This thesis presents the development of a generalised computer program to calculate harmonic currents and voltages in six and twelve-pulse thyristor controlled reactors under non-ideal conditions. Thyristor controlled reactors are a relatively new source of harmonic distortion in power systems. The steady state characteristic harmonics are well known. Other non-characteristic harmonics can, however, be generated. A detailed representation is therefore necessary. Apart from the most common non-ideal conditions, such as voltage, impedance and firing pulse unbalances, this work allows voltage harmonic distortions, two firing pulse control methods, the effect of the feedback control in the equally spaced firing pulse control and the effect of the step-down transformer saturation. The effect of the a.c. system impedance, filters and capacitor banks is also included. Four different models of filters were implemented. With non-infinite a.c. systems, the harmonic currents generated are not totally absorbed by the filters. The remaining distortion may affect the main busbar voltages. Therefore, an iterative method was adopted in which the distorted voltages calculated at the end of one iteration are used to calculate the new currents and voltages. The process is repeated until convergence is reached. Several cases were then studied using this program which was then joined to an existing steady-state converter harmonic program. For instance, the need for a more complete representation of controlled reactors, converters and a.c. system network is illustrated. This study begins considering an hvdc station under ideal conditions which are then gradually moved towards more real conditions. The influence of the a.c. system representation in harmonic studies is also discussed. This analysis also compares the performance of two filter designs, namely the tuned and the damped filters. A study of harmonic magnification in the presence of a.c. and d.c. resonances is also included. The harmonic calculations program presented in this thesis is able to study so many conditions of operation of converters and/or thyristor controlled reactors that it is impractical to show all the possible cases. For instance, filters and capacitor banks can be installed at the converter busbar or at any controlled reactor busbar. Furthermore, the three-phase calculation approach allows studies in which some abnormal operation, such as the absence of a filter branch or capacitor bank at one phase, can be observed.

Harmonic domain models have been developed for Thyristor Controller Reactors (TCR) and other power electronic devices. Recently, these models have been extended to describe not just the steady-state harmonic interactions but harmonic transients as well. However, these dynamic models consistently do not incorporate models for controls. On the other hand, for the TCR as a FACTS Controller, dynamic models are available in which only the fundamental frequency component of the Controller is included; excluding harmonic interactions presumes that these do not affect the dynamics of the Controller. This thesis describes the development of a Harmonic State Space (HSS) model of a three phase TCR. As an extended state space description, this model describes the dynamics of the Controller while capturing harmonic interactions. It also includes the effect of switching instant variation which significantly improves the effectiveness of the model and allows the controller feedback characteristics to be included. The result of this model was validated with a purely time-domain simulation in PSCAD/EMTDC. Using the HSS to model a power system with TCR, it is illustrated that harmonic interactions play a significant role in the dynamics of the system. It is observed that for the specific system analysed, the least-damped pole-pair which dominates the dynamics of the system is associated with the 5th harmonic. Failure to include interactions with this specific harmonic produces an inaccurate dynamic description. Preliminary to the development of HSS model, a linearised harmonic domain model of a TCR which establishes the harmonic interactions across the device is also developed. Results of this model are validated with a time-domain simulation. This characterisation paves the way for a reduced harmonic state space model that is used in the HSS model. The principles and procedures established in this thesis can be applied to the development of models for other FACTS Controllers or HVDC links.

Este trabalho analisa a necessidade da aplicação dos compensadores estáticos de reativos em sistemas elétricos industriais e em sistemas de potência. Vários tipos de compensadores de reativos são apresentados e também é feita uma comparação entre eles. O trabalho está centralizado no estudo dos compensadores estáticos tiristorisados, principalmente o Reator Controlado a Tiristores (RCT) e o Capacitor Chaveado a Tiristores (CCT). São discutidas as influências de alguns parâmetros nas formas de onda do RCT. É feita a dedução das equações das componentes harmônicas de corrente e tensão do RCT. São também analisados os efeitos das harmônicas e os meios de atenuá-las, de modo a mantê-las dentro de níveis razoáveis. Modelos para a simulação de um RCT, para vários tipos de fenômenos em circuitos monofásicos e trifásicos, são apresentados. São Mostrados gráficos e tabelas de algumas simulações utilizando o programa CSMP (Continuous System Modeling Program) e um programa desenvolvido ciclo a ciclo, utilizando o método passo a passo. As simulações permitem avaliar com razoável precisão o comportamento do RCT associado a um capacitor fixo. Sugestões de estudos afins são apresentadas no final do trabalho. / This work analyses the need of using Var systems in industrial and in power electric systems. Various types of VAr systems are presented and also a comparison among them is done. The work is centralized in the study of thyristor static VAr systems. The thyristor controlled reactor (TCR) and the thyristor switched capacitor (TSC) are analysed in more details. Parametric influences in the wave forms of TCR are discussed. TCR voltage and current harmonic equations are deduced. Harmonic effects and also the methods of producing their attenuation are analysed. TCR simulation models for multiple types of phenomena in one phase and three phase circuits are presented. Some graphics and tables using the CSMP (Continuous System Modeling Program), and a cycle by cycle program that uses the step method are showed. The simulations can evaluate with a reasonable precision the behavior of a TCR with a fixed capacitor (FC). Suggestions of other studies are presented at the end of the work.

