1,721,098 research outputs found
Contribution to the study of autonomous micro-grid systems supplied by photovoltaic sources
No full textL'orientation énergétique actuelle vers le développement de systèmes électriques isolés, s'est traduit par l'établissement de nouvelles directives sur les performances et la fiabilité des structures de puissance mises en oeuvre, en particulier ceux à base d'énergies renouvelables. C'est dans ce contexte que s'inscrivent ces travaux de thèse, qui aboutissent à l'élaboration de nouveaux outils destinés à l'amélioration de la qualité d'énergie et de la stabilité d'un micro-réseau autonome. Concernant l'optimisation énergétique des interfaces de conversion pour un réseau autonome, nous avons développé de nouveaux algorithmes de commande basés sur le concept de platitude des systèmes différentiels. L'avantage de cette technique réside dans la possibilité d'implémentation de régulateurs à une boucle. Cela garantit des propriétés dynamiques élevées en asservissement et en régulation. De plus, une prédiction exacte de l'évolution des variables d'états du système est possible. Concernant la stabilité des micro-réseaux autonomes, nous avons proposé des outils pour traiter les phénomènes d'instabilités, causés notamment par la perte d'informations de charges et par le phénomène de résonance des filtres d'interconnexionThe actual electrical energy demand focuses on the development of stand-alone electrical systems which leads to the definition of new directives on performances and reliability of the electrical structures, especially those based on renewable energy. The main objective of this work concerns the development of new tools to improve the power quality and the stability of autonomous micro-grid systems. In this aim, new control algorithms based on the concept of differential flatness have been developed. The main advantage of the proposed technique is the possibility of implementing one loop controllers ensuring high dynamic properties. In the same time, it allows accurate prediction of the evolution of all state variables of the system. Concerning the stability of the autonomous micro-grid systems, we proposed tools to deal with instability phenomena either caused by the loss of load information and the resonance phenomenon of the passive filter
Contribution à l'étude de micro-réseaux autonomes alimentés par des sources photovoltaïques
No full textThe actual electrical energy demand focuses on the development of stand-alone electrical systems which leads to the definition of new directives on performances and reliability of the electrical structures, especially those based on renewable energy. The main objective of this work concerns the development of new tools to improve the power quality and the stability of autonomous micro-grid systems. In this aim, new control algorithms based on the concept of differential flatness have been developed. The main advantage of the proposed technique is the possibility of implementing one loop controllers ensuring high dynamic properties. In the same time, it allows accurate prediction of the evolution of all state variables of the system. Concerning the stability of the autonomous micro-grid systems, we proposed tools to deal with instability phenomena either caused by the loss of load information and the resonance phenomenon of the passive filtersL'orientation énergétique actuelle vers le développement de systèmes électriques isolés, s'est traduit par l'établissement de nouvelles directives sur les performances et la fiabilité des structures de puissance mises en oeuvre, en particulier ceux à base d'énergies renouvelables. C'est dans ce contexte que s'inscrivent ces travaux de thèse, qui aboutissent à l'élaboration de nouveaux outils destinés à l'amélioration de la qualité d'énergie et de la stabilité d'un micro-réseau autonome. Concernant l'optimisation énergétique des interfaces de conversion pour un réseau autonome, nous avons développé de nouveaux algorithmes de commande basés sur le concept de platitude des systèmes différentiels. L'avantage de cette technique réside dans la possibilité d'implémentation de régulateurs à une boucle. Cela garantit des propriétés dynamiques élevées en asservissement et en régulation. De plus, une prédiction exacte de l'évolution des variables d'états du système est possible. Concernant la stabilité des micro-réseaux autonomes, nous avons proposé des outils pour traiter les phénomènes d'instabilités, causés notamment par la perte d'informations de charges et par le phénomène de résonance des filtres d'interconnexio
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
Energy management strategies for microgrids integrating distributed energy storage units
No full textDans ce travail de thèse, de nouvelles techniques de commandes coopératives sont proposées pour pallier les limites du réglage primaire des Micro-réseaux AC autonomes intégrant plusieurs unités de stockage d'énergie décentralisées (MG-DESU). Ces nouvelles commandes distribuées prennent en compte l'état des sources d'énergie et des unités de stockage comme l'état de charge (SoC) et le coût de production des batteries, ainsi que l'efficacité intrinsèque et la dynamique de chaque générateur distribué (DG). Ces commandes corrigent également les déviations de fréquence et de tension des DGs engendrées par le contrôle primaire, tout en garantissant la stabilité du système. Deux stratégies d’équilibrage du SoC (SoC balancing) des DESU basées sur le consensus sont d’abord développées pour éviter une dégradation inégale des batteries, étendre leur durée de vie et réduire la charge de maintenance. Ensuite, une étude de stabilité petit signal du MG-DESU est réalisée afin d’évaluer l’influence des paramètres de contrôle, du délai de communication et des éléments du MG (lignes, charges, etc.) sur la stabilité locale du système avec les stratégies proposées. Enfin, le coût global de la production d'énergie des MG-DESU est minimisé grâce à une stratégie de dispatching économique basée sur le consensus et le principe des coûts incrémentaux égaux. Les performances des différentes stratégies de contrôle élaborées dans cette thèse, sont validées expérimentalement sur un banc d’essai PHIL (Power Hardware In-the-Loop), développé au sein du laboratoire, et ce pour différents scénarios de fonctionnement du MG-DESU.In this thesis work, new cooperative control techniques have been proposed to overcome the various limitations of primary control of autonomous AC Microgrids integrating multiple distributed energy storage units (MG-DESUs). These new controls take into account the state of energy sources and storage units, such as the state of charge (SoC) and production cost of batteries, as well as the intrinsic efficiency and dynamics of each distributed generator (DG). These controls also correct DG frequency and voltage deviations caused by primary control, while ensuring system stability. Two consensus-based SoC balancing strategies were first developed to avoid uneven degradation of the batteries, extend their service life and reduce the maintenance burden. Secondly, a small-signal stability study of the MG-DESU was carried out in order to evaluate the influence of control parameters, communication delay and system elements (lines, loads, etc.) on the local stability of the system. Finally, the overall cost of the MG-DESU energy production is minimized thanks to an economic dispatching strategy based on consensus and equal incremental cost principle. The performance of the proposed control strategies in this thesis was validated experimentally on a laboratory-developed Power Hardware In-the-Loop test bench for various MG-DESU operating scenarios
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
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