A 10-kW SOFC low-voltage battery hybrid power conditioning system for residential use

This paper proposes a 10-kW power conditioning system for a 5-kW solid oxide fuel cells (SOFCs) low-voltage battery hybrid power generation that has been developed for participation in the 2003 Future Energy Challenge Competition organized by the U.S. Department of Energy and the IEEE. The objective of the competition was to develop a fuel cell inverter with minimum requirement for cost of $40/kW and efficiency of 90%. The proposed power conditioning system consists of the front-end dc-dc converter, the dc-ac inverter and the bidirectional dc-dc converter. Practical issues such as component rating calculation, high-frequency transformer design, heat sink design, and protection are detailed aiming at the cost and efficiency targets. A low-cost implementation of controllers is discussed along with current-mode control, output voltage regulation with capacitor balancing and an SOC control for battery management. A 10-kW hardware prototype was successfully built and tested in the steady-state as well as in the transient-state. Experimental performances are compared to minimum target requirements of the fuel cell inverter. The cost analysis is done based on the spreadsheets evaluation forms provided in the competition.