The hybrid vehicles are generally divided into three groups according to the hybrid drive:

The series hybrid electric vehicle (SHEV) mainly consists of three powertrain, such as engine, generator, drive motor, etc. it forms the power system of HEV in series.

The engine and generator of the parallel hybrid electric vehicle (PHEV) are all power assemblies. The power of the two power units can be superimposed on each other and can be output separately.

Hybrid electric vehicle (PSHEV) combines the series and parallel structure of the electric vehicles, mainly by the engine, electric generator and drive motor three power assembly.

According to the degree of mixing in hybrid systems, hybrid systems can be divided into the following four categories:

Micro hybrid power system. The models represented are PSA's hybrid version of C3 and TOYOTA's hybrid version of Vitz. In a strict sense, this kind of micro hybrid system does not belong to a real hybrid vehicle because its motor does not provide a sustained drive for the car.

Light hybrid power system. The representative model is a universal hybrid pickup. Light hybrid power system can implement control engine with generator start and stop, but also can be achieved: (1) during deceleration and braking conditions, on the part of energy absorption; (2) in the process of driving, engine isokinetic operation, the energy generated by the engine can be adjusted between the charging demand and demand driven generator wheel. The mixing degree of light hybrid systems is usually below 20%.

Medium hybrid power system. Honda's hybrid Insight, Accord and Civic are part of this system. The hybrid system uses a high voltage motor. In addition, in the hybrid system also adds a function: when the car is accelerating or high load, the motor can drive the wheels to complement the auxiliary, the engine power output, improve the performance of the vehicle so as to better. The system has a high degree of mixing, and can reach about 30%. At present, the technology is mature and widely used. Complete hybrid power system. TOYOTA's Prius and future Estima are fully hybrid systems. The system uses a 272-650v high voltage starting motor, higher mixing degree. Compared with a mid hybrid system, the full hybrid system can achieve even more than 50%. The development of technology will make fully integrated power system gradually become the main development direction of hybrid technology.