Development Of High-precision Detection And SOC Estimation Equipment For Energy Storage Battery Packs

With the development of industrialization and urbanization,electric vehicles have increasingly become the focus industry of various countries.As an important energy storage original component of electric vehicles,lithium-ion batteries still have a series of related problems that restrict the development of the electric vehicle industry.In order to study the lithium-ion battery under different operating conditions and improve the efficiency and safety performance of the battery,a battery management system(BMS)for the estimation of the state of charge(SOC)of electric vehicle batteries was designed.The device is very necessary to study.In this paper,a ternary lithium battery with a rated capacity of 42 Ah is used as the target battery for related tests.The basic working principle of lithium-ion battery charge and discharge and the basic characteristics at different temperatures and discharge rates are introduced.This article also introduces and compares some commonly used battery models.Finally,a more accurate and practical Thevenin equivalent model is used to describe the lithium-ion battery;a charge-discharge characteristic test for parameter identification is designed.The basic parameters required for Thevenin model are identified based on the least square method offline,and the parameter identification results are given.The working principles of linear Kalman filtering and extended Kalman filtering(EKF)are studied.The calculation formula of EKF estimated SOC is derived based on the battery operating in a nonlinear system and the battery equivalent model.The model simulation is established in the environment of matlab/simulink,and the results prove that the EKF algorithm can converge well near the true value and has good accuracy.A high-precision synchronous data sampling device is designed for the detection of battery state parameters.The battery voltage and current parameters can be measured with high precision through a hardware circuit,which overcomes the problem of the current BMS technology for the time and cycle detection of voltage and current.The software program of each module is designed and the design flow chart is given.The working process of the main program,AD acquisition program,CAN communication program and SOC estimation program is given.Finally,a test bench was built to carry out some necessary test verifications.The results prove that the device can well complete the high-precision data detection function and communication information transmission function,and has certain practical application value.