NPC three-level inverter fault diagnosis method based on improved-treelet transformation

Abstract

The invention relates to an NPC three-level inverter fault diagnosis method based on improved-treelet transformation. The NPC three-level inverter fault diagnosis method comprises the steps of: constructing an NPC three-level inverter circuit simulation model, simulating a fault process, measuring a voltage waveform of a bridge arm and using the voltage waveform as a fault signal; decomposing thefault signal into a plurality of IMFs components; carrying out Hilbert transformation on each IMFs component to obtain time frequency distribution and an amplitude of the IMFs component, and selectingthe first eight IMFs components; fitting out an envelope signal by using envelope analysis, and screening out fault characteristic parameters; carrying out optimization on treelet transformation by aGaussian kernel function, and generating characteristic vector samples which are independent of each other; and dividing sample data into a training set and a test set according to a ratio of 3:7, wherein the training set is used for constructing an SVM classifier model, and the test set is used for actually diagnosing a circuit fault. According to the invention, EEMD is adopted to decompose thefault signal, then Hilbert transformation is combined, and more frequency domain characteristics are collected; and the NPC three-level inverter fault diagnosis method is more suitable for processinga nonlinear and non-stationary signal generated by the three-level inverter circuit fault.0

Description

technical field [0001] The invention relates to the technical field of fault diagnosis of circuit devices, in particular to an NPC three-level inverter circuit fault diagnosis method based on improved small tree transformation. Background technique [0002] Compared with the traditional two-level inverter, the three-level inverter has the advantages of low voltage stress on the device, small electromagnetic interference, less harmonics of the output voltage and high inverter efficiency, but the three-level circuit uses More power switching devices will reduce the reliability of the circuit, and any device failure may cause the entire circuit to stop working, and even affect the safety of other circuits, causing immeasurable economic losses. Therefore, how to quickly detect the fault time and type, accurately analyze the fault signal, and realize the accurate positioning of the fault transient state and disturbance time is an urgent problem to be solved at this stage. [000...

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Problems solved by technology

In addition, once the basis function is determined, all signals must be processed with this basis function, and it cannot be adaptive

Chen Danjiang and Ye Yinzhong used Fourier transform method for fault feature extraction in "Multi-Neural Network Based Three-Level Inverter Device Open Circuit Fault Diagnosis Method" (Acta Electrotechnical Society, 2013, 28(6): 120-126) , Fourier transform is a global transform that can obtain higher resolution in the frequency domain, but it cannot give the change of frequency with time, and cannot meet the requirements of diagnosis in the time domain, making the diagnosis accuracy poor

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