Fuel cell system

A fuel cell system comprising:

• a fuel cell to generate electric power, being supplied with a fuel gas to a fuel electrode thereof and an oxidant gas to an oxidant electrode thereof;
• a fuel gas supplying device which supplies the fuel gas to the fuel electrode of the fuel cell;
• an oxidant gas supplying device which supplies the oxidant gas to the oxidant electrode of the fuel cell;
• a fuel gas pressure detector which detects fuel gas pressure at the fuel electrode of the fuel cell;
• a fuel gas pressure regulating device which regulates the fuel gas pressure at the fuel electrode of the fuel cell;
• an exhaust fuel gas discharging device which discharges exhaust fuel gas from the fuel electrode of the fuel cell to the outside, the exhaust fuel gas discharging device including a purge valve;
• an exhaust fuel gas treatment device which treats the exhaust fuel gas discharged from the purge valve to reduce fuel gas concentration thereof;
• and a controller which controls power generation of the fuel cell,
• wherein the controller:
• continues power generation of the fuel cell, controls the fuel gas pressure regulating device to lower the fuel gas pressure at the fuel electrode, having the oxidant gas supplying device continue supplying the oxidant gas to the oxidant electrode, and closes the purge valve;
• and
• after the fuel gas pressure at the fuel electrode becomes equal to or lower than atmospheric pressure, stops power generation of the fuel cell and gas treatment of the exhaust fuel gas treatment device,
• wherein the fuel gas supplying device includes a supply source which stores the fuel gas at high-pressure, and a shutoff valve provided on a downstream side of the supply source,
• wherein the fuel gas pressure regulating device comprises a variable throttle valve provided on a downstream side of the shutoff valve to regulate the fuel gas pressure at the fuel electrode of the fuel cell,
• wherein, before stopping power generation of the fuel cell, the controller is further configured to continue power generation of the fuel cell, to have the fuel gas supplying device continue supplying the fuel gas to the fuel electrode while stopping the oxidant gas supplying device supplying the oxidant gas to the oxidant electrode, and close the purge valve, and
• wherein the controller is configured to stop power generation of the fuel cell while stopping the fuel gas supplying device supplying the fuel gas to the fuel electrode by closing the shutoff valve so as to make substantially simultaneous a timing when a voltage of the fuel cell becomes equal to or lower than a predetermined value, and a timing when fuel gas pressure at the downstream side of the shutoff valve becomes equal to or lower than another predetermined value.