Design And Research Of Insulation State Real Time Detection System For High Voltage Battery Pack Of Electric Vehicle

The high-voltage battery pack of new energy electric vehicle has the characteristics of high voltage and high current,and the working environment is relatively bad,which will cause the insulation performance failure of positive and negative bus,which not only affects the vehicle electrical system,but also may lead to leakage,fire and other safety accidents.Therefore,the insulation performance real-time detection system of high-voltage battery pack is very important.This paper carried out the technical research in this aspect.The main research work and innovation of this paper are as follows.This paper studies the electric vehicle electrical system and its working environment,analyzes the external and internal factors of insulation failure,and summarizes the main forms of insulation failure.Then the advantages and limitations of the existing insulation detection technology are analyzed.It is concluded that the existing technical methods cannot fully adapt to the whole life cycle detection of high-voltage battery pack.According to the requirements of the national standard and the research results of the existing technology,a new insulation detection method combining the balanced bridge detection method,the low voltage injection method and the filtering algorithm is proposed innovatively.The feasibility of this method is confirmed by theoretical analysis and Simulation of circuit principle.Based on the analysis and establishment of the theoretical model,the software and hardware of the insulation detection system are designed.The hardware design adopts modular design,which is mainly divided into stm32f405 processor,first pulse unit,second pulse unit,AD sampling,can communication module,power supply module,etc.Hardware circuit design includes central controller system circuit design,power supply circuit design,bridge detection circuit design,signal injection circuit design,signal conditioning circuit design,signal sampling circuit design,communication circuit design,etc.The hardware circuit not only isolates the interference of high-voltage power supply and low-voltage power supply,but also designs the anti-interference of the hardware system.Software design is also modular design,which decomposes the whole system into several subprograms to improve the program reuse rate and reduce the memory occupation.In addition,digital filtering algorithm is added to improve the quality of A/D sampling signal,and the software system with excellent reliability and anti-interference is realized.Finally,the test platform is built to test and verify the detection accuracy and reliability of the method.The test results show that the established detection model can effectively measure the insulation performance,and the measurement accuracy is high.In many cases,the detection accuracy can be guaranteed within 5%.Only when the insulation resistance value is low,the error rate is large,but the actual value deviation can be maintained within5K?,the detection result is effective and reliable,which meets the expected goal.Therefore,this paper realizes a safe and reliable battery insulation detection system.