Gao Xinjie: Electromagnetic Compatibility Design Understanding of Electric Vehicles
With the advent of the post-subsidy era for new energy vehicles, technological development and operational innovation have become the top priority in promoting the new energy automotive industry in the current situation. On December 21st, 2016, the 3rd China New Energy Automobile Engineering Technology Summit and the 2nd Conference on the Matching of Operators and OEMs in the “Subsidy Period, Technology Innovation and Development Approach†was held in Shenzhen Kailuo Grand Hotel. Opening. The conference was organized by the Organizing Committee of the Electric Vehicle Resources Network and the China New Energy Automotive Engineering Summit. Hundreds of elites from the leading domestic OEMs, core parts and components companies, operators, and industry institutions and institutions gathered in various fields. Shenzhen will jointly participate in this industry event dedicated to new energy automakers.
The conference lasted for three days. The meeting on the morning of the 22nd invited industry experts, scholars, and leading domestic hosts to focus on “Understanding the criteria of complete vehicles and key components, reliability, safety, efficiency, EMC evaluation, and cost-reduction innovationsâ€. The elites in various fields such as factories and core parts and components companies are exploring. Gao Xinjie, Chief of the EMC Development Section of the Beijing New Energy Automotive Co., Ltd., gave a speech titled "Electric Vehicle Electromagnetic Compatibility Design Understanding". The following are the main contents of his speech:
I. Analysis of Electromagnetic Compatibility Test Cases for Electric Vehicles
1. Information obtained from vehicle test case 1: caused by the motor system and DC/DC converter.
2. Information obtained from vehicle test case 2: caused only by the low voltage circuit of the motor controller.
3. Information obtained in vehicle test case 3: caused only by a low-voltage component.
4. Complete vehicle test case 4
The case is a 40,20 megawatt speed, a common problem. Who caused the problem? Tests have found that it is a common problem whether the motor drive system is enabled and whether the DC/DC converter is operating.
5. Vehicle test case 5: Follow-up standards will be implemented and should be noticed.
Companies that are responsible for doing chargers for this executive standard need to pay attention to this one. Information obtained: EMC characteristics and layout of the OBC, layout of the AC input harness and low voltage control harness, layout and length.
6. Summary: There are a lot of companies that do parts, including DC/DC, high-voltage components, complete vehicle EMC, wiring harness. One design of the whole vehicle EMC is caused by the power battery circuit. The entire vehicle EMC design involves high-pressure components and low-voltage components.
Second, the analysis of the case of electromagnetic compatibility of electric vehicles
1. Optimization Case 1
This is a magnetic field test. Carefully observe that the left and front magnetic field tests have a resonance point (universal problem) at 1.39 MHz, the left side is used as the optimized position of the magnetic field and the electric field, and the optimization of the resonance point is emphatically studied.
2. Optimization Case 1 (continued)
After taking six measures, the comparison of the X- and Y-direction magnetic field tests on the left side (vehicle speed 16 km/h) found that after the six measures were implemented, there was almost no significant change in the left X direction and the Y direction was very low.
3. Optimization Case 1 (Continued): Added "Y" Capacitance Scheme to High Voltage DC Terminal
After adding the “Y†capacitance, the magnetic field in the X and Y directions on the left side was compared with the bottom test (vehicle speed 16 km/h). It was found that the magnetic resonance point was at or near the background, thus verifying the effectiveness of the measures.
4. Optimization Case 2: The shield is disconnected and there is no wiring
Before and after the lap joint optimization, electric field test comparison (vehicle speed 16km/h) found that the electric field tests at the front, rear, left, and right sides were excessively severe. At the same time, a simple optimization was performed. The shielding layer was connected and the overlapping measures were added. The effect was obvious. Must be lapped? not necessarily.
5. Optimization Case 3: CAN shielded?
This case is that there are two OBCs in an integrator, and the OBC also shields the layer. If adding the shield split signal is OK, a simple optimization is made to disconnect the OBC at the shield, but it cannot be left unconnected. From the test results, it can be seen that the CAN shield ground connection, CAN waveform does not meet the technical requirements, measure 4 after the CAN waveform is very good, no error frame.
6. Optimization Case 4: Comparison of a Sensor Signal before and after Optimization
When a BR component is disturbed by a simple optimization, this optimization is related to the power battery. It can be seen that the waveform comparison of the optimized front sensor signal is very obvious.
7. Optimization Case 5: Contrast before and after reversing image optimization
After optimizing the reversing image test, look for a clip to short the camera video and the negative polarity of the monitor to compare what happened.
8. Summarizing: Accumulating and developing, researching the "Electromagnetic Compatibility and Quality Control Specification and Method for Electromobility", "Standard Specification for Electromagnetic Compatibility Test of Electric Vehicles", "Power Supply and Signal Integrity Analysis and Engineering Practice", and "Switching Power Supply for Electric Vehicles" Design Principles and Practical Techniques, "High Voltage and Low Voltage Harnesses for Electric Vehicles and Structural Design."
