Bi-directional dc-dc converter for fuel cell generation system

Fuel cell (FC) has slow response characteristic for load variation. In this paper, bi-directional dc-dc converter for FC generation system is proposed to improve load response characteristic. The bi-directional converter interfaces the low voltage battery to the inverter dc link of FC generation system. When power flows from the low voltage side (battery: 48 V) to the high voltage side (dc link: 380 V), the circuit works in discharge operation (boost mode) to power the high voltage side load; otherwise, it works in charge operation (buck mode) to charge the low voltage side battery. A simple voltage clamp branch is used to limit transient voltage across the current-fed full bridge and realize zero-voltage-switching (ZVS) during discharge operation. A soft switched, isolated bi-directional dc-dc converter has been developed for FC generation system, in which the 48 V battery for the system accessory loads is also used to start up the FCs and to charge the energy consumed on operating of FC generation system.