| Lithium batteries are used as the power source of electric vehicles.In order to meet the power,voltage and capacity requirements of electric vehicles.Single batteries are generally used in series and parallel groups.However,due to the complexity of the battery production process and manufacturing process,even the same batch of batteries will be inconsistent.At the same time,the inconsistency between the single cells will be further aggravated due to differences in the working environment temperature during the battery pack use.It is necessary to use equalization technology to improve the inconsistency between the single cells.And solve the problems of reduced endurance of new energy vehicles and reduced service life of the battery pack due to the inconsistency of the single cells inside the battery pack.The thesis analyzes the factors that cause the inconsistency between the single cells in the lithium battery pack.Considering the effect caused by the inconsistency,and summarizes the specific performance of the parameters caused by the inconsistency between the single cells.The battery’s State Of Charge(SOC),open circuit voltage,and remaining battery capacity are used as balancing variables.Their advantages and disadvantages are analyzed at the same time.The working voltage is selected as the balancing variable of the active balancing control strategy of the battery pack.Then,the active balancing strategy of lithium battery pack is summarized.Analyzed and compared different balancing circuits,in order to achieve the goal of fast response and low cost.In this paper,an active balancing circuit based on active clamp forward converter proposed.Designing a novel switch driving circuit,which enables the switch to be normally on or off.So that the balancing circuit can charge any single battery for a long time through the gating of the switch array.This paper analyzes the different modes of the main circuit,and discussion the theoretical basis of soft switching of the main switch and its clamp switch.Designing the main parameters of the balancing circuit.And the experimental simulation model is builtby saber simulation software to analyze and verify the feasibility of the theory.Finally,the TMS320F28035 of Texas Instruments is used as the main control chip of the active equalization experiment platform.And design the circuit of the active balancing control system.Including the peripheral circuit of the main control chip,the voltage sampling circuit,the current sampling circuit,the auxiliary power supply circuit,the active clamp forward converter and the driving circuit of the switch array.Aiming at the active balancing experimental platform,the balancing control strategy is formulated,and the balancing algorithm is optimized.Taking the battery pack composed of 14 ternary lithium batteries in series as the experimental research object.Setting up the active balancing experimental test platform.And verify the feasibility and effectiveness of the balancing system designed in this paper through the results of the balancing experiment. |
