Control device and control method for electric motor, and motor and vehicle driving system to which the control device and control method are applied

A control device for an electric motor that controls an operation of the electric motor by outputting PWM signals to switching elements included in an inverter, the inverter being capable of converting an input direct-current voltage into an alternating-current voltage having an arbitrary frequency and an arbitrary voltage, the control device for the electric motor comprising:

• a voltage-command generating unit configured to generate, as voltage commands, a superimposed wave signal obtained by superimposing, on a sine wave having an output frequency of the inverter as a fundamental frequency, a third harmonic of the sine wave;
• and
• a PWM-signal generating unit configured to generate the PWM signals by comparing amplitude of the voltage commands output by the voltage-command generating unit and amplitude of a predetermined carrier signal, wherein
• an asynchronous carrier signal is input to the PWM-signal generating unit, and
• the PWM-signal generating unit generates PWM signals each including a plurality of pulses in a half cycle of an inverter output voltage and outputs the PWM signal in all control regions of the electric motor.