To solve the problem, wherein fluctuations are producedin torque, at controlling of as variable of an electric motor by operating a power conversion circuit having a switching element connecting a terminal of the electric motor whose neutral point is connected to a first DC power supply to the anode and to the cathode of a second DC power supply.
Polarity inversion avoidance control for avoiding inversion of polarity of phase current of respective phases in the electric motor is performed by operating command voltage. In more detail, a command voltage is operated to perform feedback control so that a current offset amount, which is the amplitude center of phase current with respect to a point where phase current becomes zero, becomes not less than the amplitude value of phase current. Command voltage is operated by offset-operating command voltage to a negative side when the current offset amount is smaller than the amplitude value.
FUJII ATSUSHI
SUZUKI TAKASHI
Yasunari Kurita
Kyoko Hino
Satoru Ando