Multilevel Inverter Fault Modeling And Diagnosis

As one kind of multi level inverters, three-level inverter is widely used in the high-power and high-voltage applications. However, the increasing of the power devices improves the system’s fault rate. How to ensure safe operation of the system has become an important research question.Using three-level diode-clamped inverter as an example, the paper analyzes operation mode and behavior patters of inverter under open-circuit faults under situation, and presents a technique of fault detection and diagnosis for open-circuit fault of power device in three-level diode-clamped inverter based on wavelet packet transform and neural network.Firstly, in terms of three-level inverter’s topology and work principle, fault types of inverter’s main circuit are analyzed in this thesis. The open circuit faults of power devices in main circuit are separated into nine types. Simulation analysis of these faults is implemented in MATLAB software, and some important conclusions are made. Secondly, after a brief introduction to wavelet analysis and neural network, their applications in fault diagnosis are analyzed. Finally, the fault diagnosis method based on wavelet packet transform and neural network is studied. According to wavelet packet transform theory, fault signal’s energy in different frequency band is extracted as input vector of BP neural network fault classifier for fault diagnosis of complex failure in the inverter. The simulation results show that the proposed method has excellent classification effect.