Mar 08, 2020
Pure electric vehicle is powered by power battery. Its electrical system includes high voltage electrical system, low voltage electrical system and can communication information network system. This paper briefly introduces the composition and development trend of high voltage electrical system.
>>>>Composition of high voltage electrical system
In pure electric vehicles, high-voltage electrical system is mainly responsible for starting, driving, charging and discharging, air conditioning power, etc. It mainly includes battery system, power assembly, high-voltage electric control system, charging system, high-voltage equipment and harness system.
High voltage electrical system of pure electric vehicle
Pack assembly of power battery: the “heart” of electric vehicle, providing energy for all systems of the vehicle. When the electricity is consumed, it also needs to be charged. The power battery is high-voltage direct current, its working voltage is generally 100-400v, and its output current can reach 300A. Ternary lithium battery is the mainstream at present.
Generally speaking, electric vehicle power battery pack consists of the following parts: power battery module, structural system, electrical system, thermal management system, battery management system (BMS).
The power assembly of electric vehicle is mainly composed of drive motor and motor controller (MCU).
Motor controller MCU: converts high-voltage direct current to alternating current, and interacts with vehicle controller and other modules to realize effective control of driving motor.
Drive motor: according to the command of the motor controller, convert the electric energy into mechanical energy and output it to the transmission system of the vehicle. At the same time, the mechanical energy (such as braking efficiency) generated during driving can also be converted into electrical energy, which is transmitted to the power battery through the on-board charger. At present, the main driving motors are permanent magnet synchronous motor and three-phase AC asynchronous motor (Tesla).
High voltage electric control system
High voltage distribution box (PDU): a power distribution device for high voltage of the whole vehicle, similar to the electrical fuse box in the low-voltage circuit system.
Maintenance switch: between the power battery and PDU, when the power battery is maintained, it can be used to cut off the high voltage of the whole vehicle to ensure the maintenance safety. It is also integrated on PDU
Voltage converter (DC / DC): converts the high-voltage direct current of the power battery into the low-voltage direct current required by the electrical appliances of the vehicle, and supplies the battery to maintain the power balance of the vehicle.
On board charger (OBC): a device that converts alternating current to direct current.
Under the influence of vehicle layout, more and more vehicle models tend to integrate DC / DC and OBC into a two in one controller, or even integrate PDU, DC / DC and OBC into a three in one controller.
Fast charging port: input high-voltage DC, can directly charge the power battery through PDU.
Slow charging port: input high-voltage AC, need to be converted through OBC, and then charge the power battery through PDU.
High voltage equipment
The electric equipment on the electric vehicle mainly includes the power steering system, braking system, electric air conditioning and electric heating equipment.
Power steering system: it is composed of variable frequency drive and power steering pump to assist the vehicle to turn the steering wheel and reduce the burden of driving the vehicle.
Braking system: it is composed of variable frequency drive and electric air compressor, which provides compressed air for braking system and suspension system to realize braking function.
Electric air conditioning compressor and PTC heater: in order to adjust the temperature of the interior space of the vehicle, the electric vehicle is equipped with a cold and warm air conditioner or the air conditioner is equipped with PTC heating. Air conditioners and heaters are the big consumers of electric vehicles.
All parts of the electric system of the electric vehicle are connected by wire harness, including high-voltage wire harness and low-voltage wire harness.
High voltage harness is the medium of high-voltage power transmission, which can be regarded as the “big artery” of electrical system. It continuously transmits the power of power battery system “heart” – power battery to all required components.
The low-voltage harness can be regarded as the “neural network” and “capillary” of the electrical system. In addition to meeting the function of the traditional fuel vehicle harness, it is also responsible for the realization of the function of the strong current control unit module.