Reactive power support by photovoltaic farms has been under discussion in several countries. This kind of operation has been proposed because the photovoltaic farm converter is an expensive asset that is often used well below its power rating. This paper proposes a methodology for estimating the reactive power support capability and the associated technical cost of operating a photovoltaic installation as a STATCOM at nighttime. The technical cost is related to the need to buy active power from the grid to compensate for power losses. A precise estimation of this cost is of interest for both photovoltaic farm owners and grid operators to be able to evaluate the economic feasibility of this kind of operation. In order to illustrate the proposed methodology, a 1.5 MWp photovoltaic farm is considered. By evaluating the losses of each component (converter, tie reactor, filter and transformer), a reactive power support capability map integrating the technical cost for each point of operation is obtained. The analysis outlines key points to operate a PV farm as a STATCOM at nighttime: the system must include a blocking diode, the capability map is asymmetric, an operation with variable DC-link voltage is desirable and can lead to savings of up to 8.9 % in comparison with operation at fixed nominal DC-link voltage. / O suporte de potência reativa por fazendas solares fotovoltaicas está sob discussão em diversos países. Este tipo de operação foi proposta pois o conversor das fazendas solares é um equipamento de custo elevado que é usualmente utilizado abaixo de sua potência nominal. Este trabalho propõe uma metodologia para estimar a capabilidade de suporte de reativos e o custo técnico associado na operação de uma fazenda solar fotovoltaica como um STATCOM durante o período da noite. O custo técnico desta operação está associado à necessidade da compra de potência ativa da rede elétrica para suprir as perdas de energia para compensar as perdas nos equipamentos. Uma estimativa precisa deste custo técnico é de interesse tanto dos empreendedores que possuem fazendas fotovoltaicas como dos operadores da rede elétrica para que se avalie a viabilidade econômica deste tipo de operação. Para ilustrar a metodologia proposta, uma fazenda solar fotovoltaica de 1.5 MWp é considerada. Através da avaliação das perdas em cada componente (conversor, reator, filtro e transformador), um mapa de capabilidade de suporte de potência reativa é obtido integrando os custos técnicos para cada ponto de operação. A análise realizada neste trabalho destaca os pontos chave para a operação noturna de uma fazenda solar como STATCOM: o sistema deve incluir um diodo de bloqueio, o mapa de capabilidade é assimétrico, a operação com tensão do circuito CC é desejável e resulta em economia de energia de 8.9 % em comparação com operação com a operação em tensão nominal fixa do circuito CC.

This research and development work deals with the design methodology for Cascaded Multilevel Converter (CMC) based Transmission STATCOM (TSTATCOM) and development of a &plusmn / 12MVAR, 12kV line-to-line wye-connected, 11-level CMC. This CMC module constitutes the basic building block of TSTATCOM systems. Sizing of the CMC module, number of H-Bridges in each phase of the CMC, AC voltage rating of the CMC, the number of paralleled CMC modules in the T-STATCOM system, optimum value of series filter reactors and determination of busbar in the power grid to which the T-STATCOM system is going to be connected are also discussed in the thesis in view of IEEE Std.519-1992, current status of HV IGBT technology and the required reactive power variation range for the T-STATCOM application. In the field prototype of the CMC module, the AC voltages are approximated to sinusoidal waves by Selective Harmonic Elimination Method (SHEM) and by the use of an optimized series input filter reactor. The use of n number of HBs in each phase provides us n number of freedom in the application of SHEM. One of them is allocated to the fundamental component while n-1 is for the elimination of low order harmonics. Since n is chosen to five in the prototype system, 5th, 7th,11th and 13th harmonic components are successfully eliminated in the AC voltage waveforms of the CMC module. The equalization of DC link capacitor voltages is achieved according to Modified Selective Swapping (MSS) algorithm. MSS is applied every 400&mu / s period if needed to obtain a perfect equalization of DC link capacitor voltages at the expense of higher switching frequency and hence switching losses. In this research work, an L-shaped laminated bus has been designed and the HV IGBT driver circuit has been modified for optimum switching performance of HV IGBT modules in each HB circuit. The performances of the HB circuit and the resulting 11-level CMC module have been obtained not only in the laboratory but also in the field. Design works for HB and the CMC are based on MATLAB and PSCAD simulations. The laboratory and field performance of the HB circuit and CMC module is found to be satisfactory and quite consistent with the theoretical results and design objectives. In addition to these, 154 kV, &plusmn / 50MVAr T-STATCOM prototype has been designed, implemented and installed at Sincan Transformer Substation-Ankara primarily for the purposes of reactive power compensation and terminal voltage regulation. The T-STATCOM prototype is composed of five parallel operated CMC modules developed within the scope of this PhD thesis research work. The T-STATCOM configuration permits the operation of any number of CMC modules in the range from one to five for experimental purposes. The performance of this T-STATCOM system is also presented in this PhD thesis as a sample application.

