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1
Sulkin, Daniel Paul. "Hysteresis in the Current Recession: Evidence and Consequences." Thesis, Boston College, 2012. http://hdl.handle.net/2345/2643.
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Thesis advisor: Robert Murphy<br>Hysteresis, in an economic context, is the idea that periods when the unemployment rate is greater than the natural rate have the effect of raising the underlying natural rate of unemployment (or, non-accelerating inflation rate of unemployment, NAIRU) and moving it to a new higher equilibrium state. The existence of hysteresis is still a matter of dispute in modern economics.This study examines the economic and employment situation from 1980 to the present and in particular since the beginning of the most recent recession in December 2007 and demonstrates that there exists evidence of hysteresis. It then aims to predict the economic consequences for the future and offers possible solutions to the problem.Given the scale of unemployment in the present economy and the importance of crafting an appropriate policy response, an examination of unemployment through the perspective of the hysteresis theory is a valuable approach that deserves further exploration<br>Thesis (BS) — Boston College, 2012<br>Submitted to: Boston College. Carroll School of Management<br>Discipline: Carroll School of Management Honors Program<br>Discipline: Economics
2
Liu, Yingying. "Multifrequency Averaging of Hysteresis-Current-Controlled DC-DC Converters." UKnowledge, 2015. http://uknowledge.uky.edu/ece_etds/67.
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Multifrequency averaging is one of the widely used modeling and simulation techniques today for the analysis and design of power electronic systems. This technique is capable of providing the average behavior as well as the ripple behavior of power electronic systems. Hysteresis current control has fast response and internal current stability through controlling switches to maintain the current within a given hysteresis band of a given current command. However the state space variables in a hysteresis controlled system cannot be directly approached by multifrequency averaging method because of time varing switching frequency. In this thesis, a method of applying multifrequency averaging to hysteresis current controlled dc-dc converters is proposed. A dc-dc converter model with the application of this method has been successfully developed and validated both in simulation and experiment.
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White, Terence H. "A three-phase hybrid dc-ac inverter system utilizing hysteresis control." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FWhite%5FTerence.pdf.
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Chen, Hanling. "AVERAGE-VALUE MODELING OF HYSTERESIS CURRENT CONTROL IN POWER ELECTRONICS." UKnowledge, 2015. http://uknowledge.uky.edu/ece_etds/78.
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Hysteresis current control has been widely used in power electronics with the advantages of fast dynamic response under parameter, line and load variation and ensured stability. However, a main disadvantage of hysteresis current control is the uncertain and varying switching frequency which makes it difficult to form an average-value model. The changing switching frequency and unspecified switching duty cycle make conventional average-value models based on PWM control difficult to apply directly to converters that are controlled by hysteresis current control.
In this work, a new method for average-value modeling of hysteresis current control in boost converters, three-phase inverters, and brushless dc motor drives is proposed. It incorporates a slew-rate limitation on the inductor current that occurs naturally in the circuit during large system transients. This new method is compared with existing methods in terms of simulation run time and rms error. The performance is evaluated based on a variety of scenarios, and the simulation results are compared with the results of detailed models. The simulation results show that the proposed model represents the detailed model well and is faster and more accurate than existing methods. The slew-rate limitation model of hysteresis current control accurately captures the salient detail of converter performance while maintaining the computational efficiency of average-value models. Validations in hardware are also presented.
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Wu, Zhengqiu. "Nonlinear modelling of three phase multi limb transformers." Thesis, London South Bank University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245156.
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RANJAN, SHILPA. "MINIMISATION OF TORQUE RIPPLE OF HYSTERESIS CURRENT CONTROLLED PMSM USING PI-RES CONTROLLER." Thesis, DELHI TECHNOLOGICAL UNIVERSITY, 2021. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18871.
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For the better dynamic performance of PMSM & minimum ripples in torque field
oriented control (FOC) is implemented. Some intricate methods are applied for
controlling & for the better performance of permanent magnet synchronous machine.
For highly performed motor drives flux estimation is always important. The rotor flux
estimation model is designed using high pass filter (HPF) to solve the problem caused
due to integrator applied in the flux estimation. Also phase locked loop (PLL) is
introduced in the model. It is known PMSM is used wherever smooth torque is
required. But because of some application of power electronics devices in the
modelling often reveals the cogging torque that led to ripple in torque. The key
drawback of PMSM is that it produces ripples in the induced torque, which are
undesirable in these high-performance applications. Torque ripples led to speed
oscillations, which cause PMSM servo output to worsen. The ripples in torque
produces mechanical vibrations and noise in the machine that decreases the life of
machine. The smoothness of torque is considered as the essential requirement for high
performance of permanent magnet synchronous motors. As a consequence, the
primary issue in PMSM's control problem is ripple minimization. Since many torque
ripples are caused by non-ideal back EMF in stators, a number of techniques for
reducing ripples caused by this phenomenon have been developed. PI controllers are
generally preferred but this got affected by the variations in parameters, load condition
and also on speed. To overcome this problem, a resonant controller is introduced in
accordance with PI for the minimization of ripples and to get the better performance.
The performance of control methods of both PI & PI-RES controller is compared.
7
Najafi, M., F. Hayati, and A. Rafati. "Effect of Current Frequency and Annealing on Magnetic Properties of [Co70Fe30]97Sn3 Nanowire Arrays." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35351.
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[Co70Fe30]97Sn3 alloy nanowire arrays have been fabricated by alternative current (ac) electrodeposition
of Co2+, Fe2+ and Sn2+ into anodic aluminum oxide (AAO) templates. The samples were deposited at current
frequency 50, 100, 200, 300, 400, 500, 800 and 1000 Hz, respectively. The structure and magnetic
properties of [Co70Fe30]97Sn3 nanowire arrays dependence on different current frequency were analyzed by
XRD and alternating gradient field magnetometer (AGFM). The X-ray diffraction patterns are shown an
amorphous structure of the[Co70Fe30]97Sn3 nanowires.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35351
8
Block-Schachter, David. "Hysteresis and urban rail : the effects of past urban rail on current residential and travel choices." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/73697.
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Thesis (Ph. D. in Transportation)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2012.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (p. 265-284).<br>Cities are endowed with and accumulate assets based on their unique histories, which in turn define the choice set of the present. These assets range from the natural-sheltered ports, fertile land--to the constructed--concrete and cement, institutions and people. This dissertation examines the effects of one of these assets, urban rail, on residential location and travel behavior, from the era of horsecars and streetcars to the present in Boston. It explores the hysteretical effects of past access to rail--the extent to which the urban system retains the impacts of rail even when it no longer exists. Current density and travel behavior are measurably influenced by past access to rail. The built environment and demographic patterns are found to be the strongest mechanism for these persistent effects. Past access to rail has shaped the city, and that shape has, in turn, affected travel behavior. For density and auto ownership there is an additional measurable effect of past access unexplained by the built environment or demographic patterns. This legacy is plausibly explained by cultural effects--mnemonics--due to personal history, behavioral norms, and zoning/politics. Past access to rail has a stronger effect on density than on auto ownership. The daily choice of modes is almost entirely conditioned on current circumstances. Because places shaped by rail retain its imprint, these findings imply that there is need to consider how policy decisions will influence the city's future choice set. The greatest benefits from the endowments of urban rail are likely where redevelopment costs are low and growth potential is high--particularly light industrial areas near strong central cities. Realizing these changes requires mechanisms that allow and encourage government and private entities to be patient with the long time frames for adaptation to rail infrastructure. One such step is requiring, rather than allowing, supportive zoning and other policies within the Federal Transit Administration's New Starts capital program--including such items as increased as-of-right density, reasonable limits on parking, car sharing, and graduated drivers licensing laws. This research strengthens prior findings that similar approaches can encourage sustainable cultural norms.<br>by David Block-Schachter.<br>Ph.D.in Transportation
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Lee, Heejae. "Analysis of Current-Voltage Hysteresis and Ageing Characteristics for CH3NH3PbI3-xClxBased Perovskite Thin Film Solar Cells." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX009/document.
