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1
Sjolte, Jonas. „Marine renewable energy conversion : Grid and off-grid modeling, design and operation“. Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26004.
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The global energy production from renewable sources is increasing, with high penetration of both wind and solar in key regions. Ocean Wave Energy is projected to contribute with an increasing share of the future power supply, and the focus of this work is to investigate the requirements for connecting wave energy to the power grid, in context of the Fred. Olsen (FO) Wave Energy Project. Most Wave Energy Converters (WECs) produce highly distorted power due to the reciprocal motion induced by the ocean waves. Some WEC systems have integrated energy storage that overcomes this limitation, but adds significant expenses. As an alternative approach, this work investigates direct power export that relies on aggregate smoothing among several WECs. By optimizing the position of the WEC devices with respect to the incoming waves, fluctuations may be mutually canceled out between the devices. FO has closely monitored the global development within wave energy for about two decades, and has worked actively on developing WECs since 2002. The latest WEC system, named Lifesaver, has been in operation since April 2012 and is the basis of this thesis work. The Lifesaver system is described in detail, and comprehensive data on operational performance is presented. The major cost driver for grid integration is the peak to average power ratio, which can be as high as 20 in the early power conversion stages. Thus, it is crucial to improve the power quality early in the conversion chain so that the downstream power system is efficiently utilized. The simulations undertaken in this work indicate that a high quality power output can be achieved at the farm level, but that significant oversize factors will be required in the intermediate power systems within the farm. Cost-benefit analysis of the system show that a grid connected system at the current technology level will return marginal profitability. Therefore, several alternative approaches are investigated that could serve as a bridge towards future large scale systems. This includes autonomous systems that could supply power to remote ocean based units such as measurement and surveillance buoys, aquaculture facilities and support systems for the off-shore oil and gas industry. In general, the findings show that the WEC system is well suited for grid integration, although it becomes clear that significant development remains before wave energy can become an important supplement in the energy mix. Moreover, there seems to be a market for autonomous systems that is economically viable at the current technology level that could allow for immediate deployment of commercial systems.
2
Liu, Xin. „Scalable online simulation for modeling grid dynamics /“. Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3158471.
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3
Elyas, Seyyed Hamid 8045266. „Synthetic Modeling of Power Grids Based on Statistical Analysis“. VCU Scholars Compass, 2017. http://scholarscompass.vcu.edu/etd/4888.
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The development of new concepts and methods for improving the efficiency of power networks needs performance evaluation with realistic grid topology. However, much of the realistic grid data needed by researchers cannot be shared publicly due to the security and privacy challenges. With this in mind, power researchers studied statistical properties of power grids and introduced synthetic power grid topology as appropriate methodology to provide enough realistic power grid case studies. If the synthetic networks are truly representative and if the concepts or methods test well in this environment they would test well on any instance of such a network as the IEEE model systems or other existing grid models.
In the past, power researchers proposed a synthetic grid model, called RT-nested-smallworld, based on the findings from a comprehensive study of the topology properties of a number of realistic grids. This model can be used to produce a sufficiently large number of power grid test cases with scalable network size featuring the same kind of small-world topology and electrical characteristics found in realistic grids. However, in the proposed RT-nested-smallworld model the approaches to address some electrical and topological settings such as (1) bus types assignment, (2) generation and load settings, and (3) transmission line capacity assignments, are not sufficient enough to apply to realistic simulations. In fact, such drawbacks may possibly cause deviation in the grid settings therefore give misleading results in the following evaluation and analysis.
To address this challenges, the first part of this thesis proposes a statistical methodology to solve the bus type assignment problem. This method includes a novel measure, called the Bus Type Entropy, the derivation of scaling property, and the optimized search algorithm. The second part of this work includes a comprehensive study on generation/Load settings based on both topology metrics and electrical characteristics. In this section a set of approaches has been developed to generate a statistically correct random set of generation capacities and assign them to the generation buses in a grid. Then we determine the generation dispatch of each generation unit according to its capacity and the dispatch ratio statistics, which we collected and derived from a number of realistic grid test cases. The proposed approaches is readily applied to determining the load settings in a synthetic grid model and to studying the statistics of the flow distribution and to estimating the transmission constraint settings. Considering the results from the first two sections, the third part of this thesis will expand earlier works on the RT-nested-smallworld model and develop a new methodology to appropriately characterize the line capacity assignment and improve the synthetic power grid modeling.
4
Bürgler, Josef Franz. „Discretization and grid adaptation in semiconductor device modeling /“. [S.l.] : [s.n.], 1990. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=9146.
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5
Srivastava, Ravi K. „An Adaptive Grid Algorithm for Air Quality Modeling“. NCSU, 1998. http://www.lib.ncsu.edu/theses/available/etd-19980919-174712.
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SRIVASTAVA, RAVI K. An Adaptive Grid Algorithm for Air Quality Modeling. (Under the direction of Dr. D. Scott McRae.)The physical and chemical processes responsible for air pollution span a wide range of spatial scales. For example, there may be point sources, such as power plants that are characterized by relatively small spatial scales compared to the size of the region that may be impacted by such sources. To obtain accurate distributions of pollutants in an air quality simulation, the pertinent spatial scales can be resolved by varying the physical grid node spacing.A new dynamic adaptive grid algorithm, the Dynamic Solution Adaptive Grid Algorithm - PPM (DSAGA-PPM), is developed for use in air quality modeling. Given a fixed number of grid nodes, DSAGA-PPM distributes these nodes in response to spatial resolution requirements of the solution field and then updates the solution field based on the resulting distribution of nodes. DSAGA-PPM is implemented dynamically to resolve any evolving solution features. Tests with model problems demonstrate that DSAGA-PPM calculates advection much more accurately than the corresponding static grid algorithm (SGA-PPM) and, therefore, would assure more accurate starting concentrations for chemistry calculations. For example, after one revolution of four rotating cones, 87% of each of the cone peaks is retained using DSAGA-PPM while only 63% is retained using SGA-PPM. The root-mean-square errors in DSAGA-PPM results are about 4-5 times lower than those in the corresponding SGA-PPM results. Tests with reacting species and sources demonstrate that DSAGA-PPM provides the needed solution resolution. In simulations of a rotating and reacting conical puff, the root-mean-square errors in DSAGA-PPM results are about 4-6 times lower than those in the corresponding SGA-PPM results. In simulations of a power plant plume, the DSAGA-PPM solution reflects the early, the intermediate, and the mature stages of plume development; these stages are not seen in the corresponding SGA-PPM solution. Finally, it is demonstrated that DSAGA-PPM provides an accurate description of the ozone production resulting due to dynamic interactions between emissions from two power plants and an urban area. In general, these results reflect that DSAGA-PPM is able to provide accurate spatial and temporal resolution of rapidly changing and complex concentration fields. Performance achieved by DSAGA-PPM in model problem simulations indicates that it can provide accurate air quality modeling solutions at costs 10 times less than those incurred in obtaining equivalent static grid solutions.
6
Hayashi, Koichi 1967. „Variable grid finite-difference modeling including surface topography“. Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9367.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, September 1999."August 6, 1999."
Includes bibliographical references (leaves 188-190).
