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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Analysis of the reliability for the 132/66/22 KV distribution network within ESKOM’s Eastern Cape operating unit

Pantshwa, Athini January 2017 (has links)
A stable and reliable electrical power supply system is an inevitable pre-requisite for the technological and economic growth of any nation. Due to this, utilities must strive and ensure that the customer’s reliability requirements are met and that the regulators requirements are satisfied at the lowest possible cost. It is known fact around the world that 90% of the customer service interruptions are caused due to failure in distribution system. Therefore, it is worth considering reliability assessments as it provides an opportunity to incorporate the cost or losses incurred by the utilities customer as a result of power failure. This must be considered in the planning and operating practices. The system modelling and simulation study is carried out on one of the district’s distribution system which consists of 132 kV, 66 kV and 22 kV network in Aliwal North Sector ECOU. The reliability assessment is done on the 22, 66 and 132 kV system to assess the performance of the present system and also predictive reliability analysis for the future system considering load growth and system expansion. The alternative which gives low SAIDI, SAIFI and minimum breakeven costs is being assessed and considered. The reliability of 132 kV system could be further improved by constructing a new 132 kV line from a different source of supply and connecting with line coming from another district (reserve) at reasonable break even cost. The decision base could be further improved by having Aliwal North Sector context interruption cost. However, the historical data which may be used in Aliwal North Sector to acquire interruption costs from the customers are being proposed. The focus should be on improving the power quality on constrained networks first, then the reliability. Therefore for the Aliwal North power system network it is imperative that Eskom invest on the reliability of this network. This dissertation also analysed load reflected economic benefit versus performance expectations that should be optimized through achieving a balance between network performance (SAIDI) improvement, and total life cycle cost (to Eskom as well as the economy). Reliability analysis conducted in this dissertation used Aliwal North power system network as a case study; the results proved that the system is vulnerable to faults, planned and unplanned outages. Reliability evaluation studies were conducted on the system using DigSilent software in conjunction with FME. These two models gave accurate results with acceptable variance in most indices except for the ENS where the variance was quite significant. It can be concluded that DigSilent results are the most accurate results in all three reliability evaluation scenarios for the Aliwal North Power System, best interpretation being that of DigSilent.
12

LEARNING AND OPTIMIZATION FOR REAL-TIME MICROGRID ENERGY MANAGEMENT SYSTEMS

Unknown Date (has links)
Microgrid is an essential part of the nation’s smart grid deployment plan, recognized especially for improving efficiency, reliability, flexibility, and resiliency of the electricity system. Since microgrid consists of different distributed generation units, microgrid scheduling and real-time dispatch play a crucial role in maintaining economic, reliable, and resilient operation. The control and optimization performances of the existing online approaches degrade significantly in microgrid applications with missing forecast information, large state space, and multiple probabilistic events. This dissertation focuses on these challenges and proposes efficient online learning and optimization-based approaches. For addressing the missing forecast challenges on online microgrid operations, a new fitted rolling horizon control (fitted-RHC) approach is proposed in Chapter 2. The proposed fitted-RHC approach is designed with a regression algorithm that utilizes the empirical knowledge obtain from the day-ahead forecast to make microgrid real-time decisions whenever the intra-day forecast data is unavailable. Simulation results show that the proposed fitted-RHC approach can achieve the optimal policy for the deterministic case study and perform efficiently with the uncertain environment in the stochastic case study. / Includes bibliography. / Dissertation (PhD)--Florida Atlantic University, 2021. / FAU Electronic Theses and Dissertations Collection
13

Militär makt som säkerhetspolitiskt verktyg : En Smart Power analys av hur svensk militär verksamhet mellan 2008-2019 framställs genom strategiskt narrativ

