Anatomy of electric vehicle high voltage distribution box (PDU) technology, market and mainstream enterprises

Electric vehicle high voltage distribution box (PDU), also known as high voltage distribution box, is a high voltage system distribution unit. Electric vehicles have the characteristics of high voltage and high current. They are usually equipped with a high voltage system of more than 300V, and the working current can reach more than 200A, which may endanger personal safety and the safety of use of high-voltage components.

Therefore, when designing and planning a high-voltage power system, it is necessary not only to fully meet the requirements of the vehicle's power drive, but also to ensure the safety of the vehicle, the safety of the driver and passengers, and the safety of the vehicle's operating environment.

Generally, high-voltage components related to power batteries, such as contractors and fuses of various circuits, are integrated into a power battery pack.

As the energy storage device of electric vehicles, the power battery is limited by the size and arrangement of the whole vehicle. At the same time, it is necessary to ensure the convenience of maintenance of the power battery system, reduce the number of times of disassembling the power battery pack, and the high voltage box comes into being.

01

working principle

The function of the electric vehicle high-voltage box (PDU) is to ensure the transmission of power and energy of the whole vehicle system, and it is the bridge between the power battery and the power supply and signal transmission of each high-voltage equipment. And at any time to detect the insulation fault, open circuit fault, ground fault and high voltage fault of the entire high voltage system.

In electric vehicles, high-voltage components connected to the high-voltage power distribution box include: power battery, motor controller, frequency converter, inverter power supply, electric air conditioner, electric defrosting, charging stand, and the like.

02

Design principles and structure

In general, the design principle of the high-voltage distribution box is: compact device arrangement, small size, easy to disassemble and assemble. Due to the small space of the cabinet and the large current, the design focuses on the heat dissipation arrangement to avoid potential safety hazards caused by the increase in temperature focusing.

Considering the complexity of the vehicle space, the complexity of the vehicle structure and the cost, the centralized power supply system is widely used in the industry. The high-voltage power supply directly enters the high-voltage power distribution box and is distributed to the system high-voltage electrical products according to the needs of the system. It has the function of ensuring the safety, system insulation, electromagnetic interference, shielding, sealing and vibration resistance of the entire high-voltage system and its various electrical equipment. Very high demand.

Before the large-scale popularization of electric vehicles, there are still many improvements in the design and technology of high-voltage distribution boxes. Most of the high-voltage power distribution boxes on the market use the design concept of industrial high-voltage distribution boxes, and their safety, reliability and durability can not meet the requirements of automobiles.

For example, for high-power capacitive loads like motor drivers and voltage-converting devices (DC/DC), pre-charge processing and status monitoring are required. Traditional electric circuits are difficult to monitor effectively, and it is easy to cause damage to high-voltage switch parts (such as terminal sticking).

The industry often uses a product with relatively high electrical parameters to solve this problem, but it is not satisfactory in terms of size and cost.

At present, strong domestic and foreign enterprises have begun to develop intelligent high-voltage distribution boxes, generally adopting cast aluminum casings and connectors. The protection level reaches IP67. It has current and voltage acquisition functions. It has high-voltage connection monitoring and insulation monitoring. It has a high-voltage safety management function. High-voltage power distribution management function with pre-charging function.

In the future, high-voltage distribution boxes will develop in the direction of small size, light weight and intelligence.

03

The main components

Electric vehicle high-voltage power distribution box contains bronze, circuit breaker, air open, contractor, soft start, frequency converter, transformer, contractor, high voltage relay, fuse, surge protector, transformer, ammeter, voltmeter, conversion Switch, etc. (For the analysis of various component markets and enterprises, please refer to the “2015-2022 China New Energy Vehicle Core Parts Industry Investment Prospect Report” published by the public.

1, high voltage relay

The main circuit voltage of new energy vehicles is generally greater than 200V, which is much higher than that of conventional vehicles. In addition to the low voltage relays required by conventional vehicles, new energy vehicles also need special high-voltage DC relays. Each new energy vehicle requires 5-8 high-voltage DC relays – 2 main relays, 1 pre-charger, 2 fast chargers, 2 normal charging relays and 1 high-voltage system auxiliary machine relay.

