Energy Management System Control Strategy And Optimization For Pure Electric Vehicle Based On The Lithium-ion Power Battery

The pure electric vehicle which has the low noise, zero-release, and savingenergy is the developing trend of the automotive. Because of the technology of thebattery at present, the energy of the pure electric vehicle is limited. The drivingmileage cannot arrive to the level of the fuel vehicle. Because of the excellent energymanagement system control strategy, the bottleneck problem can be solved partly.There are two main control strategies: one is reducing the whole car energy utilizationrate method, only reserving the necessary high voltage load in driving anddistributing all the power to the driving system; the other one is improving the batteryutilization rate method. It can control the battery in a high-effect area by using thethermal management system. For the first method: although the electricity cost can beminimized in the driving process, the vehicle’s economic performance will beaffected because of lacking thermal management system, which will accelerate thebattery aging in the long-time high temperature circumstances. For the second method:the common method is threshold controlling method. Although its control strategy issteady, it cannot solve the problem of power distributing optimally because that thecontrolling rule is fixed and then the vehicle’s dynamic performance will be affected.For solving the above problems, this thesis gets the help from the followingprojects, they are: National Development and Reform Commission and The Ministryof Industry and Information Technology―The Electrical Equipment Researching andIndustrialization of the Pure Electric Vehicle‖; Department of Science andTechnology of Jilin Province―The Development of the Vehicle Control Unit ofQuick-Charge-Electric-Vehicle‖. This thesis makes the Lithium-Ion power battery asthe researching line and does the following researching to the pure electric vehicleenergy management system as follows:Firstly, the thesis makes the experiment analysis on the common power batteryequivalent circuit model, and finds out the main factor which affect the model’sprecision. And the thesis also designs the RC-H battery equivalent circuit model, andmakes the parameters identification and effective experiment validation.Secondly, the thesis designs the battery state of charge estimating method based on the RC-H equivalent circuit model and the parameters and Kalman filter theory bythe adjusting and optimizing of the ampere-hour integration method. And by theexperiments, the thesis validates the convergence and the stability of this method andestimates the precision.Thirdly, the thesis designs the battery state of power estimating method based onthe RC-H battery equivalent circuit model and takes the battery cell model to thebattery pack by the coherent parameters. And by the experiments, the thesis validatesthis method’s effectiveness in the battery cell and battery pack power estimation.Fourthly, the thesis introduces the energy management system power distributingcoefficient, points out the controlling aim of the energy management system, makesthe pure electric vehicle energy management system controlling strategy based on thefuzzy logics by analyzing the relationships of the power flows of the pure electronicvehicle energy management system. By the comparison experiment of the differencecontrol strategy in the same driving cycle, the thesis validates this method can makethe vehicle possess ideal economic performance and dynamic performance.Fifthly, the thesis points out an optimized scheme based on the fuzzy controllingstrategy. It takes the dynamic programming theory as guidance and adjusts the fuzzycontroller’s output parameters automatically based on the operating state of thesystem and minimizes the energy loss of the vehicle. The experiments prove that thisoptimization method can improve the battery’s using efficiency.At last, the author summarizes the contents, and makes a comparative analysisbetween the research results and other electric vehicles on the market, and makes theexpectation of the future on the researching.