Brandelius, Tom January 2019 (has links)
Småstaters ofta begränsade resurser innebär ett behov av optimering för att uppnå önskadeffekt. Dagens informationsflöde innebär dessutom att det inte räcker med att användaresurser på rätt sätt, alternativa berättelser kan motverka aktören och det narrativ som fårfäste hos allmänheten kan bli det som betraktas som sanningen. Den här undersökningen syftar till att analysera hur svensk militär verksamhet framställs avstatliga representanter i det offentliga rummet och hur detta kan bidra till en smartsäkerhetsstrategi. Genom en narrativ analys av elva händelser har en översikt skapats som sedan kontrolleratsmot definierade militära maktdimensioner i teorin Smart Power, vilka utgör grund för ensmart strategi. Undersökningen visar att det svenska strategiska narrativet används för att framhäva svenskaegenskaper i vad som kan beskrivas som en kampanj för Sverige som den moraliskastormakten. Detta görs bland annat genom att betona verksamhet som en del i enallomfattande ansats, framhäva defensiva förmågor och undvika egenintresse. Det svenska narrativet berör samtliga maktdimensioner över tiden vilket innebär godaförutsättningar för en framgångsrik strategi som dock behöver verkställas med skicklighet föratt få god effekt. En tydlig koppling mellan Försvarsmaktens uppgifter och berördamaktdimensioner är identifierad. Undersökningen tyder på att det inte behöver finnas enkonflikt mellan återgång till ett nationellt intresse och en smart säkerhetsstrategi, menmedvetenhet är avgörande.
14

Global Time-Independent Agent-Based Simulation for Transactive Energy System Dispatch and Schedule Forecasting

Chandler, Shawn Aaron 13 March 2015 (has links)
Electricity service providers (ESP) worldwide have increased their interest in the use of electrical distribution, transmission, generation, storage, and responsive load resources as integrated systems. Referred to commonly as "smart grid," their interest is driven by widespread goals to improve the operations, management and control of large-scale power systems. In this thesis I provide research into a novel agent-based simulation (ABS) approach for exploring smart grid system (SGS) dispatch, schedule forecasting and resource coordination. I model an electrical grid and its assets as an adaptive ABS, assigning an agent construct to every SGS resource including demand response, energy storage, and distributed generation assets. Importantly, real time is represented as an environment variable within the simulation, such that each resource is characterized temporally by multiple agents that reside in different times. The simulation contains at least as many agents per resource as there are time intervals being investigated. These agents may communicate with each other during the simulation, but only agents assigned to represent the same unique resource may exchange information between time periods. Thus, confined within each time interval, each resource agent may also interact with other resource agents. As with any agent-based model, the agents may also interact with the environment, in this case, containing forecasted environment, load and price information specific to each time interval. The resulting model is a time-independent global approach capable of: (1) capturing time-variant local grid conditions and distribution grid load balancing constraints; (2) capturing time-variant resource availability and price constraints, and finally, (3) simulating efficient unit-commitment real-time dispatches and schedule forecasts considering time-variant forecasted transactive market prices. This thesis details the need for such a system, discusses the form of the ABS, and analyzes the predictive behavior of the model through a critical lens by applying the resulting proof-of-concept simulation to a set of comprehensive validation scenarios. The resulting analysis demonstrates ABS as an effective tool for real-time dispatch and SGS schedule forecasting as applied to research, short-term economic operations planning and transactive systems alike. The model is shown to converge on economic opportunities regardless of the price or load-forecast shape and to correctly perform least-cost dispatch and schedule forecasting functionality.
15

De Prague à Riga : stratégies de mise en place du soft power de l’Union européenne dans les États du Partenariat oriental / From Prague to Riga : strategy implemented to establish EU’s soft power in Eastern Partnership countries