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Les perovskites organiques-inorganiques en halogénures de plomb sont des matériaux très prometteurs pour la prochaine génération de cellules solaires avec des avantages intrinsèques tels que leur faible coût de fabrication (grande disponibilité des matériaux de base et leur mise en œuvre à basse température) et leur bon rendement de conversion photovoltaïque. Cependant, les cellules solaires pérovskites sont encore instables et montrent des effets d'hystérésis courant-tension délétères. Dans cette thèse, des résultats de l’analyse physique de couches minces de pérovskite à base de CH3NH3PbI3-xClx et de cellules solaires ont été présentés. Les caractéristiques de transport électrique et les processus de vieillissement ont été étudiés avec différentes approches.Dans une première étape, la synthèse du matériau pérovskite a été optimisée en contrôlant les conditions de dépôt des films en une seule étape telles que la vitesse de rotation (6000 rpm) de la tournette et la température de recuit des films (80 °C). Dans un second temps, des cellules solaires perovskites à base de CH3NH3PbI3-xClx ont été fabriquées en utilisant la structure planaire inversée et caractérisées optiquement et électriquement.Grace à l’utilisation de la spectroscopie optique à décharge luminescente (GDOES), un déplacement des ions halogénures a été observé expérimentalement et de façon directe sous l’application d’une tension électrique. Une longueur de diffusion ionique de 140 nm et un rapport de 65% d'ions mobiles ont été déduits. Il est montré que l'hystérésis courant-tension dans l'obscurité est fortement affectée par la migration des ions halogénures provoquant un écrantage substantiel du champ électrique appliqué. Nous avons donc trouvé sous obscurité un décalage de la tension à courant nul jusque 0,25 V et un courant de fuite jusque 0,1 mA / cm2 en fonction des conditions de mesure. Grâce aux courbes courant-tension en fonction de la température, nous avons déterminé la température de transition de la conductivité ions/électrons à 260K et analysé les résultats expérimentaux en utilisant l'équation de Nernst- Einstein donnant une énergie d'activation de 0.253 eV pour les ions mobiles.Enfin, le processus de vieillissement de la cellule solaire a été étudié avec des mesures optiques et électriques. Nous avons déduit que le processus de vieillissement apparaît d'abord à la surface des cristaux de pérovskite ainsi qu’aux joints de grains. Les mesures GDOES nous indiquent que les caractéristiques électriques des cellules pérovskites sont perdues par une corrosion progressive de l'électrode supérieure en argent causée par la diffusion des ions iodures<br>Organic-inorganic lead halide perovskites are very promising materials for the next generation of solar cells with intrinsic advantages such as a low-cost material due to the availability of source materials and low-temperature solution processing as well as a high power conversion efficiency of the sunlight. However, perovskite solar cells are still unstable and show deleterious current-voltage hysteresis effects. Inthis thesis, analyses of CH3NH3PbI3-xClx based perovskite thin films and solar cells are presented. The electrical transport characteristics and the ageing processes are investigated using different approaches.The synthesis of the halide perovskite materials is optimized in a first step by controlling the deposition conditions such as annealing temperature (80°C) and spinning rate (6000 rpm) in the one step-spin-casted process. CH3NH3PbI3-xClx based perovskite solar cells are then fabricated in the inverted planar structure and characterized optically and electrically in a second step.Direct experimental evidence of the motion of the halide ions under an applied voltage has been observed using glow discharge optical emission spectroscopy (GDOES). Ionic diffusion length of 140 nm and ratio of mobile iodide ions of 65 % have been deduced. It is shown that the current-voltage hysteresis in the dark is strongly affected by the halide migration which causes a substantial screening of the applied electric field. Thus we have found a shift of voltage at zero current (< 0.25 V) and a leakage current (< 0.1 mA/cm2) in the dark versus measurement condition. Through the current-voltage curves as a function of temperature we have identified the freezing temperature of the mobile iodides at 260K. Using the Nernst-Einstein equation we have deduced a value of 0.253 eV for the activation energy of the mobile ions.Finally, the ageing process of the solar cell has been investigated with optical and electrical measurements. We deduced that the ageing process appear at first at the perovskite grain surface and boundaries. The electrical characteristics are degraded through a deterioration of the silver top-electrode due to the diffusion of iodides toward the silver as shown by GDOES analysis
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Rezeq, Mohammed (Moh'd). "Investigation of magnetothermal and critical current hysteresis in polycrystals of low and high T(c) type II superconductors." Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6371.
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The model of Clem and Hao and others is extended to account for the enhancement of the Meissner effect observed in single crystals of hysteretic type II superconductors upon thermal cycling below Tc in static applied magnetic fields. Predictions are made about the features of the final closed thermal hysteretis loop achievable by extensive cycling and their dependence on the temperature limits T1 and T2 < Tc chosen for the cycles. A large variety of observations, by several workers, of a narrow peak of enhanced Meissner effect near Tc in polycrystalline type II superconductors upon slow warming in static applied fields after fast field cooling, are qualitatively and quantitatively accounted for by a model where we introduced the scheme developed above for single crystals into a weak-linked intergranular network (matrix). This "two tier" framework is then extended to describe the enhancement of the Meissner effect observed by Hyun by thermal cycling of weak-linked Nb3Sn below Tc in a static field. A simple framework is presented which quantitatively develops the proposal of Evetts and Glowacki that the superposition of the applied field H a and the return field, Hr of the magnetized grains, is the cause of the hysteretic behaviour of Ic in weak-linked high T c superconductors and the occurrence of a peak in Ic versus Ha descending and reascending, after an excursion to various values, denoted Hcycle, or after field cooling in different H cool. Observations by several workers on the dependence, of the position of four categories of peaks of Ic, on Hcycle and Hcool are reproduced by this model and yield estimates of the "compression" factor C in the linear dipole approximation, H r = C Mg. We also show that, ratios of the measured plateau values for the position of these peaks, lead to an estimate for C which is independent of H·g, the penetration field into the grains, and of the model chosen to calculate the dependence of the magnetization of the grains, Mg, on Ha. Instead of the artificial pseudo-Josephson - junction expression generally used by other workers in the analysis of Ic hysteresis phenomena, we develop a family of formulae based on the critical state concept applied to idealized planar geometry. Exploiting an especially simple case from this family of formulae we reproduce a panoply of experimental curves of Ic versus Ha displayed in the literature and exhibiting a variety, of features. Analysis of the extensive data of List et al reveals that our approach leads to results in accord with observations whereas the Josephson junction format does not. (Abstract shortened by UMI.)
11
Baktiono, Surya. "A Study of Field-Oriented Control of a Permanent Magnet Synchronous Generator and Hysteresis Current Control for Wind Turbine Application." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1338314559.
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Moura, Walterley Araujo. "Determinação da polarização ferroelétrica do PVDF estirado biaxialmente utilizando a técnica de corrente constante." Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-19052009-102253/.
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Foi desenvolvido um novo método para a determinação da polarização ferroelétrica de polímeros ferroelétricos, em particular do PVDF estirado biaxialmente. A técnica consiste em manter constante a corrente através da amostra e medir a evolução da tensão (V versus t) entre os eletrodos da mesma. As medidas foram realizadas em ambiente com atmosfera de ar superseco o que permite desprezar a condução elétrica das amostras, simplificando sobremaneira as equações do problema. Considera-se a existência de dois tipos de polarização: a ferroelétrica, com tempo de chavamento desprezível, e uma polarização elétrica foram realizados em duas situações distintas: com chaveamento e sem chaveamento ferroelétrico. O procedimento permite avaliar a dependência da polarização ferroelétrica com o campo, determinada a partir da equação geral da corrente. Para se descrever a resposta da polarização elétrica dependente do tempo, usa-se o princípio da superposição e assume-se que ela está em fase com o campo elétrico aplicado (processo lento). Será mostrado que é possível determinar a polarização ferroelétrica do polímero PVDF estirado biaxialmente sem a necessidade de determinar a formas funcionais da polarização dependente do tempo e de se conhecer o valor da capacitância da amostra.<br>In this work a novel method was developed for the determination of the ferroelectric polarization of ferroelectric polymers, in particular of biaxially stretched PVDF. The technique consists of maintaining constant the current through the sample and to measure the evolution of the bias voltage (V versus t) on the electrodes. Measurements were performed in super-dry air, which allows one to neglect the electric surface and volumetric conduction of the samples, simplifying the equations of the problem. It is considered the existence of two polarization types: the ferroelectric, with a very short switching time, and a another polarization dependent of the time. The processes for studying the electric polarization were accomplished in two different situations: with switching and without ferroelectric switching. The procedure allows evaluating the dependence of the ferroelectric polarization on the electric field, determined starting from the general equation of the current. To describe the time dependent polarization it is used the principle of superposition and the polarization value assumed to be in phase with the applied electric field (slow process). It will be shown that it is possible to determine the ferroelectric polarization of the material without the need of the functional form of the polarization and the value of the capacitance of the sample.
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Ozkaya, Hasan. "Parallel Active Filter Design, Control, And Implementation." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608438/index.pdf.
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The parallel active filter (PAF) is the modern solution for harmonic current
mitigation and reactive power compensation of nonlinear loads. This thesis is
dedicated to detailed analysis, design, control, and implementation of a PAF for a 3-
phase 3-wire rectifier load. Specifically, the current regulator and switching ripple
filter (SRF) are thoroughly investigated. A novel discrete time hysteresis current
regulator with multi-rate current sampling and flexible PWM output, DHCR3, is
proposed. DHCR3 exhibits a high bandwidth while limiting the maximum switching
frequency for thermal stability and its implementation is simple. In addition to the
development of DHCR3, in the thesis state of the art current regulation methods are
considered and thoroughly compared with DHCR3. Since the current regulator type
determines the SRF topology choice, various SRF topologies are considered and a
thorough design study is conducted and SRF topology selection and parameter
determination methods are presented via numerical examples. Through a PAF
designed for a 10kW diode/thyristor rectifier load, the superior performance of
DHCR3 is verified through simulations and experiments and via comparison to other
current regulators. The sufficient switching ripple attenuation of the SRF structures
for the designed PAF system and the overall performance of the designed and built
PAF system are demonstrated via detailed computer simulations and laboratory
experiments. This thesis aids the PAF current regulator and SRF selection, design,
and implementation.
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Lengvinas, Danius. "Elektros energijos apskaitos prietaisų charakteristikų tyrimas." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20100618_135329-87271.
