The residual current protector (RCD) as a leakage protector (RCD) is widely used in low -voltage power distribution systems to prevent electric shock accidents, electrical equipment leakage and electrical fires.Also in the field of electric vehicle charging, RCD is also widely used as a basic electrical protection device.
There are four modes of electric vehicle charging, which is clearly explained in GB / T 18487.1-2015 "Part 1: General Requirement".As soon as the mode is used to connect the charging cable, the electric vehicle is connected to the AC grid. The remaining current protection depends mainly on the remaining current protection device (RCD) in the building distribution box. Since all existing building devices are equipped with RCD, this method isIt is very dangerous and has been prohibited; Mode 2 installed the cable control protection device (IC -CPD) on the charging cable, and the IC -CPD has the surplus current detection protection function insideThe AC grid is directly connected, and a control guide device is installed on a dedicated power supply device. Special power supply equipment is the AC charging pile. When Mode 4 connects the electric vehicle to AC power grid or DC power grid, the DC power supply equipment with the control guide function function is used., That is DC charging pile.Here, we mainly discuss the selection of the remaining current protectors in the four charging piles.
In GB / T 18487.1-2015, it is required that the remaining current protector of the power supply equipment should be adopted by type A or B, which meets the relevant requirements of GB 14084.2-2008, GB 16916.1-2014 and GB 22794-2008EssenceAs shown in Figure 1, the chart of the control circuit scheme of the charging mode 3 controls the circuit, and the remaining current protector is installed inside the power supply equipment.
What is the remaining current protector of Type A or B?my country’s remaining current protection device (RCD) guidance standard GB / Z 6829-2008 (IEC / TR 60755: 2008, MOD) "General Requirements for the remaining current action protector" from the basic structure of the product, the remaining current type, and the deduction Methods and other aspects are divided.According to the remaining current type, RCD can be divided into AC, A, and B.AC -type remaining current protector: For the remaining sine AC current that suddenly applies or slowly rises to ensure the deduction RCD.Type A surplus current protector: Contains the characteristics of AC type and the remaining current of the pulse DC, the pulse DC remains overlay 6mA smooth and the remaining current to ensure the deduction RCD.Type B remaining current protector: contains the protection characteristics of Type A. In addition, it can also communicate with 1000Hz and below sinusoidal surplus current, exchange remaining current superimposed smooth DC current, pulsating DC remain superimposed and smooth remaining current, two or more or moreThe pulsating DC current generated by the phase rectifier circuit, the remaining current of the smooth DC current to ensure the deduction RCD.
At present, because the price of B -type RCD is too expensive, most of the domestic AC charging piles are installed inside the internal of the A -type remaining current protector.The figure below shows the internal structure diagram of the exchange charging pile, and the remaining current protection device is used.
So can the remaining current protector of the type A meet the leakage protection requirements of the charging pile?Let’s analyze the remaining current types that may be generated during the charging process.
As shown in Figure 3, in the process of using the exchange charging pile charging process, the communication charging pile and the vehicle coupling device are connected to the public power grid. If the pile is damaged due to insulation, the leakage current may be generated.In the electric vehicle part, the possible leakage current is mainly from the leakage of the vehicle charger. The general topology of the charger is mainly AC / DC and DC / DC.As shown in the figure below, the main circuit diagram of a common vehicle charger.
Part of the AC / DC single -phase input AC electricity is first filtered through EMI, and then the AC electricity of 85-265V is reorganized into a stable output DC 400V voltage under the action of the Boost APFC circuit, and DC input is provided for the rear level.The DC / DC part uses the main bridge LLC main circuit to convert the DC voltage 400V into a acceptable voltage that can be acceptable.When the insulation between the circuit board and the device shell is damaged, the remaining current remaining current may be generated in the rectifier part. In the BOOST APFC circuit, the remaining current with a small ripple coefficient may be generated.Here, the BENDER’s diagram is used to explain the generation and harm of the remaining current of DC.
It can be seen that DC leakage may occur among the DC / DC part of the push -pull full bridge converter. The low -voltage power distribution system in my country generally uses TN forms of power. The metal shell of the device is connected with the working zero line. The DC leakage will pass the body and the PE line Feedback on the charging route, it affects the entire system current waveform.Through the simulation of the native circuit, the current waveform of the entire system will change, as shown in the figure below.
It can be seen that after a DC leakage occurs at the back end, it will also affect the front circuit. The pulsating DC waveforms after rectification occur, which causes spikes to interfere with the back -end circuit stepped.EssenceOn the other hand, due to the existence of the TN system, this failure will not form a large voltage in the body, which is less harmful to the human body. However, if the ground wire of the system is missing or the PE line is broken, then this part of the voltage will hurt the human body to the human bodyEssenceIn fact, there are problems with the connection of PE lines in many places, especially rural areas, especially in rural areas.The existing A type A RCD can only be interfered by DCCCB current when detecting the pulse DC leakage, and cannot detect DC leakage and disconnect. When the DC leakage is greater than 6mA, the magnetic core will cause the magnetic core to magnetize in advance., Increase the deduction value, so that the type A RCD cannot move normally, so it must be protected with type B RCD!
Inside the DC charging pile, the municipal electricity is converted into high -precision DC power to charge the battery through a non -vehicle charger.DC charging pile leakage protection is divided into the AC side and DC side. In theory, the communication side also needs to increase the B -type RCD for protection. The DC side needs to be installed with the DC -to -ground insulation monitoring device to detect the detection of DC positive poles and negative electrode insulation.
In the foreseeable future, as new energy vehicles enter millions of households, the charging pile will become an indispensable part of the lives of ordinary people. Therefore, the update of the remaining current protectors in the charging pile is necessary.The electric environment can allow everyone to rest assured to enjoy the convenience brought by new energy vehicles.
Magtron’s overall SOC chip overall solution based on IFLUXGATE technology has been digitized for type B leak protection protection. It provides a set of cost -effective B -type leakage solutions for RCCB from the traditional AC / A type / A -type type B technology.It provides better protection for the power safety of charging equipment.
【references】
[1] Liu Hongli, Ma Zhenglai, Nie Peng.Research and implementation of 4KW electric vehicle vehicle charger.Wuhan University of Technology, School of Automation.
[2] GB / T 18487.1-2015 Electric vehicle conduction charging system Part 1: General requirements.
[3] General requirements for GB / Z 6829-2008 remaining current action protector.
[4] GB 22794-2008 useless and similar useless and current -not -with -current B -shaped current removable current as a circuit breaker (B -type RCCB and type B RCBO).
[5] Cai Congchao, Wan Yingfei, Liu Yong, Ruan Shaoqing.Potential electric shock risk analysis and design of DC charging piles.Special Transformer Xinjiang New Energy Co., Ltd., Special Transformer Xi’an Electric Technology Co., Ltd..
[6] Liu Jinzheng, Zou Jianhua, Hu Hongyu.The application of the remaining current action protector in the electric vehicle charging system.Electric and energy efficiency management technology.