Dissertations / Theses on the topic 'Electrical Engineering: Power Electronics'
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1
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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Das, Debosmita. "Advanced power electronics for hybrid energy systems." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1412940298.
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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.Includes bibliographical references (p. 321-323).
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.
(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.
by Sauparna Das.
Ph.D.
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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.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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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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McNeill, John Neville. "Current transformer circuits for power electronics applications." Thesis, Edinburgh Napier University, 2008. http://researchrepository.napier.ac.uk/Output/6196.
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This thesis investigates the operation of the current transfonner (CT) when sensing retum-to-zero current pulses in power electronic circuitry. The CT's output signal is nonnally rectified when sensing current pulses and the effects of the different rectification techniques on peak current and average current droop are evaluated. Initially, the various current sensing techniques and their application in power electronics circuits are reviewed. The CT and both diode and synchronous rectification are then reviewed in more detail. Operation of the CT with diode rectification (DR) and natural resetting is investigated. Three operating modes are identified. These are the discontinuous magnetizing current, continuous magnetizing current and discontinuous secondary current modes. The error (droop) in the average output signal obtained is found to be predominantly defined by CT core losses. Coefficients are given for correcting the error due to droop, provided that the discontinuous secondary current mode is avoided. Diode rectification with the dual CT arrangement is also investigated. Operation of the CT with synchronous rectification (SR) and natural resetting is then investigated. The SR topologies possible using a discrete MOSFET are categorized. During experimentation the arrangement used to drive the MOSFET's gate is found to be important if distortion is to be minimized. It also is found that the average current droop is dependent on the oscillatory behaviour of the resetting circuit and has an effectively random component. The magnitude of this component is defined by the voltage drop exhibited by the SR MOSFET's intrinsic anti-parallel diode. SR is then implemented using a commercially available analogue switch. The problems detailed with the use of a discrete MOSFET are largely alleviated. Another benefit is that the increased restriction on maximum duty factor imposed by introducing a discrete MOSFET is also eased. However, whichever SR technique is implemented, an operational amplifier is used and the transient response of this circuit element is important. A method of minimizing droop by indirect sensing of the CT's peak core flux excursion is then presented. A corresponding correcting voltage is applied in series with the CT's output terminals during a current pulse. The magnitude of this voltage is based on the magnitude of the resetting voltage sensed during previous switching cycles. A circuit is implemented and simulated. Experimental results are presented. A switched-mode circuit operating at a frequency higher than that of the main power circuit is then used to apply the correcting voltage with the objective of reducing the power drawn. Again, the circuit is implemented and simulated and experimental results are presented.
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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.
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This thesis analyzes generator reactive power dispatch under restructured power systems from two different perspectives.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.
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.
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.
Several numerical examples under different conditions are presented to examine and compare the effectiveness of these two methods.
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Araghchini, Mohammad. "(MEMS) toroidal magnetics for integrated power electronics." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/84882.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 237-241).
Power electronics represent a key technology for improving the functionality and performance, and reducing the energy consumption of many systems. However, the size, cost, and performance constraints of conventional power electronics currently limit their use. This is especially true in relatively high-voltage, low-power applications such as off-line power supplies, light-emitting diode (LED) drivers, converters and inverters for photovoltaic panels, and battery interface converters; a LED driver application serves as a motivation example throughout the thesis. Advances in the miniaturization and integration of energy-conversion circuitry in this voltage and power range would have a tremendous impact on many such applications. Magnetic components are often the largest and most expensive components in power electronic circuits and are responsible for a large portion of the power loss. As operating frequencies are increased, the physical size of the passives can, in theory, be reduced while maintaining or improving efficiency. Realizing this reduction in size and the simultaneous improvement in efficiency and power density of power electronic circuits requires improvements in magnetics technology. This thesis focuses on the challenge of improving magnetics through the analysis, optimization, and design of air-core toroidal inductors for integration into high-efficiency, high-frequency power electronic circuits. The first part of the thesis presents the derivation of models for stored energy, resistance and parasitic capacitance of microfabricated toroidal inductors developed for use in integrated power electronics. The models are then reduced to a sinusoidal-steady-state equivalent-circuit model. Two types of toroidal MEMS inductors are considered: in-silicon inductors (with or without silicon core) and in-insulator inductors. These inductors have low profiles and a single-layer winding fabricated via high-aspect-ratio molding and electroplating. Such inductors inevitably have a significant gap between winding turns. This makes the equivalent resistance more difficult to model. The low profile increases the significance of energy stored in the winding which, together with the winding gap, makes the equivalent inductance more difficult to model as well. The models presented in this thesis account for these effects. In the case of in-silicon inductors, magnetically and electrically driven losses in different regions of silicon are modeled analytically as well. The second part of the thesis focuses on the optimized design of microfabricated toroidal inductors for a LED driver. The models developed in the first part of the thesis allow optimization of inductor designs based on objectives such as minimizing substrate area, maximizing efficiency, and simplifying the fabrication process by maximizing minimum feature size. Because the magnetics size and loss depend strongly on the driver design parameters, and the driver performance depends strongly on the inductance value and loss, the simultaneous optimization of driver components and magnetics parameters is used in the design process. The use of computationally efficient models for both magnetics and other circuit components permits numerical optimization using the general co-optimization approach. Finally, a multi-dimensional Pareto-optimal filtering is applied to reduce the feasible design set to those on the multi-objective optimality frontier. For the case of LED drivers, the current state of the art efficiencies range from 65% to 90%. The co-optimization process results in efficiencies greater than 90% while reducing the size of the LED driver by 10 to 100 times compared to the commercially available LED drivers. This is a significant improvement in both the efficiency and the size of the LED drivers. In the resulting designs, the magnetics are no longer the largest part of the circuit. In the third part of the thesis several numerical and experimental tests are presented. The models developed in this thesis, are verified against results from 2D FEA, 3D FEA, direct measurement of MEMS fabricated devices (for both in-insulator devices for flip-chip bonding and in-silicon devices for direct integration), and in-circuit experimentation of the fabricated devices. These tests show that the equivalent-circuit models presented in this thesis have greater accuracy than existing models. The results also show that these models are good enough to support the LED driver optimization.
by Mohammad Araghchini.
Ph.D.
9
Sun, Bo. "A FPGA-based power electronics controller for three-phase four-wire hybrid active power filters." Thesis, University of Macau, 2011. http://umaclib3.umac.mo/record=b2547180.
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Al, Johani Ebrahim Dakhil. "Surface transfer doping of diamond for power electronics." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/129079.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, September, 2020Cataloged from student-submitted PDF of thesis.
Includes bibliographical references (pages 77-80).
The quest for a suitable wide-bandgap semiconductor for high-power and high-frequency applications is well motivated; wide-bandgap semiconductors generally exhibit a high breakdown field and can therefore support a high voltage over short distances. Diamond (Bandgap of 5.5 eV) in particular is an attractive prospect since its thermal conductivity and radiation hardness well surpass other wide-bandgap semiconductors. However, practical transistors require the ability to engineer the charge density through substitutional doping which has proven to be difficult considering the strong covalent bonds that make up bulk diamond. In this work, we utilize hydrogen-passivated diamond surface along with surface acceptors to generate a highly conductive 2D hole sheet at the surface with carrier densities going up to 10¹⁴ cm⁻². Surface transfer doping using stable high electron affinity transition-metal oxides (TMO) such as WO₃ in conjunction with the novel contact-first process explored in this work shows great promise on advancing process stability while attaining the high current densities desired in the future of power diamond transistors. We closely examine the H-terminated diamond/TMO interface using a numerical approach based on a Schrödinger-Poisson solver package. We identify key inconsistencies in the generic valence-to-conduction transfer model for both shallow and deep TMO electron affinity regimes. We report that introducing deep level impurities in the TMO have shown improvements to the effect of bias modulation and agreement with experiments for low TMO affinities. A solution for engineering a preexisting TMO with fixed affinity and trap level is presented through TMO thickness engineering. The methods explored in this work show promise towards the enhancement of diamond conductivity and reproducibility.
by Ebrahim D. Aljohani.
