Analysis of a Voltage-fed Full Bridge DC-DC Converter in Fuel Cell Systems

Fuel cells at moderate power levels have a high output current and low output voltage. In order to make them usable for applications with a higher voltage demand, a DC-DC converter with large voltage gain is needed. This paper deals with a voltage-fed full bridge converter that is designed to reach a high voltage gain. Analytical calculations are given, completely describing the operating behaviour of the converter. Herewith, the impact of the output inductor choke, the transformer's winding ratio and its leakage inductance on the operating behaviour and the value of the output voltage is analysed. For both, the output inductor and the transformer, design considerations are given. All results are verified by simulations and experimental results taken from a 1.2 kW prototype.