Design And SOC Estimation Of Power Lithium Ion Battery Management System

The new energy vehicles represented by electric vehicles have become the future automobile development trend.As one of the key technologies for electric vehicles,the safety and efficient using of batteries depend on the accurate estimation of the battery status and the safety and rational design of the battery management system.The research on the key technologies of the battery management system is divided into two parts.There are the research of functional safety technology and the SOC core estimation algorithm.State of charge(SOC)of battery estimation is the most important part of the battery management system.Accurately estimating the battery SOC can prevent the battery from over-charging and over-discharging,prolonging the service life of the battery,and preventing the electric vehicle from stopping due to the error in the power estimation.Since the battery parameters and conditions changing in real time during operation,there is of great significance to establish an accurate battery model and to study accurate battery model parameters and SOC estimation methods.This paper focus on the battery model parameters and accurate SOC estimation algorithm for lithium iron phosphate batteries.The battery management system of electric vehicles is closely related to the safety of occupants.The system is particularly important in the context of accurately estimating the SOC.Therefore,based on the safety considerations,this paper introduces the idea of functional safety and analysis.The battery management system that meets functional safety requirements has been designed.The main research content has the following aspects:1.Based on the functional safety analysis and the functions of the battery management system,the concept phase and the system phase analysis were carried out.The battery management system architecture that meets the functional safety was obtained and the safety of the battery management system was ensured.2.Based on the working principle of lithium iron phosphate battery,the relevant experimental data,the key characteristics of lithium battery such as voltage characteristics,internal resistance characteristics,and efficiency characteristics are analyzed,and the SOC is defined;3.This paper build the battery model based on the classic battery equivalent circuit model and the characteristics of lithium iron phosphate battery.On this basis,the on-line method is used to identify the model parameters,and the effectiveness of the battery model is verified through simulation and experiments.Improve the accuracy of the battery model;4.Based on the established battery model,an extended Kalman filter algorithm is used to estimate the SOC.In the algorithm,according to write the SOC equation of state and detects the voltage and current data of the battery to correct the state variables in real time.And there is high accuracy,convergence and feasibility.In order to track the time-varying characteristics of the battery,this paper studies the battery model parameters and SOC dynamic estimation method,and through simulation and experimental verification battery model parameters and SOC dynamic estimation method has high accuracy and convergence.