In order to use hydrogen fuel cells in domestic applications either as main power supply or backup source, their low DC output voltage has to be matched to the level and frequency of the utility grid AC voltage. Such power converter systems usually consist of a DC-DC converter and a DC-AC inverter. The paper focuses on double-stage, grid-connected Fuel Cell conversion systems. Comparison of different structures of resonant DC-DC converters, which allows reduced switching losses, are analyzed accounting the specific behavior of Fuel Cells. The converter is elaborated for 5 kW power to match the rated power of the proton exchange membrane (PEM) fuel cell