An energy conversion system, an energy conversion method, and a power system. The energy conversion system may include a bridge arm conversion module, a direct current to direct current (DC/DC) conversion module, a motor, a bus capacitor, and a control module. The control module may be configured to control a bridge arm switch action in the bridge arm conversion module, drive the motor based on an alternating current input voltage supplied by a power supply, form a bus voltage at two ends of the bus capacitor, and control the DC/DC conversion module to charge a traction battery and an auxiliary battery based on the bus voltage. The traction battery and the auxiliary battery can be charged while the motor is driven, thereby achieving higher energy conversion efficiency, low costs, and strong applicability.