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1
Gurunlu, Cemil. "Single-phase operations of three-phase generators." Thesis, Loughborough University, 1986. https://dspace.lboro.ac.uk/2134/32922.
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The ever-increasing demand for power, and the correspondingly greater complexity of power systems, is leading to more severe problems of system reliability. Modern society is so dependent on the usage of electrical power that even a short interruption of service can cause serious problems. A public utility cannot be expected to provide a perfect power supply, since many of the possible causes of a power disturbance are beyond its control. The windings of small diesel-driven three-phase generator sets are often capable of being connected in either a zig-zag or an Edison-delta arrangement, to provide a single-phase supply for standby or emergency purposes. Although many of these generators are genuinely on standby (i.e. they are brought into operation only as a result of a system failure), many others operate continuously in situations where no mains supply is available. The thesis aims to investigate both the steady-state and the dynamic performance of a three-phase salient-pole generator, when reconnected in either a zig-zag or an Edison-delta configuration, and to provide a performance comparison with the more familiar modes of single-phase operation involving line-to-line and line-to-neutral loading. Symmetrical components are used to investigate the steady-state performance and a phase model is used to determine both the steady state and transient performance. Analytical expressions are obtained for the short-circuit currents for various generator connections by utilizing the modified Clarke transformation. The theoretical results from various models are compared with experimental results on a test machine. Losses, efficiency and voltage waveforms for various generator connections are experimentally obtained for the test machine. Results are discussed and suggestions for future research are included.
2
Yunus, Haroon Iqbal. "Single phase active power filters." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/13282.
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Reddy, M. A. "Single phase heat transfer enhancement." Thesis, University of Manchester, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616903.
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This thesis presents investigations into the enhancement of heat transfer inside tubes using HiTRAN® tube inserts manufactured by Cal Gavin Ltd. The applicability of heat transfer enhancement in vertical thermo syphon reboilers was investigated using a computer simulation. In vacuum operation, reboilers can have a significant subcooled length (as high as 60 % of the tube length). Heat transfer coefficients in this region are lower than in the two-phase region. Using tube inserts, an increase is made in the heat transfer rate occurring in the sub-cooled region and, a corresponding increase in the length of the tube subjected to two-phase heat transfer and improvement of heat transfer performance results. Geometric variables of the tube insert were investigated experimentally, to study their influence on heat transfer and pressure drop performance. Loop density, loop wire diameter, core wire diameter, loop material and uniformity of loop density were investigated. Two experimental facilities were designed, commissioned and constructed to measure the heat transfer and pressure drop performance of these tube inserts. The new rig at UMIST is located in a flameproof location and was constructed with the intention of investigating a wide range of other processes in the future. Two tube inserts were tested over a Reynolds number range of 200 to 200000 using water as the working fluid. Adiabatic, cooling and heating tests were performed using an inside tube diameter of28.25 mm. At the Cal Gavin Ltd. facility, the rig was redesigned to extend the operating range of data collection. It was enhanced by the provision of automatic data collection, improved accuracy of temperature measurement and new equipment to allow cooling experiments. Tube inserts were tested between a Reynolds number of 100 to 2000 using a viscous oil as the working fluid. Again adiabatic, cooling and heating tests were performed. An inside tube diameter of 21.18 mm was used in the maj ority of the tests, but some preliminary results using a tube diameter of 28.45 mm are also reported. Using the results of the experimental work, pressure drop performance was correlated using an approach similar to that used for packed beds. It was found that 90 % of the data were correlated between ± 15 % of the prediction using specific insert dimensions and inside tube diameter. Further investigations into the prediction of heat transfer coefficients were made. However no general correlation could be developed from a fundamental basis, to predict heat transfer across the full range of Reynolds numbers investigated in this study. A recommendation is made for a suitable correlation. The influence of the insert geometry was associated with the fundamental pressure drop and heat transfer performance of the tube insert, leading to recommendations for the optimisation of tube insert design.
4
Magozore, Caxton. "DSP phase angle controlled three phase to single phase uninterruptible power supply." Master's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/5177.
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Garber, Edward Martin. "Surface acoustic wave single-phase unidirectional transducers and phase weighting." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15225.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.
Bibliography: leaves 245-253.
by Edward Martin Garber.
Ph.D.
6
Xue, Jing. "Single-phase vs. Three-phase High Power High Frequency Transformers." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/32919.
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This thesis proposes one comparison methodology for single and three-phase high power high frequency transformers in power conversion systems. The objective is to compare the volume of the transformers. And single and three-phase Dual Active Bridge Converter (DAB1 and DAB3) topologies with single and three-phase isolating transformers are selected for the transformer comparison. Design optimization of power transformer has been studied and simplified models have been built for the single and three-phase transformer design optimization in this work, including assumptions for core shapes, materials, winding structures and thermal model. Two design methods have been proposed according to different design constraints, named T â B Method and J â B Method separately. T â B Method is based on feature of the core, which has the major limits of maximum flux density and temperature rise. The flux density should not reach the saturation value of the core, and temperature rise should meet specifications in different applications to assure the performance of the core (permeability, saturation flux density, and core loss) and the insulation of the wire. And J â B Method starts from the comparison of area product in conventional design method. The relationship between area product of transformer cores and the flux and current of the transformer in design is analyzed. There is specified relationship between area product of single and three-phase transformers if flux and current densities are specified for both. Thus J â B Method is proposed with the design constraints of specified current and flux density. Both design methods include both single and three-phase transformer design.
One example case for single and three-phase transformer comparison is selected as high power high frequency DAB conversion system. Operation principles are studied for both DAB1 and DAB3 based on previous work. And transformer design based on the T â B and J â B Methods are carried out and transformer volumes are compared. And results show that three-phase transformer has little benefit in volume or thermal than single-phase transformer, when they are utilized in single-phase DAB and three-phase DAB converters separately. Scaled-down single and three-phase DAB systems have been built and volume and thermal tests have been carried out.Master of Science
7
Beber, DG. "DSP controlled three phase to single phase uninterruptible power supply." Master's thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/5244.
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Includes bibliographical references.With the increase in use of electronic equipment such as personal computers, network stations and AC drive conrollers, an increased "polution" of the AC mains has resulted in the form of unwanted harmonics generated by the switching currents associated with these devices. Combined with the problem of mains "pollution" is the problem of balancing a large number of single phase loads onto a three phase supply, such as in a large computer network. This has resulted in more frequent supply voltage failure, causing substantial data and financial loss and in the extreme case death due to hospital equipment not being powered. Thus the need for an uninterruptible power supply (UPS) which is capable of resolving these problems. Taking these considerations into account, a three to single phase converter topology was developed and tested, using a Texas Instruments TMS320F243 Digital Signal Processor (DSP) for control of the system. The topology is based on a technique that utilises minimal semiconductor devices whilst still allowing for sinusoidal current to be drawn from the mains supply.
8
Stihi, Omar. "Single phase controlled current PWM converter." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63844.
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Wong, Kwan Butt Albert. "Aspects of single-phase motor performance." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390215.
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Blewitt, Warren. "Improvements to Single Phase Grid Connected Inverters." Thesis, University of Newcastle Upon Tyne, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506423.
