According to the connection mode of hybrid drive, hybrid vehicles are generally divided into three categories:
① Series hybrid electric vehicle (SHEV) mainly consists of three power trains including engine, generator and drive motor in series to form the power system of HEV.
② The engine and drive motor of a parallel hybrid electric vehicle (PHEV) are both powertrains, and the power of the two powertrains can be superimposed on each other or output separately.
③ Hybrid hybrid electric vehicle (PSHEV) is an electric vehicle composed of a series and parallel structure. It is mainly composed of three power trains: engine, motor-generator and drive motor.