Research On Monitoring System Of High Voltage Safety For Pure Electric Vehicles

In recent years, the energy crisis and environmental pollution has become increasingly serious, we develop energy-efficient and zero-emission pure electric vehicles have become an inevitable trend of the development of automobile industry. The operating voltage of high voltage system should above300V, operating current should up to tens or even hundreds amps, when high-voltage safety fault occurs, the high-voltage and high-current will endanger the safety of passengers, will also affect the low-voltage electrical work. Therefore, study of high-voltage safety monitoring for pure electric vehicles has a very important significance.In this paper, the study of high-voltage safety monitoring system for pure electric vehicle was based on analysis of the characteristics of the electric vehicle high-voltage circuit, the theoretical basis was the high-voltage circuit model, and the hardware master unit used the STM32chip. System through real-time monitoring the important electrical parameters of the pure electric vehicles high-pressure circuit to realize the electrical safety and fault diagnosis&alarm during vehicles starting and stopping. The main work and results of this paper are as follows:1. Arranged in the form of high-voltage system for pure electric vehicles were designed. All kinds of potential failure of high-voltage system for pure electric vehicles were analyzed. The high-voltage system circuit models of pure electric vehicles were simplified. Insulation resistance model, the equivalent capacitance model and the remaining power model were established.2. The various functions of the system were presented based on the hardware design requirements of high-voltage safety monitoring system for pure electric vehicles. The hardware circuits of the functional modules of the system have been developed. The realization of the principle of functional modules and hardware anti-interference method were described. The hardware PCB test board was welded.3. The fault was classified based on the severity of the fault of the high voltage system. The high-voltage system control strategy was divided into high-voltage system opening control strategy, high-voltage system management strategies and high-voltage system shutdown control strategies. Three flow charts of control strategies were drawn.4. System test platform was structured. Experimental program of insulation resistance, response of closure for contactor and response of break for contactor was designed. Insulation resistance model validation test, high-voltage contactor closure response test and high-voltage contactors disconnect response test were completed.The final results showed that:The measurement of the insulation resistance value there is only a relative error of0.3%relative to the theoretical value, and to prove the correctness of the calculation model of the insulation resistance; the DC contactor disconnected response time of approximately14ms, than the national standards required by the20ms security value increased by30%. The two indicators meet the design requirements.