A new three phase AC to DC rectifier with active power factor correction

Abstract

A new three phase AC to DC rectifier system with near unity input power factor and reduced input current harmonics is proposed, The proposed approach employs three SCRs and three active semiconductor switches with anti-parallel diodes to form a three phase bridge. In the proposed approach only two semiconductor device drops are encountered in the power flow path. Also the DC link inductor is unnecessary and three AC side inductors are used instead. It is shown that discontinuous input current is the preferred mode of operation to realize high quality input current. A suitable control strategy is proposed in order to minimize the input current THD. Further, a zero voltage switching strategy is implemented to minimize the switching losses. The SCRs are suitably phase controlled to limit inrush currents during starting and to provide current limiting action under overload or output short circuit conditions. During normal operation the SCRs are gated to function as diodes. A design procedure for the proposed approach to achieve near sinusoidal input currents and zero voltage switching is detailed. Simulation and experimental results on a laboratory prototype system are discussed. >