A Comprehensive Criterion Type Boundary Protection Method and System for Multi-terminal DC Power Grid

Abstract

The invention relates to a comprehensive criterion type boundary protection method and system for a multi-terminal DC power grid. The method includes: obtaining the current at the installation place of the protection device of the calibration line in the multi-terminal DC power grid, performing multi-layer wavelet decomposition on the current to obtain multiple frequency bands; using historical data to obtain the local fault sensitivity and An indicator of external fault reliability, selecting the frequency bands of a calibrated quantity from a plurality of frequency bands according to the indicators as characteristic frequency bands, and assigning weights to the characteristic frequency bands; determining the reliability of the characteristic frequency bands, The weight is updated according to the reliability, and according to the updated weight, it is determined that an internal fault or an external fault occurs on the calibration line, and corresponding protection is performed on the calibration line. The technical scheme of the invention can take into account both reliability and sensitivity when performing boundary protection.

Description

technical field [0001] The invention relates to the technical field of power systems, in particular to a comprehensive criterion type boundary protection method and system for a multi-terminal DC power grid. Background technique [0002] The multi-terminal flexible DC transmission technology has gradually transformed the grid structure of power transmission from the traditional point-to-point type to the "strong AC and strong straight" type of strong grid with multiple power supplies and multiple drop-off points. However, what does not match this substantial upgrade at the topological level is that the fault isolation technology of the multi-terminal flexible DC grid itself is not yet mature. When a fault occurs on the DC line, the AC circuit breaker or the converter with improved topology is still used to limit the fault current and clear the fault, and these solutions are essentially just the direct use of the fault handling method of the point-to-point DC system. [0003...

AI Technical Summary

Problems solved by technology

However, once there is an external fault combined with noise, the above protection based on a single criterion is very easy to malfunction

In order to ensure the selectivity of the protection in the fault scenario outside the zone, its setting threshold must be greatly increased to strictly avoid noise interference. This will sacrifice the sensitivity of the protection in the fault scenario in the zone, resulting in some fault conditions with transition resistance. Protection cannot be selectively acted

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