Classification of electric drive systems for pure electric vehicles

Focusing on the three-part pure electric vehicle drive technology, the author is sorting out the key technologies in the development process of new energy powertrains to provide a theoretical basis and reference for the design, testing and production of powertrains. The plan is divided into three chapters to analyze the key electric drive technologies in pure electric vehicle powertrains. Today, we will introduce the classification of pure electric vehicle electric drive systems.

Motor drive system definition

According to the vehicle power battery status and vehicle power requirements, the electrical energy output by the on-board energy storage or power generation device is converted into mechanical energy.

The energy is transferred to the drive wheels through the transmission device, and part of the vehicle's mechanical energy is converted into electrical energy and fed back to the energy storage device when the vehicle brakes.

Motor drive system classification

According to the different electric drive systems, they are divided into the following three categories: pure electric vehicles, hybrid electric vehicles, and plug-in hybrid electric vehicles.

1. Pure electric vehicles can be divided into the following four categories according to the motor: single motor drive system, dual motor drive system, hub motor drive system and wheel side motor drive system.

● Working principle of single motor drive system

Features: The motor replaces the engine, keeping the original gearbox and mechanical transmission unchanged.

Advantages: simple structure, low technical content, small changes to the vehicle, high reliability and low cost.

● Working principle of dual motor drive system

Features: The dual-side motors are driven independently, eliminating the gearbox, mechanical drive shaft, and mechanical differential.

Advantages: simple structure, power is flexibly connected by cables, flexible layout, and effective use of space.

● Working principle of wheel hub motor drive system

Advantages: The hub motor has the advantages of high efficiency, energy saving, lightweight and miniaturization, and is the ultimate solution for electric vehicles.

The hub motor integrates power, transmission and braking into the wheel hub, changing the central drive to a distributed drive, eliminating the transmission, drive shaft and differential, reducing 80% of transmission components and reducing its own weight by 30%.

● Wheel side motor drive system

Features: The motors on both sides are driven independently, the motors are on the outside of the wheel hub, and the motors drive the wheels through the reducer.

Advantages: simple structure, effective use of wheel side space, suitable for heavy-duty and high-torque vehicles.

2. Hybrid electric vehicles can be divided into series, parallel and hybrid vehicles according to their layout.

● Series hybrid electric vehicle

Features: Mechanical power flow and electric power flow are connected in series, wheels are driven purely electrically, and the braking energy recovery function is added.

Advantages: simple power flow, convenient energy management, energy saving.

Disadvantages: The system is not compact and the technical content is low. It has been eliminated.

● Parallel hybrid

The parallel type has low technical content, no obvious advantages, and is gradually being eliminated.

● Parallel-parallel hybrid power

It is currently the most commonly used form and is suitable for 4×4 wheeled hybrid vehicles with obvious advantages.

Advantages: It gives full play to the advantages of high mechanical transmission efficiency and compact structure, and mechanical transmission is used in common working conditions; mechanical drive and motor drive exist at the same time, and the vehicle can run as long as one drive mode works normally; it is suitable for multi-wheel drive vehicles, and traditional mechanical transmission is used near the front of the vehicle, with minor changes to the vehicle.

Disadvantages: The addition of generators and generator controllers takes up space and increases costs; the need to match the electric power balance increases the complexity of energy management; the structure is complex and has high engineering requirements.

3. Plug-in hybrid system

According to different configuration forms, plug-in hybrid systems can be divided into series, parallel and hybrid types.

Hybrid power: When the motor participates in the driving for a maximum of about 10%, it is called a mild hybrid; when it accounts for more than 30%, it is called a strong hybrid.

Plug-in hybrid: pure electric driving range is greater than 50km.

● Series plug-in hybrid

● Parallel plug-in hybrid

● Plug-in hybrid

There are currently two main types of hybrid vehicles on the Chinese market: Japan's Toyota's gasoline-electric hybrid solution, and China's plug-in hybrid solution.

● Japan Toyota Solution

Hybrid power is a weak electric hybrid with a pure electric range of 2-3km. Compared with pure internal combustion engines, the cost is 20,000 yuan higher. Due to its fuel efficiency and low operating cost, the market response is good. Toyota Prius is already the fourth generation of cars. It is well-known for its safety and reliability, and its fuel economy is in the leading position in the industry. Fuel consumption is reduced by 13-20%:

1.5L hybrid, official measurement: 5.1L/100km in urban conditions, 4.4L/100km in suburban conditions, comprehensive customer measurement 5-7L/100km. Customer average 7.8L/100km.

● China Solution

Plug-in hybrid vehicles are medium-strong electric hybrids with a pure electric range of 80-120km. Compared with pure internal combustion engines, they cost 30,000 yuan more. With government subsidies, they are gradually gaining market recognition. Fuel consumption: urban conditions, pure electric drive, suburban conditions, hybrid drive.