NPC three-level inverter open-circuit fault diagnosis method based on instantaneous frequency

Abstract

The invention provides an NPC three-level inverter open-circuit fault diagnosis method based on an instantaneous frequency, and relates to the field of power electric appliance fault diagnosis. The method comprises the following steps: acquiring a three-phase output current on a grid side of an inverter, estimating the instantaneous frequency of the three-phase output current by using a weighted sliding Hilbert transform method, constructing an instantaneous frequency residual value in combination with a theoretical instantaneous frequency, and solving a mean value of the instantaneous frequency residual value; and obtaining a normalized current period mean value according to the three-phase output current of the grid side of the inverter, and comparing the mean value of the instantaneousfrequency residual value and the current period mean value with a set fault threshold value to judge a fault type and a kind. According to the technical scheme of the invention, a ''flying wing effect'' between data segments can be well overcome, and open-circuit fault diagnosis of a single power switching tube based on the three-phase output current can be realized.

Description

technical field [0001] The invention relates to the technical field of fault diagnosis, in particular to an instantaneous frequency-based NPC three-level inverter open-circuit fault diagnosis method. Background technique [0002] Since the NPC type three-level inverter has the advantages of large output capacity, high output voltage, and low current harmonic content, it is widely used in wind energy, solar energy and other new energy power generation fields. However, since the NPC three-level inverter uses more power switching devices and operates under high temperature, high current and high voltage for a long time, the failure rate of the power switching devices of the NPC three-level inverter is relatively high. , with low reliability. In order to ensure the safe and reliable operation of the NPC type three-level inverter, it is required to timely and accurately diagnose the faults of the power switching devices of the inverter, which will allow maintenance personnel to ...

AI Technical Summary

Problems solved by technology

[0005] 1. The current Park vector method and the average current Park vector method can detect and locate the open circuit fault of the power switch tube at the same time, but obviously, the fault diagnosis based on the Park vector trajectory must be realized by combining complex pattern recognition methods, which is not conducive to algorithm integration

[0006] 2. The current vector instantaneous frequency method can detect the open circuit fault of the power switch tube, but cannot identify the position of the faulty power switch tube

The point is that it is difficult to exhaust all fault phenomena and obtain a complete fault knowledge base, and some fault modes are very similar to a certain state of the power switch tube when it is working normally, making it difficult to accurately match faults

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