No description available.

Transient stability of electric energy grids is defined as the ability of the power system to remain in synchronism during large disturbances. If the grid is not equipped with controllers capable of transiently stabilizing system dynamics, large disturbances could cause protection to trigger disconnecting the equipment and leading further to cascading system-wide blackouts. Today’s practice of tuning controllers generally does not guarantee a transiently stable response because it does not use a model for representing system-wide dynamic interactions. To overcome this problem, in this thesis we propose a new systems modeling and control design for provable transient stabilization of power systems against a given set of disturbances. Of particular interest are fast power-electronically-controlled Flexible Alternating Current Transmission System (FACTS) devices which have become a new major option for achieving transient stabilization. The first major contribution of this thesis is a framework for modeling of general interconnected power systems for very fast transient stabilization using FACTS devices. We recognize that a dynamic model for transient stabilization of power systems has to capture fast electromagnetic dynamics of the transmission grid and FACTS, in addition to the commonly-modeled generator dynamics. To meet this need, a nonlinear dynamic model of general interconnected electric power systems is derived using time-varying phasors associated with states of all dynamic components. The second major contribution of this thesis is a two-level approach to modeling and control which exploits the unique network structure and enables preserving only relevant dynamics in the nonlinear system model. This approach is fundamentally based on separating: a) internal dynamics model for ensuring stable local response of components; b) system-level model in terms of interaction variables for ensuring stability of the system when the components are interconnected. The two levels can be controlled separately which minimizes the need for communication between controllers. Both distributed and cooperative ectropy-based controllers are proposed to control the interaction-level of system dynamics. Proof of concept simulations are presented to illustrate and compare the promising performance of the derived controllers. Some of the most advanced FACTS industry installations are modeled and further generalized using our approach.

Due to the high energy consumption demand and restrictions in the installation of new transmission lines, using Flexible AC Transmission System (FACTS) devices is inevitable. In power system analysis, transferring high-quality power is essential. In fact, one of the important factors that has a special role in terms of efficiency and operation is maximum power transfer capability. FACTS devices are used for controlling the voltage, stability, power flow and security of transmission lines. However, it is necessary to find the optimal location for these devices in power networks. Many optimization techniques have been deployed to find the optimal location for FACTS devices in power networks. There are several varieties of FACTS devices with different characteristics that are used for different purposes. The imperialist competitive algorithm (ICA) is a recently developed optimization technique that is used widely in power systems. This study presents an approach to find the optimal location and size of FACTS devices in power networks using the imperialist competitive algorithm technique. This technique is based on human social evolution. ICA technique is a new heuristic algorithm for global optimization searches that is based on the concept of imperialistic competition. This algorithm is used for mathematical issues; it can be categorized on the same level as Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) techniques. Also, in this study, the enhancement of voltage profile, stability and loss reduction and increasing of load-ability were investigated and carried out. In this case, to apply FACTS devices in power networks, the MATLAB program was used. Indeed, in this program all power network parameters were defined and analysed. IEEE 30-bus and IEEE 68-bus with 16 machine systems are used as a case study. All the simulation results, including voltage profile improvement and convergence characteristics, have been illustrated. The results show the advantages of the imperialist competitive algorithm technique over the conventional approaches.

No description available.

