Method for accurately calculating power harmonic wave parameters through adopting time delay Fourier transform frequency measurement method

Abstract

The invention provides a method for accurately calculating power harmonic wave parameters through adopting a time delay Fourier transform frequency measurement method, and belongs to a method for automatically monitoring an analytical instrument and an automatic monitoring device used for voltage and current waveform distortion of various power networks. The method includes the following steps: firstly, truncating sampled power harmonic wave signals through adopting a symmetrical window function; performing fast Fourier transform (FFT for short) for the truncated signals; truncating sampled power signals of the same length through adopting the same symmetrical window function at a time delay L point of the sampled power harmonic wave signals, and performing FFT for the truncated signals; accurately calculating out the fundamental wave and the frequency of each harmonic wave as per the phase difference of angle of the FFT performed for two times; calculating out the fundamental wave and the correction factor of each harmonic wave through adopting the method of interpolation in the frequency domain of the dissymmetrical window function; and finally, calculating out the amplitude value and the phase position of each power harmonic wave. The method provided by the invention has remarkable advantage with respect to the time spent in calculation as compared with other windowed FFT interpolation correction and analysis methods, best suits the DSP with hardware FFT, and is a practical algorithm.

Description

technical field [0001] The invention relates to an automatic monitoring method for an analysis instrument and an automatic monitoring device for various grid voltage and current waveform distortions, in particular to a time-delay Fourier transform frequency measurement method for accurately calculating power harmonic parameters. Background technique [0002] With the development of power electronics technology and devices, nonlinear loads are more and more widely used in power systems, and harmonic pollution in power systems is becoming more and more serious. Harmonics have become the main problem affecting power quality. The high-precision estimation of harmonic component parameters will be beneficial to the evaluation of power quality and the corresponding necessary control measures. [0003] Fast Fourier Transform (FFT) is the fastest tool for harmonic analysis. However, the premise of FFT to accurately analyze the frequency spectrum is to ensure the synchronous samp...

AI Technical Summary

Problems solved by technology

The actual power grid frequency usually fluctuates around the power frequency, thus causing asynchronous sampling and non-integer cycle truncation, which will cause spectrum leakage and inter-spectrum interference, which will cause errors in spectrum analysis

There are two solutions to the above problems: one technical solution is to use hardware or software phase-locked loop technology to solve the problem of synchronous sampling and integer cycle truncation; because the frequency of the power grid is not a constant value, and the response of the phase-locked loop takes time, it cannot be guaranteed Fully Synchronous Sampling

The use of window interpolation method can effectively improve the accuracy of harmonic estimation, but with the increase of the order of the interpolation correction curve fitting function and the increase of the number of harmonics contained, the accuracy of harmonic estimation is improved while the amount of calculation is greatly increased

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