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Šio darbo tyrimo tikslas – ištirti elektros energijos apskaitos prietaisų, indukcinių ir elektroninių, charakteristikas. Buvo atlikta informacijos šaltinių analizė apie indukcinių ir elektroninių elektros energijos skaitiklių ir srovės matavimo transformatorių parametrus, apsprendžiančius jų charakteristikas. Remiantis informacijos šaltinių apibendrinimu suformuota hipotezė: ne visos elektroninių elektros energijos prietaisų charakteristikos geresnės už indukcinių elektros energijos apskaitos prietaisų charakteristikas. Suformuoti tyrimo uždaviniai: ištirti elektroninių ir indukcinių elektros energijos prietaisų paklaidų priklausomybes nuo apkrovos srovės, galios koeficiento, eksploatacijos laiko, pasvyros kampo ir srovės matavimo transformatorių srovinės paklaidas. Padarytos išvados, nurodomas naudotos literatūros sąrašas.<br>The aim of this paper is to investigate the electricity metering devices, i.e. inductive and electronic, characteristics. It was made the analysis of the sources about the inductive and electricity meters and current transformers for measuring the parameters that define their characteristics. According to sources of information was formed the hypothesis: not all electronic power devices characteristics are better than inductive energy metering devices characteristics. The study objectives are to investigate experimentally the electronic and inductive power devices values of the load current, power factor, operating time, against an adverse list angle and current measuring transformer errors stream. Findings are discussed; the list of references is presented.
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Ingram, David. "An Evaluation of Harmonic Isolation Techniques for Three Phase Active Filtering." Thesis, University of Canterbury. Electrical and Computer Engineering, 1998. http://hdl.handle.net/10092/1260.
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Recent advances in power electronics have lead to the wide spread adoption of advanced power supplies and energy efficient devices. This has lead to increased levels of harmonic currents in power systems, degrading the performance of electrical machinery and interfering with telecommunication services. Active filters provide a solution to these problems by compensating for the distorted currents drawn by non-linear loads. Optimal methods for controlling these active filters have been determined by computer simulation and experimental implementation. Methods used for isolating the harmonic content of an unbalanced three phase load current were compared by computer simulations. A technique based on the Fast Fourier Transform (FFT) was developed as part of this work and shown to perform favourably. Notch Filtering, Sinusoidal Subtraction, Instantaneous Reactive Power Theory, Synchronous Reference Frame and Fast Fourier Transform methods were simulated. The methods shown to be suitable for compensation of three phase unbalanced loads were implemented in a Digital Signal Processor to evaluate true performance. These methods were Notch Filtering, Sinusoidal Subtraction, Fast Fourier Transform, and a High Pass Filter based method. A completely digital hysteresis current controller for a three phase active filter inverter has been developed and implemented with a Field Programmable Gate Array. This controller interfaces directly to a digital signal processor and is resistant to electromagnetic interference. Results from the experimental hardware verified that the active filter model used for simulation is accurate, and may be used for further development of harmonic isolation methods. A technique using notch filtering gives the best performance for steady loads, with the FFT based technique giving the most flexible operation for a range of load current characteristics. Novel use of the FFT based harmonic isolation technique allows selective cancellation of individual harmonics, with particular application to multiple shunt filters connected in parallel.
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Mousavi, Seyedali. "Electromagnetic Modelling of Power Transformers for Study and Mitigation of Effects of GICs." Doctoral thesis, KTH, Elektroteknisk teori och konstruktion, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-159747.
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Geomagnetic disturbances that result from solar activities can affect technological systems such as power networks. They may cause DC currents in power networks and saturation of the core in power transformers that leads to destruction in the transformer performance. This phenomena result in unwanted influences on power transformers and the power system. Very asymmetric magnetization current, increasing losses and creation of hot spots in the core, in the windings, and the metallic structural parts are adverse effects that occur in transformers. Also, increasing demand of reactive power and malfunction of protective relays menaces the power network stability. Damages in large power transformers and blackouts in networks have occurred due to this phenomenon. Hence, studies regarding this subject have taken the attention of researchers during the last decades. However, a gap of a comprehensive analysis still remains. Thus, the main aim of this project is to reach to a deep understanding of the phenomena and to come up with a solution for a decrease of the undesired effects of GIC. Achieving this goal requires an improvement of the electromagnetic models of transformers which include a hysteresis model, numerical techniques, and transient analysis. In this project, a new algorithm for digital measurement of the magnetic materials is developed and implemented. It enhances the abilities of accurate measurements and an improved hysteresis model has been worked out. Also, a novel differential scalar hysteresis model is suggested that easily can be implemented in numerical methods. Two and three dimensional finite element models of various core types of power transformers are created to study the effect of DC magnetization on transformers. In order to enhance the numerical tools for analysis of low frequency transients related to power transformers and the network, a novel topological based time step transformer model has been outlined. The model can employ a detailed magnetic circuit and consider nonlinearity, hysteresis and eddy current effects of power transformers. Furthermore, the proposed model can be used in the design process of transformers and even extend other application such as analysis of electrical machines. The numerical and experimental studies in this project lead to understanding the mechanism that a geomantic disturbance affects power transformers and networks. The revealed results conclude with proposals for mitigation strategies against these phenomena.<br><p>QC 20150210</p>
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Long, Fei. "Three-Dimensional Motion Control and Dynamic Force Sensing of a Magnetically Propelled Micro Particle Using a Hexapole Magnetic Actuator." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1452093964.
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Liu, Guangyuan. "Advanced Controllers of Power Electronic Converters in DC Microgrids." Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3422330.
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To cope with the pressure of climate change and depletion of fossil fuels, distributed power generation based on sustainable and green resources, such as photovoltaic and wind, have been exploited over the past decades. High penetration of renewable energy sources challenges the normal operation of traditional power grids, due to their characteristics of intermittence and uncertainty. To address this issue, an effective way is to aggregate distributed generators, energy storage systems, and customer loads together, as a single entity, that is, the so-called microgrids. Every microgrid is a fully dispatchable unit for grid operators, relieving the strains brought by renewable energy sources. Also, microgrids are able to provide reliable power for customer loads by supporting autonomous operation. Distributed energy resources are linked to microgrids by means of power electronic converters. As most of resources and future appliances are DC in nature, DC microgrids are more appealing than their AC counterparts. They can potentially achieve higher energy conversion efficiency and lower system costs, mainly by minimizing the number of DC-AC and AC-DC power conversion stages.
Droop control is a common decentralized solution to implement primary level control. With the droop control method, DC bus voltage is employed to convey the loading condition of DC microgrids, and load power can be automatically allocated among parallel resource converters. This dissertation focuses on performance improvement of droop-controlled converters, mainly in the following three aspects: i) reduction of DC bus capacitance while maintaining tight DC bus voltage regulation; ii) suppression of second-order harmonic current flowing into distributed energy resources; iii) smooth transfer from power flow control to droop control, allowing DC microgrids to seamlessly disconnect from upstream grids.
The first aspect: one of the constrains to reduce DC bus capacitance is the voltage surges and sags during load changes. From this point of view, resistive output impedance is a better design option than non-resistive output impedance for resource converters. This is because, given a certain output voltage tolerance band, resistive output impedance allows larger voltage dynamic variations, so that smaller output capacitance can be used. A systematical design approach, including the selection criteria of output capacitance and the design of droop coefficient, is proposed, covering both non-isolated (buck, boost, etc.) and isolated (dual active bridge) DC-DC converters. Following this design method, resistive output impedance can be effectively obtained. On the other hand, hysteresis control is another way to further reduce output capacitance, since it features faster dynamic response than classical PID control. Herein, hysteresis controller is implemented on digital signal processors instead of field programmable gate arrays. The implementation details, including the generation of driving signals for power switches and the effect of non-negligible computation time, are presented.
The second aspect: second-order harmonic power is an unavoidable issue in DC microgrids with single-phase inverters/rectifiers. Since droop-controlled converters usually show low output impedance at twice the line frequency, second-order harmonic power can flow into resource sides of converters. In some application like fuel cells, such harmonic current ripples can shorten device lifetime. To prevent the diffusion of second-order harmonic power, this dissertation studies the adoption of notch filter and resonant regulator in control loops. Although these two methods could mitigate second-order harmonic current, they deteriorate the stability performance of converters. In such a case, modified notch filter and modified resonant regulator are proposed to overcome the shortcoming of the traditional schemes. A comparative study is carried out to highlight the advantages of the proposed filter and regulator.
The third aspect: there are two limitations of the traditional droop control: one limitation is that the output power of droop-controlled converters is determined by load condition, and the other one is that the power sharing performance of droop control degrades with the presence of interconnecting cable impedance. To enhance the power flexibility and accuracy, a power-based droop controller, which unifies power flow control and droop control, is proposed for resource converters. When grid-interfacing converters impose the DC bus voltage, resource converters could operate with power flow control. When grid-interfacing converters fail, resource converters could work with droop control to stabilize the system. Importantly, the switch from power flow control to droop control can be automatically accomplished without communication or detection schemes. The operation principle, the design criteria, and the power sharing performance of the proposed controller are analyzed comprehensively.
All of the above-mentioned proposals are verified by relevant experimental results performing on different laboratory-scale DC microgrid prototypes.
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Gabi, Yasmine. "Modélisation FEM du système de contrôle non destructif 3MA en ligne de production des aciers dual phase." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00749118.
