Composite open-circuit fault diagnosis method for NPC three-level inverter

Abstract

The invention discloses a composite open-circuit fault diagnosis method for an NPC three-level inverter, and belongs to the technical field of fault diagnosis. The method comprises the following steps of establishing a hybrid logic dynamic model, establishing a novel adaptive sliding mode observer, giving a primary adaptive threshold value, carrying out primary fault diagnosis, giving a secondary adaptive threshold value and carrying out secondary fault diagnosis. Compared with a traditional sliding-mode observer, the novel self-adaptive sliding-mode observer has the advantages that the sliding-mode surface approaching time is shortened, and buffeting of sliding-mode motion is reduced; according to the method, the accuracy and robustness of fault diagnosis are improved by adopting a self-adaptive threshold value; according to the method, a three-phase output current estimation value and a relation between a three-phase output current residual error and an adaptive threshold value are compared to define a fault detection characteristic quantity and a fault positioning characteristic quantity to carry out fault diagnosis on the NPC three-level inverter, and multi-switch tube fault diagnosis continues to be carried out after the first fault diagnosis.

Description

technical field [0001] The invention relates to the technical field of fault diagnosis, in particular to a compound open-circuit fault diagnosis method for an NPC three-level inverter. Background technique [0002] In the photovoltaic power generation system, the inverter plays an important role. NPC three-level inverters have many advantages such as low loss, low harmonic content of output voltage and current waveforms, small device stress, and large output capacity, and are widely used in photovoltaic microgrids. Although the NPC three-level inverter has many of the above advantages, due to the complex and changeable environment of the photovoltaic power generation system, the power devices in the inverter are prone to failure, which seriously threatens the safety of the photovoltaic power generation system, and the NPC three-level inverter The complex structure of the inverter, with too many power electronic devices, leads to an increase in the failure rate during operat...

AI Technical Summary

Problems solved by technology

The main idea of ​​this type of method is to establish a mathematical model of the inverter, compare the estimated system output with the measurement information to obtain the residual, and analyze the residual to realize the fault diagnosis of the converter. Related patent documents such as "A Model-Based Parametric Fault Diagnosis Method for Multi-Level Inverter" (Application Publication No. CN108649600A), etc., such methods have the problems of high mathematical model requirements and poor robustness

[0008] In summary, the existing technology has problems such as high signal processing complexity, long diagnostic cycle, large amount of calculation, difficulty in establishing and maintaining the knowledge base, high requirements for mathematical models, and poor robustness.

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