Power system sub/super-synchronous harmonic detection method

Abstract

The invention discloses a power system sub / super-synchronous harmonic detection method comprising the following steps: extracting and separating power-frequency components; carrying out grouping according to modal aliasing conditions; extracting a grouping signal with the highest-frequency harmonic component, and judging whether modal aliasing occurs; if modal aliasing occurs, carrying out frequency shift modulation and empirical mode decomposition to get an intrinsic mode function corresponding to sub / super-synchronous harmonics contained in the group; carrying out amplitude phase and frequency compensation; carrying out Hilbert transform to get the instantaneous frequency and amplitude of the sub / super-synchronous harmonics contained in the group; separating the sub / super-synchronous harmonics contained in the group; and repeating the steps until the sub / super-synchronous harmonics contained in all the groups are separated. The advantages are as follows: based on a frequency shift method of signal modulation, the signal decomposition range of empirical mode decomposition is extended by increasing the frequency ratio of two sub / super-synchronous harmonic components; and the method is applicable to real-time accurate detection of sub / super-synchronous harmonics in a power system.

Description

technical field [0001] The invention relates to the technical field of power system dynamic monitoring and power quality, in particular to a sub / super synchronous harmonic detection method of a power system. Background technique [0002] In recent years, wind power, photovoltaic and other new renewable energy power generation has expanded rapidly, and its penetration rate has continued to increase. The problem of subsynchronous oscillation caused by the interaction between the wind turbine controller and the AC grid has become increasingly prominent, affecting the safe operation of the grid and equipment. , and even cause serious stability accidents or equipment damage, which is extremely harmful. [0003] Subsynchronous oscillations in the power grid are mainly manifested as continuous growth (divergence) or constant amplitude subsynchronous and / or supersynchronous current, voltage and power harmonics with large amplitudes. Accurately detect the amplitude of sub / supersynchr...

AI Technical Summary

Problems solved by technology

However, there are problems such as endpoint effect and modal aliasing in the application of the EMD method, especially when the frequency of the two components in the signal is within 2 times the frequency, EMD cannot decompose the two components, resulting in modal aliasing. Reduced frequency resolution

Since the frequency between the sub / supersynchronous harmonic and the fundamental or sub / supersynchronous harmonic is close to or within 2 times the frequency, this shortcoming restricts the application of HHT in sub / supersynchronous harmonic detection

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