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Les métallurgistes d'ArcelorMittal développent actuellement une nouvelle génération d'aciers " flat carbon" dédiés principalement au domaine automobile (aciers Dual- Phase ou DP). Afin d'augmenter la performance des aciers au carbone, ArcelorMittal développe une stratégie de production intelligente basée sur un contrôle non destructif en ligne de production en utilisant le capteur 3MA (Multi-Parameter Micro-Magnetic Microstructure and Stress Analyzis). Ce système a été développé par l'Institut Fraunhôfer IZFP ; il est dédié à divers domaines d'applications de contrôle non destructifs des aciers en ligne. L'objectif principal de cette recherche est de simuler le comportement magnétique du dispositif industriel 3MA via la méthode des éléments finis. La modélisation du système (dispositif CND et échantillon) présente des difficultés au niveau du maillage et du temps de calcul surtout avec la mise en œuvre du modèle d'hystérésis. En effet, le système présente une géométrie multi échelles spatiale et temporelle. Afin de palier à ces problèmes, une stratégie de calcul a été développée et validée en 2D, en séparant calcul haute fréquence (HF) et basse fréquence (LF). Cette méthode permet d'effectuer des calculs en plusieurs fois et prend moins d'espace mémoire. Le modèle d'hystérésis de Jiles-Atherton a été choisi pour sa précision et a été implémenté dans le code FEM Flux afin de décrire le comportement magnétique du matériau. Les résultats obtenus sont en accord avec les données expérimentales.
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Rutkovskiy, Yaroslav. "A Novel Control Method for Grid Side Inverters Under Generalized Unbalanced Operating Conditions." Cleveland State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=csu1610646102417883.
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Zare, Firuz. "Multilevel converter structure and control." Thesis, Queensland University of Technology, 2001. https://eprints.qut.edu.au/36142/7/36142_Digitsed%20Thesis.pdf.
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In recent years, multilevel converters are becoming more popular and attractive than traditional converters in high voltage and high power applications. Multilevel converters are particularly suitable for harmonic reduction in high power applications where semiconductor devices are not able to operate at high switching frequencies or in high voltage applications where multilevel converters reduce the need to connect devices in series to achieve high switch voltage ratings. This thesis investigated two aspects of multilevel converters: structure and control.
The first part of this thesis focuses on inductance between a DC supply and inverter components in order to minimise loop inductance, which causes overvoltages and stored energy losses during switching. Three dimensional finite element simulations and experimental tests have been carried out for all sections to verify theoretical developments. The major contributions of this section of the thesis are as follows:
The use of a large area thin conductor sheet with a rectangular cross section separated by dielectric sheets (planar busbar) instead of circular cross section wires, contributes to a reduction of the stray inductance. A number of approximate equations exist for calculating the inductance of a rectangular conductor but an assumption was made that the current density was uniform throughout the conductors. This assumption is not valid for an inverter with a point injection of current. A mathematical analysis of a planar bus bar has been performed at low and high frequencies and the inductance and the resistance values between the two points of the planar busbar have been determined.
A new physical structure for a voltage source inverter with symmetrical planar bus bar structure called Reduced Layer Planar Bus bar, is proposed in this thesis based on the current point injection theory. This new type of planar busbar minimises the variation in stray inductance for different switching states. The reduced layer planar busbar is a new innovation in planar busbars for high power inverters with minimum separation between busbars, optimum stray inductance and improved thermal performances. This type of the planar busbar is suitable for high power inverters, where the voltage source is supported by several capacitors in parallel in order to provide a low ripple DC voltage during operation.
A two layer planar busbar with different materials has been analysed theoretically in order to determine the resistance of bus bars during switching. Increasing the resistance of the planar busbar can gain a damping ratio between stray inductance and capacitance and affects the performance of current loop during switching. The aim of this section is to increase the resistance of the planar bus bar at high frequencies (during switching) and without significantly increasing the planar busbar resistance at low frequency (50 Hz) using the skin effect. This contribution shows a novel structure of busbar suitable for high power applications where high resistance is required at switching times.
In multilevel converters there are different loop inductances between busbars and power switches associated with different switching states. The aim of this research is to consider all combinations of the switching states for each multilevel converter topology and identify the loop inductance for each switching state. Results show that the physical layout of the busbars is very important for minimisation of the loop inductance at each switch state. Novel symmetrical busbar structures are proposed for multilevel converters with diode-clamp and flying-capacitor topologies which minimise the worst case in stray inductance for different switching states. Overshoot voltages and thermal problems are considered for each topology to optimise the planar busbar structure.
In the second part of the thesis, closed loop current techniques have been investigated for single and three phase multilevel converters. The aims of this section are to investigate and propose suitable current controllers such as hysteresis and predictive techniques for multilevel converters with low harmonic distortion and switching losses. This section of the thesis can be classified into three parts as follows:
An optimum space vector modulation technique for a three-phase voltage source inverter based on a minimum-loss strategy is proposed. One of the degrees of freedom for optimisation of the space vector modulation is the selection of the zero vectors in the switching sequence. This new method improves switching transitions per cycle for a given level of distortion as the zero vector does not alternate between each sector. The harmonic spectrum and weighted total harmonic distortion for these strategies are compared and results show up to 7% weighted total harmonic distortion improvement over the previous minimum-loss strategy. The concept of SVM technique is a very convenient representation of a set of three-phase voltages or currents used for current control techniques.
A new hysteresis current control technique for a single-phase multilevel converter with flying-capacitor topology is developed. This technique is based on magnitude and time errors to optimise the level change of converter output voltage. This method also considers how to improve unbalanced voltages of capacitors using voltage vectors in order to minimise switching losses. Logic controls require handling a large number of switches and a Programmable Logic Device (PLD) is a natural implementation for state transition description. The simulation and experimental results describe and verify the current control technique for the converter.
A novel predictive current control technique is proposed for a three-phase multilevel converter, which controls the capacitors' voltage and load current with minimum current ripple and switching losses. The advantage of this contribution is that the technique can be applied to more voltage levels without significantly changing the control circuit. The three-phase five-level inverter with a pure inductive load has been implemented to track three-phase reference currents using analogue circuits and a programmable logic device.
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Magee, Warwick R. "Development of an electromagnetic actuator for active vibration control." Thesis, Queensland University of Technology, 1997.
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Jing, Linyuan. "HYSTERESIS IN REPOLARIZATION OF CARDIAC ACTION POTENTIALS: EFFECTS OF SPATIAL HETEROGENEITY AND SLOW REPOLARIZATION CURRENTS." UKnowledge, 2013. http://uknowledge.uky.edu/cbme_etds/11.
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Repolarization alternans, i.e. beat-to-beat variation of repolarization of action potential, is proposed as a predictor of life-threatening arrhythmias. Restitution relates repolarization duration with its previous relaxation time, i.e. diatstolic interval (DI), and is considered a dominant mechanism for alternans. Previously, we observed that different repolarization durations at the same DI during decelerating and accelerating pacing, i.e. restitution displays hysteresis, which is a measure of “cardiac memory”.
Objective of the current study was to investigate in the pig 1) the mechanism for a previously observed hysteresis type phenomenon, where alternans, once started at higher heart rate, persists even when heart rate decreases below its initiating rate, 2) regional differences in expression of hysteresis, i.e. memory in restitution in the heart, and 3) changes in restitution and memory during manipulation of an important repolarization current, the slow delayed rectifier, IKs.
Action potentials were recorded in pig ventricular tissues using microelectrodes. Regional differences were explored in endocardial and epicardial tissues from both ventricles. DIs were explicitly controlled in real time to separate restitution mechanism from non-restitution related effects. Stepwise protocols were used to explore the existence in hysteresis in alternans threshold, where DIs were held constant for each step and progressively decreased and then increased. Quantification of cardiac memory was achieved by sinusoidally changing DI protocols, which were used to investigate memory changes among myocytes from different regions of the heart and during IKs manipulation.
Results show that during stepwise protocol, hysteresis in alternans still existed, which indicates that restitution is not the only mechanism underlying the hysteresis. When comparing hysteresis obtained from sinusoidally oscillatory DIs among different regions, results show memory is expressed differently with endocardium expressing the most and epicardium the least memory. This provides important implications about the location where arrhythmia would initiate. Results also show that measures for hysteresis loops obtained by sinusoidal DI protocols decreased (increased) after enhancement (attenuation) of IKs, suggesting decreased (increased) hysteresis, i.e. memory in restitution. This effect needs to be considered during drug development.
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Thekkevalappil, Soniya Noormuhamed. "Hysteretic pulse width modulation with internally generated carrier for a boost dc-dc converter." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0013267.
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Ribbenfjärd, David. "A lumped element transformer model including core losses and winding impedances." Licentiate thesis, KTH, School of Electrical Engineering (EES), 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4307.
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<p>In order to design a power transformer it is important to understand its internal electromagnetic behaviour. That can be obtained by measurements on physical transformers, analytical expressions and computer simulations. One benefit with simulations is that the transformer can be studied before it is built physically and that the consequences of changing dimensions and parameters easily can be tested.</p><p>In this thesis a time-domain transformer model is presented. The model includes core losses as magnetic static hysteresis, eddy current and excess eddy current losses. Moreover, the model comprises winding losses including eddy currents, capacitive effects and leakage flux. The core and windings are first modelled separately and then connected together in a total transformer model. This results in a detailed transformer model.</p><p>One important result of the thesis is the possibility to simulate dynamic hysteresis including the eddy current shielding in the magnetic core material. This is achieved by using Cauer circuit combined with analytical expression for static and dynamic hysteresis. Thereby, all magnetic loss components in the material can be simulated accurately. This dynamic hysteresis model is verified through experiments showing very good agreement.</p>
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Almeida, Lucas Alves de. "Estudo de técnicas de controle de máquinas de relutância chaveada para aplicações em sistemas de acionamentos com velocidade variável." Universidade Federal de Juiz de Fora (UFJF), 2018. https://repositorio.ufjf.br/jspui/handle/ufjf/6837.
