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Sheard, Benjamin Charles De Villiers. "An electrical power system for CubeSats." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/20101.
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The advent of CubeSats has provided a platform for relatively low-budget programmes to realise space missions. In South Africa, Stellenbosch University and the Cape Peninsula University of Technology have impressive space programmes and have been involved in numerous successful satellite launches. A number of CubeSat projects are currently in progress and commercial-grade Attitude Determination and Control Systems (ADCS), and communications modules, are being developed by the respective universities. The development of a CubeSat-compatible Electrical Power System remains absent, and would be beneficial to future satellite activity here in South Africa. In this thesis, some fundamental aspects of electronic design for space applications is looked at, including but not limited to radiation effects on MOSFET devices; this poses one of the greatest challenges to space-based power systems. To this extent, the different radiation-induced effects and their implications are looked at, and mitigation strategies are discussed. A review of current commercial modules is performed and their design and performance evaluated. A few shortcomings of current systems are noted and corresponding design changes are suggested; in some instances these changes add complexity, but they are shown to introduce appreciable system reliability. A single Li-Ion cell configuration is proposed that uses a 3.7 V nominal bus voltage. Individual battery charge regulation introduces minor inefficiencies, but allows isolation of cells from the pack in the case of cell failure or degradation. A further advantage is the possibility for multiple energy storage media on the same power bus, allowing for EPS-related technology demonstrations, with an assurance of minimum system capabilities. The design of each subsystem is discussed and its respective failure modes identified. A limited number of single points of failure are noted and the mitigation strategies taken are discussed. An initial hardware prototype is developed that is used to test and characterise system performance. Although a few minor modifications are needed, the overall system is shown to function as designed and the concepts used are proven.
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Lehr, Rainer Helmut. "Web based distance learning for power system engineering." Master's thesis, University of Cape Town, 2000. http://hdl.handle.net/11427/5186.
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Bazrafshan, Mohammadhafez. "Modeling and Optimization of Electrical Power Networks." Thesis, The University of Texas at San Antonio, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10929124.
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<p> The electrical power network is moving towards sustainability and cost-efficiency. The former is achieved by incorporating distributed renewable generation and the latter requires employing intelligent control and optimization techniques. As the main interface between the electricity grid and its consumers, the distribution network will play a pivotal role in the near future. In practice, distribution networks operate under unbalanced conditions and far from single-phase simplifications. Thus, the majority of this dissertation aims to provide comprehensive computational tools for multi-phase distribution networks. A final part of this work touches upon transmission networks to explore benefits of combining control and optimization algorithms in various time-scales. </p><p> In Chapter 2, models of the most practical distribution elements, including wye and delta ZIP loads, transmission lines with missing phases, step-voltage regulators (SVRs), and three-phase transformers are assembled. Specifically for SVRs, novel nodal admittance models are derived from first principles. Concatenation of these models yields the bus admittance matrix (Y-Bus). Using linear algebra, it is then shown that Y-Bus invertibility is compromised only when the network includes ungrounded or delta-connected transformers. For such devices, we mathematically show why a previously proposed modification in their nodal admittance restores Y-Bus invertibility. Mathematical guarantees for Y-Bus invertibility is important since, for instance, it allows one to run the Z-Bus method to compute voltage solutions of power flow equations. </p><p> In Chapter 3, theoretical convergence of the Z-Bus method in multi-phase distribution networks with wye and delta ZIP loads is studied. By viewing the Z-Bus method as a fixed-point iteration, sufficient conditions for its contraction are derived. These conditions define a region, expressed in terms of Y-Bus and ZIP loads, in which unique voltage solutions to power flow equations exist. </p><p> Chapter 4 considers a planning problem for inverter-based renewable systems in multi-phase distribution networks. The objective is to minimize the installation costs of distributed generators (DG) during the planning stage and the costs of power import plus DG curtailment during operations. Three- and single-phase inverter models that preserve the underlying mapping between renewable uncertainty to power injection are presented. Scenario-based characterization of distributed generation and loads as well as power flow linearizations are leveraged to render a stochastic formulation for optimal DG placement and sizing. The proposed problem is a mixed-integer second-order cone program that is solved efficiently. Simulations on several medium-to-large-sized distribution test feeders promise that optimal stochastic planning of DGs reduces costs during validation, compared to a scheme where uncertainty is only represented by its average value. </p><p> Chapter 5 presents an optimal power flow (OPF) problem that allows for tap selection of various types of SVRs. The goal is to minimize power import while satisfying operational constraints. A set of power flow equations are derived that explicitly account for the tap ratios based on the nodal admittance model of SVRs (Chapter 2). Chordal semidefinite relaxations of the power flow equations are pursued for non-SVR edges. For each SVR type, novel relaxations are proposed to handle the non-convex primary-to-secondary voltage relationship. The formulation is a semidefinite program (SDP). Numerical tests on the IEEE 37-bus distribution feeder indicate the success of the proposed SDP in selecting taps of wye, closed-delta, and open-delta SVRs. </p><p> Chapter 6 augments the transmission OPF problem with a load-following controller whose costs are expressed through the linear quadratic regulator (LQR). The power network is described by a set of nonlinear differential algebraic equations (DAEs). By linearizing the DAEs around a known equilibrium, a linearized OPF with operational constraints is formulated first. This OPF is then augmented by a set of linear matrix inequalities equivalent to the implementation of an LQR controller. The resulting formulation, termed LQR-OPF, is an SDP which furnishes optimal steady-state setpoints and an optimal feedback law to steer the system to the new steady state with minimum load-following control costs. Experiments on test cases demonstrate that the setpoints computed by LQR-OPF result in lower overall costs and frequency deviations compared to those of a scheme where OPF and load-following control are considered separately.</p><p>
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Yang, Xiaoguang Miu Karen Nan. "Unbalanced power converter modeling for AC/DC power distribution systems /." Philadelphia, Pa. : Drexel University, 2006. http://hdl.handle.net/1860/1231.
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Kyaw, Phyo Aung. "Efficient Power-Dense Passive Components for Next-Generation High-Frequency Power Conversion." Thesis, Dartmouth College, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10978933.
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<p> Advancements in energy systems and electric vehicles have increased demands for efficient and compact power electronics. High-frequency operation is important for miniaturization of switching power converters since it reduces energy storage requirement and improves transient performance. Wide-bandgap semiconductors allow for efficient high-frequency switching, but full realization of their potential in power electronics requires efficient power-dense high-frequency passive components. Magnetic components such as inductors and transformers, due to their frequency-dependent losses, are increasingly the main bottleneck in improving the density of power converters. </p><p> Although incremental improvements in magnetics, and passives in general, are enabling advances in power electronics, the importance of the problem merits consideration of the fundamental performance limits and exploration of alternative passive component technologies. Analysis of various energy storage mechanisms indicates the potential of mechanical storage coupled with a piezoelectric transduction mechanism. Optimally designed piezoelectric and electromagnetic resonators, in ideal scenarios, are capable of orders-of-magnitude higher power density than passive components in use today. Investigation of various practical limitations provides insights into possible technological development for improving the performance of passive components and switching converters. </p><p> High-performance resonant tanks and power converters are also presented. First, an integrated LC resonator with a multilayer foil winding demonstrates 50% better performance compared to a similar resonator with a single-layer skin-effect limited winding. Second, an optimally designed integrated LC resonant tank, made of commercial Class I ceramic capacitors, has a sub-m? effective series resistance and incurs only 4.56 W loss, resulting in a 7.42 kW power capability in a small 1.14 cm<sup>3</sup> volume. The high performance means that a power converter utilizing these prototype resonators will be limited by the performance of switches rather than by the passive component. Finally, a prototype 48 V to 16 V stacked-ladder converter, with a high active device utilization figure of merit, combined with a small low-loss integrated resonator, provides a peak efficiency of 97.8% and a high power density of 913 W/in<sup>3</sup>. The theoretical analysis, together with these prototypes, shows the potential for significant improvement in the efficiency and power density of high-frequency switching converters, and the various technological developments required to achieve such improvements.</p><p>
6
Tai, Sio Un. "Power quality study in Macau and virtual power analyzer." Thesis, University of Macau, 2012. http://umaclib3.umac.mo/record=b2586277.
