1,720,975 research outputs found
Wavelet-based decompositions in probabilistic load forecasting
No full textProbabilistic load forecasting is gaining growing interest by researchers and practitioners. Multi-stage forecasting systems have recently demonstrated their effectiveness in increasing the overall performances. In this paper, we address the effect of pre-processing load time series using wavelet-based decompositions, before using quantile regression forests and random forests to build probabilistic forecasts. Four wavelet-based decompositions are specifically used for this task. Forecasts for the load components resulting from these transformations are obtained through distinct models, in order to increase the accuracy and to reduce the computational effort. Numerical applications based on the actual data published during the 2014 Global Energy Forecasting Competition are presented to evaluate the performance in a comparison with several benchmarks
Impact on railway infrastructure of wayside energy storage systems for regenerative braking management: a case study on a real Italian railway infrastructure
No full textDFT-parametric methods for an accurate and fast assessment of waveform distortions caused by adjustable speed drives
No full textThe increasing application of adjustable speed drives dictates that the effect of waveform distortions on other equipment in industrial systems must be seriously considered. In this paper, we proposed new, advanced methods for the accurate and fast estimation of waveform distortions caused on the supply-side currents by an adjustable-speed drive. The methods consist of a four-step procedure based on proper combinations of Prony, ESPRIT, and DFT methods as well as analytical formulas. The methods properly combine the accuracy of the parametric methods (ESPRIT or Prony) with the speed of both the DFT method and analytical formulas. Experiments and comparisons were made based on both synthetic and measurement data. The results showed that the proposed methods were effective and efficient
New Power Quality Indices for the Assessment of Waveform Distortions from 0 to 150 kHz in Power Systems with Renewable Generation and Modern Non-Linear Loads
No full textThe widespread use of power electronics converters, e.g., to interface renewable generation systems with the grid or to supply some high-efficiency loads, has caused increased levels of waveform distortions in the modern distribution system. Voltage and current waveforms include spectral components from 0 kHz to 150 kHz, characterized by a non-uniform time-frequency behavior. This wide interval of frequencies is currently divided into “low-frequency” (from 0 kHz to 2 kHz) and “high-frequency” (from 2 kHz to 150 kHz). While the low-frequencies have been exhaustively investigated in the relevant literature and are covered by adequate standardization, studies for the high-frequencies have been addressed only in the last decade to fill current regulatory gaps. In this paper, new power quality (PQ) indices for the assessment of waveform distortions from 0 kHz to 150 kHz are proposed. Specifically, some currently available indices have been properly modified in order to extend their application also to wide-spectrum waveforms. In the particular case of waveform distortions due to renewable generation, numerical applications prove that the proposed indices are useful tools for the characterization of problems (e.g., overheating, equipment malfunctioning, losses due to skin effects, hysteresis losses or eddy current losses) in cases of both low-frequency and high-frequency distortions
On the comparison between ensemble Kalman filter and Kalman filter for the dynamic harmonic state estimation in a hybrid microgrid
No full textNew ESPRIT-based method for an efficient assessment of waveform distortions in power systems
No full textDay-ahead Optimal Scheduling of Loads and Dispatchable Resources in a Hybrid AC/DC Microgrid of an Industrial System
No full textIndustrial systems are usually characterized by high energy consumption and presence of sensitive loads which require high levels of Power Quality. Based on the grid architecture of an actual Italian industrial facility, this paper proposes the installation of a hybrid AC/DC microgrid. The hybrid microgrid includes dispatchable and non-dispatchable renewable generation units, battery storage systems and controllable loads. An optimization model is formulated to solve the problem of the day-ahead optimal scheduling of the microgrid. The model aims to optimize the operation of dispatchable resources, controllable loads and storage systems minimizing the daily costs of the energy imported from the AC grid and the costs required by the dispatchable generators while satisfying operational constraints such as those related to the production process of the industry facility. Different case studies are investigated in order to show the feasibility and effectiveness of the proposed procedure. © 2015, European Association for the Development of Renewable Energy, Environment and Power Quality (EA4EPQ). All rights reserved
On the comparison between ensemble Kalman filter and Kalman filter for the dynamic harmonic state estimation in a hybrid microgrid
No full textThe management of micro grids requires the dynamic harmonic state estimation of the system in order to perform control strategies that optimize waveform distortions. In industrial context, AC and DC devices and sources coexist and, therefore, micro grids can be a hybrid combination of AC and DC power sections. Also for such hybrid AC/DC micro grids optimal control strategies that optimize waveform distortions are mandatory. In this paper, the comparison of two different methods for the dynamic harmonic state estimation of hybrid AC/DC micro grids is performed analyzing both theoretical and numerical aspects. In particular, the Kalman Filter- and Ensemble Kalman Filter-based dynamic harmonic state estimations are compared in terms of accuracy and computational efforts. The numerical applications were performed on a hybrid AC/DC μG proposed for an actual industrial facility in southern Italy
A Wavelet-Modified ESPRIT Hybrid Method for Assessment of Spectral Components from 0 to 150 kHz
No full textWaveform distortions are an important issue in distribution systems. In particular, the assessment of very wide spectra, that include also components in the 2–150 kHz range, has recently become an issue of great interest. This is due to the increasing presence of high-spectral emission devices like end-user devices and distributed generation systems. This study proposed a new sliding-window wavelet-modified estimation of signal parameters by rotational invariance technique (ESPRIT) method, particularly suitable for the spectral analysis of waveforms that have very wide spectra. The method is very accurate and requires reduced computational effort. It can be applied successfully to detect spectral components in the range of 0–150 kHz introduced both by distributed power plants, such as wind and photovoltaic generation systems, and by end-user equipment connected to grids through static converters, such as fluorescent lamps
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