A fault identification method for single-end protection of DC power grid

Abstract

The invention relates to a fault identification method for single-end protection of a DC power grid: the instantaneous current of the line is collected in real time, and when the current change rate exceeds the protection start threshold g, it is judged that a fault occurs and the fault current is obtained; the fault current is determined according to the fault current Modulus component and linear mode component increment, determine the threshold scaling factor according to the current change rate K when the fault occurs: adaptively set the fault protection threshold in the zone according to the threshold scaling factor, and construct the phase plane of the fault current modulus amplitude; for For different fault types, obtain the phase plane locus of the fault current modulus amplitude, compare the fault current modulus with the preset protection threshold, and determine the fault occurrence area and fault pole according to the comparison result to realize protection. The present invention improves and perfects the problems of the prior art, such as limited ability to withstand transition resistance, difficulty in meeting the requirements of quick movement, and low detection sensitivity of terminal high-resistance faults, and improves the operation stability of the DC power grid.

Description

technical field [0001] The invention relates to the technical field of direct current power systems, in particular to the technical field of fault identification for single-end protection of direct current power grids. Background technique [0002] With the development of power electronics technology, flexible DC transmission based on modular multilevel converters has developed rapidly. Compared with traditional high-voltage DC transmission, flexible DC transmission has high power quality, low loss, and flexible and independent control of active and reactive power. , large transmission capacity, no commutation failure and other technical characteristics. Among them, the multi-terminal flexible DC transmission system can realize multi-power supply and multi-drop power receiving. Compared with the point-to-point DC transmission system, it can reduce line costs, improve power supply reliability, flexibility and system redundancy, and is the future power grid. inevitable trend ...

AI Technical Summary

Problems solved by technology

Slow protection action will cause all converter stations to be blocked or even power outage in the whole network, so DC power grid protection must quickly identify and eliminate faults

The DC line protection schemes that have been proposed so far are not yet mature. The single-ended protection method generally has the defects of difficult threshold value setting, limited ability to withstand transition resistance, and the protection range is not the full length of the line. The double-ended protection method is difficult to meet the requirements of protection quickness. , affecting the operational reliability of the flexible HVDC system

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