M. Eng.
M.Eng. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
11
Wang, Qi. "Logic synthesis for low power." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/288924.
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The dissertation addresses several problems in the power optimization and power-delay tradeoffs in digital CMOS circuits. The work is organized according to the three main sources of power dissipation: Power dissipation due to switching (P(sc)), standby or leakage power (P(leak)) and short circuit power (P(sc)). First we present new, efficient and provably correct algorithms for minimizing the switching power in combinational and sequential CMOS logic circuits. The techniques are based on the addition and removal of redundancies at the logic level. The basic technique developed for combinational circuits is extended to sequential circuits. Results of experiments carried on large (thousands of logic gates) commerical circuits (of the PowerPC chip) will be presented. Power dissipation due to the short circuit current has received much less attention. For submicron MOSFETs, this can be comparable to the switching power. A new, and computationally tractable model for the short circuit current in CMOS inverters and more complex CMOS gates was developed. This model was verified using a commerical 0.25 μm CMOS library and device models. The problem of minimizing the standby power for deep submicron technology is also addressed. The standby power dissipation has often been ignored in the design of CMOS circuits since its contribution to the total power dissipation has been negligable. However as device dimensions and voltages are scaled down, the standby power can be of the same order of magnitude as the switching power. This is a serious problem of many portable devices as they are in standby mode for considerable periods of time. One approach to alleviate this problem is the use of dual threshold voltages. We developed several new algorithms that optimally assign one of two threshold voltages to CMOS gates so as to minimize the standby power without sacrificing performance. The new algorithms handle circuits of thousands of gates and it is shown that the standby power can be reduced by as much as an order of magnitude without any loss of performance.
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Lok, Io Keong. "Study of soft-switching techniques on three-level three-phase four-wire active power filters." Thesis, University of Macau, 2010. http://umaclib3.umac.mo/record=b2493512.
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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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Du, Toit J. A. (Jacques Andre). "Development and analysis of a distributed control strategy for power electronic converters." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52761.
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Thesis (PhD)--University of Stellenbosch, 2002.ENGLISH ABSTRACT: The dissertation presents an alternative approach to the control of power electronic converters. The conventional approach is to use a centralized controller with one or more measurement systems providing feedback. As converters become larger, in both power rating and complexity, a number of drawbacks to this approach emerge. The number of physical data paths increases and voltage isolation becomes a problem. This has an adverse effect on the manufacturability as well as the reliable operation of the system as a whole. An alternative is to use a distributed control approach, where a number of smaller integrated control and measurement units are used. These units communicate with the central controller via a serial daisy-chain communications link. The dissertation investigates the design of such a controller as well as the application of distributed control in a number of emerging converter topologies. It was shown that centralized control has its limitations in modem power electronics in terms of reliability, maintainability and manufacturability. A feasible distributed control strategy was proposed and implemented and the operation was verified in an experimental converter system.
AFRIKAANSE OPSOMMING: Die proefskrif ondersoek 'n alternatiewe manier om drywings omsetters te beheer. Huidiglik word die meerderheid van omsetters beheer vanaf 'n sentrale beheereenheid, wat dan stelsel data versamel vanaf een of meer meetstelsels. Soos die drywingsvermoë van die omsetters toeneem, raak spannings isolasie en die aantal beheerseine 'n probleem, wat nadelig is vir die betroubaarheid en vervaardigbaarheid van die stelsel. As 'n alternatief, kan 'n aantal kleiner beheereenhede en meetstelsels gebruik word. Die beheerders kommunikeer met mekaar, sowel as die hoof stelselbeheerder deur middel van 'n optiese vesel netwerk, verbind in 'n ring struktuur. Die proefskrif ondersoek die ontwerp van die beheerder en die toepassing van gedesentraliseerde beheer in 'n aantal nuwe omsetter topologië. Die studie toon dat sentrale beheer problematies kan raak soos die omsetters meer kompleks raak. Die studie bewys dat 'n stelsel suksesvol bedryf kan word deur gebruik te maak van gedesentraliseerde beheer deur dit in 'n praktiese opstelling toe te pas.
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Seo, Jongsoo. "Power-efficient multi-ary QAM systems." Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/5153.
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Arpin, Frederic N. "Multi-feed spatial power combining reflectarrays." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26566.
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In order to have increased bandwidth, future wireless communications systems will use millimeter-wave frequencies. Such systems will require antennas with relatively high gain and sources with sufficient power. Spatial power combining provides an attractive alternative to these issues. This thesis develops a means of combining the antenna and spatial power-combining functions in a single device. We formulate a design procedure that allows multiple feeds to illuminate a reflectarray that will give a single-beam. The reflectarray acts both as a spatial-power combiner and as the antenna. Unlike previous work that has been done on spatial power-combining reflectarrays, the proposed design does not involve the integration of any active devices. The new design procedure for a multi-feed spatial power-combining reflectarray was first applied to a two-feed reflectarray which was fabricated and tested as a proof of concept. (Abstract shortened by UMI.)
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Saadallah, Nisrine. "High-speed low-power asynchronous circuits." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80140.
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This thesis presents several design experiments for high-performance power-efficient asynchronous circuits.In Chapter two we present a new asynchronous pipeline logic family with improved latency and throughput compared to several other asynchronous pipeline circuits. The channels between pipeline stages use data encoding and a small set of minimum-delay timing constraints that permit modular design with few dependencies on technology and layout. We develop circuit blocks that implement linear pipelines as well as forking, joining and data-dependent decisions. An implementation in 0.18mum CMOS exhibits a latency of 56ps per pipeline stage and throughput of 4.8-giga data item per second (GDI/s) in Hspice simulation.
We also present the design of a low-control-overhead asynchronous microprocessor integrated with a high-speed sampling FIFO. This is an experiment in exploring the benefits of asynchronous design in high-speed embedded DSP applications. It reports on the design approach, implementation and performance, including a comparison with the synchronous version of the microprocessor.
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Cheng, Wing Mao John 1960. "Random bilateral trading in power systems." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36798.
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The power industry is undergoing a revolutionary change due to deregulation and associated restructuring. Deregulation is the legislation that governs open access to the transmission grid by competing producing and consuming entities. In this newly-created market structure, bilateral power transactions are emerging as a major trading mechanism. As such, bilateral contracts have become important decision variables in all aspects of power system operation and planning. Consequently, a critical question is how to evaluate the success of any given transaction, especially in the presence of other random simultaneous trades. A successful transaction is understood to be one under which a power system is secure and the proposed trade will be approved as is. This is a necessary condition for the transaction to be economically viable.The originality of this thesis lies in the integration of random bilateral trading with the physical transmission network. A methodology is developed to estimate the probability of success of any given transaction in the presence of simultaneous random trades with the security requirements of the power system as a given. This measure of success is termed POST (Probability of Secure Transaction). Different forms of POST are defined from the perspectives of the system, the trading partners, or the partners and amount transacted. These and other similar measures form a group of transaction-based security indices.
