SOC Estimation And Research Of Vehicle Power Battery Pack

In recent years,with the increasing use of lithium-ion batteries in electric vehicles,the healthy life of batteries,the range of electric vehicles and the energy feedback of batteries have become key factors affecting battery systems.A Battery Management System(BMS)which has accurate estimation of state of charge(SOC)can effectively solve the above problems,and it is also an important part of electric vehicles.SOC estimation is the core part of BMS,and its accuracy affects battery health life,balancing strategy,thermal management strategy and other technical parameters.Battery operating temperature,charge/discharge rate,noise,aging,and inconsistency of the battery pack are the key factors that affect the accuracy of battery pack SOC estimation.This research takes 18650 cylindrical lithium-ion batteries as the research object,and designs a battery pack estimation method with parameter-free recursive least squares(PF-RLS)with the forgetting factor and adaptive smooth display estimator(ASDE).The main research contents are as follows:(1)The working principle and related battery characteristics of lithium-ion batteries are studied,mainly analyzing the influence of temperature,charge and discharge ratio on important parameters such as battery characteristic capacity,open circuit voltage(OCV)and especially battery pack inconsistency.Then introduce the related battery model.(2)The first-order RC model and battery pack model of the battery model are established.Based on the model,the parameter identification methods are introduced and compared.Finally,a parameter identification method-PF-RLS is proposed,and the open circuit voltage is calculated in real time.The identification accuracy of related parameters is compared and analyzed.(3)According to the battery characteristics,the established battery model and parameter identification method,an ASDE algorithm is proposed to obtain accurate battery pack SOC estimation results.At the same time,the SOC estimation of the series battery pack is analyzed based on different complex operating conditions,and the ASDE algorithm is compared with the Ampere-hour integration method and extended Kalman filter algorithm in robustness and accuracy.(4)The test bench and the working conditions of parameter identification verification and ASDE algorithm verification are introduced.At the same time,the ASDE algorithm is implemented in C language.The software and hardware of BMS controller are used to implement the ASDE battery pack SOC algorithm in vehicle verification.The experimental results show that it is very robust and accurate under real vehicle conditions,and there is no jump during driving or standing.