| Lithium ion battery has become the first choice for power grid energy storage due to its advantages of good cycle performance and high specific energy.In recent years,there have been frequent fire incidents in electrochemical energy storage power stations.One of the reasons is the abnormal operation of individual cells,resulting in a transient increase in internal temperature and thermal runaway.Accurately obtaining the internal temperature of each single battery is of great significance for the safe operation of the energy storage power station.The common method for temperature detection of energy storage battery is to install the temperature sensor on the battery surface.Due to the influence of heat conduction lag,the simple surface temperature detection cannot realize the early warning of battery thermal runaway.In this paper,the mapping relationship between AC impedance parameters and internal temperature of lithium ion battery is taken as the starting point,and a method for estimating the internal temperature of energy storage battery based on impedance modulus detection is studied.The main research work is as follows:(1)Based on the analysis of the influencing factors of the internal temperature of the energy storage battery,an experimental method for the estimation of the internal temperature-impedance modulus of the battery was designed.Taking lithium iron phosphate batteries for energy storage in power grid as the experimental object,an AC impedance measurement experiment with SOC and temperature as control variables was designed and carried out.Through comparative analysis of the correlation between various ac impedance parameters and internal temperature,it is found that the correlation between the impedance modulus and internal temperature of the battery is stronger in a wide temperature range and is not affected by SOC.An experimental method for estimating the internal temperature of the lithium-ion battery for power grid energy storage based on the impedance modulus is determined.(2)The establishment and verification of the mapping relationship between the impedance modulus of the energy storage battery and the internal temperature.According to the data obtained by the experimental method,the impedance modulus and the internal temperature were fitted by the form of Arrhenius-like,and by comparing the fitting effect at multiple frequency points,a functional expression for estimating the internal temperature of the battery based on the impedance modulus was established.Meanwhile,combining with the linear relationship between the estimated temperature of the high temperature part and the internal temperature,a linear function with the estimated temperature as the independent variable and the internal temperature as the dependent variable is established,which is used to further fit the estimated temperature of the high temperature part(?85?).Finally,a single point ac impedance measurement experiment is designed and validated.The experimental results show that the relative error of the four batteries can be controlled within 6.5% in the temperature range of 60? and below.In the range of 60?100?,the relative error of the four batteries can be controlled within 10.5%.(3)Online application of estimation method.Firstly,the method is optimized for the problems existing in the actual application of the temperature estimation method.Then,the internal temperature of lithium ion battery under different working conditions was measured online by the method.The final result shows that the internal temperature estimation method of energy storage battery based on impedance modulus has a good online estimation effect. |
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