New control scheme for 3-phase PWM AC/DC converter without phase angle detection under unbalanced input voltage conditions

Abstract

Generally, most of 3-phase PWM AC/DC converters have been implemented in the synchronous frame model to eliminate steady state errors effectively and have fast transient response characteristics. But such designed controllers have input current harmonics and DC-link voltage ripples under unbalanced input voltage conditions because they have been designed under assumption of balanced input voltage conditions. In this paper, the new control scheme is designed to minimize harmonic distortions of the input current and the output DC-link voltage in 3-phase PWM AC/DC converter systems under unbalanced input voltage conditions. The synchronous frame input voltage, which is considered as input side back-EMF component, is regulated pertinently according to input voltage condition. Where, the analysis of the input voltage is implemented without zero crossing and magnitude detecting of each phase voltage. The current reference is selected to eliminate the reactive power and the harmonic active power. The proposed control scheme is simple and minimizes effectively the harmonic distortions in input and output system under unbalanced input voltage conditions.