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1
Assamagan, Ketevi Adikle. "Two-dimensional analytical model of an n+-p-p+ concentrator solar cell." Virtual Press, 1989. http://liblink.bsu.edu/uhtbin/catkey/560283.
Повний текст джерелаАнотація:
A successful model that could accurately predict the performances of n+-p-p+ concentrator solar cells should include a model of carrier photogeneration rates consistent with the spectral content of the incident light. Furthermore, a finite back surface recombination velocity should be considered since new techniques such as 'Back Surface Field' were developed to reduce the recombination rate at the rear of the cell.In the present work, a two-dimensional concentrator solar cell is modeled for low levels of injection. The model however, assumes an incident light containing one single wavelength. The incident light is assumed to decrease linearly from the center of the illuminated area until it vanishes at the edges of the cell. Finite recombination velocities are taken into account at the front and the back surfaces. Finite-width space charge regions are also included. The transport equations are solved for the carrier concentrations in different regions of the cell. The current density expressions are derived. The generation of theoretical current voltage characteristics is outlined. However, the use of these characteristics to predict cell performances is left for further research.Department of Physics and Astronomy
2
Vichare, Nitin Shrikrishna. "Robust Mahalanobis distance in power systems state estimation." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/40024.
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3
Altamirano, Chavez Armando. "An efficient algorithm using Householder's formulas for the solution of faulted power systems." Thesis, Kansas State University, 1986. http://hdl.handle.net/2097/9896.
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4
Wang, Yuanzhe, and 王远哲. "Macromodeling, passivity enforcement and fast simulation/verification for interconnects, power grids and large circuits." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B46604376.
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5
Rohani, Mehdiabadi Behrooz. "Power control for mobile radio systems using perceptual speech quality metrics." University of Western Australia. School of Electrical, Electronic and Computer Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0174.
Повний текст джерелаАнотація:
As the characteristics of mobile radio channels vary over time, transmit power must be controlled accordingly to ensure that the received signal level is within the receiver's sensitivity. As a consequence, modern mobile radio systems employ power control to regulate the received signal level such that it is neither less nor excessively larger than receiver sensitivity in order to maintain adequate service quality. In this context, speech quality measurement is an important aspect in the delivery of speech services as it will impact satisfaction of customers as well as the usage of precious system resources. A variety of techniques for speech quality measurement has been produced over the last few years as result of tireless research in the area of perceptual speech quality estimation. These are mainly based on psychoacoustic models of the human auditory systems. However, these techniques cannot be directly applied for real-time communication purposes as they typically require a copy of the transmitted and received speech signals for their operation. This thesis presents a novel technique of incorporating perceptual speech quality metrics with power control for mobile radio systems. The technique allows for standardized perceptual speech quality measurement algorithms to be used for in-service measurement of speech quality. The accuracy of the proposed Real-Time Perceptual Speech Quality Measurement (RTPSQM) technique with respect to measuring speech quality is first validated by extensive simulations. On this basis, RTPSQM is applied to power control in the Global System for Mobile (GSM) communication and the Universal Mobile Telecommunication System (UMTS). It is shown by simulations that the use of perceptual-based power control in GSM and UMTS outperforms conventional power control in terms of reducing the transmitter signal power required for providing adequate speech quality. This in turn facilitates the observed increase in system capacity and thus offers better utilization of available system resources. To enable an analytical performance assessment of perceptual speech quality metrics in power control, the mathematical frameworks for conventional and perceptual-based power control are derived. The derivations are performed for Code Division Multiple Access (CDMA) systems and kept as generic as possible. Numerical results are presented which could be used in a system design to readily find the Erlang capacity per cell for either of the considered power control algorithms.
6
Flath, Allen III. "Mathematical Programming Approach for the Design of Satellite Power Systems." UKnowledge, 2019. https://uknowledge.uky.edu/ece_etds/136.
Повний текст джерелаАнотація:
Satellite power systems can be understood as islanded dc microgrids supplied by specialized and coordinated solar cell arrays augmented by electrochemical battery systems to handle high-power loads and periods of eclipse. The periodic availability of power, the limited capacity of batteries, and the dependence of all mission service on power consumption create a unique situation in which temporal power and energy scarcity exist. A multi-period model of an orbital satellite power system’s performance over a mission’s duration can be constructed. A modular power system architecture is used to characterize the system’s constraints. Using mathematical programming, an optimization problem can be posed such that the optimal power and energy ratings for the power system are determined for any load schedule imposed by a given mission’s requirements. The optimal energy trajectory of the electrical power system over a mission’s duration is also determined when the mathematical programming problem is solved. A generic set of mission requirements is identified to test this approach, but the objective function of the resulting optimization problem can be modified to return different results. These results can provide a clear illustration of the trade-offs that designers of such power systems consider in the design process.
7
Wang, Minnan, and 王旻楠. "Islanding of systems of distributed generation using optimization methodology." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B44914933.
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8
Lam, King-hang, and 林勁恆. "Techniques for dynamic modelling of BIPV in supporting system design and BEMS." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39558460.
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9
Bhattacharya, Subroto. "Simulation of transient phenomena in high voltage direct-current converter systems." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26959.
Повний текст джерелаАнотація:
In this thesis models for the simulation of transient phenomena in high voltage direct-current systems are developed. The new converter model is versatile and the solution algorithm is free from numerical oscillations. A new generic inverter control described in this thesis is based on a predictive approach. Steady-state and transient simulations of two-terminal and multi-terminal (i.e., a parallel converter system) high voltage direct-current systems are carried out using the new converter system model. Comparison between the two-terminal transient simulation results and the high voltage direct-current simulator outputs shows good agreement.
An alternating-current/direct-current initialization procedure for the Electromagnetic
Transients Program (EMTP) has been investigated and a novel initialization
algorithm has been suggested in this thesis.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
10
Khosravi-Dehkordi, Iman. "Load flow feasibility under extreme contingencies." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100252.
Повний текст джерелаАнотація:
This thesis examines the problem of load flow feasibility, in other words, the conditions under which a power network characterized by the load flow equations has a steady-state solution. In this thesis, we are particularly interested in load flow feasibility in the presence of extreme contingencies such as the outage of several transmission lines.Denoting the load flow equations by z = f(x) where z is the vector of specified injections (the real and reactive bus demands, the specified real power bus generations and the specified bus voltage levels), the question addressed is whether there exists a real solution x to z = f( x) where x is the vector of unknown bus voltage magnitudes at load buses and unknown bus voltage phase angles at all buses but the reference bus. Attacking this problem via conventional load flow algorithms has a major drawback, principally the fact that such algorithms do not converge when the load flow injections z define or are close to defining an infeasible load flow. In such cases, lack of convergence may be due to load flow infeasibility or simply to the ill-conditioning of the load flow Jacobian matrix.
This thesis therefore makes use of the method of supporting hyperplanes to characterize the load flow feasibility region, defined as the set the injections z for which there exists a real solution x to the load flow equations. Supporting hyperplanes allow us to calculate the so-called load flow feasibility margin, which determines whether a given injection is feasible or not as well as measuring how close the injection is to the feasibility boundary. This requires solving a generalized eigenvalue problem and a corresponding optimization for the closest feasible boundary point to the given injection.
The effect of extreme network contingencies on the feasibility of a given injection is examined for two main cases: those contingencies that affect the feasibility region such as line outages and those that change the given injection itself such as an increase in VAR demand or the loss of a generator. The results show that the hyperplane method is a powerful tool for analyzing the effect of extreme contingencies on the feasibility of a power network.
11
Hecker, Rogelio Lorenzo. "Power feedback control in cylindrical grinding process." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/16619.
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12
Landford, Jordan. "Event Detection Using Correlation within Arrays of Streaming PMU Data." PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/3031.
Повний текст джерелаАнотація:
This thesis provides a synchrophasor data analysis methodology that leverages both statistical correlation techniques and a statistical distribution in order to identify data inconsistencies, as well as power system contingencies. This research utilizes archived Phasor Measurement Unit (PMU) data obtained from the Bonneville Power Administration in order to show that this methodology is not only feasible, but extremely useful for power systems monitoring, decision support, and planning purposes.
