Projeto e desenvolvimento de uma fonte de potência CA trifásica a quatro fios

Abstract

This work presents a contribution to the study of AC Power Sources, where a prototype s development is presented. The stages that compose the system, including converter topology, filter, instrumentation and controller, are presented. The developed prototype is a three-phase four-wire source, which uses a four-leg voltage source inverter. This topology increases the flexibility for unbalanced waveforms generation or unbalanced load conditions, also simplifying the control problem of the process. This work first looks for justifying the use and the study of AC Power Sources, in this sense, some examples of tests and norms, whose tests demand its use, are given. The applications are in general related to electrical and electronic equipments and for driving electromechanical plants such as shakers. In this sense, AC Power Sources are equipment that can be used both in industry applications and didactic or research laboratories. In practically all applications, it is shown that good performance in waveforms generation is necessary. This performance is related to the ability for waveforms generation with low harmonic distortion even in conditions of variable frequency or amplitude and with nonlinear loads behavior. In this way, the use of an adequate converter topology is not enough, are too necessary controllers to guarantee performance for the system, even in adverse load conditions or in presence of unmodeled dynamics. The unmodeled dynamics are derived from some stages that compose the system, but they are generally related to the uncertainties on the model of the plant and load. Then, this work not only describes the implemented prototype and topological relative questions but also applies a Robust Model Reference Adaptive Control (RMRAC) for the plant control. This technique improves the robustness in the closed loop system even under presence of unmodeled dynamics and disturbances. The controller makes use of a Gradient type algorithm for parametric adaptation with four adapted parameters, which leads to a new error equation that is used for the controller s implementation