Open-switch Fault Diagnosis Based On Mixed Logical Dynamic Model In Single-phase PWM Rectifiers

With the large-scale service of high-speed electric multiple units(EMUS),the operation security of high-speed EMUs has become an important part of the performance improvement.The electric traction drive system with high security is one of the core systems of high-speed EMUs.In the electric traction drive system,the insulated gate bipolar transistors(IGBTs)in the grid side converter,which is a single-phase pulse width modulation(PWM)rectifier,have high failure rate.Therefore,it is very important to study IGBT fault diagnosis in single-phase PWM rectifiers to improve the safety of high-speed EMUs.In this paper,the single-phase two-level rectifier and single-phase three-level neutral-point-clamped(NPC)rectifier,which are widely used in high-speed EMUs,are concerned as the research objects.The IGBT open-circuit fault diagnosis methods in them are studied.First of all,the single-phase PWM rectifiers under all possible switching signals,different grid side current,grid side voltage and DC-link voltage conditions are analyzed.The discrete events including control transitions and condition transitions of the single-phase PWM rectifiers are established by using logic function.According to the continuous state equations,the continuous variables and discrete events constitute the mixed logical dynamic(MLD)models.Then,the MLD model is used to estimate the grid side current.The measured current substracting the estimated one generates the residual.The characteristics of the voltage,current and residual are analyzed by theory and simulation.For each IGBT fault of the single-phase two-level rectifier,the rate of residual change with the isolated switch signals is defined as the diagnostic variable.It is compared with the threshold to achieve diagnosis.For the single-phase three-level NPC rectifier,the rate of residual change is used as the diagnostic variable.The specific fault signal is extracted by specific switching signal injection method.The corresponding fault evaluation rules are established to realize fault localization.Finally,the proposed diagnosis methods for IGBT open-circuit fault are verified by simulation and field-programmable-gate-array(FPGA)based hardware-in-the-loop(HIL)simulation platform.The results show that the estimator can accurately estimate the grid side current,and the proposed methods can effectively diagnose the open-circuit faults of the single-phase two-level rectifier and single-phase three-level NPC rectifier.The proposed methods are insensitive to change of load,grid voltage and condition switching.