This thesis studies different aspects of Flexible AC Transmission System (FACTS) devices which are used to improve the power transfer capability and increase the controllability in electric power systems. In the thesis, different aspects on the usage and control of Dynamic Power Flow Controllers (DPFC) and related FACTS devices are studied. The DPFC is a combination of a Phase Shifting Transformer (PST) and a Thyristor Switched Series Capacitor (TSSC)/Thyristor Switched Series Reactor (TSSR). The thesis proposes and studies a new method, the Ideal Phase-Shifter (IPS) method, for selection and rating of Power Flow Controllers (PFC) in a power grid. The IPS method, which is based on steady-state calculations, is proposed as a first step in the design process for a PFC. The method uses the Power controller plane, introduced by Brochu et al in 1999. The IPS method extends the usage of decoupling methods in the Power controller plane to a power system of arbitrary size. The IPS method was in the thesis used to compare the ratings of different PFC:s required to improve the power transfer capability in two test systems. The studied devices were here the PST, the TSSC/TSSR and the DPFC. The thesis treats control of ideal Controlled Series Capacitors (CSC), TCSC, TSSC/TSSR, and DPFC. The goals of the FACTS controllers which are developed are Power Oscillation Damping (POD), fast power flow control, and transient stability improvement in the power system. New adaptive control strategies for POD and power flow control are proposed and studied in different models of power systems by time-domain simulations. A strategy for transient stability improvement is also proposed and studied. Additionally, different methods for study of Subsynchronous Resonance (SSR), which is associated with series compensation in power systems, are investigated. Here, four of the most common methods for frequency scanning to determine the electrical damping of subsynchronous oscillations in a power grid are studied. The study reveals significant differences of the electrical damping estimates of the studied standard methods when applied to a four-machine test system. / QC 20110819

The static synchronous series compensator (SSSC) is a series controller of Flexible AC Transmission Systems (FACTS). It can be controlled by Thyristors, it also has the ability of fast control adjustments and high frequency operation. Through impedance compensation, it is able to control the magnitude and directions of the real power flow in the transmission system. In order to achieve a fast and steady response for real power control in power systems, this thesis proposed a unified intelligent controller, which consists of RBFNN and GA for the SSSC to provide better control features for real power control in the dynamic operations of power systems. Finally, the simulation results of the proposed controllers is compared with the conventional proportional plus integral (PI) controllers to demonstrate the superiority and effectiveness of the unified intelligent controller.

In recent year, the awareness of environmental protection has made the power dispatch problem not necessarily economy-oriented. This thesis proposed the application of Particle Swarm Optimization (PSO) algorithm to solve the Unit Commitment (UC) problem for 24 hours with maximum profit in the power and carbon market. Optimal Power Flow (OPF) is used to solve the UC problem for the interconnected power network that is comprised of three independent areas to optimize the dispatching strategy. The UC problem must satisfy the constraints of the load demand, generating limits, minimum up/down time, ramp rate limits, and also the limits of power flow, buses voltage and transmission line capacity. The other objective of this thesis is to employ the Static Synchronous Series Compensator (SSSC) to integrate with OPF based on Equivalent Current Injection (ECI) power flow model, and install it at interconnected lines between each independent area controlling the power flow to reduce emission. In order to avoid the local optimality problem, this thesis proposed the utilization of the Multiple Particle Swarm Optimization (MPSO), which can quickly reach the optimal solution with a better performance and accuracy. The Independent Power Producer (IPP) can get the maximum profit with installed SSSC from the power and carbon trading with the calculation of power wheeling expense and carbon forecasting data. Furthermore, it can also assess the need of participating in the trading market or not.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-19T19:42:59Z No. of bitstreams: 1 danielsalomaosilva.pdf: 1815639 bytes, checksum: 1ac9991f1cfff85fc90c22c80f5ccaf4 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-04-20T13:12:33Z (GMT) No. of bitstreams: 1 danielsalomaosilva.pdf: 1815639 bytes, checksum: 1ac9991f1cfff85fc90c22c80f5ccaf4 (MD5) / Made available in DSpace on 2017-04-20T13:12:33Z (GMT). No. of bitstreams: 1 danielsalomaosilva.pdf: 1815639 bytes, checksum: 1ac9991f1cfff85fc90c22c80f5ccaf4 (MD5) Previous issue date: 2011-09-01 / O Compensador Série Síncrono Estático (SSSC – Static Synchronous Series Compensator) é um controlador FACTS (Flexible AC Transmission Systems) proposto na literatura para controlar o fluxo de potência pelas linhas de transmissão a corrente alternada. O SSSC é um compensador de potência reativa baseado em conversores eletrônicos de potência de alta capacidade ligados em série com as linhas de transmissão. Neste trabalho são utilizados conversores fonte de tensão (do inglês, VSC – Voltage Source Converters) multiníveis em cascata assimétrica, ligados ao sistema elétrico sem transformadores. O uso do SSSC aumenta as margens de estabilidade, a controlabilidade e a capacidade de transferência de potência de um sistema elétrico. Como a tensão sintetizada pelo SSSC está em quadratura com a corrente pela linha, pode-se utilizá-lo para emular uma reatância série, impor uma tensão ou injetar/absorver potência reativa em série com a linha de transmissão compensada. Neste trabalho são estudados cinco diferentes algoritmos para controlar as tensões geradas pelo SSSC. Resultados de simulações digitais são utilizados para verificar o desempenho de cada algoritmo implementado. / The Static Synchronous Series Compensator (SSSC) is a FACTS (Flexible AC Transmission Systems) controller proposed in the literature to control the power flow through the transmission power lines. The SSSC is a series connected compensator based on static power electronics converters. In this work, three single-phase asymmetrical cascaded multilevel voltage source converters (VSC) are used, connected to the electric power system without transformers. The use of SSSC increases the stability limit, the controllability and the transfer power capacity of electric power systems. Since the voltage synthesized by SSSC is in quadrature with line current, it can be used to emulate a series reactance, to synthesize a voltage or to inject/absorb reactive power in series with the compensated transmission line. Five different control algorithms are investigated to control the output voltages of the SSSC. Digital simulation results are used to demonstrate the effectiveness of each control strategy.

