Research On The State Of Charge Estimation And Equalization Control Strategy Of Battery Management System For Electric Vehicle

As one of the most promising vehicles in the development of new energy vehicles,Electric vehicle are mainly drived by battery.Compared with the traditional vehicle,Electric vehicle has the advantages of better environmental protection,lower energy consumption and renewable power sources.The most important factor that affects the development of electric vehicles is the battery management system(BMS).In this paper,we mainly study the dynamic state of charge(SOC)estimation and the inconsistency of power lithium battery in the battery management system.The main research contents as follows:Firstly,this paper studies the basic characteristics of the power lithium battery,mainly the electrical characteristics and performance parameters.Based on the analysis of the basic characteristics of power lithium battery,the advantages and disadvantages of the equivalent model of power lithium battery at home and abroad are analyzed and compared in detail.The applicability of the Kalman filtering algorithm and the extended Kalman filter algorithm are discussed in detail,such as the Kalman filter algorithm for linear signal estimation with very good effect,and the extended Kalman filter algorithm is improved by Kalman filtering algorithm which can accurately estimate application for nonlinear signal can cause inconsistency.This paper analyzes the causes of the inconsistency of the power lithium battery and the negative consequences,and demonstrates the necessity of the equalization control.The advantages and disadvantages of several kinds of equilibrium control schemes are analyzed in detail.Then,based on the analysis of the advantages and disadvantages of different equivalent models of power lithium battery,this paper presents an improved equivalent model of PNGV power lithium battery,and the model parameters are identified by the zero input and zero state response analysis combined with least squares identification.In order to verify the practicability of Kalman filter and extended Kalman filter.Matlab/Simulink and Advisor are used to simulate the parameters of the equivalent model;the Kalman filter and the extended Kalman filter algorithm are applied to the Advisor simulation software to verify the algorithm.The simulation results show that the improved PNGV model combined with the extended Kalman filter algorithm has high accuracy of SOC estimation,the error is very small,and the nonlinear SOC estimation effect is obvious.Finally,aimed at the necessity of the power lithium battery pack equilibrium control combined with the analysis of the current balance control strategy,This paper proposes a new control strategy based on Buck-Boost double energy transfer,and the equilibrium process of the equilibrium strategy is analyzed in detail.In order to achieve a balanced effect,the software and hardware design of the circuit module for each module of the balanced control system.The hardware mainly includes power supply circuit,voltage measurement circuit,current measurement circuit,temperature measurement circuit,equalization circuit and so on.The software part mainly uses the LabVIEW to carry on the development of the upper computer and the communication between the upper computer and the lower computer by CAN bus.In this paper,the equilibrium experiment is carried out.The results show the effectiveness and accuracy of the proposed control strategy.