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Previous issue date: 2018-02-27<br>Sistemas eletromecânicos são de grande importância atualmente, e a procura por maior eficiência e desempenho aliados a um menor custo justificam a busca por alternativas tanto em topologia quanto no controle e acionamento de tais sistemas. A máquina de relutância chaveada é capaz de cumprir estes requisitos e tem despertado o interesse de pesquisadores e empresas nos últimos anos, emergindo como uma alternativa viável em diversas aplicações. Porém, esta máquina possui características singulares. Por conta de sua estrutura duplamente saliente, seu funcionamento correto depende da aplicação de pulsos de corrente por determinados intervalos de tempo, e na sequência correta, seus parâmetros são variáveis no tempo, apresentando um comportamento com características não-lineares. Tais particularidades fazem com que seja difícil controlar o torque destas máquinas, as quais possuem a tendência de apresentar altas oscilações durante a mudança da excitação de cada fase. Este trabalho tem por objetivo contribuir com o estudo da modelagem e do acionamento de uma máquina de relutância chaveada. É apresentada sua modelagem matemática e um modelo de simulação que leva em consideração as não linearidades existentes. Em seguida são apresentadas técnicas de controle de corrente que incluem um regulador de histerese, um controlador PI e um controlador por modos deslizantes. Também é utilizado um método capaz de determinar o momento em que cada fase deve ser acionada, baseado no ângulo do rotor, e uma técnica de variação dos ângulos de acionamento de maneira dinâmica, usados em conjunto com os controladores propostos. O trabalho também caracteriza e apresenta as funções de divisão de torque como uma maneira de reduzir drasticamente as oscilações de torque. São apresentadas as operações como motor e como gerador, bem como um exemplo de aplicação de modo a ilustrar ambos os modos de operação.<br>Electromechanical systems have a huge relevance nowadays, and seeking for improvements in efficiency and performance at the lowest cost make valid to identify topological and control alternatives of these systems. The switched reluctance machine is capable to fulfill such requirements and emerges as an interesting field of research. Academics and industrial works shows that it is a promising alternative in several applications. However, this machine presents unique characteristics, like the doubly salient structure, the necessity to apply phase currents in a sequence determined by the stator/rotor pole ratio, its time variantparameters,andthestrongnonlinearcharacteristics. Suchsingularitiesmaketorque control hard, as it tends to present high ripples and makes a lot of noise. This thesis aims to contribute on switched reluctance machine modeling and drive system. A mathematical model is presented, and also a simulation model that accounts for nonlinearities, making possible to simulate the machine accurately in a computational environment. A hysteresis regulator, a PI controller and a sliding mode controller are designed and simulated. An algorithm to determine when each phase should be excited based on rotor angle is used, and a technique to change such firing angles dynamically is developed that can be used along with current control methods presented. The work also defines and presents torque sharing functions as a way to greatly reduce torque ripple. Motor and generator operation are contemplated, and both modes are illustrated in an application example.
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Arbetter, Barry Steven. "DC-DC converter utilizing hysteretic current-mode control for low-voltage microprocessor systems with power management." Diss., Connect to online resource, 2006. 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:3219222.
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Boora, Arash Abbasalizadeh. "Flexible high-power multi DC-DC converters for train systems." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/33208/1/Arash_Boora_Thesis.pdf.
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This thesis reports on the investigations, simulations and analyses of novel power electronics topologies and control strategies. The research is financed by an Australian Research Council (ARC) Linkage (07-09) grant. Therefore, in addition to developing original research and contributing to the available knowledge of power electronics, it also contributes to the design of a DC-DC converter for specific application to the auxiliary power supply in electric trains. Specifically, in this regard, it contributes to the design of a 7.5 kW DC-DC converter for the industrial partner (Schaffler and Associates Ltd) who supported this project. As the thesis is formatted as a ‘thesis by publication’, the contents are organized around published papers. The research has resulted in eleven papers, including seven peer reviewed and published conference papers, one published journal paper, two journal papers accepted for publication and one submitted journal paper (provisionally accepted subject to few changes). In this research, several novel DC-DC converter topologies are introduced, analysed, and tested. The similarity of all of the topologies devised lies in their ‘current circulating’ switching state, which allows them to store some energy in the inductor, as extra inductor current. The stored energy may be applied to enhance the performance of the converter in the occurrence of load current or input voltage disturbances. In addition, when there is an alternating load current, the ability to store energy allows the converter to perform satisfactorily despite frequently and highly varying load current. In this research, the capability of current storage has been utilised to design topologies for specific applications, and the enhancement of the performance of the considered applications has been illustrated. The simplest DC-DC converter topology, which has a ‘current circulating’ switching state, is the Positive Buck-Boost (PBB) converter (also known as the non-inverting Buck-Boost converter). Usually, the topology of the PBB converter is operating as a Buck or a Boost converter in applications with widely varying input voltage or output reference voltage. For example, in electric railways (the application of our industrial partner), the overhead line voltage alternates from 1000VDC to 500VDC and the required regulated voltage is 600VDC. In the course of this research, our industrial partner (Schaffler and Associates Ltd) industrialized a PBB converter–the ‘Mudo converter’–operating at 7.5 kW. Programming the onboard DSP and testing the PBB converter in experimental and nominal power and voltage was part of this research program. In the earlier stages of this research, the advantages and drawbacks of utilization of the ‘current circulating’ switching state in the positive Buck-Boost converter were investigated. In brief, the advantages were found to be robustness against input voltage and current load disturbances, and the drawback was extra conduction and switching loss. Although the robustness against disturbances is desirable for many applications, the price of energy loss must be minimized to attract attention to the utilization of the PBB converter. In further stages of this research, two novel control strategies for different applications were devised to minimise the extra energy loss while the advantages of the positive Buck-Boost converter were fully utilized. The first strategy is Smart Load Controller (SLC) for applications with pre-knowledge or predictability of input voltage and/or load current disturbances. A convenient example of these applications is electric/hybrid cars where a master controller commands all changes in loads and voltage sources. Therefore, the master controller has a pre-knowledge of the load and input voltage disturbances so it can apply the SLC strategy to utilize robustness of the PBB converter. Another strategy aiming to minimise energy loss and maximise the robustness in the face of disturbance is developed to cover applications with unexpected disturbances. This strategy is named Dynamic Hysteresis Band (DHB), and is used to manipulate the hysteresis band height after occurrence of disturbance to reduce dynamics of the output voltage. When no disturbance has occurred, the PBB converter works with minimum inductor current and minimum energy loss. New topologies based on the PBB converter have been introduced to address input voltage disturbances for different onboard applications. The research shows that the performance of applications of symmetrical/asymmetrical multi-level diode-clamped inverters, DC-networks, and linear-assisted RF amplifiers may be enhanced by the utilization of topologies based on the PBB converter. Multi-level diode-clamped inverters have the problem of DC-link voltage balancing when the power factor of their load closes to unity. This research has shown that this problem may be solved with a suitable multi-output DC-DC converter supplying DClink capacitors. Furthermore, the multi-level diode-clamped inverters supplied with asymmetrical DC-link voltages may improve the quality of load voltage and reduce the level of Electromagnetic Interference (EMI). Mathematical analyses and experiments on supplying symmetrical and asymmetrical multi-level inverters by specifically designed multi-output DC-DC converters have been reported in two journal papers. Another application in which the system performance can be improved by utilization of the ‘current circulating’ switching state is linear-assisted RF amplifiers in communicational receivers. The concept of ‘linear-assisted’ is to divide the signal into two frequency domains: low frequency, which should be amplified by a switching circuit; and the high frequency domain, which should be amplified by a linear amplifier. The objective is to minimize the overall power loss. This research suggests using the current storage capacity of a PBB based converter to increase its bandwidth, and to increase the domain of the switching converter. The PBB converter addresses the industrial demand for a DC-DC converter for the application of auxiliary power supply of a typical electric train. However, after testing the industrial prototype of the PBB converter, there were some voltage and current spikes because of switching. To attenuate this problem without significantly increasing the switching loss, the idea of Active Gate Signalling (AGS) is presented. AGS suggests a smart gate driver that selectively controls the switching process to reduce voltage/current spikes, without unacceptable reduction in the efficiency of switching.
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Masoud, Khalid Hasan. "Circuits and controls for grid-connected inverters." Thesis, Queensland University of Technology, 2002.
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Krings, Andreas. "Iron Losses in Electrical Machines - Influence of Material Properties, Manufacturing Processes, and Inverter Operation." Doctoral thesis, KTH, Elektrisk energiomvandling, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-145243.
