Control system for fuel cell

A control system for a fuel cell, comprising:

• a discharged reactant gas flow control unit disposed at an outlet portion of said fuel cell, said discharged reactant gas flow control unit including:
• a first control valve which is under feedforward control based on a target value of a pressure-flow characteristic of a reactant gas or a discharged reactant gas,
• a second control valve disposed in parallel with said first control valve, said second control valve being under feedback control based on a detected value of pressure-flow characteristic of the reactant gas or the discharged reactant gas and having a different pressure-flow control characteristic as compared with said first control valve, wherein
• said first control valve and said second control valve are under digital control so that the opening degree of said first and second control valves may vary in a stepwise manner, the opening degree of said first control valve per one step being less than or equal to the maximum opening degree of said second control valve,
• only said second control valve controls the flow rate of a discharged reactant gas until the flow rate exceeds a predetermined value, and
• said second control valve together with said first control valve controls the flow rate of the discharged reactant gas when the flow rate of the discharged reactant gas exceeds said predetermined value.

A control system for a fuel cell, comprising:

• a fuel reforming unit which reforms a fuel so as to produce a hydrogen-enriched reformed fuel;
• a fuel supply unit which supplies the hydrogen-enriched reformed fuel from said fuel reforming unit to said fuel cell;
• and
• a discharged fuel flow control unit disposed at an outlet portion of said fuel cell, said discharged fuel flow control unit including:
• a first control valve;
• and
• a second control valve disposed in parallel with said first control valve, said second control valve having a different pressure-flow control characteristic as compared with said first control valve, wherein
• only said second control valve controls the flow rate of a discharged fuel until the flow rate exceeds a predetermined value, and
• said second control valve together with said first control valve controls the flow rate of the discharged fuel when the flow rate of the discharged fuel exceeds said predetermined value.

A control system for a fuel cell, comprising:

• an air pressurizing unit which pressurizes air to produce pressurized air;
• a pressurized air supply unit which supplies the pressurized air from said air pressurizing unit to said fuel cell;
• and
• a discharged air flow control unit disposed at an outlet portion of said fuel cell, said discharged air flow control unit including:
• a first control valve;
• and
• a second control valve disposed in parallel with said first control valve, said second control valve having a different pressure-flow control characteristic as compared with said first control valve, wherein
• only said second control valve controls the flow rate of a discharged air until the flow rate exceeds a predetermined value, and
• said second control valve together with said first control valve controls the flow rate of the discharged air when the flow rate of the discharged air exceeds said predetermined value.