| As an energy storage element with high power density,high energy density,long cycle life,and environmental friendliness,lithium-ion batteries have been widely used in electric vehicles and rail transit.Because the safety,cycle life,peak power,and available capacity of lithium-ion battery have a strong coupling relationship with the battery temperature,it is essential to equip the battery with a good thermal management system during use.Especially now,lithium-ion batteries tend to large-capacity,high-power,and high-current development.Therefore,a scientific and effective thermal management system is particularly important.In order to solve the problems of design and online monitoring of lithium-ion battery thermal management system,several commercial lithium-ion batteries are used as the study.A thermal simulation model and an online model for estimating the core temperature and heat generation rate of the battery are established,based on coupled thermoelectric theory.The main research contents are as follows:Firstly,in view of the problem that traditional thermal simulation methods cannot achieve real-time correction of heat generation power based on battery temperature,a coupled thermoelectric model of the battery is established based on the terminal voltage model and heat generation power equation of the lithium-ion battery,with a commercial lithium titanate cell token as the research object.And the temperature correction link to the heat generation rate is introduced,forming a closed-loop coupling from "electricity" to "heat" to "electricity" to achieve accurate modeling of the battery’s thermal behavior.Secondly,based on the thermoelectric coupling process of the battery,a collaborative simulation framework combining circuit simulation and computational fluid dynamics simulation is proposed.In the simulation process,the synchronous correction of the heating power of the lithium-ion battery is applied to achieve the purpose of accurately modeling the thermoelectric coupling process of the battery,thereby providing a scientific prior tool for the development and design of the thermal management system.Based on the existing simulation framework,the heat transfer analysis of battery cell is performed at different temperatures,different C-rates,and dynamic driving cycle to verify the effectiveness and accuracy of the proposed simulation framework.Besides,the heat transfer simulation for the battery modules used in the actual project,and the simulation analysis of the heat dissipation efficiency of tab cooling are performed to provide a reference for the development and design of its thermal management system.Finally,to solve the problem that the thermal management system cannot monitor the battery core temperature or heat generation rate,based on the "two-stage" simplified heat transfer model,the heat transfer state equation of the lithium-ion battery is derived.Recursive least squares algorithm and Kalman filter algorithm are applied to realize the online estimation of the thermal property parameters and core temperature of lithium-ion batteries respectively,so as to provide a numerical reference for the safety warning of the thermal management system. |