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As the major electricity consumer, electrical machines play a key role for global energy savings. Machine manufacturers put considerable efforts into the development of more efficient electrical machines for loss reduction and higher power density achievements. A consolidated knowledge of the occurring losses in electrical machines is a basic requirement for efficiency improvements. This thesis deals with iron losses in electrical machines. The major focus is on the influences of the stator core magnetic material due to the machine manufacturing process, temperature influences, and the impact of inverter operation. The first part of the thesis gives an overview of typical losses in electrical machines, with focus put on iron losses. Typical models for predicting iron losses in magnetic materials are presented in a comprehensive literature study. A broad comparison of magnetic materials and the introduction of a new material selection tool conclude this part. Next to the typically used silicon-iron lamination alloys for electrical machines, this thesis investigates also cobalt-iron and nickel-iron lamination sheets. These materials have superior magnetic properties in terms of saturation magnetization and hysteresis losses compared to silicon-iron alloys. The second and major part of the thesis introduces the developed measurement system of this project and presents experimental iron loss investigations. Influences due to machine manufacturing changes are studied, including punching, stacking and welding effects. Furthermore, the effect of pulse-width modulation schemes on the iron losses and machine performance is examined experimentally and with finite-element method simulations. For nickel-iron lamination sheets, a special focus is put on the temperature dependency, since the magnetic characteristics and iron losses change considerably with increasing temperature. Furthermore, thermal stress-relief processes (annealing) are examined for cobalt-iron and nickel-iron alloys by magnetic measurements and microscopic analysis. A thermal method for local iron loss measurements is presented in the last part of the thesis, together with experimental validation on an outer-rotor permanent magnet synchronous machine.<br><p>QC 20140516</p>
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Nami, Alireza. "A new multilevel converter configuration for high power and high quality applications." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/33216/1/Alireza_Nami_Thesis.pdf.
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The Queensland University of Technology (QUT) allows the presentation of theses for the Degree of Doctor of Philosophy in the format of published or submitted papers, where such papers have been published, accepted or submitted during the period of candidature. This thesis is composed of ten published /submitted papers and book chapters of which nine have been published and one is under review. This project is financially supported by an Australian Research Council (ARC) Discovery Grant with the aim of investigating multilevel topologies for high quality and high power applications, with specific emphasis on renewable energy systems. The rapid evolution of renewable energy within the last several years has resulted in the design of efficient power converters suitable for medium and high-power applications such as wind turbine and photovoltaic (PV) systems. Today, the industrial trend is moving away from heavy and bulky passive components to power converter systems that use more and more semiconductor elements controlled by powerful processor systems. However, it is hard to connect the traditional converters to the high and medium voltage grids, as a single power switch cannot stand at high voltage. For these reasons, a new family of multilevel inverters has appeared as a solution for working with higher voltage levels. Besides this important feature, multilevel converters have the capability to generate stepped waveforms. Consequently, in comparison with conventional two-level inverters, they present lower switching losses, lower voltage stress across loads, lower electromagnetic interference (EMI) and higher quality output waveforms. These properties enable the connection of renewable energy sources directly to the grid without using expensive, bulky, heavy line transformers. Additionally, they minimize the size of the passive filter and increase the durability of electrical devices. However, multilevel converters have only been utilised in very particular applications, mainly due to the structural limitations, high cost and complexity of the multilevel converter system and control. New developments in the fields of power semiconductor switches and processors will favor the multilevel converters for many other fields of application. The main application for the multilevel converter presented in this work is the front-end power converter in renewable energy systems. Diode-clamped and cascade converters are the most common type of multilevel converters widely used in different renewable energy system applications. However, some drawbacks – such as capacitor voltage imbalance, number of components, and complexity of the control system – still exist, and these are investigated in the framework of this thesis. Various simulations using software simulation tools are undertaken and are used to study different cases. The feasibility of the developments is underlined with a series of experimental results. This thesis is divided into two main sections. The first section focuses on solving the capacitor voltage imbalance for a wide range of applications, and on decreasing the complexity of the control strategy on the inverter side. The idea of using sharing switches at the output structure of the DC-DC front-end converters is proposed to balance the series DC link capacitors. A new family of multioutput DC-DC converters is proposed for renewable energy systems connected to the DC link voltage of diode-clamped converters. The main objective of this type of converter is the sharing of the total output voltage into several series voltage levels using sharing switches. This solves the problems associated with capacitor voltage imbalance in diode-clamped multilevel converters. These converters adjust the variable and unregulated DC voltage generated by renewable energy systems (such as PV) to the desirable series multiple voltage levels at the inverter DC side. A multi-output boost (MOB) converter, with one inductor and series output voltage, is presented. This converter is suitable for renewable energy systems based on diode-clamped converters because it boosts the low output voltage and provides the series capacitor at the output side. A simple control strategy using cross voltage control with internal current loop is presented to obtain the desired voltage levels at the output voltage. The proposed topology and control strategy are validated by simulation and hardware results. Using the idea of voltage sharing switches, the circuit structure of different topologies of multi-output DC-DC converters – or multi-output voltage sharing (MOVS) converters – have been proposed. In order to verify the feasibility of this topology and its application, steady state and dynamic analyses have been carried out. Simulation and experiments using the proposed control strategy have verified the mathematical analysis. The second part of this thesis addresses the second problem of multilevel converters: the need to improve their quality with minimum cost and complexity. This is related to utilising asymmetrical multilevel topologies instead of conventional multilevel converters; this can increase the quality of output waveforms with a minimum number of components. It also allows for a reduction in the cost and complexity of systems while maintaining the same output quality, or for an increase in the quality while maintaining the same cost and complexity. Therefore, the asymmetrical configuration for two common types of multilevel converters – diode-clamped and cascade converters – is investigated. Also, as well as addressing the maximisation of the output voltage resolution, some technical issues – such as adjacent switching vectors – should be taken into account in asymmetrical multilevel configurations to keep the total harmonic distortion (THD) and switching losses to a minimum. Thus, the asymmetrical diode-clamped converter is proposed. An appropriate asymmetrical DC link arrangement is presented for four-level diode-clamped converters by keeping adjacent switching vectors. In this way, five-level inverter performance is achieved for the same level of complexity of the four-level inverter. Dealing with the capacitor voltage imbalance problem in asymmetrical diodeclamped converters has inspired the proposal for two different DC-DC topologies with a suitable control strategy. A Triple-Output Boost (TOB) converter and a Boost 3-Output Voltage Sharing (Boost-3OVS) converter connected to the four-level diode-clamped converter are proposed to arrange the proposed asymmetrical DC link for the high modulation indices and unity power factor. Cascade converters have shown their abilities and strengths in medium and high power applications. Using asymmetrical H-bridge inverters, more voltage levels can be generated in output voltage with the same number of components as the symmetrical converters. The concept of cascading multilevel H-bridge cells is used to propose a fifteen-level cascade inverter using a four-level H-bridge symmetrical diode-clamped converter, cascaded with classical two-level Hbridge inverters. A DC voltage ratio of cells is presented to obtain maximum voltage levels on output voltage, with adjacent switching vectors between all possible voltage levels; this can minimize the switching losses. This structure can save five isolated DC sources and twelve switches in comparison to conventional cascade converters with series two-level H bridge inverters. To increase the quality in presented hybrid topology with minimum number of components, a new cascade inverter is verified by cascading an asymmetrical four-level H-bridge diode-clamped inverter. An inverter with nineteen-level performance was achieved. This synthesizes more voltage levels with lower voltage and current THD, rather than using a symmetrical diode-clamped inverter with the same configuration and equivalent number of power components. Two different predictive current control methods for the switching states selection are proposed to minimise either losses or THD of voltage in hybrid converters. High voltage spikes at switching time in experimental results and investigation of a diode-clamped inverter structure raised another problem associated with high-level high voltage multilevel converters. Power switching components with fast switching, combined with hard switched-converters, produce high di/dt during turn off time. Thus, stray inductance of interconnections becomes an important issue and raises overvoltage and EMI issues correlated to the number of components. Planar busbar is a good candidate to reduce interconnection inductance in high power inverters compared with cables. The effect of different transient current loops on busbar physical structure of the high-voltage highlevel diode-clamped converters is highlighted. Design considerations of proper planar busbar are also presented to optimise the overall design of diode-clamped converters.
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Faudot, Adrien. "Les choix de facturation du commerce international : état des lieux, déterminants, inertie de la monnaie." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAE011/document.
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Malgré une apparente concurrence entre les monnaies, le dollar américain est la monnaie adoptée par la majorité des participants aux échanges internationaux, exportateurs et importateurs. C’est ce que montre l’état des lieux statistique proposé dans cette thèse. Partant d’un tel constat, l’objectif de cette thèse est d’expliquer les choix de monnaies de facturation du commerce international. Différents déterminants ont été établis par la littérature académique pour expliquer les choix de monnaies de facturation. Trois approches, aux méthodologies sensiblement distinctes, y contribuent, et peuvent dès lors être confrontées : l’approche macroéconomique standard, l’approche institutionnaliste, et l’approche de l’économie politique internationale. Le principal résultat de cette thèse est de montrer que la compréhension du choix du dollar américain ne peut se contenter des déterminants mis en évidence par les approches instrumentales de la monnaie qui dominent la macroéconomie internationale, et dans lesquelles la monnaie est avant tout vue comme un outil de maximisation d’utilités individuelles : leurs apports sont utiles, mais insuffisants. En appliquant la lecture institutionnaliste aux échanges internationaux, la thèse introduit l’importance des rapports de confiance et d’adhésion des acteurs à l’égard de la monnaie et de l’ordre défendu par ses institutions régulatrices. Cette importance se vérifie dans l’histoire du XXe siècle, à la fois dans l’échec des monnaies concurrentes du dollar, et dans la persistance de la monnaie américaine elle-même<br>Despite the appearance of competition between currencies, the US dollar remains the invoicing currency among the actors of international trade. Such observation is derived from ample statistical evidence contained in this thesis. This observation represents the starting-point of a broader reflection on the rationale underlying the choice of an invoicing currency in international trade, which is the central question which this thesis aims to address. Various determinants have been closely examined by the academic literature to that end. Three approaches dealt with the subject, each with its distinct methodology, and can therefore be analyzed comparatively: the standard macroeconomic approach, the institutionalist approach, and the international political economy approach. The main result of this thesis is that preference for the US dollar cannot be explained exclusively by the instrumental approaches of money which usually prevail in international macroeconomics: their contributions are useful but inadequate as they envision money primarily as a tool for maximizing individual utilities. By applying the institutionalist reading to international exchanges, the thesis introduces the necessity of trust and ethical appeal that money inspires, and the centrality of the social order that its regulatory institutions pursue. This necessity was reasserted throughout the twentieth century, as competing currencies failed to challenge the supremacy of the dollar. It is also evidenced by the resilience of the American currency itself
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Carrander, Claes. "Magnetizing Currents in Power Transformers : Measurements, Simulations, and Diagnostic Methods." Doctoral thesis, KTH, Elektroteknisk teori och konstruktion, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-208422.