The thesis use capacitors, Static Synchronous Compensator (STATCOM) and wind generator to get optimal voltage stability for twenty-four-hour dynamic load by compensating real/reactive power. In the thesis, Modified Orthogonal Particle Swarm Optimizer (MOPSO) is proposed to find the sitting and sizing of capacitors, STATCOM and wind generator, and integrate Equivalent Current Injection (ECI) algorithm to solve Optimal Power Flow (OPF) to achieve optimal voltage stability. The algorithm uses MOPSO to renew STATCOM and wind turbine sizing Gbest with multiple choices and Taguchi orthogonal array, which improves Particle Swarm Optimizer (PSO) without falling into the local optimal solution and searches optimal voltage stability of power system by load balancing equation and inequality constraints. Average Voltage Variation (AVV) and Average Voltage Drop Variation (AVDV) are proposed as objective function to calculate whole system voltage variations, and convergence test of MOPSO. The IEEE 33 Bus distribution system and Miaoli-Houlong distribution system were used for simulation to test the voltage control during peak and off-peak periods of Taipower. Compensation of real/reactive power was used to get optimal system voltage stability for each simulated case.

Due to development of industries, power factor and harmonic pollution have become serious concerns in the power system. This thesis presents an adaptive linear neuron (ADALINE) - based static synchronous compensator (STATCOM) to cope with power quality issues in the industrial power system. The targeted compensating current of the STATCOM is generated based on the so-called LMS algorithm, thus the compensated system current becomes balanced and active even in reactive, unbalanced or distorted loads. In this thesis, the STATCOM is realized by using a three-level neutral point-clamped (NPC) inverter with the in-phase level-shifted sinusoidal pulse width modulation (IPLSPWM). Theoretical analysis of ADALINE method is detailed and hardware implementation of STATCOM is conducted to validate effectiveness of the proposed approach.

Power quality issues of heavy industry, especially iron and steel plants, require special solutions. High levels of harmonic currents, unbalanced operation and light flicker arising from rapid fluctuations of active and reactive power demands are common problems in these plants. Almost all of these plants in Turkey are equipped with modern Static Var Compensator (SVC) Systems. In this thesis, alternative control strategies and flicker compensation system topologies are investigated and evaluated based on real-time field data and compared with the existing SVC systems. It is found out that the currently installed SVCs are not fully capable of solving the power quality issues of EAFs. This thesis is dedicated to detailed analysis, design, control, and simulation of TCR based SVC using instantaneous power theory, Three Phase Bridge Connected STATCOM and Delta Connected STATCOM. These 3 different types of compensators are modelled based on the similar installed capacities and their contribution to voltage quality and reactive power compensation are compared.

The most important advantages of Multilevel Inverters are the absence of a coupling transformer for medium voltage applications and low harmonic current content. In this way, relocatable and economical STATCOM systems can be realized. Complex control algorithms and the isolation problems of measurement devices and power supplies are the main challenging parts of this type of application. In this study, the design, realization, and the performance of a Voltage Source Type Cascaded Multilevel Converter Based STATCOM will be investigated in terms of digital computation, control hardware and the semiconductors devices commercially available in the market. This research work is fully supported by the Public Research Grant Committee (KAMAG) of TUBiTAK within the scope of National Power Quality Project of Turkey with the project No: 105G129.