We have developed a two-dimensional viscoelastic finite-difference modeling method for highly complex surface topography and subsurface structures. Realistic modeling of seismic wave propagation in the near surface region is complicated by many factors, such as strong heterogeneity, topographic relief and large attenuation. In order to account for these complications, we use a velocity-stress staggered grid and employ an 0(2,4) accurate viscoelastic finite-difference scheme. The implementation includes an irregular free surface condition for topographic relief and a variable grid technique in the shallow parts of the model. Several methods of free surface condition are bench marked, and an accurate and simple condition is proposed. In the proposed free surface condition, stresses are calculated so that the shear and normal stresses perpendicular to the boundary are zero. The calculation of particle velocities does not involve any specific calculations, and the particle velocities are set to zero above the free surface. A stable variable grid method is introduced, where we use a three times finer grid in the near surface or low velocity region compared to the rest of the model. In order to reduce instability, we apply averaging or weighting to the replacement of the coarse grid components within the fine grid. The method allows us to avoid any limitation of the shape of the grid size boundary. Numerical tests indicate that approximately ten grid-points per shortest wavelength with the variable grid method results in accurate calculations. The method requires a stair-shaped discretization of a free surface. We investigated the stair-shaped structures, and found that the cause of the dispersion from irregular free surface is mainly a numerical error due to the large grid sizes rather than the Rayleigh waves scattering due to the stair-shaped boundary. The finite-difference modeling is applied to the investigation of near surface wave propagation. Several numerical simulations are performed to show the characters of wave propagation in the near surface region. The simulations show that the low velocity thin layers just below the surface and anelastic attenuation have significant effect on surface seismic record. The 2-D modeling of near surface structure beneath a 2-D refraction survey line is carried out. The comparison of the observed data with theoretical waveforms is performed. The characters in the observed data can be explained by a subsurface model constructed by P-wave traveltime tomography.
by Koichi Hayashi.
S.M.
7
Sankaran, Vaidyanathan. „Sub-grid Combustion Modeling for Compressible Two-Phase Flows“. Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/5274.
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A generic formulation for modeling the sub-grid combustion in
compressible, high Reynolds number, two-phase, reacting flows has
been developed and validated. A sub-grid mixing/combustion model
called Linear Eddy Mixing (LEM) model has been extended to
compressible flows and used inside the framework of Large Eddy
Simulation (LES) in this LES-LEM approach. The LES-LEM approach is
based on the proposition that the basic mechanistic distinction
between the convective and the molecular effects should be
preserved for accurate prediction of the complex flow-fields such
as those encountered in many combustion systems. In LES-LEM, all
the physical processes such as molecular diffusion, small and
large scale turbulent convection and chemical reaction are modeled
separately but concurrently at their respective time scales. This
multi-scale phenomena is solved using a two-scale numerical
approach, wherein molecular diffusion, small scale turbulent
convection and chemical reaction are grouped as small scale
processes and the convection at the (LES grid) resolved scales are
deemed as the large scale processes. Small-scale processes are
solved using a hybrid finite-difference Monte-carlo type approach
in a one-dimensional domain. Large-scale advection on the
three-dimensional LES grid is modeled in a Lagrangian manner that
conserves mass.
Liquid droplets (represented by computational parcels) are tracked
using the Lagrangian approach wherein the Newton's equation of
motion for the discrete particles are integrated explicitly in the
Eulerian gas field.
Drag effects due to the droplets on the gas phase and the heat
transfer between the gas and the liquid phase are explicitly
included. Thus, full coupling is achieved between the two phases
in the simulation.
Validation of the compressible LES-LEM approach is conducted by
simulating the flow-field in an operational General Electric
Power Systems' combustor (LM6000). The results predicted using
the proposed approach compares well with the experiments and a
conventional (G-equation) thin-flame model.
Particle tracking algorithms used in the present study are
validated by simulating droplet laden temporal mixing layers.
Comparison of the energy growth in the fundamental and
sub-harmonic mode in the presence and absence of the droplets
shows excellent agreement with spectral DNS.
Finally, to test the ability of the present two-phase LES-LEM in
simulating partially premixed combustion, a LES of freely
propagating partially premixed flame in a droplet-laden isotropic
turbulent field is conducted. LES-LEM along with the spray models
correctly captures the flame structure in the partially premixed
flames. It was found that most of the fuel droplets completely
vaporize before reaching the flame, and hence provides a
continuous supply of reactants, which results in an intense
reaction zone similar to a premixed flame. Some of the droplets
that did not evaporate completely, traverse through the flame and
vaporize suddenly in the post flame zone. Due to the strong
spatial variation of equivalence ratio a broad flame similar to a
premixed flame is realized. Triple flame structure are also
observed in the flow-field due to the equivalence ratio
fluctuations.
8
Miller, Daniel K. „Wire grid modeling of the Linearly Tapered Slot Antenna“. Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/26339.
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9
Ilves, Kalle. „Modeling and Design of Modular MultilevelConverters for Grid Applications“. Licentiate thesis, KTH, Elektrisk energiomvandling, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-105779.
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Grid-connected high-power converters are found in high-voltage direct current transmission (HVDC), static compensators (STATCOMs), and supplies for electric railways. Such power converters should have a high reliability, high efficiency, good harmonic performance, low cost, and a small footprint. Cascaded converters are promising solutions for high-voltage high-power converters since they allow the combination of excellent harmonic performance and low switching frequencies. A high reliability can also be achieved by including redundant submodules in the chain of cascaded converters. One of the emerging cascaded converter topologies is the modular multilevel converter (M2C). This thesis aims to bring clarity to the dimensioning aspects and limiting factors of M2Cs. The dc-capacitor in each submodule is a driving factor for the size and weight of the converter. It is found that the voltage variations across the submodule capacitors will distort the voltage waveforms and also induce alternating components in the current that is circulating between the phase-legs. It is, however, shown that it is possible to control the alternating voltage by feed-forward control. It is also shown that if the circulating current is controlled, the injection of a second-order harmonic component can extend the operating region of the converter. The reason for this is that when the converter is operating close to the boundary of overmodulation the phase and amplitude of the second-order harmonic is chosen such that the capacitors are charged prior to the time when a high voltage should be inserted by the submodules. The controller that is used must be able to balance the sbmodule capacitor voltages. Typically, an increased switching frequency will enhance the performance of the balancing control scheme. In this thesis it is shown that the capacitor voltages can be balanced with programmed modulation, even if fundamental switching frequency is used. This will, however, increase the voltage ripple across the aforementioned capacitors. In order to quantify the requirements on the dc-capacitors a general analysis is provided in this thesis which is based on the assumption that the capacitor voltages are well balanced. It is found that for active power transfer, with a 50 Hz sinusoidal voltage reference, the capacitors must be rated for a combined energy storage of 21 kJ/MW if the capacitor voltages are allowed to increase by 10% above their nominal values.QC 20121127
10
Stergiadis, Dimitris. „Persona modeling by crowdsourcing using the repertory grid technique“. Thesis, Linköpings universitet, Institutionen för datavetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-140916.
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Within user modeling there are various methods for representing targeted users. Persona for example is a user archetype which is given a face and name, and is carefully described in terms of goals, needs, and tasks (Blomquist & Arvola, 2002). Personas are widely used, but have been criticized for often not being based on empirical data (McGinn & Kotamraju, 2008). In this thesis I explore the use of the Repertory grid technique (RGT) in a user modeling context, an approach deriving from George Kelly’s (1955) Personal construct theory, which elicits both idiographic (i.e. the subjective dimensions of one individual) and nomothetic (i.e. a populations behaviours and traits) empirical data from individuals by analysing both qualitative and quantitative data. Furthermore, the possibilities and difficulties that the RGT offers in the context of user modeling are investigated. An online survey is crowdsourced (n = 28) containing five vignettes which are based on structured interviews and are used to elicit the participant’s personal constructs. The results are presented in the form of bertin plots and a biplot along with the Importance (the order of a constructs elicitation), and Dominance (the relative elicitation percentage of a construct) measures. The results suggest that the technique employed could be used in a number of user modelling processes. The weaknesses of RGT when done remotely in a user modelling context are also discussed.
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Gross, Matthew Edward. „Discrete fracture modeling for fractured reservoirs using Voronoi grid blocks“. Texas A&M University, 2003. http://hdl.handle.net/1969.1/5777.
