Research On Lithium Battery Charging Strategy Based On Particle Swarm Optimization

At present,the main development direction of China's new energy vehicles is pure electric vehicles,and the battery is one of the core components that limit the development of pure electric vehicles.Because of the electric energy density,cycle life and self-discharge rate of pure electric vehicles,higher requirements ensure a fast and safe charging and discharging of pure electric vehicles.Firstly,based on the dynamic nonlinear system of lithium battery,a new lithium battery equivalent model is proposed,and the state of charge(SOC)of the battery is estimated.The experimental results show that the extended Kalman filter(EKF)algorithm The estimation error of the new lithium battery equivalent model can be controlled within 2%,which verifies the effectiveness of the new lithium battery equivalent model.Secondly,based on the proposed new lithium battery equivalent model,the lithium battery charging and temperature rise model was built by Matlab/Siumlink software.The lithium battery charging process was divided into 100 stages according to the interval of 1% SOC.The programmed particle swarm optimization algorithm optimizes the 100-stage constant current charging strategy of lithium batteries.By establishing a fuzzy controller for lithium battery charging time and battery temperature rise,and using its output as the fitness value in the particle swarm algorithm,the particle swarm algorithm is used to judge the charging time of lithium battery and the optimization of battery temperature rise.In the particle swarm optimization process,the established lithium battery charging temperature rise model is continuously called,and finally the 100-phase constant current charging optimal curve of the lithium battery is obtained.According to the optimized charging curve,the simulation experiment is compared with the 1C constant current charging simulation results.The results show that the 100-stage optimal charging strategy can shorten the charging time by 674 seconds.At the same time,the temperature rise of the lithium battery is also reduced by 15.2 degrees Celsius.During the charging process of the lithium battery,the temperature of the lithium battery is always ensured within a safe operating temperature range,thereby ensuring the safety of the lithium battery in a state of rapid charging in 100 stages.Finally,considering the complexity of the 100-stage current change process in the actual charging process of the lithium battery,it is difficult to implement,and the 100 stages must be simplified.By performing regression line analysis on the charging current of the 100 stages,the final simplified charging strategy becomes 13 stages.According to the 13 stages of constant current charging strategy,the lithium battery is further optimized for charging and obtained by orthogonal test.Test combination of optimal charging current.The objective function of the orthogonal experiment is obtained by the output of the fuzzy controller,and is used as the basis for judging the charging strategy of the lithium battery.Finally,the optimal charging strategy is obtained.Compared with 1C constant current charging and 100 stage strategy charging simulation experiments,the results show that the 13-stage constant current charging strategy is not only better than 1C constant current charging,but also compared with the previous 100 stage charging strategy.The charging time is shortened by 26 seconds,basically unchanged.Comprehensive consideration,the 13-stage lithium battery charging strategy obtained in this paper can simplify the lithium battery charging strategy,and greatly shorten the charging time and effectively reduce the temperature rise of the lithium battery.