Fault Diagnosis Of Power Lithum-ion Battery Pack Based On Hybrid System Mode

Real time fault diagnosis of power Lithum-ion battery pack ensures a battery system in normal and safe operation.Due to the battery back is a hybrid system actually,multiple forms of coupled fault may appear,including continuous fault and descrete fault.How to diagnose all of the coming faults rapidly and effectively is necessary to battery pack.This thesis studies the comprehensive fault diagnosis problem focuses on power Lithum-ion battery pack based on a hybrid system framework,and a series methods of identification and diagnosis aming at different fault mode are presented.Continuous faults and descrete faults are both solved,which has been separately verified by experiments.Firstly,basic characteristics of power Lithum-ion batteries are introduced before establishing the 1-order RC equivalent circuit model of battery.Parameter identifiability of the model is discussed,and state estimation and parameter identification approaches are analysed.Secondly,an approach of estimation of time-varying parameters and fault diagnosis UTSTF algorithm is proposed.The diagnosis procedure is designed according to UTSTF.Reliability analysis of the diagnosis approach is also completed.Experiment for simulating fault occurrence is conducted under DST profile.Results of UTSTF and UKF are compared with true value,which verifies the proposed algorithm achieves a good tracking performance,diagnosis speed and reliability.Then,an approach of inconsistency identification and diagnosis of the series-connected lithium-ion battery pack is proposed based on STF and adaptive LM algorithm.STF is established for obtaining the state estimation and parameter identification of the reference cell.Through discussing state similarity between the rest cells and the reference cell,adaptive LM algorithm is applied to identify inconsistent parameters of the rest cells,meanwhile diagnosis method of inconsistency fault is formed.Battery inconsistency experiment is conducted under DST and FUDS profiles.Results show that the proposed approach achieves a good convergency,the diagnosis method is reliable.Finally,a descrete fault diagnosis approach of battery pack based on a hybrid diagnoser is reviewed.Two examples aming at relay fault and sensor fault of battery pack provide the hybrid diagnosers and diagnosis procedure through establishing an in-loop diagnosis verification platform.State and parameter estimation module and diagnosis module under continuous system of battery pack are also considered.Experimental results not only verify the validity of proposed approach,but also set up a comprehensive fault diagnosis structure of power Lithum-ion battery pack based on hybrid system.