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Fernando, Warnakulasuriya A. M. "Power quality improvement in power systems using a static VAR compensator." Thesis, California State University, Long Beach, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10638886.
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<p> The primary purpose of a power system is to transform energy from one of its naturally obtainable forms into electricity, and then supply it through grids to points of consumption. With the increasing demand for electricity, more reliable methods are required to keep the quality of power in the desired range. This paper focuses on the impacts that a static var compensator (SVC) has on power quality. A two-area power system was used to demonstrate the power quality enhancements of a SVC, and simulations were done on the Real Time Digital Simulator (RTDS) and Electrical Transients Analyzer Program (ETAP). Simulations were performed for both steady-state and transient conditions to exhibit the dynamic capabilities of a SVC. Also, two different types of SVC controls were used and their effectiveness was analyzed. Simulations showed that the steady-state voltage, namely at bus 8 where the SVC was installed, improved from 0.94pu to 1.0pu. In addition, the voltage recovery time of bus 8 was improved from over 40s to approximately 2s.</p><p>
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Villanueva, Anita A. (Anita Ariel) 1978. "Electrical reliability of RF power GaAs PHEMTs." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/87862.
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Tiako, Remy. "Optimal design of power system stabilizer (PPS) using multi-power flow conditions." Master's thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/5096.
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Lam, Chi Seng. "An adaptive low dc-voltage controlled LC coupling hybrid active power filter in three-phase four-wire power systems." Thesis, University of Macau, 2012. http://umaclib3.umac.mo/record=b2580608.
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Niemelä, Elvira, and Lucas Wallhager. "Fast Power Support of Electrical Batteries in Future Low Inertia Power Systems." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-281935.
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To create more sustainable power systems, as well as achieve environmental goals, further integration of Renewable Energy Sources (RES) is essential. However, this may result in a power system more vulnerable to disturbances, since RES do not contribute to the system’s inertia. A power system’s ability to counteract disturbances is highly dependant on inertia. This is because the power system uses the kinetic energy of rotating machines, i.e. inertia, to restore the power balance after a disturbance. This causes a deviation of the system’s frequency, which must be contained within certain limits or, in the worst case scenario, a blackout could follow. Frequency Containment Reserves (FCR) stabilizes the frequency first dozens of seconds after a disturbance, therefore, it is the inertia that plays the major role in controlling the initial frequency deviation. One possibility to counter disturbances in a power system with less inertia is to use electrical batteries as fast power support, by injecting power into the system when needed. This project aims to investigate the dynamics of the FCR as well as the possibility to use batteries as fast power support. Different parameters of the batteries are also analyzed. The project is conducted through a case study of a power system model in Simulink and Matlab. Additional aspects, such as sustainability, cost-effectiveness, and future research, are discussed.<br>För att skapa mer hållbara kraftsystem, men även uppnå miljömål, är fortsatt integrering av förnyelsebara energikällor viktigt. Dock kan detta resultera i ett kraftsystem som är mer sårbart mot störningar, då förnyelsebara energikällor inte bidrar till systemets svängmassa. Ett kraftsystems förmåga att möta störningar är direkt relaterad till svängmassan i systemet. Detta är på grund av att systemet använder kinetisk energi från roterande maskiner, deras svängmassa, för att återställa balans mellan produktion och konsumtion efter en störning. Dock orsakar detta en avvikelse hos systemets frekvens, som måste hållas inom vissa gränser, annars kan det i värsta fall leda till strömavbrott. Primärreglering stabiliserar frekvensen först dussin sekunder efter en störning, därför är det svängmassan som spelar den avgörande rollen för att kontollera den initiella avvikelsen. En möjlig lösning för att möta störningar i ett kraftsystem med mindre svängmassa är att använda elektriska batterier som snabbt kraftstöd, genom att tillföra effekt till systemet vid behov. Detta projekt syftar till att undersöka dynamiken hos primärregleringen men även huruvida batterier kan användas som snabbt kraftstöd. Olika parametrar hos batterierna analyseras även. Projektet görs genom en fallstudie av en model av ett kraftsystem i Simulink och Matlab. Andra aspekter, så som hållbarhet, kostnadseffektivitet samt framtida forskning diskuteras.
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Boesak, Dawid John Johannes. "Voltage stability analysis of a power system network comprising a nuclear power plant." Master's thesis, Faculty of Engineering and the Built Environment, 2018. http://hdl.handle.net/11427/30056.
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As recently as 2016, the performance of South Africa’s power utility has shown that it is not resilient enough to withstand the consequences of a power system blackout. Blackouts are defined as being a form of power system instability that can be brought about by a variety of abnormal network scenarios. The most common modes of failure are grouped under the term power system stability. In this dissertation, the different modes of power stability that can affect a nuclear power station will be investigated and discussed. The particular phenomenon that will be focused on, however, is the effect that voltage instability has on the ability of generators and loads to perform their standard functions, thus ensuring a secure power system. To investigate the effect that voltage instability has on a nuclear power station, this dissertation will look at relevant literature on the topic. In addition, by extracting from common examples of national and international occurrences of voltage stability, this dissertation will record the effects that this phenomenon has on the security of a power system, in particular on nuclear power plants. To model the network containing a nuclear power plant for the evaluation of voltage stability, the different mathematical models of the generation plant are presented, which include: the automatic voltage regulator, power system stabilizer, governor, nuclear reactor, and excitation system. Also presented are mathematical models of network equipment such as under voltage tap changers and the dynamic loads that are of interest when evaluating voltage stability. The models used for evaluation of the voltage stability phenomenon affecting a nuclear power plant and the surrounding integrated power system are built in the Digsilent PowerFactory® software. The scenario for evaluation is based on a voltage stability event that occurred around at the Koeberg nuclear power system situated in the Western Cape province on South Africa on 15 October 2003. It is commonly accepted that voltage stability can be evaluated at a steady state level by performing power versus voltage (PV) analysis to determine the voltage buses vulnerable to voltage collapse, and reactive power versus voltage (QV) analysis to determine the critical reactive devices required to avert a voltage instability event. The scenarios that are evaluated for voltage stability are divided into two sections: i) a PV and QV analysis as per the event that occurred on 15 October 2003 and ii) present-day voltage stability indices for PV and QV if mixed with a generation such as renewable energy sources that include wind, solar, biomass and concentrated solar power (CSPs). The result reveals the vulnerabilities of the nuclear power plant and the surrounding integrated power system due to a voltage instability event. Some of the solutions proposed include a review of the typical power system protection schemes — such as under and overvoltage detection scheme — that are used. In the study, PV and QV curves provide v good indications of the state of critical busbars and the reactive power reserve margins available before instability can potentially settle in. Simulations confirmed the effectiveness of critical equipment installed in the Western Grid and the effect on their electrical parameters such as torque and the slip on motors.
