A Fault Phase Selection Method Applicable to Doubly-fed Wind Farm Ties

Abstract

The invention discloses a fault phase selection method for a double-fed wind power plant tie line. The fault phase selection method comprises the following steps: (1) obtaining the voltage of each phase, the break variable of voltage of each phase, the break variable of voltage of each line and a zero sequence voltage at the position where a line protector is mounted; (2) obtaining a fault phase selection coefficient according to the proportion of the break variable of voltage of single voltage to the difference between two phases in the break variable of voltage; (3) judging whether a power grid has an earth fault or not according to the value of the zero sequence voltage and a rated voltage; (4) according to the proportion of the maximum value to the intermediate value of the fault phase selection coefficient, determining the type of the earth fault of the power grid; (5) according to the proportion of the minimum value to the intermediate value of the fault phase selection coefficient, determining the type of the interphase fault of the power grid; and (6) according to the maximum stable-state value of a three-phase voltage and the rated voltage, judging whether the power grid has a three-phase symmetry fault. Based on the characteristic that the break variable of voltage of a fault phase and the break variable of interphase voltage related to a fault have high sensitivity to the fault, the fault phase selection method can be used for accurately judging a fault type and a fault phase.

Description

Technical field [0001] The invention belongs to the technical field of power systems, and more specifically, relates to a fault phase selection method suitable for double-fed wind farm tie lines. Background technique [0002] Phase selection components are important components of high-voltage power system protection devices. In the traditional phase selection method, it is assumed that the positive and negative sequence impedances of the power grid are equal. However, with the access of wind turbines, the characteristics of the fault current fed into the grid have undergone great changes, making it difficult for the abrupt phase selection components in the wind power system to meet the phase selection requirements for the tie line protection of doubly-fed wind farms. The prior art has carried out various researches on the fault phase selection method of doubly-fed wind farm tie lines. For example, for the fault characteristics of doubly-fed wind turbines after crowbar action, th...

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Problems solved by technology

[0004] Aiming at the above defects or improvement needs of the prior art, the present invention provides a fault phase selection method suitable for doubly-fed wind farm tie-lines. The problem of incorrect phase selection when feeding the tie line of the wind farm

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