1,720,972 research outputs found
Reliability Studies in Information and Communication Technologydominated Distribution Systems: Adequacy Assessment of Cyber-Physical Distribution Networks Including Microgrids
Full text linkIn the past decade, the emergence of high-speed, reliable, and smart computer systems has caused a revolution in control systems, and digital systems are replacing traditional and analogous control systems in industries. Power systems are not an exception, and Information and Communication Technologies (ICTs) are increasingly integrated into these systems. Due to the increasing deployment of ICTs in power infrastructures, the power systems will become “cyber-physical power systems.” While it is exciting to contemplate all the benefits that ICTs bring to power systems, we deal with not-so-perfect components and designs of ICTs, so failures do occur in these technologies; therefore, ICTs influence the reliability of the overall system. With this perspective, the fundamental objective of this Ph.D. research work is to develop suitable methodologies for assessing the impact of ICT component failures on the reliability of cyber-physical distribution systems and microgrids. To achieve the primal objectives of this study, three novel reliability assessment frameworks are proposed for Cyber-Physical Microgrids (CPMGs) and Cyber-Physical Distribution Systems (CPDSs).
This thesis includes two parts. Part 1 consists of five chapters and intends to provide supplementary explanations for the appended papers in Part 2. This part presents a comprehensive overview of the literature on the reliability of CPDSs and CPMGs. It explains the Monte Carlo Simulation (MCS) and state enumeration method, which were used to develop the reliability assessment frameworks. It also provides some additional simulation results.
The proposed frameworks are explained in the appended papers. In the first paper, an MCS-based framework for the adequacy assessment of grid-connected CPMGs is developed. The impact of the failure of ICT components involved in the system control on the reliability of grid-connected CPMGs is investigated through the proposed framework. This framework can also be applied to isolated CPMGs with minimum effort. This framework is further extended in the second paper to include multi-microgrid considerations. In addition, a methodology is proposed to investigate the impact of ICT components’ failure on the functioning of protection and restoration systems when a centralized scheme is adopted for system protection. Both of these frameworks are based on MCS. While reliability assessment methods based on MCS are effective and can include the detail of the system as desired, they are relatively time-consuming. In this regard, a novel analytical methodology is proposed in the third paper for the adequacy assessment of Cyber-Physical Multi-Microgrid (CPMMG) distribution systems to accelerate the procedure. The proposed framework uses the state enumeration method, classification of components, graph theory, reliability block diagram, and probability theory.
Besides the main objectives that define the main research questions of this thesis, several other questions were raised, which are partially answered in this thesis. In response to these research questions, a detailed model for the reliability assessment of solar farms is proposed, a generic scheme for treating uncertainties associated with the duration of contingency events is outlined, and two new reliability indices are formulated to take the impact of ownership of the microgrids in a multi-microgrid system into account.
The effectiveness of the proposed methodologies is demonstrated by applying them to suitable case studies. Further support is provided by analyzing the impact of device-level failures of cyber systems on the reliability of CPMGs and CPMMG distribution networks through quantifying well-known reliability indices. In brief, the primary conclusion of this thesis is that the adverse impact of device-level failures of cyber systems on the reliability of distribution systems and microgrids can be effectively mitigated by improving the cyber system topology and adding redundancy for critical cyber components in the system. In such an enhanced cyber system, the adverse impact of cyber failures compared to the functionalities they bring to distribution systems is negligible. However, to achieve such a cyber system, reliability studies are crucial
Quantum annealing applications, challenges and limitations for optimisation problems compared to classical solvers
No full textQuantum computing is rapidly advancing, harnessing the power of qubits’ superposition and entanglement for computational advantages over classical systems. However, scalability poses a primary challenge for these machines. By implementing a hybrid workflow between classical and quantum computing instances, D-Wave has succeeded in pushing this boundary to the realm of industrial use. Furthermore, they have recently opened up to mixed integer linear programming (MILP) problems, expanding their applicability to many relevant problems in the field of optimisation. However, the extent of their suitability for diverse problem categories and their computational advantages remains unclear. This study conducts a comprehensive examination by applying a selection of diverse case studies to benchmark the performance of D-Wave’s hybrid solver against that of industry-leading solvers such as CPLEX, Gurobi, and IPOPT. The findings indicate that D-Wave’s hybrid solver is currently most advantageous for integer quadratic objective functions and shows potential for quadratic constraints. To illustrate this, we applied it to a real-world energy problem, specifically the MILP unit commitment problem. While D-Wave can solve such problems, its performance has not yet matched that of its classical counterparts.</p
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
Towards a Sustainable Bolivian Power System: Impacts of Gas Subsidies and Variable Renewable Energy Sources
Full text linkImens utviklingsland navigerer det komplekse landskapet i energiomstillingen, står de overfor unike utfordringer som økonomiske begrensninger, store behov for oppgradering av infrastruktur og et energisystem avhengig av fossile brensler. For å muliggjøre informert beslutningstaking som kan balansere ulike faktorer samtidig som de sikrer transparens er åpnet tilgjengelige energisystemmodeller essensielle verktøy.