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Salamah, Ahmed Mohamed Abdelaziz. "Parallel operated, grid connected, single-phase inverters." Thesis, University of Strathclyde, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501881.
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Mills, Carlo Juan. "Supply-friendly single phase uninteruptible power supply." Master's thesis, University of Cape Town, 1998. http://hdl.handle.net/11427/16095.
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Includes bibliography.Uninterruptible power supplies (UPS) maintain a constant supply of power to a critical load. The distinguishing features are a fixed voltage and frequency, low harmonic content and the ability to supply the load for a period of time after the incoming supply has failed. The document begins by identifying the typical power-line disturbances and their effect on various types of equipment. Together with the power conditioners used to suppress these disturbances, various UPS standby, line-interactive and on-line configurations are introduced. Next, the possibility of modifying a locally manufactured UPS to meet the design specifications is investigated. The performance of the system under load is evaluated, and forms the basis for the following decision. Due to the large number of modifications required and the inflexibility of local UPS topology, an alternative topology is adopted. In the new topology a power factor corrector, constructed around a DC to DC boost converter, interfaces with the incoming AC line. It delivers a half sinusoidal current into the DC bus. An IGBT inverter using sinusoidal unipolar pulse-width modulation regenerates the AC load voltage after filtering through a LC-filter. The DC bus voltage ripple is reduced by synchronising the inverter load and power factor corrector current while the battery pack maintains the DC bus during a power failure. The power factor corrector employs a dedicated analogue controller chip while a MCS-51 microcontroller generates the inverter PWM, provides the remote monitoring facilities, battery charging and performs general support tasks. The total harmonic distortion of the input current is measured at less than 4% while the power factor remained above 0.99 over the entire load range. The ripple regulator reduced the DC bus voltage ripple without any noticeable effect on the load. Under maximum load, the steady state output voltage is maintained during the -20%, +10% variation in the incoming line voltage. However, the transient response fails to meet the 5% design specification. A 0-100% load step results in a 7% drop in the output voltage while the loss of the load results 10% jump in voltage. System efficiency is measured at 85%. It is the lack of processing power, precluding the use of floating point or an optimal control algorithm, which ultimately compromises the performance of the system. It is recommended that the microcontroller be replaced with a 16-bit processor or digital signal processor to provide the extra computational power needed to optimise the UPS response. To improve the voltage regulation, it is recommended that the control include an inner current loop while the switching frequency should be increased to reduce the energy storage in the output filter. Further adjustments and refinements to the topology are suggested in the final chapter.
13
Kumar, Rajiv. "Programmed harmonic reduction in single phase and three phase voltage-source inverters." Ohio : Ohio University, 1996. http://www.ohiolink.edu/etd/view.cgi?ohiou1178302407.
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Gundersen, Bjørnar. "An investigation on gridconnectable single phase photovoltaic inverters." Thesis, Norwegian University of Science and Technology, Department of Electrical Power Engineering, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9108.
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Several inverter topologies for use with power conditioning of photovoltaic modules were investigated with both national and international requirements in mind, as well as also practical challenges and the ability to be user friendly for ordinary people. A good inverter topology should also be low cost, have a high efficiency and have a good output power quality. In addition several filter possibilities was investigated, and it was concluded that the LCL-filter was the best for the given conditions, since it attenuated the unwanted frequencies the best with relative small filter parameters. Five different inverter topologies was then presented and investigated: A hybrid multilevel inverter, a full bridge inverter, a series resonant buck-boost inverter, a flyback converter with unfolding H-bridge inverter and a series resonant converter with unfolding H-bridge inverter. After an investigation of the above mentioned criteria, two of the inverter topologies, the H-bridge inverter and the hybrid multilevel inverter, were considered better than the rest for the given requirements and purposes. These were then closer analysed with the computer simulation programs SIMULINK and SPICE in order to find quantitative arguments about which topology was the best under the above mentioned conditions. Filter parameters were also quantified. From this it was found that the hybrid multilevel inverter was 0.5 to 1 percent point more effective than the H-bridge, at the same time the total harmonic distortion was significantly better, approximately five to ten times better than the H-bridge inverters total harmonic distortion. This means that the hybrid multilevel inverter may have a considerably cheaper filter. Both of these factors contributed so that the hybrid multilevel inverter was regarded the better topology and this topology was selected for further tests. The last simulation was about finding good switches to equip the hybrid multilevel inverter with. Here it was found that the decisive factor for the low voltage bridge was quick switches, whereas for the high voltage bridge it was more important to have switches with low resistance when turned on. The chosen switches were STY60NK30Z and BSC520N15NS3 G for the low voltage bridge. In addition it was meant to perform a laboratory experiment with the selected topology, but because of a delay with the deliverance, the test object did not arrive at time, so the experiment could not be done.
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Botne, Kjetil Kandal. "Modeling wax thickness in single-phase turbulent flow." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for petroleumsteknologi og anvendt geofysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19307.
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Oil and gas transport is today a vital part of the industry. Oil cooled during transport in pipelines may precipitate paraffin wax. Precipitated wax may deposit on pipe walls and cause flow restrictions. Deposition models are used to understand and predict deposition of solids. A deposition model can help predict wax problems before a pipe line is set into operation. If the amount of deposited wax is predicted it can help operators to develop removal plans and strategies. A total of 21 wax deposition experiments performed by others were digitized and evaluated. The logarithmic deposition-release model showed a good match with 18 of the experiments. The experiments tested the effect of varying flow rate, temperature or both. Most experiments behaved as expected when flow rate and temperature were varied. The deposition-release model consists of two coefficients, k1 and k2. Both coefficients were evaluated against wall shear stress for the varying rate experiments. The coefficients in the varying temperature series were evaluated against the temperature driving force. Linear trends between most coefficients and physical parameters were found. These linear trends lead to the development of four models that predict wax deposition. The models use either wall shear stress, the temperature driving force or both as an input. All models produce similar results. Each model was based on an experimental series. A study of a real pipeline with wax deposition was also investigated. Temperature and viscosity calculations matched well with values used in the study. The study reported calculated wax thickness based on measurements of pressure drop. The pressure drop method was evaluated and explained. The method does not consider an altered pressure drop due to increased pipe roughness and non-evenly distribution of deposits. Both of these effects will increase the pressure drop. It was found that neglecting these will cause the calculated thickness to be overestimated. Because of the overestimation of thickness it was hard to get an accurate match with models.
16
Remley, Timothy J. "Single-phase heat transfer in a trapezoidal channel." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/22212.
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Jenkinson, Graeme Craig. "The design of single-phase switched reluctance motors." Thesis, University of Leeds, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405002.
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Chaturvedi, Praveen. "Single phase multicomponent flow simulation in porous media." Ann Arbor, Mich. : ProQuest, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3307176.
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Thesis (Ph.D. in Applied Mathematics)--S.M.U.Title from PDF title page (viewed Mar. 16, 2009). Source: Dissertation Abstracts International, Volume: 69-04, Section: B, page: 2354. Adviser: Zhangxin Chen. Includes bibliographical references.
19
Montoya, Higinio Ariel. "Protection Against Ungrounded Single Phase Open Circuit Faults in 3-Phase Distribution Transformers." DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/1869.
