Graph Based Fault Propagation Analysis And Criticality Analysis For CRH5 EMU Traction System

High-speed train is the most important link between high-speed railway operation and passengers,Fault propagation mechanism investigation and hazard assessment of traction drive system,the most important subsystem in high speed train,is the fundamental condition of safely operation of the train.This paper carries out the study of fault propagation analysis and hazard assessment of CRH5 traction drive system.Firstly,due to the characteristics of traction drive system which mainly contains inverter,traction motor and gearbox,Bond Graph modeling technology is used to construct its closed-loop model.Simulation results show the reliability and accuracy of the system model,and the advantages on analyzing fault propagation mechanism of the system.Secondly,based on the Bond Graph model of the system,cause and effect relations between variables can be achieved.According to these relations,an open-loop directed graph model can be built.Two types of qualitative methods are adopted to investigate fault propagation mechanism of traction drive system.One is a method based on consistent path theory of signed directed graph and the other is based on forward and backward propagation of fault tree analysis.Due to the deficiencies of these two methods,a quantitative method based on grey correlation analysis is proposed.The simulation results show that the proposed quantitative method can seek out the most affected path in the open-loop system.In order to analyze fault propagation mechanism of traction drive system comprehensively,a closed-loop Petri net is built on the basis of the simplified directed graph constructed in the second chapter.Grey correlation analysis is adopted both in fuzzy Petri net and fault Petri net to do fault propagation reasoning analysis.After comparison of these two methods,a new quantitative method called fuzz fault Petri net which combines grey correlation analysis,fuzzy Petri net and fault Petri net is proposed.This method overcomes the problems of resources conflict and transition ignition repeatedly in traditional Petri net.When a fault occurs,not only the system structure but also fault propagation paths can be obtained by this method.Simulation result of IGBT open-circuit fault in inverter validates the methodFinally,a quantitative method of risk priority number is proposed to do hazard assessment of fault in traction drive system on account of the deficiencies of the traditional qualitative risk priority number method.In this method,mutual information is firstly used to do nodes importance assessment,occurrence probability ranking and effect severity ranking are calculated then to identify the fault rank.The proposed method is proved to be effective by simulation results and can provide basic information for system reliability assessment in the future work.