By analyzing positive sequence voltage angles between a pair of PMUs at two different substation locations, an historic record of correlation is established. From this record, a Rayleigh distribution of correlation coefficients is calculated. The statistical parameters of this Rayleigh distribution are used to infer occurrences of power system and data events.
To monitor an entire system, a simple solution would be observing each of these parameters for every PMU combination. One issue with this approach is that correlation of some PMU pairs may be redundant or yield little value to monitoring capabilities. Additionally, this approach quickly encounters scalability issues as each additional PMU adds considerably to computation - for example, if the system contains n PMUs the amount of computations will be n(n-1)/2. System-wide monitoring of these parameters in this fashion is cumbersome and inefficient.
To address these issues, an alternative scheme is proposed which involves monitoring only a subset of PMUs characterized by electrically coupled zones, or clusters, of PMUs. These clusters include both electrically-distant and electrically-near PMU sites. When monitored over an event, these yield statistical parameters sufficient for detecting event occurrences. This clustering scheme can be utilized to significantly decrease computation time and allocation of resources while maintaining optimal system observability.
Results from the statistical methods are presented for a select few case studies for both data and power system event detection. In addition, determination of cluster size and content is discussed in detail. Lastly, the viability of monitoring pertinent statistical parameters over various clustering schemes is demonstrated.
13
Hall, David Eric. "Transient thermal models for overhead current-carrying hardware." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/17133.
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14
Cho, Bo Hyung. "Modeling and analysis of spacecraft power systems." Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/54741.
Повний текст джерелаАнотація:
A comprehensive large-scale power system modeling is developed to facilitate the design and analysis of present and future spacecraft power systems. A two-port coupling method is utilized to provide a modularity in model building and analysis of the system. The modular approach allows the model to be flexible, verifiable and computationally efficient. A methodology for the system level analysis is presented with the ability to focus on the performance characteristics of an arbitrary component or subsystem. The system performance parameters are derived explicitly in terms of the two-port hybrid g-parameter representation of the component or subsystem, and impedances of its terminating subsystems. From this, the stability of the system is analytically determined and the subsystem interaction criteria is observed. Also presented is a model development from the empirical data employing the complex curve fitting technique. The technique is especially powerful for large scale system modeling and analysis where certain components and subsystems are viewed as black boxes with measurable terminal characteristics. The technique can also be used to realize a reduced order model of a complex subsystem.
The Direct Energy Transfer (DET) spacecraft power system is modeled to demonstrate the versatility of the comprehensive system model by performing various DC, small-signal and large-signal analyses. Of particular interest is the analysis of the large-signal behavior of the nonlinear solar array system by employing the state-plane method. The analysis of the solar array system operation focused on the transition mode between the shunt mode and the battery discharging mode is presented. The subsystem interaction problems in the local component and global system are illustrated. A methodology for the design and trouble-shooting of a system dealing with the interaction problems using the g-parameters is described. Finally, a system level analysis of the DET system using an empirical data modeling technique is performed.Ph. D.
15
Gao, Wenzhong. "New methodology for power system modeling and its application in machine modeling and simulation." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/14732.
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16
Li, Xiaojuan. "Estimations of power system frequency, phasors and their applications for fault location on power transmission lines." University of Western Australia. School of Electrical, Electronic and Computer Engineering, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0125.
Повний текст джерелаАнотація:
The thesis is devoted to the development of new algorithms for estimation of system frequency, power system phasors and transmission line fault location in the context of power system protection and control. A z-transform signal model combined with a nonlinear post-filtering scheme to estimate the operating frequency in a power system is first developed in the thesis. The signal model parameters are identified by an optimisation method in which the error between the model output and the actual signal that represents a voltage or current in the power system is minimised. The form and the structure of the signal model do not require iterations in the optimisation process for parameter identification. The system operating frequency is directly evaluated from the model parameters. Effects of noise and any frequency components other than the operating or supply-frequency on the accuracy are countered very effectively by applying a median post-filtering on the time series representing the frequency estimates derived from the model. Extensive simulation studies and comparisons with previously-published frequency estimation techniques confirm the high performance of the method developed in the thesis in terms of accuracy and time delay. With respect to power system phasor estimation, a method is developed based on waveform interpolation in the discrete time-domain to counter the spectral leakage errors arising in forming, by discrete Fourier transform (DFT), the supply frequency phasors representing power system voltages and currents when there are system frequency deviations from the nominal value. The interpolation scheme allows DFT evaluation to be performed with a time window length which is exactly equal to the fundamental period of the voltage or current waveform. Comparative studies presented in the thesis confirm the improvements achieved by the method proposed over other previouslypublished techniques in terms of accuracy and computing time. With the availability of accurate operating frequency and phasor estimates, an optimal fault location method based on multi-conductor distributedparameter line model is developed. The method is a general one which is applicable to any transmission line configurations, including multi-terminal lines. The fault location method is based on the minimisation of an objective function in which the fault distance is a variable. The objective function is formed from combining the phase-variable distributed-parameter equations of individual line sections from the fault point to the line terminals. The multivariable minimisation leads to high accuracy and robustness of the fault location algorithm in which any voltage/current measurement errors, including sampling time synchronisation errors, are represented in the estimation procedure as variables in addition to the fault distance. Extensive simulation studies are performed to verify that the method developed is highly accurate and robust. The thesis is supported by two international publications of which the candidate is a joint author.
17
Thai, Doan Hoang Cau Australian Graduate School of Management Australian School of Business UNSW. "Analysing tacit collusion in oligopolistic electricity markets using a co-evolutionary approach." Awarded by:University of New South Wales. Australian Graduate School of Management, 2005. http://handle.unsw.edu.au/1959.4/22478.
Повний текст джерелаАнотація:
Wholesale electricity markets now operate in many countries around the world. These markets determine a spot price for electricity as the clearing price when generators bid in energy at various prices. As the trading in a wholesale electricity market can be seen as a dynamic repeated game, it would be expected that profit maximising generators learn to engage in tacit collusion to profitably increase spot market prices. This thesis investigates this tacit collusion of generators in oligopolistic electricity markets. We do not follow the approach of previous work in game theory that presupposes firms' collusive strategies to enforce collusion in an oligopoly. Instead, we develop a co-evolutionary approach (extending previous work in this area) using a genetic algorithm (GA) to co-evolve strategies for all generators in some stylised models of an electricity market. The bidding strategy of each generator is modelled as a set of bidding actions, one for each possible discrete state of the state space observed by the generator. The market trading interactions are simulated to determine the fitness of a particular strategy. The tacitly collusive outcomes and strategies emerging from computational experiments are thus obtained from the learning or evolutionary process instead of from any pre-specification. Analysing many of those emergent collusive outcomes and strategies. we are able to specify the mechanism of tacit collusion and investigate how the market environment can affect it. We find that the learned collusive strategies are similar to the forgiving trigger strategies of classical supergame theory (Green and Porter, 1984). Also using computational experiments, we can determine which characteristics of the market environment encourage or hinder tacit collusion. The findings from this thesis provide insights on tacit collusion in an oligopoly and policy implications from a learning perspective. With modelling flexibility, our co-evolutionary approach can be extended to study strategic behaviour in an oligopoly considering many other market characteristics.
18
Liu, Xinghua, and 刘兴华. "Power system operation integrating clean energy and environmental considerations." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43085866.
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19
Uong, Hoang. "The application of the ordered list method and the dynamic programming to the unit commitment." PDXScholar, 1989. https://pdxscholar.library.pdx.edu/open_access_etds/3948.
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20
Yu, Chang, and 余暢. "An investigation of subsynchronous oscillation of AC/DC power systems: modeling and analysis." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B37151885.
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21
Noudjiep, Djiepkop Giresse Franck. "Feeder reconfiguration scheme with integration of renewable energy sources using a Particle Swarm Optimisation method." Thesis, Cape Peninsula University of Technology, 2018. http://hdl.handle.net/20.500.11838/2712.
