A Comparison of Soft-Switched DC-DC Converters for Fuel Cell to Utility Interface Application

High frequency (HF) transformer isolated DC-DC converter is a part of a fuel cell inverter system for utility interface, required to translate the level of low fuel cell stack voltage to meet the peak utility line voltage and provides isolation between inverter and utility line. This paper presents a comparison of various soft-switched HF transformer isolated DC-DC converters for fuel cell to utility interface application. It is shown that due to wide variation in fuel cell voltage with load variation, none of the voltage-fed converters can maintain ZVS for the complete operating range. Active clamped two-inductor current-fed converter is able to maintain ZVS for wide load and fuel cell stack voltage variations and is suitable for the present application. Analytical and simulation results to evaluate the performance of the current-fed converter are presented.