according to one embodiment , a vehicle drive system has an engine to generate torque . the vehicle drive system has an alternator coupled to the engine . the alternator converts torque from the engine to magnetic flux and generate an ac voltage . the vehicle drive system has a pwm converter coupled to the alternator to convert ac voltage from the alternator to dc voltage . the vehicle drive system has a pwm inverter which is connected with the pwm converters , the pwm inverter is to transform dc voltage to ac voltage . the vehicle drive system has a filter capacitor between the pwm converter and the pwm inverter . the filter capacitor is configured to be charged by the pwm converter .