A Monte Carlo simulation approach is developed as a practical means to estimate the transaction-based security indices. Extensive testing and simulations show that this methodology is effective in transaction risk management, and in network adequacy assessment in the context of random trading. Furthermore, the methodology is used to determine the viability of proposed system reinforcements, especially major power system interconnections involving substantial investments in equipment and resources.
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Chen, Ruiming. "Analysis of modern power distribution networks." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66944.
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Analysis and proper design of power distribution networks (PDNs) are critical steps in developing modern electronic systems. Parallel-plate structures with vias are the core components of PDN configuration at any scale of system implementation from chip to package and printed circuit board. Voltage fluctuations induced by vias with carrying time-varying currents are interpreted as power/ground noise. In this thesis, this type of noise is quantified by two fast prediction methods, i.e. using radial transmission line theory and resonant cavity analysis. A number PDN structures containing single or multiple parallel-plates and vias are simulated using the developed analytical models. These models are portable to the commercial circuit simulators, provide a fast means of PDN analysis and enable global system simulations. Suppression of power/ground noise by using discrete decoupling capacitors and differential signalling is investigated using the developed models. The validity of the models is tested against full-wave simulations and prototype measurements. Improvement of power integrity is also studied by using a uniplanar EBG structure in a parallel-plate stack-up. The main challenge in employing EBG structures in compact low frequency designs is the relatively large footprint of the EBG unit cell. This thesis reviews two techniques for miniaturization of a uniplanar EBG and demonstrates their efficacy through full-wave simulations.L'analyse et la conception appropriée du réseau de distribution d'énergie (RDE) sont des étapes critiques lors du développement de systèmes électoniques modernes. La composante principale d'un RDE est une structure de plaques parallèles avec vias, et ce à toutes les étapes de l'implémentation, du désign circuit à la carte imprimée. Les fluctuations du voltage induites par le courant variable qui transite par les vias sont typiquement interprétées comme du bruit sur la source de tension ou la mise à la terre. Dans la présente thèse, ce type de bruit est quantifié à l'aide de deux méthodes rapides de prédiction. Celles-ci sont la théorie radiale des lignes de transmissions ainsi que l'analyse des cavités résonnantes. Plusieurs structures RDE contenant une ou plusieurs plaques parallèles combinées à des vias sont simulées à l'aide des modèles analytiques présentés. Ces modèles sont facilement transférables vers des simulateurs de circuits commerciaux, ce qui fournit un moyen rapide d'effectuer l'analyse du RDE dans une simulation globale. Nous analysons également la suppression de bruit de source/mise à la terre effectuée à l'aide de condensateurs discrets de découplage ou à l'aide de signalement différentiel. Les modèles sont validés par comparaison avec des simulations à onde complète et des mesures sur prototype. Nous étudions les améliorations à l'intégrité de la source de puissance à l'aide de structure EBG dans un empilage de plaques parallèles. Le défi principal relié à l'emploi de structures EBG dans un désign compact et basse fréquence est dû à la grande taille des unités EBG. Nous passons en revue deux techniques pour miniaturiser un EBG uniplanaire et démontrons leur efficacité à l'aide de simulation à onde complète.
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Dinh, Duc Dang. "Millimetre-wave power sensor design." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7851/.
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This study is to maintain and extend the power standards at National Physical Laboratory (NPL) in the United Kingdom. The calibration service of microwave power sensors at high frequencies is endangered because a limited number of traceable waveguide power sensors is available at 50 GHz and above. In this thesis, the technologies of sensing microwave power in waveguides are reviewed, and the bolometric power sensor is investigated further, as its principle is suitable for the traceability requirement at NPL. The conventional design technique of bolometric sensor based on transmission line theory is generalised and two power sensor designs are introduced. The X-band sensor was fabricated, measured at the University of Birmingham and calibrated at NPL. Excellent linearity and high effective efficiency of the design was obtained. The high frequency power sensor designs based on the proposed technique can be scalable to 300 GHz and above, and a W-band sensor is introduced as an example. In order to add more flexibility in selecting frequency and bandwidth, a novel design of microwave power sensor with integrated filter function is described. An analytical power sensor synthesis technique using coupling matrix is presented for the first time. An X-band power sensor with integrated third order Chebyshev filter function was designed and manufactured. Experiential measurements in Birmingham and NPL are in good agreement with simulation and theoretical expectation.
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Nie, Xin 1969. "Graphic user interface for power electronic research facility." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20511.
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This thesis synthesizes the development of a graphical user interface for multi-converter research facility using Visual C++ 4.0 and Microsoft Foundation Class library on Windows95 platform. The multi-converter research facility is used in flexible ac transmission system control. The design of the user interface follows the user-centered design philosophy. The main idea of the user-centered design is to produce the user interface for the convenience and efficiency of the user rather than the software designer.The user interface manages the data transfer between the hardware and user and allows the user to change the hardware settings via interactive dialogs. It also displays the current parameters running on the hardware, thus provides the user with a more convenient and efficient way of monitor the performance of the multi-converter research facility.
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Escobar-Mejia, Andres. "Indirect Matrix Converter as Standard Power Electronic Interface." Thesis, University of Arkansas, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3667722.
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The increase in the penetration levels of distributed generation in the modern power grid and its importance in future energy systems have accelerated the interest of developing new power electronic interfaces for the energy conversion process. The feasibility of applying the indirect matrix converter as the standard power electronic interface for applications with power ratings from several kW to few MW is addressed in this dissertation. Special attention is given to those applications where space dominates the power electronic requirements. The main motivation for using the indirect matrix converter is that eliminates the energy storage component in the way of a dc-link capacitor for the energy conversion process. This contributes to reduce size and weight, and potentially, increase reliability of the power electronic interface. Two main new contributions are presented. First, a new power electronic interface that allows the connection of two ac power grids through a medium- or high-voltage dc system is proposed. The new topology contemplates the use of two high-voltage dc-link converters based on the modular multilevel converter, two indirect matrix converters and two medium-frequency transformers. Second, a new sensorless control technique working in the d – q reference is developed. The controller is used to interface a distributed generation unit to the power grid when the indirect matrix converter is used as the power electronic interface. The design and performance of the proposed power electronic interface is validated through time-domain simulations and a laboratory prototype is built to experimentally validate the sensorless controller.
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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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Cantillon-Murphy, Pádraig J. "Development of three-dimensional passive components for power electronics." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/34679.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (leaves 85-88).
As component and power densities have increased, printed circuit boards (PCBs) have taken on additional functionality including heatsinking and forming constituent parts of electrical components. PCBs are not well suited to these tasks. A novel fabrication method is proposed to develop an enhanced circuit board fabrication approach which overcomes this problem. This method uses a photoresistive scaffold and subsequent metallization to realize the proposed structures. These structures are suitable as heatsinks, inductor windings, busbars and EMI shields among other applications.
by Pádraig J. Cantillon-Murphy.
S.M.
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Alvira, Mariano. "Courseware development for a laboratory class in power electronics." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33705.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (leaf 103).
