Non-Isolated Power Converters for Fuel Cell Power Sources

Fuel Cells are high current low voltage (HCLV) power sources. The output voltage of a stack is around or under 50 V. The power conditioning system which is to be incorporated with these power sources must provide a high voltage conversion ratio with small ripple in FC output current and no reverse current. For automotive, grid connected and portable applications the PEMFC type FCs are most appropriate, due to their high power density, low temperature and faster transient response for the dynamic loading conditions. For the requirement of a DC link voltage smaller than the FC stack voltage, buck converters are used and such applications include portable power and battery charging. A special case is when the regulated voltage falls inside the FC unregulated voltage range and requires the use of buck-boost converters. The distinctively non-isolated type converters are boost, buck, buck-boost, Cuk, and Sepic converters. Considering the number of switches connected in the topologies i.e., isolated converters are further classified as single switch and multiple switch converters.