Orientador: Prof. Dr. Edmarcio Antonio Belati / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, 2017. / Neste trabalho analisou-se o desempenho de um Sistema Elétrico de Potência, quando alocados TCSC (do inglês, Thyristor Controlled Serie Compensator), e determinaram-se seus parâmetros ótimos de controle buscando maximizar a capacidade de transmissão total do sistema e melhorar o seu perfil de tensão, operando com suas variáveis dentro de limites pré-estabelecidos. Para tanto, foram modeladas variações do problema de Fluxo de Potência Ótimo Reativo (FPOR) e executadas em duas fases, identificadas como fase de alocação e fase de análise. Na fase de alocação foram realizadas simulações para analisar a alocação de diferentes quantidades de TCSC no sistema, com o objetivo de maximizar a capacidade de transmissão total e, por conseguinte, com base em um carregamento previsto na rede, foi determinada a quantidade mínima de dispositivos necessários para atender tal demanda. Em seguida, com o número de TCSC definido, os mesmos foram realocados com o objetivo de minimizar o desvio de tensão. Na fase de análise, os TCSC alocados na fase anterior foram mantidos com objetivo de otimizar o perfil de tensão, simulando variações nas cargas do sistema. Na fase de alocação, foi utilizada uma modelagem de Programação Não Linear Inteira Mista (PNLIM). Na fase de análise, o perfil de tensão foi otimizado por meio de uma modelagem de Programação Não Linear (PNL). Os resultados obtidos para os sistemas testes IEEE-14 e -118 barras demonstram os benefícios da utilização de TCSC na rede, pois possibilitou o aumento da carga total do sistema, e proporcionou uma melhora no perfil de tensão por meio do seu ajuste ótimo. / This work analyzed the electric power system performance when allocated TCSC (Thysristor Controlled Series Compensator) and determined their optimal control parameters in order to maximize the total transmission capability of the system and improve the voltage profile, operating within their pre-stablished limits. For this purpose, variations of Reactive Optimal Power Flow (FPOR) problems were modeled and executed in two phases, identified as phase of allocation and phase of analysis: In the allocation phase, simulations were performed to analyze the allocation of different amounts of TCSC in the system in order to maximize the total transmission capacity and, therefore, based on a predicted loading in the network, the minimum amount of devices was determined to attain such demand. Then, as the number of TCSC was defined, they were reallocated with the objective of minimizing the voltage deviation. In the analysis phase, the TCSC were maintained by considering the objective of optimizing the voltage profile and simulating loads variations of the system. In the allocation phase, a Mixed Integer Nonlinear Programming (MINLP) model was used. In the analysis phase, the voltage profile was optimized through a Nonlinear Programming (NLP) modeling. The results for the IEEE-14 and -118 test systems demonstrated the benefits of using the TCSC in the network because it allowed the increase of the total load of the system and provided an improvement in the voltage profile through its optimum adjustment.

