Equalization System For Series Power Batteries Based On Direct Equalization Technology

With the increasing fossil raw materials,lithium-ion series power batteries is widely used in electric vehicles,clean energy storage,high-power equipment,emergency power supply and other important areas,as the current energy storag e is an important means.The existing difference between each cell of series power batteries gradually increase in the course of using,resulting in unbalanced state of charge between each cell,accelerating the aging process of batteries and endangering the safe operation of the whole system equipment.Therefore,research on equalization system for series power batteries is of great significance.Based on the current research status quo of equalization system,this paper presents a new direct equalization circuit which can realize the direct equalization of any two battery cells in series power batteries.There are three kinds of work patterns: Buck-Boost mode while adjacent cell,flyback mode while two odd or even cell,flyback mode while two non-adjacent cell.The equalization efficiency of the new direct equalization circuit is quantitatively analyzed.The simulation model is established by using Pspice software,verifying the correctness and rationality of the new direct equalization circuit and related theoretical analysis.This paper designs a six-cell direct equalizer at first.On this basis,the equalization system for series power batteries is designed.The circuit of six-cell direct equalizer and equalization system is built,while optocoupler isolation drive circuit is designed to solve the floating GND problem.The analog front end and system protection circuit is realized based on the BQ76930 chip.Aiming at the complex imbalance situation,the control method of voltage hysteresis is introduced and the switching action table of the equalization system is given,as the digital controller of the equalization system is designed.According to the theoretical analysis and the design of hardware and software,this paper builds a experiment platform,completing the equilibrium function experiment and whole equilibrium process experiment.The equilibrium experiment effectively reduces the voltage difference between the cells and solves the problem of inconsistency between the cells.