SaskPower has two separate systems, namely the North and the South systems. The South system contains SaskPower major generation and system load. The North system load is located relatively far from its generation (200 to 300 km). The North system is considered, therefore, to be electrically weaker than the South system. Recently there has been an interest in connecting the two systems to improve the security, stability and reliability of the integrated system. Grid interconnections, however, especially between weak and strong systems, often result in the arising of low-frequency oscillations between the newly connected areas. These oscillations that are termed “inter-area oscillations” exhibit, generally poor damping and can severely restrict system operations by requiring the curtailment of electric power transfers level as an operational measure. There are two options for SaskPower North and South systems interconnection, namely HVAC and HVDC interconnections (tie-lines). This thesis reports the results of digital timedomain simulation studies carried out to investigate the dynamic performance of a proposed 260 km, 138 kV double-circuit HVAC tie-line incorporating a hybrid three-phase Thyristor- Controlled Series Capacitor (TCSC) compensation scheme that would connect the SaskPower North and South systems. The potential problems that might arise due to such an interconnection, namely power flow control and low-frequency oscillations are studied and quantified and a feasible solution is proposed. In this context, the effectiveness of the TCSC compensation scheme in damping power system oscillations in the tie-line is investigated. Time-domain simulations were conducted on the benchmark model using the ElectroMagnetic Transients Program (EMTP-RV). The results of the investigations demonstrate that the proposed HVAC link that incorporates a TCSC compensation scheme is effective in mitigating the low-frequency oscillations between the North and South systems for different system contingencies and operating conditions.

The objective of this work is to design a damping controller for a thyristor controlled series capacitor (TCSC) to damp robustly inter-area oscillations in power systems with an immunity against sub-synchronous resonance (SSR) oscillations which may lead to torsional oscillations. The new control strategy has two main loops; an SSR mitigation loop and a bang-bang loop, the latter is designed with the aim of damping inter-area oscillations with a settling time 8-10 sec. The appropriate selection of the bang-bang series compensation component, ∆KC, is addressed by considering the Eigen analysis of the generators’ shafts and an impedance scan of the series compensated line for different compensation levels. The SSR mitigation loop is designed with the aim of providing a fine tune control signal to be added to the main value of the inserted series compensation (KC), to damp SSR oscillations and related torsional mode of oscillations. To address this issue, a new observer-based multiple model adaptive control algorithm is designed to control a multi-stage TCSC. The SSR modelling challenges associated with the load dynamics and with the insertion of the series compensation into the transmission system are overcome by a fine tuning control loop, which adjusts the resultant series compensation (KC). Considering the integration and coordination of oscillation damping and distance protection in the transmission system, a new adaptive technique must be designed to control the distance relay (DR) to prevent its mal operation (during the damping process). The new strategy is illustrated through an 11-bus 4-machine 2-area benchmark power system. The performance and advantages of the new algorithm are validated using time domain simulation via PSCAD software.

ABSTRACT Wind energy is among the fastest growing renewable energy technologies in the world that has been increasing by about 30% a year globally. Wind energy has proven to be a clean, abundant and completely renewable source of energy. Owing to the rapidly increasing use of wind power, the aspect of integrating high level of penetrations wind power into the grid is becoming more and more of reality. Examples of large wind farms in the United States are the 781.5 MW Roscoe wind farm in Texas, the 735.5 MW Horse Hollow Wind Energy Center in Taylor and Nolan County, Texas, the 845 MW Shepherds Flat wind farm in Oregon and the 1550 MW Alta wind farm being developed in California. As most large wind farms in North America employ Doubly-fed Induction Generator (DFIG) wind turbines, their voltage-sourced converter-based back-to-backs offer independent control of the real and reactive power. The use of these control capabilities have been recently proposed for damping power swings, inter-area oscillations as well as subsynchronous resonance. There is, however, a question that is always associated with the use of voltage-sourced converter -based back-to-back wind farms for damping power system oscillations: what happens when there is no wind? The keyword to the answer is “combined”. The potential benefit of using these types of wind farms for damping power system oscillations should always be combined with conventional damping devices (power system stabilizers, thyristor controlled series capacitor, static synchronous series compensator, high voltage dc systems, etc.). This thesis reports the results of digital time-domain simulation studies that are carried out to investigate the potential use of supplemental controls of DFIG-based wind farms combined with a phase imbalanced hybrid series capacitive compensation scheme for damping power system oscillations. The thesis also addresses the recent concern over the case of large share of wind power generation which results in reducing the total inertia of the synchronous generators and degrading the system transient stability. In this regards, the results of the investigations have shown that in such a case; properly designed supplemental controllers for the wind farm converters could be an asset in improving the system transient stability rather than degrading it. Time-domain simulations are conducted on a benchmark model using the ElectroMagnetic Transients program (EMTP-RV).

