Research On Modeling,simulation And Equalization Control For Power Lithium Battery Of Electric Vehicle

When the global governments are paying more and more attention on energy security and environmental protection,the electric vehicles have gradually become an important development direction of the world's automobile industry.Due to the complexity of the battery manufacturing technology and production process,there are many differences in performance among battery cells.The battery management system is required to monitor and manage the battery pack.Battery modeling is the key to the development of battery management system.The battery model not only reflects the characteristics of the battery,but also provides support for the equalization control.The Li Fe PO₄ battery is taken as the research object to carry out characteristic analysis in this thesis.The improved equivalent circuit model considering hysteresis voltage and dynamic parameters is proposed to improve the simulation accuracy of the battery model.At the same time,a bi-directional flyback equalization control system based on coaxial windings transformer is designed to improve the inconsistency of the battery pack.The accuracy of the battery model and the effectiveness of the equalization control are verified with Matlab/Simulink.This study provides an effective means for the research and development of the battery management system in the electric vehicles.The main research is as follows:1.Working principle and performance parameters of lithium ion battery.The development of power battery is summarized.The reason why lithium ion battery becomes the mainstream of electric vehicle power battery is introduced.The working principle and performance parameters of lithium ion battery are analyzed.The power battery test platform is built to carry out performance test experiments.2.Study on modeling and parameter identification of power lithium battery.Based on the power battery test platform,the characteristics of Li Fe PO₄ battery are analyzed.Considering the characteristics of voltage hysteresis and the dynamic changes of battery parameters,an improved equivalent circuit model is proposed.The parameters of the model are identified through Hybrid Pulse Power Characteristic test,and the battery model is built in Matlab/Simulink to verify its accuracy.3.Analysis of the cause and state of the battery pack inconsistency.The causes and manifestations of battery pack inconsistencies are described.The evaluation indexes of battery pack inconsistencies are analyzed,and the harm of inconsistency to the performance of battery pack is summarized.The importance of equalization control to improve battery pack inconsistency is illustrated.4.Design and simulation verification of equalization control system.A bi-directional flyback equalization system based on coaxial windings transformer is designed,and an appropriate equalization control strategy is formulated.The simulation model is built in the Matlab/Simulink to verify the effectiveness of the equalization system.