Повний текст джерелаАнотація:
Thesis (Master of Engineering in Electrical Engineering)--Cape Peninsula University of Technology, 2018.A smart grid is an intelligent power delivery system integrating traditional and advanced control, monitoring, and protection systems for enhanced reliability, improved efficiency, and quality of supply. To achieve a smart grid, technical challenges such as voltage instability; power loss; and unscheduled power interruptions should be mitigated. Therefore, future smart grids will require intelligent solutions at transmission and distribution levels, and optimal placement & sizing of grid components for optimal steady state and dynamic operation of the power systems. At distribution levels, feeder reconfiguration and Distributed Generation (DG) can be used to improve the distribution network performance. Feeder reconfiguration consists of readjusting the topology of the primary distribution network by remote control of the tie and sectionalizing switches under normal and abnormal conditions. Its main applications include service restoration after a power outage, load balancing by relieving overloads from some feeders to adjacent feeders, and power loss minimisation for better efficiency. On the other hand, the DG placement problem entails finding the optimal location and size of the DG for integration in a distribution network to boost the network performance. This research aims to develop Particle Swarm Optimization (PSO) algorithms to solve the distribution network feeder reconfiguration and DG placement & sizing problems. Initially, the feeder reconfiguration problem is treated as a single-objective optimisation problem (real power loss minimisation) and then converted into a multi-objective optimisation problem (real power loss minimisation and load balancing). Similarly, the DG placement problem is treated as a single-objective problem (real power loss minimisation) and then converted into a multi-objective optimisation problem (real power loss minimisation, voltage deviation minimisation, Voltage stability Index maximisation). The developed PSO algorithms are implemented and tested for the 16-bus, the 33-bus, and the 69-bus IEEE distribution systems. Additionally, a parallel computing method is developed to study the operation of a distribution network with a feeder reconfiguration scheme under dynamic loading conditions.
22
Heo, Deukhyoun. "Silicon MOS field effect transistor RF/Microwave nonlinear model study and power amplifier development for wireless communications." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/15618.
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23
Mazumdar, Joy. "System and method for determining harmonic contributions from nonlinear loads in power systems." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/23215.
Повний текст джерелаАнотація:
The objective of this research is to introduce a neural network based solution for the problem of measuring the actual amount of harmonic current injected into a power network by an individual nonlinear load. Harmonic currents from nonlinear loads propagate through the system and cause harmonic pollution. As a result, voltage at the point of common coupling (PCC) is rarely sinusoidal. The IEEE 519 harmonic standard provides customer and utility harmonic limits and many utilities are now requiring their customers to comply with IEEE 519. Measurements of the customer’s current at the PCC are expected to determine the customer’s compliance with IEEE 519. However, results in this research show that the current measurements at the PCC are not always reliable in that determination. In such a case, it may be necessary to determine what the customer’s true current harmonic distortions would be if the PCC voltage could be a pure sinusoidal voltage. However, establishing a pure sinusoidal voltage at the PCC may not be feasible since that would mean performing utility switching to reduce the system impedance. An alternative approach is to use a neural network that is able to learn the customer’s load admittance. Then, it is possible to predict the customer’s true current harmonic distortions based on mathematically applying a pure sinusoidal voltage to the learned load admittance. The proposed method is called load modeling. Load modeling predicts the true harmonic current that can be attributed to a customer regardless of whether a resonant condition exists on the utility power system. If a corrective action is taken by the customer, another important parameter of interest is the change in the voltage distortion level at the PCC due to the corrective action of the customer. This issue is also addressed by using the dual of the load modeling method. Topologies of the neural networks used in this research include multilayer perceptron neural networks and recurrent neural networks. The theory and implementation of a new neural network topology known as an Echo State Networks is also introduced. The proposed methods are verified on a number of different power electronic test circuits as well as field data. The main advantages of the proposed methods are that only waveforms of voltages and currents are required for their operation and they are applicable to both single and three phase systems. The proposed methods can be integrated into any existing power quality instrument or can be fabricated into a commercial standalone instrument that could be installed in substations of large customer loads, or used as a hand-held clip on instrument.
24
Pourbeik, Pouyan. "Design and coordination of stabilisers for generators and FACTS devices in multimachine power systems /." Title page, contents and abstract only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09php877.pdf.
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25
Kari, Uday Shankar. "Emergency evacuation around nuclear power stations : a systems approach /." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-03122009-040357/.
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26
Fachrizal, Reza. "Synergy between Residential Electric Vehicle Charging and Photovoltaic Power Generation through Smart Charging Schemes : Models for Self-Consumption and Hosting Capacity Assessments." Licentiate thesis, Uppsala universitet, Byggteknik och byggd miljö, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-419665.
Повний текст джерелаАнотація:
The world is now in a transition towards a more sustainable future. Actions to reduce the green-house gases (GHG) emissions have been promoted and implemented globally, including switching to electric vehicles (EVs) and renewable energy technologies, such as solar photovoltaics (PV). This has led to a massive increase of EVs and PV adoption worldwide in the recent decade. However, large integration of EVs and PV in buildings and electricity distribution systems pose new challenges such as increased peak loads, power mismatch, component overloading, and voltage violations, etc. Improved synergy between EVs, PV and other building electricity load can overcome these challenges. Coordinated charging of EVs, or so-called EV smart charging, is believed to a promising solution to improve the synergy. This licentiate thesis investigates the synergy between residential EV charging and PV generation with the application of EV smart charging schemes. The investigation in this thesis was carried out on the individual building, community and distribution grid levels. Smart charging models with an objective to reduce the net-load (load - generation) variability in residential buildings were developed and simulated. Reducing the net-load variability implies both reducing the peak loads and increasing the self-consumption of local generation, which will also lead to improved power grid performance. Combined PV-EV grid hosting capacity was also assessed. Results show that smart charging schemes could improve the PV self-consumption and reduce the peak loads in buildings with EVs and PV systems. The PV self-consumption could be increased up to 8.7% and the peak load could be reduced down to 50%. The limited improvement on self-consumption was due to low EV availability at homes during midday when the solar power peaks. Results also show that EV smart charging could improve the grid performance such as reduce the grid losses and voltage violation occurrences. The smart charging schemes improve the grid hosting capacity for EVs significantly and for PV slightly. It can also be concluded that there was a slight positive correlation between PV and EV hosting capacity in the case of residential electricity distribution grids.
27
Stefopoulos, Georgios Konstantinos. "Quadratic power system modeling and simulation with application to voltage recovery and optimal allocation of VAr support." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29695.
Повний текст джерелаАнотація:
Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2010.Committee Chair: Meliopoulos, A. P. Sakis; Committee Member: Deng, Shijie; Committee Member: Divan, Deepakraj; Committee Member: Harley, Ronald; Committee Member: Taylor, David. Part of the SMARTech Electronic Thesis and Dissertation Collection.
28
Du, Zhaobin, and 杜兆斌. "Area COI-based slow frequency dynamics modeling, analysis and emergency control for interconnected power systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B4175783X.
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29
Hamilton, Nicholas Michael. "Anisotropy of the Reynolds Stress Tensor in the Wakes of Counter-Rotating Wind Turbine Arrays." PDXScholar, 2014. https://pdxscholar.library.pdx.edu/open_access_etds/1848.
