1,720,984 research outputs found
Analisi di sensitività per circuiti trifasi di elettronica di potenza con la tecnica della rete aggiunta
No full textAn Alternative Approach to Parallel A/D Conversion
No full textA functional diagram of a novel type of A/D converter, described as bit oriented, for high-speed application is discussed. Although the system can be regarded as the natural development of the well-known flash ADC, a different approach to the conversion process has led to a reduction in the number of comparators required, with no loss in flash performances. There is also no need for sample and hold (S/H) and digital circuits for the coding. A comparison with the most up-to-date high conversion techniques (subranging, folding and interpolation) points out the advantages of the techniqu
A New Method For Efficient Time-Domain Simulation Of Power Electronic Circuits
No full textIn this paper a method for fast time-domain simulation of power electronic circuit with switches is described. The method is based on transient windows analysis joined by DC analysis on reduced circuits at the switching instants. It shows that the proposed approach provides the same results of standard analysis methods with a consistent reduction of the iterations required
Analisi di piccolo segnale per convertitori PWM ac/dc e dc/ac con la tecnica del frequency-shift
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Technical image reduction using N.N. and Wavelet
No full textA general-purpose procedure for scaling technical line drawings, suitable for video presentation, is described in this paper. The proposed method is based on the separate processing of scaleable (layout) and non-scaleable (symbol) elements, drawn from standard technical drafting. Symbols, detected by a cluster-based template procedure and a Minimum Distance Classifier, are extracted from drawings and utilized to form a symbols position table. To obtain the clusters of symbols, a Rival Penalized Competitive Learning neural network and a human template labeling procedure have been adopted. The extraction of symbols from drawings produces clear layouts. These layouts are scaled down by wavelet based algorithm and the symbols are then restored or replaced, through the symbols position table, with different graphs or textual representations, according to the scaling factors and the display device. The results of an experimental study on a large database of technical drawing are presented and the accuracy of the system is discussed
A feature extraction unsupervised neural network for an environmental data set
No full textEnvironmental data sets are characterized by a huge amount of heterogeneous data from external fields. As the number of measured points grows, a strategy is needed to select and efficiently analyze the useful information from the whole data set. One efficient way of obtaining the validation-compression of data sets is the adoption of a restricted set of features that describe, with an assigned accuracy a subset of the whole data set. One characteristic feature of the environmental data is time dependency: in the medium and long term they are not stationary data sets. The aim of this work is to propose a feature extraction technique based on a new model of an unsupervised neural network suitable to analyze this kind of data. The paper reports the results obtained utilizing the above extraction and analysis procedure on a real data set on chemical pollutants. It is shown that the proposed neural network is able to identify correctly human and/or meteorological effects in the environmental data set
Sensitivity analysis of an LCL-filter-based three-phase active rectifier via a "virtual circuit" approach
No full textThree-phase active rectifiers based on the voltage source converter topology can successfully replace traditional thyristor-based rectifiers or diode bridge plus chopper in interfacing dc-systems to the grid. However, if the application in which they are employed has a high safety issue or if there are other loads connected to the same Point of Common Coupling (PCC), and sensitive to the harmonics produced by the switching of the converter, an LCL-filter has to be used. This kind of solution has been studied in theory but its sensitivity to the value of the LCL-filter passive elements employed, to the grid side stiffness and to the parameters of the controller has never been considered in detail. In. this paper the experimental results of an LCL-filter-based three-phase active rectifier are analyzed with the circuit theory approach. A "virtual circuit" is synthesized in role of the digital controller and of the feedback filters to have an homogenous model that allows a sensitivity analysis which is rigorous and straightforward for the industry
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