This thesis has proposed two types of real time System Integrity Protection Schemes(SIPS) using Emergency Single Machine Equivalent (E-SIME) and Model PredictiveControl (MPC) approaches respectively. They are aiming to resolve the transientstability problems in power systems. Synchronous measurements, fast communicationnetwork and FACTS are deployed in the two SIPSs. The Thyristor Controlled SeriesCompensation (TCSC) is applied as the control action in both SIPSs.In the E-SIME based SIPS, the SIME approach is used to evaluate the transient stabilityof the system and then a decision is made about the control actions needed to stabilizethe system. During emergency conditions, a fast response time is very important andthis requires a security guideline to be used in the decision making process. Theguideline is developed by analyzing offline multiple fault scenarios using an automaticlearning approach. This ensures appropriate control actions can be performed withoutcompromising the response time required on a real system.The MPC based SIPS optimizes the control action at every discrete time instant byselecting the control action that leads to the minimized cost function value. Automaticlearning (AL) is utilized to predict power system dynamics by assuming each controlaction has been taken. Furthermore, a feature selection technique, that chooses themost relevant variables, is used to improve the performance of the AL prediction. Themodel predictive control (MPC) technique is performed every discrete time interval, sothe optimal control action is always selected.Two types of SIPS are tested and verified in the benchmark systems. Simulation resultsshow they can effectively protect the system from loss of synchronism in the aftermathof a large disturbance. This thesis also compares the two SIPSs and concludes thebenefits and shortcomings of each approach.

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.

Made available in DSpace on 2014-06-11T19:22:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-11-19Bitstream added on 2014-06-13T18:49:32Z : No. of bitstreams: 1 menezes_mm_me_ilha.pdf: 769292 bytes, checksum: 4b80be15a6104228fa9612312498644f (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho apresenta estudos referentes à estabilidade a pequenas perturbações do SEP, considerando a atuação de FACTS para o amortecimento das oscilações eletromecânicas de baixa frequência. São abordados os dispositivos FACTS TCSC (Thyristor Controlled Series Capacitor) e o SSSC (Static Synchronous Series Compensator). É realizada a representação e modelagem dos dispositivos FACTS no SEP inserindo no Modelo Sensibilidade de Potência. Para melhorar o desempenho do SEP no que se refere à estabilidade a pequenas perturbações, controladores suplementares são propostos para aumentar o desempenho dos dispositivos TCSC e SSSC, introduzindo o amortecimento necessário ao SEP. Adicionam-se os controladores suplementares POD no modelo modificado para os dispositivos TCSC e SSSC para verificar sua atuação. Para encontrar a melhor localização para instalação dos dispositivos é usado a teoria dos resíduos. Esta mesma teoria é usada também para o ajuste dos parâmetros dos controlares juntamente com outro ajuste feito através de Redes Neurais Artificiais (RNA), que é proposto como alternativa de comparação ao método dos resíduos. Simulações são efetuadas em um sistema teste simétrico para se verificar resultados e a eficácia do controlador POD (parâmetros ajustados pela RNA proposta), acoplados aos dispositivos FACTS, na manutenção da estabilidade a pequenas perturbações do SEP. Palavras-chave: Controladores POD. Estabilidade de sistema de potência. Redes neurais artificiais. TCSC e SSSC / This work presents studies referred to short term Electric Power System (EPS) perturbations, considering the actuation of FACTS devices for low frequency electromechanical oscillation damping. The devices considered are: FACTS TCSC (Thyristor Controlled Series Capacitor) and the SSSC (Static Synchronous Series Compensator). It is representation and modeling FACTS devices in the EPS inserting in the Power Sensitivity Model. To improve the performance of the EPS considering the short term perturbations, additional controllers are proposed to increase the performance of the TCSC and SSSC devices, introducing the necessary damping to the EPS. The additional POD controller is added to the modified model for TCSC and SSSC devices to verify the acting. The residual theory is used to find the best location to install the devices. The same theory is used to adjust the parameters of the controllers and an adjustment with Artificial Neural Networks (ANN) is proposed as an alternative to the residual method. Simulations are effectuated for a symmetric test system to verify the efficiency of the POD controller (parameters adjusted by the ANN proposed), coupled with the FACTS devices, to maintain the stability considering the short term perturbations