This dissertation is to design the operation strategy and protective scheme of micro-grid systems with dispersed generation (DG). The industrial power system with cogeneration units and the distribution feeder with wind power generators were selected as the study micro-grids for computer simulation. The mathematical models of cogeneration units and wind generators were included in the computer simulation by considering the operation control modes of DGs. The micro-grid systems and the nearby utility networks were constructed to solve the power flows of the micro-grids with various operation scenarios of power generation and load demand. For the severe external fault contingencies, the micro-grids have to be isolated from the utility power system in time to prevent the tripping of critical loads and DGs. By considering the fault ride through capability of cogenerators and voltage tolerance curves of critical loads, the critical tripping time (CTT) of tie circuit breaker of the micro-grids was determined according to the transient stability analysis. To maintain the stable operation of the micro-grids after tie line tripping, the load shedding scheme was designed by applying the under frequency and under voltage relays to disconnect the proper amount of non-critical loads according to the governor responses of cogeneration units. For the micro-grid of distribution feeder with wind power generator, the STATCOM was used to provide adaptive reactive power compensation for the mitigation of voltage fluctuation due to the variation of wind speed and feeder loading. The STATCOM can also be applied for the support of terminal voltage of wind generator (WG) to enhance the transient response of the micro-grid. The CTT of tie circuit breaker was determined by considering the low voltage ride through (LVRT) capability and the critical fault cleaning time of WG. To achieve more effective islanding operation of the micro-grids, the artificial neural network (ANN) was applied to determine the proper timing for tie line tripping and the proper amount of load shedding by using the wind speed, feeder loading and the voltage of micro-grid system as the input of ANN. To verify the effectiveness of the proposed tie line tripping and load shedding scheme, different fault contingencies of the external utility network have been simulated by using the computer program for the transient stability analysis. It is found that the critical and voltage sensitive loads of the micro-grid can be maintained when the tie circuit breaker is activated to isolate the external fault in time and followed by the execution of load shedding scheme.

En esta Tesis de Maestría se presenta la investigación y el estudio detallado del comportamiento de los hornos de arco eléctrico como carga perturbadora en las redes eléctricas y los diferentes tipos de compensadores utilizados para la compensación del Flicker producido por dichos hornos. Como producto de dicho estudio se realiza el desarrollo completo de un modelo de compensador de Flicker tipo STATCOM en el programa SIMULINK de MATLAB. Se realizan mediciones en una Planta Industrial de producción de acero equipada con dichos hornos y se obtienen todas las perturbaciones introducidas en la red. Con los registros tomados en campo se verifica el efecto del compensador de Flicker diseñado. Se concluye que la rápida compensación de potencia provista por el STATCOM lo hace ideal para compensar el Flicker producido por los hornos de arco eléctrico.

