| With the advantages of pollution-free,low noise and high energy efficiency,electric vehicles have been popular and been promoted all over the world.However,the development of electric vehicles is restricted by the problems of short range and slow charging speed.The inconsistency of power battery pack seriously affects the available capacity and cycle life of battery packs.At present,although most of the management methods have achieved good equalization results,there is no equalization management method for different stages of battery pack.Therefore,aiming at the inconsistency of electric vehicle power battery pack.This paper studies the equalization scheme;emphatically analyses the characteristics of the inconsistency of battery pack in each stage;studies the equalization management mode in each stage;designs the equalization hardware circuit and management strategy,and builds a complete equalization management system.Aiming at improving the equalization time and voltage fluctuation amplitude of battery pack in each stage.The equalization effect of battery pack is improved.The main content is as follows:Firstly,in view of the reasons for the inconsistency of battery pack,this paper has analyzed the production,storage and usage stages of batteries.By discussing the variation law of the intermal state of batteries,the characteristics of the inconsistency of battery packs in different stages and the differences of the inconsistency in different stages have been studied.The existing methods to improve the inconsistency of battery pack have been compared,and the research of this paper has been put forward.According to the relationship between SOC and parameters in battery experiment data.The advantages and disadvantages of open-circuit voltage,working voltage and SOC in representing the inconsistency of battery packs have been compared and analyzed,and the open-circuit voltage and working voltage have been selected as equalization variables.Then,aiming at the characteristics of inconsistency in different stages,based on the study of battery pack equalization scheme,the corresponding equalization circuit structure and equalization management strategy were designed,and the working methods of equalization circuit have been analyzed.By exploring the law of voltage variation with current in experimental data,the equalization threshold was set for the equalization management strategy.Combining the parameters of the selected corponents and the working method of the equalization circuit,the control quantity of the equalization circuit has been calculated.By building battery model,equalization circuit model and equalization management system model,the feasibility of equalization circuit and equalization management strategy has been verified by simulation.Next,aiming at the integral structure design of the equalization management system,a two-tier management system architecture has been proposed,and the design index of the system function has been discussed.Through the design of functional indicators,the control chip was selected,The hardware of power supply,voltage acquisition,current acquisition,equalization and other modules have been designed.The software of the system and the host computer have been designed.Finally,based on the verification of the equalization management system and the equalization test bench,the equalization test methods of battery packs in shelf stage and charge-discharge stage have been formulated.The test data of the equalization management system under closed and open conditions has been compared and analyzed.The results show that after one hour of equalization management,the voltage range of each stage decreases by more than 40%compared with the system shutdown condition,which achieves the purpose of improving the consistency of battery packs.By comparing the relationship between voltage and SOC under different equalization currents,it is proved that the system can take into account the voltage fluctuation amplitude and accelerate the equalization speed in each stage. |
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