ELECTRIC POWER SYSTEM AND CONTROL METHOD THEREFOR

An electric power system includes a secondary battery configured to supply electric power to a drive motor, configured to generate driving force of a vehicle, and an auxiliary having an auxiliary smoothing capacitor, a secondary battery relay configured to open or close an electrical contact between the secondary battery and the drive motor, a secondary battery smoothing capacitor connected between the secondary battery relay and the drive motor, an auxiliary relay configured to open or close an electrical contact between the secondary battery and the auxiliary, and a control unit configured to control a switching operation of each of the secondary battery relay and the auxiliary relay. The control unit is configured to, at startup of the vehicle, precharge the secondary battery smoothing capacitor by closing the secondary battery relay and then precharge the auxiliary smoothing capacitor by closing the auxiliary relay.