This thesis introduces a new lab kit that is uniquely suited to teach power electronics: the Power NerdKit. The Power NerdKit is a self-contained prototyping system, which is easily incorporated into other systems such as an electric go-kart. Central to the kit is the card-rack prototyping area, where circuitry on PCB cards can be installed, interconnected, and tested. We present three prototyping PCB cards for use with the kit. Each of the cards has a common interconnection inter- face: up to five high current connections can be made via terminal lugs, and up to 26 low current connections can be made via card-edge connector. The first card provides solderless breadboard for constructing circuits and can connect with other cards through the standard interface. The second card is similar to the first, but is designed for circuits that must be soldered together. The last card, called the TriTotemII, implements three "totem-pole" circuits, which form the foundation of the converter topologies taught in the class. Finally the cards feature a unique method to attach oddly shaped devices using Unplated Through-hole Anchor Points. The lab exercises emphasize design.
(cont.) In Lab 1, the student: learns why switching circuits are useful; learns a few necessary control circuits; and builds a switching audio amplifier. In Lab 2, the student constructs a 1500W buck converter that drives an electric go-kart at variable speeds; they also design and build a 12W boosting power supply for a switching stereo amplifier of their construction. In Lab 3, the student designs and builds a high-voltage flyback converter and an electric fluorescent lamp ballast. Lastly, in Lab 4, the student explores how power electronics are used to drive induction and permanent magnet machines using a teaching motor specifically designed for this course.
by Mariano Alvira.
M.Eng.
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Zhu, Lu. "Thermal and electrical modeling of power electronics devices with emphasis on heat generation /." The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487948807588325.
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Guo, Yan. "Real-time parallel processing for power applications." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41602.
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The thesis describes the design, implementation and applications of two multiprocessor systems. A Multiprocessor Controller and an Extensible Modular Multiprocessor System have been built and have been used to solve problems of real-time digital control and real-time digital simulation in the power electronics and power systems areas.The Multiprocessor Controller, built around three fixed-point digital signal processors(DSPs), has been used in real-time parallel processing to control a voltage-source type pulse-width-modulated power converter. In a pole-placement control strategy with a state observer, the converter has been stabilized with its dc link capacitance reduced by a factor of as much as 120, thus making the converter a potentially practical device for High Voltage direct current transmission.
The Extensible Modular Multiprocessor System consists of modules which can be easily added in a mesh architecture to provide more computing power. Each module consists of one or two autonomous processing units (PUs) and the supporting control/interface circuits. A prototype of three modules (five floating-point DSPs) has been built and used in parallel processing to simulate a small power system with two turbo-generators operating in real time as a Transient Network Analyzer(TNA).
The power system equations are partitioned by using a new method in which the system is modeled as an interconnection of functional blocks. The power system is simulated by an interconnection of DSP modules, with one module simulating one block. The results of elaborate tests demonstrate the correctness of: (a) the new partitioning method, and (b) the design and operation of the Extensible Modular Multiprocessor System. The results further show that the new partitioning method together with the Extensible Modular Multiprocessor System form a promising approach to digitize the Transient Network Analyzer.
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Kou, Chin Fong. "Packet CDMA performance with imperfect power control." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22658.
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This work considers both single-cell and multi-cell packet CDMA cellular systems in the presence of power level variations due to imperfect power control. The teletraffic is modeled as an M/G/$ infty$ queueing system. Average error rates and outage probabilities are evaluated for single-cell and multi-cell CDMA systems. Traffic capacities in terms of a fixed average error rate or outage probability are presented. Often in the literature the analysis of multi-cell systems assumes a regular cell geometry with precisely defined boundaries. This condition is rarely met in practice. We have derived an analysis technique that does not assume a precise cell geometry, where the portable unit is connected to the base station from which it receives the highest power. In our opinion this represents a situation that is closer to reality than geographically specified cells. Both CDMA systems with two-dimensional and three-dimensional cell layouts have been considered. Numerical results for CDMA systems with different processing gains and coding gains are presented. It is shown that imperfect power control reduces significantly the CDMA traffic capacity.
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Darvish, Hossein. "Smart Power Grid Synchronization with Nonlinear Estimation." Thesis, Southern Illinois University at Edwardsville, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1589157.
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Grid synchronization is a critical concern for proper control of energy transfer between the Distributed Power Generation Systems (DPGS) and the utility power grid. Nonlinear estimation techniques are proposed to track the voltage magnitude, phase angle, and frequency of the utility grid. Instead of directly analyzing in abc coordinate frame, the symmetrical component is employed to separate the positive, negative, and zero sequences in the transformed AlphaBeta stationary coordinate frame. By using the Fortescue's Transformations and Clarke's Transformation, the number of system state variables is reduced to five. The results show that our proposed nonlinear estimation technique is efficient in smart power system synchronization. The MATLAB simulation studies have been conducted to compare the performance of the Extended Kalman Filter (EKF), the Particle Filter (PF), and the Unscented Kalman Filter (UKF). Computer simulations have shown that the efficacy of our proposed nonlinear estimation methods. It also shows that the Unscented Kalman Filter, and the Particle Filter are better estimators, because voltage synchronization problem is nonlinear, and linearization process which the Extended Kalman Filter is based on is not very accurate. The number of particles in Particle Filter can be increased to improve the accuracy, but there exists a trade off between computational effort and estimation accuracy. In our research, considering the same amount of computational complexity, we calculate the Mean Square Error (MSE) to examine the performances of different nonlinear estimation approaches. By comparing the MSE of different estimators, we prove that the Unscented Kalman Filter shows the most accurate performance in voltage synchronization for three phase unbalanced voltage. Our results have shown the potential applications of the nonlinear estimation techniques in the future smart power grid synchronization.
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Alibeik, Maryam. "Different configurations of microgrids and power converters." Thesis, Purdue University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1573479.
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This thesis proposes a two-phase microgrid system with voltages in quadrature. The two-phase microgrid system presents the following advantages: 1) constant power through the power line at balanced condition; 2) two voltages available by using a three-wire system; 3) optimized voltage utilization compared to a three-phase system; and 4) a direct connection of both symmetrical two-phase and single-phase machines. Power analysis and symmetrical components of this kind of microgrid have also been studied through this thesis. Besides the two-phase microgrid system, the hybrid DC/AC microgrid has been analyzed. Both hybrid DC/AC and two-phase microgrid need power interfaces such as power converters to be connected to the grid. Also two different types of power converters have been proposed and studied during this thesis.
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Kanten, Bethany. "Power Monitoring Device for Off-Grid Solar." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:14398556.
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Off-grid solar power systems are being used in rural, developing regions of the world to provide electricity to communities that previously didn’t have access. These systems are unable to communicate data about power generation and consumption to the organizations that install them. This information can be critical for the organization to ensure they are providing quality electricity, maintain the health of the components in their system, and evaluate the impact they are having in the community. I designed and built a device to monitor power at both the generation and AC or DC consumption sites. Once daily it sends the data to a website via text message where is it displayed to the installer. The device also stores the data locally on a microSD card. The final device abides by the key specifications set by the prior art of low cost and low power consumption. The device also addresses key challenges of off-grid monitoring including data transmission via text message, battery monitoring, reliability/ durability, and versatility with load site monitoring.
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Zupac, Dragan 1961. "ESD-induced noncatastrophic damage in power MOSFETs." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/291470.
