Design And Implementation Of Power Battery Management System For Electric Vehicles

The battery management system is the key to the stable and reliable operation of electric vehicles.The BMS monitors and manages the battery voltage,temperature,state of charge,and vehicles/battery faults uniformly to complete the status display and alarm notification for users,which can effectively improve traffic safety and battery usage efficiency.For this reason,this paper studies the BMS embedded integrated machine and the host computer system.Considering the amount of system computation and the difficulty of parameter identification methods,the first-order Thevenin model is adopted to be equivalent to the battery circuit.By experiment on the the hybrid pulse power for the battery,the parameters of the equivalent model and the hysteresis curve of the open circuit voltage are determined.The accuracy of the open circuit voltage curve is verified by the results of the discharge simulation model of the battery.Taking the internal and external factors of the battery into account,the corresponding correction factor is introduced,c ombining with the open-circuit voltage method for determination of initial battery SOC,a modified ampere-hour integral method is designed to complete the SOC estimation.However,as the modified ampere-hour integration method is an open-loop method,where exists an irreparable initial error and cumulati ve error,Kalman filtering algorithm for SOC estimation is introduced.We establish the state space expression of the battery circuit based on the first-order Thevenin equivalent battery model,design the Kalman filter for SOC estimation,and guarantee the accuracy of the optimal value estimation by model simulation.According to the functional requirements of the system,the MCU basic management circuit,bus communication circuit,and battery monitoring module of the integrated machine are designed.The functional testing of the model is completed,and the embedded system of the battery management integrated machine is built to provide a hardware platform for the algorithm and software.We designed the embedded software based on the hardware platform of the integrated machine.The specific implementation process of the system and the battery/unit fault handling method is designed according to the corresponding execution actions of different working conditions of the system and state transition conditions.We introduce the BMS communication protocol,complete the graphic display and alarms of battery/machine status and fault information on the host computer monitoring software,and a unified monitoring and management platform of the host computer.The system complete CAN bus communication through the USB-CAN,the integrated machine starts the embedded program to complete the battery monitoring and data upload,the host computer receives the data and displays it to accomplish the integration test of the overall system.