Direct-current power distribution network fault line selection method, device and system based on direction traveling waves

Abstract

The invention discloses a direct-current power distribution network fault line selection method, device and system based on direction traveling waves. The method comprises the following steps: (1) extracting a voltage traveling wave signal and a current traveling wave signal; (2) acquiring voltage and current traveling wave line mode components; (3) when the micro-component continuous multiple points of the voltage or current traveling wave line mode component are greater than a starting criterion setting value, starting a fault protection action; (4) decomposing a voltage forward wave and a voltage reverse wave of each direct-current distribution line; (5) processing to obtain forward wave and reverse wave fault line selection criterion coefficients of each DC distribution line; and (6) multiplying the forward wave line selection criterion coefficient of a certain line by the forward wave line selection criterion coefficients of other lines in pairs, if the multiplying results are allnegative numbers, judging that the line has a fault, and cutting off the line. The differential component of the directional traveling wave is used as the protection criterion quantity, so that effective identification and accurate judgment of the faulty line can be realized, and the faulty line identification accuracy and the faulty line removal speed are improved.

Description

technical field [0001] The invention relates to a power grid protection method and protection device, in particular to a DC distribution network fault line selection method, device and system. Background technique [0002] With the widespread use of various distributed power sources such as wind power, photovoltaic power generation, and energy storage equipment, the AC distribution network is facing huge challenges. Compared with the AC distribution network, the DC distribution network has the advantage of being able to directly access distributed new energy, and has better performance in terms of transmission capacity, power supply quality, line loss, etc. Broad development prospects. However, the network topology of the DC power distribution system is complex, with many branches and various operating modes. After a fault occurs, the converters, distributed power sources, capacitors, and energy storage in the system will provide fault current to the short-circuit point, ca...

AI Technical Summary

Problems solved by technology

DC overcurrent protection relies on the large fault current generated when the line is faulty to constitute the protection criterion of the DC distribution network, and realizes the rapid removal of the fault. However, it is difficult to select the setting value of the overcurrent protection, and the high setting value cannot guarantee sensitivity. It is easy to cause damage to the DC equipment due to excessive fault current, and the low setting value can easily cause protection malfunction and affect the normal power supply of the system

Moreover, the DC overcurrent protection cannot perform accurate fault line selection, and generally needs to cooperate with other protections for fault location

The longitudinal differential protection relies on the current difference generated at both ends of the line when a fault occurs as the protection criterion for the DC distribution network. The longitudinal differential protection can accurately identify the fault section, but when a high-impedance fault occurs, due to the fault The current is too small, the protection cannot accurately identify such faults

Differential undervoltage protection mainly uses the rate of change of voltage to constitute the protection criterion of the DC distribution network system, but this protection method has low sensitivity and is easily affected by transition resistance, and cannot effectively identify the fault when a high-impedance ground fault occurs

[0004] To sum up, in the existing main protections of several DC distribution networks, the overcurrent protection cannot accurately realize fault line selection, while the longitudinal differential and differential undervoltage protections have low sensitivity and are easily affected by transition resistance.

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