SOC Estimation Of Lithium Battery And The Research Of Equalization Control Strategy

While promoting social economy and meeting people’s living needs,the traditional automobile industry has also greatly depleted the earth’s resources and brought serious environmental pollution.Lithium battery by virtue of its high output voltage、long cycle life、low self-discharge rate、high energy density、no pollution、light weight and other advantages,quickly occupy the vast market.Electric vehicles with the advantages of low power consumption,low noise and zero pollution are recognized as the development trend of future automobiles.Battery Management System(BMS)is related to the energy stability and safety of automobiles,and is a particularly important technology related to electric vehicles.Excellent BMS can protect the battery from overcurrent and overvoltage,effectively increase the service life and mileage of the battery,provide users with real-time and reliable battery status information,and help users control the battery status.State of charge(SOC)estimation and balanced control strategy are two basic and critical technologies in electric vehicle BMS.Based on the analysis of the research status of BMS at home and abroad,this paper introduces the basic functions,hardware framework and software process of BMS.Secondly,the inconsistency of lithium battery,the harm to the battery pack and the solution are analyzed.Then by comparing and analyzing the advantages and disadvantages of the commonly used battery equivalent model,this paper simplified the original Thevenin circuit equivalent model and established a more simple and easy to calculate Thevenin equivalent circuit model.Finally,Genetic Algorithms(GA),Particle Swarm Optimization(PSO)and Artificial Neural Network(ANN)were used to calculate the SOC of lithium battery based on ga-bp Neural Network and hpso-bp Neural Network.The two joint algorithms are proved to be accurate and convergent.At last,based on the analysis of common energy consumption and non-energy consumption equalization circuit,this paper designs a cascade equalization control circuit and formulates corresponding equalization control strategy for this circuit.When the maximum SOC deviation is greater than 3%,the balance control is started for the battery pack.When the maximum SOC deviation of the battery pack is controlled within 1%,the balance circuit is in standby state to complete the balance.The simulation results show that the balanced control circuit can realize thefunction of charge and discharge equalization and fault redundancy.