Research On Equilibrium Control Of Power Battery Management System

With the development of social economy,energy shortages and environmental pollution problems have followed,and the development of new energy vehicles has become an important strategic move of the country.Lithium-ion batteries have become the preferred power source for new energy vehicles because of their high specific energy and strong charge and discharge capability.They are widely used in new energy vehicles,and the batteries used in series are different due to differences.The inconsistencies in the factors have greatly affected the service life of the battery pack and the stability of the electric vehicle.Battery management system BMS(Battary Management System)is an important part of electric vehicles and belongs to the core controller of new energy vehicles.As one of the key technologies in BMS,equalization control technology is mainly used to effectively manage power sources.Improving the consistency of the power source and avoiding the occurrence of overcharging and over-discharging of the battery are crucial to the development of new energy vehicles.Therefore,in this research background,this thesis summarizes the current research status of equilibrium control by current scholars,and clarifies the research on equalization control technology from the two directions of equalization control strategy and topology structure,and studies the following contents:For battery pack inconsistencies,From the three processes of production,use and storage,the reasons for the inconsistency of the battery pack and the different characterization parameters reflected by the inconsistency are analyzed,and the methods for improving the inconsistency of the battery pack are summarized.By comparing and analyzing the characteristics of different equalization circuit architectures,the equalization control scheme based on Buck-Boost non-energy inductive hardware architecture is designed,and the control principle and calculation of topology parameters are analyzed in detail,and the switch tube is established and derived.The mathematical model between the air ratio and the equalization current is used for theequalization control strategy and simulation of the subsequent design;the OCV-SOC characteristic curve obtained by the open circuit voltage method and MATLAB fitting is used to study the characteristics of various equilibrium indicators.A hybrid variable adaptive fuzzy control strategy is developed,which mainly adopts the voltage and SOC double equalization variables,and combines the fuzzy control theory to design the control regulator separately,which makes up for the defect of the single variable design equilibrium strategy in the battery pack recycling process.Different stages can effectively eliminate the inconsistency of the battery pack;use Matlab/Sim Power Systems to build the equilibrium system model,verify the operation from three stages of static,charging and discharging,and compare it with the unbalanced control scheme to further prove the feasibility of the control scheme.Finally,the hardware and software of the BQ76940 battery monitoring management chip and STM32F407VET6 as the core of the equalization control system are designed.The equalization effect is tested from different stages by setting up the 8-cell battery experimental platform.The data obtained by the test has high precision and strengthens the equalization control scheme.The equalization effect further demonstrates the effectiveness of the scheme from the perspective of practical application and effectively improves the consistency of the battery pack.