Lambert, Michael 07 December 2016 (has links)
Les États du Partenariat oriental (Ukraine, Moldavie, Biélorussie, Géorgie, Arménie, Azerbaïdjan) ainsi que les territoires séparatistesqui s’y trouvent (Transnistrie, République du Donbas, Crimée, Abkhazie, Ossétie du Sud, Haut-Karabakh) doivent déterminer leurappartenance à un ensemble géopolitique afin d’assurer leur prospérité mais aussi leur sécurité. Les options qui se présentent à euxpeuvent se résumer à une intégration au sein de l’Union européenne, de l’Union (Économique) Eurasiatique ou à un partenariat avec la Chine, et ce en raison de leur difficultés à survivre en tant que pays non-alignés, et des pressions exercées pour Bruxelles et parMoscou. La raison de ces pressions repose sur la souhait d’émergence de l’Union européenne en tant que puissance géopolitique mondiale, poussée notamment par les États-Unis pour contrebalancer l’influence de la Russie, et par le Kremlin qui souhaite conserver son influence dans ce qu’il considère encore comme sa zone d’influence légitime” plus de 25 ans après la chute de l’Union soviétique. Cette thèse analyse les tendance intra-européennes, avec l’approche normalisatrice des pays d’Europe de l’Ouest, qui cherchent un compromis avec la Russie, et ceux d’Europe de l’Est, qui voient dans les Institutions européennes un moyen de s’affirmer comme puissances régionale. Avec l’avènement du projet de Partenariat oriental lancé par la Pologne et la Suède en 2008, l’UE incarne ces deux tendances, parfois contradictoires, à travers la mise en place de ses stratégies d’influence - son soft power - sur le terrain. Une influence mis à mal par les membres de l’EaP qui détournent abondamment les fonds en provenance de l’UE en raison de la corruption qui règne au sein des institutions nationales. La Russie tente pour sa part de retrouver son influence mais en usant d’une approche plus musclée, parfois même relevant du domaine militaire - son hard power - comme le montrent l’annexion de la Crimée et la mise en place des Peacekeepers dans le Caucase du Sud. Alors que l’Union européenne peine à exercer son influence dans un contexte de crise économique post-2008, la Russie semble pour sa part disposer de nouveaux moyens pour accroitre son influence : la guerre hybride, l’instrumentalisation des réfugiés qui affluent aux portes de l’Espace Schengen, et l’Union Economique Eurasiatique. / The states of the Eastern Partnership (Ukraine, Moldova, Belarus, Georgia, Armenia, Azerbaijan) and the separatist territories therein (Transnistria, Republic of Donbas, Crimea, Abkhazia, South Ossetia, Nagorno-Karabakh) have to determine their membership in a geopolitical entity to ensure their prosperity and safety. Due to the difficulties to survive as non-aligned countries and pressures fromBrussels and Moscow, all of them either have to join the European Union, the Eurasian (Economic) Union or to establish an exclusivepartnership with China in the upcoming years.Pressure from the EU and Russia is based on the desire of the EU to emerge as a global geopolitical power, particularly pushed by theUnited States to counterbalance the influence of Russia, and the will of the Kremlin to retain its influence in what is presented in theRussian media as the “legitimate sphere of influence”, even more than 25 years after the fall of the Soviet Union.The PhD dissertation analyzes the political divergences between EU member states, with the “normalizing approach” of WesternEuropean countries that seek a compromise with Russia, and those from Eastern Europe currently trying to use the European institutionsas a means to become regional powers.The Eastern Partnership launched by Poland and Sweden in 2008 embodies these two, sometimes contradictory tendencies through theimplementation of EU’s strategies of influence - the EU’s soft power - in post-Soviet space. Nonetheless, those strategies are oftenundermined by members of the EaP, which abundantly divert funds from the EU, because of the corruption of local institutions. At thesame time, Russia is also trying to regain its influence, sometimes even by using military means - the so called Russian hard power - asshown by the annexation of the Crimea and the establishment of peacekeeping missions in South Caucasus.While the European Union hardly exerts its influence in a post-2008 economic crisis context, Russia seems to have developed new waysto weaken its opponents. Hybrid warfare, weaponizing of refugees, pushed by massive bombings in Syria, and the establishment of theEurasian Economic Union are under the most efficient ways to weaken the EU and NATO so far.
16

Analysis of the dynamic power requirements for controllable energy storage on photovoltaic microgrid

