Loss Comparison of Two Bidirectional Isolated DC/DC Converters for Reversible Solid Oxide Fuel Cell Systems

The reversible solid oxide fuel cell (RSOFC) is a promising solution for future storage system in power grid, but the wide voltage range makes it difficult to design the DC/DC converter for RSOFC stack. In this paper, the losses of two DC/DC topologies, CLLC cascade interleaved Buck(two-stage) converter and dual-active-bridge(DAB) converter, are compared as the interface DC/DC converter for RSOFC. Firstly, the topology and control method is introduced for two selected DC/DC converters. Secondly, the losses of two converters are analyzed and corresponding loss models are presented. The loss models are also extended for multi-port topology. At last based on 1kW single port prototype, the experiments are conducted and the total loss are measured for two topologies. Both the model and experimental results indicate that the two-stage topology has higher efficiency and is selected for the interface DC/DC converter for RSOFC stack.