Hybrid Electric Vehicle

Hybrid electric vehicles have three types of arrangement: series, parallel, and hybrid. 
1、 Series connection refers to the engine driving a generator to generate electricity, and its electrical energy is directly transmitted to the electric motor through the motor controller, which generates electromagnetic torque to drive the car. The performance characteristics include: 
(1) The working state of the engine is not affected by the driving conditions of the car, and it always runs stably in its optimal working area. Therefore, the engine has good economy and low emission indicators. 
(2) Due to the use of batteries for driving power "peak shaving", the power of the engine only needs to meet the power required for stable operation of the car at a certain speed, so a lower power engine can be chosen.
(3) There is no mechanical connection between the engine and the drive axle, so there is no requirement for the engine speed. The selection range of engines is large, such as the use of high-efficiency prime movers such as high-speed gas turbines.
(4) There is no mechanical connection between the engine and the electric motor, and the structural layout of the entire vehicle has a large degree of freedom. 
(5) The output of the engine needs to be fully converted into electrical energy and then into mechanical energy to drive the car, requiring a generator and electric motor with sufficient power.
(6) To achieve good generator output power balance and avoid overcharging or discharging of the battery, a larger battery capacity is required.
(7) Generators convert mechanical energy into electrical energy, electric motors convert electrical energy into mechanical energy, and there is energy loss during battery charging and discharging. Therefore, the energy utilization rate output by the engine is relatively low. 
2、 Parallel type refers to the connection between the engine and the drive axle through a mechanical transmission device, and the electric motor is also connected to the drive axle through a power composite device. Cars can be driven by the engine and electric motor together or individually. Its performance characteristics include:
(1) The engine directly drives the car through a mechanical transmission mechanism, resulting in a loss of inorganic electric energy conversion. Therefore, the utilization rate of engine output energy is relatively high. When the driving conditions of the car enable the engine to operate within its optimal operating range, the fuel economy of parallel HEVs is higher than that of series HEVs. 
(2) There is an electric motor for "peak shaving" function, and the power of the engine can also be appropriately reduced. 
(3) When the electric motor is only used as an auxiliary drive system, the power can be relatively small. 
(4) If equipped with a generator, the power of the generator can also be smaller. 
(5) Due to the presence of a generator to supplement electrical energy, a relatively small battery capacity can meet usage requirements. 
(6) Due to the fact that the operating conditions of the engine in a parallel drive system are influenced by the driving conditions of the vehicle, the engine will operate more frequently under its adverse operating conditions when there are many and significant changes in the driving conditions of the vehicle. Therefore, the engine's emissions are higher than those of the series type. 
(7) Due to the direct mechanical connection between the engine and the drive axle, a transmission device is required to adapt to the changes in the driving conditions of the car. In addition, the parallel drive of the engine and electric motor also requires a power composite device. Therefore, the transmission mechanism of the parallel drive system is relatively complex. 
3、 The hybrid drive system is a combination of series and parallel, which refers to the power generated by the engine being transmitted to the drive axle through mechanical transmission, while the other part drives the generator to generate electricity. The structural form and control method of the hybrid drive system fully leverage the advantages of series and parallel, enabling more optimized matching of components such as the engine, generator, and electric motor. This ensures that the system operates in the optimal state under more complex working conditions, making it easier to achieve emission and fuel consumption control goals. 
Disadvantages: The system structure is relatively complex; The fuel saving effect is not significant for long-distance high-speed driving