A period composed of a total of three periods, namely a period when an actual voltage vector is employed and periods before and after it can be regarded as an isolation period when an actual voltage vector is isolated in a vicinity where switching for commutation in a current-source converter is generated. When the switching in the current-source converter occurs at the isolation period, zero-current switching is realized. When presence of dead time is thus taken into consideration, a width of the timing when the zero-current switching is realized is made to be broader than a case where the presence of the dead time is not taken into consideration by the dead time.