Third, the design difficulties of electromagnetic compatibility of electric vehicles
1. The urgency of the research on electromagnetic compatibility of electric vehicles: Following water pollution, air pollution and noise pollution, electromagnetic radiation has become the fourth largest source of environmental pollution in today’s society, and it has the characteristics of invisible, invisible, and inaudible. There are mysterious colors.
2. The depth of research on electromagnetic compatibility of electric vehicles
For the high and low voltage parts of the vehicle, the actual waveform is inaccurate and is always in a trimmed state. Tesla, BMW, and BYD have all done this test. Only Tesla's car has no problem. For BMW and BYD's cars, spot two models and go to a very high pressure environment, but the test results are not very impressive.
First of all, the standard laws and regulations are the car companies must pay attention to, followed by system compatibility, human protection, power battery or BMS supplier, are all attention. So why is BMS always inaccurate? What is the depth of research on domestic new energy auto companies?
3. Difficulties 1: Contradiction between layout and space
Electromagnetic compatibility design of electric vehicles is actually only the layout of electric vehicles, the space of electric vehicles is small, the electrical structure is complex, and the layout is compact. It is found that the EMC characteristic is only one of the important characteristics of the vehicle electrical system, in such a narrow space. Designing in the middle rather than the flat is definitely difficult. Once the layout and state of electrical components are frozen, the entire vehicle EMC becomes an inherent characteristic.
4. Difficulties 2: DC/DC output needs attention
Analysis: As we all know, the body as part of the negative ground, there are currents on the various surfaces of the body, it is known from the car body and the circuit design on the plane there are differences, DC / DC converter function also shows that the DC / DC converter output EMC design is very important .
5. Difficulties 3: High-pressure component system integration technology capabilities need to be improved
(1) DC/DC Converter & Car Charger
(2) DC/DC Converter & Motor Controller
(3) DC/DC Converter & Motor Controller & Car Charger
There is almost no difference in the circuit topology, but there is a big difference in the design of the housing structure, materials, and circuit layout, and the resulting EMC performance difference is very large! At the same time, most of the square-shaped housing design in China has laid a slog for the building of a complete vehicle electrical architecture.
6. Difficulty 4: V2G, wireless charging and other emerging technologies applications - standard formulation and implementation
V2G will be included in EMC's charging standards. V2G's case is less done domestically and V2G conduction is very difficult. In the past, many OEMs had problems with all of EMC's responsibilities plus DC/DC. Then there were problems with controllers. That was not good for the OEM's EMC setup. The idea was to rely entirely on suppliers of parts and components.
7. Summary: To break the past reliance on the promotion of suppliers to pursue the adoption of standards; to enhance the depth of research, establish a knowledge system of research and development with independent intellectual property rights; to strengthen the technical exchanges within the industry and cooperation of testing agencies.
IV. Electromagnetic Compatibility Design Ideas for Electric Vehicles
1. EMC design principles: EMC design ideas into components and vehicle design
Consider: time to market, high-voltage safety, lightweight, IP protection, cost, NVH, ease of maintenance, reliability, electromagnetic compatibility, aesthetics...
EMC is just one of the important attributes of the vehicle's electrical system. It is a "soft" feature based on the vehicle's entity. Considering factors such as functional integrity, reliability, technical cost, light weight, and time to market for the entire vehicle electrical components, the layout and technology control status are determined, and materials, structures, and processes are selected during each phase of vehicle development. Design ideas and specific measures such as grounding, shielding, and filtering are implemented in products or systems in the lowest cost and most effective way.
2. Achievable feasible methods for vehicle EMC design: based on a reasonable development process
Planning phase - system architecture layout phase - design phase - system testing and state freeze phase - assessment, review, and optimization phase
3. Quantitative design premise of complete vehicle EMC: Orderly layout of electrical architecture
Why the layout is the most critical, if ABCDEF 6 districts, all of the district's EMC design, including the wiring layout, like a mobile phone, why not do a good shield, it will have a lot of filter capacitors in all parts and the like. The layout is a complete design, and it should actually be controlled in Zone A. It should not be that the harness of this vehicle is a crossover.
4. Motor Controller EMC Design Optimization Key: Drive Isolated Power EMC Design
Manufacturers of motor controllers should pay attention to the fact that the entire vehicle is generally exceeding the standard at 20 to 30 megabits, but through improvement, it is mainly driven by the isolated power supply. The interference actually mirrors the entire vehicle frame.
5. Summary
EMC design is very simple. The key to EMC is design philosophy. EMC's development process This domestic BYD process document is better controlled. In fact, where is EMC's biggest domestic and foreign gap? Foreign joint venture brand control and evaluation links are particularly complex and detailed. Engaged in the design of new energy vehicles, do you think that we can build so many complex process software for EMC? What is shielding? If everyone is in a meeting and bother to the opposite, this screening is not good. EMC should establish its own development process. Of course, EMC has more design methods.
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