Fundamental wave and harmonic wave detection method based on four-item coefficient Nuttall window interpolation FFT

Abstract

The invention discloses a fundamental wave and harmonic wave detection method based on a four-item coefficient Nuttall window interpolation FFT, which comprises the steps of: obtaining sampling data of detected signals through an analog-to-digital converter; carrying out weighted four-item coefficient Nuttall window interpolation FFT operation on the sampling data; searching the maximum spectrum line and the larger spectrum line adjacent to the maximum spectrum line in an FFT spectrum line for a fundamental wave and harmonic waves, directly computing interpolation coefficients of the fundamental wave and the harmonic waves according to the amplitude ratio of every two adjacent spectrum peaks by an explicit expression; and finally, obtaining frequencies, amplitudes and phases of the fundamental wave and the harmonic waves through the interpolation operation. The invention firstly provides the fundamental wave and harmonic wave detection method based on the four-item coefficient Nuttallwindow interpolation FFT for directly computing the interpolation coefficients by using the explicit expression, and has the advantages of small computed amount and high analysis accuracy.

Description

technical field [0001] The invention relates to the field of fundamental wave and harmonic detection in signals, in particular to a fundamental wave and harmonic detection method based on four-term coefficient Nuttall window interpolation FFT. Background technique [0002] Taking power signal detection as an example, power system harmonics affect the normal operation of power equipment, and accurate detection of fundamental and harmonics is a basic requirement for the safe and stable operation of power grids and power equipment. Windowed interpolation FFT (Fast Fourier Transform) method is a common method for harmonic detection in power systems. In non-synchronous sampling, Fourier transform has spectral leakage and fence effect. The windowed interpolation FFT suppresses the spectrum leakage through the windowing operation, and eliminates the influence of the fence effect through the interpolation operation. Cosine window functions commonly used in windowed interpolation F...

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Problems solved by technology

[0004] The deficiencies of the prior art are that the windowing interpolation FFT method based on a window function with a small number of items has a small amount of calculation, and has an explicit calculation formula for interpolation coefficients, but the analysis accuracy is low; the windowing method based on a window function with a large number of items The interpolation FFT method has high analysis accuracy, but it needs to solve multiple equations, and the interpolation coefficient cannot be directly calculated through an explicit expression, and the calculation amount is large

For example, the Hanning window is a two-term coefficient cosine window, and its interpolation formula is explicit. The calculation formula is simple and clear, and can be directly calculated. The calculation amount is small and the calculation stability is good, but the analysis accuracy is low; The number of items of the first-order Nuttall window function is more than that of the Hanning window, and the analysis accuracy is high. However, when calculating the interpolation coefficient, it is necessary to solve multiple equations or polynomial fitting approximations, and it is impossible to directly calculate the interpolation coefficient. The amount of calculation is large. may result in no valid solution to the equation

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