Wave correlation based current protection method for power collecting lines in wind farm

Abstract

The invention relates to a wave correlation based current protection method for power collecting lines in a wind farm. The method comprises the following steps: firstly, three-phase current in protective mounting position of each power collecting line in the wind farm is collected; filtering is performed, and fault component current of each phase is extracted by programming; correlation coefficients of the phases between the power collecting lines is calculated according to the fault component current, and the correlation coefficients are traversed pairwise; if the correlation coefficient of one phase belongs to (0, 1], the phase of the two power collecting lines has no fault, and the two power collecting lines are written as line i and line j; if the correlation coefficient of the one phase does not belong to (0,1], the phase of one and only one of the two power collecting lines has a fault, and the two power collecting lines are written as line u and line v; at the moment, when the correlation coefficient of the phase between the line u and the line j belongs to (0,1], the phase of the power collecting line u has no fault, while the phase of the power collecting line v has a fault; when the correlation coefficient of the phase between the line u and the line j does not belong to (0,1], the phase of the power collecting line u has a fault, while the phase of the power collecting line v has no fault.

Description

technical field [0001] The invention belongs to the technical field of electric power system relay protection, and in particular relates to a current protection method of a wind farm collector line based on waveform correlation. Background technique [0002] my country's wind power development has a unique development model, most of which are large-scale centralized development and long-distance delivery. The impact of wind power on the power grid due to this development model cannot be ignored. With the continuous increase of wind power installed capacity, the problems caused by wind power grid integration have become more and more prominent. In recent years, there have been many large-scale wind power chain off-grid accidents in Jiuquan and other wind power bases in Gansu Province, resulting in a large loss of power grid output and affecting the safe and stable operation of the power system. Accident investigations show that large-scale wind farm cascading off-grid accide...

AI Technical Summary

Problems solved by technology

[0004] (1) Multiple DFIGs are scattered and connected to one collector line, and each DFIG is only equipped with fuse protection on the high-voltage side, which makes it very difficult to cooperate with the protection of the collector line and the fuse protection of the box-type transformer. When the high-voltage side of the box-type transformer fails, The overcurrent stage I protection of the collector line will trip over the level

[0005] (2) When a collector line fails, the low wear current provided by the wind turbine on the non-faulty collector line may be greater than the load current, resulting in the malfunction of the overcurrent II section of the non-directional element

There are great differences between wind turbines and conventional power sources, especially for double-fed wind turbines that combine asynchronous generators and power electronic devices, and their fault characteristics are very complicated

During the fault period, the equivalent positive and negative sequence impedance of the wind power supply is controlled by the fault transient strategy of the wind turbine, and the impedance phase angle may change greatly, which may lead to insufficient sensitivity or misjudgment of the fault component direction element

Therefore, problem (2) has not been substantially solved

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