Повний текст джерелаАнотація:
A wind turbine array was constructed in the wind tunnel at Portland State University in a standard Cartesian arrangement. Configurations of the turbine array were tested with rotor blades set to rotate in either a clockwise or counter-clockwise sense. Measurements of velocity were made with stereo particle-image velocimetry. Mean statistics of velocities and Reynolds stresses clearly show the effect of direction of rotation of rotor blades for both entrance and exit row turbines. Rotational sense of the turbine blades is visible in the mean spanwise velocity W and the Reynolds shear stress -[macron over vw]. The normalized anisotropy tensor was decomposed yielding invariants [lowercase eta] and [lowercase xi], which are plotted onto the Lumley triangle. Invariants of the normalized Reynolds stress anisotropy tensor indicate that distinct characters of turbulence exist in regions of the wake following the nacelle and the rotor blade tips. Eigendecomposition of the tensor yields principle components and corresponding coordinate system transformations. Characteristic spheroids are composed with the eigenvalues from the decomposition yielding shapes predicted by the Lumley triangle. Rotation of the coordinate system defined by the eigenvectors demonstrates streamwise trends, especially trailing the top rotor tip and below the hub of the rotors. Direction of rotation of rotor blades is evidenced in the orientation of characteristic spheroids according to principle axes. The characteristic spheroids of the anisotropy tensor and their relate alignments varies between cases clearly seen in the inflows to exit row turbines. There the normalized Reynolds stress anisotropy tensor shows cumulative effects of the rotational sense of upstream turbines. Comparison between the invariants of the Reynolds stress anisotropy tensor and terms from the mean mechanical energy equation indicate a correlation between the degree of anisotropy and the regions of the wind turbine wakes where turbulence kinetic energy is produced. The flux of kinetic energy into the momentum-deficit area of the wake from above the canopy is associated with prolate characteristic spheroids. Flux upward into the wake from below the rotor area is associate with oblate characteristic spheroids. Turbulence in the region of the flow directly following the nacelle of the wind turbines demonstrates more isotropy compared to the regions following the rotor blades. The power and power coefficients for wind turbines indicate that flow structures on the order of magnitude of the spanwise turbine spacing that increase turbine efficiency depending on particular array configuration.
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Chandler, Shawn Aaron. "Global Time-Independent Agent-Based Simulation for Transactive Energy System Dispatch and Schedule Forecasting." PDXScholar, 2015. https://pdxscholar.library.pdx.edu/open_access_etds/2212.
Повний текст джерелаАнотація:
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.
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SILVA, WANDERLEI M. da. "Proposta de novas topologias de conversores 'C-DUMP' para o acionamento de motores e geradores de relutancia chaveados." reponame:Repositório Institucional do IPEN, 2004. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11336.
Повний текст джерелаАнотація:
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Tese (Doutoramento)
IPEN/T
Escola Politecnica, Universidade de Sao Paulo - POLI/USP
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Krishnamurthy, Senthil. "Development of decomposition methods for solution of a multiarea power dispatch optimisation problem." Thesis, Cape Peninsula University of Technology, 2013. http://hdl.handle.net/20.500.11838/1193.
Повний текст джерелаАнотація:
Thesis submitted in fulfilment of the requirements for the degree
Doctor of Technology: Electrical Engineering
in the Faculty of Engineering
at the Cape Peninsula University of Technology
2013The objective of the economic dispatch problem of electrical power generation is to schedule the committed generating unit outputs to meet the required load demand while satisfying the system equality and inequality constraints. The thesis formulates single area and multi-area Combined Economic Emission Dispatch (CEED) problem as single criterion, bi-criterion and multi-criteria optimisation problems based on fuel cost and emission criterion functions, constraints over the operational limits of the generator and the tie-lines, and requirements for a balance between the produced power and the system demand and power loss. Various methods, algorithms and softwares are developed to find solution of the formulated problems in single area and multi-area power systems. The developed methods are based on the classical Lagrange's and on the meta-heuristic Particle Swarm Optimisation (PSO) techniques for a single criterion function. Transformation of the bi-criteria or multi-criteria dispatch problem to a single criterion one is done by some existing and two proposed in the thesis penalty factors. The solution of the CEED problems is obtained through implementation of the developed software in a sequential way using a single computer, or in a data-parallel way in a Matlab Cluster of Computers (CC). The capabilities of the developed Lagrange's and PSO algorithms are compared on the basis of the obtained results. The conclusion is that the Lagrange's method and algorithm allows to receive better solution for less computation time. Data-parallel implementation of the developed software allows a lot of results to be obtained for the same problem using different values of some of the problem parameters. According to the literature papers, there are many algorithms available to solve the CEED problem for the single area power systems using sequential methods of optimisation, but they consume more computation time to solve this problem. The thesis aim is to develop a decomposition-coordinating algorithm for solution of the Multi Area Economic Emission Dispatch (MAEED) problem of power systems. The MAEED problem deals with the optimal power dispatch inside and between the multiple areas and addresses the environmental issue during the economic dispatch. To ensure the system security, tie-line transfer limits between different areas are incorporated as a set of constraints in the optimisation problem. A decomposition coordinating method based on the Lagrange's algorithm is developed to derive a set of optimal solutions to minimize the fuel cost and emissions of the multi-area power systems. An augmented function of Lagrange is applied and its decomposition in interconnected sub problems is done using a new coordinating-vector. Task-parallel computing in a Matlab Cluster is used to solve the multi-area dispatch problem. The calculations and tasks allocation to the Cluster workers are based on a shared memory architecture. Implementation of the calculation algorithm using a Cluster of Computers allows quick and simpler solutions to the multi-area CEED problem. The thesis applied the developed algorithms for the various problem formulation scenarios, i.e. fuel cost and emission function with and without valve point loading effect, quadratic and cubic fuel cost and emission functions. The various IEEE benchmark models are used to test the developed Lagrange's and PSO algorithms in the sequential, data-parallel, and task-parallel implementations. Developed methods, algorithms and software programmes can be applied for solution of various energy management problems in the regional and national control centres, smart grid applications, and in education and research institutions.
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Hamilton, Nicholas Michael. "Wake Character in the Wind Turbine Array: (Dis-)Organization, Spatial and Dynamic Evolution and Low-dimensional Modeling." PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/3084.
Повний текст джерелаАнотація:
To maximize the effectiveness of the rapidly increasing capacity of installed wind energy resources, new models must be developed that are capable of more nuanced control of each wind turbine so that each device is more responsive to inflow events. Models used to plan wind turbine arrays and control behavior of devices within the farm currently make questionable estimates of the incoming atmospheric flow and update turbine configurations infrequently. As a result, wind turbines often operate at diminished capacities, especially in arrays where wind turbine wakes interact and inflow conditions are far from ideal. New turbine control and wake prediction models must be developed to tune individual devices and make accurate power predictions. To that end, wind tunnel experiments are conducted detailing the turbulent flow in the wake of a wind turbine in a model-scale array. The proper orthogonal decomposition (POD) is applied to characterize the spatial evolution of structures in the wake. Mode bases from distinct downstream locations are reconciled through a secondary decomposition, called double proper orthogonal decomposition (DPOD), indicating that modes of common rank in the wake share an ordered set of sub-modal projections whose organization delineates underlying wake structures and spatial evolution. The doubly truncated basis of sub-modal structures represents a reduction to 0.015% of the total degrees of freedom of the wind turbine wake. Low-order representations of the Reynolds stress tensor are made using only the most dominant DPOD modes, corrected to account for energy excluded from the truncated basis with a tensor of constant coefficients defined to rescale the low-order representation of the stresses to match the original statistics. Data from the wind turbine wake are contrasted against simulation data from a fully-developed channel flow, illuminating a range of anisotropic states of turbulence. Complexity of flow descriptions resulting from truncated POD bases is suppressed in severe basis truncations, exaggerating anisotropy of the modeled flow and, in extreme cases, can lead to the loss of three dimensionality. Constant corrections to the low-order descriptions of the Reynolds stress tensor reduce the root-mean-square error between low-order descriptions of the flow and the full statistics as much as 40% and, in some cases, reintroduce three-dimensionality to severe truncations of POD bases. Low-dimensional models are constructed by coupling the evolution of the dynamic mode coefficients through their respective time derivatives and successfully account for non-linear mode interaction. Deviation between time derivatives of mode coefficients and their least-squares fit is amplified in numerical integration of the system, leading to unstable long-time solutions. Periodic recalibration of the dynamical system is undertaken by limiting the integration time and using a virtual sensor upstream of the wind turbine actuator disk in to read the effective inflow velocity. A series of open-loop transfer functions are designed to inform the low-order dynamical system of the flow incident to the wind turbine rotor. Validation data shows that the model tuned to the inflow reproduces dynamic mode coefficients with little to no error given a sufficiently small interval between instances of recalibration. The reduced-order model makes accurate predictions of the wake when informed of turbulent inflow events. The modeling scheme represents a viable path for continuous time feedback and control that may be used to selectively tune a wind turbine in the effort to maximize power output of large wind farms.
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Yang, Fang. "A Comprehensive Approach for Bulk Power System Reliability Assessment." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14488.