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Malengret, Michel. "Definition of apparent power in 3-phase 4-wire non-sinusoidal power systems." Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/5174.
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Includes abstract.<br>Includes bibliographical references (leaves 120-125).<br>The thesis starts by collating and comparing most power theories in the instantaneous and average power domain. The instantaneous theories are reformulated and classified into three groups, which can be linked with one equation. Introducing a new instantaneous theory based on vector space allows the fundamental properties of the groups to be examined and provides the means to extend instantaneous power into the rms domain and calculate the compensating currents required. The approach results in power components that can be attributed a real physical interpretation. The new approach to three phase power theory has significant potential for education, the practical design of active compensators, and the revision of international standard definitions of power.
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Lao, Keng Weng. "A novel electric traction power supply system using hybrid parallel power quality compensator." Thesis, University of Macau, 2011. http://umaclib3.umac.mo/record=b2550461.
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Olofsson, Magnus. "Power Flow Analysis of the Swedish Railway Electrical System." Licentiate thesis, Stockholm, 1993. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-223934.
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This thesis deals with analysis of the steady state power flow in the Swedish railway electrical system. Finding the steady state of the system means that all voltages and power flows in the system are known. The trains are supplied from the public grid using frequency converters. This is the major difference compared with ordinary power systems fed from turbine-driven generators. The output voltage phase shift function for the converters is important in the mathematical formulation of the problem. In the system, the locomotives are almost entirely of the Re-type, having a rectifier and d.c.-motors. The fundamental frequency reactive power need is thereby dependent on the train speed, wheel power and line voltage. In this thesis, the converters and thyristor locomotives are modelled and included in the load flow formulation. The method is shown to have good convergence properties. An approximate and fast method for the calculation of the power injections from converters is presented. A necessary condition for this approximate method to be valid is that the converters are strongly interconnected. The construction of a new 130 kV line brings the converters close to each other electrically. Energy input from each of the converters inthe system can be simulated calculating repeated load flows. Measurements in a real system have verified the applicability of the proposed load flow method. Examples of areas where the method can be used are system studies and optimal control of the system. The locomotives act as sources of harmonic currents. In an extended load flow formulation this is taken into account. The fundamental idea behind the method is that harmonic powers caused by the thyristor bridges at first are transferred as fundamental frequency active power from the sinusoidal voltage sources. The method thus gives the fundamental frequency powers injected from the sinusoidal voltage sources to the network. Comparisons with time simulations with detailed models show good agreement.
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Noble, Michael Lynn. "Preliminary design of the PANSAT electrical power subsystem." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA236911.
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Thesis (M.S. in Electrical Engineering (Space Systems Engineering))--Naval Postgraduate School, June 1990.<br>Thesis Advisor(s): Ewing, Gerald R. Second Reader: Panholzer, Rudolf. "June 1990." Description based on signature page as viewed on October 20, 2009. DTIC Indicator(s): Electrical Power Supplies, Solar arrays, Petite satellites, Amateur satellites, DC DC Converters. Author(s) subject terms: PANSAT satellite, electrical power system, battery charge regulator. Includes bibliographical references (p. 111-114). Also available online.
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Suwanapingkarl, Pasist. "Power quality analysis of future power networks." Thesis, Northumbria University, 2012. http://nrl.northumbria.ac.uk/12625/.
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Dancy, Abram P. (Abram Paul). "Power supplies for ultra low power applications." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10069.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.<br>Includes bibliographical references (p. 101-103).<br>by Abram P. Dancy.<br>M.Eng.
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Pan, Haibo 1973. "SMES for power quality improvement and uninterruptible power supply." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33342.
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The history of applied superconductor-based equipment in industry, especially in power system, is briefly reviewed. The thesis presents a development of a superconducting magnetic energy storage system for power quality improvement and uninterruptible power supply (PQ/UPS SMES). The configuration of such a system and its control concept are analyzed in full details. Evaluation tests of an SMES system operating on a simple power system are presented and analyzed. They validate the applicability of such a system, as an attractive alternative for power quality improvement and uninterruptable power supply.<br>The PQ/UPS SMES system as well as the power network has been modeled using Matlab/Simulink simulation environment for convenience. The Simulink models of all relevant components are also presented. Finally, all the evaluation tests are also done in Simulink simulation environment.
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Khayat, Moghaddam Elham. "On low power test and low power compression techniques." Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/997.
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With the ever increasing integration capability of semiconductor technology, today's large integrated circuits require an increasing amount of data to test them which increases test time and elevated requirements of tester memory.
At the same time, as VLSI design sizes and their operating frequencies continue to increase, timing-related defects are high proportion of the total chip defects and at-speed test is crucial. DFT techniques are widely used in order to improve the testability of a design. While DFT techniques facilitate generation and application of tests, they may cause the test vectors to contain non-functional states which result in higher switching activities compared to the functional mode of operation. Excessive switching activity causes higher power dissipation as well as higher peak supply currents. Excessive power dissipation may cause hot spots that could cause damage the circuit. Excessive peak supply currents may cause higher IR drops which increase signal propagation delays during test causing yield loss.
Several methods have been proposed to reduce the switching activity in the circuit under test during shift and capture cycles. While these methods reduce switching activity during test and eliminate the abnormal IR drop, circuits may now operate faster on the tester than they would in the actual system. For speed related and high resistance defect mechanisms, this type of undertesting means that the device could be rejected by the systems integrator or by the end consumer and thus increasing the DPPM of the devices. Therefore, it is critical to ensure that the peak switching activity generated during the two functional clock cycles of an at-speed test is as close as possible to the functional switching activity levels specified for the device.
The first part of this dissertation proposes a new method to generate test vectors that mimic functional operation from the switching activity point of view. It uses states obtained by applying a number of functional clock cycles starting from the scan-in state of a test vector to fill unspecified scan cells in test cubes. Experimental results indicate that for industrial designs, the proposed techniques can reduce the peak capture switching on average by 49% while keeping the quality of test very close to conventional ATPG.
The second part of this dissertation addresses IR-drop and power minimization techniques in embedded deterministic test environment. The proposed technique employs a controller that allows a given scan chain to be driven by either the decompressor or pseudo functional background. Experimental results indicate an average of 36% reduction in peak switching activity during capture using the proposed technique.
