Research On Open-Switch Faults Diangnosis Based On Hybrid System Model In Traction Inverter

With the rapid development of electrified railways in China,the reliability of AC electric traction drive system plays a vital role on trains' safe operation,which is due to its conducting as a power source on the train.However,in the main circuit of traction drive system,the insulated gate bipolar transistor(IGBT)modules often break down,which could lead to abnormal operation,even stopping and some other unexpected accidents.In order to locate the fault quickly,reduce the operation cost of maintenance and replacement,it is very important to study the online fault diagnosis methods of the traction drive system.Considering the limitations of the existing diagnostic methods based on signal method and analytical model,this paper presented two methods of IGBT open-circuit fault diagnosis for traction inverter based on hybrid model.Firstly,the IGBT-based traction inverter was studied in this paper,and the causes of their failure were briefly described.Then through comparing the three-phase currents in the inverter under normal and faulty conditions,the single IGBT fault,the double IGBTs fault and the multiple IGBTs fault were respectively analyzed in detail.Also,their impacts on the system were explored,which could provide the theoretical basis for real-time fault diagnosis.Secondly,the switched system model of the inverter and motor was built to observe the Residual's variation of three-phase currents,which was based on switched system modelling method with IGBT switching signal being defined as the discrete variable.Based on the current variation rule,the current residual table is created to locate the fault,and the threshold was set to restrain the impact of noise and measurement error.Thirdly,through introducing the controlled node,the nonlinear traction inverter was modelled by the hybrid bond graph.Based on the model,a system behavior constraint equation conforming to the conservation of energy was derived.Based on the system behavior constraint equation,the current behavior of the system is identified by the least squares method.By comparing the actual behavior with the expected behavior of the system,the fault identification vector can be produced,and the fault IGBT can be recognized.Finally,simulations of the above IGBT fault diagnosis algorithms were carried out in MATLAB/Simulink.The simulation results were consistent with the theories,which further demonstrated the feasibility of the diagnostic algorithms.According to the diagnosis results,the method based on switched system modelling was simple and effective without additional sensors,but it was suitable only for the single IGBT open circuit fault.The method based on hybrid bond graph had a fast speed of detection,and it was suitable for the single IGBT open-circuit fault case as well as the double IGBT open-circuit fault cases.