Research On Active Equalization Technology Of Battery Management System

As the most common means of transportation in daily life,traditional oil-fired vehicles not only facilitate production and living,but also consume a lot of oil resources and cause serious air pollution.With the intensification of energy consumption and the deterioration of the ecological environment,the willingness of all sectors of society to save resources and protect the environment has gradually increased,so electric vehicles have once again entered the stage of history.Lithium batteries are the power core of electric vehicles,in order to meet the normal driving demand of vehicles,a large number of single cells are usually used in series and parallel,the lack of monitoring and management of battery packs,their inconsistencies not only seriously affect the driving quality of electric vehicles,there are also huge safety hazards,so battery management system is particularly important to improve battery pack performance and ensure battery safety.Taking lithium battery as the research object,this dissertation studies the active equalization technology in battery management system.Aiming at the inconsistency of lithium battery packs,starting from the characteristics of lithium batteries and their models,the ternary lithium battery is established as the research object,the equivalent model is constructed through parameter identification,the causes and solutions of the inconsistencies are introduced.The existing balance management technology is summarized in detail,the balance variables of balance management are compared,and the working voltage is finally selected as the balance indicator,which lays a good foundation for the subsequent research on active balance technology.This dissertation analyzes the working principle of the traditional LC equalization circuit in detail,and summarizes its advantages and disadvantages.In order to improve the problem that the amplitude of the equalization current is limited by the battery voltage difference and the slow equalization speed at the end of the equalization,this dissertation designs the boost LC equalization circuit to improve equalization speed,and analyzes the influence of system parameters on the equalization current;in the process of research,its equilibrium state is optimized,and the boost dual-LC equalization circuit is proposed to further increase the equalization speed.The simulation analysis in MATLAB verifies its feasibility.According to the characteristics of the proposed equalization circuit,two control strategies of double closed-loop control are adopted to control the equalization voltage and the equalization current respectively,which provides a basis for the balancing strategy design of the equalization circuit under complex working conditions.Based on the research on the equalization circuit,it is combined with the switch array to form a centralized equalization system and a corresponding scheme for the equalization system is designed to achieve the balance between multiple batteries.The feasibility of the equalization circuit control strategy,the equalization system and its scheme are verified through simulation experiments.According to the characteristics of the equalization circuit and the equalization system,an experimental platform is established.The working voltage is used as the equilibrium variable,in the static state,the individual equalization circuits are used to verify each equalization circuit,the battery voltage data is recorded by the host computer,the results verify the proposed method and the improvement of the equalization circuit in the equalization speed indicates the correctness of the design of the equalization circuit.Then,the boost LC equalization circuit is used as an experimental platform to test the control strategy of the equalization circuit.The experimental results show that the equalization strategy can accurately control the equalization voltage and the equalization current.Finally,three batteries balancing is taken as an example to verify the practicability of the equalization system design.