Proposal of three-phase two-level unidirectional SEPIC PWM rectifiers with high power factor

This paper presents the initial theoretical analysis of three-phase two-level unidirectional SEPIC PWM rectifiers. The rectifiers operate in CCM (continuous conduction mode) with high power factor and output voltage control. Converter switching stages are analyzed for single-phase structure and the three-phase Y-connected and the Δ-connected rectifiers are derived from it. These rectifiers have the advantages of providing high power factor with low input filtering effort, as Boost rectifiers, and lower output voltage level, as Buck rectifiers. The disadvantage is the increase of component count, due the need for additional capacitors and inductor per phase. The control strategy is presented with a description of the objectives of the mains current control loop and the output voltage control loop. Simulation results from a rectifier with 380V input voltage, 400V output voltage, 20kHz switching frequency and 6kW output power are also presented.