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This thesis explores the impacts and behavior of 3-phase distribution transformers when subject to ungrounded single phase open circuit faults. A simple 3-phase system is modeled using MATLAB Simulink and operation under fault conditions are simulated and studied. Simulation results are confirmed via lab experimentation. Finally, a robust detection and protection method using neutral current injection (as proposed in industry literature) is built and demonstrated.
Electric utility operating experience has demonstrated that all too often, loads on 3-phase distribution transformers are not adequately protected against an ungrounded single phase open circuit fault (commonly called “single phasing”). This type of fault is amongst the least understood and hence the least protected against. This is especially true at end of transmission system radial feeds where 3-phase transformers can re-create the opened phase voltage due to a variety of effects including magnetic coupling, voltage loops and loading effects. Operating experience in the nuclear power industry has shown that the results can be catastrophic especially considering the impacts to motor loads. Impacts can result in unavailability of emergency loads, tripping of motor protection circuits or even motor damage and failure.
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Thacker, Timothy Neil. "Phase-Locked Loops, Islanding Detection and Microgrid Operation of Single-Phase Converter Systems." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/29281.
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Within recent years, interest in the installation of solar-based, wind-based, and various other renewable Distributed Energy Resources (DERs) and Energy Storage (ES) systems has risen; in part due to rising energy costs, demand for cleaner power generation, increased power quality demands, and the need for additional protection against brownouts and blackouts. A viable solution for these requirements consists of installation of small-scale DER and ES systems at the single-phase (1Φ) distribution level to provide ancillary services such as peak load shaving, Static-VAr Compensation (STATCOM), ES, and Uninterruptable Power Supply (UPS) capabilities through the creation of microgrid systems. To interconnect DER and ES systems, power electronic converters are needed with not only control systems that operate in multiple modes of operation, but with islanding detection and resynchronization capabilities for isolation from and reclosure to the grid.
The proposed system includes control architecture capable of operating in multiple modes, and with the ability to smoothly transfer between modes. Phase-Locked Loops (PLLs), islanding detection schemes, and resynchronization protocols are developed to support the control functionality proposed.
Stationary frame PLL developments proposed in this work improve upon existing methods by eliminating steady-state noise/ripple without using Low-Pass Filters (LPFs), increasing frequency/phase tracking speeds for a wide range of disturbances, and retaining robustness for weakly interconnected systems.
An islanding detection scheme for the stationary frame control is achieved through the stability of the PLL system interaction with the converter control. The proposed detection method relies upon the conditional stability of the PLL controller which is sensitive to grid-disconnections. This method is advantageous over other methods of active islanding detection mainly due to the need for those methods to perturb the output to test for islanding conditions. The PLL stability method does not inject signal perturbations into the output of the converter, but instead is designed to be stable while grid-connected, but inherently unstable for grid-disconnections.
Resynchronization and reclosure to the grid is an important control aspect for microgrid systems that have the ability to operate in stand-alone, backup modes while disconnected from the grid. The resynchronization method proposed utilizes a dual PLL tracking system which minimizes voltage transients during the resynchronization process; while a logic-based reclosure algorithm ensures minimal magnitude, frequency, and phase mismatches between the grid and an isolated microgrid system to prevent inrush currents between the grid and stand-alone microgrid system.Ph. D.
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Fajemidupe, Olawale Taye. "Effect of particle size on sand deposition in single-phase and multi-phase pipelines." Thesis, Cranfield University, 2016. http://dspace.lib.cranfield.ac.uk/handle/1826/12325.
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Sand production in the life of oil and gas reservoirs is inevitable, as it is co- produced with oil and gas from the reservoirs. Sand deposition in petroleum pipelines poses considerable risk to the production of oil and gas. This study investigates the effect both of sand particle diameter and concentration on minimum transport conditions in single phase and multiphase horizontal pipelines through experimental methods. This study defines the minimum transport condition (MTC) for sand grains under stratified two-phase flow regimes, as the combined minimum gas and liquid velocities at which all sand particles have sufficient energy to keep them moving in the liquid phase along the pipe. In this study, careful analyses based on experimental observations were made producing several conclusions. Based on the analysis, it was found that sand of different particle diameters and concentrations exhibits similar behaviours in single phase flow and stratified two-phase flow in horizontal pipes. Furthermore, in stratified two-phase flow, sand particles were transported within the liquid film and never observed crossing into the gas phase or transported across the gas- liquid interface; however, an increase in gas velocity tends to cause an increase in liquid velocity which in turn increases the velocity of the sand particles in stratified two-phase flow. Studies carried out on the effect of particle diameter and concentration on MTCs in both single phase (water) and stratified two-phase flows (air-water) in horizontal pipes showed that MTC increases with increases in particle diameter for the same concentration and also increases as the concentration increases for the same particle diameter. Sand sensors were used in this study for the purpose of sand monitoring and detection in single phase (water) and stratified two-phase flow in horizontal pipes. The sensors were flush-mounted at the bottom of the pipe. These sensors are commonly used to measure the thickness of a film in multiphase flow but have not been used before for monitoring and detecting sand both in single phase and multiphase flows. In this work the sensors were applied in monitoring and detecting sand in single phase and multiphase flows; they were found to be capable of monitoring and detecting sand in a conducting liquid in both single phase and stratified two-phase flows. Measured pressure gradients for sand-water flow at MTC were compared with measured pressure gradients for sand-air-water flow for the same particle diameter and concentration; it was found that there was a difference between the two pressure gradients. The pressure gradient of sand-water flow at MTC was higher than the pressure gradient of sand-air-water flow at MTC. For this reason, King et al.’s (2001) pressure gradient approach cannot be used to design wet gas pipelines. Modified concentration (v/v) correction correlation is proposed to predict sand transport at MTC in air-water. The correlation accounts for low concentration of sand (5.39E-05 to 4.90E-04v/v) in air-water flow. The proposed correlation predicted fairly when compared with the experimental results at MTC.
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Bodnar, Nathan. "Phase-locking Stability of a Quasi-single-cycle Pulse." Master's thesis, University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5606.
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There is increasing interest in the generation of very short laser pulses, even down to attosecond (10-18 s) durations. Laser systems with femtosecond pulse durations are needed for these applications. For many of these applications, positioning of the maximum electric field within the pulse envelope can affect the outcome. The peak of the electric field relative to the peak of the pulse is called the Carrier Envelope Phase (CEP). Controlling the position of the electric field becomes more important when pulse duration approaches single-cycle. This thesis focuses on the stabilization of a quasi-single-cycle laser facility. Improvements to this already-established laser facility, HERACLES (High Energy, Repetition rate Adjustable, Carrier-Locked-to-Envelope System) described in this thesis include a stabilized pump line and the improvement in CEP stabilization electronics. HERACLES is built upon an Optical Parametric Chirped Pulse Amplification (OPCPA) architecture. This architecture uses Optical Parametric Amplification (OPA) as the gain material to increase the output energy of the system. OPA relies on a nonlinear process to generate high gain (106) with ultra-wide bandwidth. Instabilities in the OPA driving pump energy can create dynamically fluctuations in the final OPCPA output energy. To reduce these fluctuations two key upgrades were implemented on the pump beam. Both were major improvements in the stability. Firstly, an improved regenerative amplifier design reduced beam pointing fluctuations. Secondly, the addition of a pump monitoring system with feedback-control eliminated long-term power drifts. Both enhanced the OPA pulse-to-pulse and long-term stability. To improve the stability in measuring CEP drifts, modification of the feedback electronics was needed. The modification consisted of integrating noise reduction electronics. This novel noise reducer uses a similar process to a super-heterodyne receiver. The noise reducer resulted in 60 dB reduction of out-of-band noise. This led to increased signal quality with cleaner amplification of weaker signals. The enhanced signal quality led to more reliable long-term locking. The synthetically increased signal-to-noise ratio allows locking of the CEP frequency below the typically requirements. This integration allows relaxed constraints on the laser systems. The optics and electronics of a high-power, quasi-single cycle laser facility were improved. This thesis included the stabilization of the pump line and the stabilization of the CEP. This work allows for new long-duration experiments.M.S.
