The Analysis Of LiFePo₄ Battery SOC Estimation And Battery Management System

Lithium-ion battery is a kind of environmentally friendly and efficient chemical energy and electrical energy conversion carrier.Compared with the other two batteries,it has many advantages.It has been widely studied and applied in the field of scientific research and engineering.However,there are various kinds and different characteristics of lithium ion batteries at present.Some users and researchers are not enough to understand the characteristics of different lithium ion batteries,not enough estimation accuracy（accumulative error）for SOC,and the problem of passive/active power consumption in BMS and insufficient intelligence.The olivine structure of Li FePO₄ battery is studied and applied in this paper.First,the internal structure,working mechanism,main performance parameters and charge and discharge characteristics of lithium iron phosphate battery are introduced.Through the zero state response of the voltage and the zero input voltage response data before and after the battery pulse discharge,the dynamic data is calculated by combining the Curve Fitting Tool toolbox of Matlab software.The dynamic model of the two order RC equivalent circuit of the lithium iron phosphate battery is established.Secondly,the definition of SOC,the influencing factors and the method of estimation are introduced,and a variety of SOC estimation algorithms are analyzed in detail,and Matlab/Simulink simulation of lithium iron phosphate battery system.The dynamic characteristics of the battery are simulated by using the experimental data as the internal dynamic parameters of the battery.By setting the different initial SOC of 12 groups of lithium-ion batteries,simulating the pulse discharge condition of the lithium iron phosphate battery,using a variety of tracking filtering algorithms to track the battery SOC,the results show that the Multi-rate Strong Tracking Kalman filter method is superior to the other algorithms.Thirdly,the design of the lithium iron phosphate BMS is introduced in detail,and the battery management system PCB and the balanced PCB are analyzed and designed.BMS host computer software has been developed,and its functions of control,data recording and display have been realized.Hardware testing of multi class batteries has been done by BMS.Finally,the electromechanical system architecture of the battery management system is designed,which is realized as a large capacity battery power supply system which can work under water for a long time,and the underwater experiment is carried out.In the cold underwater environment,the successful operation of electromechanical equipment and intelligent control algorithm has good performance in charge discharge and active equalization.Based on deep water remote operation equipment,the electronic load is charged and discharged to ensure that the battery power system can provide power for underwater mechanical equipment.Through this study,the identification of the internal parameters of the lithium iron phosphate battery is more accurately realized,the dynamic characteristics of the different charge state of the lithium iron phosphate battery are established,and the accurate estimation of the battery SOC is realized.The user and the battery management system are used to obtain the exact residual battery power,which is convenient for the users to carry out the next operation and the intelligent management of the BMS;the battery tube is designed and realized.In the system,the BMS PC software is developed to monitor and manage the state of the power battery group,to realize the active balance of the low loss of the battery group and to protect the battery working in the safe range,so that the battery group is safer,more efficient and longer life.Therefore,the BMS has wide application fields and has certain economic value.