Ship MMC-MVDC rapid fault protection method based on transient current characteristics

Abstract

The invention provides a ship MMC-MVDC rapid fault protection method based on transient current characteristics, and the method comprises the steps that ship MMC-MVDC fault characteristic analysis which comprises fault moment MMC fault current characteristic analysis and fault current characteristic analysis under a multi-region power distribution topological structure is performed; a sample database of fault current information is established; after a fault starting criterion is met, transient current information is sampled, sudden change point detection is carried out on the sampled currentinformation, and abnormal values are removed; the correlation degree of the sampling current information and the fault current information in the sample database is calculated by adopting an improvedcosine similarity algorithm so as to complete fault detection, and an approximate fault transition resistance range is speculated according to the fault current information with the maximum correlation degree in the sample database; according to the positivity and the negativity of the correlation degree of each line meeting the fault threshold, the fault instantaneous current direction is replaced to realize fault positioning. The ship MMC-MVDC fault detection method has the capability of resisting transition resistance, and can overcome the defects that the existing ship MMC-MVDC fault detection time is long, the detection algorithm is complex and the like.

Description

technical field [0001] The invention relates to the technical field of power systems, in particular to a ship MMC-MVDC fast fault protection method based on transient current characteristics. Background technique [0002] Medium-voltage DC distribution network (MVDC) has the advantages of high power generation efficiency, high power distribution efficiency, and high reliability. With the continuous development of power electronics technology and the increase in the capacity of ship power systems, MVDC distribution network has become the An important development direction of the power system. However, due to the lack of mature and effective fault protection means, the further development of ship MVDC is limited. At present, there is a lack of transient analysis and isolation scheme design for high-power ship medium-voltage DC distribution network, especially the lack of mature and effective fault protection methods, which limits the further development of ship MVDC. [0003...

AI Technical Summary

Problems solved by technology

For the VSC-HVDC DC transmission system with large capacitors connected in parallel on the DC side, the Pearson correlation coefficient is used to measure the difference between the transient current of the capacitor branch and the line entrance, so as to realize the identification of faults inside and outside the zone; however, since the capacitors in the MMC are scattered in In the sub-module, when a fault occurs on the DC side, the MMC sub-module is in a state of continuous switching, and the ship's MMC-MVDC cannot perform fault identification according to the above method

In the aspect of distribution network ranging, the feature matching technology of full waveform current is used to analyze the time-frequency matrix similarity of each branch sample database, so as to realize the location of fault branches; but this method is mainly used to solve the fault location of AC distribution network, and A large amount of data mining and analysis is required, which cannot meet the rapidity requirements of MMC-MVDC

In the existing marine MVDC protection technology, the method of analyzing transient high-frequency energy in the frequency domain can solve the problem of threshold selection in various operating states, but this method has high sampling requirements, and the excessive resolution of the frequency domain affects the calculation Accuracy, and longer processing time

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