Propostas para Regulação de Tensão em Geradores de Indução Trifásicos Autoexcitados: Análise com Carga Dinâmica e com Carga Desequilibrada

Abstract

This thesis presents proposals for controlling the terminal voltage on three-phase self-excited induction generators, based on the methodology of static var compensators. However, different to the traditional method that uses thyristors in antiparallel switched reactors, the proposed voltage regulator uses bidirectional switches. These switches are triggered by means of a PWM signal that originates from the operation of a PID controller, thus generating an effective voltage over reactors that consumes the reactive power from the system, and through such controlling the terminal voltage of the generator. Based on the use of bidirectional switches, two voltage regulator proposals are presented for the three-phase self-excited induction generator. The first is directed toward balanced loads, where the regulator presents only a PID controller on its circuit. In this case, the performance of the regulator is tested in the presence of a dynamic load (direct startup of an induction motor). To demonstrate further this case, computer and experimental results are presented. However, the second case looks at optimizing the working of the voltage regulator presented in first proposal, as it allows the induction generator, even when supplied with an unbalanced load, to present the most symmetrical terminal voltage possible, while maintaining it within the permitted voltage regulation range. In this case, a voltage regulator is proposed with individual control for each phase of the generator, that is, the bidirectional switches of each phase receive a PWM signal from different controllers. Thus, the switching of this regulator allows for the supply of the reactive energy necessary for maintaining the voltage of each phase within the established value, while compensating the influence of voltage unbalance. In order to demonstrate this proposal, the results are presented by means of computer simulation.