The key to hybrid vehicles is the hybrid power system, and its performance is directly related to the performance of the hybrid vehicle. After more than ten years of development, the hybrid power system assembly has evolved from the original discrete structure of the engine and the motor to the integrated structure of the engine, motor and gearbox, that is, the integrated hybrid power system. Hybrid vehicles are driven by electric motors as auxiliary power for the engine.
Parallel-parallel hybrid electric vehicle structure
1. Structure
The hybrid drive system can work in series hybrid mode or parallel hybrid mode, that is, a combination of the two modes. This requires two motors, a relatively complex transmission system and an intelligent control system.
The working principle of the hybrid drive system is as follows: part of the power generated by the engine is transmitted to the drive wheel through the power splitter (power distributor) through the mechanical transmission system, and the other part drives the generator to generate electricity, and the generated electric energy is transmitted to the motor or battery. The torque of the motor can also be transmitted to the drive wheel through the transmission system. The general control strategy of the hybrid drive system is: when the car is driving at low speed, the drive system mainly works in series; when the car is driving at high speed and stably, it is mainly in parallel.
The structural form and control method of the hybrid hybrid drive system give full play to the advantages of series and parallel, which can make the engine, generator and other components more optimally matched, and structurally ensure that the system works in the optimal state under more complex working conditions, so it is easier to achieve the control goals of emissions and fuel consumption. Compared with the parallel type, the hybrid type has a more complex power compound form, so it puts forward more requirements on the power compound device in terms of mechanical structure and control. The current hybrid structure generally uses a planetary gear mechanism as a power compound device.
II. Features
1. Advantages
1) Compared with series hybrid vehicles, the power system is smaller and the cost is reduced. The hybrid hybrid vehicle is based on the parallel hybrid vehicle, and then adds an electric motor/generator or a drive motor. Therefore, the hybrid hybrid vehicle consists of three powertrains, which drive the vehicle with 50-100% power, but the power, mass and volume are smaller than those of the series hybrid vehicle powertrain.
2) Multiple working modes to obtain better performance. The hybrid hybrid vehicle has a variety of driving modes to choose from, including series drive and parallel drive, so that the working state of the engine can choose the optimal mode in a variety of working conditions.
3) The engine participates in the drive to reduce energy conversion losses. The engine drive mode is one of the basic drive modes of the hybrid electric vehicle. In the process of power transmission from the engine to the wheels, except for friction loss, there is no conversion process of mechanical energy-electrical energy-mechanical energy. The comprehensive efficiency of energy conversion is higher than that of internal combustion engine vehicles.
4) Pure electric driving reduces emissions. The pure electric motor drive mode is also one of the basic drive modes of the hybrid electric vehicle. It can independently drive the vehicle. When the vehicle starts and starts, the characteristics of the low speed and high torque of the electric motor are used to drive the vehicle to start and achieve "zero pollution" driving.
2. Disadvantages
1) The emission of the engine participating in the drive is inferior to that of the series hybrid electric vehicle under special working conditions, and the performance of the hybrid electric vehicle is closer to that of the internal combustion engine vehicle. The working condition of the engine will be affected by the driving condition, and the emission of harmful gases from the engine is higher than that of the series hybrid electric vehicle.
2) The structure is complex and difficult to arrange. The hybrid electric vehicle needs to be equipped with two drive systems. The engine transmission system needs to be equipped with a clutch, a transmission, a drive shaft and a drive wheel. In addition, there are electric motors/engines, drive motors, reducers, power battery packs, and multi-energy power combinations or special devices for coordinating engine drive and drive motor drive. Therefore, the multi-energy power system structure of the hybrid electric vehicle is complex and the overall layout is more difficult.
3) The requirements for the multi-energy control system of the whole vehicle are higher and more complex. There are different combinations of multi-energy power matching and combination, and a complex multi-energy powertrain control system needs to be assembled to achieve high economy and "ultra-low pollution" control goals.
3. Working mode
The hybrid electric vehicle has both parallel and series hybrid electric vehicle working modes.
1) Pure electric drive. Using the battery's electrical energy, the car is driven by the drive motor alone.
2) Series drive. One is the low-speed range, high-power driving conditions, such as continuous climbing, etc. At this time, according to the working conditions, it is driven by the motor, which will consume a lot of electricity and require the engine to replenish the battery. When the car is driving in series drive mode, the engine works in the economic zone and outputs constant power.
3) The engine is driven alone. This situation is the same as the working condition of traditional cars, so it is suitable for the engine economic speed area, that is, the cruising speed at this time.
4) Driving charging. Generally, it works in the engine medium speed area, and the engine power load at this time is low and the efficiency is low. This mode is used to increase the engine's workload, thereby improving the engine's working efficiency and replenishing energy for the battery.
5) Parking charging. When the battery charge state is lower than the set limit, the parking charging mode is adopted. The engine drives the ISG motor to generate electricity in the economic area by outputting constant power to replenish energy for the battery.
6) Braking energy recovery. When the car brakes, the wheels provide reverse torque to drive the drive motor to generate electricity as a generator to recover energy. By recovering braking energy, hybrid vehicles can control fuel consumption and emissions well. This mode works under medium and high speed gliding and braking conditions.
7) Parallel drive. The engine and the motor work at the same time, which can provide a large power output, so this mode is usually suitable for working in medium and low speed acceleration and high speed areas.
