In addition, in this embodiment of this application, the two bridge arms of the three-phase bridge arm converter 302 may further be used as two bridge arms of an inverter, that is, the two bridge arms of the three-phase bridge arm converter 302 may be connected to the secondary-side winding of the transformer 304, to invert a direct current at the direct current port to an alternating current and transmit the alternating current to the transformer 304. Therefore, the three-phase bridge arm converter 302 in this embodiment of this application has two functions: One is to serve as a three-phase inverter by using the three bridge arms to provide electric energy for the motor winding 303, and the other is to serve as a two-phase inverter to deliver electric energy to the transformer 304. In actual application, the three-phase bridge arm converter 302 may provide optionality for the foregoing two functions by using two switch groups (a first switch group 307 and a second switch group 308). As shown in FIG. 3a, the two bridge arms of the three-phase bridge arm converter 302 may be connected to the secondary-side winding of the transformer 304 through the first switch group 307, and connected to the motor winding 303 (which may be specifically two windings of the motor winding 303) through the second switch group 308.