Fuel cell system

A fuel cell system comprising:

• a fuel cell (FC) stack;
• a compressor having an air bearing;
• a battery;
• a valve configured to adjust an amount of air to be supplied to the FC stack;
• and
• a controller configured to control the compressor and the valve, wherein:
• the controller is configured to execute, when a supply of fuel to the FC stack is stopped because a state of charge of the battery is equal to or higher than a predetermined state of charge, a stack protection control in which less air is supplied to the FC stack than when the fuel is being supplied;
• and
• the stack protection control includes
• a first control in which the compressor is rotated at a rotational speed lower than a floating rotational speed of the air bearing and the valve is fixed at a predetermined opening degree to supply less air than when the fuel is being supplied, and
• a second control in which the compressor is rotated at a rotational speed equal to or higher than the floating rotational speed of the air bearing and the valve is adjusted to an opening degree smaller than the predetermined opening degree to supply less air than when the fuel is being supplied.