In the last part of this dissertation, a new low power test data compression scheme using clock gater circuitry is proposed to simultaneously reduce test data volume and test power by enabling only a subset of the scan chains in each test phase. Since, most of the total power during test is typically in clock tree, by disabling significant portion of clock tree in each test phase, significant reduction in the test power in both combinational logic and clock distribution network are achieved. Using this technique, transitions in the scan chains during both loading of test stimuli and unloading of test responses decrease which will permit increased scan shift frequency and also increase in the number of cores that can be tested in parallel in multi-core designs. The proposed method has the ability of decreasing, in a power aware fashion, the test data volume. Experimental results presented for industrial designs demonstrate that on average reduction factors of 2 and 4 in test data volume and test power are achievable, respectively.
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Mutha, Shashank. "Adaptive Linearization of Power Amplifiers." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1244049195.
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Gunda, Rahul. "Performance analysis of high power photoconductive switch at elevated temperature." Diss., Columbia, Mo. : University of Missouri-Columbia, 2005. http://hdl.handle.net/10355/4310.
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Thesis (M.S.)--University of Missouri-Columbia, 2005.<br>The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (July 13, 2006) Includes bibliographical references.
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Oyedokun, David Temitope. "Power flow and rotor angle stability studies of HVAC-HVDC power system interconnections using DigSILENT." Master's thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/12367.
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Includes bibliographical references (leaves 143-147).<br>The backbone of all industrialised nations is the success of the power sector, which involves an efficient, reliable and secure means of power generation, transmission and distribution. Industrial growth and urbanisation have together endlessly stimulated electrical engineers to ensure that the electrical power needs of the society are met.
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Doorduin, Riaan. "Electricity theft detection on a low voltage reticulation environment." Thesis, Stellenbosch : University of Stellenbosch, 2004. http://hdl.handle.net/10019.1/16310.
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Thesis (MScIng)--University of Stellenbosch, 2004.<br>ENGLISH ABSTRACT: Electricity theft in South Africa has become a major problem. This led to several developments
from both industries and research institutes to counter these actions. Since equipment is already
installed and major capital has been invested to provide electricity for a broad spectrum
of consumers, the challenge is to find a low cost solution harnessing current investments and
technology to detect electricity theft more accurately.
This thesis investigates into the electricity theft topic. Two different methods, Time Domain
Pulse Reflectometry and a data driven platform based on the Theory of Constraints philosophy,
were investigated to provide means to detect and determine the impact of illegal electricity
usage. Both methods required detailed designs to conduct preliminary proof of concept tests in
a laboratory environment.
These methods are evaluated against their economical viability, possible practical implications
and applications. This thesis presents a practical approach to electricity theft detection
and provides the basic tools for management of this ever-increasing problem.<br>AFRIKAANSE OPSOMMING: Suid Afrika se elektrisiteit diefstal statistiek het die afgelope jare skrikwekkend gegroei. Dit het
die industrie genoop om baie meer navorsing in die area te doen. Met reeds gevestigde toerusting
en tegnologie om di´e energie medium so effektief moontlik te versprei, is die uitdaging juis
om ’n ekonomiese oplossing te vind om reeds beskikbare tegnologie¨e meer doeltreffend aan te
wend.
Die doel van die tesis is om die gebied van elektrisiteit diefstal na te vors. Twee verskillende
metodes is ondersoek, naamlik Tydgebied-pulse-reflektometrie en ’n informasie gebaseerde
stelsel wat op die Randvoorwaarde Teorie gebaseer is, om effektief die omvang van elektrisiteit
diefstal in ’n mikro, asook makro omgewing te bepaal. Die twee metodes is in ’n beheerde
omgewing getoets sodat die konsepte wat ontwikkel is bewys kon word.
Die metodes is ge-evalueer in terme van die ekonomiese lewensvatbaarheid daarvan met inagneming
van die praktiese implikasies. Die tesis bied bestuur die nodige kennis om elektrisiteit
diefstal in die praktyk doeltreffend die hok mee te slaan.
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Villanueva, Anita A. (Anita Ariel) 1978. "Electrical degradation mechanisms of RF power GaAs PHEMTs." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40547.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.<br>Vita.<br>Includes bibliographical references (p. 155-161).<br>GaAs Pseudomorphic High-Electron Mobility Transistors (PHEMTs) are widely used in RF power applications. Since these devices typically operate at high power levels and under high voltage biasing, their electrical reliability is of serious concern. Previous studies have identified several distinct degradation phenomena in these devices, but a complete picture has yet to be formed. In this study, we have carried out a comprehensive study of the mechanisms of electrical degradation on a set of experimental RF power GaAs PHEMTs (non-commercial devices provided by our sponsor, Mitsubishi Electric). A wide variety of electrical stressing experiments employing different conditions (varying temperature, bias, environment) were performed on these devices in order to monitor their degradation with stressing. Our general observations showed several forms of degradation, the most concerning being an increase in the drain resistance RD and a reduction in maximum drain current Imax. Contrary to what is often claimed in the literature, our experiments indicated that these forms of degradation were not driven by impact-ionization or hot-electron effects. Instead, we found the degradation to be strongly correlated with temperature, stressing environment, and drain-gate bias, which were all consistent with a corrosion mechanism. Via materials analysis we were able to confirm that the degradation of both RD and Imax were due to surface corrosion on the drain side of the device, albeit at different specific locations. The increase in RD was attributed to oxidation on the n+GaAs ledge, while the reduction in Imax was due to oxidation on the AlGaAs surface, closer to the gate.<br>(cont.) A recoverable negative shift in the threshold voltage VT and a permanent decrease in Rs were also observed during electrical stressing. The shift in VT was attributed to field-assisted tunneling of electrons out of traps under the gate, while the decrease in Rs was found to be consistent with recombination-induced annealing of defects on the source side of the device. Measurements were also performed to observe light emitted from the device during electrical stressing. The observed light-emission indicated that device degradation was proceeding in a highly non-uniform manner across the width of the device, due to a non-uniform electric field distribution. We attributed this to a non-uniform recess geometry across the device width. This suggested that it is important to ensure uniform geometry across the device width, in order to minimize non-uniformities in electric field distribution and enhance device reliability. The physical understanding developed in this work should be instrumental to identifying and addressing future reliability issues in RF power GaAs PHEMTs.<br>by Anita Villanueva.<br>Ph.D.
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Li, Jinbo 1961. "A study of reactive power dispatch under restructured power systems /." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80120.
Full textAbstract:
This thesis analyzes generator reactive power dispatch under restructured power systems from two different perspectives.<br>The first follows the two-step approach adopted by some electricity markets where first, the generators' real powers are dispatched in the energy market, followed by the dispatching of the generator reactive power support services in the ancillary services market.<br>Once the generators' real power has been dispatched in the energy market, the generators' reactive power is dispatched according to the minimization of a combination of multiple objectives: network MW loss cost, generator opportunity cost, and generator MW shift cost. The MW loss cost is represented as a function of bus voltage magnitudes and angles as well as the nodal prices in $/MWh found in the first step. Opportunity cost is represented as a function of the generator reactive powers, whose cost parameters are derived in terms of the MW dispatch, the MW nodal prices and the generators' capabilities. The generator shift cost is represented as a function of the generator real powers and the MW shift weighting factor. As these three objectives may conflict, compromises are needed to arrive at an optimum solution.<br>The second reactive power dispatch approach unifies real and reactive power dispatch by minimizing both MW and MVAr generation costs while enforcing the MW and MVAr/voltage constraints simultaneously. This unified dispatch avoids a disadvantage of the two-step MVAr dispatch, that is, that the MW price signal determined in the energy market may be distorted by the subsequent MVAr dispatch in the ancillary services market.<br>Several numerical examples under different conditions are presented to examine and compare the effectiveness of these two methods.
