Voltage sag frequency evaluation method and device

Abstract

The invention provides a voltage sag frequency evaluation method and device. The method comprises the following steps: after a short circuit fault occurs in a power grid system, determining the self-impedance and mutual impedance of a fault point in a first stage, and calculating a voltage sag amplitude of a target bus in the first stage according to the self-impedance and mutual impedance of thefirst stage; determining the self-impedance and mutual impedance of the fault point in a second stage, and calculating the voltage sag amplitude of the target bus in the second stage according to theself-impedance and mutual impedance of the second stage; determining voltage sag duration of the target bus; and calculating the sag frequency of the target bus according to the voltage sag amplitudeand the voltage sag duration of the target bus at the first stage, wherein the first stage and the second stage are respectively two stages before and after a main protection action on the first sideof a line where the fault point is located. The voltage sag frequency evaluation method and device in the present invention provide a theoretical evaluation basis for the occurrence of multi-level voltage sag.

Description

technical field [0001] The invention relates to the technical field of power system control, in particular to a voltage sag frequency evaluation method and device. Background technique [0002] With the development of new industries and the improvement of industrial automation, more new power electronic devices have been put into use. Sensitive equipment is extremely sensitive to voltage sags, and a single voltage sag event will bring great losses to users. Therefore, it is of great significance to analyze the short-circuit fault of the power system and accurately evaluate the frequency of voltage sags. [0003] There are two main types of evaluation methods for the frequency of voltage sags: measured statistical methods and random evaluation methods. The measured statistics method uses measurements to statistically determine the characteristics and frequency of sags. The time and economic cost of the actual measurement method is high, and the evaluation results are diffi...

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Problems solved by technology

[0004] In the current random evaluation method, the traditional voltage sag evaluation method only studies the voltage transient under normal conditions such as the protection action at both ends after the line fault, and ignores the voltage under special circumstances such as the main protection action at only one end of the line fault However, there is no mature method in the prior art to evaluate the characteristics and frequency of voltage fluctuations in this special case

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