Повний текст джерелаАнотація:
Abstract
The goal of this research is to advance the state of the art in bulk power system reliability assessment. Bulk power system reliability assessment is an important procedure at both power system planning and operating stages to assure reliable and acceptable electricity service to customers. With the increase in the complexity of modern power systems and advances in the power industry toward restructuring, the system models and algorithms of traditional reliability assessment techniques are becoming obsolete as they suffer from nonrealistic system models and slow convergence (even non-convergence) when multi-level contingencies are considered and the system is overstressed. To allow more rigor in system modeling and higher computational efficiency in reliability evaluation procedures, this research proposes an analytically-based security-constrained adequacy evaluation (SCAE) methodology that performs bulk power system reliability assessment.
The SCAE methodology adopts a single-phase quadratized power flow (SPQPF) model as a basis and encompasses three main steps: (1) critical contingency selection, (2) effects analysis, and (3) reliability index computations. In the critical contingency selection, an improved contingency selection method is developed using a wind-chime contingency enumeration scheme and a performance index approach based on the system state linearization technique, which can rank critical contingencies with high accuracy and efficiency. In the effects analysis for selected critical contingencies, a non-divergent optimal quadratized power flow (NDOQPF) algorithm is developed to (1) incorporate major system operating practices, security constraints, and remedial actions in a constrained optimization problem and (2) guarantee convergence and provide a solution under all conditions. This algorithm is also capable of efficiently solving the ISO/RTO operational mode in deregulated power systems. Based on the results of the effects analysis, reliability indices that provide a quantitative indication of the system reliability level are computed. In addition, this research extends the proposed SCAE framework to include the effects of protection system hidden failures on bulk power system reliability.
The overall SCAE methodology is implemented and applied to IEEE reliability test systems, and evaluation results demonstrate the expected features of proposed advanced techniques. Finally, the contributions of this research are summarized and recommendations for future research are proposed.
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Lin, TsungPo. "An adaptive modeling and simulation environment for combined-cycle data reconciliation and degradation estimation." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24819.
Повний текст джерелаАнотація:
Thesis (Ph.D.)--Aerospace Engineering, Georgia Institute of Technology, 2008.Committee Chair: Dimitri Mavris; Committee Member: Erwing Calleros; Committee Member: Hongmei Chen; Committee Member: Mark Waters; Committee Member: Vitali Volovoi.
36
Kong, Kang-Chuen. "Real time simulations of EMTP results." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-07292009-090324/.
Повний текст джерела
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Bettoni, Luiz Marcelo Michelotti. "Modelos plim para otimização de circuitos da rede de distribuição secundária de energia elétrica." Universidade Tecnológica Federal do Paraná, 2011. http://repositorio.utfpr.edu.br/jspui/handle/1/373.
Повний текст джерелаАнотація:
ANEELEm sistemas de distribuição de energia elétrica é comum o desenvolvimento de projetos que busquem a melhoria dos índices de equilíbrio de cargas, carregamento de transformadores e quedas de tensão ao longo dos circuitos da rede secundária. O presente trabalho apresenta modelos matemáticos de Programação Linear Inteira Mista (PLIM) para quatro das intervenções técnicas usualmente praticadas com vistas a estas melhorias: balanceamento de carga, troca de condutor, divisão de circuito e remanejamento de carga. Os modelos respeitam aspectos técnicos, elétricos e considerações operacionais dos especialistas na busca de soluções que minimizem o investimento necessário para restabelecimento destes índices. Um método linear simplificado para o cálculo elétrico, baseado no Backward-Forward Sweep (BFS), é proposto a fim de incluir restrições sobre níveis de tensão diretamente nos modelos. A realização conjunta das intervenções é sugerida em uma proposta de integração de modelos por encadeamento de soluções. Para desenvolvimento dos modelos PLIM criou-se o ambiente de modelagem Gusek, interface para o solver livre GLPK. Os modelos foram implementados em uma ferramenta de apoio à tomada de decisão para projetos de melhoria de rede. Resultados são apresentados através de estudos de caso com dados de circuitos reais.
In eletric power distribution systems it is common to develop projects to improve the levels of load balancing, transformer loading and voltage drops along secondary network circuits. This paper presents Mixed Integer Linear Programming (MILP) mathematical models for adressing four technical interventions usually undertaken to achieve these improvements: load balancing, conductor changing, circuit split, and load relocation. These models comply with technical and electrical aspects and satisfy operational considerations from specialists in finding solutions that minimize the required investment for restoration of circuit levels. A simplified linear power flow method, based on the Backward-Forward Sweep (BFS), is proposed to include voltage levels constraints into the models. The combination of interventions is suggested in a proposal for integration of models by chaining solutions. To develop the MILP models the GUSEK modeling environment was created as an interface for the GLPK free solver. The models were implemented in a decision-making support tool for network improvement projects. Results are presented through case studies with data from real circuits.
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Pereira, Andre Flavio Soares. "Planejamento da operação energetica e da manutenção no sistema hidrotermico de potencia brasileiro." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264637.
Повний текст джерелаАнотація:
Orientadores: Sergio Valdir Bajay, Paulo Sergio Franco BarbosaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Nesta dissertação se avalia o estado da arte do planejamento da operação energética e da manutenção de usinas em sistemas hidrotérmicos de potência e se propõe algumas inovações. Neste contexto, se faz uma revisão crítica das metodologias de planejamento empregadas no setor elétrico brasileiro, incluindo as bases de dados que dão suporte a estas metodologias e dando destaque às práticas atuais do Operador Nacional do Sistema Elétrico (ONS); várias propostas de avanços metodológicos são feitas ao longo desta parte do trabalho. Uma outra parte desta dissertação envolve a aplicação de um modelo de otimização, a médio prazo, da operação de algumas usinas do Sistema Interligado Nacional (SIN), pertencentes a uma concessionária geradora no Estado de São Paulo, satisfazendo as metas de geração impostas pelo planejamento centralizado do SIN, realizado pelo ONS, e restrições associadas ao uso múltiplo da água nos reservatórios destas usinas, dentre outras. Várias funções-objetivo podem ser utilizadas neste modelo, dependendo das finalidades a serem atingidas nas simulações. O modelo foi aplicado ao parque gerador hidrelétrico da empresa AES, nos rios Tietê e Pardo; algumas simulações foram feitas, discutindo-se os resultados alcançados
Abstract: The state-of-the-art of power plant scheduling and maintenance planning in hydro-thermal power systems is evaluated in this thesis and some innovations are proposed. In this context, a critical review of the planning methodologies employed in the Brazilian power sector is carried out, including the data bases which support these methodologies and pointing out the current practices of the National Operator of the Power System (ONS); several proposals concerning advances in these methodologies are put forward along this work. In another part of this thesis, the medium-term scheduling of some power stations of the National Interlinked System (SIN) belonging to a utility in the State of São Paulo are modeled through an optimization algorithm, which meets the generation targets imposed by the centralized planning of SIN, carried out by ONS, and constraints associated to multiple uses of water in the reservoirs of these plants, among other constraints. Several objective functions can be used in this model, depending on the purposes to be achieved in the simulations. The model was applied to the hydroelectric generation system of the company AES, in the rivers Tietê and Pardo; some simulations were carried out and their results are discussed in the thesis
Mestrado
Planejamento de Sistemas Energeticos
Mestre em Planejamento de Sistemas Energéticos
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Nyimi, Douglas Ricardo Slaughter. "Computabilidade e limites da matemática das teorias físicas: aplicações em sistemas elétricos de potência." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-09122011-101051/.
