A new power converter for fuel cells with high system efficiency

Abstract

This paper presents a new high-efficiency grid-connected single-phase converter for fuel cells. It consists of a two-stage power conversion topology. Since the fuel cell operates with a low voltage in a wide voltage range (25 V–45 V) this voltage must be transformed to around 350–400 V in order to be able to invert this dc power into ac power to the grid. The proposed converter consists of an isolated dc–dc converter cascaded with a single-phase H-bridge inverter. The dc–dc converter is a current-fed push-pull converter. The inverter is controlled as a standard single-phase power factor controller with resistor emulation at the output. Experimental results of converter efficiency, grid performance and fuel cell dynamic response are shown for a 1 kW prototype. The proposed converter exhibits a high efficiency in a wide power range (higher than 92%) and the inverter operates with a near-unity power factor and a low current THD.