1,720,962 research outputs found
High-level control algorithms for maximising energy efficiency of solar nano-grids designed for energy access
Full text linkPeer-to-peer interconnection of households having on-site batteries, four-port DC-DC converters and solar panels to form four-port DC-DC converter-enabled solar nano-grids is an emerging bottom-up approach for providing affordable energy access to rural areas. However, power losses which include battery charge and discharge losses, distribution losses and converter losses are one of the technical barriers hindering the practical deployment and operation of solar nano-grids in rural areas. Power losses reduce the energy efficiency of solar nano-grids. This research aimed to answer the following research question:
What control algorithms can be developed to address the problem of maximising the energy efficiency of four-port DC-DC converter-enabled solar nano-grids that are designed for energy access?
Solar nano-grids with star and hybrid distribution network configurations were considered in this research. Three novel high-level control algorithms were developed to answer the research question. The first one was a centralised control algorithm, the second one was a quasi-consensus based distributed control algorithm and the third one was a distributed state-of-charge based droop control algorithm. Numerical and simulation results carried out in Python showed the effectiveness of the developed control algorithms for addressing the research question through the considered solar nano-grid configurations.
The first and second control algorithms addressed the research question for the star solar nano-grid configuration through optimisation. Firstly, a high fidelity steady-state model of the solar nano-grid was developed and a new two-stage convex power loss optimisation problem was formulated. The formulated optimisation problem did not require either linearisation or convex relaxation of power flow equations, making it scalable and computationally efficient. Then, the first and second control algorithms were developed to solve the formulated optimisation problem in a centralised and quasi-distributed manner respectively.
The third algorithm addressed the research question for both the star and hybrid solar nano-grid configurations through balancing the state-of-charge of the batteries in a distributed manner. In this algorithm, household distribution voltages were adjusted in proportional to the state-of-charge of their local batteries, creating an automatic power flow between the households each time there was a slight change in the battery state-of-charge. Due to the automatic power flow between the households, the magnitude of current flow at every time instant in the solar nano-grid was low, thus, keeping the power losses to a minimum.
The present work aimed to contribute towards the universal energy access agenda by focussing specifically on the third target of the United Nation’s Sustainable Development Goal 7 - doubling the global rate of improvement in energy efficiency by 2030. There is a lot of work that still needs to be done to achieve this goal. Nonetheless, the present research has made a significant step towards improving energy efficiency by developing control algorithms that minimise the solar nano-grid power losses
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
Power loss minimization of off-grid solar DC nano-grids—part I : centralized control algorithm
Full text linkPeer-to-peer interconnection of households having on-site batteries, multi-port converters and solar panels to form a multi-port converter-enabled solar DC nano-grid is an emerging approach for providing affordable energy access in rural areas. Battery charge and discharge losses, distribution losses and converter losses are significant problem when operating such nano-grids. This paper presents a centralized control algorithm that can help address the power loss problem. The proposed algorithm uses a new problem formulation where the power loss problem is formulated as a two-stage convex optimization problem. The first stage of the optimization problem is an optimal battery dispatch problem for determining optimal battery charge and discharge currents. The second stage is an optimal current flow problem for determining optimal distribution voltages which corresponds to the optimal battery currents. Simulation results of the nano-grid show that the proposed algorithm can minimize the nano-grid power losses while facilitating the power exchange between the households. The proposed algorithm is suitable for small nano-grids where privacy of households is not a concern. In Part II of this paper we propose a distributed control algorithm that preserves the privacy of the households especially where the size of the nano-grid is large
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
Distributed State of Charge-Based Droop Control Algorithm for Reducing Power Losses in Multi-Port Converter-Enabled Solar DC Nano-Grids
No full textThis paper aims to address the power loss problem of multi-port converter-enabled solar DC nano-grids (or simply nano-grids) that are designed to provide energy access in rural areas. Nano-grids are low voltage DC energy systems that are built for energy access by gradually interconnecting households that have solar panels, batteries and multi-port converters. Due to low distribution voltage levels (≤120 V), scattered households in rural areas and bidirectional power exchange between the households, power losses such as distribution line losses, battery charge/discharge losses and converter losses are significant in nano-grids. As batteries are distributed in each household and the nano-grid network configuration is dynamic in nature owing to the gradual interconnection of households, addressing the power loss problem using conventional optimization techniques is a challenge. To address the challenge, we propose a novel distributed state of charge-based droop control algorithm that does not require prior knowledge of the nano-grid network configuration. The proposed algorithm minimizes the power losses by reducing the magnitude of power flow in the nano-grid at each time instant through battery state of charge balancing. Numerical and simulation results demonstrate the effectiveness of the proposed algorithm
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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