Horonga, Nyasha January 2016 (has links)
A dissertation submitted to the Facaulty of Engineering and the Built Environment, University of the Witwatersrand in ful lment of the requirements of the degree of Master of science in Engineering September 2016 / Standalone microgrid studies are being done because an expansion of the existing utility grids to supply power to remote communities is not feasible. Standalone microgrids can be considered as one of the solutions for remote communities because power can be generated close to these communities and it minimizes cost related to power transmission. Renewable energy sources with large uctuations are frequently the source of power for these standalone microgrids. The uctuating nature of these renewable sources can often lead to frequent blackouts. This research is aimed at minimizing power uctuations using controllable energy storage systems. This MSc focuses on the analysis of the ramp rate and delay time requirements for controllable energy storage system used in standalone PV microgrids. Measured insolation data and recorded load demand data for typical domestic appliances are used in this study to analyze ramp rates present. The ramp rates are then used to determine the range of energy storage ramp rate and delay time required to maintain the microgrid voltage within the standardized range of 1pu 5%. From the recorded data it has been observed that PV power can be sampled from at least 1-second intervals without losing important information. The 1 second averaged ramp rates obtained from the insolation data measurements have been found to have the highest value of 0.12pu/sec. However, this ramp rate increases to 0.3pu/sec when the allowable microgrid voltage band is narrow (1pu 5%). These insolation ramp rates are very low compared to the ramp rates of typical loads that can be connected to a microgrid. This means that, if the energy storage system is speci ed to meet the load ramp rate requirements, it will be able to respond to the uctuating PV power. The results obtained from the simulations con rm that energy storage system ramp rate plays an important role in the stability of a standalone microgrid. The minimum allowable energy storage ramp rate was found to be 8.15pu/sec for load transients with a ramp time of 20ms. This value is 28 times the energy storage ramp rate required to cancel out insolation uctuations. This further con rms that energy storage system ramp rates must be speci ed using the load demand data. The maximum allowable delay time was also found to be 0.53s to maintain the microgrid voltage within the standardized range of 1pu 5%. This delay time is applicable when canceling out only the insolation uctuations. To cancel out load transient power uctuations, there should be no delay time. / MT2017
17

Investigation into the steady-state load sharing of weak sources in a low voltage three-phase islanded microgrid

Wu, Meng-Chun Merelda January 2016 (has links)
A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in ful lment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 2016 / This research investigates the power sharing between distributed energy resources with voltage and frequency droop control. A case study based on voltage sources in an islanded microgrid is set up in the laboratory, referred to as: The Example Microgrid. The Example Microgrid consists of two synchronous generators, active and reactive power loads. A simulation model is constructed based on the laboratory set-up, where componentwise and system-wise testing are completed. The simulation results are validated with the experimental set-up, and it is concluded that the model accurately represents the physical system under steady-state conditions. Further simulation studies on conventional droop controllers are conducted based on the Example Microgrid model. The results indicate that the use of conventional droop control is inappropriate for small, low-voltage islanded microgrids. As a possible application of this work, three variations of adapted droop controllers are simulated and their performance evaluated. It is found that with the adapted droop controllers, the power sharing error can be minimised / M T 2016
18

Analysis of the effect of renewable generation on the power quality of the grid, modelling and analysis of harmonic and voltage distortion

Musoni, Nkusi Emmanuel January 2018 (has links)
Thesis (Master of Engineering in Electrical Engineering)--Cape Peninsula University of Technology, 2018. / As the electric energy demand grows, there is a significant increase in the penetration of renewable generation (RG) in the existing electrical grid network. Interconnecting of renewable generation technologies to an existing distribution system has proven to provide various benefits such as meeting the growing load demand and its contribution to energy system decarbonisation, long-term energy security and expansion of energy access to new energy consumers in the developing urban and rural areas. However, the aim of this thesis is to conduct a study on the impacts of renewable generation on the power quality of electrical grid. Therefore, this work aims at assessing the potential effects of Distributed Generation (DG) on the operation of electric power system by modelling of harmonics and voltage distortion. With different types of renewable generation available at present, it is believed that some designs contribute significantly to electrical network’s Power Quality (PQ). After the analysis of harmonic currents (chapter 6 and 7 of this thesis) introduced by renewable generation technologies, their negative impact on the power quality of the grid is seen to be apparent at point of connection (POC) but only within controlled limits. Analytical method for modeling of harmonic interactions between the grid and aggregated distributed generation technologies are investigated using DIgSILENT Power Factory software and the results obtained are discussed.
19