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O TCSC é um dos compensadores dinâmicos mais eficazes empregados em Sistemas Elétricos de Potência, pois, oferece um ajuste flexível, de forma rápida e confiável, possibilitando a aplicação de teorias avançadas no seu controle. Estes dispositivos podem desempenhar funções importantes para a operação e o controle do sistema, trazendo inúmeros benefícios. Devido aos benefícios que o uso deste dispositivo oferece, uma grande quantidade de trabalhos vem sendo desenvolvidos com o intuito de sintetizar leis de controle para o mesmo. Porém, a maioria destes trabalhos é fundamentado em técnicas de controle clássico, isto é, projetando leis de controle baseado em sistemas linearizados e para pontos específicos da operação. Estas técnicas de análise entretanto, não garantem que para perturbações que levam o sistema para pontos distantes daqueles usados no projeto do controlador, a atuação do controlador seja eficaz e contribua assim para a estabilização do sistema. Visando o estudo mais aprofundado dos fenômenos que ocorrem nos sistemas físicos, modelos não lineares vêm sendo empregados, e as técnicas de projeto de controladores baseadas nesses modelos, são cada vez mais desenvolvidas. Neste trabalho será empregada a técnica de controle não linear baseada na Função Energia Generalizada de Controle para síntese de leis de controles estabilizantes para os dispositivos TCSC considerando, na modelagem, as perdas do sistema de transmissão. Esta técnica foi desenvolvida recentemente por SILVA et al. (2009), onde as ideias de Função de Lyapunov de Controle para uma classe maior de problemas foram desenvolvidas. Além de permitir o projeto do controlador, a técnica fornece estimativas da região de estabilidade do sistema e, portanto, podendo subsidiar a avaliação sistemática da contribuição do controlador na estabilidade transitória. / The TCSC is one of the most effective dynamic compensators used in electric power systems, offering a flexible adjustment, quickly and reliably, enabling the application of advanced theories in their control. These devices can play important roles for the operation and control of the networks, bringing many benefits. Because of the beneficial use of these devices a large amount of work has been developed in order to synthesize their control laws. However most of these studies are based on the classical control techniques, designing control laws based on linearized systems at specific operating points. However, these techniques do not guarantee that system disturbances which lead to operating points far away from those used for the controller design, the performance of the controller will be effective contributing to the system stabilization. Aiming to further studies and understanding of the physical phenomena occurring in the real world systems, nonlinear models have being employed in the controller design and techniques based on these methodologies have been proposed as never. In this work the technique of nonlinear control based on the Generalized Control Energy Function, for synthesis of control laws, which stabilize the TCSC devices considering the losses in the system transmission lines are employed. These techniques were recently developed by SILVA et al. (2009), and they extend the ideas of Control Lyapunov Function for a larger class of problems. Besides allowing the controller design, the technique provides estimates of the system stability region and therefore can support the systematic evaluation of the contribution to the transient stability controller.

O TCSC é um dos compensadores dinâmicos mais eficazes empregados em Sistemas Elétricos de Potência, pois, oferece um ajuste flexível, de forma rápida e confiável, possibilitando a aplicação de teorias avançadas no seu controle. Estes dispositivos podem desempenhar funções importantes para a operação e o controle do sistema, trazendo inúmeros benefícios. Devido aos benefícios que o uso deste dispositivo oferece, uma grande quantidade de trabalhos vem sendo desenvolvidos com o intuito de sintetizar leis de controle para o mesmo. Porém, a maioria destes trabalhos é fundamentado em técnicas de controle clássico, isto é, projetando leis de controle baseado em sistemas linearizados e para pontos específicos da operação. Estas técnicas de análise entretanto, não garantem que para perturbações que levam o sistema para pontos distantes daqueles usados no projeto do controlador, a atuação do controlador seja eficaz e contribua assim para a estabilização do sistema. Visando o estudo mais aprofundado dos fenômenos que ocorrem nos sistemas físicos, modelos não lineares vêm sendo empregados, e as técnicas de projeto de controladores baseadas nesses modelos, são cada vez mais desenvolvidas. Neste trabalho será empregada a técnica de controle não linear baseada na Função Energia Generalizada de Controle para síntese de leis de controles estabilizantes para os dispositivos TCSC considerando, na modelagem, as perdas do sistema de transmissão. Esta técnica foi desenvolvida recentemente por SILVA et al. (2009), onde as ideias de Função de Lyapunov de Controle para uma classe maior de problemas foram desenvolvidas. Além de permitir o projeto do controlador, a técnica fornece estimativas da região de estabilidade do sistema e, portanto, podendo subsidiar a avaliação sistemática da contribuição do controlador na estabilidade transitória. / The TCSC is one of the most effective dynamic compensators used in electric power systems, offering a flexible adjustment, quickly and reliably, enabling the application of advanced theories in their control. These devices can play important roles for the operation and control of the networks, bringing many benefits. Because of the beneficial use of these devices a large amount of work has been developed in order to synthesize their control laws. However most of these studies are based on the classical control techniques, designing control laws based on linearized systems at specific operating points. However, these techniques do not guarantee that system disturbances which lead to operating points far away from those used for the controller design, the performance of the controller will be effective contributing to the system stabilization. Aiming to further studies and understanding of the physical phenomena occurring in the real world systems, nonlinear models have being employed in the controller design and techniques based on these methodologies have been proposed as never. In this work the technique of nonlinear control based on the Generalized Control Energy Function, for synthesis of control laws, which stabilize the TCSC devices considering the losses in the system transmission lines are employed. These techniques were recently developed by SILVA et al. (2009), and they extend the ideas of Control Lyapunov Function for a larger class of problems. Besides allowing the controller design, the technique provides estimates of the system stability region and therefore can support the systematic evaluation of the contribution to the transient stability controller.

