A control system for controlling power flow in a power bus generally powered by a reformer-based fuel cell system (FCS) is provided. The control system comprises an energy storage device (ESD); a power interface unit coupled to selectively and bi-directionally pass power between the energy storage device and the power bus; and a controller coupled to the power bus to receive one or more signals indicative of the instantaneous power delivered by the fuel cell system. The controller may be configured so that the energy storage device may supply power to the power bus at least during transient conditions when the instantaneous power delivered by the fuel cell system drops below a (FCS) power command signal.