The electric circuit in the electric vehicle belongs to high-voltage direct current, and the general relay cannot meet the requirements. Currently, the most used ones are vacuum type and gas-filled type relays.

Vacuum is the ideal insulation. Since the high voltage arc is generated by the ionization of the insulating medium, and the vacuum itself has no medium, there is good isolation between the contacts. The complete vacuum state is only an ideal state, and some residual oxygen will remain. The oxygen will form copper oxide in the case of arc and the copper electrode, the contact resistance will increase, and the relay has a risk of failure.

At present, the main application is gas-filled relays. The main arc-extinguishing solutions for gas-filled relays are hydrogen and nitrogen. It is filled with pure hydrogen, and the deflection magnet is used to assist arc extinguishing. Compared with vacuuming and nitrogen filling, the hydrogen insulation performance is good and it is difficult to ionize.

Compared with traditional relays, high-voltage DC relays for new energy vehicles have high technology content and complicated production processes. From the perspective of the global market structure, the high-voltage DC relay brand has a high concentration.

The production and research of products in this field are mainly concentrated in foreign companies, and the Chinese market is dominated by multinational companies. The main companies are Tyco, Panasonic, Omron and Bosch.

In recent years, domestic brands have also begun to be applied to new energy vehicles. Hongfa, Songchuan, National, Sanyou Lianzhong, Aerospace Electric, Ningbo Ford and other companies have products, among which Hongfa is a domestic dominant brand, ranking first in domestic enterprises.

In addition, domestic new energy vehicles such as BYD also develop and produce relays.

2, high voltage connector

According to the statistics of the public consultation, in terms of the global connector market, the market concentration is relatively high, and it is basically occupied by the United States, Japan, Taiwan and other countries and regions. The world's top ten Dalian machine manufacturers account for more than 60%, and the Tyco family accounts for more than 60%. More than 20%.

Relatively speaking, Chinese manufacturers are mainly positioned in low-end and mid-range products. The top ten domestic manufacturers have a market share of only 18% in China, and there is a big gap between industry concentration and foreign markets.

In the future, with the rapid development of new energy vehicles, communications, military, etc., Chinese manufacturers will have a large import substitution space in the future, and some areas (such as new energy vehicle connectors) may even be overtaken.

In terms of the domestic market, there are more than 1,000 connector manufacturers in China, including about 300 foreign-invested companies and about 700 local companies. Mainly concentrated in the Yangtze River Delta and the Pearl River Delta region. The development of China's connector market is unbalanced. Most enterprises are small in scale, single product types, new product development lags, and homogenization competition are serious, resulting in fierce market competition and a decline in the gross profit margin of manufacturers.

Electric vehicle auto connectors are different from traditional industrial and traditional automotive connectors. Traditional connector devices are difficult to meet their high current and high voltage requirements, so connector manufacturers are also deploying high-power connection products for new energy vehicles. In the field of high-voltage connectors, the advantages of international companies are obvious, but in recent years, domestic high-end products have also formed a certain industrial base, and gradually mastered advanced technology, and initially formed a strong competitive advantage.

At present, high-voltage connector manufacturers that can supply in bulk in China include: AVIC Optoelectronics, Yonggui Electric, Basba, Jiangsu Ruicheng, etc. In recent years, second-tier enterprises have also begun to grow. From the perspective of sales scale, China's gradually growing enterprises have gradually emerged in the domestic market. (For a detailed analysis, please refer to the “2017-2022 China New Energy Vehicle High Voltage Connector Market and Enterprise Research Report”.

3, high voltage wiring harness

The high-voltage harness is a key component in the electric vehicle's connectors and cables throughout the operation of the vehicle. The hidden dangers of the high-voltage harness are mainly overheating or burning, and the harsh environment should also have shielding performance and water intake. Dust risk and so on. Unlike conventional automotive 12V harnesses, high-voltage harnesses also need to consider magnetic compatibility with the vehicle's electrical system.

