Traction Inverter Fault Diagnosis And Tolerant Control Strategies

The electric traction drive system is the originality of high-speed EMU and its reliability plays a vital role in safe and stable train operation. It is therefore that how to online monitor the traction drive system operating condition has drawn widely attention in practice. The power device, IGBT, is currently identified as the weak segment in traction drive system operation. However, some failure in this segment gives rise to a whole operation unit remove with respect of safe operation of EMU, which leads to power loss. Clearly, it has great engineering significance on the exploration of fault tolerant operation in the study of electric traction drive system. This dissertation will targets to the IGBT fault diagnosis and three-phase four-wire tolerant topology and the details are illustrated as followings:The dissertation firstly analyzes the influence of IGBT open circuit fault on three-phase current through the filtered the three-phase current by wavelet transformation and extract eigenvectors in addition to classification and position of fault by Support Vector Machine (SVM) during a fundamental-wave period. It forms the three-phase voltage measurement model based on the model of the Mixed Logical Dynamical (MLD) inverter and asynchronous motor to achieve the online diagnostic method that based on residual voltage failure in 3 to 5 switching periods. The model tests under three conditions in A phase bridge arm:(1) T1 failure, (2) T4 failure and both T1 and T4 failure. The failure data in half fundamental period will output when residual error is less than the threshold in fault diagnosis. Under the model of three-phase current measurement, the fault will be identified through threshold setting and fault diagnosis information table positioning when the switches have fault and then to compare and contrast the three diagnosis methods and its working conditions by shortening the diagnostic time to an eighth of fundamental-wave period.Secondly, when it is to consider limitations of traction converters weight and space, three-phase four-switch topology has the great potential in the traction inverter fault-tolerant control applications. To add 6 fuses and 3 bidirectional thyristors up to six-switch topology, when IGBT has short circuit faults or open circuit faults, it can isolate the fault and swift to three-phase four-switch topology. A compensation method is applied to solve the intermediate DC link imbalance which is caused by the output current imbalance following the topology structure analysis, working principles and the five-stage SVPWM control as well as the rotor field oriented control closed loop simulation.The last but not the least, the method of traction inverter IGBT open diagnosis and fault-tolerant topology have been tested when TMS320F2812 regards as controller and dSPACE hardware-in loop simulator does virtual load. Moreover, it has also proved the validity and effectiveness of diagnosis method and the feasibility of fault-tolerant topology.