1,720,958 research outputs found
Control architectures and algorithms design for the aggregation of flexible loads for network services provisioning
Full text linkIl sistema dell’energia elettrica europeo nelle ultime due decadi è stato ed è protagonista di una profonda trasformazione. La sempre più elevata presenza di Risorse Energetiche Distribuite (DERs) - sparse oramai ad ogni livello della rete elettrica - insieme alla repentina crescita e diffusione dell’elettromobilità richiedono una revisione che arriva fino alle fondamenta del sistema elettrico. La profonda trasformazione del sistema elettrico ha riscosso l’interesse dalla comunità della ricerca scientifica, dalle compagnie elettriche e dagli enti europei. L’inclusione di carichi flessibili, distribuiti, e associati a Fonti di Energia Rinnovabile (FERs) tra gli attori partecipanti alla fruizione dei servizi ancillari come mezzo per aggiungere flessibilità alla rete elettrica, instaura nuove opportunità e sfide scientifiche, di mercato e di gestione del sistema a livello europeo. La tesi discute quindi l’integrazione dei carichi flessibili nella partecipazione dei servizi energetici di rete. La tesi fornisce un’analisi incrementale che, partendo da esempi applicativi arriva alla progettazione di sistemi di controllo realistici. Nella prima parte della tesi vengono introdotte e caratterizzate le trasformazioni associate al sistema elettrico ed al mercato dell’energia elettrica, rimarcando la separazione tra Servizi Ancillari Globali e Locali. Sulla base di questa separazione, la tesi propone una sequenza di studi e lavori incrementali che hanno lo scopo di fornire gli strumenti, le considerazioni e le valutazioni necessarie per la progettazione e l’implementazione di un sistema di controllo sempre più sofisticato in grado di fornire servizi di rete tramite l’utilizzo di carichi flessibili, quali
Veicoli Elettrici (PEVs) e Sistemi di Accumulo dell’Energia (ESSs). Nella prima parte della sezione 3 della tesi l’attenzione è focalizzata sui Servizi Ancillari Locali. Nella seconda parte della stessa sezione i risultati ottenuti a livello locale diventano oggetto di revisione ed estensione al fine di adattare l’impianto, costruito al livello di Servizi Locali, a scenari associati a Servizi Ancillari Globali. Tutti i lavori proposti
sono accompagnati da simulazioni ed emulazioni integrate con infrastrutture ICT reali. I risultati delle simulazioni sono presentati e ampiamente discussi, per evidenziare l’efficacia delle soluzioni proposte ed aspetti che danno spunto per possibili sviluppi futuri
Decentralized Model Predictive Control of Plug-in Electric Vehicles Charging based on the Alternating Direction Method of Multipliers
Full text linkThis paper presents a decentralized Model Predictive Control (MPC) for Plug-in Electric Vehicles (PEVs) charging, in presence of both network and drivers' requirements. The open loop optimal control problem at the basis of MPC is modeled as a consesus with regularization optimization problem and solved by means of the decentralized Alternating Direction Method of Multipliers (ADMM). Simulations performed on a realistic test case show the potential of the proposed control approach and allow to provide a preliminary evaluation of the compatibility between the required computational effort and the application in real time charging control system
Ensuring the Stability of Power Systems Against Dynamic Load Altering Attacks: A Robust Control Scheme Using Energy Storage Systems
Full text linkThis paper presents a robust protection scheme to protect the power transmission network against a class of feedback-based attacks referred in the literature as "Dynamic Load Altering Attacks" (D-LAAs). The proposed scheme envisages the usage of Energy Storage Systems (ESSs) to avoid the destabilising effects that a malicious state feedback has on the power network generators. The methodologies utilised are based on results from polytopic uncertain systems, invariance theory and Lyapunov arguments. Numerical simulations on a test scenario validate the proposed approach
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
Decentralised Model Predictive Control of Electric Vehicles Charging
Full text linkThis paper presents a decentralised control strategy for the management of simultaneous charging sessions of electric vehicles. The proposed approach is based on the model predictive control methodology and the Lagrangian decomposition of the constrained optimization problem which is solved at each sampling time. This strategy allows the computation of the charging profiles in a decentralised way, with limited information exchange between the electric vehicles. The simulation results show the potential of the proposed approach in relation to the problem of shaving the aggregated power withdrawal from the electricity distribution grid, while still satisfying drivers’ preferences for charging
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