Study On SOC Estimation Method Of Lithium Iron Phosphate Batteries

The State of Charge(SOC)is a parameter that characterizes the remaining capacity of the battery and is a key factor in the overall management of the Battery Management System(BMS)in the energy management of the power battery.Therefore,the main content of this study is to accurately estimate the SOC.In this paper,the model of 18650,3.2V/1500 mA lithium iron phosphate battery was used as the research object,and its voltage characteristics at different discharge current rates and different temperatures were analyzed.Several existing battery models are briefly analyzed and Thevenin equivalent circuit model is selected.An improved equivalent circuit model is added to the model,in which the influence of simulated discharge current of controlled voltage source on open circuit voltage is added.The improved equivalent circuit model is verified and analyzed by discharging experiments at different rates.In this paper,the extended Kalman filter(EKF)algorithm is used to estimate the SOC of lithium iron phosphate batteries,and the algorithm is improved in order to improve the accuracy of SOC estimation.Then,the estimation results before and after the improvement of the algorithm are compared and analyzed through constant current and equal capacity discharge experiments.This paper designs the lithium iron phosphate battery test platform based on the DSP processor of TMS320F28335 model.The hardware and software part of the system is designed and verified by simulation and experiment.The results show that the platform realizes the functions of each sampling circuit,and the estimation accuracy of SOC is also within the design range.