Design Of SOC Estimation System For Electric Vehicle Power Battery

Based on the fact that today’s society has great demand for transportation,pure electric vehicles have become a major trend in the development of the automobile industry because of its clean and pollution-free advantages and not relying on fossil resources.As one of the core components of electric vehicles,the power battery has become the focus of research,including research on power battery SOC,battery SOH,battery BMS system,etc.The research object of this paper is the SOC of electric vehicle power lithium-ion battery,after which The corresponding hardware system and software system are designed to realize the simulation estimation display of the power battery SOC.This article specifically did the following work:In order to further improve the estimation accuracy of the SOC of the power battery,this paper establishes the state space equation and the output observation equation of the power battery based on the Thevenin first-order battery model and the modified ampere-time integration algorithm.A new method combining adaptive BP neural network and EKF algorithm is used to jointly estimate the SOC of the power battery.The parameters of the Thevenin model are estimated by the recursive least squares method with forgetting factor.The corresponding output parameters of the EKF algorithm and the battery operation time The temperature data is used as the training input value of the adaptive BP neural network,and the output value of the trained adaptive BP neural network is used as the compensation of the EKF algorithm to estimate the SOC value of the power battery.The research results show that the proposed adaptive BP-EKF algorithm can further improve the SOC estimation accuracy of the power battery compared with the EKF algorithm.After completing the theoretical simulation verification of the designed adaptive BP-EKF algorithm,based on the theory,a hardware system for estimating the SOC of the power battery is designed,including the current measurement circuit and voltage measurement circuit of the power battery.Temperature measurement circuit,minimum system circuit based on MC9S12XS128,CAN communication circuit and LCD liquid crystal circuit.And completed the drawing of the circuit schematic diagram and the PCB drawing of the wiring according to the actual package of the specific electronic components.Lay the foundation for the next practical application.After completing the above work,this paper uses MC9S12XS128 as the core control chip to use CAN bus as communication mode,and completes the simulation display verification of the algorithm on the single-chip microcomputer.The designed software system includes: ATD conversion code,ECT code,CAN communication code,PIT code and LCD display code based software system.The working mode of the whole software system is: after the ATD conversion completes the information data collected on the power battery,the information is sent to the receiving end of the MCU through the CAN bus,and the adaptive BP is completed in the PIT interrupt program of the receiving end.-Calculation of the EKF algorithm and displaying the calculated SOC data on the LCD liquid crystal.The verification results on the simulated system show that the designed adaptive BP-EKF algorithm is implemented.After recording the displayed data and comparing with the experimental data,the error of the power battery SOC estimated by the algorithm is obtained.Within 3%,it achieved the intended purpose.