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Experimental assessment of the waveform distortion in grid-connected photovoltaic installations
No full textThis paper provides a multi-faceted view on the characterization of the waveform distortion in grid-connected photovoltaic (PV) plants from experimental results. The focus is set on the characterization of the waveform distortion occurring under different operating conditions in field measurements and laboratory tests. The assessment is carried out by considering the system-based point of view, on the basis of the measurements gathered at the interface between the PV plant and the grid or the supply point in the laboratory. New methodological hints on the formulation of the experimental tests are provided. The results of the waveform distortion analysis for harmonic currents and voltages are compared to the requirements of present power quality standards, indicating that in practical cases the current distortion can be significantly higher than in normal test conditions. Furthermore, the key aspect concerning harmonic and interharmonic modelling of multiple grid-connected PV inverters is addressed. Experimental results on plant configurations with multiple PV inverters show that low-order harmonics sum up almost arithmetically, whereas the higher-order harmonics and the interharmonics sum up in an almost Euclidean wa
Influence of harmonic system voltages on the harmonic current emission of photovoltaic inverters
No full textPerformance of grid-connected photovoltaic systems in fixed and sun-tracking configurations
No full textThis paper deals with the performance of grid- connected photovoltaic (PV) systems with parallel-connected converters. The focus of the paper is twofold. The first part concerns the assessment of the energy production and of the operational characteristics of multiple photovoltaic systems in Sun-tracking configurations, comparing their performance to the one of the corresponding fixed PV systems. The second part refers to assessing the harmonic characteristics of the integration of several converters in PV plants of various size. Different indicators are taken into account, including the individual and total harmonic distortion, the harmonic and interharmonic summation ratios at different harmonic orders, as well as the indicators formulated in the IEC Std. 61000-4-7 for group total harmonic distortion (THDG) and subgroup total harmonic distortion (THDS). Results from PV applications in Germany and Italy are shown and discussed
Characterisation and assessment of the harmonic emission of grid-connected photovoltaic systems
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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