Повний текст джерелаАнотація:
Apesar dos modelos usados em engenharia serem, em sua maioria, reconhecidamente aproximados, acredita-se que a matemática usada na física e nos próprios modelos é infinitamente precisa e que tais teorias físicas poderiam prever completamente qualquer evento relacionado às variáveis equacionadas. No limite, seria possível prever o estado do universo em qualquer instante, crença esta chamada de determinismo. Claro está que essa pretensão é apenas de princípio, sendo impossível na prática. No entanto, pesquisas sobre os fundamentos da matemática e outras teorias matemáticas desenvolvidas no século XX sugerem que a matemática (e, consequentemente, a física) teria certos limites inerentes. A análise feita nesta tese fundamenta seus argumentos na Teoria das Funções Recursivas e Computabilidade Efetiva e na Teoria do Caos Determinístico. O objetivo principal é tratar de apurar a existência de limites inerentes e como tais limites se aplicariam aos sistemas elétricos de potência (mais especificamente nos tópicos fluxo de carga, transitórios eletromecânicos, transitórios eletromagnéticos e eletrônica de potência) e à engenharia de controle.Although the models used in engineering are, in most cases, admittedly approximated, it is believed that the Mathematics used in Physics and in these models, is infinitely precise and that such physical theories could fully predict any event related to variables in equations. In the limit, it would be possible to predict the state of the universe at any moment, this belief is called determinism. It is clear that this claim is only in principle, impossible in practice. However, research on the foundations of Mathematics and other mathematical theories developed in the 20th century suggest that the Mathematics (and hence Physics) would have certain inherent limitations. The analysis made in this thesis has the arguments based on the Theory of Recursive Functions and Effective Computability and the Theory of Deterministic Chaos. The main objective is to find out the existence of inherent limits and how these limits could be applied to electric power systems (more specifically to the topics load flow, electromechanical transient and electromagnetic transient and power electronics) and control engineering.
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Domingues, Adriana Favaro. "Um modelo de espaço de estados com representação de segunda ordem para a analise das oscilações de modo interarea em sistemas de energia eletrica." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260320.
Повний текст джерелаАнотація:
Orientador : Vivaldo Fernando da CostaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: Este trabalho aborda o problema das oscilações eletromecânicas de baixa freqüência de modo interárea em sistemas de energia elétrica através de duas metodologias: primeiramente, através do método convencional da análise modal linear e, posteriormente, através da aplicação do método da forma normal dos campos vetoriais como ferramenta para viabilizar o acréscimo dos termos não lineares de segunda ordem resultantes da expansão em série de Taylor. Neste caso, o método da forma normal é aplicado a um Modelo de Sensibilidade de Potência com representação de segunda ordem, para investigar os efeitos das interações não lineares entre os modos naturais de oscilação de sistemas de energia elétrica. São consideradas, em ambas as análises, a inclusão de dispositivos FACTS e da modelagem dinâmica das cargas. As simulações são realizadas para um sistema simétrico de duas áreas e para o Sistema Equivalente Sul-Sudeste Brasileiro. A metodologia de análise proposta mostra-se bastante satisfatória como alternativa à simulação não linear no domínio do tempo e à análise modal convencional
Abstract: In this work, the analysis of power systems inter-area mode oscillations is performed by the application of two different methodologies: first, the linear modal analysis, and then the analysis including second order nonlinear terms from a Taylor series expansion, with the application of the method of normal forms of vector fields. In this case, the method of normal forms is applied to a Power Sensitivity Model including second order nonlinear terms, in order to investigate the effects of nonlinear interactions between system modes. Both methodologies consider the inclusion of FACTS devices and dynamic load model. Simulations are performed for a symmetric two-area test power system and for the Equivalent South-Southeast Brazilian system. The results obtained show that the methodology proposed is very effective as an alternative to linear modal analysis and timedomain simulation in the performance of inter-area mode oscillations analysis
Doutorado
Energia Eletrica
Doutor em Engenharia Elétrica
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Farthing, Brendan J. "Statistical aspects in the design and analysis of long term ecological monitoring efforts." Thesis, Queensland University of Technology, 2002. https://eprints.qut.edu.au/37118/1/37118_Farthing_2002.pdf.
Повний текст джерелаАнотація:
There is increasing public concern about the health of our environment and the burden placed on it by the way the world uses its natural resources. This requires
decisions be made about the best manner to care for these resources. To make these decisions, long term ecological monitoring efforts are necessary as they provide
decision makers with accurate information concerning the status of measures in time. The planning of such efforts is a study of decision making in itself. This thesis has considered ways in which those responsible for the planning of long term ecological monitoring surveys can go about this process. To start, the concept of a
Decision Support System (DSS) is explored. This provides a framework under which a number of alternative decisions may be considered and the best one chosen to solve
a problem. We then move on to model based methods for survey design, using the DSS concept to varying degrees. This involves specifying a model for data analysis
and then designing a sampling scheme to best estimate parameters of interest under
this model. One such method is to consider the power of a linear regression to detect changes in a variable over time (Gerrodette 1987). This is explored and extended
upon, but it was found that some assumptions underlying the procedure may be violated in practice. In an attempt to rectify such violations a Bayesian spatiotemporal
model was developed and applied to a real data set from the Queensland Department of Natural Resources (QDNR). Three approaches that use the output of this model to help design future schemes are then discussed. The first being a
survey sampling approach similar to the power analysis approach already explored.
The second is a simulation method, in which a hypothetical data set is sampled and modelled in an effort to select the best procedure for the decision to be made. The final approach is Bayesian survey design which closely follows the ideas of Bayesian
experimental design (Chaloner & Verdinelli 1995). The aim of this approach is to select a plan that maximises a utility function which assigns a value of worth to
various decisions outcomes. In this way, the decision-theoretic principles of a DSS are satisfied. This may be the best manner to proceed with the planning of a future
survey design, however it is a mathematically and numerically challenging exercise.
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Chang, Chun-Wei, and 張俊偉. "Power Output Prediction of Photovoltaic Power Systems by Using Multiple-Regression Models." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/61042087885764952237.
Повний текст джерелаАнотація:
碩士健行科技大學
電機工程系碩士班
102
Solar irradiations and cell temperatures are required for traditional photovoltaic cell model to estimate the cell power output. However, the cell temperatures cannot be obtained before building the photovoltaic systems. Hence, only solar irradiation is usually used to predict the cell power, it brings bigger error at higher temperature. In this article, multiple-regression models are proposed to predict the power output of photovoltaic systems. The independent variables of these models may include solar irradiation, ambient temperature and wind speed. The weather hourly data can be obtained in advance from Bureau of Meteorology. Test results indicate that the predictive error can be lowed 16.7% by using the proposed multiple-regression models when compared with that of single solar irradiation regression.
43
Sajadian, Sally. "Energy conversion unit with optimized waveform generation." Thesis, 2014. http://hdl.handle.net/1805/6109.
Повний текст джерелаАнотація:
Indiana University-Purdue University Indianapolis (IUPUI)The substantial increase demand for electrical energy requires high efficient apparatus dealing with energy conversion. Several technologies have been suggested to implement power supplies with higher efficiency, such as multilevel and interleaved converters. This thesis proposes an energy conversion unit with an optimized number of output voltage levels per number of switches nL=nS. The proposed five-level four-switch per phase converter has nL=nS=5/4 which is by far the best relationship among the converters presented in technical literature. A comprehensive literature review on existing five-level converter topologies is done to compare the proposed topology with conventional multilevel converters. The most important characteristics of the proposed configuration are: (i) reduced number of semiconductor devices, while keeping a high number of levels at the output converter side, (ii) only one DC source without any need to balance capacitor voltages, (iii) high efficiency, (iv) there is no dead-time requirement for the converters operation, (v) leg isolation procedure with lower stress for the DC-link capacitor. Single-phase and three-phase version of the proposed converter is presented in this thesis. Details regarding the operation of the configuration and modulation strategy are presented, as well as the comparison between the proposed converter and the conventional ones. Simulated results are presented to validate the theoretical expectations. In addition a fault tolerant converter based on proposed topology for micro-grid systems is presented. A hybrid pulse-width-modulation for the pre-fault operation and transition from the pre-fault to post-fault operation will be discussed. Selected steady-state and transient results are demonstrated to validate the theoretical modeling.
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Kosterev, Dmitry N. "Planning for controllable network devices in power transmission systems." Thesis, 1996. http://hdl.handle.net/1957/34617.
Повний текст джерелаАнотація:
The full capacity of the existing transmission lines is often underutilized
due to the system stability requirements. Controllable network devices represent
the effective means of improving the system stability, and their deployment allows
better use of the existing transmission facilities and can help to avoid construction of
new lines. This dissertation addresses system analysis and modeling of controllable
network devices.
