Research on Electrical Testing System of New Energy Vehicle Based on Computer

According to the design structure and working characteristics of the whole vehicle electrical system of new energy vehicle, combined with the deep application of computer in PLC programming and sensor, this paper studies the detection target, detection principle, detection method and some instruments of electrical insulation performance and electrical working performance, in order to provide some reference for the development and progress of new energy vehicle electrical system.


Introduction
Electrical systems have always been one of the big systems in cars, almost everywhere. Since its own traditional car, it needs to use a lot of electricity to assist the device, there are lights, wipers, lighter and so on need to use electricity, but in the traditional car, these parts of the electricity are low piezoelectric, generally do not have the danger of electric shock, even if there is a fault, generally will not cause serious consequences. The new energy vehicle develops rapidly and receives the attention in the world [1] . The application of electric energy in the new energy vehicle is more extensive than before, the electrical system is more complex and the function is more perfect. Whether it is a pure electric vehicle or a hybrid new energy vehicle, in the new energy vehicle with electric system as power supply, there are high voltage circuits in the vehicle, which far exceeds the voltage range of safe voltage. The development of new energy vehicles to some extent alleviates the pressure on the ecological environment and plays a positive role in the social and economic prosperity and the progress of power technology. The electrical system is the key to the concept of new energy. But the complete automobile electrical system is in the initial stage of exploration at home and abroad, without mature technology and definite direction, the future long road needs to be opened up a little bit. Therefore, including electrical insulation system and electrical performance system of new energy vehicle electrical test system research is significance.

Technical characteristics of electric system of new energy vehicle
We usually refer to hybrid vehicles and pure electric vehicles. Due to the limitation of technical conditions, the short board of new energy vehicles in energy utilization and energy storage is still very obvious. Therefore, new energy vehicles are mostly used in specific fields. In order to enhance the 2 ability of new energy vehicles to store electricity, super capacitors have been widely used in new energy vehicles, which have the characteristics of environmental protection. The research shows that it is very important to improve the voltage of energy vehicles in order to make a breakthrough in power utilization and efficiency, and to show obvious advantages in economy [2] . However, the increase of automobile power supply voltage must put forward more stringent requirements for the insulation and operation performance of the whole vehicle electrical system than before, which greatly increases the difficulty of the production of new energy vehicles. So that the number of manufacturers able to produce qualified new energy vehicles dropped a lot. In order to achieve better energy utilization, electric vehicles use high voltage drive motor. In addition, the control system design of pure electric vehicle must be timely and accurate in order to improve the man-machine operation and safety of the vehicle. The electric storage of the energy storage device can maintain the distance of the vehicle driving is of great significance to the normal driving of the vehicle. The new energy automobile electrical system and the traditional automobile electrical system are completely out of date, so there is a lot of research work to be done in testing. Along with the development of computer technology, the control of PLC current or the crowning of sensor voltage will be the important technical basis in the development of automobile electrical system [3] .

Electrical insulation requirements analysis
For the sake of safety, the power supply of new energy vehicles often adopts parallel double power supply or double battery packs. One way for lithium battery power supply, the other way can be oil and gas power supply or battery power supply. In most designs, the output characteristics of the combustion battery can be converted between constant voltage and constant power by boost converter. In order to ensure the efficiency of automobile battery, the current of automobile output power supply changes according to the running condition of automobile, but the voltage needs to be guaranteed at a higher level in accordance with the regulations, which can save energy [4] . Improve the power supply efficiency of lithium battery power supply. Among them, constant power and constant current are mainly responsible for limiting the maximum power and current limit of fuel cell output in new energy vehicles. It can use the distribution of lithium batteries in high voltage systems. In this way, new energy vehicles achieve the design goal of providing power under normal conditions by high voltage lithium batteries.

Insulation test principles for new energy automotive electrical systems
New energy vehicles are tested before they are put into use, including insulation testing. The insulation detection of new energy vehicles is mainly based on the performance detection of the impedance network established between the positive and negative electrodes of the on-board high voltage power supply. Because of the wide use of new technology, new technology and new materials, the electrical system has changed greatly in structure and performance. Many of the original automobile electrical system testing methods and tools cannot be used, but need to adjust the electrical test system in real time to adapt to the new changes according to the actual test and experience, so as to ensure the safety of the automobile electrical system.

Test method for electrical insulation in new energy vehicle
The electrical system of new energy vehicle is mostly high voltage DC, and adopts the form of closed loop. For this kind of electrical system, the auxiliary power supply method or the current sensing method are generally used to test the electrical system, and this kind of test is also found in the detection and treatment of the automobile electrical system fault in the garage after the factory is used [5] . The main function of electrical insulation test is to detect whether the current of new energy vehicle battery is leaking. If the leakage current is too large, the alarm will be automatically triggered, and the internal power will be cut off. Reduce the damage of new energy vehicles and ensure the

Analysis of performance test method for vehicle electrical system
At present, there are few companies in China that can independently develop the electrical performance test system of new energy vehicle, and the accuracy of the collected data is low and the system performance is poor. All kinds of waveforms are obtained by computer processing, and the report form is generated. The same rate is low, only simple data can be processed, and the requirements of electrical performance test are not satisfactory. Figure 1 shows the data acquisition mode of computer communication card and communication interface.

Sensor principle
There are many kinds of vehicle-borne electrical signals in new energy vehicles. The function of sensors is to transform the physical quantities in nature into electrical signals or other required forms of information output according to certain laws. As a signal converter, the choice of sensor will directly affect the design of the overall structure of the electrical test system of the new energy vehicle. Taking the Hall current sensor as an example, it is divided into closed loop Hall current sensor and open loop Hall current sensor. The difference between the two is that the open loop Hall current sensor produces another compensating magnetic field equal to the current magnetic field of the original conductor and opposite direction.

Sensor selection
Now, the development of computer technology and semiconductor materials is very high, sensor technology is mature, various forms, and a wide range of options. There are FDIB-C16 series of current sensors using fluxgate principle, DC leakage current sensor, 80 i-110s AC / DC current clamp with strong compatibility, clamp AC/DC sensor with wide applicability CT9693, K thermocouple made by thermoelectric principle, etc.

Electrical test system requirements
(1) Measurement signals. The whole vehicle electrical test system needs to measure the functional signals including auxiliary electrical. (2) System power supply requirements. The electrical test system can use the battery of the automobile itself to supply power, and it can also be connected to the external power supply for power supply. In the process of testing, the protection of short circuit and overload of the system should be strengthened [6] . Figure 2 is a schematic diagram of single and double power supply for the sensor of the test system. (3) Environmental adaptation needs. In addition to the system's working temperature, humidity, seismic and moisture-proof and other external environment, but also check EMC, and continuous working ability, joint contact stability and other internal conditions [7] .

Conclusion
The new energy automobile is produced under the situation of the development of science and technology and the overburdened ecological environment, and its appearance is not only a technical but also a breakthrough in understanding, which is of great significance. New energy vehicles have new inventions in technology and materials, and are used in high voltage electrical systems. In the design, we should pay attention to the experimental test effect and related knowledge principles at the same time, in order to improve the performance of all aspects of the electrical system of the automobile.