The inverter 18 is a three-phase inverter, and is connected to the rotary electric machine 20. The inverter 18 converts direct-current power, stepped up by the electric power converter 11, to three-phase alternating-current power, and outputs the three-phase alternating-current power to the rotary electric machine 20. Thus, the rotary electric machine 20 is rotationally driven. The driving force of the rotary electric machine 20 is transmitted to drive wheels (not shown).

During braking of the vehicle, regenerative braking is carried out by the rotary electric machine 20. Regenerated electric power obtained at this time is converted by the inverter 18 from alternating-current power to direct-current power, the direct-current power is stepped down by the electric power converter 11, and the stepped-down direct-current power is supplied to the first battery B1 and the second battery B2.

The CNV controller 13 controls step-up/step-down (electric power conversion) operation and series-parallel switching operation over the electric power converter 11 by controlling the on/off states of switching elements S1 to S4 of the electric power converter 11. The controller 22 controls DC-AC conversion or AC-DC conversion by controlling the on/off states of switching elements (not shown) of the inverter 18. Through control over the electric power converter 11 and the inverter 18, the CNV controller 13 and the controller 22 control the driving of the rotary electric machine 20.

Details of Components