Este trabalho apresenta um método sistemático para projeto de controladores suplementares para um tipo de dispositivo FACTS (o modelo TCSC) para o amortecimento de oscilações em sistemas elétricos de potência. Adota-se uma metodologia previamente desenvolvida para projeto de apenas controladores de tipo PSS. Tal metodologia é fundamentada na teoria de controle robusto e estruturada na forma de desigualdades matriciais lineares (LMIs). A modelagem politópica é utilizada para tratar a robustez dos controladores frente às variações no ponto de operação do sistema. O fator de amortecimento mínimo para os modos de resposta do sistema em malha fechada é especificado como índice de desempenho mínimo a ser satisfeito na fase de projeto. Os controladores propostos possuem uma estrutura de realimentação dinâmica de saída e utilizam sinais medidos localmente como entrada de controle. O projeto dos controladores propostos é realizado de duas maneiras diferentes: (i) projeto simultâneo e coordenado de controladores de tipo PSS e controlador suplementar de dispositivo TCSC para amortecimento tanto de modos locais, quanto de modos inter-área e; (ii) projeto de controlador suplementar para apenas um dispositivo TCSC operando no sistema com a finalidade de amortecer modos inter-área pouco amortecidos e instáveis. No primeiro caso, a descentralização dos controladores é garantida através da imposição de uma estrutura bloco-diagonal para as variáveis matriciais presentes na formulação do problema de controle. No segundo caso, este trabalho propõe uma extensão da metodologia de projeto utilizada no caso anterior ao combiná-la com uma técnica de redução da ordem de modelo do controlador. A análise de desempenho dos controladores em malha fechada é realizada através de análise modal e simulações não-lineares em dois sistemas testes. O primeiro deles é constituído por 10 barras e 4 geradores e o segundo sistema teste apresenta 40 barras e 10 geradores. / This work proposes a systematic method for the design of supplementary controllers for a type of FACTS device (the TCSC device model) to damp oscillations in electric power systems. It is adopted a technique previously presented to design only PSS-type damping controllers. The method is based on a robust control technique structured in the form of linear matrix inequalities (LMIs). The polytopic model is used to guarantee the robustness of the controllers with respect to the variations in the operating points of the system. The minimum damping ratio is used in the design stage as performance index for the closed loop system. The proposed controllers are based on dynamic output feedback and uses only local measurements as input signals. The design of the proposed controllers is realized in two different cases: (i) a simultaneous coordinated design of PSS-type controllers and TCSC supplementary controller to damp both local and interarea oscillations and; (ii) design of a supplementary controller for a FACTS device only to damp poorly damped and unstable inter-area oscillations. In the first case, a decentralized structure of the controllers is guaranteed by adoption of a block-diagonal strutucture to the matricial variables of the control problem. In the second case, this work proposes a extension of the previously methodology by combining it with a model order reduction technique. Performance analyses of the closed loop system were carried out by means of modal analysis and nonlinear simulations in two test systems. The first one is constituted by 10 buses and 4 generators and the other test system is constituted by 40 buses and 10 generators.

