A 1kW Grid-Connected Converter System for PEFC

We have developed a small-size high-efficiency grid-connected converter system for a 1 kW PEFC (polymer electrolyte fuel cell) unit, which consists of a novel isolated DC-DC converter and a single-phase inverter whose output voltage is 200 V. In order to reduce reverse recovery losses of diodes in the secondary circuit of the DC-DC converter, two rectifiers with 600 V diodes and an inductor connected in series are employed instead of one rectifier with higher voltage diodes that have a slow reverse recovery characteristic. Furthermore, we have applied a new low-loss clamp-type snubber to the diodes. The efficiency of the converter system is 91.1%, and the efficiency of the DC-DC converter in the system is 94.6% at the nominal condition.