An energy conversion system, comprising a bridge arm conversion module, a direct current, DC/DC conversion module, a motor comprising three phases of windings (U, V, W), a bus capacitor, and a control module, wherein the bridge arm conversion module comprises a first bridge arm switch and a plurality of second bridge arm switches (201, 202, 203) connected in parallel, the first bridge arm switch is connected in parallel to the plurality of second bridge arm switches (201, 202, 203) connected in parallel, and a parallel connection end between the first bridge arm switch and the plurality of second bridge arm switches (201, 202, 203) connected in parallel is used as an input/output end of the bridge arm conversion module, wherein each bridge arm switch (201, 202, 203, 204) comprises an upper bridge arm switch and a lower bridge arm switch connected in series, a series connection point between the upper bridge arm switch and the lower bridge arm switch is a bridge arm midpoint of the corresponding bridge arm switch (201, 202, 203, 204), a bridge arm midpoint of the first bridge arm switch is the first bridge arm midpoint, bridge arm midpoints of the plurality of second bridge arm switches (201, 202, 203) are the other bridge arm midpoints; wherein the first bridge arm midpoint of the bridge arm conversion module is connected to an alternating current charging interface and each bridge arm midpoint of the plurality of second bridge arm switches (201, 202, 203) is connected to one of the three phases of windings (U, V, W) of the motor; wherein the input/output end of the bridge arm conversion module is connected in parallel to the bus capacitor and to a first input/output end of the DC/DC conversion module, a second input/output end of the DC/DC conversion module is connected to a traction battery, a third input/output end of the DC/DC conversion module is connected to an auxiliary battery, a neutral wire of the motor is connected to the alternating current charging interface, the neutral wire of the motor is led out from a common connection end of the three phases of windings (U, V, W), and the alternating current charging interface is connected to a power supply; characterised in that the control module is configured to control a bridge arm switch action in the bridge arm conversion module, to drive the motor based on an alternating current input voltage supplied by the power supply and form a bus voltage (Vbus) at two ends of the bus capacitor, and control the DC/DC conversion module to charge the traction battery and the auxiliary battery based on the bus voltage. wherein the bridge arm conversion module comprises a first bridge arm switch and a plurality of second bridge arm switches (201, 202, 203) connected in parallel, the first bridge arm switch is connected in parallel to the plurality of second bridge arm switches (201, 202, 203) connected in parallel, and a parallel connection end between the first bridge arm switch and the plurality of second bridge arm switches (201, 202, 203) connected in parallel is used as an input/output end of the bridge arm conversion module, wherein each bridge arm switch (201, 202, 203, 204) comprises an upper bridge arm switch and a lower bridge arm switch connected in series, a series connection point between the upper bridge arm switch and the lower bridge arm switch is a bridge arm midpoint of the corresponding bridge arm switch (201, 202, 203, 204), a bridge arm midpoint of the first bridge arm switch is the first bridge arm midpoint, bridge arm midpoints of the plurality of second bridge arm switches (201, 202, 203) are the other bridge arm midpoints; wherein the first bridge arm midpoint of the bridge arm conversion module is connected to an alternating current charging interface and each bridge arm midpoint of the plurality of second bridge arm switches (201, 202, 203) is connected to one of the three phases of windings (U, V, W) of the motor; wherein the input/output end of the bridge arm conversion module is connected in parallel to the bus capacitor and to a first input/output end of the DC/DC conversion module, a second input/output end of the DC/DC conversion module is connected to a traction battery, a third input/output end of the DC/DC conversion module is connected to an auxiliary battery, a neutral wire of the motor is connected to the alternating current charging interface, the neutral wire of the motor is led out from a common connection end of the three phases of windings (U, V, W), and the alternating current charging interface is connected to a power supply; characterised in that the control module is configured to control a bridge arm switch action in the bridge arm conversion module, to drive the motor based on an alternating current input voltage supplied by the power supply and form a bus voltage (Vbus) at two ends of the bus capacitor, and control the DC/DC conversion module to charge the traction battery and the auxiliary battery based on the bus voltage.