| Lithium-ion batteries have the advantages of high energy density and low self-discharge rate.They are ideal batteries for power grid energy storage.Lithium-ion batteries may cause thermal runaway under abusive conditions and cause safety problems.The sensor installed outside the lithium-ion battery pack cannot sense the internal temperature of the battery in real time,thereby preventing the timing of thermal runaway from occurring.Existing research results show that the method of measuring the AC impedance phase shift of a battery can be used to sense the internal temperature of the battery online in real time to realize early warning of thermal runaway and allow time for preventing thermal runaway.In this paper,a lithium-ion phosphate battery for grid energy storage is used as an example to study the calibration method and application of the lithium-ion battery AC impedance phase shift and the internal temperature of the lithium-ion battery.The main contents include:(1)Analysis of energy storage power stations and lithium-ion batteries.The function of the energy storage power station in the power system is analyzed,and the supporting facilities of the lithium-ion battery energy storage power station are introduced.And the basic working principle of lithium-ion batteries,the models of several lithium-ion batteries and the parameters of several lithium-ion batteries are analyzed,and the heat generation and heat transfer of lithium-ion batteries,as well as the thermal runaway process and the danger of fire are analyzed.(2)Research on the internal temperature calibration method of lithium-ion batteries.A calibration scheme for the relationship between the AC impedance phase shift of the lithium-ion battery and its internal temperature is designed,and a lithium-ion phosphate battery for power grid energy storage is used as an example for experiments.After experimental research,the internal temperature calibration excitation frequency is selected as 70 Hz,and then a mathematical model of the relationship between the 70 Hz impedance phase shift and the internal temperature is obtained.For this type of lithium-ion battery,the internal temperature is effective in a temperature range below 65 ?.It provides conditions for the on-line measurement of the internal temperature of this type of lithium-ion battery in grid energy storage applications.The calibration method given in this paper can also be generalized to the internal temperature calibration of similar types of power grid energy storage lithium-ion batteries.(3)Calibration method application and user interface development.The mathematical model of the relationship between the impedance phase shift and the internal temperature of the lithium-ion battery obtained from the experiment is used to measure the internal temperature of the lithium-ion battery during the charge and discharge and charge-discharge processes,and compared with the surface temperature of the lithium-ion battery.The effect of this method good.A user interface was developed to facilitate integration with the battery management system. |
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