Unidirectional Three-Phase Voltage-Doubler SEPIC PFC Rectifier

Abstract

This article reports the theoretical analysis and experimental results for a three-phase high power factor SEPIC-type rectifier operating in discontinuous conduction mode (DCM). The topology, steady-state analysis, dynamic model, control strategy, and experimental verification are reported herein. The operation in DCM naturally provides input currents with low harmonic content that are in phase with input voltages without the need for current control, due to the converter operation as a voltage follower. Thus, the control system and the PWM modulator are simplified, when compared to other three-phase high power factor rectifiers. The proposed three-phase SEPIC rectifier employs the voltage-doubler concept, which means it may reduce the voltage stress on the switches and diodes or it may supply double voltage gain with the same voltage stress. It also uses a three-state switch, and four different implementations are approached in this article, including bridgeless structures. The theoretical study was corroborated by experimental results obtained with a prototype built using the following design specifications: 220 V input voltage, 400 V output voltage, 3000 W output power, and 50 kHz switching frequency. Peak efficiency of 95.85%, THD of 3.1%, and power factor of 0.9991 were achieved.