Single-end ultra-high-speed protection method for AC line at inversion side of AC-DC hybrid system

Abstract

The invention discloses a single-ended ultra-high-speed protection method for an AC line at an inversion side of an AC-DC hybrid system, and the method comprises the following steps: performing phase-mode conversion of the voltage and current of a local single end respectively to obtain two corresponding line moduli delta(ualpha), delta(ubeta) and delta(ialpha), delta(ibeta); calculating the mathematical morphological gradient of the current line modulus delta(ialpha) and delta(ibeta), solving the morphological gradient modulus maximum values of the line modulus, comparing the larger one witha starting threshold value, and if the larger one is greater than the starting threshold value, starting protection; distinguishing fault directions through employing time domain energy of line modulus reverse traveling waves, and discriminating internal faults and external faults in the area through employing the characteristic that characteristic frequency components and high-frequency components are remarkably attenuated by newly-added primary equipment of an inverter station, and starting the protection when the faults exist in the area. Only the voltage and the current of the local singleend are utilized, opposite end data are obtained without a communication channel, the rapidity and the reliability are superior to those of longitudinal protection, and an effective guarantee is provided for safe and stable operation of the AC-DC hybrid system.

Description

technical field [0001] The present disclosure relates to the technical field of relay protection for power systems, and in particular to a single-end ultra-high-speed protection method for an AC line on an inverter side of an AC / DC hybrid system. Background technique [0002] HVDC power transmission technology has advantages in collapsed grid interconnection and long-distance large-scale power transmission, and has been applied more and more in the world, and the AC-DC hybrid power system has been formed. However, with the increase of DC feed-in lines, the AC-DC hybrid power grid increasingly presents complex coupling characteristics, and the safe and stable operation of the power grid is seriously threatened. [0003] In 2013, the single-phase transient fault of the 500kV AC line in Shanghai area caused four circuits of Genan, Yihua, Lin Feng and Fufeng to fail to commutate at the same time when entering Shanghai DC. The measures will cause power fluctuations of about 4.5 ...

AI Technical Summary

Problems solved by technology

However, with the increase of DC feed-in lines, the AC-DC hybrid grid is increasingly showing complex coupling characteristics, and the safe and stable operation of the grid is seriously threatened.

[0003] In 2013, the single-phase transient fault of the 500kV AC line in Shanghai area caused four circuits of Genan, Yihua, Lin Feng and Fufeng to fail to commutate at the same time when entering Shanghai DC. This will cause about 4.5 million kilowatts of power fluctuations on the Central China-North China transmission section, leading to the disconnection of the North China and Central China power grids.

In 2015, the single-phase transient fault of 500kV AC line in Guangdong area caused the inverter side of 6 DC circuits in Tianguang, Gaozhao, Chusui, Niucongyi (the metal circuit of pole I was in operation, and Niuconga was out of service), and Jiangcheng The commutation fails, and the sum of the 6 DC power instantaneous drops exceeds 10,000MW. According to the simulation calculation and wave recording, if the fault removal time exceeds 0.38s, the system will experience power angle instability

For the AC line protection on the inverter side, the currently proposed protections based on fault traveling waves or transients are all longitudinal protections, which need to obtain peer data. Newly added primary equipment to improve protection performance

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