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摘要
The noise mixed in the voltage sag signal will obscure the start and end time of the voltage sag in detection, and the interference of the voltage fluctuation will affect the determination of the of the voltage sag depth. This paper proposes a denoising method based on the variational mode decomposition (VMD), and designs a TDM(third derivative method)-Prony algorithm combined with wavelet transform. First, the signal is decomposed via VMD to obtain several band-limited intrinsic modal components(BLIMFs), and the acquired high-frequency BLIMFs are denoised by SURE threshold then reconstructed with the low-frequency components. Then, wavelet transform is performed on the reconstructed signal to locate the start and end time of voltage fluctuation and voltage sag, and TDM-prony algorithm is used to fit the fluctuation signal segment to obtain its information, so as to achieve the separation of fluctuation and sag. Finally, Hilbert transform is performed on the clean sag signal to obtain the amplitude and duration of voltage sag. Simulation results show that the designed algorithm can effectively extract the feature of voltage sag interfered by fluctuating signals.
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