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Fractured reservoirs are commonly simulated using the Dual Porosity model, but
for many major fields, the model does not match field results. For these cases, it is
necessary to perform a more complex simulation including either individual fractures or
pseudofracture groups modeled in their own grid blocks.
Discrete Fracture Modeling (DFN) is still a relatively new field, and most
research on it up to this point has been done with Delaunay tessellations. This research
investigates an alternative approach using Voronoi diagrams, yet applying the same
DFN principles outlined in previous works.
Through the careful positioning of node points, a grid of Voronoi polygons can
be produced so that block boundaries fall along the fractures, allowing us to use the DFN
simulation methods as proposed in the literature. Using Voronoi diagrams allows us to
use far fewer polygons than the Delaunay approach, and also allows us to perfectly align
flow so as to eliminate grid alignment errors that plagued previous static systems. The
nature of the Voronoi polygon further allows us to simplify permeability calculations
due to orthogonality and, by extension, is more accurate than the commonly used cornerpoint
formulation for non-square grid blocks.
12
Plikas, Atanasis. „Numerical modeling of fibre suspensions in grid-generated turbulent flow“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0023/MQ50361.pdf.
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Ilves, Kalle. „Modeling and Design of Modular Multilevel Converters for Grid Applications“. Doctoral thesis, KTH, Elektrisk energiomvandling, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-153762.
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This thesis aims to bring clarity to the dimensioning aspects and limiting factors of the modular multilevel converter (MMC). Special consideration is given to the dc capacitors in the submodules as they are a driving factor for the size and weight of the converter. It is found that if the capacitor voltages are allowed to increase by 10% the stored energy must be 21 kJ/MW in order to compensate the capacitor voltage ripple. The maximum possible output power can, however, be increased by injecting a second-order harmonic in the circulating current. A great advantage of cascaded converters is the possibility to achieve excellent harmonic performance at low switching frequencies. Therefore, this thesis also considers the relation between switching harmonics, capacitor voltage ripple, and arm quantities. It is shown that despite subharmonics in the capacitor voltages, it is still possible to achieve periodic arm quantities. The balancing of the capacitor voltages is also considered in further detail. It is found that it is possible to balance the capacitor voltages even at fundamental switching frequency although this will lead to a comparably large capacitor voltage ripple. Therefore, in order to limit the peak-to-peak voltage ripple, it is shown that a predictive algorithm can be used in which the resulting switching frequency is approximately 2–3 times the fundamental frequency. This thesis also presents two new submodule concepts. The first submodule simply improves the trade-off between the switching frequency and capacitor voltage balancing. The second submodule includes the possibility to insert negative voltages which allows higher modulation indices compared to half-bridge submodules. A brief comparison of cascaded converters for ac-ac applications is also presented. It is concluded that the MMC appears to be well suited for ac-ac applications where input and output frequencies are close or equal, such as in interconnection of ac grids. In low-frequency applications such as low-speed drives, however, the difficulties with handling the energy variations in the converter arms are much more severe in the MMC compared to the other considered topologies.QC 20141010
14
Vasudevan, Sneha. „One-Step-Ahead Load Forecasting for Smart Grid Applications“. The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1323312608.
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15
Mansouri, Seyed Akbar. „Circuit Topology Study of Grid-Connected Photovoltaic System“. The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1308328627.
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Podber, David P. „Modeling strongly stratified flow using the dynamic grid adaptation (DGA) technique /“. The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487946776024051.
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Foshee, Jacob Wesley. „Resolution independent curved seams in clothing animation using a regular particle grid“. Texas A&M University, 2004. http://hdl.handle.net/1969.1/1226.
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We present a method for representing seams in clothing animation, and its application
in simulation level of detail. Specifically we consider cloth represented as a regular
grid of particles connected by spring-dampers, and a seam specified by a closed set
of parametric trim curves in the cloth domain.
Conventional cloth animation requires the tessellation of seams so that they are
handled uniformly by the dynamics process. Our goal is a seam definition which
does not constrain the attached clothing panels to be of the same resolution, or even
constant resolution, while not being a hindrance to the dynamics process. We also
apply our seams to cloth defined on a regular grid, as opposed to the irregular meshes
commonly used with seams.
The determination of particles interior to the cloth panel can be done using wellknown
graphics operations such as scan-conversion. Due to the particle-based nature
of the simulation, the dynamics approach combines easily with existing implicit and
explicit methods.
Finally, because the seams are resolution independent, the particle density per
clothing panel can be adjusted as desired. This gives rise to a simple application
of the given seams approach illustrating how it may be used for simulation level of
detail.
18
Howard, Dustin F. „Modeling, simulation, and analysis of grid connected dish-stirling solar power plants“. Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34832.
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The percentage of renewable energy within the global electric power generation portfolio is expected to increase rapidly over the next few decades due to increasing concerns about climate change, fossil fuel costs, and energy security. Solar thermal energy, also known as concentrating solar power (CSP), is emerging as an important solution to new demands for clean, renewable electricity generation. Dish-Stirling (DS) technology, a form of CSP, is a relatively new player in the renewable energy market, although research in the technology has been ongoing now for nearly thirty years. The first large plant utilizing DS technology, rated at 1.5 MW, came online in January 2010 in Peoria, AZ, and plants rated for several hundred MW are in the planning stages. Increasing capacity of this technology within the utility grid requires extensive dynamic simulation studies to ensure that the power system maintains its safety and reliability in spite of the technological challenges that DS technology presents, particularly related to the intermittency of the energy source and its use of a non-conventional asynchronous generator. The research presented in this thesis attempts to fill in the gaps between the well established research on Stirling engines in the world of thermodynamics and the use of DS systems in electric power system applications, a topic which has received scant attention in publications since the emergence of this technology.
DS technology uses a paraboloidal shaped dish of mirrors to concentrate sunlight to a single point. The high temperatures achieved at the focal point of the mirrors is used as a heat source for the Stirling engine, which is a closed-cycle, external heat engine. Invented by the Scottish clergyman Robert Stirling in 1816, the Stirling engine is capable of high efficiency and releases no emissions, making it highly compatible with concentrated solar energy. The Stirling engine turns a squirrel-cage induction generator, where electricity is delivered through underground cables from thousands of independent, autonomous 10-25 kW rated DS units in a large solar farm.
A dynamic model of the DS system is presented in this thesis, including models of the Stirling engine working gas and mechanical dynamics. Custom FORTRAN code is written to model the Stirling engine dynamics within PSCAD/EMTDC. The Stirling engine and various other components of the DS system are incorporated into an electrical network, including first a single-machine, infinite bus network, and then a larger 12-bus network including conventional generators, loads, and transmission lines. An analysis of the DS control systems is presented, and simulation results are provided to demonstrate the system's steady state and dynamic behavior within these electric power networks. Potential grid interconnection requirements are discussed, including issues with power factor correction and low voltage ride-through, and simulation results are provided to illustrate the dish-Stirling system's capability for meeting such requirements.
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Mataifa, Haltor. „Modeling and control of a dual-mode grid-integrated renewable energy system“. Thesis, Cape Peninsula University of Technology, 2015. http://hdl.handle.net/20.500.11838/2190.
