Harmonious wave detecting method in power system

Abstract

The invention discloses a harmonious wave detecting method in a power system. On the basis of five-layered db 40 wavelet packet transformation, hilbert transform is applied to perform frequency shift operation; every harmonic component is transferred to a side frequency band with relatively high precision, so as to perform wavelet packet decomposition and signal reconstruction, thus the high-precision detection of every harmonic wave is realized. The method includes steps of S01, moving every frequency classification of a former signal to 25-75 Hz frequency sections by hilbert transform; S02, respectively performing wavelet packet decomposition and reconstruction on every component after moving frequency; S03, respectively moving frequency of every restructured component and restoring to original frequency section; S04, acquiring the harmonious wave detecting result according to the recorded waveform data. The method provided by the invention eliminates the adverse influence of wavelet filter aliasing of the middle frequency section on the detecting precision, and has high-resolution time frequency analysis ability, and can effectively position the transient state disturbance; the detecting precision is high and the instantaneity is good; the method is applicable to various occasions of harmonious wave detection.

Description

technical field [0001] The invention belongs to the field of power system signal processing, and more specifically relates to a method for detecting harmonics in a power system. Background technique [0002] As the power grid system becomes more and more complex, the increasingly open distributed power grid-connected strategy and the use of diverse non-linear devices have brought a series of problems to the stability of the power grid. Harmonics are one of the typical power quality problems. The existence of harmonics may not only cause the devices connected to the power grid to fail to work normally, but also seriously affect the quality of electric energy, causing huge economic losses to power companies and society. The accurate detection of harmonics can not only reduce the error of electric energy measurement, but also provide accurate reference data for harmonic control, so as to study targeted control programs to deal with the problem of harmonic pollution in power sy...

AI Technical Summary

Problems solved by technology

[0004] Although the wavelet packet transform solves the time domain, frequency domain analysis and resolution problems in the high frequency band, the wavelet filter used in the wavelet packet transform almost always has aliasing phenomenon in the signal analysis, which leads to low accuracy and robustness. The current method of dealing with aliasing is mainly to improve the algorithm steps, sacrificing the simplicity and timeliness of the algorithm to obtain the required detection effect

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