8) Full acceleration. The engine, generator and drive motor are driven at the same time. At this time, all the energy is output to drive the car. This mode can obtain the maximum driving force. It is generally used for driving at extreme speeds, overtaking, etc.
The hybrid drive system can work in series hybrid mode or parallel hybrid mode, that is, a combination of the two modes. This requires two motors, a relatively complex transmission system and an intelligent control system.
The working principle of the hybrid drive system is as follows: part of the power generated by the engine is transmitted to the drive wheel through the power splitter (power distributor) through the mechanical transmission system, and the other part drives the generator to generate electricity, and the generated electric energy is transmitted to the motor or battery. The torque of the motor can also be transmitted to the drive wheel through the transmission system. The general control strategy of the hybrid drive system is: when the car is driving at low speed, the drive system mainly works in series; when the car is driving at high speed and stably, it is mainly in parallel.
The structural form and control method of the hybrid hybrid drive system give full play to the advantages of series and parallel, which can make the engine, generator and other components more optimally matched, and structurally ensure that the system works in the optimal state under more complex working conditions, so it is easier to achieve the control goals of emissions and fuel consumption. Compared with the parallel type, the hybrid type has a more complex power compound form, so it puts forward more requirements on the power compound device in terms of mechanical structure and control. The current hybrid structure generally uses a planetary gear mechanism as a power compound device.
II. Features
1. Advantages
1) Compared with series hybrid vehicles, the power system is smaller and the cost is reduced. The hybrid hybrid vehicle is based on the parallel hybrid vehicle, and then adds an electric motor/generator or a drive motor. Therefore, the hybrid hybrid vehicle consists of three powertrains, which drive the vehicle with 50-100% power, but the power, mass and volume are smaller than those of the series hybrid vehicle powertrain.
2) Multiple working modes to obtain better performance. The hybrid hybrid vehicle has a variety of driving modes to choose from, including series drive and parallel drive, so that the working state of the engine can choose the optimal mode in a variety of working conditions.
3) The engine participates in the drive to reduce energy conversion losses. The engine drive mode is one of the basic drive modes of the hybrid electric vehicle. In the process of power transmission from the engine to the wheels, except for friction loss, there is no conversion process of mechanical energy-electrical energy-mechanical energy. The comprehensive efficiency of energy conversion is higher than that of internal combustion engine vehicles.
4) Pure electric driving reduces emissions. The pure electric motor drive mode is also one of the basic drive modes of the hybrid electric vehicle. It can independently drive the vehicle. When the vehicle starts and starts, the characteristics of the low speed and high torque of the electric motor are used to drive the vehicle to start and achieve "zero pollution" driving.
2. Disadvantages
1) The emission of the engine participating in the drive is inferior to that of the series hybrid electric vehicle under special working conditions, and the performance of the hybrid electric vehicle is closer to that of the internal combustion engine vehicle. The working condition of the engine will be affected by the driving condition, and the emission of harmful gases from the engine is higher than that of the series hybrid electric vehicle.
2) The structure is complex and difficult to arrange. The hybrid electric vehicle needs to be equipped with two drive systems. The engine transmission system needs to be equipped with a clutch, a transmission, a drive shaft and a drive wheel. In addition, there are electric motors/engines, drive motors, reducers, power battery packs, and multi-energy power combinations or special devices for coordinating engine drive and drive motor drive. Therefore, the multi-energy power system structure of the hybrid electric vehicle is complex and the overall layout is more difficult.
3) The requirements for the multi-energy control system of the whole vehicle are higher and more complex. There are different combinations of multi-energy power matching and combination, and a complex multi-energy powertrain control system needs to be assembled to achieve high economy and "ultra-low pollution" control goals.
3. Working mode
The hybrid electric vehicle has both parallel and series hybrid electric vehicle working modes.
1) Pure electric drive. Using the battery's electrical energy, the car is driven by the drive motor alone.
2) Series drive. One is the low-speed range, high-power driving conditions, such as continuous climbing, etc. At this time, according to the working conditions, it is driven by the motor, which will consume a lot of electricity and require the engine to replenish the battery. When the car is driving in series drive mode, the engine works in the economic zone and outputs constant power.
3) The engine is driven alone. This situation is the same as the working condition of traditional cars, so it is suitable for the engine economic speed area, that is, the cruising speed at this time.
4) Driving charging. Generally, it works in the engine medium speed area, and the engine power load at this time is low and the efficiency is low. This mode is used to increase the engine's workload, thereby improving the engine's working efficiency and replenishing energy for the battery.
5) Parking charging. When the battery charge state is lower than the set limit, the parking charging mode is adopted. The engine drives the ISG motor to generate electricity in the economic area by outputting constant power to replenish energy for the battery.
6) Braking energy recovery. When the car brakes, the wheels provide reverse torque to drive the drive motor to generate electricity as a generator to recover energy. By recovering braking energy, hybrid vehicles can control fuel consumption and emissions well. This mode works under medium and high speed gliding and braking conditions.
7) Parallel drive. The engine and the motor work at the same time, which can provide a large power output, so this mode is usually suitable for working in medium and low speed acceleration and high speed areas.
8) Full acceleration. The engine, generator and drive motor are driven at the same time. At this time, all the energy is output to drive the car. This mode can obtain the maximum driving force. It is generally used for driving at extreme speeds, overtaking, etc.