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Electrostatic discharge (ESD) may, depending on the energy of the pulse, cause either catastrophic failures or degradation of MOSFETs. Effects of noncatastrophic positive Human-Body Model (HBM) ESD stress at the gate of power MOSFETs are investigated in this work. Noncatastrophic damage is manifested in the form of positive charge trapping in the gate oxide. In p-channel devices used in this study, the charge injection and trapping occur predominantly in the gate oxide areas lying above the p-body region. In p-channel devices used, the charge is injected mainly from the p-drain region. Based on the polarity of the pulse and the regions observed to contribute to charge injection, a model of ESD-induced charge injection from the silicon into the oxide is proposed. Finally, the effects of noncatastrophic ESD events on the radiation response of n-channel power MOSFETs are reported.
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Leong, Kennith Kin. "Utilising power devices below 100 K to achieve ultra-low power losses." Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/46807/.
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One of the main trend in the development of high power electric machines (motors, generators) is to replace the magnetic components with superconducting wires, this inevitably leads to a critical requirement from the industry (Converteam) to operate power devices at cryogenic temperatures. However, the current understanding of the behaviour power devices at cryogenic temperatures is limited, especially below the liquid nitrogen temperature of 77 K. This is a problem since most of the superconducting wires operate at temperatures below 77 K. Furthermore, it is uncertain which device type is better, if at all suited to cryogenic operation. In order to answer this, a thorough analysis of the known cryogenic behaviour of all the generic power devices was performed, including the physical behaviour of silicon at cryogenic temperatures. It is concluded that the power MOSFET is the best likely candidate for cryogenic operation. To understand the cryogenic behaviour of silicon power MOSFETs especially between the temperatures of 20 K and 100 K, a cryogenic measurement system was built to characterise different types of power MOSFETs. All the measured power MOSFETs exhibited large improvement in on-state resistance down to 50 K and non-linear degradation of breakdown voltages with lower temperatures. Various behaviour was observed below 50 K including carrier freeze-out, electric field dependent ionisation of free charge carriers and large variations in on-state resistance between identical devices. Several power Schottky diodes were also characterised and all exhibited merged PiN Schottky diode behaviour at cryogenic temperatures. Non-silicon devices such as silicon carbide power MOSFETs and gallium nitride HEMTs were also measured. Silicon carbide exhibited no improvements at cryogenic temperatures, whereas gallium nitride HEMTs may prove to be the best power device to be utilised in future cryogenic applications. Since unusual behaviour was observed in power MOSFETs below 50 K, an attempt was made to explain these phenomena using theoretical equations of semiconductor physics and analytical models of power MOSFETs. The author suggested that careful control of the dopant concentration at the accumulation region below the oxide gate is required to improve the power MOSFET operations below 50 K. Moreover, the super-junction power MOSFETs could be optimised for better cryogenic operation. It is the intention of this work to demonstrate the benefits of power MOSFET cryogenic operation in a realistic industrial application. A demonstration model was designed and simulated, this circuit uses a back-to-back power MOSFETs configuration to control the freewheeling current flowing through a high temperature superconducting coil. The electrical and thermal design of the model has been described, simulated and presented in this work.
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Sumsurooah, Sharmila. "Robust stability analysis of power electronic systems." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/37829/.
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Power electronics is the enabling technology that can put transportation on a more sustainable pathway. The key problem with power electronic (PE) systems is that they are prone to instability. Classical techniques are insufficient at assessing the stability of these systems, as they do not take into account the uncertain nature of physical systems. This thesis presents the structured singular value (SSV) method as an effective, reliable and robust stability analysis approach that justifiably incorporates uncertainties which are inherently present in physical systems. Although the SSV approach has numerous benefits, it has a few drawbacks that tend to make it hard to apply. Its theoretical framework remains complex. The practical approaches to applying the SSV method to PE systems seem lacking in the literature. The SSV approach is generally applied to linear system models while most systems are non-linear in nature. This thesis demonstrates the applicability of the SSV method to PE systems, by addressing these limitations. The work first brings deeper and clearer insights into key concepts of SSV theory. It demonstrates the significance and usefulness of the robust stability measure (SSV) in the space of multiple parametric uncertainties, through the concept of the hypercube. Secondly, it presents several practical approaches to applying the SSV method to PE systems. Finally, it develops a modelling methodology that converts a non-linear system to an equivalent linear model, suited for SSV analysis. The findings are supported by simulation and experimental results of the buck converter, permanent magnet machine drive, ideal constant power load and resistance-inductance-capacitance systems. This thesis provides the design engineer with some crucial theoretical and practical tools for applying the SSV approach to both linear and non-linear models of PE systems, while showing how to reap the full benefits of the method. It is the author's belief that the SSV method can be used as widely as classical methods, and to great effect.
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Hornik, Tomas. "Power quality in microgrids." Thesis, University of Liverpool, 2010. http://livrepository.liverpool.ac.uk/1456/.
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Rapidly increasing energy demand from the industrial and commercial sector, especially in the current climate of high oil prices, steadily reducing energy sources and at the same time increased concerns about environmental changes, have caused fast development of Distributed Power Generation Systems (DPGS) based on renewable energy. A recent concept is to group DPGS and the associated loads to a common local area forming a small power system called a microgrid. This small autonomous system formed by DPGS can offer increased reliability and effciency of future power system networks. Furthermore, the improvement of the control capabilities and operational features of microgrids brings environmental and economic benefits. The introduction of microgrids improves power quality, reduces transmission line congestion, decreases emission and energy losses, and effectively facilitates the utilisation of renewable energy resources. As a consequence of the fast expanding DPGS based on renewable energy sources, Transmission System Operators (TSO) have issued strict interconnection requirements (grid code compliance), e.g., on power quality control, reactive power control, fault ride-through etc. Among these different requirements issued by the grid operators, power quality have recently gained a lot of attention due to excessive non-linear and unbalanced loads over-stressing the power systems and causing system failure. As nonlinear and/or unbalanced loads can represent a high proportion of the total load in small-scale systems, the problem with power quality is a particular concern in microgrids. In this work, different control strategies are proposed and implemented for the grid and microgrid connected voltage-source inverters (VSI), based on H^inf and repetitive control techniques. The repetitive control, which is regarded as a simple learning control method, offers very good performance for voltage and current tracking as it can deal with a very large number of harmonics simultaneously. This leads to a very low Total Harmonic Distortion (THD) of the output voltage and/or the current even in the presence of nonlinear loads and/or grid distortions. Initially, a voltage controller proposed in the literature for microgrid applications is further developed and experimentally tested. The aim is to improve power quality and tracking performance, while considerably reducing the complexity of the controller design. The model of the plant is reduced for single-input-single-output (SISO) repetitive control design. As a consequence, the design becomes much simpler and the stability evaluation easier. Moreover, a frequency adaptive mechanism is proposed so that the controller can cope with grid frequency variations in the grid-connected mode. This mechanism allows the controller to maintain very good tracking performance over a wide range of grid frequencies. Then, a H^inf repetitive control strategy for the inverter current is proposed and validated with experiments. As a result, the power quality and tracking performance are considerably improved. In order to demonstrate the improvements, the proposed controller is compared with the traditional proportional-resonant (PR), proportional- integral (PI) and predictive deadbeat (DB) controllers. Finally, the advantages of the proposed voltage and current controllers based on H^inf and repetitive control techniques are put together for consideration in microgrid applications and experimentally tested. The proposed cascaded current-voltage control strategy is not a simple combination of the two control strategies, but a complete re-design after realising that the inverter LCL filter can be split into two separate partsfor the design of the controllers. As a consequence, the cascaded controller is able to maintain low THD in both the microgrid voltage and the current following into/from the grid at the same time. It also enables seamless transfer of the operation mode from standalone to grid-connected or vice versa. It turns out that the voltage controller can be reduced to a proportional gain cascaded with the internal model (in a re-arranged form), which can be easily implemented in real applications. Experiments under different scenarios (e.g. in the standalone mode or in the grid-connected mode, with linear, nonlinear or unbalanced loads etc.) are presented to demonstrate the excellent performance of the controllers.
