MMC converter station running state fuzzy comprehensive evaluating method

Abstract

The invention relates to an MMC converter station running state fuzzy comprehensive evaluating method and belongs to the technical field of electric power transmission.According to the MMC converter station running state fuzzy comprehensive evaluating method, the method aims at carrying out statistic operation on direct-current bus voltage information with a Tsallis wavelet packet energy entropy algorithm, and taking the ratio of the Tsallis wavelet packet energy entropy peak value generated in a transient state fault to the Tsallis wavelet packet energy entropy peak value generated when the fault does not occur as an evaluating factor.The method comprises the steps that voltage signals of a direct-current bus are collected, wherein the sampling frequency is 1024 Hz; level decomposition is carried out on the voltage signals of the direct-current bus with a discrete wavelet packet, a signal matrix is restructured with the node coefficients of the discrete wavelet packet, and finally the energy entropy of the Tsallis entropy wavelet packet is obtained.The evaluating method can be proposed with the combination of reverse nonextensive entropy, healthy evaluation on the MMC running state can be achieved, and the study course of the energy transfer process of an MMC-HVDC alternating-current and direct-current parallel serial system is promoted.The influence severity degree of the MMC converter station by alternating-current line faults or disturbance is accurately reflected by analyzing changes of all electric information in the MMC converter station, and then the healthy evaluation on the MMC running state is achieved.

Description

technical field [0001] The invention belongs to the technical field of electric power transmission. Background technique [0002] In 2001, Rainer Marquardt of the Bundeswehr University in Munich, Germany proposed the concept of a modular multilevel converter (multilevelmodularconverter, MMC). In November 2010, the world's first flexible direct current transmission (MMC-HVDC) project based on modular multilevel converters - TransBayCable project was put into operation in San Francisco, USA. The MMC-HVDC system has many advantages such as power supply to islands, no commutation failure, low waveform level, strong fault handling capability, and small footprint. Engineering experiments show that when a transient fault occurs on the AC transmission line, it will have a corresponding impact on the operation of the MMC. If an evaluation method can be proposed, through the analysis of the changes in electrical information in the MMC converter station, it can accurately reflect the...

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Problems solved by technology

This then leads to differences in the energy distribution of the upper and lower bridge arms of each phase in the MMC converter station

However, due to the complexity of the transient mutation components of the electrical signals of each phase in the station, there are characteristics such as uncertainty and ambiguity, the traditional state evaluation method directly based on such signals cannot meet the evaluation accuracy requirements

[0005] At present, the evaluation based on the operation state of MMC still only uses the electrical information such as voltage and current inside the MMC converter station, and does not consider the electrical information on the DC bus. The evaluation results cannot fully describe the change law of the operation state in the MMC rectifier station

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