High efficiency power converter for a doubly-fed SOEC/SOFC system

Regenerative fuel cells (RFC) have become an attractive technology for energy storage systems due to their high energy density and lower end-of-life disposal concerns. However, high efficiency design of power conditioning unit (PCU) for RFC becomes challenging due to their asymmetrical current-power characteristics that are dependent on the operation mode (energy storage / energy supply). This paper proposes a new PCU architecture for grid-tie RFC with which the RFC's asymmetrical characteristic becomes less critical and thus a much more symmetrical power rating of the dc-dc converter for both operating modes is possible. This paper discusses the design considerations for this novel PCU, and verifies its operation principle with Matlab/Simulink simulations. Experimental results on a tailored dc-dc converter confirm the design simplifications for high efficiency operation along the entire power operating range of the RFC as well as the utilization of the same control strategy design for the two RFC operating modes.