1,720,956 research outputs found
Planning studies for active distribution grids in presence of EVs charging stations: simulation on a real test network
No full textIn the next future, a large spread of Electrical Vehicles (EVs) is foreseen, in accordance with the
European policies and regulation dealing with environmental sustainability. It will lead to an important
number of charging stations connections, whose number will be a function of the demand required by
the EVs (traffic conditions, EV fleet and features, etc.), but they depend also on grid capacity,
considering that they typically represent very variable loads for the grid. A “fit and forget” approach
could involve the violation of grid operation limits and so the need of grid reinforcements (new MV
and LV lines construction, primary and secondary substations expansion or new construction), thus
causing relevant investments on the distribution grids. An intelligent management approach for EV
charging stations could ensure the respect of the operation limits of the grids in the actual asset. The
same approach should take into account the presence of DG and coordinate the RES energy
production with the new EV charging stations consumption, solving technical problems such as the
reverse power flow. In this way it should be possible to defer or avoid network reinforcements and
development.
The paper shows some results of a wide planning study performed on a real active distribution grid,
including EVs charging stations connected to MV grid (public stations) and LV grid (home stations) in
different EVs spread scenarios, according to European addresses, Italian policies, Enel guidelines and
making a study of the territory where the distribution grid is located. Simulations have been carried
out on the MV and LV grids connected to a HV/MV transformer. The complete analysis has been
based on Power Flow (PF) and Optimal Power Flow (OPF) calculations performed using a MatLab
tool. PF analysis gave the possibility to know the hosting capacity of the distribution grid for EV
charging stations, pointing out if grid reinforcements are required. OPF analysis allowed evaluating
the impact of a smart management approach, taking full advantage of the actual hosting capacity of the
grid, suitably dispatching the EV charging stations. Many objective functions have been tested with
the MatLab tool. Some of the results are reported in the paper for showing the benefits of the smart
management approach in terms of grid reinforcements avoided
EV charging stations and RES-based DG: A centralized approach for smart integration in active distribution grids
Full text linkRenewable Energy Sources based (RES-based) Dispersed Generation (DG) and Electrical Vehicles (EVs) charging systems diffusion is in progress in many Countries around the word. They have huge effects on the distribution grids planning and operation, particularly on MV and LV distribution grids. Many studies on their impact on the power systems are ongoing, proposing different approaches of managing. The present work deals with a real application case of integration of EVs charging stations with ES-based DG. The final task of the integration is to be able to assure the maximum utilization of the distribution grid to which both are connected, without any upgrading action, and in accordance with Distribution System Operators (DSOs) needs. The application of the proposed approach is related to an existent distribution system, owned by edistribuzione, the leading DSO in Italy. Diverse types of EVs supplying stations, with diverse diffusion scenarios, have been assumed for the case study; various Optimal Power Flow (OPF) models, based on diverse objective functions, reflecting DSO necessities, have been applied and tried. The obtained results demonstrate that a centralized management approach by the DSO, could assure the respect of operation limits of the system in the actual asset, delaying or avoiding upgrading engagements and charges
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
EVs charging stations in active distribution grids: A real case-study of smart integration
No full textIn Italy a large amount of Dispersed Generation (DG), mainly based on Renewable Energy Source (RES), has been connected in the last years to the distribution grids in Medium Voltage (MV) and Low Voltage (LV) grids of Enel Distribuzione, the main Distribution System Operator (DSO) in Italy, changing the electrical system from passive to active. The diffusion of Electrical Vehicles (EVs) is foreseen for the next future, in accordance with the European policies regarding environmental sustainability, resulting in another important change for the distribution grids: EVs charging stations will be realized as new connections with their very variable load towards the grid, in function of the demand required by the EVs. New planning and operation criteria are thus required for the electrical grid. This paper describes results of a wide planning study performed on a real active distribution grid of Enel Distribuzione, including different types of charging stations (public and home stations) in different EVs spread scenarios. The study shows how a smart management approach for EVs charging stations, recently proposed in many scientific papers, dispatching them taking into account DG and coordinating them with RES energy production, could ensure the respect of the operation limits of the grids in the actual asset, so deferring or avoiding network reinforcements
Active distribution grids and EV charging stations: a centralized approach for their integration
No full textThe paper proposes real case of application of a smart integration of Electrical Vehicles (EVs) charging stations with Dispersed Generation (DG) that can guarantee the maximum exploitation of the system and its sustainability. The case study is a real distribution grid of e-distribuzione, the main Italian Distribution System Operator (DSO). Different kinds of EVs charging systems and spread scenarios are hypothesized and different Optimal Power Flow (OPF) models, with different objective function, reflecting different needs of DSO, have been implemented and tested. The analysis points out how a centralized management approach of EVs fast charging systems, by the DSO, might guarantee no violation of grid operation limits in the current configuration, postponing or escaping network upgrading actions and costs
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