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Mahmud, Shekhar. "Influence of contamination on the electrical performance of power transformer oil." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/379273/.
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Transformer failure statistics from all over the world showed that almost 30% of them were due to insulation. Large amount of those failures were due to particles in transformer oil. Main focus of this research is to effects of contamination on electrical performance of transformer oil. A literature review of major causes of transformer failure, breakdown mechanisms of transformer oil has been conducted. The experimental setup and results from the pressboard-dust-contaminated transformer mineral oil test are also discussed. Several experiments have been carried out with cellulose particle contaminated transformer mineral oil. The experiments of bridge formation are conducted under the influence of DC, AC, and DC biased AC voltages. Samples with several levels of contaminant are tested under different voltage levels. The influence of different electrode systems is also tested i.e. bare electrode, covered electrode, bare electrodes with paper barrier, spherical and needle – plane electrodes. These experiments revealed that the bridges are always formed under the influence of DC voltages. The particles are attracted towards high electric field due to Dielectrophoretic (DEP) force and become charged once in contact with the electrode surface. Long fiber particles were attached to the electrodes and aligned parallel to electric field towards the other electrode. More particles attached to the initial fibers and the process continued until a full bridge formed between the electrodes. The conduction current increased with contamination levels as the bridge thickened with increment of contaminations. There is no complete bridge formed under AC electric field. The particles were attracted to the high electric field and attached to the electrodes but the particles are not been able to charge before the polarity of AC electric field alters with spherical electrodes. The current for AC remained unchanged with the increment of particle contamination levels as there is no bridge formed. However, when the DC biased AC signal is applied, the bridge is formed for all the three voltage levels tested. DC and AC breakdown tests were also conducted for several contamination levels. Experiments with kraft paper covered spherical electrodes confirmed that a tightly bonded cover does not stop the bridge; only a loose bonded cover stopped the bridging. Another test with a paper barrier between bare electrodes also did not stop the bridging. Partial discharge (PD) and breakdown test of the contaminated transformer oil is also measured but the results were not conclusive. An initial mathematical model of pressboard dust accumulation using Finite Element Analysis (FEA) software, COMSOL multiphysics has been conducted. The result of the simulation model for charging-discharging and bridging showed similar trend as experimental results. There are a number of changes that can result in improved simulations. There are several variables affecting the simulation i.e. the pressboard dust particle shape, size, conductivity of impregnated pressboard fiber etc.
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Brynjolfson, Ian. "Dynamic clock management circuits for low power applications." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32954.
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Low power methods employing dynamically controlled clock rates offer potentially powerful energy saving capabilities. Dynamic clock management is a system level technique that benefits from the relationship between operating frequency and power consumption through the variation of clock speeds based on demand. This thesis provides robust and scalable clock management circuits for dynamic clock control. A complete Programmable Clock Manager (PCM) has been designed, implemented, integrated into a Systems-on-a-Chip and tested. The PCM incorporates two novel circuits who enable dynamic clock management, the Range Shifting Phase-Locked Loop (RSPLL) and the Dynamic Programmable Clock Divider (DPCD). The self-calibrating RSPLL extends operating bandwidth while reducing jitter. Such a Phase-Locked Loop design also provides easier system-level integration and range-independent usage. The design is scalable to the higher bandwidths and lower voltages, associated with future technologies. The DPCD is capable of dynamic clock division without exhibiting glitches. Both of these robust circuits are easier to use for all clock managment purposes.
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Dixon, Juan W. (John Walterio). "Boost type PWM rectifiers for high power applications." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75864.
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The present industrial practice of ac to dc rectification uses diode or thyristor bridges which are harmonic polluters and poor power factor sources. The research of this thesis is directed towards exploiting fast, gate-turn-off semiconductor switching devices and PWM techniques in order to develop a new generation of rectifiers with nearly sinusoidal current waveforms operating at unity or even leading power factor. The scope of the investigation is restricted to the Boost rectifier (as opposed to Buck) which has bilateral power transfer capability through bidirectional current flow in the dc link.The stand-alone, Boost Type PWM Voltage Regulated Rectifier was originally conceived as being Direct Current Controlled. The work of the thesis advances the control methodology by replacing the inner hysteresis current feedback loop by Indirect Current Control, which uses the standard sinusoidal PWM technique. In the process, the cost of two expensive high quality current transducers is avoided. Furthermore, Sinusoidal PWM has more predictable characteristics harmonics for filter design on harmonic elimination purposes.
The thesis addresses the problem of upscaling the voltage and current ratings of the rectifiers. Many semiconductor switching devices have inherent difficulties in voltage and current sharing when connected in series and/or in parallel. These difficulties are avoided by connecting rectifier modules in series and/or in parallel. Different topologies for both series and parallel connections have been analyzed mathematically. Digital simulations and experiments have confirmed the analyses.
The research was carried out by building 2 kW size laboratory models which were subjected to demanding experimental tests. Experimentally justified mathematical models have been developed and have successfully been used in predicting stability boundaries and in the dynamic compensation of feedback control.
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Godbole, Rahul Pushpak. "Design of a Flexible DSP Based Controller Hardware System for Power Electronics Applications." NCSU, 2008. http://www.lib.ncsu.edu/theses/available/etd-03252008-173146/.
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This thesis proposes the concept of a universal controller hardware system for power electronics applications. With the presence of generic interfaces and communication schemes, this system can be used in various other control scenarios. A prototype hardware system incorporating a high performance floating point digital signal processor (DSP) and a powerful field programmable gate array (FPGA) has been built to demonstrate the concept of real-time hardware simulation. Prior to being deployed for control of a complete power electronics system, an intermediate step that would yield more information pertaining to system timing is the hardware simulation enabled by such a board. Extracting maximum throughput from this system with a few innovative schemes has been another goal of this project. In order to achieve this objective, the embedded peripherals of the Texas Instruments C6000 series DSP have been programmed to facilitate a higher degree of parallelism. The core of this thesis deals with the different sub-systems that comprise the real-time controller (RTC) board, and their interaction with one another. One of the novel schemes proposed in this thesis involves the on-board communication between the DSP and several analog-to-digital converter (ADC) chips using the multi-channel audio serial port (McASP) peripheral. The efficacy of this concept is made possible by robust software architecture, enabled by the enhanced direct memory access (EDMA) peripheral. In addition to the DSP peripheral activity, significant processing capability is offered by the Cyclone II series FPGA. The option of universal connectivity is provided over either Ethernet or USB. The FPGA also provides a platform for developing a complete system with an embedded 32-bit processor. The RTC board prototype can be used for power electronics applications with the addition of certain interface boards, which can be readily developed.
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Zhuang, Fulin 1956. "Optimal generation unit commitment in thermal electric power systems." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75896.
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This thesis is devoted to the optimal commitment of generation units in an all-thermal, single or multiple area, power system. The problem, known as unit commitment, is a nonlinear mixed program typically with thousands of 0-1 integer variables and diverse constraints. An exact optimal solution to the problem is only possible via (explicit or implicit) enumeration, which requires a prohibitively long computation time for large problem instances.Two optimization approaches, Lagrangian relaxation and simulated annealing, are explored in this thesis for efficient and near-optimal unit commitment.
