Equivalent harmonic impedance method for calculating single-point equivalent of power grid

Abstract

The invention relates to an equivalent harmonic impedance method for calculating the single-point equivalent of a power grid. The method comprises the steps of firstly, acquiring the bus voltage at a point of common coupling and the current of a current branch of a focused harmonic source, conducting the fourier transformation and decomposing the voltage and the current to obtain a harmonic voltage and a harmonic current; secondly, grouping every five pairs of the bus harmonic voltage at the point of common coupling and the harmonic current of the infusion bus of the focused harmonic source as one group to establish a complex domain partial linear model, and figuring out an equivalent harmonic impedance estimated value, an equivalent harmonic voltage estimated value and an estimated error thereof for each group; on the condition that the minimum value of the estimated errors of all groups is greater than a given error limit value, re-selecting data groups for calculation; otherwise, figuring out the mean value of equivalent harmonic impedance estimated values corresponding to the minimum value when the minimum value is smaller than or equal to the given error limit value, namely the equivalent harmonic impedance of the power grid in the single-point equivalent state. According to the technical scheme of the invention, the equivalent harmonic impedance of the power grid in the single-point equivalent state can be obtained accurately.

Description

Technical field: [0001] The invention relates to the field of electric energy quality, and more specifically relates to a method for calculating equivalent harmonic impedance at a single point equivalent of a power grid. Background technique: [0002] With the wide application of various high-precision power electronic devices in various industrial sectors and electrical equipment, power users' requirements for power quality are constantly increasing. However, the rapid development of my country's electrified railways, the application of large-capacity electric arc furnaces in metallurgical enterprises, and a large number of other types of nonlinear loads connected to the power grid have caused a large number of harmonics to be injected into the power grid, causing serious distortions in the voltage and current waveforms of the power grid. It poses a huge threat to the safe operation of the system and the normal work of user equipment. Harmonics reduce the efficiency of prod...

AI Technical Summary

Problems solved by technology

However, when the fluctuations of other harmonic sources are dominant, the dominant fluctuation method cannot obtain enough sample data, which will cause insufficient estimation information, and make the calculation results of system equivalent harmonic impedance and system equivalent harmonic voltage inaccurate

[0004] For the power grid, when the harmonic fluctuations of both concerned harmonic source users and non-concerned harmonic source users are large, or when the harmonic fluctuation of concerned harmonic source users is smaller than that of non-concerned harmonic source users, None of the existing methods can accurately calculate the equivalent harmonic impedance

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