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El-Damak, Dina Reda. "Power management circuits for ultra-low power systems." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/99821.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 137-145).<br>Power management circuits perform a wide range of vital tasks for electronic systems including DC-DC conversion, energy harvesting, battery charging and protection as well as dynamic voltage scaling. The impact of the efficiency of the power management circuits is highly profound for ultra-low power systems such as implantable, ingestible or wearable devices. Typically the size of the system for such applications does not allow the integration of a large energy storage device. Therefore, extreme energy efficiency of the power management circuits is critical for extended operation time. In addition, flexibility and small form factor are desirable to conform to the human body and reduce the system's over all size. Thus, this thesis presents highly efficient and miniature power converters for multiple applications using architecture and circuit level optimization as well as emerging technologies. The first part presents a power management IC (PMIC) featuring an integrated reconfigurable switched capacitor DC-DC converter using on-chip ferroelectric caps in 130 nm CMOS process. Digital pulse frequency modulation and gain selection circuits allow for efficient output voltage regulation. The converter utilizes four gain settings (1, 2/3, 1/2, 1/3) to support an output voltage of 0.4 V to 1.1 V from 1.5 V input while delivering load current of 20 [mu]A to 1 mA. The PMIC occupies 0.366 mm² and achieves a peak efficiency of 93% including the control circuit overhead at a load current of 500 [mu]A. The second part presents a solar energy harvesting system with 3.2 nW overall quiescent power. The chip integrates self-startup, battery management, supplies 1 V regulated rail with a single inductor and supports power range of 10 nW to 1 [mu]W. The control circuit is designed in an asynchronous fashion that scales the effective switching frequency of the converter with the level of the power transferred. The ontime of the converter switches adapts dynamically to the input and output voltages for peak-current control and zero-current switching. The system has been implemented in 180 nm CMOS process. For input power of 500 nW, the proposed system achieves an efficiency of 82%, including the control circuit overhead, while charging a battery at 3 V from 0.5 V input. The third part focuses on developing an energy harvesting system for an ingestible device using gastric acid. An integrated switched capacitor DC-DC converter is designed to efficiently power sensors and RF transmitter with a 2.5 V regulated voltage rail. A reconfigurable Dickson topology with four gain settings (3, 4, 6, 10) is used to support a wide input voltage range from 0.3 V to 1.1 V. The converter is designed in 65 nm CMOS process and achieves a peak efficiency of 80% in simulation for output power of 2 [mu]W. The last part focuses on flexible circuit design using Molybdenum Disulfide (MoS₂), one of the emerging 2D materials. A computer-aided design flow is developed for MoS₂-based circuits supporting device modeling, circuit simulation and parametric cell-based layout - which paves the road for the realization of large-scale flexible MoS₂ systems.<br>by Dina Reda El-Damak.<br>Ph. D.
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Solhall, Axel, and Edvin Guéry. "Coordination of Wind Power and Hydro Power." Thesis, KTH, Industriell ekologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-210740.
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The goal of this project was to calculate how much wind power could be balanced with hydro power in our designated area consisting of five hydro power stations, four villages which consume power, possible locations for wind power and one connection to the national grid. To achieve this a simulation model was constructed in the GAMS software with the goal of achieving the maximum profit from the hydro power plants by considering electricity prices, inflow of water, the physical construction of the power plants and the time of year. When this was achieved, restriction for the maximum transmission load on the power grid was added as well as local wind power production as to simulate the implementation of new power sources on an old system and power grid. This would result in a maximum income in SEK as well as the most wind power which could be maintained and balanced by the designated system. This project shows how to find the optimal way to use hydro power and wind power as well as how the integration between different sources of electricity production could work, which is vital for a future powered by renewable energy and will help towards lowering emissions.
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Chan, Lai Cheong. "Investigation on energy efficiency of electrical power system in Macau Coloane power plant." Thesis, University of Macau, 2012. http://umaclib3.umac.mo/record=b2586280.
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Burt, Robert. "Distributed Electrical Power System in Cubesat Applications." DigitalCommons@USU, 2011. https://digitalcommons.usu.edu/etd/1052.
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The single bus voltage distributed architecture is the mainstay architecture for small satellite spacecraft. Even large satellites follow this architecture. While they may have more than one voltage that is distributed, such as a high voltage bus and a low voltage bus, within a subsystem, there is usually one bus voltage. Each subsystem component is responsible for further regulation or point-of-load regulation. The Nano-satellite class, and more particularly the cubesat, have broken away from this norm and overwhelmingly implement a centralized architecture. With the advances of small, highly efficient monolithic dc-dc converters, this thesis researches the possibilities of implementing the distributed architecture at the cubesat scale. The Goal is to create a very efficient electrical power system design that has a high degree of utility, allowing it to be used for multiple missions, without having to redesign the system every time.
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Khanabadi, Ghehi Mojtaba. "Global Operation of Integrated Decentralized Power Systems." Thesis, Mississippi State University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10643425.
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<p> Nowadays, power systems are interconnected together to provide a reliable and secure source of energy to the consumers and operate at lower operating cost than if they being run separately. As the most important reason for interconnecting power systems is to improve the economic aspects in operation of the entire system, this interconnection between power systems would provide the following economic advantages: 1) lower overall congestion costs for consumers; 2) more consistent prices across the areas; and 3) lower operating cost due to presence of broader pool of mutual benefits shared between systems. In addition, in the event of an emergency in any individual system, such as a shortage of generation capacity and a network outage, an interconnected power system can utilize all available power generation resources and delivery facilities throughout the entire grid to adjust the transferring power among systems; thus, guaranteeing a continuous power supply to customers in their regions and achieving a high-level power system reliability. Also, in the event of transmission line congestion, the interconnected power systems can work closely together to remove the congestion from the entire power grid. </p><p> The main motivation of this dissertation is to provide methodologies which enable different regional/virtual system’s operators to efficiently schedule their regional generation resources and optimally coordinate their operations with other neighboring areas while respecting the information privacy between individual systems. Our proposed methodologies rely on decentralized solution philosophies. Using these methods, the original large-scale problems can be divided into several scalable and tractable subproblems, where their solution can be coordinated with each other to find the optimal operating point of the entire system using either sequential or parallel calculation. Furthermore, by providing the flexibility to define the border of the areas, the decentralized solution methodologies can be also utilized to accelerate the solution process of the decision-making process in a large-scale power system where an enormous number of variables should be accommodated into the problem formulation.</p><p>
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Jensen, Amanda C. "Power Divider Miniaturization with a Variable Load." Thesis, Marquette University, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=13815232.