Lagrangian relaxation combines the solution of the dual of the unit commitment problem with feasibility search to obtain primal feasible solutions. The feasibility search is necessary because a solution to the dual seldom solves the primal, and because little theory is available to bridge the optimal dual and primal solutions. In this thesis, several new feasibility search procedures to find a near-optimal primal feasible solution from the dual solution are developed and tested. These procedures are independent of the data constituting different problem instances, and are more rigorous and systematic than the existing ones. With these procedures, Lagrangian relaxation is successfully and efficiently applied to both single and multiple area unit commitment.
Simulated annealing exploits the resemblance between a minimization process and the cooling of a molten metal. The method generates feasible solution points randomly and moves among these points following a strategy which leads to a global minimum in a statistical sense. Simulated annealing is very flexible for handling diverse and complicated constraints, such as those typical of the unit commitment problem. Simulated annealing is analyzed, evaluated and implemented for unit commitment in this thesis.
Five major algorithms, proposed in this thesis for unit commitment and reserve-constrained economic dispatch, are extensively tested and compared by numerical simulation on sample power systems of 10 to 100 units. The simulation results show the efficiency of the tested algorithms for large-scale unit commitment and demonstrate the general applicability of simulated annealing. A comparison with the priority list method and a study of the convergence rates of the subgradient type algorithms are also included in the simulation.
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Li, Jing. "Dynamics of power systems with wind power generation and the fractional frequency transmission system." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6465/.
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Under pressure for low carbon emissions and environmental protection, large scale wind farms are constructed and integrated into power systems to meet energy demands. On the other hand, the long distance transmission for large scale wind power and conventional power plants is another technical issue in modern power systems. These two challenges stimulate the research and development of wind energy and the fractional frequency transmission system (FFTS). Thus, the research of this thesis focuses on the dynamics of power systems with wind power generation and the FFTS. This thesis can be divided into the following three parts: Firstly, the influence of wind farms on the subsynchronous resonance (SSR) of conventional power systems is systematically examined. Both eigenvalue analysis and time domain simulations are conducted to examine the influence of wind farms. Secondly, the FFTS is proposed to deliver the energy from large scale offshore wind farms. The small signal stability of the FFTS with wind farms is studied. To improve the damping performance, a proper controller for the FFTS is also proposed. Thirdly, the FFTS is also applied in grid interconnections. The power flow controller for the FFTS is also proposed in this application.
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Abid, Abubakar. "Ingestible electronics without batteries : power and communication for gastroresident devices." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107102.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 77-80).
In this thesis, I introduce a novel ingestible electronic device designed to reside inside the stomach for weeks or longer with both wireless communication and wireless powering capabilities. The device is powered by a transmitter outside of the body via wireless power transfer through 5 to 6 cm of tissue, while keeping under specific absorption of radiation limits. Electromagnetic theory and microwave simulations identified the optimal region of operation for transmitting power through tissue as around 1 GHz. Small loop antennas fabricated to fit onto a circuit board the size of a pill capsule exhibited power transfer efficiencies of around -45 dB when tested ex vivo in pig stomach tissue. Choice of electronic components for rectification, sensing, and wireless communication are also discussed, as well as electrical and material characterization of an encapsulated device, to show that an end-to-end wireless ingestible electronic device is feasible for gastroresident applications.
by Abubakar Abid.
M. Eng.
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Huang, Hui. "Lifetime prediction for power converters." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/54844/.
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Renewable energy is developing rapidly and gaining more and more commercial viability. High reliability of the generation system is essential to maximize the output power. The power inverter is an important unit in this system and is believed to be one of the most unreliable parts. In the case of wind power generation, especially in off-shore wind, when the system reliability requirement is high, a technique to predict the inverter lifetime is invaluable as it would help the inverter designer optimize his design for minimal maintenance. Previous researchers studying inverter lifetime prediction, focus either at device level such as device fatigue damage models, or at system level which require experimental data for their selected device. This work presents a new method to estimate the inverter lifetime from a given mission profile within a reasonable simulation time. Such model can be used as a converter design tool or an on-line lifetime estimation tool after being configured to a real converter system. The key contribution of this work is to link the physics of the power devices to a large scale system simulation within a reasonable framework of time. With this technique, the system down time can be reduced and therefore more power can be generated. Also, the failure damage to the system is avoided which reduces the maintenance cost. A power cycling test is designed to gather the lifetime data of a selected IGBT module. Die-attach solder fatigue is found out to be the dominant failure mode of this IGBT module. The accuracy of widely accepted Miner’s rule, which accumulates damage linearly, is discussed and a nonlinear accumulation method is promoted to predict the lifetime of power inverters.
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De, Almeida Katia Campos. "A general parametric optimal power flow." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28660.
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The objective of an Optimal Power Flow (OPF) algorithm is to find the steady-state operation point of a generation-transmission system which minimizes a pre-specified cost function and meets a set of operational and/or security constraints. OPF algorithms are among the tools present in many Energy Management Systems and their usefulness is increasingly being recognized by power utilities.This thesis presents an algorithm which uses the parameters existing in the OPF problem to find its solution. These parameters can be in the objective function or the equality or inequality constraints. This algorithm is applied to a parameterized OPF model built according to the following criteria: (i) when all parameters present in the model are relaxed from their given levels, a solution can be trivially found for this parameterized problem and (ii) when all parameters are returned to their original values, the parameterized model is equal to the original OPF. As the initially relaxed parameters are returned to their original values, they define a sequence of OPF problems which converge to the original one. The algorithm is designed to track the optimal solutions of these intermediate problems until the optimum of the original OPF. This tracking is made in a systematic manner. By using a binary search or a linear prediction method, the algorithm finds the maximum increment of the parameters which allow only one inequality to be fixed at its limit or to be released. The parameters are then adjusted to their new values, defining a new OPF problem with known optimal active feasible set. As a consequence, the optimal solution of this new problem can be easily found by solving the first order optimality conditions by Newton's method. In this way, the optimum is tracked from one active feasible set to the next until the parameters reach their original values.
The parameterization permits the solution of the OPF problem for a fixed and variable load using the same mechanism described in the previous paragraph. As a result of this systematic tracking, the method is robust and able to provide a very good insight about the behaviour of the OPF solutions. In addition, the main difficulties encountered in solving the OPF problem are easily visualized and, in particular, the approach permits the differentiation of the potential causes for the failure of the tracking process, including the identification of unsolvable cases. The sensitivities of the optimal solution as a function of the parameters are also by-products of the method; including the Bus Incremental Costs and the System Incremental Cost as functions of the loads. The approach is also flexible enough to permit the simulation of line contingencies and of Flexible AC Transmission Systems (FACTS devices). The algorithm developed was tested in numerous networks with different objective functions and initializations and the results demonstrated the potential of this technique.
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Atanackovic, Djordje. "intelligent power system design." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41969.
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In this thesis, the concept of an intelligent system for the design and planning of electric power systems is developed. Such a system serves to preserve the vast body of power system design knowledge by identifying, structuring and consolidating it into one easily accessible source. The intelligent system can then be used to support experienced power system planners or for training purposes. The main planning and design activities considered include the design of a complete power system or of specific subsystems such as a substation or a transmission corridor. The principal features and main components of this general intelligent system, called PSIDE, are delineated.A general methodology and a design tool were then devised for modelling and using this kind of knowledge. The object-oriented strategy was found to be the most suitable due its powerful capabilities to naturally represent the structure and behaviour of power systems. Thus, PSIDE is based on object-oriented knowledge models for design tasks such as point-to-point transmission design, insulation coordination as well as protection system and substation design.
