Research And Application Of Insulation Resistance Calculation Model Based On Low Voltage Pulse Injection Method

With the development of society and science and technology,energy supply and envirorunental protection have been severely challenged.Under the active support of the country for "green travel and low carbon development",People pay more and more attention to environmental protection and propose new ways of life.Requirements.Electric vehicles use electric energy as a direct energy to drive electric motors.The source of electric energy is multi-channel and regenerable.Therefore,electric vehicles have incomparable advantages compared with traditional fuel vehicles using non-renewable fossil fuels as power sources.Therefore,electric vehicles are favored by the public and develop extremely rapidly,making them the most potential means of transportation in the future automotive market.New energy electric vehicles use the power battery high-voltage DC system to power the entire car.However,the internal structure of the high-voltage DC system is complex,and the bus voltage is generally above 300 volts.The changes in the vibration,shock,temperature and humidity of the environment during the use of the vehicle cause a great change in the safety insulation performance,directly threatening the safety of passengers and giving the society.The stability of electric vehicle power battery operation,especially the real-time safety monitoring of insulation performance has become one of the key research points of electric vehicle technology.The insulation fault of electric vehicles mainly refers to the situation that the power battery leaks due to the aging of the power battery and the leakage of the two ends of the battery bus.Therefore,the monitoring object of the insulation monitoring system is the equivalent insulation resistance of the power battery.In this paper,the characteristics of several traditional power battery insulation resistance detection methods are compared and analyzed.The advantages and disadvantages of each method are pointed out.A power battery insulation detection scheme based on low voltage pulse injection method is proposed.In the hardware design of the scheme,the 8-bit Freescale control chip of model MC9S08DZ60 is used as the main control unit,and the circuit with modular design is divided into detailed functions.The circuit diagram of the main component modules is drawn and the hardware is drawn.The anti-jamming design of the circuit raises some considerations.In the software design,the module is divided according to the logic flunction of the insulation monitoring system detection algorithm.Based on this,the program flow chart of each module function operation is made,and the function model is built in the development environment of MATLAB/SIMULINK,and the model is analyzed.Logical operation and signal transmission,using the model to be converted into a code program that can be downloaded and debugged,and finally through the laboratory bench simulation power battery use environment for experimental debugging.The test data shows that the measurement error of the insulation resistance of the power battery shows a trend of decreasing first and then increasing with the increase of the resistance value.Among them,when the error is higher than 200 KΩ。there is a small error accuracy fluctuation of 2%.In the case of eliminating extreme insulation faults,the overall insulation detection accuracy is kept within 5%,which proves the feasibility of this research scheme.