Research On SOC Estimation Algorithm Of Pure Electric Vehicle Lithium Battery

As domestic environmental protection policies have become more stringent and affected by national crude oil reserves,in the past ten years,with the strong support of national policies,electric vehicles have experienced rapid development.Batteries as energy storage devices for electric vehicles,and the accurate SOC(State of Charge)value is very important to prolong the service life of battery and avoid overcharge and over discharge.Modeling,simulation and SOC estimation of lithium battery for electric vehicle are done in this paper:Firstly,The development status of new energy vehicles and the research status of battery management system are introduced in this paper,and then leads to the estimation algorithm of lithium battery SOC.After comparing and analyzing several common SOC algorithms,it is determined that this paper uses the extended Kalman filter algorithm to perform SOC on lithium battery estimate.Secondly,in order to make the battery model accurately simulate the dynamic characteristics of the battery,and at the same time,the battery model is not too complicated.After comprehensively weighing the accuracy and complexity,the DP equivalent circuit model is selected as the battery model in this paper.The accuracy of the DP equivalent circuit model is verified under current discharge conditions.Because of the phenomenon of "data saturation" existing in the process of online identification due to the accumulation of old data,the forgetting factor recursive least square method for online identification was choosed in this paper,transforms the DP equivalent circuit model into recognizable mathematical form,and deduces the expressions of various parameters in the transformation process in detail.Finally,the extended Kalman filter algorithm model was established in the Matlab/simulink environment,and the SOC value obtained by the ampere-hour integration method in the simulink environment was used as the reference value.The extended Kalman filter was also verified under the HPPC discharge condition and the constant current discharge condition.In order to verify the accuracy of the extended Kalman filter algorithm applied to the actual vehicle operating conditions,a AMEsim/simulink co-simulation model was established,and the initial value of the battery SOC of the AMEsim model was different from that of the EKF algorithm model.It is verified that the extended Kalman filter algorithm can accurately estimate the battery SOC under NEDC actual cycle conditions.