Transient angle stability is one of the major requirements limiting transfer
capability of the power transmission systems. The theoretical concepts of transient
angle controllability using controllable network devices are considered in this dissertation.
The main results are derived for a general transmission network structure
and applied to series and shunt compensators as well as braking resistors. The
proposed approach allows to quantify controllability and to relate it to the control
device size, type and location in the transmission network.
Transient stability controllers are needed to maximize the device effect on the
transient angle stability enhancement. The transient stability controller functional
structure is discussed and the design requirements for each component are specified.
The examples of controller designs are presented.
Emerging technologies such as Thyristor-Controlled Series Compensators and
Synchronous Voltage Sources offer superior control capabilities and performance
characteristics as compared to conventional compensators. Unlike conventional compensators,
the new controllable network devices are very complex dynamical systems
and require more comprehensive modeling for time-domain studies and controller
designs. Detailed models of a Thyristor-Controlled Series Compensator and a Synchronous
Voltage Source for powerflow, transient stability, and electro-magnetic
transient studies are presented.
Finally, a detailed planning study for increasing transfer capability of the
Montana transmission system using controlled series compensation is presented. A
variety of design and performance requirements is considered in this study, which
makes it a useful reference for similar planning projects.Graduation date: 1996
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Vedam, Rajkumar. "Nonlinear control applied to power systems." Thesis, 1994. http://hdl.handle.net/1957/35510.
Повний текст джерелаАнотація:
When large disturbances occur in interconnected power systems, there exists the danger
that the power system states may leave an associated region of stability, if timely corrective action
is not taken. Open-loop remedial control actions such as field-forcing, line-tripping, switching of
series-capacitors, energizing braking resistors, etc., are helpful in reducing the effects of the
disturbance, but do not guarantee that the post-fault power system will be stabilized. Linear
controllers are widely used in the power industry, and provide excellent damping when the power
system state is close to the equilibrium. In general, they provide conservative regions of stability.
This study focuses on the development of nonlinear controllers to enhance the stability of
interconnected power systems following large disturbances, and allow stable operation at high
power levels.
There is currently interest in the power industry in using thyristor-controlled series-capacitors
for the dual purpose of exercising tighter control on steady-state power flows and
enhancing system stability. This device is used to implement the nonlinear controller in this
dissertation. A mathematical model of the power system controlled by the thyristor-controlled
series-capacitor is developed for the purpose of controller design.
Discrete-time, nonlinear predictive controllers are derived by minimizing criterion
functions that are quadratic in the output variables over a finite-horizon of interest, with respect to
the control variables. The control policies developed in this manner are centralized in nature. The
stabilizing effect of such controllers is discussed. A potential drawback is the need to have large
prediction horizons to assure stability. In this context, a coordinated-control policy is proposed, in
which the nonlinear predictive controller is designed with a small prediction horizon. For a class of
disturbances, such nonlinear predictive controllers return the power system state to a small
neighborhood of the post-fault equilibrium, where linear controllers provide asymptotic
stabilization and rapid damping. Methods of coordinating the controllers are discussed. Simulation
results are provided on a sample four-machine power system model.
There exists considerable uncertainty in power system models due to constantly shifting
loads and generations, line-switching following disturbances, etc. The performance of fixed-parameter
controllers may not be good when the plant description changes considerably from the
reference. In this context, a bilinear model-based self-tuning controller is proposed for the
stabilization of power systems for a class of faults. A class of generic predictive controllers are
presented for use with the self-tuning controller. Simulation results on single-machine and
multimachine power systems are provided.Graduation date: 1995
46
Gumede, Nkosinomusa S. "Eskom-ZESA interconnected power system modelling." Thesis, 2016. http://hdl.handle.net/10539/21110.
Повний текст джерелаАнотація:
A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering, 2016The power system frequency must be kept as close as possible to the nominal value. This is due to the inherent design of electrical equipment to operate efficiently at the nominal frequency. Frequency regulation in an interconnected power system is the duty of all members of the interconnection. However, in the Eskom-ZESA interconnected power system Eskom engineers ignore the contribution of the ZESA system to primary frequency control. This is mainly due to the prevalent assumption that the ZESA control area is small relative to the Eskom control area and its contribution to primary frequency control of the interconnected power system is negligible. This document presents a project that examines the validity of this assumption via determination of the contribution of the ZESA system to the interconnected power system’s primary frequency control. The interconnected power systems background was studied to understand the theory behind the operation of two or more interconnected power systems. System frequency disturbances deemed to be a good representation of the Eskom-ZESA interconnected power system’s performance were selected and analysed to validate the current assumption. The results show that there is a significant support from ZESA during a system frequency disturbance. This proves that the existing assumption is not valid anymore. Furthermore; the generator model that mimics the Eskom-ZESA tie-line governing behaviour was developed. Two different types of governor models were employed; firstly the IEEEG1 governor was tuned to control generator output to match the tie-line performance and then the TGOV5 governor model was used. The IEEEG1 governor model is a simplified governor representation; as a result, it is not easy to tune the parameters to match tie-line response. However, the performance is acceptable and it can be used to represent the tieline governor response. The TGOV5 governor model is very complex as discussed in section 4.2. The model includes boiler dynamics, and this improves performance such that it is possible to tune the parameters to follow the tie-line performance as close as necessary.
GR2016
47
"Distributed wireless utility maximization via fast power control." 2013. http://library.cuhk.edu.hk/record=b5549730.
Повний текст джерелаАнотація:
本论文开发出了一个全新的理论和算法框架用於无线网络的分布式功率控制。我们提出两种快速分布式功率控制算法，并对此作了深入的研究。 此种算法相当普适，比如适用于目前热门的LTE和认知无线电网络。 它在解的最优性以及收敛速度等方面击败了著名的高通公司的"荷载溢出型分布式功率控制算法" (收录于重要论文[HandeRanganChiangWu08] )以及"分布式加权比例型信干噪比均衡算法" (收录于重要论文[TanChiangSrikant 11)。作为一个重要而富有挑战性的研究课题，通过分布式功率控制达至无线网络效用的最大化一直受到业界的普遍关注。 这方面的研究通常把问题表述为一个最优化问题，即在某些功率约束条件下，优化整体系统的效用函数。 (其中，系统的效用函数通常是各无线收发链路的信干噪比的增函数。 )此问题已经有了不错的集中式解决方案，但成本更低廉、更易于布置、更为实用的分布式解决方案则欠奉，尤其是经严格证明可行的分布式解决方案。 这是因为分布式算法一般只适用于相对简单或者有特殊结构的优化问题。 而无线设备之间的相互干扰和各自信号功率之间的复杂关系使得分布式求解极其困难。 在算法设计上，很小的疏漏就可能导致解决方案无效或者不收敛。 例如，尽管论文[HandeRanganChiangWu08] 和[TanChiangSrikant 11] 都声称各自的分布式算法提供了问题的最优解，但我们通过大量的仿真实验以及理论研究发现并非如此。 我们发现"荷载溢出型分布式功率控制算法"时常要么无法收敛，要么收敛得极其慢。而"分布式加权比例型信干噪比均衡算法"则经常在几次迭代之後就已经发散。
我们开发出了全新的分析和算法框架，并将其推广到适用于一般线性功率约束的情况。(前述论文的分析框架是基于某些非常特殊的线性功率约束。)在此基础上，我们逐一找出了前述算法中的错漏之处，并设计出我们的分布式梯度投影功率控制算法，以及与之相匹配的步长规则。 我们严格证明了该步长规则的有效性和算法的收敛性、最优性，并给出了算法复杂度的分析。(相较之下， [HandeRanganChiangWu08] 在算法收敛性证明上语焉不详，在其它方面则付之阙如;而[TanChiangSrikant 11] 的算法收敛性证明存在明显错误，在其它方面同样付之阙如。 )在某些情况下，我们的算法可以进一步提速并提升运行性能。 大量的仿真实验证实我们的算法在解的最优性和运行速度两方面都较前述算法优越。在某些情况下，我们算法的收敛速度上百倍快于前述算法。
总而言之，本论文成功解决了重要的效用优化问题并取得比前述论文更好的结果。它开发出全新的理论和算法框架，完全解决了步长规则和收敛性、最优性这些难题。展望未来，我们相信，本论文为快速功率控制在无线和移动解决方案中的应用打下了坚实的理论基础。 我们期待该理论框架能够提供更多問題的解決方案。
This thesis develops a new theoretical and algorithmic framework for practical distributed power control in wireless networks. It proposes and investigates fast optimal distributed power control algorithms applicable to LTE as well as cognitive radio. The proposed algorithms beat the well-known Qualcomm's load-spillage distributed power control algorithm in [HandeRan-ganChiangWu08] and the distributed weighted proportional SINR algorithm in [TanChiangSrikant11] in terms of both the optimality of the solution and the convergence speed.