El presente trabajo consiste en la modelación de un compensador estático para el control de generación distribuida con energías renovables. El objetivo es que esta modelación represente una microred básica en la cual se pueda observar el comportamiento de un pequeño medio de generación, como por ejemplo una micro turbina hidráulica, en un ambiente de generación distribuida. El modelo debe ser capaz de simular requerimientos violentos de potencia y, también, el control, como por ejemplo un compensador estático, diseñado para mitigar los efectos negativos que esto trae, como por ejemplo problemas de frecuencia y voltaje. Se busca obtener un modelo sencillo e implementarlo con el software Matlab a través de su herramienta de simulación con entorno gráfico Simulink con la ayuda de las herramientas disponibles en el Toolbox SimPowerSystems. Con el fin de contextualizar los conceptos de generación distribuida, energías renovables y equipos de compensación estáticos, se hace una revisión del contexto mundial sobre el problema energético y las medidas que se han adoptado en otros países como la liberalización del mercado energético para la integración de generación distribuida. Se presentan las alternativas comunes que se utilizan hoy en día para el control de generación desde las más sencillas hasta las más elaboradas. También se revisan los distintos tipos de equipos de compensación FACTS, en particular los equipos de compensación de potencia activa y los sistemas de almacenamiento de energía, existentes en el mercado. Para poder introducir el modelo en Matlab-Simulink, se presentan algunos esquemas de control típicos para equipos STATCOM y SVC en los que está basada la modelación y los bloques que conforman el sistema de control simulado. El modelo diseñado, fue ajustado para trabajar en una microred en presencia de una carga resistiva y una carga inductiva que es conectada a la microred mediante un interruptor trifásico. La carga inductiva fue conectada 0.5 segundos después del inicio de la simulación provocando una baja de tensión en la línea hasta los 0.92[pu] que es restablecida hasta su valor unitario en aproximadamente 0.16[s] por la acción del dispositivo modelado. Se concluye que el esquema de STATCOM basado en inversores VSI presentan características operativas atractivas para la generación distribuida dada su rapidez de respuesta y la posibilidad de aportar su capacidad nominal en condiciones severas de funcionamiento.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / O constante aumento da demanda energÃtica de um paÃs à sempre alvo de preocupaÃÃo para os operadores de sistemas. Isto implica diretamente no aumento do grau de exigÃncia dos novos procedimentos de rede. Dentre outros tipos de exigÃncia, o ONS (Operador Nacional do Sistema ElÃtrico), solicita, por exemplo que a tensÃo contratada seja controlada pelo solicitante em nÃveis entre 0,95 e 1,05 p.u. (230kV). Quando existem no sistema, centrais eÃlicas de geraÃÃo baseados em mÃquina de induÃÃo duplamente alimentada, esta preocupaÃÃo à ainda maior. Isto porque este tipo de mÃquina, possui seu estator conectado diretamente à rede, tendo, por sua vez, maior sensibilidade a oscilaÃÃes de tensÃo. Sabendo disto, nos Ãltimos anos a eletrÃnica de potÃncia tem estado cada vez mais presente no setor elÃtrico, a exemplo do Static Synchronous Compensator, o STATCOM, que atravÃs do gerenciamento da potÃncia reativa, pode melhorar e muito a ponto de atà anular efeitos causados por oscilaÃÃo de tensÃo. Visando uma aplicaÃÃo semelhante a esta, este trabalho investiga a operaÃÃo conjunta entre o STATCOM e centrais eÃlicas no que diz respeito ao suporte à tensÃo do sistema no qual esta incorporaÃÃo à conectada. Decidiu-se basear o estudo num cenÃrio existente no nordeste brasileiro pois desta forma, à possÃvel ter noÃÃo dos reais efeitos que um STATCOM pode trazer, positivamente, ao sistema. Este trabalho apresenta uma tÃcnica para dimensionamento do STATCOM bem como discussÃes gerais sobre possÃveis desvantagens desta aplicaÃÃo. AlÃm disso, à utilizado dois softwares para elaboraÃÃo dos resultados: MatLab, que atravÃs de scripts calcula todos pontos de interesse para a anÃlise; e ANAREDE, para verificaÃÃo e comparaÃÃo dos resultados obtidos atravÃs do primeiro software. E ainda, este estudo mostra que o script desenvolvido à capaz de designar resultados que se aproximam bastante das respostas do ANAREDE, que sÃo conferidos atravÃs do comportamento do erro das respostas de ambos os programas. Por fim, com objetivo de mostrar o funcionamento dos modos de operaÃÃo do STATCOM conectado ao sistema, sÃo explicitados resultados retirados pelo software PSCAD para um cenÃrio diferente do estudado. / The constant increase in energy demand of a country is always the target of concern for system operators. This implies directly in increasing degree of requirement of the new grid procedures. Among other types of requirement, the ONS (National Electricity System Operator), requests, for example that the tension is controlled by contractor requestor is always controlled between 0.95 and 1.05 p.u.. When there are in the system, wind generation plants based on doubly fed induction machine, this concern is even greater. This is because this type of machine, has its stator connected directly to the network, and in turn more sensitive to voltage fluctuations. Knowing this, in recent years the power electronics is being increasingly present in the electricity sector to mitigate these failures, the example of Static Synchronous Compensator, the STATCOM, that through the management of reactive power, can improve and the point until oscillation effects of annular tension. Targeting an application similar to this, this work brings an idea of STATCOM operating in conjunction with wind farms on serviceability of the desired bar voltage. It was decided to base the study on existing scenario in northeastern Brazil because this way, you can get a sense of the real effects of a STATCOM can bring, positively, to the system. This paper presents a technique for STATCOM sizing as well as general discussions about possible disadvantages of this application. In addition, is used two softwares for preparation of results: MatLab, which through scripts calculates all points of interest for analysis; and ANAREDE, for verification and comparison of the results obtained through the first software .