Research On Echelon Use Battery State Assessment Method

Electric vehicle with lithium-ion batteries still has certain using value after retirement,the lithium battery appearance intact,no damage,the functional components under the premise of effective will be retired lithium-ion batteries use arrangement in the renewable energy power generation energy storage,low-speed electric cars,household use energy storage as well as the emergency power supply and so on scene,not only can decrease the cost of lithium-ion battery,and is beneficial to environmental protection and energy conservation and emissions reduction.In this paper,the retired ternary lithium ion batteries of electric vehicles are taken as the research object,and the battery cells that meet the echelon utilization standards are preliminarily screened out under the test conditions of environmental temperature change,charge and discharge ratio and self-discharge and other factors.The battery model was established,and the healthy SOH and SOC of the battery were estimated based on the specific operating conditions of the battery echelon.Specifically,the following research work was carried out:First of all,to the energy storage battery internal resistance,capacity,voltage,discharge platform time carries on the summary analysis,ratio performance such as performance index,design implementation from electric cars retired ternary lithium battery selection scheme,by off-line testing battery appearance,capacity and internal resistance can be screened out in the form of arrangement in use in the grid side the retired battery energy storage system,and make arrangement in use of battery failure and safety analysis.Secondly,the working principle of ternary battery is analyzed,the battery modeling methods and characteristics are listed,and the definition of SOH and its practical significance in the study of battery echelon utilization are expounded.In order to identify the echelon utilization of the battery degradation state online,the Rint equivalent battery model was built,the parameters of the open circuit voltage and internal resistance of the battery were identified online by kalman filter algorithm,and the available capacity of the battery and SOH were monitored online by ocv-soc curve.Thirdly,by comparing the advantages and disadvantages of various battery models,the second-order davenan equivalent circuit model with higher accuracy was selected,and the battery characteristic parameters in the equivalent circuit model wereidentified.The results of model parameter identification under different aging degrees were compared,laying a foundation for the accurate estimation of SOC for echelon utilization of batteries.Finally,on the premise of describing the practical significance of SOC estimation for energy storage battery management,several popular SOC estimation methods are listed.Based on the battery equivalent circuit model established above,the method of Sliding mode observer was selected to estimate the SOC of the battery,and the observability of the system was analyzed.Based on the observability,the slide-mode state observer was designed,and a state-coordinated SOC estimation method with SOH online update was proposed.At last,Matlab/Simulink software was used for experimental verification and simulation to compare the SOC estimation error of the battery under a certain aging degree without SOH update,so as to verify the superiority of the state coordination estimation algorithm.There are 55 figures,6 tables and 86 references in this paper.