1,720,960 research outputs found
A passivity based, system reference frame approach for decentralized stability analysis and control design in future power grids
No full textOver the last decades, power systems have been through critical changes as a result of the
worldwide efforts to decelerate climate change and global warming. Such changes were
the introduction of new generation and storage technologies, and the rapid increase of the
share of Renewable Energy Sources (RES) in power generation. Although these advances
contributed to technological and economic development, they have introduced numerous
issues that were not previously encountered in traditional power grids. Specifically, the
gradual replacement of the large fossil-fueled plants with a large number of small sparselylocated
RES resulted in the significant decrease of system rotational inertia and the emergence
of serious stability-related problems.
Despite the latest decisive steps in the area of stability analysis and control design,
existing power systems are still in danger due to the continuously increasing challenges they
encounter. An effective way to overcome these problems is the adoption of more accurate
dynamical models for both the network and the power system components within stability
studies. Such accurate modeling will not only assist in the design of more effective control
mechanisms, but it will provide useful insights regarding the stability and the reliability of
the system.
The current thesis aims to address the above problems by introducing a novel approach
for decentralized stability analysis and control design in existing and future power grids
wherein more detailed dynamical models are employed. The proposed approach relies upon
the transformation of both the network and the bus dynamics into the system reference
frame instead of each bus local dq coordinates. In particular, this transformation allows the
formulation of the network equations as an input-output system which we show it is passive
even if the network’s lossy and dynamic nature is taken into account. The passivity property
of the adopted network model along with the local passivity conditions imposed on a broad
class of bus dynamics guarantee the asymptotic stability of the whole power network in a
completely decentralized manner. The use of such a general representation also facilitates
the incorporation of more accurate dynamical models for the power system components
and their control mechanisms, even though their inclusion in such a decentralized analysis
has been difficult. A further detailed discussion regarding the advantages of the presented approach for the reliable and robust operation of the future low-inertia power grids as well
as the design of more effective distributed control mechanisms is provided. The proposed
stability analysis framework is finally verified through realistic applications and simulations
on several testbed systems such as the Two Area Kundur, the IEEE 68 Bus test systems and
the IEEE 37 Node test feeder.Complete
A System Reference Frame Approach for Stability Analysis and Control of Power Grids
Get PDFDuring the last decades, significant advances have been made in the area of power system stability and control. Nevertheless, when this analysis is carried out by means of decentralized conditions in a general network, it has been based on conservative assumptions such as the adoption of lossless networks. In this paper, we present a novel approach for decentralized stability analysis and control of power grids through the transformation of both the network and the bus dynamics into the system reference frame. In particular, the aforementioned transformation allows us to formulate the network model as an inputoutput system that is shown to be passive even if the network's lossy nature is taken into account. We then introduce a broad class of bus dynamics that are viewed as multivariable input/output systems compatible with the network formulation, and appropriate passivity conditions are imposed on those that guarantee stability of the power network. We discuss the opportunities and advantages offered by this approach while explaining how this allows the inclusion of advanced models for both generation and power flows. Our analysis is verified through applications to the two area Kundur and the IEEE 68-bus test systems with both primary frequency and voltage regulation mechanisms included
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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