When the temperature detected by the temperature sensor is equal to or higher than a predetermined temperature, the drive system controls the boost converter and the inverter, such that the motor is driven in a range of an electric power on which a limit is imposed to decrease a discharge power upper limit value. When a failure occurs in the boost converter, the drive system stops the boost converter. When it is subsequently determined that the failure of the boost converter causes a failure of the temperature sensor, the drive system controls the inverter, such that the motor is driven without a limit imposed on the discharge power upper limit value, irrespective of the temperature detected by the temperature sensor that is equal to or higher than the predetermined temperature.