Fundamental wave and harmonic wave detecting method based on three-coefficient Nuttall windowed interpolation FFT

Abstract

The invention discloses a fundamental wave and harmonic wave detecting method based on three-coefficient Nuttall windowed interpolation FFT. The method comprises the following steps of: obtaining a sampling data of a detected signal by an analog-to-digital converter; carrying out a three-coefficient Nuttall windowed FFT calculation on the sampling data; searching for a largest spectral line and an adjacent second largest spectral line of an amplitude spectral line for the fundamental wave and each harmonic in an FFT spectral line, according to the amplitude ratio of adjacent spectral peaks and an explicit formulation, directly calculating interpolation coefficients of the fundamental wave and each harmonic; and finally, obtaining the frequency, the amplitude and the phase of the fundamental wave and each harmonic by the interpolation calculation. The invention provides the three-coefficient Nuttall windowed interpolation FFT fundamental wave and harmonic detecting method for directly calculating the interpolation coefficients based on the explicit formulation. The invention has advantages of providing the windowed interpolation FFT fundamental wave and harmonic wave detecting method thereof with small calculated amount and high analysis precision.

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 three-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 ...

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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 an explicit calculation formula, which is simple and clear, can be directly calculated, has a small amount of calculation, and has good calculation stability, but the analysis accuracy is low; Blackman-Harris window and four-term The number of items of the third-order Nuttall window function is more than that of the Hanning window, and the analysis accuracy is higher. 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 following may lead to the non-existence of an efficient solution to the equation

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