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<p> A 3 Tesla (127.72 MHz) Magnetic Resonance system is able to scan with both the body coil and surface coil at the same time due to a technology called simultaneous acquisition, which uses a 4-port power divider, typically a quad hybrid. This functions at 127.72 MHz. The goal is to replicate this function at 1.5 Tesla field strength (63.86 MHz), but to do so would require the power divider to double in size. This space is not available, so methods of miniaturizing the design were investigated. It was found that slow wave structures cannot shrink the quadrature hybrid design enough to fit inside the desired area. Meandering the transmission lines of the hybrid shrinks the design, but is still too large for our application. The use of lumped elements successfully shrinks the design to fit within the desired space. </p><p> Both the meander line design and lumped element design were printed on RO4350, a Rogers printed circuit board material. The meander line design meets all of the critical performance requirements, while the lumped element design did not. </p><p> The design also had to withstand a variable load and coupling between the coils of the body coil. To test for this, the printed boards were attached to a body coil and a variable attenuator. The meander line design met all the performance requirements and had better performance than the lumped element design.</p><p>
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Biglarbegian, Mehrdad. "High Frequency GaN Power Converters Digital Twin." Thesis, The University of North Carolina at Charlotte, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10979304.
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<p> There is a need for a foundation of a research study aimed at investigations on near real-time reliability awareness of Gallium Nitride devices in high-frequency power converters for which we need advanced hardware and algorithms. This dissertation is moving beyond traditional reliability analysis and looking to more applicable and accurate analytical tools by introducing deep learning techniques and advanced sensing solutions. The computational structures will be applied at the edge of the power converter through online sensing and data processing units as well as on a remote server. They will provide an iterative ability to predict the time until the device may fail or reach a pre-defined degradation threshold. </p><p> With the availability of the most granular information deduced from advanced devices, a new data-driven scheme is proposed for system monitoring and possible lifetime extension Gallium Nitride power converters. The approach relies on the real-time on-resistance data extraction from the power converter, and calibration of an adaptive model using multi-physics co-simulations under power cycling. More specifically, the focus is on deploying machine learning algorithms to exploit for the parameter estimation in power electronics engineering reliability. The proposed techniques in this work are quite new and have not yet been developed and analyzed for high-frequency power converters specifically with Gallium Nitride power semiconductor devices.</p><p>
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Kulworawanichpong, Thanatchai. "Optimising AC electric railway power flows with power electronic control." Thesis, University of Birmingham, 2004. http://etheses.bham.ac.uk//id/eprint/4/.
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The latest generation of AC-fed traction drives, employing high-speed switching devices, is able to control the reactive power drawn from the overhead line by each equipment. If the conditions at each locomotive or train could be fed back to a central control point, it is possible for a centrally located controller to calculate optimal values for the reactive power in each drive and to send those commands back to the individual equipment. In this thesis, AC railway power flows are optimised in real time and the results are used to achieve some particular system objective via control of the PWM equipment as mobile reactive power compensators. The system voltage profile and the total power losses can be improved while the overall power factor at the feeder substation is also made nearer to unity. For off-line simulation purposes, high execution speeds and low storage requirements are not generally significant with the latest computer hardware. However, this real-time control employs on-line optimising controllers, which need embedded power solvers running many times faster than real time. Thus, a fast and efficient algorithm for AC railway power flow calculation was developed. The proposed scheme is compared to a conventional reactive power compensation, e.g. SVC, and found to be less expensive to implement. Several test cases for AC electric railway systems are examined. The centralised area control system leads to the best improvement where an existing fleet of diode or thyristor phase-angle controlled locomotives is partially replaced with PWM ones, compared to that obtained without compensation or to classical track-side Var compensation methods. From these results, the potential for PWM locomotives to improve overall system performance is confirmed.
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Das, Sauparna 1979. "Magnetic machines and power electronics for power MEMS applications." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/34465.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.<br>Includes bibliographical references (p. 321-323).<br>This thesis presents the modeling, design, and characterization of microfabricated, surface-wound, permanent-magnet (PM) generators, and their power electronics, for use in Watt-level Power MEMS applications such as a microscale gas turbine engine. The generators are three-phase, axial-flux, synchronous machines, comprising a rotor with an annular PM and ferromagnetic core, and a stator with multi-turn surface windings on a soft magnetic substrate. The fabrication of the PM generators, as well as the development of their high-speed spinning rotor test stand, was carried out by collaborators at the Georgia Institute of Technology. The machines are modeled by analytically solving 2D magneto-quasistatic Maxwell's Equations as a function of radius and then integrating the field solutions over the radial span of the machine to determine the open-circuit voltage, torque and losses in the stator core. The model provides a computationally fast method to determine power and efficiency of an axial-air-gap PM machine as a function of geometry, speed and material properties. Both passive and active power electronics have been built and tested. The passive power electronics consist of a three-phase transformer and diode bridge rectifier.<br>(cont.) The active power electronics consist of a switch-mode rectifier based on the boost semi-bridge topology which is used to convert the unregulated AC generator voltages to a regulated 12 V DC without the need for rotor position/speed or stator terminal current/voltage sensing. At the rotational speed of 300,000 rpm, one generator converts 16.2 W of mechanical power to electrical power. Coupled to the transformer and diode bridge rectifier, it delivers 8 W DC to a resistive load. This is the highest output power ever delivered by a microscale electric generator to date. The corresponding power and current densities of 57.8 MW/m3 and 6x 108 A/m2, respectively, are much higher than those of a macroscale electric generator. At the rotational speed of 300,000 rpm, the generator and switch-mode rectifier delivered 5.5 W DC to a resistive load at a power density three times that of the passive electronics. This Watt-scale electrical power generation demonstrates the viability of scaled PM machines and power electronics for practical Power MEMS applications.<br>by Sauparna Das.<br>Ph.D.
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Lund, Richard. "Multilevel Power Electronic Converters for Electrical motor Drives." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Information Technology, Mathematics and Electrical Engineering, 2005. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-687.
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<p>Power electronic converters are widely used in industrial power conversion systems both for utility and drives applications. As the power level increases, the voltage level is increased accordingly to obtain satisfactory efficiency. During the last years, the voltage rating of fast switching high voltage semiconductors such as the Insulated Gate Bipolar Transistor (IGBT) has increased. Still, there is a need for series connection of switching devices. In this area of applications, the Multilevel Converter has shown growing popularity.</p><p>The fundamental advantages of the Multilevel Converter topologies are low distorted output waveforms and limited voltage stress on the switching devices. The main disadvantages are higher complexity and more difficult control. </p><p>In this thesis, Multilevel Converters are analysed for large motor drive applications. The main focus has been on converter losses, output waveform quality and control.</p><p>Analytical expressions for both switching and conduction losses for 4- and 5-level Diode Clamped Converters have been developed. The investigation shows that the losses can be reduced by utilizing a multilevel topology for a 1 MW drive. This work is presented in [46]. The same reduction in losses is proven for a 2300V/ 3 MW drive.</p><p>Analytical expressions for the harmonic losses in 3-level converters have been developed for 2 different Carrier Based PWM schemes, presented in [56], [57] and [58]. Also Space Vector PWM are investigated and compared by simulations, in addition to 4- and 5-level Carrier Based PWM.</p><p>DC-bus balancing in both 3- and 5-level converters is discussed. Balancing in 3- level converters can be achieved by proper control. Balancing in 5-level converters can be achieved by proper arrangement of isolated DC-supplies.</p><p>One 40kW 3-level converter and one 5kW 5-level converter has been designed and built. Experimental verification of the analytical and simulated results is shown.</p>
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Whitcomb, Clifford Alan. "Composite system analysis of advanced shipboard electrical power distribution systems." Thesis, Cambridge, Massachusetts : Massachusetts Institute of Technology, 1992. http://handle.dtic.mil/100.2/ADA254851.
