Research On SOC Estimation Strategy And Active Equalization Technology Of Lithium-Ion Battery

As the main power of electric vehicle,lithium battery affects its driving reliability and endurance.Reasonable management and control of lithium battery is also the key to solve its own inconsistency and ensure the safety of lithium battery pack in electric vehicles.In this paper,model parameter identification method,SOC estimation strategy and equalization control system are studied.Firstly,this paper mainly analyzes the working principle of the battery and establishes the equivalent circuit model according to the related electrochemical characteristics.Taking online identification of battery as the focus of this paper,the state space equation is established according to the equivalent circuit model,and the whole identification process is simulated and analyzed by FFRLS algorithm in MATLAB environment.Secondly,the estimation method of battery SOC is introduced in detail.Each method is analyzed in principle and verified by simulation and error analysis in MATLAB/Simulink environment.By comparing the advantages and disadvantages of different methods,a new SOC estimation strategy based on noise estimation is proposed in this paper.The theoretical derivation of the estimation strategy is detailed,and the simulation and experimental verification are made based on the actual working conditions.Then,this paper designed the battery equalization system,introduced the battery equalization technology.Taking active equalization as the focus of this paper,the cascaded bidirectional Buck-Boost circuit is determined as the main equalization circuit and an adaptive digital-analog hybrid control strategy based on fuzzy PID is proposed.The parameters of fuzzy PID controller are designed and the fuzzy PID control model based on equilibrium topology is built by Simulink.Then the digital-analog hybrid control strategy adopted in this paper is introduced in detail.Finally,the battery equalization system experimental platform was built,the selection of lithium battery was completed and the parameters of the main power equalizer circuit were designed.The hardware circuit and software system are designed according to the modules involved in the battery equalization system.The equalization system works under charge equalization,discharge equalization and static equalization to verify the feasibility of the theoretical analysis in this paper.