Este trabalho analisa a necessidade da aplicação dos compensadores estáticos de reativos em sistemas elétricos industriais e em sistemas de potência. Vários tipos de compensadores de reativos são apresentados e também é feita uma comparação entre eles. O trabalho está centralizado no estudo dos compensadores estáticos tiristorisados, principalmente o Reator Controlado a Tiristores (RCT) e o Capacitor Chaveado a Tiristores (CCT). São discutidas as influências de alguns parâmetros nas formas de onda do RCT. É feita a dedução das equações das componentes harmônicas de corrente e tensão do RCT. São também analisados os efeitos das harmônicas e os meios de atenuá-las, de modo a mantê-las dentro de níveis razoáveis. Modelos para a simulação de um RCT, para vários tipos de fenômenos em circuitos monofásicos e trifásicos, são apresentados. São Mostrados gráficos e tabelas de algumas simulações utilizando o programa CSMP (Continuous System Modeling Program) e um programa desenvolvido ciclo a ciclo, utilizando o método passo a passo. As simulações permitem avaliar com razoável precisão o comportamento do RCT associado a um capacitor fixo. Sugestões de estudos afins são apresentadas no final do trabalho. / This work analyses the need of using Var systems in industrial and in power electric systems. Various types of VAr systems are presented and also a comparison among them is done. The work is centralized in the study of thyristor static VAr systems. The thyristor controlled reactor (TCR) and the thyristor switched capacitor (TSC) are analysed in more details. Parametric influences in the wave forms of TCR are discussed. TCR voltage and current harmonic equations are deduced. Harmonic effects and also the methods of producing their attenuation are analysed. TCR simulation models for multiple types of phenomena in one phase and three phase circuits are presented. Some graphics and tables using the CSMP (Continuous System Modeling Program), and a cycle by cycle program that uses the step method are showed. The simulations can evaluate with a reasonable precision the behavior of a TCR with a fixed capacitor (FC). Suggestions of other studies are presented at the end of the work.

In this research work, the control system of 16 MVAr, 13.8 kV TCR will be designed and digitally implemented. A Real-Time Control System (NI CompactRIOTM Reconfigurable I/O) and a Digital Platform (NI LabVIEWTM Gcode) are used in the digital implementation of TCR control system. The digital control system is composed of reactive power calculation, firing angle determination and triggering pulse generation blocks. The performance of control system will be tested in the field. The simulation results will also be compared with test data.

In this thesis, control schemes for the self-excited induction generator are developed with Matlab/Simulink. Self-excited induction generator is considered as a constant voltage-constant frequency supply for an isolated load. A wind turbine is assumed to be the variable-speed drive of the induction generator. Control schemes aim to ensure a constant voltage-constant frequency operation of the induction generator in case of the variations in the wind speed and/or the load. From the general model of the self-excited induction generator, the characteristics of the system and the dynamic responses of the system in case of any disturbance are examined. Next, the control strategies are developed both for the squirrel-cage rotor induction generator and for the wound-rotor induction generator. Two control loops are necessary for constant voltage-constant frequency operation of a variable speed induction generator, one for the voltage regulation and the other for the frequency regulation. After developing the control loops, constant voltage-constant frequency operation of the self-excited induction generator is simulated with a cage type saturation adaptive induction generator, a fixed capacitor with thyristor controlled reactor (TCR) used for frequency regulation and switched external resistors connected to the stator terminals used for voltage regulation.

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