Research On Complex Harmonics/Interharmonics Analysis Using Atomic Decomposition And Windowed Frequency Shifting

Along with the increase of high-capacity loads’ impact and electricity grid connection of a large number of power electronic devices, the complexity of power system harmonic components increases. It which is harmful to the electricity grid. Comparing with the traditional harmonics, inter-harmonic frequency is uncertain, which can be any frequency between DC and higher harmonic. So the complex electrical signals of harmonics are likely to contain harmonic/inter-harmonic components with closing frequencies. Due to the main-lobe jamming exists among the signals with closing frequencies, the traditional harmonic analysis method can’t analyse it correctly. This paper makes a deep research on the complex electrical signals of harmonics/inter-harmonic.In this paper, the atomic decomposition algorithm and windowed frequency shifting algorithm are systematically introduced, and the advantages and disadvantages of each algorithm when they are used for harmonic/inter-harmonic analysis are pointed out. The former introduction of the two algorithms laid a good throretical basis for the algorithm proposition of this paper.In order to treat the complex electrical signals of harmonic/inter-harmonic components with closing frequencies, which prevailing in modern power systems, a new scheme using both the atomic decomposition and windowed frequency shifting algorithm is proposed in this paper. In the specific implementation of the algorithm, the main-lobe jamming criterion is constructed according to the main-lobe jamming method and the Hanning window is selected as the window function of this algorithm according to the characteristics of common cosine window function. The analyzed signal is windowed and imposed with Fast Fourier Transform and checking whether the main-lobe jamming exists in the Maximal Magnitude Component(MMC) according to the phase-frequency characteristics. If the main-lobe jamming does exist, atomic decomposition algorithm is used to search the best matching atom in neighborhood of the MMC frequency to obtain the exact parameters of predominant harmonics/inter-harmonics. If the main-lobe jamming does not exist, windowed frequency shifting algorithm is employed to adjust the MMC frequency to remove and get the correct parameters of harmonics/inter-harmonics. The proposed approach avoids the problem that the windowed frequency shifting algorithm can not solve harmonic/inter-harmonic signals with main-lobe jamming, and reduces the calculation of the atomic decomposition algorithm. The simulation results confirm its effectiveness and good noise resistance.