A control unit calculates a motor voltage vector including a corresponding excitation voltage command and a torque voltage command in response to an output request for a motor and distributes the motor voltage vector to a first inverter voltage vector and a second inverter voltage vector while maintaining the motor voltage vector obtained to control modes of operation (PWM, overmodulation, and square wave mode) of a first inverter or a second inverter. The first inverter voltage vector includes an excitation voltage command and a torque voltage command associated with an output from the first inverter, and the second inverter voltage vector includes an excitation voltage command and a torque voltage command associated with an output from the second inverter.