Fuel cell system

A fuel cell system comprising:

• a fuel cell unit including first and second fuel cells that supplies electric power to a load device;
• first and second supply systems configured to respectively control first and second flow rates of cathode gas respectively supplied to the first and second fuel cells;
• a switching device capable of switching the fuel cell unit and the load device between an electrically connected state where the fuel cell unit is electrically connected to the load device, and an electrically disconnected state where the fuel cell unit is electrically disconnected to the load device;
• a switching control unit configured to switch the fuel cell unit and the load device to the electrically disconnected state, when required power of the fuel cell unit is equal to or smaller than a threshold;
• an open circuit voltage obtaining unit configured to obtain a first open circuit voltage of the first fuel cell and a second open circuit voltage of the second fuel cell in the electrically disconnected state;
• and
• a supply system control unit programmed to increase and decrease the first and second open circuit voltages so as to respectively converge within first and second target ranges, by controlling the first and second supply systems to increase and decrease the first and second flow rates at different timing.