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Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2015.From the electric power generation perspective, the last three decades have been characterized by sustained growth in the amount of Distributed Power Generation (DPG) systems integrated into the electric grid. This trend is anticipated to continue, especially in light of the widespread acceptance of the many benefits envisaged in the increase of renewable-based power generation. The potential for grid-integrated DPG systems to significantly contribute to electric power supply reliability has consistently attracted extensive research in recent times, although concerns continue to be raised over their adverse impact on the normal grid operation at high penetration levels. These concerns largely stem from the limited controllability of most DPG systems, which tend to exhibit large output impedance variation, and non-deterministic power output characteristics. There has therefore also been a growing need to develop effective control strategies that can enhance the overall impact of the DPG systems on the grid operation, thus improving their synergistic properties, and probably also enabling an even higher penetration level into the utility grid. In line with this identified need, this thesis discusses the modeling and controller design for an inverter-based DPG system with the capability to effectively operate both in grid-connected and autonomous (i.e. independent of the utility grid) operational modes. The dual-mode operation of the DPG is made possible by incorporating into the inverter interface control scheme the means to ensure seamless transition of the DPG between the grid-connected and autonomous modes of operation. The intention is to have a grid-integrated inverter-based DPG system whose operation approximates that of an online Uninterruptible Power Supply (UPS) system, in that it is able to sustain power supply to the local load in the absence of the grid supply, which would be desirable for critical loads, for which the level of power supply reliability guaranteed by the grid often falls short of the requirements. The work developed in this thesis considers three of the aspects associated with grid-integrated DPG systems that are equipped with autonomous-mode operation capability.
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Johnson, Benjamin Anders. „Modeling and Analysis of a PV Grid-Tied Smart Inverter's Support Functions“. DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/994.
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The general trends in the past decade of increasing solar cell efficiency, decreasing PV system costs, increasing government incentive programs, and several other factors have all combined synergistically to reduce the barriers of entry for PV systems to enter the market and expand their contribution to the global energy portfolio. The shortcomings of current inverter functions which link PV systems to the utility network are becoming transparent as PV penetration levels continue to increase. The solution this thesis proposes is an approach to control the inverters real and reactive power output to help eliminate the problems associated with PV systems at their origin and in addition provide the grid with ancillary support services. The design, modeling, and analysis of a grid-tied PV system was performed in the PSCAD software simulation environment. Results indicate that in the presence of grid disturbances the smart inverter can react dynamically to help restore the power system back to its normal state. A harmonic analysis was also performed indicating the inverter under study met the applicable power quality standards for distributed energy resources.
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Baduel, Laurent. „Typed Groups for the Grid“. Phd thesis, Université de Nice Sophia-Antipolis, 2005. http://tel.archives-ouvertes.fr/tel-00009757.
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La communication de groupe est un dispositif crucial pour le calcul haute performance notamment sur les grilles de calculs. Tandis que les bibliothèques issues des travaux antérieurs imposent des contraintes spécifiques aux programmeurs (par exemple l'utilisation d'interfaces consacrées) pour effectuer des communications de groupes, cette thèse présente un mécanisme qui se veut plus flexible. En particulier, nous proposons un modèle, où, étant donnée une classe Java, les communications de groupes sont déclanchées par appel aux méthodes publiques de la classe en conservant la notation pointée; de cette façon les communications et les groupes deviennent typés. De plus, des groupes sont automatiquement construits pour collecter les résultats d'une opération collective. Ce système est basé sur un Protocole à Méta-Objets. Cela permet une notation objet et une gestion dynamique des résultats (ex: B groupB = groupA.foo();). Cette flexibilité permet également de gérer les résultats qui sont eux mêmes des groupes d'objets accessibles à distance, et d'utiliser un groupe comme paramètre d'appel de méthode pour que ses membres soient distribués entre les membres d'un groupe d'appel. De plus, des groupes hiérarchiques peuvent être facilement et dynamiquement construits : une importante fonctionnalité de déploiement dans un contexte de grilles. Des mesures de performances et une application numérique démontrent la viabilité de l'approche. Nos derniers travaux mènent à un style de programmation SPMD (Single Program Multiple Data) orienté-objet basé sur les communications de groupes typés et qui permet un contrôle étendu sur des applications de calculs intensifs tout en préservant les bénéfices d'une approche typée. Les groupes d'objets soutenant le calcul distribué sont organisés selon une topologie, c'est à dire l'ajout de la notion d'une identification pour chaque membre dans le groupe SPMD et la possibilité de référencer facilement ses voisins. Les opérations collectives ont été revisitées et étendues par des barrières de synchronisation de façon à fournir un modèle complet de programmation SPMD orienté-objet.
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Dimble, Dipesh S. „Geometry modeling for patterned and repetitive configurations“. Birmingham, Ala. : University of Alabama at Birmingham, 2006. http://www.mhsl.uab.edu/dt/2007m/dimble.pdf.
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Kurzbach, Stefan [Verfasser], und Ralf [Akademischer Betreuer] Möller. „Flood modeling in spatial data and grid infrastructures / Stefan Kurzbach. Betreuer: Ralf Möller“. Hamburg-Harburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2014. http://d-nb.info/1053704275/34.
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Marshall, David D. „Extending the functionalities of Cartesian grid solvers : viscous effects modeling and MPI parallelization“. Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/11999.
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Rehman, Attiqa [Verfasser]. „Workload Modeling and Prediction for Workflow Scheduling in Dynamic Grid Environments / Attiqa Rehman“. Hagen : Fernuniversität Hagen, 2014. http://d-nb.info/104711464X/34.
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Akkinapragada, Nagasmitha. „Dynamic modeling and simulations of solid oxide fuel cells for grid-tied applications“. Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.umr.edu/thesis/pdf/final_copy1_09007dcc8031997c.pdf.
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Thesis (M.S.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 17, 2007) Includes bibliographical references (p. 77-80).
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Wu, Diyun, und 伍迪芸. „Modeling, analysis and coordination of electric vehicles integrating into the electric power grid“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/197122.
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In recent years, since the concept of smart grid rises and the existing power grids are continuously modernized, more and more electric vehicles (EVs) are integrated into the power grid. In the power grid, EVs are expected to provide various energy services, such as spinning reserves, regulation services, optimization services, stability improvement, reactive compensation and grid security. This thesis is to model, analyze and implement these energy services of EVs.
Firstly, a multilayer framework of a power system with vehicle-to-grid (V2G) and vehicle-to-vehicle (V2V) operation is proposed. Its fundamental components including batteries, renewable energy sources are modeled for system analysis. Moreover, a general model for multiply purposes is presented.
Secondly, based on the modeling of EVs and the power systems, the analysis on frequency regulation and transient stability of the V2G system can be carried out effectively. The objectives of the frequency regulation are to keep the system frequency constant, and eliminate the deviations fast and effectively. While, the transient stability is to observe the performances of the power systems integrated with EVs and superconducting magnetic energy storage (SMES) during emergency cases. The results illustrate that EVs are valuable for improve the frequency and transient stability of the power systems.
Finally, the coordination and optimization of the power systems with EVs are studied. Unit commitment involving EVs is analyzed, which uses EVs to replace some expensive generating units to achieve minimum operating cost and emissions. In addition, the optimal sizing of EV aggregations in the distribution power system is conducted to minimize the total power loss. And the individual EV in the aggregations is dispatched to achieve minimum charging cost by satisfying the optimal sized demand and the real-time pricing. The results verified that EVs can be used to achieve optimized goals, such as minimum costs, emissions and losses.published_or_final_version
Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy
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Bailey, Jermaine A. „UNIFORM AND MULTI-GRID MODELING OF ACOUSTIC WAVE PROPAGATION WITH CELLULAR AUTOMATON TECHNIQUES“. Monterey, California. Naval Postgraduate School, 2013. http://hdl.handle.net/10945/32789.
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The Cellular Automaton (CA) method is an alternative computational technique used in understanding the behavioral response of dynamic systems. It allows great flexibility in the application of various types of boundary conditions. As such, this method is used in developing an alternative propagation model for ocean acoustics. The modeling scheme creates a profile of propagation losses versus range, in an acoustic medium. Moreover, the chosen complex boundary conditions, which are not easily modeled by ordinary numerical techniques, are shown to perform with remarkable ease with CA methods. Accordingly, like any other modeling method, the computational time increases when a refined solution is desired. As such, an alternative multi-grid modeling scheme is shown to increase the performance time of the CA method significantly. This improvement is dependent upon the total number of global grid points inside the multi-grid domain. The end result show a multi-grid, with fewer nodal points, producing accurate results that replicate a uniform grid, which utilizes a larger quantity of nodal points.
