Photovoltaic power generation grid-connected tie line pilot protection method and system based on comprehensive impedance

Abstract

The invention discloses a photovoltaic power generation grid-connected tie line pilot protection method and system based on comprehensive impedance. The method comprises the steps of respectively extracting three-phase voltage sampling values and current sampling values at two sides of a photovoltaic power generation grid-connected tie line based on a pilot protection device after a starting element acts; respectively extracting a three-phase voltage power frequency phasor and a three-phase current power frequency phasor through a fast Fourier algorithm, and calculating a differential voltage phasor and a differential current phasor according to phases; based on the differential voltage phasor and the differential current phasor, calculating three-phase comprehensive impedance in the grid-connected tie line, and taking imaginary absolute values of the three-phase comprehensive impedance respectively; respectively comparing the imaginary absolute values of the three-phase comprehensive impedance with a protection setting threshold value; and executing a corresponding protection action based on a comparison result. According to the method, internal and external faults can be distinguished without being influenced by a photovoltaic inversion control strategy, and the method has relatively high anti-transition resistance capability and high reliability and sensitivity.

Description

technical field [0001] The invention belongs to the technical field of electric power system relay protection, and in particular relates to a method and system for longitudinal protection of grid-connected tie lines of photovoltaic power generation based on comprehensive impedance. Background technique [0002] With the development of renewable energy and the implementation of a sustainable energy development strategy, photovoltaics has become a hot spot in the development of new energy due to its unique advantages. At the same time, the access of photovoltaic systems has also brought many impacts on the protection of the current power grid. The random fluctuation of photovoltaic power output and the influence of control structure and control strategy in the process of grid-connected inverter make the fault characteristics of photovoltaic system more complicated. Changes in system fault characteristics after power is connected will cause protection performance to decline, or...

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Problems solved by technology

[0004] The purpose of the present invention is to provide a method and system for longitudinal protection of photovoltaic power generation grid-connected tie line based on comprehensive impedance, which solves the problem that the sensitivity of the existing line longitudinal current differential protection may decrease or even refuse to operate in the photovoltaic grid-connected tie line question

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