800V high voltage system

1.  800V What is it?

800V The name of high-voltage system comes from the electrical angle of the whole vehicle . At present, the voltage range of high-voltage electrical system of mainstream new energy vehicles is generally 230V-450V, Median value 400V, It is generally called 400V System ; With the application of fast charging , The voltage range of the high-voltage electrical system of the whole vehicle reaches 550-930V, Median value 800V, It can be collectively referred to as 800V System .

800V The typical feature of high voltage system is voltage platform . The core of fast charging technology is to improve the charging power of the whole vehicle , To improve the charging power of the whole vehicle , In terms of technical means, either increase the charging current or increase the charging voltage , An increase in charging current means a thicker and heavier harness 、 More heating capacity and more auxiliary equipment bottlenecks , While the charging voltage increases, there is a greater degree of design freedom , This directly promotes 400V The voltage platform is facing 800V Voltage platform conversion .

400V Electronic and electrical architecture （ source ：EDC Electric drive future ）

800V Electronic and electrical architecture （ source ：EDC Electric drive future ）

400V Under branch , Most benchmarking companies have gone from 150kW Go to 200kW Start working , and 800V Fast charging design , Also started from 350A The watershed of , Go to 500-600A More current to design .

400V The evolutionary path of fast charging （ source ： Wangcai power assembly ）

800V The evolutionary path of fast charging （ source ： Wangcai power assembly ）

 

2019 year 4 Month Porsche Taycan Turbo S Global launch ,800V The world's first pure electric vehicle was born . On the performance , The maximum charging power can reach 320kW General 120kW Fast filling pile 2~3 times ; High voltage power battery , Front drive motor , Rear drive motor , On board charger and PTC All components adopt 800V Voltage platform .

 

2020 year 12 month 2 Japan , Hyundai Motor Group launched a new special platform for electric vehicles all over the world “E-GMP”, This platform can also realize 800V function . On the performance , Maximum charging power 350kW, Support battery charging by 10% To 80% Only 18min; All components include high-voltage power battery , Front drive motor , Rear drive motor , Battery heater , Cabin heater and high-pressure air conditioner , All adopted 800V Voltage platform .

 

 

2.  800V advantage

First of all , Charging power can be higher , Eliminate charging time anxiety .

During the popularization of new energy vehicles , Endurance and charging speed are two shortcomings . Compared with fuel vehicles , The range of most new energy vehicles is lower than 600 km , Generally lower than the range of fuel vehicles , It is difficult to meet the demand for long-distance driving between cities . On the other hand , Existing charging technologies require consumers to wait 40 Minutes or more to fill , The refueling process of fuel vehicles only needs 5 minute , In contrast, the energy replenishment efficiency is lower .400V Under the system 200kW About the charging power will become the limit of many vehicle designs , and 800V High voltage system can break the limit to 400kW, In this case, if the battery of the long-range vehicle [email protected]%-80% Charge , Only 9 minute , Basically equal to the refueling time of traditional fuel vehicles , Completely eliminate the anxiety of charging time .

Charging power of different voltage platforms （ source ： Wangcai power assembly ）

 

second , The cost of fast charging system is low .

Based on 400V Fast charging of the system , but 800V High voltage system can achieve lower system cost in high-power charging applications . In the short term 800V Charge 250kW The above charging power segment , The long term 800V Charge 150kW The above charging power segment ,800V High voltage system has obvious system cost advantage .

Third , Fast charging, low charging loss .

comparison 400V System ,800V The charging current of the high-voltage system is small , Battery loss , Harness loss and charging pile loss can be reduced , Realize charging energy saving . According to the power 、 voltage 、 Current relation formula 𝑄 = 𝑈𝐼, Other conditions remain unchanged , Any increase in the charging voltage or current can improve the charging efficiency .

Fourth , Low energy consumption in vehicle driving , The battery capacity can be reduced and the assembly cost can be reduced under the same battery capacity .

comparison 400V System , One of them 800V High voltage system battery 、 Electric drive and other high-voltage components have low current , The loss of relevant components and harness can be reduced ; Both are accompanied by the introduction of the third generation semiconductor silicon carbide Technology , The energy consumption of high-voltage components, especially electric drive components, can be greatly reduced , Realize energy-saving driving of vehicles .

3.  How to adapt to 800V High voltage platform

3.1  SiC High pressure resistance 、 High temperature resistance 、 The advantage of high frequency , It's just for 800V The platform is tailored

Why do silicon carbide semiconductors have more advantages than silicon semiconductors ？

Silicon carbide has significant performance advantages at the power semiconductor level . Compared with silicon semiconductor , The band gap width of silicon carbide is that of silicon 3 times , Make it have the ability to work stably under high temperature ; The electric field strength of silicon carbide is that of silicon 15 times , Make its conduction impedance low , The conduction energy consumption is reduced ; The electron saturation rate of silicon carbide is that of silicon 2 times , It can have faster switching speed , Reduce switching energy consumption ; The thermal conductivity of silicon carbide is that of silicon 3.5 times , Bring better heat dissipation performance .