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This thesis demonstrates a method for transformer core diagnostics. The method uses the no-load current of the transformer as an indicator, and gives different characteristic signatures for different types of faults or defects. Using the no-load current for the diagnostic gives high sensitivity. The method is therefore able to detect defects that are too small to have an impact on the losses. In addition to different types of fault, the method can in some cases also distinguish between faults in different locations within the core. Both single-phase and three-phase transformers can be diagnosed using this method, and the measurements can be easily performed at any facility capable of measuring the no-load loss. There are, however, some phenomena that occur in large transformers, and in transformers with high rated voltages. Examples include capacitive resonance and magnetic remanence. This thesis proposes and demonstrates techniques for compensating for these phenomena. With these compensating techniques, the repeatability of the measurements is high. It is shown that units with the same core steel tend to have very similar no-load behavior. The diagnostics can then be performed either by comparing the transformer to another unit, or to simulations. The thesis presents one possible simulation method, and demonstrates the agreement with measurements. This topological simulation method includes both the electric circuit and an accurate model of the magnetic hysteresis. It is therefore also suitable for other, related, studies in addition to core diagnostics. Possible subjects include ferroresonance, inrush, DC magnetization of transformers, and transformer core optimization. The thesis also demonstrates that, for three-phase transformers, it is possible to compare the phases to each other. This technique makes it possible to diagnose a transformer even without a previous measurement to compare to, and without the data required to make a simulation.<br><p>QC 20170607</p>
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Curran, Mark James [Verfasser]. "The Hysteretic Limit of a Reaction-Diffusion System with a Small Parameter / Mark James Curran." Berlin : Freie Universität Berlin, 2019. http://d-nb.info/1183675798/34.
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Ribbenfjärd, David. "Electromagnetic transformer modelling including the ferromagnetic core." Doctoral thesis, KTH, Elektroteknisk teori och konstruktion, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-13080.
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In order to design a power transformer it is important to understand its internal electromagnetic behaviour. That can be obtained by measurements on physical transformers, analytical expressions and computer simulations. One benefit with simulations is that the transformer can be studied before it is built physically and that the consequences of changing dimensions and parameters easily can be assessed. In this thesis a time-domain transformer model is presented. The model includes core phenomena as magnetic static hysteresis, eddy current and excess losses. Moreover, the model comprises winding phenomena as eddy currents, capacitive effects and leakage flux. The core and windings are first modelled separately and then connected together in a composite transformer model. This results in a detailed transformer model. One important result of the thesis is the feasibility to simulate dynamic magnetization including the inhomogeneous field distribution due to eddy currents in the magnetic core material. This is achieved by using a Cauer circuit combined with models for static and dynamic magnetization. Thereby, all magnetic loss components in the material can be simulated accurately. This composite dynamic magnetization model is verified through experiments showing very good correspondence with measurements. Furthermore, the composite transformer model is verified through measurements. The model is shown to yield good correspondence with measurements in normal operation and non-normal operations like no-load, inrush current and DC-magnetization.<br>QC20100708
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Zorni, Chiara. "Contrôle non destructif par courants de Foucault de milieux ferromagnétiques : de l’expérience au modèle d’interaction." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112031/document.
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La problématique étudiée est le contrôle non destructif par courants de Foucault de matériaux ferromagnétiques à l’aide d’un capteur à magnétorésistance géante (GMR). Durant ces travaux deux aspects complémentaires ont été abordés : l’un concerne la mesure expérimentale pour essayer de quantifier et de s’affranchir du bruit de structure et du champ magnétique rémanent, l’autre le développement d’un modèle numérique d’interaction. En ce qui concerne la partie expérimentale plusieurs études avec un capteur GMR qui présente un intérêt particulier en raison de sa bonne sensibilité à basses fréquences, de sa dynamique et de la relative simplicité de mise en œuvre ont été conduites et ont permis d’identifier et quantifier les phénomènes d’artefacts spécifiques aux matériaux ferromagnétiques : le bruit de structure et le champ magnétique rémanent. Une solution basée sur une combinaison linéaire des données expérimentales obtenues à plusieurs fréquences est appliquée pour atténuer le bruit dû à la structure du matériau. Le champ magnétique rémanent a été analysé expérimentalement et un circuit d’asservissement permettant de fixer un point de polarisation dans la zone de fonctionnement linéaire de la GMR et ainsi d’atténuer les perturbations dues aux champs magnétiques rémanents est mis en place. En parallèle et dans l’optique de développer des outils de simulation permettant de mieux comprendre les phénomènes physiques et ainsi d’optimiser les procédés de contrôle, un modèle numérique d’interaction simulant le cas du contrôle d’une pièce plane ferromagnétique d’une ou plusieurs couches pouvant contenir un ou plusieurs défauts est développé. Il étend un modèle déjà existant dans un cas non-ferromagnétique déjà intégré dans la plateforme de simulation CIVA développé par le CEA-LIST et permettant la simulation du Contrôle Non Destructif par Courants de Foucault. Il est basé sur une méthode d’intégrales de volume (VIM) et l’utilisation des tenseurs ou dyades de Green. La solution est obtenue après la discrétisation du volume de calcul et l’application d’une variante de Galerkin de la Méthode des Moments (MoM). La réponse de la sonde est ensuite calculée en appliquant le théorème de réciprocité de Lorentz. Des collaborations avec deux laboratoires universitaires (le Laboratoire de Génie Électrique de Paris (LGEP) et l’Université de Cassino (Italie)) ont permis de comparer les résultats issus des trois différents modèles sur un cas de la littérature. Les résultats se sont révélés satisfaisants et plusieurs études de convergence ont permis d’analyser la stabilité du modèle<br>The aim of this work is the eddy-current testing (ECT) of ferromagnetic materials within magnetic sensors, such as Giant Magneto-Resistances (GMR). Two complementary aspects have been studied. Experimental measurements have been carried out in order to quantify and minimize the noise coming from the materials structure and residual magnetization. On the other hand, a model has been developed in order to be able to simulate the electromagnetic interactions between a ferromagnetic specimen and the EC probe. The GMR sensors are characterized by high sensitivity at low frequency, large dynamic range and are relatively easy to implement. The studies carried out during this thesis allowed us to identify and analyse the “ghost signals” due to magnetic materials. In order to minimize the noise coming from the materials structure, a linear multi-frequencies combination of experimental signals has been employed successfully and the detection of buried flaws has been improved. The residual magnetization in ferromagnetic materials has been experimentally analyzed and an electronic system has been realized to fix the polarisation point of the sensor in the linear response zone of the GMR. Thus, disturbances caused by residual magnetization are successfully reduced. Beside, in order to develop simulation tools aiming at improving the understanding of experimental signals and optimizing the performances of ECT procedures, a model has been developed to simulate the ECT of planar, stratified and ferromagnetic materials affected with multiple flaws. CEA developed for many years semi-analytical models embedded into the simulation platform CIVA dedicated to non-destructive testing. Following a previous work carried out at the laboratory and already integrated in the simulation platform CIVA, developed at CEA-LIST, the new model extends CIVA functionalities to the ferromagnetic planar case. Simulation results are obtained through the application of the Volume Integral Method (VIM) which involves the dyadic Green’s functions. Two coupled integral equations have to be solved and the numerical resolution of the system is carried out using the classical Galerkin variant of the Method of Moments (MoM). Finally, the probe response is calculated by application of the Lorentz reciprocity theorem. A collaboration with the University of Cassino (Italy) and Laboratoire de Génie Electrique de Paris (France) allowed us to compare the three models on experimental and numerical results from literature. Results showed a good agreement between the three models and the model stability has been analyzed
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Zadeh, Ramin Agha. "Performance control of distributed generation using digital estimation of signal parameters." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/47011/1/Ramin_Agha_Zadeh_Thesis.pdf.
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The Queensland University of Technology (QUT) allows the presentation of a thesis for the Degree of Doctor of Philosophy in the format of published or submitted papers, where such papers have been published, accepted or submitted during the period of candidature. This thesis is composed of seven published/submitted papers, of which one has been published, three accepted for publication and the other three are under review. This project is financially supported by an Australian Research Council (ARC) Discovery Grant with the aim of proposing strategies for the performance control of Distributed Generation (DG) system with digital estimation of power system signal parameters.
Distributed Generation (DG) has been recently introduced as a new concept for the generation of power and the enhancement of conventionally produced electricity. Global warming issue calls for renewable energy resources in electricity production. Distributed generation based on solar energy (photovoltaic and solar thermal), wind, biomass, mini-hydro along with use of fuel cell and micro turbine will gain substantial momentum in the near future. Technically, DG can be a viable solution for the issue of the integration of renewable or non-conventional energy resources. Basically, DG sources can be connected to local power system through power electronic devices, i.e. inverters or ac-ac converters. The interconnection of DG systems to power system as a compensator or a power source with high quality performance is the main aim of this study. Source and load unbalance, load non-linearity, interharmonic distortion, supply voltage distortion, distortion at the point of common coupling in weak source cases, source current power factor, and synchronism of generated currents or voltages are the issues of concern.
