Study On SOC Estimation Method Based On Battery In Electric Vehicles

The development of automobile industry brings comfort and convenience to people’s life.But thecars consuming oil accelerates the energy crisis,and brings environmental pollution.Therefore,Thedevelopment trend of the future is that the clear low carbon electric vehicle(EV)EV will replace carsconsuming oil.However,EV use a lot of batteries as power source,and the battery’s energy density is low.Sothe EV may take place power failure in use.It may take much trouble to production and life.Estimation ofSOC can resolve this problem.The estimation of SOC is one of the hard core in the battery managementsystem.It can represents the SOC at every time,reminding the driver of charging at time,advoiding nocharge in halfway.We can know EV mileage at any time.According to the SOC,So estimating the SOCaccurately SOC is very important.Firstly,the thesis introduced the kinds of batteries of EV and its performance parameter,theprincile of operation.Then the advantages and disadvantages of SOC were described in detail.Because theestimation of SOC is the combination of the arithmetic and batteries’ model,giving main battery model’sschematic diagram.And the internal factors impacting the estimation of SOC was analyzed.The Taylorformula combining the battery model and arithmetic as a bridge was stated.Secondly,A newarithmetic---.Composite kalman filter is proposed to improve the estimation method of SOC.The newarithmetic combined the advantages of the accurate estimation of SOC when EKF worked at the currentdramatic changing and Ampere----hour integral method worked at the stable current.Then the newarithmetic was used in the battery model of Thevenin equivalent circuit model.The Taylor formulaterealized the linear coming into nolinear,finishing the research of SOC in this thesis. Finally,based on EVbatteries simulating situation discharge test,and the MATLAB was used to simulate experimental data.Thesimulating results of arithmetic this paper were compared with EKF and the true value.Simulation imagesshowed Composite kalman filter was better than EKF,approching the ture value,and inhibited definitely thenoise.The determination of the joint--point of Ampere----hour integral method and EKF is the one ofthe creative point of this paper. The suitable joint--point is found by selecting the current model and the batteries, analysising and comparing experimental data. Duing to the samll calculated amount whilereaching the require precision, the battery model and the arithmetic are combined by using a first orderTaylor formula as another creative point of this paper.