Estratégia de controle para retificadores boost PWM bidirecionais monofásicos e trifásicos.

Abstract

A.c.- d.c. converters are widely used to supply direct current loads. The diodebased rectifiers are a valid alternative, but these rectifiers without control inject high levels of harmonic currents into the feeder and therefore, distort the voltage available for other loads at the point of common coupling. Furthermore it is not possible to control the dc bus voltage. Controlled rectifiers using PWM are being increasingly used instead of conventional diode rectifiers because they present a high power factor to the source and allow voltage control of the dc bus. Moreover, distortion of the source currents may be minimized. This dissertation presents a simplified control strategy for the boost PWM rectifiers and its control objectives are: (i) to improve the power factor of the rectifier; (ii) to control the dc bus voltage and (iii) to minimize the unbalance and distortion of the source currents. Unlike most previous research in control strategies, the control method presented in this work addresses the scenario where the input voltage of the rectifier presents distortion or imbalance, achieving the control objectives in the face of this scenario. The proposed control strategy has been validated by software simulations and experimental results obtained with a low-voltage, low-power prototype built in the laboratory.