In order to validate the proposed concepts as well as the object-oriented paradigm adopted for their realization, a substation design module (SIDE) was fully developed and tested.
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Kazemtabrizi, Behzad. "Mathematical modelling of multi-terminal VSC-HVDC links in power systems using optimal power flows." Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2937/.
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An advanced mathematical model of the Voltage Source Converters (VSC) suitable for optimal power flow (OPF) solutions using Newton’s method for augmented Lagrangian functions has been developed in this research, using first principles – this model is far more flexible and realistic than the existing VSC models aimed at fundamental frequency power systems studies. The nodal active and reactive powers of the VSC are suitably modified to accommodate more complex models corresponding to back-to-back, point-to-point and multi-terminal High Voltage Direct Current (HVDC) transmission links, within Newton’s OPF algorithm – the various model representations of the HVDC links use two or more VSC models, resulting in a new and more powerful way of VSC-HVDC representation. These models are subsequently used to interconnect otherwise independent AC systems. The new models are developed and presented in quite a comprehensive manner throughout the thesis. System simulations are carried out in order to illustrate the VSC-HVDC modelling flexibility in representing various modes of VSC-HVDC operation by selecting a range of control modes. It should be noticed that a straightforward extension of the VSC model yields a new STATCOM model of unrivalled modelling flexibility. It has been observed that the new models do not impair the strong convergence characteristics exhibited by Newton’s iterative method. As an integral part of this research, a computer program written in MATLAB has been developed to perform OPF system simulations. The program is capable of solving conventional power systems of an arbitrary complexity, multi-terminal VSC-HVDC transmission links and combined AC/DC transmission systems. It follows that less complex systems comprising one or more STATCOM, back-to-back and point-to-point VSC-HVDC can be solved with ease, using the Newton OPF computer program. It should be brought to attention that existing power systems commercial or distribution free packages with OPF facilities do not possess the advanced modelling capabilities exhibited by the new VSC model and its extensions, presented in this thesis.
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Khan, Farzana Noor. "Gallium nitride class-F power amplifier for UMTSWCDMA applications." Thesis, University of Ottawa (Canada), 2008. http://hdl.handle.net/10393/27697.
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The importance of wireless communications in today's telecommunications industry is indubitable. Wireless technologies are used in almost every aspect of our everyday life. Universal Mobile Telecommunications System (UMTS) technology has already implemented 3G communication standard for mobile communications.
Power amplifiers are the most power consuming unit in wireless communication systems. The power amplifiers used in UMTS devices need to be highly efficient. Improved efficiency not only extends the battery life but also reduces the DC power consumption, transmitter size and weight. Although the power amplifiers used in existing second generation GSM (Global System for Mobile Communications) transmitters are highly efficient, they cannot be applied to UMTS/WCDMA since GSM uses the constant envelope feature of GMSK (Gaussian Minimum Shift Keying) modulation which introduces phase variations only. In UMTS, a WCDMA system with QPSK modulation is used where both phase and amplitude variations are introduced by the modulation. The power amplifiers designed for WCDMA need to satisfy the contradicting operation requirement between linearity and efficiency.
In this thesis, a highly efficient class F power amplifier has been designed for WCDMA band with a center frequency of 2.14 GHz and bandwidth of 5 MHz using GaN transistor. The amplifier has been simulated using a high frequency circuit simulator namely, the Agilent Advanced Design System (ADS). The simulated results have shown a Power Added Efficiency (PAE) of 76.8% for an optimum input power of 30 dBm. The amplifier was then fabricated and measured. Measurement has shown a PAE of 75.9% for an optimum input power of 29.6 dBm which is in good accordance with the simulated results. Based on a literature review, and to the best of our knowledge, our circuit exhibited one of the highest measured PAE for a GaN class-F amplifier working at 2.14 GHz. The value of third and fifth order IM products of the designed class F PA is -13 dBc and -21 dBc respectively at peak power and -28.5 dBc and -43 dBc respectively at 6 dB back-off from peak power.
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Hamoui, Anas. "Current, delay, and power analysis of submicron CMOS circuits." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0022/MQ50618.pdf.
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Maksimcev, Mirko D. "Energy considerations in power system damping by reactorcapacitor switching." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23370.
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Flexible AC transmission systems (FACTS) technology is an emerging new technology which can be efficiently used in power system damping. Objectives of this study are the considerations of the energy flow involved in power system damping by functional switching of series capacitors and/or reactors. The principal questions are how the energy transiently flows through the network and what is its impact on damping of mechanical oscillations.The analytical studies (covered in Chapter 1) reveal that the magnetic and electrostatic energy are constantly stored in the reactive components of the transmission system. The energy stored in a series compensated line is greater than the energy stored in an uncompensated line of equal transmission capability. The transient energy flow caused by characteristic switching in transmission systems is studied analytically in Chapter 2. Switching of an additional line or switching of series capacitors initiates transient charging/discharging of the line towards its new steady-state energy level which is always associated with losses. Power transfer characteristics of the systems which are equivalent in steady-state operation (parallel lines vs. an equivalent series compensated line) have quite different transient power transfer characteristics. These differences are related to different stored energies in such systems. System sources participate in all transient energy flow phenomena.
The impact of series compensation switching upon the mechanical oscillation damping was demonstrated by simulations presented in Chapter 3. Thyristor switched variable series compensation (VSC) is simulated in order to verify the conclusions of the analytical studies regarding the charging/discharging energy of the line.
The switching of reactive power components for the purpose of power system oscillation damping involves significant energy impulses in and out of the machines. Therefore, stability studies have to be performed by simulation which involves detailed representation of electromagnetic phenomena (EMTP for example).
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Luo, Changling 1980. "Fluctuating wind power penetration as limited by frequency standard." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=83873.
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Fluctuating wind power is due to wind turbulence and is the part which should be filtered out leaving behind the more predictable mean wind power which can be traded in the hourly energy market. The power fluctuations cause the frequency of electric utility to deviate from the 60Hz standard. This thesis is concerned with estimating the maximum fluctuating wind power before the 1% deviation from the 60 Hz standard (required by some utilities) is exceeded. To keep the thesis manageable, the scope is narrowed to thermal power plants with governor speed control but no Automatic Governor Control (AGC). This thesis shows that each governor speed control system provides energy storage buffer to attenuate the wind power fluctuations and arrives at the estimate that the fluctuating wind power penetration is conservatively around 5% of the generation capacity of the utility grid. The methodologies used to reach this estimate are: (i) Transfer Function analysis of power plants; (ii) digital simulations using HYPERSIM. Through the research, an innovative method of predicting the frequency deviation in an electric grid with multiple power plants has been developed and validated by simulation.The thesis also shows that fluctuating wind power penetration can be higher when there are filtering also in the wind farms. Wind turbines, with small inertias, driving constant speed squirrel cage induction generators are found to provide poor filtering. On the other hand, the fluctuating wind power penetration limit is increased to 18% in the case of wind turbines, with large inertias, driving variable-speed doubly-fed induction generators (DFIG) with decoupled P-Q control to implement optimal wind power acquisition.