Technology Planning for Aligning Emerging Business Models and Regulatory Structures: the Case of Electric Vehicle Charging and the Smart Grid

Cowan, Kelly R. 07 December 2017 (has links)
Smart grid has been described as the Energy Internet: Where Energy Technology meets Information Technology. The incorporation of such technology into vast existing utility infrastructures offers many advantages, including possibilities for new smart appliances, energy management systems, better integration of renewable energy, value added services, and new business models, both for supply- and demand-side management. Smart grid also replaces aging utility technologies that are becoming increasingly unreliable, as the average ages for many critical components in utility systems now exceed their original design lives. However, while smart grid offers the promise of revolutionizing utility delivery systems, many questions remain about how such systems can be rolled out at the state, regional, and national levels. Many unique regulatory and market structure challenges exist, which makes it critical to pick the right technology for the right situation and to employ it in the right manner. Technology Roadmapping may be a valuable approach for helping to understand factors that could affect smart grid technology and product development, as well as key business, policy and regulatory drivers. As emerging smart grid technologies are developed and the fledgling industry matures, a critical issue will be understanding how the combination of industry drivers impact one another, what barriers exist to achieving the benefits of smart grid technologies, and how to prioritize R&D and acquisition efforts. Since the planning of power grids often relies on regional factors, it will also be important investigate linkages between smart grid deployment and regional planning goals. This can be used to develop strategies for overcoming barriers and achieving the benefits of this promising new technology. This research builds upon existing roadmapping processes by considering an integrated set of factors, including policy issues, which are specifically tuned to the needs of smart grids and have not generally been considered in other types of roadmapping efforts. It will also incorporate expert judgment quantification to prioritize factors, show the pathways for overcoming barriers and achieving benefits, and discussing the most promising strategies for achieving these goals.
20

Spectral Clustering for Electrical Phase Identification Using Advanced Metering Infrastructure Voltage Time Series

Blakely, Logan 23 January 2019 (has links)
The increasing demand for and prevalence of distributed energy resources (DER) such as solar power, electric vehicles, and energy storage, present a unique set of challenges for integration into a legacy power grid, and accurate models of the low-voltage distribution systems are critical for accurate simulations of DER. Accurate labeling of the phase connections for each customer in a utility model is one area of grid topology that is known to have errors and has implications for the safety, efficiency, and hosting capacity of a distribution system. This research presents a methodology for the phase identification of customers solely using the advanced metering infrastructure (AMI) voltage timeseries. This thesis proposes to use Spectral Clustering, combined with a sliding window ensemble method for utilizing a long-term, time-series dataset that includes missing data, to group customers within a lateral by phase. These clustering phase predictions validate over 90% of the existing phase labels in the model and identify customers where the current phase labels are incorrect in this model. Within this dataset, this methodology produces consistent, high-quality results, verified by validating the clustering phase predictions with the underlying topology of the system, as well as selected examples verified using satellite and street view images publicly available in Google Earth. Further analysis of the results of the Spectral Clustering predictions are also shown to not only validate and improve the phase labels in the utility model, but also show potential in the detection of other types of errors in the topology of the model such as errors in the labeling of connections between customers and transformers, unlabeled residential solar power, unlabeled transformers, and locating customers with incomplete information in the model. These results indicate excellent potential for further development of this methodology as a tool for validating and improving existing utility models of the low-voltage side of the distribution system.

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