1,720,961 research outputs found
Methods for security enhancement in low-inertia and non-synchronous power systems
No full textQuesta tesi di dottorato riporta i risultati ottenuti dall'autore durante le attività triennali del XXXVI ciclo del corso di dottorato in Ingegneria Elettrica e dell'Informazione del Politecnico di Bari. L'obiettivo principale di questo lavoro è stato quello di sviluppare metodologie e controlli per la gestione di risorse energetiche distribuite con lo scopo di promuovere la diffusione di microgrid isolate. Inoltre, l'obiettivo è stato quello di migliorare la capacità di accoglienza dei sistemi di distribuzione isolati, garantendone il funzionamento sicuro e stabile.
Il controllo e funzionamento di una microgrid in isola sono stati affrontati nel loro complesso, partendo dalla gestione ottimale delle risorse fino ad arrivare al controllo del funzionamento dinamico dei componenti della rete. In questi studi, l'attenzione si è incentrata principalmente su una piccola isola italiana di riferimento. Sulla base della sua struttura, sono stati sviluppati un algoritmo di pianificazione operativa (che opera sulla scala gerarchica di controllo più elevata e una scala temporale dell’ordine delle ore) e un algoritmo in tempo reale per la valutazione e l'allocazione della riserva operativa (che opera su una scala gerarchica di controllo intermedia e una scala temporale da 1 minuto a 15 minuti). Inoltre, sempre in relazione alla bassa inerzia delle microreti e delle reti di distribuzione in isola, sono state studiate e realizzate soluzioni innovative per la fornitura di servizi ancillari di regolazione veloce della frequenza (che operano su la scala gerarchica di controllo più bassa e su una scala temporale di pochi secondi). Tutte le metodologie discusse in questa tesi hanno mostrato un miglioramento della sicurezza e della stabilità dei sistemi di distribuzione isolati e la riduzione dei costi operativi e delle emissioni di gas serra.This doctoral thesis reports the results carried out by the author during the three-year activities of the XXXVI cycle of the Ph.D. course in Electrical and Information Engineering at Politecnico di Bari. The main goal of this work was to develop methodologies and controls for managing distributed energy resources with the aim to promote the deployment of isolated microgrids. Moreover, the goal was to enhance the hosting capacity of isolated distribution systems, ensuring their secure and stable operation. The control and operation of an islanded microgrid have been addressed in their entirety, starting with the optimal management of resources and ending with the control of the dynamic operation of grid components. In these studies, the main focus has been on a small Italian reference island. Based on its structure, an operational planning algorithm (operating on the highest hierarchical control level and a time scale on the order of hours) and a real-time algorithm for operating reserve assessment and allocation (operating on an intermediate hierarchical control level and a time scale from 1 minute to 15 minutes) were developed. Furthermore, concerning the low system inertia of microgrids and isolated distribution networks, innovative solutions for the provision of fast frequency support ancillary services, operating on the lowest hierarchical control level and a time scale of a few seconds, were studied and implemented. All of the methodologies discussed in this thesis have enhanced the security and stability of isolated distribution systems and reduced operational costs and greenhouse gas emissions
A blockchain-based architecture for tracking and remunerating fast frequency response
Full text linkThe increasing penetration of renewable sources introduces new challenges for power systems’ stability, especially for isolated systems characterized by low inertia and powered through a single diesel power plant, such as it happens in small islands. For this reason, research projects, such as the BLORIN project, have focused on the provision of energy services involving electric vehicles owners residential users to mitigate possible issues on the power system due to unpredictable generation from renewable sources. The residential users were part of a blockchain-based platform, which also the Distributors/Aggregators were accessing. This paper describes the integrated framework that was set up to verify the feasibility and effectiveness of some of the methodologies developed in the BLORIN project for fast frequency response in isolated systems characterized by low rotational inertia. The validation of the proposed methodologies for fast frequency response using Vehicle-to-Grid or Demand Response programs was indeed carried out by emulating the dynamic behavior of different power resources in a Power Hardware-in-the-Loop environment using the equipment installed at the LabZERO laboratory of Politecnico di Bari, Italy. The laboratory, hosting a physical microgrid as well as Power Hardware-in-the-Loop facilities, was integrated within the BLORIN blockchain platform. The tests were conducted by assuming renewable generation development scenarios (mainly photovoltaic) and simulating the system under the worst-case scenarios caused by reduced rotational inertia. The experiments allowed to fully simulate users’ interaction with the energy system and blockchain network reproducing realistic conditions of tracking and remuneration of users’ services. The results obtained show the effectiveness of the BLORIN platform for the provision, tracking and remuneration of grid services by electric vehicles and end users, and the benefits that are achieved in terms of reducing the number of diesel generating units that need to be powered on just to provide operational reserve due to the penetration of renewable sources, resulting in fuel savings and reduced emissions
Power Hardware-in-the-Loop Test of a Low-Cost Synthetic Inertia Controller for Battery Energy Storage System
Full text linkIn the last years, the overall system inertia is decreasing due to the growing amount of energy resources connected to the grid by means of power inverters. As a consequence, reduced levels of inertia can affect the power system stability since slight variations of power generation or load may cause wider frequency deviations and higher rate of change of frequency (RoCoF) values. To mitigate this trouble, end-user distributed energy resources (DERs) interfaced through grid-following inverters, if opportunely controlled, can provide additional inertia. This paper investigated the possibility of improving the control law implemented by a low-cost controller on remotely controllable legacy DERs to provide synthetic inertia (SI) contributions. With this aim, power hardware-in-the-loop simulations were carried out to test the capability of the proposed controller to autonomously measure frequency and RoCoF and provide SI actions by controlling an actual battery energy storage system
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
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
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