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Gokarapu, Ramu. „Determination of Harmonics for Modeling Integration of Solar Generation to The Electric Grid“. ScholarWorks@UNO, 2011. http://scholarworks.uno.edu/td/1312.
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The purpose of this study is to determine a model for analysis of integrating solar generation to the electric grid .The model is then used in determining Harmonics of Integrating solar panels to the electric grid that are based on parallel or series combination of solar cells. To study integration of solar generation to the grid, we have used solar series and solar parallel models in EMTP (Electro Magnetic Transient Program) real time simulation software. When integrating solar generation models to the grid, due to DC to AC conversion and due to variation of solar energy intensity, the electric utility shall experience undesired harmonics that may impact quality of service to other customers in the grid. This study identifies one method of analysis for determining harmonic content of solar panels before solar generation can be integrated in to the electric grid.
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Foskolos, Georgios. „Current harmonic modeling of aggregated electric vehicle loads in the low voltage grid“. Licentiate thesis, Mälardalens högskola, Framtidens energi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-53169.
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The proliferation of Electric Vehicles (EVs) poses new challenges for the Distribution System Operator (DSO). For example, the rectifiers that are used for charging EV batteries could significantly influence Power Quality (PQ), in terms of harmonic distortion. The emissions from individual EV, are well regulated by current harmonic emission standards. But what the aggregation of multiple EV loads will look like is still uncertain and the research being made in this area is still in its early stage. The DSO responsibilities include ensuring grid code compliance confirmed by PQ metering. In general, 10 minute RMS values are sufficient. However, the large scale integration of non-linear loads, like EVs, could lead to new dynamic phenomena, possibly lost in the process of time aggregation. In this thesis PQ and, in more detail, the concept of harmonics, and how this is related to EVs, is presented. A current-harmonic load model using power exponential functions and built from actual measurement data during the individual charging of four different fully electric vehicles was constructed. The model was based on individual emitted current harmonics as a function of state of charge (SOC), and was used to deterministically simulate the simultaneous charging of six vehicles fed from the same bus. The aggregation of current harmonics up to the 11th was simulated while randomizing battery SOC, the start of charging, and the kind of vehicle. Additionally, an investigation of the impact on aggregation in time was conducted. The analysis clearly shows the importance of phase angle information, its correlation to SOC, and how the aggregation of EV loads is influenced by these factors. The analysis also shows that 10 minute RMS aggregation could lead to significant deviations from the “actual” (200ms) data. This indicates that 10 minute value monitoring could lead to information losses.
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Tee, Chin Yen. „Market Design for the Future Electricity Grid: Modeling Tools and Investment Case Studies“. Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/856.
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The future electricity grid is likely to be increasingly complex and uncertain due to the introduction of new technologies in the grid, the increased use of control and communication infrastructure, and the uncertain political climate. In recent years, the transactive energy market framework has emerged as the key framework for future electricity market design in the electricity grid. However, most of the work done in this area has focused on developing retail level transactive energy markets. There seems to be an underlying assumption that wholesale electricity markets are ready to support any retail market design. In this dissertation, we focus on designing wholesale electricity markets that can better support transactive retail market. On the highest level, this dissertation contributes towards developing tools and models for future electricity market designs. A particular focus is placed on the relationship between wholesale markets and investment planning. Part I of this dissertation uses relatively simple models and case studies to evaluate key impediments to flexible transmission operation. In doing so, we identify several potential areas of concern in wholesale market designs: 1. There is a lack of consideration of demand flexibility both in the long-run and in the short-run 2. There is a disconnect between operational practices and investment planning 3. There is a need to rethink forward markets to better manage resource adequacy under long-term uncertainties 4. There is a need for more robust modeling tools for wholesale market design In Part II and Part III of this dissertation, we make use of mathematical decomposition and agent-based simulations to tackle these concerns. Part II of this dissertation uses Benders Decomposition and Lagrangian Decomposition to spatially and temporally decompose a power system and operation problem with active participation of flexible loads. In doing so, we are able to not only improve the computational efficiency of the problem, but also gain various insights on market structure and pricing. In particular, the decomposition suggests the need for a coordinated investment market and forward energy market to bridge the disconnect between operational practices and investment planning. Part III of this dissertation combines agent-based modeling with state-machine based modeling to test various spot, forward, and investment market designs, including the coordinated investment market and forward energy market proposed in Part II of this dissertation. In addition, we test a forward energy market design where 75% of load is required to be purchased in a 2-year-ahead forward market and various transmission cost recovery strategies. We demonstrate how the different market designs result in different investment decisions, winners, and losers. The market insights lead to further policy recommendations and open questions. Overall, this dissertation takes initial steps towards demonstrating how mathematical decomposition and agent-based simulations can be used as part of a larger market design toolbox to gain insights into different market designs and rules for the future electricity grid. In addition, this dissertation identifies market design ideas for further studies, particularly in the design of forward markets and investment cost recovery mechanisms.
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Shepero, Mahmoud. „Modeling and forecasting the load in the future electricity grid : Spatial electric vehicle load modeling and residential load forecasting“. Licentiate thesis, Uppsala universitet, Fasta tillståndets fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-359432.
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The energy system is being transitioned to increase sustainability. This transition has been accelerated by the increased awareness about the adverse effects of the greenhouse gas (GHG) emissions into the atmosphere. The transition includes switching to electricity as the energy carrier in some sectors, e.g., transportation, increasing the contribution of renewable energy sources (RES) to the grid, and digitalizing the grid services. Electric vehicles (EVs) are promoted and subsidized in many countries among the sustainability initiatives. Consequently, the global sales of EVs rapidly increased in the recent years. Many EV owners might charge their EVs only at home, thereby increasing the residential load. The residential load might further increase due to the initiatives to electrify the heating/cooling sector. This thesis contributes to the knowledge about the operation of the future energy system by modeling the spatial charging load of private EVs in cities, and by proposing a forecasting model to predict the residential load. Both models can be used to evaluate the impacts of both technologies on the local electricity grid. In addition, demand response (DR) schemes can be proposed to reduce the adverse effects of both the charging load of EVs and the residential load. A case study of the EV model on the Herrljunga city grid showed that 100% EV penetration with 3.7 kW (charging rate of 14.8 km/h) chargers will not cause voltage violations in the grid. Winter load is responsible for 5% voltage drop at the weakest bus, and EVs add only 1% to this drop. In a Swedish city, charging EVs will require adding extra 1.43 kW/car to the grid capacity—assuming 22 kW (charging rate of 88 km/h) residential chargers. If the EV charging is not restricted to residential locations, an increase of 1.23 kW/car is expected. The proposed forecasting model is comparable in accuracy to previously developed models. As an advantage, the model produces a probability density function (PDF) describing the model’s certainty in the forecast. In contrast, many previous contributions provided only point forecasts.
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Mengistu, Dawit. „Multi-Agent Based Simulations in the Grid Environment“. Licentiate thesis, Karlskrona : Blekinge Institute of Technology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-00371.
