Novel Single-Stage Isolated Natural Ohmic Mains Behaviour Fixed Voltage Transfer Ratio Three-Phase Rectifier Using Monolithic Bidirectional 600 V GaN Transistors

This paper introduces a novel phase-modular single-stage isolated three-phase PFC rectifier with a fixed (load-independent) ratio between grid voltage amplitude and dc output voltage. The ac front-end employs star-connected half-bridges with recently developed 600-V GaN monolithic bidirectional switches (M-BDSs) to directly connect to a 400-V (line-to-line rms) three-phase mains. Series-resonant compensation of the transformer’s leakage inductance and operation of the system at the resonance frequency results in a load-independent dc output voltage, directly defined by the grid voltage amplitude, and natural ohmic mains behaviour, i.e., sinusoidal input currents, without any closed-loop control. Accordingly, the converter features low complexity in both, the circuit structure and the modulation, and thus enables high reliability / availability and low assembly effort. The paper provides a detailed analysis of the converter system operating principle, determines the main power component stresses, and validates the concept by circuit simulations.