Design considerations for a 48 V fuel cell to split single phase inverter system with ultracapacitor energy storage

Fuel cells are a versatile, renewable energy source that can be used in a wide range of applications. In this paper, topologies for a 10 kW inverter system with a low voltage fuel cell input are evaluated based on simplicity, performance, and cost. This particular fuel cell system is intended for household stand-alone power generation. The inverter proposed has a nominal fuel cell input of 48 VDC and is capable of two single phase 120 VAC outputs and one 240 Vac output. Different topology options are explored for the DC-DC converter and the inverter stages, and one combination is evaluated in detail. There is a clear topological choice for the DC-DC converter, but there are a couple of options that work well for the inverter stage. Different choices for energy storage also exist and a good alternative to batteries is presented. The chosen topology contains two modular units, which are supplemented with a set of ultracapacitors at the input for transient conditions. Each module consists of a full-bridge phase-shifted front-end and a half-bridge inverter. Experimental results are displayed for several load conditions.