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The computational Grid has become an important infrastructure as an execution environment for scientific applications that require large amount of computing resources. Applications which would otherwise be unmanageable or take a prohibitively longer execution time under previous computing paradigms can now be executed efficiently on the Grid within a reasonable time. Multi-agent based simulation (MABS) is a methodology used to study and understand the dynamics of real world phenomena in domains involving interaction and/or cooperative problem solving where the participants are characterized by entities having autonomous and social behaviour. For certain domains the size of the simulation is extremely large, intractable without employing adequate computing resources such as the Grid. Although the Grid has come with immense opportunities to resource demanding applications such as MABS, it has also brought with it a number of challenges related to performance. Performance problems may have their origins either on the side of the computing infrastructure or the application itself, or both. This thesis aims at improving the performance of MABS applications by overcoming problems inherent to the behaviour of MABS applications. It also studies the extent to which the MABS technologies have been exploited in the field of simulation and find ways to adapt existing technologies for the Grid. It investigates performance monitoring and prediction systems in the Grid environment and their implementation for MABS application with the purpose of identifying application related performance problems and their solutions. Our research shows that large-scale MABS applications have not been implemented despite the fact that many problem domains that cannot be studied properly with only partial simulation. We assume that this is due to the lack of appropriate tools such as MABS platforms for the Grid. Another important finding of this work is the improvement of application performance through the use of MABS specific middleware.
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Ambarkutuk, Murat. „A Grid based Indoor Radiolocation Technique Based on Spatially Coherent Path Loss Model“. Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/80405.
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This thesis presents a grid-based indoor radiolocation technique based on a Spatially Coherent Path Loss Model (SCPL). SCPL is a path loss model which characterizes the radio wave propagation in an environment by solely using Received Signal Strength (RSS) fingerprints. The propagation of the radio waves is characterized by uniformly dividing the environment into grid cells, followed by the estimation of the propagation parameters for each grid cell individually. By using SCPL and RSS fingerprints acquired at an unknown location, the distance between an agent and all the access point in an indoor environment can be determined. A least-squares based trilateration is then used as the global fix of location the agent in the environment. The result of the trilateration is then represented in a probability distribution function over the grid cells induced by SCPL. Since the proposed technique is able to locally model the propagation accounting for attenuation of non-uniform environmental irregularities, the characterization of the path loss in the indoor environment and radiolocation technique might yield improved results. The efficacy of the proposed technique was investigated with an experiment comparing SCPL and an indoor radiolocation technique based on a conventional path loss model.Master of Science
This thesis presents a technique uses radio waves to localize an agent in an indoor environment. By characterizing the difference between transmitted and received power of the radio waves, the agent can determine how far it is away from the transmitting antennas, i.e. access points, placed in the environment. Since the power difference mainly results from obstructions in the environment, the attenuation profile of the environment carries a significant importance in radiolocation techniques. The proposed technique, called Spatially Coherent Path Loss Model (SCPL), characterizes the radio wave propagation, i.e. the attenuation, separately for different regions of the environment, unlike the conventional techniques employing global attenuation profiles. The localization environment is represented with grid-cell structure and the parameters of SCPL model describing the extent of the attenuation of the environment are estimated individually. After creating an attenuation profile of the environment, the agent localizes itself in the localization environment by using SCPL with signal powers received from the access points. This scheme of attenuation profiling constitutes the main contribution of the proposed technique. The efficacy and validity of the proposed technique was investigated with an experiment comparing SCPL and an indoor radiolocation technique based on a conventional path loss model.
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Frogley, David C. „Fast Relabeling of Deformable Delaunay Tetrahedral Meshes Using a Compact Uniform Grid“. BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2738.
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We address the problem of fast relabeling of deformable Delaunay tetrahedral meshes using a compact uniform grid, with CPU parallelization through OpenMP. This problem is important in visualizing the simulation of deformable objects and arises in scientific visualization, games, computer vision, and motion picture production. Many existing software tools and APIs have the ability to manipulate 3D virtual objects. Prior mesh-based representations either allow topology changes or are fast. We aim for both. Specifically, we improve the efficiency of the relabeling step in the Delaunay deformable mesh invented by Pons and Boissonnat and improved by Tychonievich and Jones. The relabeling step assigns material types to deformed meshes and accounts for 70% of the computation time of Tychonievich and Jones' algorithm. We have designed a deformable mesh algorithm using a Delaunay triangulation and a compact uniform grid with CPU parallelization to obtain greater speed than other methods that support topology changes. On average, over all our experiments and with various 3D objects, the serial implementation of the relabeling step of our work reports a speedup of 2.145 over the previous fastest method, including one outlier whose speedup was 3.934. When running in parallel on 4 cores, on average the relabeling step of our work achieves a speedup of 3.979, with an outlier at 7.63. The average speedup of our parallel relabeling step over our own serial relabeling step is 1.841.Simulation results show that the resulting mesh supports topology changes.
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Oral, Hakki Sarp. „Performance modeling and analysis of multicast infrastructure for high-speed cluster and Grid networks“. [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0002422.
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Antonelli, Jacopo. „Reduced order modeling of wind turbines in MatLab for grid integration and control studies“. Thesis, Högskolan på Gotland, Institutionen för kultur, energi och miljö, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hgo:diva-1865.
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The current trend in the wind power industry is to develop wind turbines of constantly increasing size and rated power, as well as wind farms of growing size and installed wind power. A careful study of the behaviour of the wind turbines during their operation is of crucial importance in the planning phase and in the design stage of a wind farm, in order to minimize the risks deriving from a non accurate prediction of their impact in the electric grid causing sensible faults of the system. To analyze the impact of the wind turbines in the system, motivates the development of accurate yet simple models. To be able to practically deal with this topics, a simple model of a wind turbine system is investigated and developed; it has the aim to describe the behaviour of a wind turbine in operation on a mechanical standpoint. The same reduced order simple model can also be employed for control system studies; the control system model that can’t be used in generation, can use the reduced model. Together with the analytical description of such model, is realized a MatLab code to numerically analyse the response of the system, and the results of the simulation through such code are presented. The objective of this thesis has been to provide a simple benchmark tool in MatLab for grid integration and control studies for interested researchers.
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Zahid, Zaka Ullah. „Design, Modeling and Control of Bidirectional Resonant Converter for Vehicle-to-Grid (V2G) Applications“. Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/77686.
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Electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) are gaining popularity because they are more environmentally friendly, less noisy and more efficient. These vehicles have batteries can be charged by on-board battery chargers that can be conductive or inductive. In conductive chargers, the charger is physically connected to the grid by a connector. With the inductive chargers, energy can be transferred wirelessly over a large air-gap through inductive coupling, eliminating the physical connection between the charger and the grid. A typical on-board battery charger consists of a boost power factor correction (PFC) converter followed by a dc-dc converter. This dissertation focuses on the design, modeling and control of a bidirectional dc-dc converter for conductive battery charging application.
In this dissertation, a detailed design procedure is presented for a bidirectional CLLLC-type resonant converter for a battery charging application. This converter is similar to an LLC-type resonant converter with an extra inductor and capacitor in the secondary side. Soft-switching can be ensured in all switches without additional snubber or clamp circuitry. Because of soft-switching in all switches, very high-frequency operation is possible, thus the size of the magnetics and the filter capacitors can be made small. To further reduce the size and cost of the converter, a CLLC-type resonant network with fewer magnetics is derived from the original CLLLC-type resonant network. First, an equivalent model for the bidirectional converter is derived for the steady-state analysis. Then, the design methodology is presented for the CLLLC-type resonant converter. Design of this converter includes determining the transformer turns ratio, design of the magnetizing inductance based on ZVS condition, design of the resonant inductances and capacitances. Then, the CLLC-type resonant network is derived from the CLLLC-type resonant network. To validate the proposed design procedure, a 3.5 kW converter was designed following the guidelines in the proposed methodology. A prototype was built and tested in the lab. Experimental results verified the design procedure presented.
The dynamics analysis of any converter is necessary to design the control loop. The bandwidth, phase margin and gain margin of the control loops should be properly designed to guarantee a robust system. The dynamic analysis of the resonant converters have not been extensively studied, with the previous work mainly concentrated on the steady-state models. In this dissertation, the continuous-time large-signal model, the steady-state operating point, and the small-signal model are derived in an analytical closed-form. This model includes both the frequency and the phase-shift control. Simulation and experimental verification of the derived models are presented to validate the presented analysis.
