Fuel cell system

A fuel cell system comprising:

• a fuel cell that generates power by being supplied with an anode gas and a cathode gas;
• an anode gas supply and exhaust part configured to supply the anode gas to the fuel cell through an anode supply flow path, discharge the anode gas from the fuel cell through an anode discharge flow path, and circulate the anode gas from the anode discharge flow path to the anode supply flow path through a circulation flow path;
• a cathode gas supply and exhaust part configured to supply the cathode gas to the fuel cell through a cathode supply flow path, discharge the cathode gas from the fuel cell through a cathode discharge flow path, and bypass the cathode gas from the cathode supply flow path to the cathode discharge flow path through a bypass flow path;
• and
• an electronic control unit including a microprocessor and a memory connected to the microprocessor, wherein
• the microprocessor is configured to perform
• controlling the anode gas supply and exhaust part and the cathode gas supply and exhaust part in accordance with a required power,
• the cathode gas supply and exhaust part includes a first valve provided in the bypass flow path and a second valve provided in the cathode discharge flow path, and
• the microprocessor is configured to perform
• the controlling including gradually increasing a valve opening degree of the first valve and decreasing a valve opening degree of the second valve such that a pressure of the cathode gas in the cathode supply flow path gradually decreases when a degree of a decrease in the required power becomes equal to or greater than a predetermined degree.