Masters
Optics and Photonics
Optics and Photonics
Optics; International
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Krawczyk-Becker, Martin [Verfasser]. "Phase-Aware Single-Channel Speech Enhancement / Martin Krawczyk-Becker." München : Verlag Dr. Hut, 2016. http://d-nb.info/1122524986/34.
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MATTOS, MARCOS ANDRE DA FROTA. "CORONA EFFECTS NUMERICAL SIMULATION IN SINGLE PHASE TRANSMISSION LINES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1985. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=14021@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORLABORATÓRIO NACIONAL DE COMPUTAÇÃO CIENTÍFICA - CNPQ
Uma análise teórica, comparativa e de sensibilidade é feita com quatro modelos básicos para o efeito corona em linhas de transmissão monofásicas. A análise de ocorrência de choque em linhas de transmissão é também considerada na análise os modelos. Um algoritmo computacional é desenvolvido para estudo de transitórios eletromagnéticos em linhas de transmissão monofásicas. Por fim são analisados casos interessantes do ponto de vista da Engenharia Elétrica.
The corona effect on monophasic transmission lines was subjected to a theoretical comparative sensibility analysis. Four basic models were used. The analysis of shock occurrence in transmission lines was also considered in the analysis of the models. A computational algorithms was developed to study electromagnetic transients on monophasic transmission lines. Finally, interesting cases from the Electrical Engeneering standpoint were analysed.
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Shin, Taeho. "Photoinduced phase transitions studied by femtosecond single-shot spectroscopy." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/62103.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2010.Vita. Cataloged from PDF version of thesis.
Includes bibliographical references (p. 221-228).
Single-shot femtosecond spectroscopy has been developed and employed for the study of phase transitions of solid-state materials. Using two crossed echelons, a two dimensional spatial delay gradient was generated across a single probe pulse profile. This novel scheme enables us to monitor irreversible change in solids by acquiring many time-resolved data points with a single laser pulse. With the integration with a non-collinear optical parametric amplifier (NOPA) and a conventional pump-probe instrument, ultrafast dynamics of coherent lattice vibrations and photo-induced phase transitions were examined in two different systems. Ultrafast dynamics such as coherent lattice vibrations and bond softening were investigated for Bi thin films and bulk single crystals. Depending on the thickness, transient reflectivity was changed significantly. The variations are ascribed to different electronic structures possibly originating from quantum confinement. Bond softening exhibits a strong thickness dependence due to hot carrier dynamics as well as to the different electronic structures. At high pump fluences, no phonon oscillations were observed suggesting a phase transition to liquid or to a higher symmetry crystalline phase (reverse Peierls distortion). Together with thermal modeling, double pump measurements reveal nonthermal melting occurring in bulk and thin Bi films. A higher threshold fluence for nonthermal melting is observed in bulk bismuth as compared to thin films, suggesting ultrafast carrier dynamics such as ballistic transport. In addition to nonthermal effects, thermal effects such as inelastic electron-phonon scattering and nonradiative recombination play a crucial role in melting and cooling at later times after nonthermal melting takes place. A quasi one-dimensional platinum iodide complex showed strong oscillations in reflectivity which are attributed to oscillatory motions of wave packets on a selftrapped exciton (STE) potential surface., As optical excitation increased, electron transfer from Pt 2+ to an adjacent Pt4+ occurred over a wider range of lattice sites and weakened the oscillations. Above a certain pump fluence, oscillations disappeared completely indicating that the mixed valence, charge density wave state changed to monovalent, Mott-Hubbard phase. The reverse phase transition, i.e., from the MottHubbard phase to the charge density wave state began within 3 ps of the optical pump.
by Taeho Shin.
Ph.D.
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Knight, Andrew Michael. "Analysis of line-start single-phase permanent magnet motors." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624867.
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Prichard, Martin Edward. "SINGLE PHASE MULTILEVEL INVERTER FOR GRID-TIED PHOTOVOLTAIC SYSTEMS." UKnowledge, 2015. http://uknowledge.uky.edu/ece_etds/81.
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Multilevel inverters offer many well-known advantages for use in high-voltage and high-power applications, but they are also well suited for low-power applications. A single phase inverter is developed in this paper to deliver power from a residential-scale system of Photovoltaic panels to the utility grid. The single-stage inverter implements a novel control technique for the reversing voltage topology to produce a stepped output waveform. This approach increases the granularity of control over the PV systems, modularizing key components of the inverter and allowing the inverter to extract the maximum power from the systems. The adaptive controller minimizes harmonic distortion in its output and controls the level of reactive power injected to the grid. A computer model of the controller is designed and tested in the MATLAB program Simulink to assess the performance of the controller. To validate the results, the performance of the proposed inverter is compared to that of a comparable voltage-sourced inverter.
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Tabatabaei, Fatemeh, and Gunter M. Schütz. "Nonequilibrium field-induced phase separation in single-file diffusion." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194414.
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Using an analytically tractable lattice model for reaction-diffusion processes of hard-core particles we demonstrate that under nonequilibrium conditions phase coexistence may arise even if the system is effectively one-dimensional as e.g. in the channel system of some zeolites or in artificial optical lattices. In our model involving two species of particles a steady-state particle current is maintained by a density gradient between the channel boundaries and by the influence of an external driving force. This leads to the development of a fluctuating but always microscopically sharp interface between two domains of different densities which are fixed by the boundary chemical potentials. The internal structure of the interface becomes very simple for strong driving force. We calculate the drift velocity and diffusion coefficient of the interface in terms of the microscopic model parameters.
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Du, Plessis Elsa. "Modelling of single phase diffusive transport in porous environments." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4323.
Full textAbstract:
Thesis (MSc (Applied Mathematics))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Macroscopic diffusion through porous media is considered in systems where this process does not occur along with or induce bulk convective flow of the diffusing species. The diffusion coefficient present in the governing equations of suchmacroscopic diffusion is unique to a pair of species in a binary system. This coefficient may be determined experimentally, but such experimentation must be carried out for every different pair of species. Taking this into consideration, a deterministic pore-scale model is proposed to predict the effective diffusivity of homogeneous and unconsolidated porous media which ultimately depends solely on the porosity of the media. The approach taken is to model a porous medium as either a fibre bed or an array of granules through which the diffusive process is assumed to be homogenous and transversally isotropic. The fibre bed and granular modelsmay be viewed as two-dimensional and three-dimensional models respectively, and may also be combined to form a weighted average model which adjusts to differing diffusive behaviour at different porosities. The model is validated through comparison with published analytical and numerical models as well as experimental data available in the literature. A numerical program is implemented to generate further data for various arrangements of homogeneous, anisotropic and transversely isotropic porous media. The numerical results were validated against an analytical model from the literature which proved to be inapplicable to a specific case. The weighted average analytical model is proposed for this case, instead. The results of this study indicate that the weighted average analytical model is in good agreement with the numerical and experimental data and as such may be applied directly to a binary system of which the porosity is known in order to predict the effective diffusivity.
