Fault diagnosis method after fault protection of two-level flexible HVDC converter

Abstract

The invention discloses a fault diagnosis method after fault protection of a double-level VSC-HVDC converter. The method comprises the following steps of 1) collecting fault signals; 2) preprocessing the fault signals; 3) calculating characteristic parameters of faults; and 4) diagnosing the converter faults in a hierarchical method via a converter fault diagnosis module. The method is simple in steps, convenient to realize, popularize and use, lower in cost, high in calculation speed, high identification rate of fault diagnosis, high in practicality, and good using effects.

Description

technical field [0001] The invention belongs to the technical field of flexible direct current transmission systems, and in particular relates to a fault diagnosis method after fault protection of a two-level flexible direct current transmission converter. Background technique [0002] Flexible direct current transmission system (VSC-HVDC) is a new type of direct current transmission technology developed in response to the requirements of green power grids and new energy power generation. It has been widely used in many fields such as wind power generation, island power transmission, and ocean power generation. As the core of the VSC-HVDC system, the voltage source converter (VSC) realizes the conversion of alternating current and direct current, but its overvoltage and overcurrent capability is poor, and it is prone to faults and difficult to maintain. Therefore, the internal faults of the voltage source converter are studied. It is very important to formulate a fault prote...

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Problems solved by technology

[0004] At present, there are few results about the fault diagnosis of VSC-HVDC converters. For example, the Chinese patent application number 201310132795.7 discloses a sub-module fault diagnosis method of a modular multi-level converter, which is aimed at the sub-module IGBT of the sub-module Short circuit, IGBT open circuit, FWD short circuit and other faults were analyzed, and the submodule fault diagnosis was carried out by using the capacitor voltage, bridge arm current and the trigger signal at this time as the fault diagnosis signal; the authors Li Zhixiong and Yan Xinping published the paper "Independent Component Application of Analysis and Manifold Learning in Fault Diagnosis of VSC-HVDC System", and the research on "Simulation Analysis and Diagnosis Method of Converter Fault in VSC-HVDC System" published by the authors Sun Xiaoyun, Tong Xiangqian and Yin Jun in 2012 Based on the VSC-HVDC fault operating characteristics of the two-level voltage source converter, the fault diagnosis method of the converter is designed by combining the ideas of signal processing and pattern recognition; however, the existing technology based on the two-level voltage source converter The VSC-HVDC fault diagnosis method needs to extract a long-term diagnostic signal. If the voltage source converter has a serious through-fault such as AC single-phase grounding, a serious overcurrent phenomenon will occur at the moment of the fault, and the protection strategy needs to be activated in a short time. voltage source converter, and the proposed diagnostic method encounters difficulties in extracting fault diagnosis signals, and its fault diagnosis method is difficult to apply to the actual system

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