proposed theory and simulation results<br>Der Schwerpunkt meiner Promotion ist die Blindleistungskompensation bei einem permanenterregten Synchrongenerator. Der Synchrongenerator speist das Gleichsspannungsnetz über ein Gleichrichter. In der Drehzahlvariablen Betriebsverhalten können Nachteile auftreten. Die Folge ist, dass bei konstanter Gleichspannung und fester Erregung durch die Permanenterregung nur ein sehr kleiner Drehzahlbereich mit vernünftiger Drehmomentausbeute bedienbar ist. Ein möglicher Ausweg wäre eine variable Kompensationsspannung. Verschiedene Kompensationsverfahren wurden untersucht. Ein Series Active Filter und ein Shunt Passive-Filter wurden als Blindleistungskompensation gewählt. Im Rahmen meiner Dissertation beschäftige ich mich mit dem Aufbau und der Simulation einer Windkraftanlage. Diese besteht aus einem permanenterregten Synchrongenerator, einem Wechselrichrter, einem Gleichrichter, drei Transformatoren und einem passiven Filter. Das Versuchsergebnis zeigt, dass die Theorie mit der Simulation übereinstimmt

This thesis describes the development of a detailed set of step-by-step SVC system design procedures which allow manufacturers and operators to plan and develop optimum SVC systems for a given a.c. power transmission system. The validity of a typical svc system designed using the suggested procedures is investigated. The internationally recognised software package EMTP has been used as the primary Research tool, and principal features of this software, including those observed in the Research study also forms part of the discussion in the thesis. Previous conventional approaches to SVC simUlation have been restricted to simplified system models, and have only provided partial solutions to the design problem. In contrast, a detailed representation of three phase SVC systems using a time-domain approach is used in this research study in order to formulate a comprehensive design methodology. The SVC considered is for high voltage transmission applications, and is the TSC-TCR-FC type. A new optimisation program termed "OPTI-SVC" has also been developed to assist the SVC system design process. The system compensation limits must first be derived, and then for given equipment costs and system harmonic constraints, the program evaluates the optimum arrangement of the SVC primary system. Although certain simplifying assumptions are made and only those factors that can be taken into account analytically are considered, the program uses a worst case design philosophy in order to ensure acceptable performanceIn particular, Cost of the the program can minimise either the total svc system or the total harmonic voltage produced in the transmission system. In order to derive optimum control system settings, in particular for the SVC regulator, a structured trial and error approach has been developed. wi th the aid of the Astrom relay tuning technique, a good first estimation on optimum regulator settings for a given a.c. system condition can be obtained. The results are then systematically trimmed until a satisfactory system response is achieved. A three phase SVC system has been designed using the suggested approaches and applied to a generator fed transmission system. Realistic system data has been supplied by NEI Reyrolle Technology Limited. Simulated performance tests carried out demonstrate the correct functioning of the svc system against general accepted criteria, and hence the validity of the design procedure is established. As a primary research tool, the software EMTP has been proved to be very versatile although not user-friendly. Significant observations regarding the use of EMTP that are necessary to assist general users of the software package, are also revealed in the research study.

This research work is devoted to the analysis, design and development of the first medium power Current-Source Converter (CSC) based distribution-type Static Synchronous Compensator (D-STATCOM) with simplest converter topology and coupling transformer connection. The developed CSC-D-STATCOM includes a +/-750kVAr full-bridge CSC employing Selective Harmonic Elimination Method (SHEM), a 250kVAr low-pass input filter at 1kV voltage level, and a &amp<br>#916<br>/Y connected coupling transformer for connection to medium-voltage load bus. The power stage of CSC is composed of series connection of natural air-cooled high-voltage IGCT switched at 500 Hz for the elimination of four lowest current harmonic components (5th, 7th, 11th, 13th), and optimized fast recovery high voltage diode in each leg. Reactive power control is achieved by applying the phase shift angle control at fixed modulation index, which is implemented digitally on a DSP microcontroller. The developed system has been implemented for compensation of rapidly varying reactive power demand of coal mining excavators in Turkish Coal Enterprises. The field test results have shown that the proposed CSC D-STATCOM serves as a technologically new full substitute of conventional Voltage-Source Converter based D-STATCOM having complex transformer connections in view of relatively fast response in reactive power compensation, very low total demand distortion factors, complying with the IEEE Std. 519-1992 even for the weakest power systems, and acceptable efficacy figures.

This research work is devoted to the analysis, design and development of the Current-Source Converter (CSC) based distribution-type Static Synchronous Compensator (D-STATCOM) for low-voltage applications in reactive-power control in order to achieve i) faster transient response in reactive-power control, ii) lower current harmonic distortion, iii) lower power losses and iv) minimum storage elements in comparison with conventional solutions. The developed CSC-D-STATCOM includes a low-pass input filter and a three phase forced-commutated CSC which is composed of six insulated gate bipolar transistors (IGBT) with built-in series diodes. The analysis and the control of the CSC-D-STATCOM are carried out in dq-synchronous reference frame in order to obtain the reference current waveform which is to be generated by switching the IGBTs at 3kHz with the use of space vector modulation.