AFRIKAANSE OPSOMMING: Makroskopiese diffusieprosesse deur poreuse media word oorweeg in sisteme waar geen konveksie van die diffunderende stof plaasvind of geïnduseer word nie. Die wiskundige beskrywing van hierdie prossese bevat die sogenaamde diffusiekoëffisïent, ’n konstante wat uniek is tot ’n tweeledige sisteem. Dié konstante kan eksperimenteel bepaal word, maar as gevolg van die uniekhied daarvan tot verskillende sisteme moet dit vir elke tweeledige sisteem bepaal word. Op grond hiervan word ’n deterministiese model voorgestel om die effektiewe diffusiwiteit vir diffusie deur homogene en losstaande poreuse media te voorspel. Die model hang slegs af van die porositeit van die poreuse medium wat benader word as ’n veselbed of korrelstruktuur. Die diffusieproses deur dergelike strukture word beskou as homogeen en isotroop in die dwarsstroomrigting. Die veselbed- en korrelmodelle word beskou as twee- en driedimensionele modelle onderskeidelik en word gekombineer om ’n geweegde gemiddelde model te vorm wat dus by enige porositeit die verlangde porositeit gee. Die model is geverifieer deur vergelyking met analitiese- en numeriese modelle asook eksperimentele data vanuit die literatuur. ’n Numeriese program is gebruik om verdere resultate te verkry vir verskeie skikkings van homogene, anisotrope en dwarsverskuifde poreuse media. Die numeriese resultate is gekontroleer deur vergelyking met ’n analitiese model vanuit die literatuur. ’n Spesifieke geval is uitgewys waarvoor hierdie model nie toepasbaar is nie, maar waarvoor die voorgestelde geweegde gemiddelde model goeie resultate lewer. Die uitkomste dui aan dat die analitiese model goed ooreenstem met die numeriese en eksperimentele data en kan dus direk toegepas word om die effektiewe diffusiwiteit te verkry van ’n tweeledige sisteem waarvan die porositeit bekend is.
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Chen, Tsu-Kung, and 陳賜恭. "Analyses of Single-Phase Induction Generators and Single-Phase Induction Motors." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/4n85uz.
Full textAbstract:
碩士國立成功大學
電機工程學系碩博士班
90
This thesis investigates the important performance of a single-phase, 110/220-V, 4-pole, 1/3-hp induction machine under two different operation modes, i.e., a single-phase induction motor (SPIM) mode and an isolated single-phase self-excited induction generator (SPSEIG) mode. In SPIM mode, the FLUX2D simulated software, which is widely employed for analyzing flux, heat, and transient characteristics, and the d-q axis SPIM equivalent-circuit model are both utilized to simulate the characteristics of a SPIM. The experimental results are compared with the simulated results obtained from both FLUX2D and q-d axis model to validate the performance of the studied machine under different operating conditions. In SPSEIG mode, both eigenvalue and eigenvalue sensitivity techniques are employed to determine required minimum excitation capacitance. The steady-state equivalent-circuit of a SPSEIG is used to obtain the relationship between main-winding current and magnetizing reactance. The simulated results based on a d-q axis equivalent-circuit SPSEIG model are also compared with the experimental results under different operating conditions.
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Chen, Guan-Ying, and 陳冠穎. "A Novel Single-stage Single-phase AC to Three-phase AC Converter." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/7dv95n.
Full textAbstract:
碩士國立虎尾科技大學
電機工程研究所
100
This thesis proposes a novel single-stage single-phase AC to three-phase AC converter. Based on a zero vector technique, the proposed converter combines a single-phase full-bridge with three-phase full-bridge to form a single-stage circuit structure. The converter has unity power factor and sinusoidal input current in input side. Adjustable amplitude and frequency of three-phase current source are in output side. The proposed converter consists of eight power switches, one capacitor, one boost inductor and three output inductors. It’s worth mentioning that ten switches of the traditional converter can reduce to eight, and this can reduce cost and improve efficiency obviously. Besides, general solution of the switching duty ratio is obtained by using the state space averaging technique. Furthermore, employing the three-phase dead-band control can decrease the ratio of 1/3 times switching number. Consequently, this reduce the switching loss, and improves efficiency of the converter. In the control circuit, both VisSim simulation and DSP TMS320F2812 are employed to finish digital control for power factor correction of the input side and feedback control of the output side. Finally, some experiment results are presented to verify the feasibility of the proposed converter.
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Lu, Wei-Tso, and 盧唯佐. "Single-Phase/Three-Phase Power Conversion System." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/w6edtd.
Full textAbstract:
碩士崑山科技大學
電機工程研究所
96
In this thesis, a single-phase/three-phase power conversion system is developed. The single-phase/three-phase power conversion system is configured by a three-phase four-wire power converter, a zero-sequence transformer set and a filter capacitor. The single-phase/three-phase power conversion system is applied to the single-phase distribution power system to perform a three-phase power conditioner. The current-mode control is applied to control the three-phase four-wire power converter so as to generate a positive-sequence current and a zero-sequence current. The positive-sequence current is used to generate the high-quality three-phase voltage suppling to the load. The zero-sequency current is passed to the single-phase distribution power system through the zero-sequency transformer such that the input current of single-phase/three-phase power conversion system is sinusoidal and in phase with the voltage of single-phase distribution power system. Since the proposed single-phase/three-phase power conversion system is configured by only one power converter, it has the advantages of simplifying the power circuit and control circuit. For verifing the performance of the proposed single-phase/three-phase power conversion system, a DSP-based hardware prototype is established and test.
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Yao-hui, Wang, and 王耀輝. "Three-Phase/Single-Phase Power Conversion System." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/15613927553968646833.
Full textAbstract:
碩士崑山科技大學
電機工程研究所
95
In this thesis, a three-phase/single-phase power conversion system is developed. The three-phase/single-phase power conversion system is configured by a power converter, a zero-sequence transformer set and a filter capacitor. The three-phase/single-phase power conversion system can be applied to the three-phase distribution power system to perform a single-phase power conditioner. In this application, the three-phase/ single-phase power conversion system absorbs a real power from the three-phase distribution power system, and it will perform the functions of three-phase balance, low harmonic distortion and unity power factor in spite of single-phase load used. Moreover, the three-phase/single-phase power conversion will supply a single-phase voltage with high power quality for supplying power to the single-phase load. The three-phase/ single-phase power conversion system can also be applied to the small capacity wind power generation system for converting the unregulated three-phase power to a high quality single-phase power and being injected to the single-phase distribution power system. In this application, the three-phase/single-phase power conversion system can perform the functions of three-phase current balance, low harmonic distortion and unity power factor for operating the three-phase power generator smoothly, and a new maximum power point tracking method is developed to extract the maximum power of small-capacity wind power system. Additionally, the three-phase/single-phase power conversion system can also generate a current which is sinusoidal and in phase with the voltage to the single-phase distribution power system. Since the proposed three-phase/single-phase power conversion system contains only one power converter, it has the advantages of simplifying the power circuit and control circuit.
