Research On Peak Power Test Method And Optimal Control Of Lithium-ion Battery For Rail Transit

With the development of rail transit and power battery new energy technology,rail transit has become the preferred mode of transportation for residents because of its advantages of speed,safety,comfort and capacity.Lithium-ion batteries have strong advantages in energy density,cycle life,energy saving,green environment protection and so on.Promoting the use of lithium-ion batteries on rail transit trains will alleviate the serious problem of energy consumption at present,and power batteries can also recycle braking energy and improve the efficiency of train operation.As the main power source of rail transit train,the power optimization control of lithium ion battery system is an important guarantee for the safe and reliable operation of rail transit train.In this paper,three main test methods for peak power of lithium-ion batteries have been completed,including HPPC test,JEVS test in Japan and time constant current charge-discharge test.On the basis of comparing and analyzing the experimental data of different test methods,an improved JEVS test method in Japan has been put forward.Taking the peak current data of time constant current charge-discharge test as the reference value,the improved JEVS test method in Japan has been verified.Considering temperature,SOC and component parameters of equivalent circuit model,a multivariate linear regression model was established to estimate the peak current of lithium-ion batteries.Based on diesel generator set model,power battery equivalent model and power battery thermal model,the optimal power control of lithium-ion battery system for hybrid electric vehicles is achieved by using particle swarm optimization(PSO)with the aim of maximizing energy saving rate under all operating conditions.The results show that the optimization control method with SOC,peak power and temperature as boundary conditions can improve the efficiency of diesel engine by 0.6%,ensure the safety of energy storage system and prolong the service life of power battery.Based on the thermal model of power battery pack and the kinematics model of train,the optimal power control of pure electric train system is completed with the objective of minimizing the temperature rise of battery energy storage system under the condition of full line operation.The results show that the power control method of pure battery system based on kinematics model can ensure the vehicle to complete self-traction work under special conditions such as long distance or large ramp under pure battery mode,and provide the basis for the configuration of vehicle energy storage system and the optimal control during operation.