Abstract
The broad diffusion of renewable energy-based technologies has introduced several open issues in the design and operation of smart grids (SGs) when distributed generators (DGs) inject a large amount of power into the grid. In this paper, a theoretical investigation on active and reactive power data is performed for one active line characterized by several photovoltaic (PV) plants with a great amount of injectable power and two passive lines, one of them having a small peak power PV plant and the other one having no PV power. The frequencies calculated via the empirical mode decomposition (EMD) method based on the Hilbert-Huang transform (HHT) are compared to the ones obtained via the fast Fourier transform (FFT) and the wavelet transform (WT), showing a wider spectrum of significant modes mainly due to the non-periodical behavior of the power signals. The results obtained according to the HHT-EMD analysis are corroborated by the calculation of three new indices that are computed starting from the electrical signal itself and not from the Hilbert spectrum. These indices give the quantitative deviation from the periodicity and the coherence degree of the power signals, which typically deviate from the stationary regime and have a nonlinear behavior in terms of amplitude and phase. This information allows to extract intrinsic features of power lines belonging to SGs and this is useful for their optimal operation and planning.
Highlights
The massive use of non-linear loads and electronic-based equipment in residential and industrial plants greatly affects the operation and management of distribution lines
It has been found that the Hilbert-Huang transform (HHT)-empirical mode decomposition (EMD) analysis takes into account of non-periodical and non-linear features of an electrical signal and it allows a wider spectrum of modes to be found and non-linear features of an electrical signal and it allows a wider spectrum of modes to be found that that could not be extracted by limiting the investigation to the fast Fourier transform (FFT) and wavelet transform (WT) techniques
It has been shown that the HHT-EMD analysis applied to three different power lines belonging to an smart grids (SGs) allows the extraction of several features that were not found according to the FFT and WT investigations, and the quantitative differences between the results obtained by
Summary
The massive use of non-linear loads and electronic-based equipment in residential and industrial plants greatly affects the operation and management of distribution lines. The EMD and its variants were used as tools to study the main features of several kinds of signals including electrical ones [27,28,29,30,31,32] In this respect, the HHT-EMD analysis presents several advantages with respect to the FFT one that is able to give a correct quantitative description only for linear, stationary and periodic systems. The paper is organized as follows: Section 2 recalls the formulation of the EMD tool based on the HHT and introduces the proposed indices useful to characterize quantitatively the electrical signal.
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