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Thesis (Nav. E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1992 and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1992.<br>Thesis Advisor: Kirtley, James L., Jr. "May 1992." Description based on title screen as viewed on March 30, 2009. Includes bibliographical references (p. 73-74). Also available in print.
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Wang, Miao. "Design of A Double-End Sourced Multi-Chip Power Module and A High Power-Density Three-Phase Inverter." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1479744941973868.
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Martinez, Manuel Madrigal. "Modelling of power electronics controllers for harmonic analysis in power systems." Thesis, University of Glasgow, 2001. http://theses.gla.ac.uk/2836/.
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The research work presented in this thesis is concerned with the modelling of this new generation of power electronics controllers with a view to conduct comprehensive power systems harmonic analyses. An issue of paramount importance in this research is the representation of the self-commutated valves used by the controllers addressed in this work. Such a representation is based on switching functions that enable the realization of flexible and comprehensive harmonic models. Modularity is another key issue of great importance in this research, and the model of the voltage source converter is used as the basic building block with which to assemble harmonic models of actual power systems controllers. In this research the complex Fourier series in the form of operational matrices was used to derive the harmonic models. Also, a novel methodology is presented in this thesis for conducting transient analysis of electric networks containing non-linearities and power electronic components. The methodology is termed the extended harmonic domain. This method is based on the use of time-dependent Fourier series, operational matrices, state-space representation and averaging methods. With this method, state-space equations for linear circuit, non-linear circuits, and power electronics controllers models are obtained. The state variables are the harmonic coefficients of x(t) instead of x(t) itself. The solution of the state-space equations gives the dynamic response of the harmonic coefficients of x(t). Moreover, a new harmonic power flow methodology, based on the instantaneous power flow balance concept, the harmonic domain, and Newton-Raphson method, is developed and explained in the thesis. This method is based on the instantaneous power balance as opposed to the active and reactive power balance, followed by traditional harmonic power flow methods. The power system and the power electronics controllers are modelled entirely in the harmonic domain.
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Stander, Tinus. "High-power broadband absorptive waveguide filters." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1157.
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Thesis (PhD (Electrical and Electronic Engineering))--University of Stellenbosch.<br>ENGLISH ABSTRACT: This dissertation presents a synthesis method for broadband high-power absorptive microwave
lters by cascading a wide stop-band wa e-iron lter with an absorptive harmonic
pad.
The classical image impedance synthesis methods for wa e-iron lters are updated to
allow for non-uniform boss patterns, which enable control over both the stop-band attenuation
and pass-band re
ection of the lter. By optimising an accurate circuit model
equivalent, computationally intensive numerical EM optimisation are avoided. The nonuniform
wa e-iron lter achieves the same electrical speci cation as similar lters in
literature, but in a smaller form factor. The prototype presented displays less than -21
dB in-band re
ection over 8.5 - 10.5 GHz, with stop-band attenuation in excess of 50 dB
over the harmonic bands 17 - 31.5 GHz and 30 dB over the 34 - 42 GHz. The prototype is
designed to handling 4 kW peak power incident in the transmitted band, and is 130 mm in
length. Minimal full-wave tuning is required post-synthesis, and good agreement is found
between synthesised and measured responses. Additionally, a completely novel oblique
wa e-iron boss pattern is proposed.
For the absorptive harmonic pad, transversal broadwall slots in rectangular waveguide,
coupling to an absorptive auxiliary guide, are investigated in the presence of standing
wave surface current distributions. An accurate circuit model description of the cascaded
structure is developed, and optimised to provide a required level of input match in the
presence of an arbitrary re
ective lter. Using numerical port parameter data of the wa eiron
lter, a harmonic pad is developed that provides -12.5 dB input re
ection match
across the band 17 - 21 GHz with up to 1 kW peak incident power handling capability,
yet is only 33 mm in length. Again, good agreement is found between synthesised and
measured responses of the cascaded structure.<br>AFRIKAANSE OPSOMMING: Hierdie proefskrif stel 'n sintesetegniek voor vir wyeband, ho edrywing absorberende mikrogol
lters deur 'n kaskade kombinasie van 'n verlieslose wafelyster lter met 'n wye stopband,
en 'n absorberende harmoniekdemper.
Die klassieke sintesemetodes vir wafelyster lters word aangepas om nie-uniforme tandpatrone
toe te laat, wat beheer oor beide die lter se stopband attenuasie en deurlaatband
weerkaatsing moontlik maak. Deur die optimering van 'n akkurate stroombaanmodel
van die lter kan berekeningsintensiewe numeriese EM optimering vermy word. Die nieuniforme
wafelyster lter behaal dieselfde spesi kasies as soortgelyke gepubliseerde lters,
maar is meer kompak. Die vervaardigingsprototipe handhaaf minder as -21 dB intreeweerkaatsing
oor die deurlaatband van 8.5 - 10.5 GHz, asook attenuasie van meer as 50
dB oor die stopband 17 - 31.5 GHz en 30 dB oor 34 - 42 GHz. Die prototipe is ontwerp
om 4 kW intree kruindrywing te hanteer in die deurlaatband, en is 130 mm lank.
Die metode vereis minimale verstellings tydens volgolf simulasie, en die meetresultate
stem goed ooreen met die gesintetiseerde gedrag. 'n Nuwe skuinstandpatroon word ook
voorgestel vir wafelyster lters.
Vir die harmoniekdemper word transversale bre ewandgleuwe in reghoekige gol
eier wat
koppel na 'n absorberende newegol
eier ondersoek in die teenwoordigheid van staandegolfpatrone
in oppervlakstroom. 'n Akkurate stroombaanmodel van 'n gleufkaskade word
ontwikkel, en geoptimeer om 'n vereiste intreeweerkaatsing te bewerkstellig in samewerking
met 'n arbitr^ere weerkaatsende lter. Deur gebruik te maak van poortparameterdata
van die wafelyster lter word 'n 33 mm lange hamoniekdemper ontwikkel wat 'n maksimum
intreeweerkaatsing van -12.5 dB oor die band 17 - 21 GHz handhaaf vir kruindrywingsvlakke
van tot 1 kW. Goeie ooreenstemming tussen gesintetiseerde en gemete resultate
word weereens waargeneem vir die volledige saamgestelde struktuur.
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Victor, Alan M. "Microwave Power Oscillator utilizing Thin-Film Varactor." NCSU, 2010. http://www.lib.ncsu.edu/theses/available/etd-03232010-100654/.
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Synthesis of Microwave Power Oscillators utilizing Thin-film Varactors. The application of the power oscillator is in high efficiency microwave sources for the direct carrier launch of microwave signals. The resulting work directing towards the efficient implementation for microwave transmitters.
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Rahkola, A. (Antti). "RF Pre-power Amplifier for LTE SoC." Master's thesis, University of Oulu, 2018. http://urn.fi/URN:NBN:fi:oulu-201806052447.
