Direct-current power distribution network protection method based on voltage characteristic traveling wave similarity measurement

Abstract

The invention discloses a direct-current power distribution network protection method based on voltage characteristic traveling wave similarity measurement. According to the method, the transient voltage currents at the two ends of a line after a direct-current fault occurs are subjected to high-frequency sampling, and are converted into line mode voltage forward traveling wave of one side of a protection area and line mode voltage inversion traveling wave of the opposite side; and based on traveling wave refraction reflection and polarity difference of intra-region and extra-region faults offorward inversion traveling wave at the two ends caused by mismatching of impedance of fault points, the similarity between the two waveforms is reflected by utilizing a globally optimal neighborhooddiffusion compatible dynamic matching similarity measure algorithm, so that the intra-region and extra-region faults can be reliably identified. According to the method, the traveling wave transmission delay and the time-to-time error can be compensated, influence from the sampling frequency deviation at the two ends, data missing and damage and the like is not caused easily, the fault tolerance is relatively high, the detection speed is high, and the power supply operation of the direct-current power distribution network is more reliable.

Description

technical field [0001] The invention belongs to the field of flexible DC distribution networks, and relates to a fast protection scheme capable of identifying internal and external faults of a DC distribution network, in particular to a protection method for a DC distribution network based on similarity measurement of voltage characteristic traveling waves. Background technique [0002] Using traditional two-level VSC or modular multilevel converter (MMC) to build a multi-terminal DC power distribution system can realize flexible adjustment and distribution of power, which is conducive to the effective consumption of distributed power, so it has attracted extensive attention from experts and scholars. . However, since related research is still in its infancy, there is no uniform standard for DC system topology, converter structure and control strategy, and system grounding methods, and DC fault characteristics are also affected by various factors. However, a large fault cur...

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Problems solved by technology

However, since related research is still in its infancy, there is no uniform standard for DC system topology, converter structure and control strategy, and system grounding methods, and DC fault characteristics are also affected by various factors.

However, a large fault current generated by a DC fault will endanger the safety of the converter equipment, and the improvement of the quick action protection requirements has increased the difficulty of the protection configuration of the DC power distribution system.

[0003] Single-ended quantity protection lacks selectivity for DC distribution networks with complex topological structures, and the setting and coordination are complicated; distance protection cannot protect the entire length of the line, and because the distribution network line is short, the calculation results are easily affected by measurement errors and transition resistance; Differential protection can meet selectivity requirements and have good performance under different fault current levels

However, due to the large current change rate di / dt of the fault between the poles of the DC system, high requirements are placed on the accurate timing of the measured current at both ends. While meeting the quick action, there may be misoperation due to faults outside the area, or due to MMC or large When a unipolar fault occurs in the DC system of the resistance converter, the fault current changes little, which affects the fault detection and then affects the reliable power supply of the distribution network

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