Research And Design Of Advanced Lithium Battery Management System For Remotely Operated Vehicle

Energy shortage and environmental pollution are two major obstacles to sustainable human development in the 21st century.General Secretary Xi Jinping emphasized in his report of 19th Communist Party of China National Congress that developing clean energy is an important task for improving energy structure,ensuring energy security and promoting the construction of ecological civilization.Lithium-ion batteries are characterized by small size,light weight,high energy,no memory effect,no pollution,small self-discharge and long cycle life.They are excellent clean energy sources.Based on the research and project of remotely operated vehicle,the characteristics of lithium iron phosphate battery,the estimation of state-of-charge and energy balancing strategy are studied.A lithium battery management system for ROV is designed in the laboratory environment and tested with ANR26650M1-B battery,which verifies the feasibility of the system.Starting from the working principle and charging and discharging characteristics of LiFePO4 batteries,the standard 1C rate charging experiment,standard 1C rate constant current discharge experiment,different rate discharge experiment at the same temperature,different rate discharge experiment at the same rate,different temperature discharge experiment and pulse discharge experiment at different rate for 2.5Ah lithium iron phosphate batteries were carried out.According to its charge-discharge characteristics,the second-order RC equivalent circuit model of LiFePO4 battery was established.At the same time,the relationship between OCV and SOC is obtained by fitting the battery OCV curve with MATLAB cftool.Ohmic internal resistance R0,polarization internal resistance R_p1/R_p2 and polarization capacitance C_p1/C_p2 were obtained by identifying battery parameters.Then,through the analysis of several common SOC estimation theories in engineering,Extended Kalman filter is selected as the SOC estimation method in this paper.The battery simulation model is established in MATLAB/Simscape simulation environment,and the simulation results of estimating SOC by EKF are obtained.The error between EKF and the real value is less than 5%of the project requirements,which shows the practicability of EKF.In addition,according to the 4P-4S battery pack structure,the multiple transformers equalization circuit based on the bidirectional flyback converter structure is selected to achieve SOC balancing by analyzing the advantages and disadvantages of several non-dissipative equalization strategies.Finally,in practical application design,this paper uses dsPIC30F series MCU as the central processing unit to control the whole circuit.LTC6804 battery monitor and ACS711Hall sensor are used to collect voltage and current data respectively.And achieving serial communication between MCU and PC through RS-232 interface.In addition,the GUI of battery monitoring system was developed by LabVIEW which can display the parameters of the battery during charging and discharging in real time.In the experimental environment,SOC estimation and energy balancing of ANR26650M1-B battery pack were carried out to verify the detection function of BMS,and the design of intelligent lithium battery management system for ROV was completed.