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Nesbitt, James William. "A novel single phase to three phase converter." 1990. http://catalog.hathitrust.org/api/volumes/oclc/23057889.html.
Full textAbstract:
Thesis (M.S.)--University of Wisconsin--Madison, 1990.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 67).
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Nien, Hung-Shou, and 粘紘壽. "Single-Phase Active Power Filters." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/16011375951715284478.
Full textAbstract:
博士國立中正大學
電機工程所
94
The objective of this dissertation is to develop single-phase two-wire (1f2W) inverter systems for achieving active power filtering. The proposed active power filters (APFs) can be used to filter harmonic currents, compensate reactive power, improve power factor, and par-tially deal with the reactive and harmonic power. They can take into account the nonlinear ef-fect of a filter inductor, and can be modualized into a parallel-APF system. In the dissertation, a voltage-source full-bridge inverter is adopted to serve as the power stage of the discussed APFs. In an APF, the system controller is its kernel. It is mainly used to determine current commands to achieve the desired features, and it is realized on a digital signal processor (DSP) chip. In general, an APF with a linear inductor has been widely de-veloped to filter harmonic currents. For reducing the volume and cost, an APF with nonlinear inductor consideration is proposed. To prevent output current from exceeding switch ratings, inverter current is properly controlled through a current estimator. A self-learning algorithm is also proposed to determine nonlinear inductance, which can increase the accuracy of the es-timated current. For effectively utilizing the maximum capacity of the inverter, the proposed APF can adjust its output current below its switch current ratings dynamically. An amplitude-clamping algorithm (ACA) and an amplitude-scaling algorithm (ASA) are proposed, which can be used to determine current commands without need of complicated calculation. Thus, in the pro-posed APF, partial active-power-filtering can be achieved to increase the filter utilization. For developing a high power system, a paralleled APF system with current sharing con-troller (CSC) and load-path control center (LPCC) is designed and implemented. In the sys-tem, each APF module is directly tied to the load, source and buses, and there is no commu-nication between modules. Through CSC and LPCC, the modules can share the total reactive and harmonic currents of the load according to their power ratings. With the proposed control scheme, power capacity of the system can be readily and flexibly expanded. Since there is no communication between modules, system expandability and flexibility will increase, and hot-swap feature can be readily achieved. Simulation and experimental results have verified the feasibility and performance of the proposed single APF module and parallel-APF system.
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Shields, Bradley J. "Single-Phase Turbulent Enthalpy Transport." 2014. https://scholarworks.umass.edu/masters_theses_2/113.
Full textAbstract:
Vapor generation is central to the flow dynamics within fuel injector nozzles. Because the degree of atomization affects engine emissions and spray characteristics, quantification of phase change within diesel fuel injectors is a topic of design interest. Within the nozzle, the large pressure gradient between the upstream and downstream plena induce large velocities, creating separation and further pressure drop at the inlet corner. When local pressure in the throat drops below the fluid vapor pressure, phase change can occur with sufficient time. At the elevated temperatures present in diesel engines, this process can be dependent upon the degree of superheat, motivating the modeling of heat transfer from the wall.
By modeling cavitation and flash boiling phenomena as a departure from equilibrium conditions, the HRMFoam model accurately reproduces canonical adiabatic flows. An experimentally determined relaxation time controls the rate at which vapor is generated, and includes model constants tuned for water and a diesel fuel surrogate. The model is shown to perform well for several benchmark experimental cases, including the work of Reitz, Lichtarowicz, and Nurick.
With the implementation of the Farve-averaged energy equation, the present work examines and validates the transport of enthalpy through the fixed heat flux and fixed wall temperature boundary conditions. The pipe heat transfer experiments of Boelter and Allen are replicated using the kEpsilon, Realizable kEpsilon, and Spalart-Allmaras models. With proper turbulence model selection, Allen's heat transfer coefficient data is reproduced within 2.9%. Best-case bulk temperature rise prediction is within 0.05%. Boelter's bulk temperature rise is reproduced within 16.7%. Turbulent diffusivity is shown to determine radial enthalpy distribution.
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Bala, Sandeep. "Integration of single-phase microgrids." 2008. http://www.library.wisc.edu/databases/connect/dissertations.html.
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(5930573), Sriharsha Challa. "Numerical Methods for Single-phase and Two-phase Flows." Thesis, 2019.
Find full textAbstract:
Incompressible single-phase and two-phase flows are widely encountered in and underlie many engineering applications. In this thesis, we aim to develop efficient methods and algorithms for numerical simulations of these classes of problems. Specically, we present two schemes: (1) a modied consistent splitting scheme for incompressible single-phase flows with open/out flow boundaries; (2) a three-dimensional hybrid spectral element-Fourier spectral method for wall-bounded two-phase flows.
In the first part of this thesis, we present a modied consistent splitting type scheme together with a family of energy stable outflow boundary conditions for incompressible single-phase outflow simulations. The key distinction of this scheme lies
in the algorithmic reformulation of the viscous term, which enables the simulation of outflow problems on severely-truncated domains at moderate to high Reynolds numbers. In contrast, the standard consistent splitting scheme is observed to exhibit a numerical instability even at relatively low Reynolds numbers, and this numerical instability is in addition to the backflow instability commonly known to be associated with strong vortices or backflows at the outflow boundary. Extensive numerical experiments are presented for a range of Reynolds numbers to demonstrate the effectiveness and accuracy of the proposed algorithm for this class of flows.
In the second part of this thesis, we present a numerical algorithm within the phase-field framework for simulating three-dimensional (3D) incompressible two-phase flows in flow domains with one homogeneous direction. In this numerical method, we represent the flow variables using Fourier spectral expansions along the homogeneous direction and C0 spectral element expansions in the other directions. This is followed by using fast Fourier transforms so that the solution to the 3D problem is obtained by solving a set of decoupled equations about the Fourier modes for each flow variable. The computations for solving these decoupled equations are performed in parallel to effciently simulate the 3D two-phase
ows. Extensive numerical experiments are presented to demonstrate the performance and the capabilities of the scheme in simulating this class of flows.
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Shen, Sheng-Yong, and 沈聖詠. "A Novel Single Stage Single Phase Step up/down Inverter." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/55011432217236195734.
Full textAbstract:
碩士國立清華大學
電機工程學系
90
Inverters are widely used in various applications. However, traditional inverter configuration basically belongs to a step/down topology. In other words, the maximum peak voltage of the output AC voltage is limited to the input DC voltage. Hence, in case a higher output voltage is needed, it is necessary to either cascade one more stage of step/up CD converter or add an step/up transformer. This will, of course, result in larger size, lower efficiency and higher cost. In view of there, it is the main objection of this thesis to develop a single stage step up/down inverter without using an extra transformer. Basically, the contributions of this thesis may be summarized as follows. First, a novel single stage step up/down inverter without using a transformer is proposed to extend operation range of the output AC voltage. In fact, due to the four-quadrant operation capability of the proposed inverter, the new inverter can also be operated as an AC to DC converter. Second, mathematical model of the proposed inverter is also derived for feedback controller design and implementation. Third, in order to achieve a better performance, a closed loop controller is also presented to satisfy the desired specification. Finally, a hardware prototype of the proposed inverter is constructed to verify the feasibility of the proposed inverter.
