POWER SUPPLY SYSTEM AND VOLTAGE CONTROL METHOD FOR FUEL CELL

A voltage control method for a fuel cell (100) includes: interrupting electrical connection between the fuel cell and a load (170, 172) in a low load state; supplying oxygen to the fuel cell in accordance with a preset condition during the electrical connection is interrupted; detecting an OCV (open circuit voltage) of the fuel cell after oxygen is supplied to the fuel cell in accordance with the preset condition; reducing an amount of oxygen supplied to the fuel cell when the OCV is higher than a target voltage by a first value or larger; increasing the amount of oxygen when the OCV is lower than the target voltage by a second value or larger; and keeping the amount of oxygen when the OCV is lower than a sum of the target voltage and the first value and higher than a value obtained by subtracting the second value from the target voltage.