| The power battery pack and its application are one of the key factors that affect the development of electric vehicles.Among them,the lithium ion battery pack is a common vehicle power source for pure electric vehicles.Due to the inconsistency between lithium battery cells,the energy density and service life of batteries after grouping will be inferior to battery cells.In addition,in the actual use of the power battery pack,it is difficult to ensure that the work strictly follows the principle of shallow charging and shallow discharge.This will not only affect the safety of the power battery system,but also make the maximum capacity of the power battery pack available over time.It will decrease with the passage of time and deviate from the rated capacity.In order to better meet the requirements of electric vehicles for energy use and extend the overall service life of the power system,it is an important direction of research to carry out safe,reliable and efficient balanced management of battery packs.In this paper,the 18650 ternary lithium ion power battery is taken as the research object.On the basis of accurately estimating the state of charge(SOC),the design of the active and passive multilevel equilibrium topology is completed,and the corresponding equilibrium control strategy is matched.Finally,a combination of simulation and experiment is used to implement a passive and active multi-level equilibrium management system that uses SOC as the equilibrium variable.It can shorten the energy transmission path,reduce losses,and improve as much as possible under the premise of weighing costs and complexity.Balanced efficiency.Among them,the main research work is:(1)The technical parameters such as the actual capacity and coulombic efficiency of the HCYINR18650 ternary lithium battery were verified.Combined with the Thevenin equivalent circuit model,the OCV-SOC curve and RC parameters of the battery were identified and the SOC was used as the equilibrium variable.The advantages.(2)In order to meet the needs of the control variables of the balanced control system,an adaptive Gauss-Hermit filter algorithm is designed to update the SOC of the lithium battery in real time.Compared with the traditional Gauss-Hermit filter algorithm and extended Kalman filter This algorithm has higher estimation accuracy,can maintain the estimation error of SOC within 2%,and effectively control the filter divergence.(3)The existing equalization circuit structure is compared,the advantages of the active and passive multilevel equalization structure are elaborated and analyzed.simulation.The results show that,compared with the traditional passive equalization circuit,the equalization structure can shorten the equilibrium control time by about 58.2% in the static state.(4)Taking STM32 chip as the core MCU,a balanced management system with master-slave type as the overall architecture was designed.With LTC6804,hardware circuits such as acquisition module and equalization control module were designed.Through the equilibrium control test,it is verified that the equilibrium management system designed in this paper has the ability to improve the SOC consistency of the power battery pack. |
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