Research On The Technology Of EMC NPC Three Level Inverter Multi Model Fault Diagnosis

The NPC (Neutral point clamped) three-level inverter with low switching stress, small output harmonic, topological stable etc, as to it, not only being applied in the EMU train, is also widely used in various occasions such as high voltage, high power. The diagnosis of faults is the basic premise of normal, stable, high efficient work. At present, the research situation of fault diagnosis has reached a new level at home and abroad, the NPC inverter is the first choice object. After reviewing and analyzing the literature about the switch tubes’ fault diagnosis of the main circuit on the NPC three-level inverter.I have an understanding with a clear and comprehensive about the disadvantages on a variety of diagnostic techniques.And this paper presents a scheme of fault diagnosis technology based on wavelet analysis and neural network.Firstly, this paper summarizes the principle of NPC three-level inverter and SPWM /SVPWM control methods, for the control strategy of svpwm being applied on the NPC three-level inverter, having been explained step by step; secondly, analyzing the fault types of power switch tubes on the main circuit of NPC in detailed, and the simulation of all kinds of faults is carried out in MATLAB. So I have get the symmetry rules that the voltage waveform, and give the proof in mathematical; finally, for the fault diagnosis of NPC inverter, selecting the scheme that based on wavelet packet and BP neural network.Because the fault conditions of the power tubes on main circuit of the NPC three-level inverter are very complex, so they are divided into typical and atypical fault. And the simple logic table only can solve the problem of the typical fault diagnosis. As to the atypical fault, getting the processing method based on wavelet analysis and neural network, and in order to improve the speed and accuracy of neural network algorithm, the BP algorithm been improved.The results of fault diagnosis about the neural network and wavelet analysis show the scheme is correct. At last, I have designed the platform of NPC inverter based on the TMS320F2812 of DSP, and testing the faults of the main circuit of the NPC three-level inverter on it, so getting the fault waveform and the results, which verify the scheme of fault diagnosis is correct and effective based on the logic table and BP neural network.