Research Of Fault Diagnosis In The Traction Converter Of CRH3 EMU

With the development in Chinese railway, the demand for the reliability and stability of the traction drive system, the high effectiveness of fault diagnosis and repair is also especially important. While the converter is one of the most important components of the traction drive system, its working performance directly determines the train operation safety. Therefore, it’s significantly important to research the fault diagnosis of the converter.Firstly, the theory of vector control is studied in the paper, and the model of the converter vector control is built through simulation, witch is based on the model of CRH3.The correctness of the model is verified by simulations of traction working and braking condition. Furthermore, though analyzing the fault principle of converter, the paper chooses the most typical fault, the open fault, as the research object, and the three-phase output current of different fault conditions, whitch is the basis for faut diagnosis, is saved by simulation. Then, the output current is decomposed by the wavelet analysis technique, and the energy coefficient and proportional coefficient is extracted from the low frequency coefficient as eigenvectors for fault diagnosising.Then, the paper discusses algorithms of the neural network and SVM. For the advantages of these two methods in dealing with nonlinear mapping, the paper put forward the fault diagnosis method by neural network and SVM based on wavelet transform. Finally,the paper demonstrates the effectiveness of this diagnostic modality via MATLAB simulation. In the simulation of neural network, there is a performance comparison analysis of BP network, GRNN network and RBF network.In the simulation of SVM, there is also several comparison analysis of parameter optimization in several different ways. The results show that these approaches can efficiently handle fault classification problem.Finally, the paper make a research on the fault-tolerant control strategies of converter based on four-switch three -phase circuit. The principle is analysed detailed and is verified by simulation. The simulation results shows that this circuit can slove the single switch fault and the double switch of the same bridge fault and the output performance by the fault-tolerant control is nearly the same as the normal condition. The function of real time data collection and treatment is realized by S-function after every part debugged successfully, then the whole system is simulated togetger. The paper also make a monitoring interface for fault diagnostic monitoring system base on VB software, and the monitoring interface is debugged by data saved by simulation. There is a deeply research from fault diagnosis to the manufacture of monitoring interface. This mode has a broad prospect of developing and applying due to the easy transplanted characteristics of MATLAB and VB language.