Denne avhandlingen fokuserer på å adressere kritiske forskningsspørsmål relatert til modellering og analyse av det bolivianske kraftsystemet ved bruk og utvidelse av åpent tilgjengelige modeller. Hovedmålene er å forbedre representasjonen av Bolivias energiinfrastruktur i PyPSA-Earth-BO-modellen, undersøke virkningen av subsidiering av fossile brensler, implementere et verktøy for pålitelighetsvurdering og integrere det bolivianske kraftsystemet i EMPIRE-modellen for komparativ analyse.
Den første studien forbedrer nøyaktigheten til PyPSA-Earth-BO-modellen betydelig ved å øke oppløsningen av representasjonen av det fysiske systemet, gjøre kritiske forbedringer i dataen som benyttes og implementere begrensninger som sikrer mer realistiske resultater. Forbedringene muliggjør en omfattende analyse av virkningen av subsidiering av fossile brensler på Bolivias energiomstilling. Den andre studien introduserer et sammensatt verktøy for å utføre pålitelighetsstudier av Bolivias fremtidige kraftsystem ved hjelp av Monte Carlo simulering. Dette fasiliterer en diskusjon rundt de kritiske komponentene i modellen som brukes til å representere Bolivia i 2040. Den tredje studien integrerer det bolivianske kraftsystemet i EMPIRE-modellen, som muliggjør en komparativ analyse mellom dens multi-horisont stokastiske programmeringsmetode og PyPSA-Earths deterministiske modell.
Funnene i denne avhandlingen har betydelige implikasjoner for modellering av energisystemer og politisk beslutningstaking i Bolivia. Undersøkelsen av effektene av drivstoffsubsidier viser at de potensielle besparelsene fra reduksjonen av disse kan finansiere de nødvendige investeringene for en bærekraftig energiomstilling, når subsidene viser seg å overgå 5 milliarder euro. Den vellykkede implementeringen av pålitelighetsverktøyet i PyPSA-Earth-BO gir en første indikasjon på viktigheten av investeringer i strømnettet for å forbedre påliteligheten til det modellerte kraftsystemet. Når man sammenligner PyPSA-Earth-BO og EMPIRE, blir betydelige avveininger mellom deres modelleringsmetoder tydelige. PyPSA-Earth-BO har en tendens til å være overoptimistisk om potensialet for fornybar energi, mens EMPIRE påvirkes av svært forenklede lastflytsbegrensninger. PyPSA-Earth-BO gir en mer detaljert utvidelse av strømnettet og lokal strømgenerering, og fremhever fordelene ved sin høyoppløste modellering. I kontrast tilbyr EMPIRE en mer robust investeringsstrategi som tar hensyn til både variasjon og usikkerhet knyttet til vær, og viser sin styrke i langsiktig strategisk planlegging.As developing countries navigate the complex landscape of the energy transition, they face unique challenges such as financial constraints, infrastructural limitations, and reliance on fossil fuels. In this context, open-source energy system models emerge as essential tools for facilitating informed decision-making, balancing numerous factors while ensuring transparency.
This thesis focuses on addressing critical research questions related to modeling and analyzing the Bolivian power system using and extending open-source tools. The primary objectives are to enhance the representation of Bolivia's energy infrastructure in the PyPSA-Earth-BO model, investigate the impact of natural gas subsidies, implement a reliability assessment tool, and integrate the Bolivian power system into the EMPIRE model for comparative analysis.
The first study significantly improves the accuracy of the PyPSA-Earth-BO model by enhancing the spatial representation, critically improving the input data, and implementing constraints aimed at ensuring a more realistic output. This enables a comprehensive analysis of the impact of natural gas subsidies on Bolivia's energy transition. The second study introduces a composite system adequacy assessment tool to evaluate the reliability of Bolivia's future power system leveraging Monte Carlo simulation, facilitating an investigation and discussion surrounding the critical nodes and components of the model used to represent Bolivia in 2040. The third study successfully integrates the Bolivian power system into the EMPIRE model, enabling a comparative analysis between its multi-horizon stochastic programming approach and PyPSA-Earth's single-period deterministic model.
The findings of this thesis have significant implications for energy system modeling and policy decision-making in Bolivia and beyond. Examining the effects of fuel subsidies which succeeded 5 billion euro, shows that the potential savings from their reduction can adequately finance the investments necessary for a sustainable energy transition. The successful implementation of the reliability tool in PyPSA-Earth-BO provides preliminary insights into the importance of transmission grid investments to improve the system adequacy of the modeled power system. When comparing PyPSA-Earth-BO and EMPIRE, significant trade-offs between their modeling approaches become evident. PyPSA-Earth-BO tends to be overly optimistic about renewable energy potential, while EMPIRE grapples with highly approximated load flow restrictions. PyPSA-Earth-BO provides a more detailed transmission line expansion and local generation distribution, highlighting the advantages of its high-resolution modeling. In contrast, EMPIRE offers a more robust investment strategy that accounts for both weather variation and weather uncertainty, showcasing its strength in long-term strategic planning
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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