Unified modulation for three-phase current-fed bidirectional dc-dc converter under varied input voltage

In this paper, a new three-phase current-fed bidirectional DC-DC converter is proposed. The topology integrates a three-phase boost converter with a three-phase galvanically isolated bidirectional DC-DC converter. Keeping dc bus voltage constant allows high efficient energy conversion over a wide input voltage and maintains ZVS conditions in the whole operation range. By using compact small inductance dc inductors the ZVS conditions can be improved in low power range and the switching losses of the lower switches are reduced. At the same time the input current ripple can be alleviated by three-phase interleaved structure. Finally, a 6-kW hardware prototype is constructed and tested. The experimental results verify it can maintain high efficiency over wide input voltage and power range.