Design Of Battery Management System For Lightweight Electric Vehicle And Study On SOC Estimation And Balance Technology

Lithium-ion batteries have been widely used in the field of electric vehicles because of their clean environment,high energy density and low self-discharge rate.To ensure the safe and reliable operation of Lithium-ion batteries,an effective battery management system(BMS)is required.In order to design a safe and efficient management system for Lithium-ion batteries,this dissertation makes the following research on Lithium-ion batteries as the object of study:1.The working principle of the battery and the choice of the lithium battery type are introduced.The capacity,charge and discharge,and voltage characteristics of the lithium battery are tested and analyzed respectively.At the same time,the relationship between the open circuit voltage(OCV)and the charging state(SOC)is obtained by the static method.Based on the working characteristics of Lithium-ion batteries,the second-order RC circuit equivalent model is established and improved.2.Recursive least squares(RLS)is used to estimate the parameters of the battery model and update the battery health state(SOH),then three Kalman filter algorithms are combined to estimate the SOC of Lithium-ion batteries.After comparing the estimation results,the Cubature Kalman filter is selected as the SOC estimation algorithm.3.After introducing the inconsistency of Lithium-ion batteries and the commonly used equalization methods in detail,a new type of power balancing topology based on non-isolated bidirectional DC/DC converter is proposed.The equalization principle of the equalization circuit is mainly studied,SOC is selected as the equalization variable,and an active equalization strategy is presented.4.In the aspect of hardware design,the microcontroller STM32F103 is selected as the main controller of BMS,and the BQ76930 chip collects the battery parameters,and designs each part of the circuit according to the functional requirements.In software design,under Keil uVision5 development environment,write BMS control logic code;Design monitoring screen in Visual Stdio development environment.Finally,build a BMS test platform and design an experimental verification system function.The results show that the platform can achieve the function of data sampling,SOC estimation accuracy is within the required range,and the battery balance performance can also meet the system requirements.