POWERTRAIN SYSTEM

A powertrain system includes an electric motor for driving a vehicle; a battery; an internal combustion engine; an electric generator; a motor inverter connected in parallel to the battery, and converting DC electric power of the battery into AC electric power and supplying it to the electric motor; a generator inverter connected in parallel to the battery, and converting AC electric power generated by the electric generator into DC electric power and supplying it to the battery; and a control device. The control device is configured, where a charging rate of the battery is not greater than a first threshold value, and a ripple current that is generated in association with an operation of the motor inverter and flows into the battery is not less than a second threshold value, not to start up the internal combustion engine for electric power generation using the electric generator.