Wireless network utility maximization via distributed power control is a classical and challenging issue that has attracted much research attention. The problem is often formulated as a system utility optimization problem under some transmit power constraints, where the system utility function is typically an increasing function of link signal-to-interference-plus-noise-ratio (SINR). This problem is complicated by the fact that these wireless devices may interfere with each other. In particular, the wireless devices are affected by each other's transmit power, and the transmit powers and interferences experienced by the devices are interwoven in a complex manner.
Despite that, there have been good centralized algorithms for solving the problem. "Decentralized" solutions, on the other hand, are a different story. In practice, decentralized algorithms in which the devices interact with each other in a loosely coupled manner to improve the network utility, are easier to deploy than centralized algorithms. However, the design of workable (and provably workable in the mathematical sense) solution is very challenging. Small neglects can lead to solutions that are invalid or non-convergent. For example, although both papers [HandeRanganChiangWu08] and [TanChiangSrikant11] claim their distributed algorithms to be optimal, we discover some experimental evidence suggesting that certain parts of these algorithms are not quite right. Oftentimes, the former fails to converge or converges extremely slowly, while the latter could diverge in the first few iterations.
To fix these glitches and to broaden the scope of the problem, we develop a new analytical and algorithmic framework with a more general formulation. With this framework, we can identify the sources of the defects and shortcomings of prior algorithms. We further construct an optimal distributed (sub)gradient projection algorithm with provably valid step size rules. Rigorous convergence proof and complexity analysis for our algorithm are given (note: convergence proof and complexity analysis were missing in [HandeRanganChiangWu08] and incorrect in [TanChiangSrikant11]). In some scenarios, our algorithm can be further accelerated to yield even better performance. Extensive simulation experiments confirm that our algorithms always outperform the prior algorithms, in terms of both optimality and efficiency. Specifically, simulation demonstrates at least 100 times faster convergence than the prior algorithms under certain scenarios.
In summary, this thesis solves the important SINR-based utility maximization problem and achieves significantly better results than existing work. It develops a new theoretical an dalgorithmic framework which completely addresses the difficult convergence and step-size issues. Going forward, we believe the foundation established in this work will open doors to other fast distributed wireless and mobile solutions to problems beyond the power control problem addressed here.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Zhang, Jialiang.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2013.
Includes bibliographical references (leaves 83-87).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstract also in Chinese.
Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Overview --- p.1
Chapter 1.2 --- Thesis Organization --- p.6
Chapter 1.3 --- Notations --- p.7
Chapter 2 --- System Model and Problem Formulation --- p.8
Chapter 2.1 --- System Model --- p.8
Chapter 2.2 --- Nonnegative Linear Power Constraints --- p.9
Chapter 2.3 --- Network Utility --- p.10
Chapter 2.4 --- Problem Formulation --- p.11
Chapter 2.5 --- Characterization of T[subscript c] --- p.13
Chapter 2.6 --- Multiple Constraints --- p.16
Chapter 3 --- Nice Properties of SINR Constraints --- p.18
Chapter 3.1 --- Convexity, Differentiability and Monotonicity --- p.19
Chapter 3.2 --- Fast Distributed Gradient Computation --- p.20
Chapter 3.2.1 --- Distributed SINR-Driven Single-Constrained Power Control --- p.21
Chapter 3.2.2 --- Network Duality --- p.23
Chapter 3.3 --- The Case of Multiple Constraints --- p.27
Chapter 4 --- Network Utility Maximization in Log-SINR Domain --- p.32
Chapter 4.1 --- Single Active Constraint and Ascent Directions --- p.34
Chapter 4.2 --- Multiple Constraints and Subgradient Projection --- p.39
Chapter 4.3 --- Unconstrained Equivalence and Complexity results of M = 1 --- p.46
Chapter 4.4 --- Simulation Experiments --- p.52
Chapter 4.4.1 --- Simulation Settings --- p.52
Chapter 4.4.2 --- Negative results of algorithm 6 in [7] --- p.54
Chapter 4.4.3 --- Negative results of Qualcomm’s load-spillage algorithm in [25] --- p.56
Chapter 4.4.4 --- More results of our algorithms --- p.62
Chapter 5 --- Related Work --- p.64
Chapter 6 --- Conclusion --- p.68
Chapter 7 --- Appendix --- p.72
48
Al-Baroudi, Homan Mohammed-Zahid. "Experimental simulations of a rotating bubble membrane radiator for space nuclear power systems." Thesis, 1993. http://hdl.handle.net/1957/36233.
Повний текст джерелаАнотація:
A rotating, flat plate condensation experiment has been developed to
investigate the heat of the Rotating Bubble Membrane Radiator (RBMR). The
RBMR is a proposed heat rejection system for space applications which uses
working fluid condensation on the inside surface of a rotating sphere to
reject heat to space. The flat plate condensation heat transfer
experiment simulates the microgravity environment of space by orienting
the axis of rotation parallel to the gravitational vector and normal to
the surface of the plate. The condensing surface is cooled to simulate the
rejection of heat to cold surface. The working fluid is a super heated
steam.
The results obtained include relationships between the overall heat
transfer coefficient as a function of the temperature difference between
the working fluid and a cold environment, both placed in dimensionless
groups, and plate angular rotational speeds. This empirical relationship
is useful for choosing the optimum rotational speed for the flat plate
radiator given a desired heat rejection load.
A RBMR prototype, using full sphere shell, was designed and built
completely in this research efforts and ready to be tested in future
planned experiments in microgravity environment. This RBMR is the first
one ever built to investigate the RBMR concepts experimentally.
This study also provides the basis for designing new heat rejection
systems utilizing centrifugal forces and condensation phenomena in both
space and ground applications.Graduation date: 1993
49
Ye, Chun. "On the Trade-offs between Modeling Power and Algorithmic Complexity". Thesis, 2016. https://doi.org/10.7916/D87W6CDC.
Повний текст джерелаАнотація:
Mathematical modeling is a central component of operations research. Most of the academic research in our field focuses on developing algorithmic tools for solving various mathematical problems arising from our models. However, our procedure for selecting the best model to use in any particular application is ad hoc. This dissertation seeks to rigorously quantify the trade-offs between various design criteria in model construction through a series of case studies. The hope is that a better understanding of the pros and cons of different models (for the same application) can guide and improve the model selection process.
In this dissertation, we focus on two broad types of trade-offs. The first type arises naturally in mechanism or market design, a discipline that focuses on developing optimization models for complex multi-agent systems. Such systems may require satisfying multiple objectives that are potentially in conflict with one another. Hence, finding a solution that simultaneously satisfies several design requirements is challenging. The second type addresses the dynamics between model complexity and computational tractability in the context of approximation algorithms for some discrete optimization problems. The need to study this type of trade-offs is motivated by certain industry problems where the goal is to obtain the best solution within a reasonable time frame. Hence, being able to quantify and compare the degree of sub-optimality of the solution obtained under different models is helpful. Chapters 2-5 of the dissertation focus on trade-offs of the first type and Chapters 6-7 the second type.
50
"Online energy generation scheduling for microgrids with intermittent energy sources and co-generation." 2013. http://library.cuhk.edu.hk/record=b5884470.
Повний текст джерелаАнотація:
Lu, Lian.Thesis (M.Phil.)--Chinese University of Hong Kong, 2013.
Includes bibliographical references (leaves 91-95).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.