| Presently, voltage fluctuation and flicker has been one of the main power reliability threats. In order to reduce the harm of voltage fluctuation and flicker, effective measurement is necessary for providing accurate parameters needed in evaluation and compensation. In this paper, measurements by wavelet transform, Hilbert transform, Prony spectral estimation are simulated and analyzed respectively, and an evaluating method based on Hilbert transform and Pisarenko harmonic decomposition is proposed to evaluate the modulating wave with single frequency in noise environment. The error of square demodulation is analyzed when it is used to measure multi-frequency modulated flicker, and a modified demodulation method by power-composition is proposed to make the band-pass filter output accurate modulation frequency. Research on flicker caused by inter-harmonics and the limitation of square demodulation on measurement of such inter-harmonics-induced flicker are made. In order to eliminate this limitation, a down-sampling method based on voltage signal of double fundamental frequency is proposed and simulation demonstrates its validity on measurement of flicker caused by inter-harmonics. |
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