Traction motor systems of hybrid electric vehicles are vulnerable to uncontrolled generation (UCG) when the inverter switches loss their drive signals suddenly during flied weakening high speed operation. Then the large current is induced by UCG and charges the battery. The current will lead to the temperature rise of the battery and even break it down. Therefore, in order to avoid destruction risk of the battery, this paper proposes a leakage resistance and a stored energy capacitor, to effectively deal with UCG. Furthermore, control strategies are developed to improve the charging efficiency of the battery and maintain the operation of the battery in appropriate temperature.