A novel three-phase high-power soft switched DC/DC converter for low voltage fuel cell applications

An efficient DC/DC converter is needed as the interface between a low-voltage fuel cell source and a high-voltage bus for inverter operation. In this paper, a three-phase transformer-isolated DC/DC converter utilizing phase-shift modulation is proposed. The converter must be able to boost the voltage significantly and operate at current levels above 240 amps on the source side. Key features of the proposed converter include: reduced transformer turns-ratio by a factor of two while maintaining the same output voltage, reduced the size of passive components including output filter and input DC bus capacitor using three-phase interleaving, eliminated inductor current ripple at phase-shift angles above 120°, and achieved soft switching over a wide load range without auxiliary circuitry. The proposed converter has been analyzed, simulated and implemented in hardware. An efficiency of above 96% was achieved using the prototype unit. Experimental results were used to verify all design and analysis.