Submitted by Morgana Silva (morgana_linhares@yahoo.com.br) on 2016-07-27T16:18:26Z No. of bitstreams: 1 arquivototal.pdf: 1682868 bytes, checksum: e6813f2f2930d8867270563d26fb878c (MD5) / Made available in DSpace on 2016-07-27T16:18:26Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1682868 bytes, checksum: e6813f2f2930d8867270563d26fb878c (MD5) Previous issue date: 2016-02-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This work proposes a repetitive-based control for series compensator with the objective of dynamically restore the voltage applied to sensitive and critical loads of power system. The control mitigates voltage sags while also minimize harmonic distortions. Its transfer function is simple to be realized and does not require any harmonic selective filters. The control system acts on sinusoid references and it is implemented in each phase independently. Another important aspect of the proposed system are the optimization strategies to minimize either the voltage injection or the active power injection. One of these strategies is to optimize the magnitude of the compensation voltage sag with the smallest voltage magnitude injection by the series compensator. For this purpose, the compensating voltage injected must be in phase with the voltage supply. Is possible to control the injection of the voltage compensation to minimize active power injection by the series compensator to compensate a voltage sag. To perform the voltage correction with minimum active power injection were developed analytical expressions for the magnitude and angle of the injected voltage. To implement theses strategies, an recursive least-squares algorithm is used to estimate the grid voltage. A laboratory-scale series compensator was developed to validate the method. Simulations and experimental results are presented and show the efficacy of the proposed method. / Este trabalho propõe um controle repetitivo para compensadores série com o objetivo de restaurar dinamicamente a tensão aplicada a cargas sensíveis e críticas de sistemas de energia. O controle pode mitigar afundamentos de tensão ao mesmo tempo que compensa distorções harmônicas. Sua função de transferência é simples de ser implementada e não requer qualquer filtro seletivo de harmônicos. O sistema de controle atua sobre as referências senoidais e deve ser implementado em cada fase independentemente. Um outro aspecto importante do trabalho são as estratégias de otimização para minimizar a tensão de compensação ou a potência ativa fornecida pelo compensador. Um destas estratégias é a otimização pela amplitude, em que a compensação do afundamento de tensão ocorre com a menor injeção de amplitude de tensão por parte do compensador série. Para isso, a tensão injetada pelo compensador deve estar em fase com a tensão da rede afundada. Pode-se, também, controlar a injeção da tensão de compensação para minimizar a potência ativa a ser injetada pelo compensador série para compensar um afundamento de tensão. Para realizar a correção com a mínima injeção de potência ativa utilizou-se expressões analíticas para obter a magnitude e o ângulo da tensão a ser injetada. Na implementação destas estratégias foi utilizado um algoritmo recursivo de mínimos quadrados para estimar a amplitude e fase da tensão da rede. Um sistema compensador série foi montado em laboratório para validar o método. As simulações e resultados experimentais são apresentados e constatam a eficácia do método proposto.

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<p>In this thesis, controllers for power oscillation damping, transient stability improvement and power flow control by means of a Controlled Series Compensator (CSC) and and a Dynamic Power Flow Controller (DPFC) are proposed. These devices belong to the group of power system components referred to as Flexible AC Transmission System (FACTS) devices. The developed controllers use only quantities measured locally at the FACTS device as inputs, thereby avoiding the risk of interrupted communications associated with the use of remote signals for control.</p><p>For power systems with one dominating, poorly damped inter-area power oscillation mode, it is shown that a simple generic system model can be used as a basis for damping- and power flow control design. The model for control of CSC includes two synchronous machine models representing the two grid areas participating in the oscillation and three reactance variables, representing the interconnecting transmission lines and the FACTS device. The model for control of DPFC is of the same type but it also includes the phase shift of the internal phase-shifting transformer of the DPFC.</p><p>The key parameters of the generic grid models are adaptively set during the controller operation by estimation from the step responses in the FACTS line power to the changes in the line series reactance inserted by the FACTS device. The power oscillation damping controller is based on a time-discrete, non-linear approach which aims to damp the power oscillations and set the desired power flow on the FACTS line by means of two step changes in the line reactance separated in time by half an oscillation cycle.</p><p>A verification of the proposed controllers was done by means of digital simulations using power system models of different complexities. The CSC and DPFC controllers were shown to significantly improve the small-signal- and transient stability in one four-machine system of a type commonly used to study inter-area oscillations. The CSC controller was also tested for 18 different contingencies in a 23-machine system, resulting in an improvement in both the system transient stability and the damping of the critical oscillation mode. </p>

This paper proposes two new topological arrangements consisting in connecting the AC power supply in series with two DC converters, one operating during the positive half-cycle and the other during the negative half cycle. It is noteworthy that these DC converters in series in a case are Buck EIE converters and on the other a buck. The results obtained with both arrangements are analyzed and compared. The control strategy is developed with the goal of imposing an AC voltage output within the limits imposed by the rules in order to mitigate the problems associated with Sags and Swells from the AC power supply . The principles of operation as well as the experimental and simulation results obtained in both steady and transient state are presented and validated for a 1kVA experimental prototype. Finally, some works still on progress related to this dissertation are presented, like the multilevel compensation and the three phase compensation. / Este trabalho propõe dois novos arranjos topológicos que consistem em se conectar a alimentação CA em série com dois conversores CC, um para operar durante o semiciclo positivo e o outro durante o semiciclo negativo. Vale ressaltar que estes conversores CC em série, em um caso são conversores Buck EIE e no outro um conversor Buck. Os resultados obtidos com ambos os arranjos são analisados e comparados. A estratégia de controle é desenvolvida com o intuito de impor uma tensão de saída CA dentro dos limites impostos pelas normas de forma a mitigar os problemas associados com Sags e Swells da rede de alimentação CA. Os princípios de operação, os resultados experimentais e de simulação obtidos, tanto em regime permanente quanto em condições transitórias de operação, são apresentados e validados para um protótipo experimental de 1kVA. Por fim apresentam-se os trabalhos relacionados a esta dissertação que ainda estão em desenvolvimento, que são a compensação em multinível e a compensação trifásica. / Mestre em Ciências

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