A detailed controller design methodology is proposed in this dissertation for the bidirectional CLLLC-type resonant converter for battery charging application. The dynamic characteristics of this converter change significantly as the battery charges or discharges. And, at some operating points, there is a high-Q resonant peaking in the open-loop bode-plot for any transfer functions in this converter. So, if the controller is not properly designed, the closed-loop system might become unstable at some operating points. In this paper, a controller design methodology is proposed that will guarantee a stable operation during the entire operating frequency range in both battery charging mode (BCM) and regeneration mode (RM). To validate the proposed controller design methodology, the output current and voltage loop controllers are designed for a 3.5 kW converter. The step response showed a stable system with good transient performance thus validating the proposed controller design methodology.Ph. D.
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Subbiah, Rajesh. „An activity-based energy demand modeling framework for buildings: A bottom-up approach“. Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23084.
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Energy consumption by buildings, due to various factors such as temperature regulation, lighting, poses a threat to our environment and energy resources. In the United States, statistics reveal that commercial and residential buildings combined contribute about 40 percent of the overall energy consumption, and this figure is expected to increase. In order to manage the growing demand for energy, there is a need for energy system optimization, which would require a realistic, high-resolution energy-demand model. In this work, we investigate and model the energy consumption of buildings by taking into account physical, structural, economic, and social factors that influence energy use. We propose a novel activity based modeling framework that generates an energy demand profile on a regular basis for a given nominal day. We use this information to generate a building-level energy demand profile at highly dis-aggregated level. We then investigate the different possible uses of generated demand profiles in different What-if scenarios like urban-area planning, demand-side management, demand sensitive pricing, etc. We also provide a novel way to resolve correlational and consistency problems in the generation of individual-level and building-level "shared" activities which occur due to individuals\' interactions.Master of Science
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Mensah, Adje. „Modeling and Analysis of Solar Arrays for Grid Connected Systems with Maximum Power Point Tracking“. Honors in the Major Thesis, University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/422.
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This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.Bachelors
Engineering and Computer Science
Electrical Engineering
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Shah, Shahil. „Small and Large Signal Impedance Modeling for Stability Analysis of Grid-connected Voltage Source Converters“. Thesis, Rensselaer Polytechnic Institute, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10786614.
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Interactions between grid-connected converters and the networks at their terminals have resulted in stability and resonance problems in converter-based power systems, particularly in applications ranging from wind and PV farms to electric traction and HVDC transmission networks. Impedance-based modeling and analysis methods have found wide acceptance for the evaluation of these resonance problems.
This thesis presents small and large signal impedance modeling of grid-connected single and three phase voltage source converters (VSC) to enable the analysis of resonance conditions involving multiple frequency components, and both the ac and dc power systems at the VSC terminals. A modular impedance modeling approach is proposed by defining the VSC impedance as transfer matrix, which captures the frequency cross-coupling effects and also the coupling between the ac and dc power systems interfaced by the VSC. Ac and dc impedance models are developed for a VSC including the reflection of the network on the other side of the VSC. Signal-flow graphs for linear time-periodic (LTP) systems are proposed to streamline and visually describe the linearization of grid-connected converters including the frequency cross-coupling effects. Relationships between the impedance modeling in dq, sequence, and phasor domains are also developed. The phasor-domain impedance formulation links the impedance methods with the phasor-based state-space modeling approach generally used for bulk power systems. A large-signal impedance based method is developed for predicting the amplitude or severity of resonance under different grid conditions. The small-signal harmonic linearization method is extended for the large-signal impedance modeling of grid-connected converters. It is shown that the large-signal impedance of a converter is predominantly shaped by hard nonlinearities in the converter control system such as PWM saturation and limiters.
This thesis also deals with the problem of synchronizing a generator or microgrid with another power system. A VSC-based synchronizer is proposed for active phase synchronization and a distributed synchronization method is developed for microgrids.
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Depuru, Soma Shekara. „Modeling, Detection, and Prevention of Electricity Theft for Enhanced Performance and Security of Power Grid“. University of Toledo / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1341522225.
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Wang, Qiaojue. „An Integrated Multilevel Approach to Urban Development Modeling at Grid, Census block and Municipality Levels“. University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1407407288.
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Alexandros, Kordonis. „DYNAMIC ANALYSIS AND MODELING OF AC/AC POWER CONVERTERS FOR APPLICATIONS TO SMART-GRID SOLUTIONS“. 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199313.
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Öhrström, Adrian, und Joakim Frisk. „ASSESSMENT OF LARGE-SCALE ENERGY STORAGE FOR GRID-CONNECTED SOLAR PARKS IN NAMIBIA“. Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-32390.
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The aim of this thesis is to investigate the impact and feasibility of implementing large scale energy storage systems for the purpose of energy shifting at grid connected solar parks in Namibia. The country, which receives a large amount of solar irradiance, is ideal for the construction of solar parks. However, as solar parks are an intermittent energy source, energy storage systems are becoming an increasingly attractive option in order to decrease losses and secure the supply of electricity. For this purpose, a model in Matlab was created to simulate different storage types. The input data was simulated with site-specific information for Windhoek in PVsyst and then evaluated in an economic analysis where electricity tariff pricing, battery investment costs and exchange rates were the main variables. This report is structured through starting with an introduction where the background of the Namibian electricity market and essential terms are presented. This is followed by a detailed description of the Matlab model construction and a literature review of battery types and storage systems. The simulation models and results are then evaluated both from an economical and technical perspective and the main findings are presented. Through this project, it was concluded that energy storage is not feasible today with current market conditions. Even with favorable electricity tariffs and Namibian exchange rates, storage technologies are currently too expensive today in order for it to be economically defensible. The forecast is however promising, where decreasing investment prices and an increased of R&D in the technology is expected. From the constructed model, it was however concluded that sodium-sulfur is by far the best option today. The reason for this is the low initial cost and relatively high round-trip efficiency of the technology. The model also proved the potential of increased electricity security from using energy shifting. With energy storage, the delivered energy from solar parks now coincide better with the demand since the intermittency is decreased. However, for future studies a detailed analysis of energy storage effects on the grid is recommended.
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Skolthanarat, Siriya. „The Modeling and Control of a Wind Farm and Grid Interconnection in a multi-machine system“. Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/28920.
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This dissertation focuses on the modeling and control of WECS (Wind Energy Conversion System) in a multi-machine system. As one of the fastest growing renewable energy resources, the trend of wind energy changes to variable speed wind turbines. The concept of the variable speed is based on the variable speed according to the instantaneous wind speed of wind turbines. Since the utility grid requires the stable frequency and magnitude voltages, there must be grid interconnection of the wind farm and the utility grid. The grid interconnection must support the concept of the variable speed wind turbines. Since each wind turbine locates in a different location in a wind site, it receives the different wind speed. Hence the grid interconnection must convert the variable frequency and magnitude output voltages of the wind turbines to a synchronous frequency and magnitude voltages associated to the grid.
With the new technologies of power semiconductor devices, the power converter can operate with high voltage, high current, and high switching frequency. This results in a higher power capacity of a wind farm. Nonetheless, the power converters generate harmonic distortions to the utility grid. The harmonic distortions components in the voltages and currents of the grid degrade the power quality. This results in the damage of electrical components in the power system such as capacitor banks, inductors, protection devices, etc. The harmonic distortions can be reduced with the technology of the multi-level inverter. It is required that the wind energy provides the real and reactive power control for frequency and voltage stability. In order to achieve the power control, the modeling and control of the power electronic grid interconnection is presented in this dissertation.
