1,720,964 research outputs found
Optimal distribution network planning applying heuristic algorithms considering allocation of PV rooftop generation
No full textThis paper deals with the optimal routing of Electrical Distribution Network in two voltage levels, taking on account the underground implementation in a geo-referenced area, in other words, the conductor must follow the street's route. The model was developed with a heuristic with a graph theory approach. The model was implemented in an area of Foz do Iguaçu in Medianeira, Brazil, reaching interesting result that can help to the planning electrical engineering in the design process. © 2020 IEEE
Optimal Hierarchical Control for Smart Grid Inverters Using Stability Margin Evaluating Transient Voltage for Photovoltaic System
No full textThis research proposed an optimal control approach for a smart grid electrical system with photovoltaic generation, where the control variables are voltage and frequency, which aims to improve the performance through addressing the need for a balance between the minimization of error and the operational cost. The proposed control scheme incorporates the latest advancements in heuristics and hierarchical control strategies to provide an efficient and effective solution for the smart grid electrical system control. Implementing the optimal control scheme in a smart power grid is expected to bring significant benefits, such as the reduced impact of renewable energy sources, improved stability, reliability and efficiency of the power grid, and enhanced overall performance. The optimal coefficient values are found by minimizing the cost functions, which leads to a more efficient system performance. The voltage output response of the system in a steady state is over-damped, with no overshoot, but with a 5% oscillation around the target voltage level that remains consistent. Despite the complexity of nonlinear elements’ behavior and multiple system interactions, the response time is fast and the settling time is less than 0.4 s. This means that even with an increase in load, the system output still meets the power and voltage requirements of the system, ensuring efficient and effective performance of the smart grid electrical systems
Optimal Secondary and Tertiary Hierarchical Control for Photovoltaic System Generation Using a Heuristic Approach
No full textThis paper proposes a secondary and tertiary optimal methodology to control an electrical distribution system with photovoltaic generation. The control is hierarchical, and the optimization relies on heuristics; thus, the optimal approach minimizes the error, comparing the output with the reference, but the methodology maintains an acceptable operational cost. The objective function determines the optimal controller's coefficient to improve system performance. The steady-state response does not have an overshoot, and it is over-damped. Considering the presence of non-linear elements, the response time is sufficiently fast. Moreover, despite the increase in load, the settling time is less than 0.4 seconds, and the system output satisfies the system requirements in terms of power and voltage
Novel Single Stage DC/AC Power Inverter for a Standalone Photovoltaic System Controlled by a Double Loop Scheme
No full textThis paper proposes a novel double-loop control strategy for a single-stage boost inverter for a standalone photovoltaic system. This strategy includes compensation filters to avoid high currents and abrupt voltage variations. The final load has a non-linear behavior, representing new electronic components in the grid. The system is implemented in Matlab/Simulink platform, and the entire system is tested in situations like a temporary short circuit, non-linear loads, abrupt load variations, and input disturbance. The proposed control strategy allows the system a continuous operation, which means that the protection system is not triggered. Secondly, the total harmonic distortion (THD) percentage is a maximum of 1.845%, and the maximum voltage deviation compared with the reference error is 4%. Finally, the system efficiency average is more significant than 77% in the operation range
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
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
Control Strategy Applied to Smart Photovoltaic Inverters for Reactive Power Exchange Through Volt-Var Control to Improve Voltage Quality in Electrical Distribution Networks
No full textPhotovoltaic (PV) generation systems have become part of the electrical distribution networks due to their clean energy and adaptability. The increasing energy consumption and the several load types in the distribution network could produce voltage deviation. Therefore, there are some strategies, which are used to solve this problem, for example, capacitor banks, voltage regulators, transformer tap variation, static Var compensators, and reactive power exchange employing inverters. This article presents a smart inverter able to deliver and absorb reactive power through Volt-Var control to solve voltage deviations. The inverter compensates for voltage deviation in the primary transformer, whether inductive or capacitive loads are connected in the point of common coupling (PCC). In consequence, the inverter improves the voltage quality in the entire network. Finally, total harmonics percentage (THD) and frequency deviation have an acceptable performance during the operation, due to the inverter hardware configuration, and the phase-locked loop (PLL) implementation
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
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