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This work focused on evaluating a single-ended complementary push-pull topology for LTE system-on-chip RF pre-power amplifier, to increase power efficiency compared to an existing class-A amplifier. Suitability of the push-pull topology was studied against strict linearity specification. Frequency range in this study was 1710–2020 MHz, and 10 dBm sine wave output power was targeted. Common source and source follower amplifier variants were designed and simulated in a schematic level. Gain control functionality was implemented by dividing the amplifier into controllable partitions. Output DC-voltage was set using a common mode feedback. Source follower topology performance was severely affected by impedance gyration, which was compensated by lowering the amplifiers’ input impedance. This however dropped performance significantly, and therefore common source topology was stated to be a better choice for the pre-power amplifier. Linearity was adequate in both topologies. Schematic level common source variant simulations showed good typical performance for LTE bands 2 and 23, although design improvements were also identified. PAE over 40 % for 10 dBm sine wave was simulated, while S22 was better than -10 dB. Harmonic frequency levels were low, and OIP3 of 23 dBm was achieved. According to schematic simulations, class-A 1.8 GHz pre-power amplifier can be replaced with a complementary common source push-pull amplifier, to achieve better power efficiency<br>Tässä työssä tutkittiin yksipäisen komplementaarisen push-pull topologian soveltuvuutta LTE-järjestelmäpiirin RF-esitehovahvistimeksi, parantamaan tehohyötysuhdetta verrattuna nykyiseen A-luokan vahvistimeen. Push-pull -topologian soveltuvuutta tutkittiin tiukkaa lineaarisuusvaatimusta vasten. Tutkimuksen taajuusalue oli 1710–2020 MHz, ja 10 dBm siniaaltoulostuloteho oli tavoitteena. Työssä suunniteltiin ja simuloitiin yhteislähde- ja lähdeseuraaja-vahvistinversiot piirikaaviotasolla. Vahvistimet hajautettiin aktivoitaviin osioihin vahvistuksensäätöä varten ja lähdön DC-jännite asetettiin käyttäen yhteismuotoista takaisinkytkentää. Lähdeseuraaja-topologian suorituskykyyn vaikutti haitallisesti impedanssigyraatio, jota kompensoitiin laskemalla vahvistimen tuloimpedanssia. Tämä kuitenkin laski suorituskykyä merkittävästi, ja tästä syystä yhteislähde-topologian todettiin olevan parempi vaihtoehto esitehovahvistimelle. Molemmat topologiat olivat riittävän lineaarisia. Piirikaaviotason yhteislähde-version simulaatiot osoittivat hyvää tyypillistä suorituskykyä LTE-kanavilla 2 ja 23, vaikka version kehityskohteitakin tunnistettiin. Yli 40 % PAE simuloitiin 10 dBm siniaallolla, S22 ollessa parempi kuin -10 dB. Harmonisten taajuuksien tasot olivat matalat, ja 23 dBm OIP3 saavutettiin. Piirikaaviosimulaatioiden mukaan A-luokan 1.8 GHz esitehovahvistin voidaan korvata komplementaarisella yhteislähde push-pull -vahvistimella, jotta parempi tehohyötysuhde saavutettaisiin
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Xiangxiang, Fang. "Characterization and Modeling of SiC Power MOSFETs." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354687371.
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Zhang, Xuan. "Switched Capacitor Circuit Based Isolated Power Converters." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461327493.
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Ma, Zhuxuan. "Voltage Balance for Super-Cascode Power Modules." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555055905885979.
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Stephen, Robert G. "Objective determination of optimal power line designs." Doctoral thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/11231.
Full textAbstract:
Includes bibliographical references (leaves 139-143).<br>The thesis investigated the possibility of overhead power line designs being decided by using an objective rather than a subjective method. Power lines are required to meet criteria for load and transfer capability as specified by system planners which results in many different line design solutions. The decision as to which solution to adopt and construct is difficult if a subjective method is used. The hypothesis proposed is thus as follows: It appears that one or a small set of appropriate technology indicators can be used by network planners and designers to identify the best group of overhead lines to meet specified objectives. These indicators can be used for a wide range of applications for AC and DC lines.
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Parry, Richard A. J. "Remote control and monitoring of power systems." Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/5128.
Full textAbstract:
Includes synopsis.<br>Includes bibliographical references (leaves 87-93).<br>Power systems are typically complex and can be affected by their environment in ways that cannot be completely predicted by their designers. It is thus imperative that monitoring is considered as part of the design of new power systems. Due to the associated costs of maintenance, repair, and downtime, monitoring these systems is particularly important when the installations are remote. Remote locations benefit greatly from renewable energy sources. As a result, this work focuses on a novel Hybrid Inverter system developed by Optimal Power Solutions Pty. Ltd. (OPS). This system uses renewable energy sources, grid power, and diesel generators together with a bi-directional inverter to supply a remote location with grid-quality power.
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Green, A. G. "The design of high power ultrasonic transducers." Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/5211.
Full textAbstract:
Includes bibliographical references.<br>The purpose of this thesis is to investigate the design and construction of high power ultrasound transducers as well as some of the effects of high power ultrasound. The two design approaches that are researched and applied are the equivalent circuit method and Finite Element Method (FEM). These methods are used in conjunction with each other to design three different transducers, which are then built and tested at low and high powers.
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Gao, Fei. "Decentralised control and stability analysis of a multi-generator based electrical power system for more electric aircraft." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/37955/.
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The more electric aircraft initative results in significant challenges in the design of aircraft electrical power systems. Different power system architectures are currently being studied by the engineering community. In this thesis, a promising single DC bus-based, multiple-source multiple-load power system is investigated in terms of power management and stability. Due to its inherent modularity and ease of implementation, droop control, as a decentralised control method, has been widely used to cope with power sharing among parallel sources in the studied architecture. The thesis proposes a comparative study of different droop control approaches by focusing on steady-state power sharing performance and stability. • Different droop control methods may lead to different stability margins. Until now, the effect of different droop control schemes on system stability has not been fully investigated. The thesis presents the control scheme for current-mode and voltage-mode systems, derives the corresponding output impedance of the source subsystem and analyses the stability of the power system. Based on the developed mathematical model, comprehensive modal analysis of the power system is performed. • A generalised analytical impedance analysis is extended to a multi-source multi-load power system. To facilitate the analysis, the thesis proposes the concept of “global droop gain” as an important factor to determine the V-I bus characteristic and the stability behaviour of a parallel sources based DC system. • Considering the tradeoff between voltage regulation and power sharing accuracy in droop control, this thesis proposes an improved voltage regulation method in multi-source based DC electrical power system. Due to the absence of additional controllers or communication lines, the proposed approach can be relatively easily implemented in a small scale DC electrical power system. The proposed approach effectively improves the load sharing accuracy under high droop gain circumstances with consideration of cable impedance. Optimal droop gain settings are investigated and the selection of individual droop gains has been described in order to reduce the distribution losses. Finally, the above-mentioned analytical results are confirmed by time-domain simulations and experimental results.
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Thapliya, Bikash. "Power utility restructuring and power-sector financing in developing countries." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/42670.
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