Fuel cell system and control method thereof

The invention provides a fuel cell system and a control method thereof. A fuel cell system is provided with: a fuel cell; a temperature sensor for measuring the temperature of the fuel cell; and a control unit that, when the temperature measured by the temperature sensor is equal to or lower than a preset rapid warm-up start temperature, executes the rapid warm-up operation of the fuel cell until the measured temperature is equal to or higher than a preset rapid warm-up completion temperature. When the occurrence of an abnormality in the temperature sensor is determined during the rapid warm-up operation, (a) if an estimated temperature used as the temperature of the fuel cell is equal to or greater than a preset re-freezing prevention temperature, the control unit replaces the operation for outputting power from the fuel cell with the rapid warm-up operation. (b) When the estimated temperature used as the temperature of the fuel cell does not rise to the re-freezing prevention temperature, the operation of t