Research On Equivalent Modeling And State Of Health Estimation Of Aviation Lithium-ion Batteries

As the application of the lithium-ion battery in aerospace field becomes more and more widespread,the working safety and performance has been widely concerned.In order to ensure the safe working,it is necessary to carry out effective battery management,which is conducive to ensuring battery safety,improving battery efficiency and reducing battery damage rate.The equivalent modeling and the State of Health(SOH)estimation are two very important parts of the Battery Management System(BMS).The equivalent modeling is the foundation and cornerstone.The SOH estimation is the core of the BMS,and its estimation effect reflects the effectiveness of the BMS,which is also the key issue in aviation lithium-ion battery management system.In this thesis,the following research has been carried out for the equivalent modeling and the SOH assessment of aviation lithium-ion batteries.(1)The operating characteristics and influencing factors of the SOH for aviation lithiumion battery are analyzed.The open circuit voltage,battery capacity characteristics and working characteristics at different temperatures are obtained through experiments,laying the foundation for the equivalent modeling of aviation lithium-ion batteries.The SOH variation of lithium-ion batteries under the influence of the number of charge and discharge cycles,different charge and discharge multipliers and different ambient temperatures is explored.(2)In order to accurately describe the dynamic characteristics of aerospace lithium-ion batteries,an improved M-Thevenin model considering charge-discharge differences is proposed on the basis of the Thevenin model.By introducing the charge-discharge difference module,the voltage error brought to the model by the different charge-discharge open circuit voltages is solved.Based on the established model,online and offline identification is conducted separately,and the effectiveness of the model is finally verified.(3)The two time-scale Adaptive Dual Extended Kalman Filter(ADEKF)algorithm is proposed for the SOH evaluation of aviation lithium-ion batteries.This algorithm reduces the computational complexity of the algorithm and achieves the accurate estimation of the SOH by estimating the battery capacity and state of charge from different time scales.The SOH estimation method is considered to combine two perspectives of ohmic internal resistance and battery capacity to jointly evaluate the SOH of the aviation lithium-ion batteries,and the SOH estimation results are corrected by using weighting coefficients.(4)Combining complex working conditions to verify the algorithm effect.The multipower complex operating condition and the simulated operating condition of aviation lithiumion batteries are carried out by the experimental platform,and then the algorithm is verified under the above operating conditions respectively.The outcome indicates that the multitimescale ADEKF can effectively predict the SOH of aviation lithium-ion batteries.The effect of joint estimation of SOH for two reference quantities,ohmic internal resistance and capacity,is validated,and the outcome indicates that the method can reach a certain correction effect on the two evaluation effects.Through the above research,an equivalent model that can precisely characterize the dynamic properties of aviation lithium-ion batteries is established and the SOH is accurately estimated.The maximum error of SOH estimated by the two time-scale ADEKF algorithm is within 3.73% and the average error is less than 1.90%,which provides an effective basis for the safety management of aviation lithium-ion batteries.