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ZHENG, ZHEN-CHENG, and 鄭振成. "Single-phase AC passive filter design." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/29375859254576071789.
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HSIN-HUNG, CHEN, and 陳信宏. "True Single-phase Adiabatic Circuit Techniques." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/32088148628579102745.
Full textAbstract:
碩士國立臺灣大學
電機工程學研究所
90
This thesis reports a circuit technique to improve the performance of true single-phase adiabatic circuitry. In chapter 2, the principles of adiabatic and non-adiabatic charging/discharging is introduced. Several conventional adiabatic circuit families are reviewed and analyzed with discussion about their advantages and disadvantages. In chapter 3, the first ever true single-phase adiabatic circuit family is reviewed and analyzed. Improved true single-phase adiabatic circuit is proposed by utilizing bootstrapped switch technique. By HSPICE simulation, it is proven that the proposed circuit has better performance in noise margin and signal integrity than the original one.
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Wu, Chun-Wei, and 吳俊緯. "Study of Single-Phase Cascaded Inverters." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/67700580896255992422.
Full textAbstract:
博士雲林科技大學
工程科技研究所博士班
97
The objective of this dissertation is to develop single-phase cascaded inverters with three H-bridge inverter modules. The proposed cascade inverter features include: 1) the method of conducting angles; 2) the separate DC voltages discharge balance control and 3) predictive current control. The multilevel inverter synthesizing the output voltage with step pulses produces output voltages with less harmonic distortion. The conducting angles of switches in the conventional cascaded multilevel inverters are obtained by the use of Fourier series to minimize the harmonic distortion of output voltage. The traditional method is complex and difficult to implement on a single chip, especially when the input voltage sources is variation. This dissertation presents a method which calculates the switching angles by using the input voltage feed-forward of each H-bridge, in which the input voltage is fed into the controller and computed switching angles by the voltage areas of the divided reference voltage according to the output voltage levels of the inverter. Finally, the switching angles are transformed into the switching reference voltages. The proposed control can easily achieve dynamic control of the output voltage and reduce the distortion of inverter output voltage. The controller for the cascaded inverter can not be used for the inverter if a new H-bridge inverter module is added to the system for increasing the power capacity, or an H-bridge inverter module is disconnected from the system due to its failure. The system controller must be replaced or modified when the number of H-bridge inverter modules is changed. This dissertation proposes a flexible controller, which only requires the number of full bridge inverter modules, thus the proposed control can easily self-adjust to ensure balanced discharging of input dc voltage sources (if the dc voltage sources are batteries). A current control technique with predictive control method for cascaded inverters is proposed in this dissertation. Compared to the conventional predictive current controllers, the proposed control features: 1) Only the inductor current measurement is required, and it is able to achieve a cost-effective and less complex circuit (the output voltage and current measurements are required for a conventional controller); 2) The proposed variable sampling technique is designed to avoid the switching noise, thus a robust current controlled system can be achieved.
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Chu, Yung-Ching, and 朱勇青. "Toward Single Element Phase-change Memory." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/19395081395349936510.
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Lazar, James Frederick. "Analysis of single phase rectifier circuits." Thesis, 1997. https://thesis.library.caltech.edu/172/1/Lazar_jf_1997.pdf.
Full textAbstract:
The preponderant application of rectifier circuits is the powering of dc loads from the ac utility line. Ordinary rectifier circuits present a nonlinear load impedance to the utility line, thereby generating harmonic currents, and contributing to the harmonic current problem. There are many active and passive rectifier circuits offering reduced harmonic currents, and in this work a methodology is developed by which these circuits may be analyzed and compared.
Rectifier circuits can be classified as either active or passive. A passive rectifier circuit contains passive components (inductors, capacitors, saturable reactors, etc.), and passive switches (rectifier diodes) only. Active rectifier circuits use at least one controllable active switch (power transistor), in addition to passive switches and passive components. The performance characteristics of these circuits can be assessed with respect to a fictional device called the ideal rectifier. This assessment allows direct comparison of various approaches, passive or active, using the ideal rectifier as the common reference. Rectifier circuit performance may also be compared against specified requirements.
The next topic considered is the analysis of active rectifier circuits employing a pwm (pulse width modulation) converter as a means to control power flow within the rectifier circuit. The pwm converter is modeled using the pwm switch method. A large-signal nonlinear pwm switch model is used for modeling large-signal rectifier circuit behavior, and models are developed for operation in either the continuous or discontinuous conduction mode. Similarly, a small-signal model is developed for small-signal considerations. In addition, for pwm converters operating in the continuous conduction mode, the effect of lossy resistive elements inside the converter are accounted for in the pwm switch model, and this modeling technique is shown to give results identical to those obtained via the state-space averaging method.
The methods developed are then applied to the analysis of the boost rectifier operating in the discontinuous conduction mode. Three control schemes are compared, each offering a different compromise between circuit complexity and performance. Finally, a design example is given, and experimental results are provided.
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Chung, Bing-hsueh, and 鍾秉學. "Development of Single-Phase and Three-Phase Grid-Connected Power Converters." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/n3aapn.
Full textAbstract:
碩士國立臺灣科技大學
電機工程系
99
This thesis is concerned with the analysis and implementation of single-phase and three-phase dc-ac power converters for grid-connection. The utility angle is used to calculate the digital phase-locked loop in the single-phase and three-phase dc-ac power converters. The controllers, which use the d-q current control modes, are performed under stationary frame, thereby yielding current and power stably to utility. In the stand-alone system, the single-phase ac voltage regulator and voltage feed-forward compensation are introduced to improve response and reduce the steady-state error. Whereas three-phase stand-alone system uses the voltage control strategy to control the output voltage to follow the balanced command voltage. The overall system for performance evaluation includes wind generator and islanding detection. When utility power fails, the system switches to stand-alone mode and continues to supply power to ac load reliably. In this thesis, the mathematical models of single-phase and three-phase dc-ac power converter systems are built and simulated by Matlab/Simulink. Then, a high-performance digital signal processor, TMS320F28335, is used to control the system with the voltage and current feedbacks. The control of overall system is conducted by software to reduce circuit component and improve system reliability. A prototype of 1kW power conversion system is developed. Under single-phase and three-phase grid-connected operations, the output voltage is 110V, 60Hz. Besides, the experimental data show that the current total harmonic distortion measured is less than 5% with efficiency above 90%.
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Hedayati, Mohammad Hassan. "Integrated CM Filter for Single-Phase and Three-Phase PWM Rectifiers." Thesis, 2015. http://etd.iisc.ernet.in/2005/3947.
Full textAbstract:
The use of insulated-gate bipolar transistor (IGBT)-based power converters is increasing exponentially. This is due to high performance of these devices in terms of efficiency and switching speed. However, due to the switching action, high frequency electromagnetic interference (EMI) noises are generated. Design of a power converter with reduced EMI noise level is one of the primary objectives of this research.
