Fuel cell system

A fuel cell system is provided which controls the temperature while maintaining the internal pressure of the fuel cell system to a permitted pressure range. A target variation amount ( DELTA gj) in the flow rate of the anode effluent is calculated based on a single target temperature-time curve (Ai) selected from a plurality of target temperature-time curves. Furthermore the pressure variation ( DELTA Pj) of the reformate gas produced by variation in the target flow rate ( DELTA gj) is predicted. It is determined whether the predicted pressure will be maintained to a permitted temperature range. When the predicted pressure will not be maintained to the permitted temperature range, a temperature-time curve with more gentle variation is selected. A final curve is selected by repeating the selection process until it is determined that the predicted pressure will be maintained to the permitted temperature range.