Este trabalho apresenta um método sistemático para projeto de controladores suplementares para um tipo de dispositivo FACTS (o modelo TCSC) para o amortecimento de oscilações em sistemas elétricos de potência. Adota-se uma metodologia previamente desenvolvida para projeto de apenas controladores de tipo PSS. Tal metodologia é fundamentada na teoria de controle robusto e estruturada na forma de desigualdades matriciais lineares (LMIs). A modelagem politópica é utilizada para tratar a robustez dos controladores frente às variações no ponto de operação do sistema. O fator de amortecimento mínimo para os modos de resposta do sistema em malha fechada é especificado como índice de desempenho mínimo a ser satisfeito na fase de projeto. Os controladores propostos possuem uma estrutura de realimentação dinâmica de saída e utilizam sinais medidos localmente como entrada de controle. O projeto dos controladores propostos é realizado de duas maneiras diferentes: (i) projeto simultâneo e coordenado de controladores de tipo PSS e controlador suplementar de dispositivo TCSC para amortecimento tanto de modos locais, quanto de modos inter-área e; (ii) projeto de controlador suplementar para apenas um dispositivo TCSC operando no sistema com a finalidade de amortecer modos inter-área pouco amortecidos e instáveis. No primeiro caso, a descentralização dos controladores é garantida através da imposição de uma estrutura bloco-diagonal para as variáveis matriciais presentes na formulação do problema de controle. No segundo caso, este trabalho propõe uma extensão da metodologia de projeto utilizada no caso anterior ao combiná-la com uma técnica de redução da ordem de modelo do controlador. A análise de desempenho dos controladores em malha fechada é realizada através de análise modal e simulações não-lineares em dois sistemas testes. O primeiro deles é constituído por 10 barras e 4 geradores e o segundo sistema teste apresenta 40 barras e 10 geradores. / This work proposes a systematic method for the design of supplementary controllers for a type of FACTS device (the TCSC device model) to damp oscillations in electric power systems. It is adopted a technique previously presented to design only PSS-type damping controllers. The method is based on a robust control technique structured in the form of linear matrix inequalities (LMIs). The polytopic model is used to guarantee the robustness of the controllers with respect to the variations in the operating points of the system. The minimum damping ratio is used in the design stage as performance index for the closed loop system. The proposed controllers are based on dynamic output feedback and uses only local measurements as input signals. The design of the proposed controllers is realized in two different cases: (i) a simultaneous coordinated design of PSS-type controllers and TCSC supplementary controller to damp both local and interarea oscillations and; (ii) design of a supplementary controller for a FACTS device only to damp poorly damped and unstable inter-area oscillations. In the first case, a decentralized structure of the controllers is guaranteed by adoption of a block-diagonal strutucture to the matricial variables of the control problem. In the second case, this work proposes a extension of the previously methodology by combining it with a model order reduction technique. Performance analyses of the closed loop system were carried out by means of modal analysis and nonlinear simulations in two test systems. The first one is constituted by 10 buses and 4 generators and the other test system is constituted by 40 buses and 10 generators.

This thesis is devoted to the development of new approaches for control coordination of PSSs (power system stabilisers) and FACTS (flexible alternating current transmission system) devices for achieving and enhancing small-disturbance stability in multi-machine power systems. The key objectives of the research reported in the thesis are, through optimal control coordination of PSSs and/or FACTS devices, those of maintaining satisfactory power oscillation damping and secure system operation when the power system is subject to persisting disturbances in the form of load demand fluctuations and switching control. Although occurring less frequently, fault disturbances are also considered in the assessment of the control coordination performance. Based on the constrained optimisation method in which the eigenvalue-based objective function is minimised to identify the optimal parameters of power system damping controllers, the thesis first develops a procedure for designing the control coordination of PSSs and FACTS devices controllers. The eigenvalue-eigenvector equations associated with the selected electromechanical modes form a set of equality constraints in the optimisation. The key advance of the procedure is that there is no need for any special software system for eigenvalue calculations, and the use of sparse Jacobian matrix for forming the eigenvalue-eigenvector equations leads to the sparsity formulation which is essential for large power systems. Inequality constraints include those for imposing bounds on the controller parameters. Constraints which guarantee that the modes are distinct ones are derived and incorporated in the control coordination formulation, using the property that eigenvectors associated with distinct modes are linearly independent. The robustness of the controllers is achieved very directly through extending the sets of equality constraints and inequality constraints in relation to selected eigenvalues and eigenvectors associated with the state matrices of power systems with loading conditions and/or network configurations different from that of the base case. On recognising that the fixed-parameter controllers, even when designed with optimal control coordination, have an inherent limitation which precludes optimal system damping for each and every possible system operating condition, the second part of ii the research has a focus on adaptive control techniques and their applications to power system controllers. In this context, the thesis reports the development of a new design procedure for online control coordination which leads to adaptive PSSs and/or supplementary damping controllers (SDCs) of FACTS devices for enhancing the stability of the electromechanical modes in a multi-machine power system. The controller parameters are adaptive to the changes in system operating condition and/or configuration. Central to the design is the use of a neural network synthesised to give in its output layer the optimal controller parameters adaptive to system operating condition and configuration. A novel feature of the neural adaptive controller is that of representing the system configuration by a reduced nodal impedance matrix which is input to the neural network.