Right after a system operation start but before a smoothing capacitor has been sufficiently pre-charged, conversion voltage control is executed to control a voltage boosting converter so that a system voltage is first raised to a target value. After the smoothing capacitor has been pre-charged, the conversion voltage control is changed over to conversion power control to control the output power of the voltage boosting converter, so that the output power of the voltage boosting converter is brought into agreement with a command value. While the conversion power control is being executed, system voltage control by operating the input power to the MG unit is prohibited.