In actual use, the electromagnetic interference of electric vehicles is nearly 100 times that of conventional internal combustion engine vehicles. The high-voltage harness of electric vehicles is a highly efficient electromagnetic interference transmitting antenna and receiving antenna, which is the most important reason for the electromagnetic compatibility failure and radiation interference of electric vehicles exceeding the regulatory requirements.

The magnetic interference produced by the high-voltage harness will affect the integrity and accuracy of the data transmission in the vehicle signal line, which will affect the handling and safety of the vehicle in severe cases. Therefore, in the outside of the high-voltage wire harness, it is often used to inject glue and wrap the shielded wire to reduce the magnetic interference to the whole vehicle. The EU also regulates the content of 6 substances such as lead, mercury and cadmium contained in automotive wiring harnesses, and requires RoHS certification.

China has no uniform standard for voltage and high voltage wiring harness. The previously implemented GB/T25085, GB/T25087 "60-600V low voltage cable for road vehicles" was born out of IS06722, for single or multi-core cable with rated voltage of 60-600V. Regulations and requirements have been made, but there are always gaps and gaps in standards for high-voltage cables of 600V or higher used in new energy vehicles.

In August 2016, the Ministry of Industry and Information Technology approved the release of the automotive industry standard QC/T 1037-2016 "High-voltage cable for road vehicles", which was officially implemented on September 1, 2016. This standard specifies the requirements, test methods, inspection rules, packaging and marking of high-voltage cables for road vehicles with rated voltages AC 1000 V/DC 1500 V and below.

In the 1980s, Japan's Yazaki and Sumitomo began to develop special high-voltage wire harnesses for Japanese auto companies. In the 1990s, Delphi in the United States began to develop high-voltage wire harness products for GM, and South Korea's LS supplied high-voltage wire harness products for LG.

From the technical point of view, the high-voltage harnesses of Japan and the United States have formed a system, and have been verified and continuously improved in actual use, and the technology is leading domestic enterprises for 20-30 years. (For a detailed analysis, please refer to the “2017-2022 China New Energy Vehicle High Voltage Wire Harness Market and Enterprise Research Report”.

4, fuse

Fuses are used for AC and DC applications, and AC is used in industrial power distribution systems. The lithium battery, storage capacitor, motor, converter and electronic control circuit of the vehicle are all DC systems. All need DC type fuses for short circuit protection to ensure safe and reliable normal operation and super short-circuit breaking effect.

In the electric vehicle high-voltage power distribution box, the output terminal is mainly connected to the auxiliary power supply system of the automobile. In the general case of the power distribution box, the electric heating fan branch, the air-conditioning compressor branch, the DC/DC branch and the charger branch are generally included.

On these four branches, each branch needs to be equipped with a line protection fuse. The purpose is to cut off the power protection circuit in time when each load is short-circuited to avoid vehicle fire.

The fuse has been widely recognized and used in large quantities due to its small size, good seismic resistance and low price. It has become a recognized main component of electric vehicle short-circuit protection at home and abroad.

According to the fuses currently used in the electric vehicle industry, the maximum voltage of most models is generally less than 700VDC, and a few models will be slightly higher than this voltage, so the fuses for battery protection can be divided into 500VDC and 700VDC. Mainly, the current level is mostly 200A~400A. (For a detailed analysis, please refer to the “2017-2022 China New Energy Automobile Fuse Market and Enterprise Research Report” published by the public.

04

Summary

The main core components of the high-voltage distribution box belong to high-voltage components, and the technical content is high. Foreign companies have strong competitive advantages, and some domestic enterprises assemble by purchasing foreign components. Large-scale high-voltage distribution box enterprises at home and abroad can provide more than 60% of core components.

The scale and standards of high-voltage distribution boxes are generally dominated by car companies, and high-voltage distribution boxes and component companies develop and produce according to the needs of car companies. However, at present, many high-voltage distribution boxes for electric vehicles in China follow the design concept of industrial high-voltage distribution boxes, and at the same time, there is a lack of relevant standards. The enterprises are in a variety of products, and the products are of various types and the quality is uneven.

With the gradual maturity of the new energy vehicle market, the requirements for related technologies are also getting higher and higher. In the next few years, technology competition will become the main promotion factor of the PDU industry.