A ZVS Bi-Directional DC–DC Converter for Multiple Energy Storage Elements

This letter presents a high-power-density multi-input dc-dc converter interfaced with energy storage elements such as a battery and an ultracapacitor. The converter consists of three half-bridges and a high-frequency multi-winding transformer. Bi-directional power flow between input and output is achieved by adjusting the phase-shift angles of the voltages across the two sides of the transformer. Soft-switching is implemented naturally by snubber capacitors and transformer leakage inductance. Operation principles are analyzed in detail. Simulation and experimental results are provided to verify the performance of the proposed converter