Study On SOC Estimation Algorithm Of Lithium-ion Battery Based On Remote Monitoring System For Pure Electric Vehicle

With the development of electric vehicles, power battery has become the hot topic,which is acted as a key factor influencing the vehicle’s performance. Lithium-ion battery hasbeen widely applied in electric vehicle, for its large specific energy and specific power. Sofar, the prediction of battery capacity has been an important factor to battery managementsystem. The residual capacity of battery is denoted by SOC(State of Charge). In order tomeet the request of state laws to new energy vehicles, make sure the safe and reliableoperation of pure electric vehicle, it is necessary to estimate and monitor the state of chargefor power battery.This research subject is from the project named the development of remote monitoringsystem and the research of battery failure diagnosis technology for pure electric bus, whichbelongs to the high-tech electric car company in Jilin Province. Jilin University assumes theresearch job on the state of charge estimation and remote monitor for battery. This papertakes the CCQ6750EV1pure electric bus as the research object, which is made by High-techCompany, and carries out the research of SOC estimation, aiming at180Ah Lithium ironphosphate battery. The existing BMS of this bus has the functions of data acquisition,management and protection for battery etc, adopts Ah integral method to estimate SOC.Through abundant real vehicle operations, it finds that there is a big error in theestimation accuracy for the existing estimation method. So this research group does theresearch on the SOC estimation of battery, tries to adopt a more appropriate method toincrease the estimation accuracy, and realize the SOC remote monitoring display through thesystem of remote monitoring system, to verify the estimation accuracy.In this paper, the main research contents include the following several parts:1. Chosen180Ah lithium ion battery as the research object. Based on the operatingprinciple of Lithium battery, did the related characteristic test, analyzed the capacity characteristic and the influential factors to battery capacity, got the correct SOC expressionby amending the Ah integral method.2. Chosen PNGV model as the estimation model, after analyzing all kinds of batterymodel, founded the battery simulation model in Simulink, got the experimental data byHPPC pulse experiment, taking the temperature into consideration; identified the modelparameters, obtained the parameters with the changes of temperature and SOC, simulatedand verified the model accuracy.3. Combined the adaptive algorithm into the EKF, founded the SOC state-spaceequation based on AEKF algorithm, compiled the estimation procedure in MATLAB, andadopted two operating conditions to verify the estimation accuracy.4. Founded the remote monitoring system, realized the monitor and display of vehicleinformation; verified SOC estimation accuracy in real vehicle operations.