Harmonic analysis method based on Kaiser window double-spectral-line interpolation FFT

Abstract

The invention discloses a harmonic analysis method based on the Kaiser window function double-spectral-line interpolation FFT. The method is suitable for analysis and monitoring on voltages, currents and harmonic waves of a power network. The method comprises the steps of firstly, using linear frequency modulation Z conversion for extracting fundamental wave signal parameters (amplitudes, frequencies and phase positions) from electric power signals containing the harmonic waves in a high-precision mode, then adding a Kaiser window function into the analyzed electric power signals to cut off the electric power signals, using the FFT for calculating frequency spectra of remaining signals, and precisely calculating parameters of the electric power harmonic waves according to interpolations of the Kaiser window function by the harmonic frequencies in a frequency domain. The method can effectively overcome fluctuations of fundamental frequencies, and influences of white noise on the harmonic analysis, under the non-integer cycle cut-off condition, the relative error of the frequency calculation of the 21-time harmonic signals is 1.4*10%, the relative error of the amplitude calculation is smaller than or equal to 0.002%, and the relative error of the initial phase position calculation is smaller than or equal to 0.0001%.

Description

technical field [0001] The invention relates to an analysis and automatic monitoring algorithm of grid voltage and current waveform distortion, which can be used for analysis instruments and automatic monitoring devices of various grid voltage and current waveform distortions. The utility model belongs to the technical field of electric power measurement and automation. Background technique [0002] With the wide application of various nonlinear loads, especially power electronic equipment in the power system, the harmonic pollution of the power grid is becoming more and more serious. FFT algorithm is the main algorithm of current harmonic analysis because of its simplicity and good practicability. [0003] The FFT algorithm needs to be under the condition of completely synchronous sampling, when the measurement time of the signal is not equal to the integer multiple of the signal period, or when the signal contains non-integer harmonics, the frequency of each harmonic obta...

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Problems solved by technology

The actual power grid frequency will always fluctuate around the rated frequency. Two methods are generally used to eliminate frequency synchronization errors: one is to implement synchronous sampling by hardware, and to add phase-locked synchronization technology to the acquisition system. The advantage is that the signal processing is relatively simple, but due to the phase-locked The ring response is slow, and the rapid change of the signal frequency cannot be tracked in time, so that the real synchronous sampling cannot be realized; another method is to select the spectral energy mainly concentrated in the main lobe, the side lobe spectral energy is small, and the amplitude attenuation block Window function to reduce inter-spectrum interference, that is, long-range leakage of spectrum; through interpolation correction between double-spectrum lines, the instrument reduces the fence effect, thereby improving the accuracy of harmonic estimation

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