Six-interpolation FFT (Fast Fourier Transform) algorithm based on four-item Nuttall cosine window

Abstract

The invention provides a six-interpolation FFT (Fast Fourier Transform) algorithm based on a four-item Nuttall cosine window. The method comprises the following steps: uniformly sampling a harmonic signal at a sampling frequency fc to obtain a discrete time signal x (n), adding four Nuttall cosine window truncation data to the discrete time signal x (n), and then performing FFT calculation to obtain a harmonic signal spectrum; analyzing the frequency spectrum of the harmonic signal, selecting about 3 spectral lines, namely 6 spectral lines, near a peak frequency point k0, establishing a spectral line correlation formula, and obtaining the amplitude, frequency and phase angle of each harmonic signal through the spectral line correlation formula. According to the invention, through the advantages of four Nuttall cosine windows and the amplitude information of different degrees contained in six spectral lines near a peak frequency point, errors caused by spectrum leakage and a fence effect existing in a conventional FFT algorithm during asynchronous sampling are reduced, so that higher-precision harmonic amplitude, frequency and initial phase angle detection is realized; the method effectively solves a problem that the detection precision is not high enough because the common interpolation at present does not completely utilize the information contained in each spectral line nearthe peak frequency point k0.

Description

technical field [0001] The present application relates to the technical field of power harmonic measurement and detection, in particular to a six-interpolation FFT algorithm based on four-term Nuttall cosine windows. Background technique [0002] In the power system, due to the use of a large number of power electronic components, the harmonic content in the power grid is increasing, which seriously affects the power quality. Such a situation threatens the safe operation of the power system. If the harmonic signal can be accurately detected and suppressed, the influence of the harmonic on the power system can be reduced. Since the discrete Fourier transform (DFT) was proposed, discrete spectrum analysis has realized the transformation of signal analysis and processing from time domain to frequency, and its fast algorithm (fast Fourier transform, FFT) uses it to calculate fast and convenient The advantages have become the basis of digital signal analysis and are widely used ...

AI Technical Summary

Problems solved by technology

[0005] This application provides a six-interpolation FFT algorithm based on the four-term Nuttall cosine window. Compared with the existing FFT algorithm, it balances the accuracy and calculation amount, reduces the risk of harmonic detection errors caused by frequency offset, and improves the The accuracy of harmonic detection effectively solves the current common interpolation of single spectral line interpolation, double spectral line interpolation, triple spectral line interpolation and four spectral line interpolation, all of which do not fully utilize the peak frequency point k 0 The information contained in the nearby spectral lines makes the detection accuracy not high enough

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