Research And Design Of Lithium-ion Battery Pack Charging And Equalization Control

In recent years,with the increase in the production level of lithium-ion batteries and the drop in cost,lithium-ion batteries have gradually replaced traditional lead-acid batteries and have begun to be used in large scale fields such as new energy power generation and new energy vehicles.Since the rated voltage of a single-cell lithium-ion battery is usually only a few volts,the battery cells need to be connected in series as a battery pack to meet the voltage level requirements of the above application scenarios.The inconsistency in the production,storage,and use of individual monomers in a battery pack,that is,individual differences in individual battery cells,can have a significant impact on the overall performance of the battery pack.Therefore,in the charging and discharging process,higher requirements are required for the rapidity and accuracy of the charging control in order to prevent overcharging and overdischarging of individual cells in the battery pack.At the same time,the inconsistency of the electrical characteristics of the individual cells within the battery pack during use must be solved with an efficient and low-cost balancing strategy.This dissertation analyzes the electrochemical characteristics and usage scenarios of the current large-scale lithium battery packs,and then elaborates the importance of precise charge control and battery pack equalization.On the basis of fully integrating the current status of various control optimization algorithms and battery balance control strategies at home and abroad,this dissertation proposes an ant colony optimization PID-based charge control method and an efficient cascaded lithium battery pack equalization strategy.The specific work of the dissertation is as follows.Firstly,the basic characteristics and key parameters of lithium-ion batteries are studied and analyzed.Further researches on lithium-ion battery models and common charging methods are carried out.On this basis,an intelligent fast charging scheme is proposed in combination with Mas's law,and a fractional-order PID charging control method based on ant colony algorithm optimization is designed.The simulation results show that the fractional-order PID controller can achieve more accurate charging current.In order to balance the application of large-scale battery packs,this dissertation analyzes in detail the causes,harms and typical processing methods of battery pack inconsistency.Based on this point,it proposes a balanced charging control method,and verifies its feasibility through simulation experiments.At last,the dissertation implements the hardware and the software designs of the balanced control system and lists the key components of the hardware circuit and value of the parameters.The hardware based on STM32 includes the main circuit,sampling circuit and power supply circuit.The software programs design includes the main program flow chart and several key subroutine flow charts.