1,720,967 research outputs found
Feedback Couplings Evaluation on Synthetic Inertia Provision for Grid Frequency Support
Full text linkEmulation mechanisms of the physical synchronous generators obtained through convert-interfaced units are becoming extremely popular in literature. Still the impact of these strategies on networks frequency transients often does not take into account the effect of the converter DC-bus regulation, that plays a significant role in the dynamics definition. Thus two of the main synthetic inertia architectures are analysed both mathematically and experimentally in this article: differently from the available literature, the goal is not just to compare their macroscopic effects on network behaviour, but rather to identify the impact of the multiple internal control feedbacks on the inertia provision itself
Experimental validation of a novel angular estimator for synthetic inertia support under disturbed network conditions
Full text linkThis paper proposes a novel estimation scheme for angular quantities extraction under disturbed network conditions; a robust identification of the network angular frequency and of its derivative are crucial for the synthetic inertia provision from grid-connected converters. The newly proposed architecture is derived from the Second Order / Second Order Generalized Integrator scheme (SO-SOGI), an algorithm exploited to extract the fundamental harmonic component from phase voltages measurements, with the introduction of an additional decoupling feedback for negative sequence compensation. The effectiveness and robustness of the proposed technique are compared, both analytically and experimentally, with other schemes already available in literature
A stability-oriented design method for virtual impedance loop in droop-controlled converters
Full text linkIn this paper, a novel strategy for virtual impedance design in droop-connected converters is analysed; the method is based on the stability analysis of equivalent system loops and aims at defining feasible operating regions of the converter depending on the control parameters. The effect of the tuning on the regulating performances of the system then has been tested in a simulation environment
Modified droop control for the optimal management of the battery systems in isolated microgrids
Full text linkMicrogrids are often made up with Hybrid Power Plants (HPPs), which include storage batteries. To enhance system efficiency, it is important to manage the batteries so as to avoid that one gets charged at other batteries' expense. To reduce costs and increase robustness, a Microgrid Controller that communicates with all the HPPs can be avoided and the droop control is often adopted for the HPPs' interface inverters. This paper proposes a method to change the droop coefficients so as to get the described target with no communication available between the HPPs. Theoretical analysis is validated through a simulation carried out on a study case
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
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