The grid interconnection is modeled with linearization techniques. The models in frequency domain in the form of transfer functions are used to design the compensators in the control system. The model is considered as a SISO (Single Input Single Output) system to design the compensators in SISO tool of MATLAB. The selected control system is current control that can control the real and reactive powers independently. Furthermore, since the grid interconnection is modeled separately for each sub-system, the control system is verified with integration of the sub-systems. The grid interconnection is modeled in Simulink and simulated in the PSCAD.
In reality, the power system is comprised of multi-machines. They affect the power system stability, reliability, and quality. The dynamic modeling of an aggregated wind farm with synchronous generator and grid interconnection in a multi-machine system is presented. The test system is a 10-bus system with three generators and three loads. The dynamic modeling involves the power flow calculations that determine the equilibrium points of the system. The system is modeled with differential equations of wind turbines, synchronous generators, and grid interconnection. The system is modeled in the time domain in state space form. The system characteristics can be determined by poles or eigen values obtained from the characteristic equations. Since the system is MIMO (Multi Input Multi Output) system, the optimal control theory is used to reduce the deviation of system behaviors during disturbances. The LQR (Linear Quadratic Regulator) is utilized to control the system with eigen value assignment method. Simulation results in Simulink are illustrated.Ph. D.
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Vukadinovic, Vladimir, Gunnar Karlsson und Ólafur Helgason. „An analytical model for pedestrian content distribution in a grid of streets“. KTH, ACCESS Linnaeus Centre, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-109778.
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Mobile communication devices may be used for spreading multimedia data without support of an infrastructure. Such a scheme, where the data is carried by people walking around and relayed from device to device by means of short range radio, could potentially form a public content distribution system that spans vast urban areas. The transport mechanism is the flow of people and it can be studied but not engineered. We study the efficiency of pedestrian content distribution by modeling the mobility of people moving around in a city, constrained by a given topology. The model is supplemented by simulation of similar or related scenarios for validation and extension. The results show that contents spread well with pedestrian speeds already at low arrival rates into a studied region. Our contributions are both the queuing analytic model that captures the flow of people and the results on the feasibility of pedestrian content distribution.QC 20130109
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Bose, Sayak. „Cyber-physical modeling, analysis, and optimization - a shipboard smartgrid reconfiguration case study“. Diss., Kansas State University, 2012. http://hdl.handle.net/2097/15104.
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Doctor of PhilosophyDepartment of Electrical and Computer Engineering
Balasubramaniam Natarajan
Caterina Scoglio
Many physical and engineered systems (e.g., smart grid, transportation and biomedical systems) are increasingly being monitored and controlled over a communication network. These systems where sensing, communication, computation and real time control are closely integrated are referred to as cyber physical systems (CPS). Cyber physical systems present a plethora of challenges related to their design, analysis, optimization and control. In this dissertation, we present some fundamental methodologies to analyze the optimization of physical systems over a communication network. Specifically, we consider a medium voltage DC shipboard smart grid (SSG) reconfiguration problem as a test case to demonstrate our approach. The main goal of SSG reconfiguration is to change the topology of the physical power system by switching circuit breakers, switches, and other devices in the system in order to route power effectively to loads especially in the event of faults/failures. A majority of the prior work has focused on centralized approaches to optimize the switch configuration to maximize specific objectives. These methods are prohibitively complex and not suited for agile reconfiguration in mission critical situations. Decentralized solutions proposed do reduce complexity and implementation time at the cost of optimality. Unfortunately, none of the prior efforts in this arena address the cyber physical aspects of an SSG. This dissertation aims to bridge this gap by proposing a suite of methods to analyze both centralized and decentralized SSG reconfigurations that incorporate the effect of the underlying cyber infrastructure. The SSG reconfiguration problem is a mixed integer non convex optimization problem for which branch and bound based solutions have been proposed earlier. Here, optimal reconfiguration strategies prioritize the power delivered to vital loads over semi-vital and non vital loads. In this work, we propose a convex approximation to the original non convex problem that significantly reduces complexity of the SSG reconfiguration. Tradeoff between power delivered and number of switching operations after reconfiguration is discussed at steady state. Second, the distribution of end-to-end delay associated with fault diagnosis and reconfiguration in SSG is investigated from a cyber-physical system perspective. Specifically, a cross-layer total (end-to-end) delay analysis framework is introduced for SSG reconfiguration. The proposed framework stochastically models the heterogeneity of actions of various sub-systems viz., the reconfiguration of power systems, generation of fault information by sensor nodes associated to the power system, processing actions at control center to resolve fault locations and reconfiguration, and information flow through communication network to:(1) analyze the distribution of total delay in SSG reconfiguration after the occurrence of faults; and (2) propose design options for real-time reconfiguration solutions for shipboard CPS, that meet total delay requirements. Finally, the dissertation focuses on the quality of SSG reconfiguration solution with incomplete knowledge of the overall system state, and communication costs that may affect the quality (optimality) of the resulting reconfiguration. A dual decomposition based decentralized optimization in which the shipboard system is decomposed into multiple separable subsystems with agents is proposed. Specifically, agents monitoring each subsystem solve a local concave dual function of the original objective while neighboring agents share information over a communication network to obtain a global solution. The convergence of the proposed approach under varying network delays and quantization noise is analyzed and comparisons with centralized approaches are presented. Results demonstrate the effectiveness as well as tradeoffs involved in centralized and decentralized SSG reconfiguration approaches.
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Lyttle, David Nolan. „Modeling inhibition-mediated neural dynamics in the rodent spatial navigation system“. Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/311105.
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The work presented in this dissertation focuses on the use of computational and mathematical models to investigate how mammalian brains construct and maintain stable representations of space and location. Recordings of the activities of cells in the hippocampus and entorhinal cortex have provided strong, direct evidence that these cells and brain areas are involved in generating internal representations of the location of an animal in space. The emphasis of the first two portions of the dissertation are on understanding the factors that influence the scale and stability of these representations, both of which are important for accurate spatial navigation. In addition, it is argued in both cases that many of the computations observed in these systems emerge at least in part as a consequence of a particular type of network structure, where excitatory neurons are driven by external sources, and then mutually inhibit each other via interactions mediated by inhibitory cells. The first contribution of this thesis, which is described in chapter 2, is an investigation into the origin of the change in the scale of spatial representations across the dorsoventral axis of the hippocampus. Here it will be argued that this change in scale is due to increased processing of nonspatial information, rather than a dorsoventral change in the scale of the spatially-modulated inputs to this structure. Chapter 3 explores the factors influencing the dynamical stability of class of pattern-forming networks known as continuous attractor networks, which have been used to model various components of the spatial navigation systems, including head direction cells, place cells, and grid cells. Here it will be shown that network architecture, the amount of input drive, and the timescales at which cells interact all influence the stability of the patterns formed by these networks. Finally, in chapter 4, a new technique for analyzing neural data is introduced. This technique is a spike train similarity measure designed to compare spike trains on the basis of shared inhibition and bursts.
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Westman, Martin, und Ellen Nordén. „Modeling and comparative analysis of different grid-forming converter control concepts for very low inertia systems“. Thesis, Uppsala universitet, Institutionen för elektroteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-414402.
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As renewable power from DC sources are constantly increasing their power generation share compared to the high inertia generators that provide robustness to the grid, the overall stability of the grid decreases. Grid forming converter could be the solution to this problem. This thesis includes a pre-study of grid forming control methods, implementation of the most promising and relevant methods in a generic PSCAD modeling environment for comparative analysis and for establishing pros and cons. Lastly, studying the system impact of each grid forming control method through small-signal stability and fault analysis. Four methods of grid forming were implemented and evaluated during the course of the thesis, which were: Droop control, Virtual Synchronous Generator control, Power Synchronization control and Synchronous Power control. All methods fulfilled the criteria for successful implementation with good results. For further developments, we would recommend Synchronous Power control and Virtual Synchronous Generator control for their development potential and operational width.