The first part of the work focuses on designing common-mode (CM) filters, which can be integrated with differential-mode (DM) filters for three-phase pulse-width modulation (PWM) rectifier-based motor drives. This work explores the filter design based on the CM equivalent circuit of the drive system. Guidelines are provided for selection of the filter components. Different variants of the filter topology are evaluated to establish the effectiveness of the proposed topology. Analytical results based on Bode plot of the transfer functions are presented, which suggest effective EMI reduction. Experimental results based on EMI measurement on the grid side and CM current measurement on the motor side are presented. These results validate the effectiveness of the filter.
In the second part of the work, it is shown that inclusion of CM filters into DM filters results in resonance oscillations in the CM circuit. An active damping strategy is proposed to damp the oscillations in both line-to-line and line-to-ground ac voltages and currents. An approach based on pole placement by state feedback is used to actively damp both the DM and CM filter oscillations. Analytical expressions for state-feedback controller gains are derived for both continuous-and discrete-time models of the filter. Trade-off in selection of the active damping gain on the lower-order grid current harmonics is analysed using a weighted admittance function method.
In the third part of the work, single-phase grid-connected power converters are considered. An integrated CM filter with DM LCL filter is proposed. The work explores the suitability of PWM methods for single-phase and parallel single-phase grid-connected power converters. It is found that bipolar PWM and unipolar PWM with 180◦interleaving angle are suitable for single-phase and parallel single-phase power converters, respectively. The proposed configuration along with the PWM methods reduces the CM voltage, CM current, and EMI noise level effectively. It is also shown that the suggested circuit is insensitive to nonidealities of the power converter such as dead-time mismatch, mismatch in converter-side inductors, unequal turn on and turn off of the switches, and propagation delays.
In the fourth part of the work, the inter-phase inductor in parallel interleaved power converters is integrated with LCL filter boost inductor. Different variant designs are presented and compared with the proposed structure. It is shown that the proposed structure makes use of standard core geometries and consumes lesser core material as well as copper wire. Hence, it reduces the overall size and cost of the power converter.
In the present work, a 10kVA three-phase back-to-back connected with input LCL filter and output dv/dt filter, a 5kVA single-phase grid-connected power converter with LCL filter, and a 7.5kVA parallel single-phase grid-connected power converter with LCL filter are fabricated in the laboratory to evaluate and validate the proposed methods. The experimental results validate the proposed methods that result in significant EMI performance improvement of grid-connected power converters.
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Huang, Kuo-Fung, and 黃國芳. "Study of Three-Phase Input Single-Phase Output Uninterruptible Power System." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/72813291767985353156.
Full textAbstract:
碩士國立高雄應用科技大學
電機工程系
98
Three-phase four-wire distribution power systems have been widely applied in office buildings and manufacturing-office buildings to supply single-phase or three-phase loads. The uninterruptible power supply (UPS) is generally applied to supply the high quality power to the computer and precise equipment. In this thesis, three-phase input single-phase output UPS, composed of three-phase AC-DC power converter, battery set and single-phase DC-AC inverter, is addressed. Several circuit topologies and control methods, applied for the power factor correction, are analyzed, and the advanced two switches based power factor correction circuit with a new power factor correction method is proposed and implemented in the three-phase AC-DC power converter. The three-phase input currents of proposed three-phase AC-DC power converter are balanced, sinusoidal and in phase with the three-phase utility voltages so as to perform the unity power factor. The single-phase DC-AC inverter is configured by a diode-clamped three-level inverter to generate a high quality voltage to the load regardless the utility is normal or not. Finally, the computer simulation is made to verify the performance of proposed UPS. The simulation results show the performance of proposed three-phase input single-phase output UPS is as expected.
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Huang, Wun-Liang, and 黃文良. "Analysis of Adjustable-Speed Single-Phase Induction Motor Using Phase-Controller." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/39188097808808891603.
Full textAbstract:
碩士崑山科技大學
電子工程研究所
100
Small single-phase induction motor(SIPM) has been widely used in household appliances such as electric fans, air-conditioning units. The most common used speed control method is with mechanical switch combined with coil connections such as external transform or internal windings connection. This is based on cost considerations. Further control method uses phase control or variable voltage variable frequency (VVVF) control, respectively. The main issue of this paper is to explore the power components and efficiency of the phase-control speed process.
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Ke, Chun-Wei, and 柯雋煒. "Two−Phase and Two Single−Phase Buck Regulators with SVID Interface." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/5464ns.
Full textAbstract:
碩士淡江大學
電機工程學系碩士在職專班
106
A three-rail buck controller with Serial VID compliant IMVP8 interface is proposed in this thesis. The controller uses differential DCR current sensing and differential voltage sensing that provide accurately adaptive voltage positioning. The controller comprises a type III frequency compensator to provide high bandwidth transient response and zero current detection of synchronous rectifier to obtain higher efficiency at light load. In this thesis, the control chip NCP81226 is used to achieve the VCORE circuit control which can improve the reliability and expandability of the system. As a result of the experimental verification, the DC gain and output voltage droop range are properly designed, and the current scale of IOUT is adjusted that can effectively improve the problem of excessive DCR tolerance of the inductor which leads to offset of the VCORE load line and current reporting error for CPU. That can further causes problems of system stability due to system performance imbalance and temperature rise.
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Lee, Bong-Joo. "Single Phase Pump: Non-Mechanical Valvular Conduit." Thesis, 2011. http://hdl.handle.net/10012/6323.
Full textAbstract:
This thesis evaluates performance of a non-mechanical conduit valve that was designed for the purpose of this research. The motivation came from the need for a cooling system of portable computers (e.g. laptops and netbooks). As the technology of micro-processors in portable computers advances, they will generate more heat, requiring a more effective and efficient way to cool the system. Based on this fact, a new method of heat dissipation using a single-phase liquid (i.e. water) instead of air was examined. This potentially allowed 80 times more heat dissipation, which translates to better and faster computers for the near future.
In designing a single-phase-liquid micro-scale cooling system, various pump mechanisms and their functionalities were considered. It was concluded that a diaphragm pump design is the most effective candidate for this cooling system. The essential component when designing a diaphragm pump is a valve; however, the main issues in selecting a valve are its mechanics and required maintenance. Thus, the non-mechanical valvular conduit, which uses no moving mechanism, was studied through a combination of numerical/computational and experimental methods.
The non-mechanical valvular conduit is a micro-channel with a complex geometry; hence, this conduit uses the principle of pressure resistance in the channel flow such that the flow is uni-directional. Through the numerical study, the valvular conduit design’s geometric dimensions were optimized. Then numerical simulations of the pumping/oscillating sequence of the valvular conduit were conducted to examine the effectiveness of the valve when placed in use for a diaphragm pump. It was found that the non-mechanical valve was 38 % more effective in the favorable direction than the opposite direction. As for the necessary heat dissipation, this conduit design demonstrates a great potential to dissipate the thermal design power (TDP) of Intel Pentium D processor (i.e. 130 [W]). During the experiments, the non-mechanical valve confirmed the numerical results. The experimental results also demonstrated that the favorable direction flow produced 244 % less pressure resistance than the opposite direction flow.
It was concluded that the non-mechanical valvular conduit can be an effective application for diaphragm pumps in macro and micro-scale without any possibility of obstructing a mechanism.