A Minimum Power-Processing-Stage Fuel-Cell Energy System Based on a Boost-Inverter With a Bidirectional Backup Battery Storage

When low-voltage unregulated fuel-cell (FC) output is conditioned to generate ac power, two stages are required: a boost stage and an inversion one. In this paper, the boost-inverter topology that achieves both boosting and inversion functions in a single stage is used to develop an FC-based energy system that offers high conversion efficiency, low-cost, and compactness. The proposed system incorporates additional battery-based energy storage and a dc-dc bidirectional converter to support instantaneous load changes. The output voltage of the boost-inverter is voltage-mode controlled and the dc-dc bidirectional converter is current-mode controlled. The load low-frequency current ripple is supplied by the battery, which minimizes the effects of such ripple being drawn directly from the FC itself. Analysis, simulation, and experimental results are presented to confirm the operational performance of the proposed system.