 

These advantages contribute to the design optimization of high-voltage components and vehicle optimization , It is mainly reflected in the following two aspects ：

First of all , Silicon carbide MOSFET It can greatly improve the efficiency of inverter and electric drive , Reduce vehicle energy consumption .

comparison 400V System silicon IGBT, No matter what 400V System or 800V High voltage system , Silicon carbide MOSFET Inverter losses can be reduced 50% about , Improve the efficiency of electric drive and then reduce the energy consumption of the whole vehicle . Energy consumption analysis of vehicles at different levels ( Pictured 2) Show ： from A00 Level to large SUV Level , Silicon carbide MOSFET Electric drive products can reduce the power consumption of the whole vehicle 5%-7% That is, the battery life of the same capacity battery increases by at least 5%, Looking at the data may be a little misleading , To say human words is to save money .

 

second , Silicon carbide MOSFET stay 800V There are almost irreplaceable advantages in the application of high-voltage electric drive system .

With high withstand voltage IGBT Impedance increases , Frequency performance decreases , from 400V The system rises to 800V After the system , At the same frequency ,Si-IGBT Conduction loss of device 、 Switching losses have increased significantly , If in 800V In the field of high-voltage system, silicon IGBT Technical route , There will be the problem of rising costs but declining efficiency . So in the moment 800V High voltage electric drive , Silicon carbide MOSFET It is the only option of high-efficiency electric drive .

3.2  800V What changes will happen to the architecture of automotive systems under high voltage systems ？

With the blessing of silicon carbide Technology 800V High voltage system has many advantages , Judging from the trend 800V High voltage system will become a high-power charging technology in the future （>200kW） The mainstream solution of .

however , The development of technology is not achieved overnight , Affected by the inertia of the industrial chain ,800V Charging pile and 800V Vehicle mounted high-voltage components and other supporting facilities are not perfect in the short term , Not enough to support the ultimate 800V Rapid promotion of high voltage system , At present, we need to focus on two points ： compatible 400V Charging pile and 800V Charging point application ; Compatible with some 400V On board component application . This leads to five different 800V Design scheme of vehicle system architecture under high voltage system , The following table ：

 

3.3  800V Is there any change in the three electricity system under the high voltage system architecture , How to ensure safety and reliability ？

（1） Common withstand voltage insulation design challenges of three electrical components ：

Conventional design , The electrical clearance related to the main power circuit of one electrical component 、 The creepage distance should be redesigned ; The signal isolation circuit of both high and low voltage components also needs to be redesigned to deal with the problem of withstand voltage insulation ; The three use insulation materials with higher voltage resistance . Special design , For example, it involves electricity 、 magnetism 、 heat 、 Motor components with mechanical and other factors , There may be partial discharge problems .

（2） Battery pack technology challenges ：

After the charging power is increased , The charging rate of the cell will be determined by 1C Upgrade to >=3C. Under high charging rate , On the one hand, it will cause the loss of active substances , Affect battery capacity and life ; On the other hand , Once lithium dendrites pierce the diaphragm , It will cause internal short circuit of the battery , Cause fire and other safety risks .

（3） Motor technology challenges ：

After the DC bus voltage increases , The insulation distance of the motor increases more , Additional insulation design needs to be considered , At the same time, high voltage will cause “ corona ” The phenomenon produces , How to ensure full life electric fatigue is a double test of cost and Technology . In addition, due to the increase of voltage , Changed the original 400V Motor power torque ratio , Need to re 800V Design electromagnetic scheme , It is bound to increase production line investment . In addition, there is the challenge of increasing the risk of failure caused by shaft current . In general , stay 800V Under the architecture , How to meet customers' torque at a lower cost 、 Power and efficiency requirements , Need a certain technical threshold , It's a huge challenge .

（4） Technical challenges of motor controller ：

First ,800V High power density must be considered in the design of motor controller 、 High heat resistance 、 Product reliability in high frequency switching applications . secondly , With 800V Voltage and frequency increase of silicon carbide inverter , Inside the inverter du/dt A substantial increase , This brings inverter EMC The great challenge of design .

（5） Other component technical challenges ：

800V OBC、800V DCDC、800V Battery high voltage relay / Fuse / The connector 、 Charging piles, etc. need to be upgraded , This brings great challenges to the automotive R & D designers .

Reference resources ：

1. Wangcai power assembly ： Reading | Technical analysis of high voltage platform

2. Wangcai power assembly ：800V High voltage platform , Can cure and tonify anxiety ？

3.EDC Electric drive future ： Electric vehicle 800V High voltage platform technology

4.EDC Electric drive future ：800V Analysis of driving force and system architecture of high voltage system —— Why 800V High voltage system , And its challenges ？