Made available in DSpace on 2014-06-11T19:22:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-01-25Bitstream added on 2014-06-13T20:09:50Z : No. of bitstreams: 1 furini_ma_me_ilha.pdf: 1020610 bytes, checksum: d3a4a2f6ec4cb8559c7d3d6b770ec955 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O objetivo desta Dissertação de Mestrado é apresentar a possibilidade de fornecer amortecimento às oscilações de baixa freqüência do sistema elétrico de potência através dos dispositivos FACTS (Flexible Alternating Current Transmission System) TCSC (Thyristor Controlled Series Capacitor) e UPFC (Unified Power Flow Controller). Para isso realiza-se o desenvolvimento e implementação do Modelo de Sensibilidade de Potência para sistemas multmáquinas. Na seqüência são introduzidos os dispositivos TCSC e UPFC, bem como os seus controladores. Apresentam-se resultados de acordo com a evolução dos modelos que representam os dispositivos FACTS, ou seja, parte-se de uma compensação fixa, passando para um modelo dinâmico de primeira ordem e por fim, é incluído o controlador POD (Power Oscillation Damping). A utilização de sinais locais e remotos para entrada do controlador POD também é analisada. Além disso são mostrados os resultados obtidos pela técnica clássica de introdução de amortecimento através de sinais suplementares (os estabilizadores de sistemas de potência – PSS: Power System Stabilizers). O projeto dos controladores POD e PSS é baseado no método da compensação de fase, utilizando a teoria de controle clássico. Fatores de participação, autovetores, autovalores e resíduos de funções de transferência são utilizados como índices para examinar a melhor alocação dos controladores POD e PSS no sistema elétrico de potência. / The objective of this work is to present the possibility to provide damping to low frequencies oscillations of the electrical power systems by FACTS devices (Flexible Alternating Current Transmission System): TCSC (Thyristor Controlled Series Capacitor) and UPFC (Unified Power Flow Controller). This is developed and implemented using the Power Sensitivity Model for multimachine systems. Afterwards, the TCSC and UPFC devices are introduced as well as the controllers. Results are presented according to the evolution of the models that represent the FACTS devices, i.e., it starts with a fixed compensation, passing through a first order dynamic model and finally, it is included a POD controller (Power Oscillation Damping). It is also analyzed the inclusion of local and remote signals for the input of the POD controller. Besides, results obtained by classical techniques of introducing damping by supplementary signals (Power Systems Stabilizer – PSS) are shown. The project of POD and PSS controllers are based on the Phase Compensation Method using the classical control theory. Participation Factor like eigenvalues, eigenvectors and transfer function residues are used as index to examine the best allocation of the POD and PSS controllers on the electrical power systems.

Orientador: Laurence Duarte Colvara / Resumo: Este trabalho apresenta um estudo sobre o controle de Sistema de Energia Elétrica (SEE) com vistas à melhoria da estabilidade transitória por meio da atuação de dispositivos FACTS, neste momento considerando os compensadores em derivação (SVC) e em série (TCSC). Propõe-se a inclusão, em dispositivos pré-existentes, a incorporação de um controle adicional visando atuação em face de transitórios eletromecânicos. A influência dos dispositivos sobre a capacidade de sincronização entre os pares de máquinas, avaliada por meio do fator de efeito é inserida na atuação dinâmica/transitória do sistema. A evolução da trajetória pós-falta do sistema é considerada em relação às fronteiras da chamada Região de Sincronização Positiva (RSP) e simulações foram realizadas usando os sistemas-teste Simétrico de duas áreas e New England para Lei de Controle proposta e conclui-se que esta é efetiva na melhoria da estabilidade transitória do Sistema de Energia Elétrica e, com aprimoramentos, poderá ser incluída em procedimentos de operação em tempo real. / Abstract: The power system transient stability control is approached by means of FACTS devices, and at this first step the SVC and TCSC devices are considered. A certain device acts upon each pair of machines by means of their synchronization capability which is affected by the corresponding transfer admittance as repeated by the FACTS device. This influence is taken into account by means of a parameter named Effect Factor. The boundaries of a region surrounding the stable equilibrium point named Positive Stability Region are used as reference for critical trajectories and the control action intend to reverse the tendency of the trajectory of leaving this region. In view of the shown tested cases the results are very promising since the proposed control has conduced to improvements in fault critical clearing times and so it has potential to be included in online operation procedures. / Doutor

Interconnection of electric power systems is becoming increasingly widespread as part of the power exchange between countries as well as regions within countries in many parts of the world. There are numerous examples of interconnection of remotely separated regions within one country. Such are found in the Nordic countries, Argentina, and Brazil. In cases of long distance AC transmission, as in interconnected power systems, care has to be taken for safeguarding of synchronism as well as stable system voltages, particularly in conjunction with system faults. With series compensation, bulk AC power transmission over very long distances (over 1000 km) is a reality today. These long distance power transfers cause, however, the system low-frequency oscillations to become more lightly damped. As a result, many power network operators are taking steps to add supplementary damping devices in their systems to improve the system security by damping these undesirable oscillations. With the advent of thyristor controlled series compensation, AC power system interconnections can be brought to their fullest benefit by optimizing their power transmission capability, safeguarding system stability under various operating conditions and optimizing the load sharing between parallel circuits at all times. This thesis reports the results of digital time-domain simulation studies that are carried out to investigate the effectiveness of a phase imbalanced hybrid single-phase-Thyristor Controlled Series Capacitor (TCSC) compensation scheme in damping power system oscillations in multi-machine power systems. This scheme which is feasible, technically sound, and has an industrial application potential, is economically attractive when compared with the full three-phase TCSC which has been used for power oscillations damping.<p> Time-domain simulations are conducted on a benchmark model using the ElectroMagnetic Transients program (EMTP-RV). The results of the investigations have demonstrated that the hybrid single-phase-TCSC compensation scheme is very effective in damping power system oscillations at different loading profiles.