The interconnection of DG sources shall be carried out by using power electronics switching devices that inject high frequency components rather than the desired current. Also, noise and harmonic distortions can impact the performance of the control strategies. To be able to mitigate the negative effect of high frequency and harmonic as well as noise distortion to achieve satisfactory performance of DG systems, new methods of signal parameter estimation have been proposed in this thesis. These methods are based on processing the digital samples of power system signals. Thus, proposing advanced techniques for the digital estimation of signal parameters and methods for the generation of DG reference currents using the estimates provided is the targeted scope of this thesis. An introduction to this research – including a description of the research problem, the literature review and an account of the research progress linking the research papers – is presented in Chapter 1.
One of the main parameters of a power system signal is its frequency. Phasor Measurement (PM) technique is one of the renowned and advanced techniques used for the estimation of power system frequency. Chapter 2 focuses on an in-depth analysis conducted on the PM technique to reveal its strengths and drawbacks. The analysis will be followed by a new technique proposed to enhance the speed of the PM technique while the input signal is free of even-order harmonics. The other techniques proposed in this thesis as the novel ones will be compared with the PM technique comprehensively studied in Chapter 2.
An algorithm based on the concept of Kalman filtering is proposed in Chapter 3. The algorithm is intended to estimate signal parameters like amplitude, frequency and phase angle in the online mode. The Kalman filter is modified to operate on the output signal of a Finite Impulse Response (FIR) filter designed by a plain summation. The frequency estimation unit is independent from the Kalman filter and uses the samples refined by the FIR filter. The frequency estimated is given to the Kalman filter to be used in building the transition matrices. The initial settings for the modified Kalman filter are obtained through a trial and error exercise.
Another algorithm again based on the concept of Kalman filtering is proposed in Chapter 4 for the estimation of signal parameters. The Kalman filter is also modified to operate on the output signal of the same FIR filter explained above. Nevertheless, the frequency estimation unit, unlike the one proposed in Chapter 3, is not segregated and it interacts with the Kalman filter. The frequency estimated is given to the Kalman filter and other parameters such as the amplitudes and phase angles estimated by the Kalman filter is taken to the frequency estimation unit.
Chapter 5 proposes another algorithm based on the concept of Kalman filtering. This time, the state parameters are obtained through matrix arrangements where the noise level is reduced on the sample vector. The purified state vector is used to obtain a new measurement vector for a basic Kalman filter applied. The Kalman filter used has similar structure to a basic Kalman filter except the initial settings are computed through an extensive math-work with regards to the matrix arrangement utilized.
Chapter 6 proposes another algorithm based on the concept of Kalman filtering similar to that of Chapter 3. However, this time the initial settings required for the better performance of the modified Kalman filter are calculated instead of being guessed by trial and error exercises. The simulations results for the parameters of signal estimated are enhanced due to the correct settings applied. Moreover, an enhanced Least Error Square (LES) technique is proposed to take on the estimation when a critical transient is detected in the input signal. In fact, some large, sudden changes in the parameters of the signal at these critical transients are not very well tracked by Kalman filtering. However, the proposed LES technique is found to be much faster in tracking these changes. Therefore, an appropriate combination of the LES and modified Kalman filtering is proposed in Chapter 6. Also, this time the ability of the proposed algorithm is verified on the real data obtained from a prototype test object.
Chapter 7 proposes the other algorithm based on the concept of Kalman filtering similar to those of Chapter 3 and 6. However, this time an optimal digital filter is designed instead of the simple summation FIR filter. New initial settings for the modified Kalman filter are calculated based on the coefficients of the digital filter applied. Also, the ability of the proposed algorithm is verified on the real data obtained from a prototype test object.
Chapter 8 uses the estimation algorithm proposed in Chapter 7 for the interconnection scheme of a DG to power network. Robust estimates of the signal amplitudes and phase angles obtained by the estimation approach are used in the reference generation of the compensation scheme. Several simulation tests provided in this chapter show that the proposed scheme can very well handle the source and load unbalance, load non-linearity, interharmonic distortion, supply voltage distortion, and synchronism of generated currents or voltages. The purposed compensation scheme also prevents distortion in voltage at the point of common coupling in weak source cases, balances the source currents, and makes the supply side power factor a desired value.
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Plíšek, Oldřich. "Analýza ztrát v železe malého asynchronního motoru." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-376984.
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The aim of this master´s thesis is to analyze core losses of a small induction motor. Analyzed values are obtained from laboratory measurements, software analysis and 2D finite element method simulation. The theoretical part of this thesis consists of two parts. The analysis of the higher spatial harmonics presents in the induction motor and the analysis of core losses of the motor. Practical part consists of laboratory measurements according to ČSN. Measured values are used to calculate individual losses. The next part consists of creating a model for software analysis (Maxwell RMxprt). The generated model is converted into a 2D simulation environment (Maxwell 2D), where it is adapted to obtain values from the examined parts (rotor and stator teeth and rotor cage). Results of simulations at different loads are compared and analyzed from the point of view of higher harmonics.
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Lai, Chien-Tsung, and 賴健宗. "HYSTERESIS-CURRENT-CONTROLLED CLASS-D AMPLIFIER WITH ACTIVE CURRENT SENSING TECHNIQUES." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/03439832355051947277.
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碩士<br>龍華科技大學<br>電子系碩士班<br>94<br>A hysteresis-current-controlled (HCC) class-D amplifier with active current sensing techniques is presented in this thesis. The proposed active current sensing circuit uses no passive elements to fully measure the bi-direction inductive load current in class-D amplifier. A hysteresis-current-controller is then used to control the measured current follow a reference signal.
The entire circuit contain an error amplifier, a hysterrsis-current-controlled circuit, a sample -and-hold circuit, an active current sensing circuit, a driver circuit……etc. The details of the entire circuit will be described thoroughly in this thesis.
The class-D amplifier has been fabricated with TSMC 3.3-V, 0.35-μm double-poly quadruple-metal CMOS technology.
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Kuo, Jia-long, and 郭家龍. "Grid Connected Application with Hysteresis Current Control Method." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/02402689351963123620.
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碩士<br>中華科技大學<br>機電光工程研究所碩士班<br>100<br>The application of green energy is an important issue. This study design and implementation the controller for the wind power and the grid connected. The voltage of the wind power should be rectifier, filter, DC to DC converter, and inverter to the alternating current. The hysteresis current controller is application with parallel synchronous operation. The Hysteresis current controller using the grid voltage as reference signal so that the phase of the inverter output current is in phase with the voltage, therefore the output of inverter is unity power factor .
There are two steps in this study. The first, Using the PSim software to simulate the system. The Second, design and implement the circuit into a circuit board. In this study, using the grid voltage phase as a reference signal for the inverter current so that the frequency of the inverter output current variations with the grid voltage variations, the results show that the hysteresis current controller can follow the reference command. On the other, the Total harmonic distortion (THD) is Satisfied with the IEEE standard.
This research has good contribution for the energy shortage and carbon reduction.
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Chiu, Mao-Ling, and 邱茂菱. "An On-Chip Current Sensing Technique for Hysteresis Current-Controlled Boost Converters." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/58608561193232615955.
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碩士<br>國立清華大學<br>工程與系統科學系<br>100<br>A novel on-chip current sensing technique suitable for hysteresis-current-controlled (HCC) boost converter is presented which has some advantages, such as simple structure, the improvement of power conversion efficiency, etc.
In this thesis, the proposed hysteresis current mode boost converter has a simple structure (the slope compensation is not required) and fast transient response (it has a higher crossover frequency and enough phase margin to avoid the oscillation). When using the proposed SENSEFETs structure and the switching-capacitor technique to monitor current on a power conductor, the power efficiency of the converter can be improved and subsequently has low power consumption.
The proposed current sensing technique has been fabricated by TSMC 0.25μm CMOS HV process. In the boost converter, the operation voltage is from 3.5V to 4.5V, the output voltage ripples less than 72.5mV, current sensor can achieve 95 percent sensing accuracy, and the 91.7 percent power efficiency was achieved.
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Chen, Chih-Chiang, and 陳志強. "Hysteresis-Current-Controlled Buck/ Buck-Boost Converter Using Active Current Sensing Circuit." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/7q3egk.
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碩士<br>國立臺北科技大學<br>電腦與通訊研究所<br>94<br>In this thesis, We design a new active current sensing circuit and apply this technology fo hysteresis-current-controlled buck/buck-boost converter using active current sensing circuit for portable applications.
In the proposed DC-DC converter, the key building blocks includes power MOS, Voltage-current conversion circuit, hysteresis-current comparator, driving circuit, non-overlapping circuit and current sensing circuit. The current sensing circuit can fully sense the inductor current and be used to construct buck/buck-boost converter. The hysteresis-current-controlled can be worked in parallel. The proposed circuits have been designed with TSMC 0.35um DPQM CMOS processes. The experimental results show that the buck/ buck-boost converter works well with the following features: the maximum inductor current up to 750mA; the input voltage range is 3~6V; the output voltage range from 0.45 to input voltage-0.4V; the maximum power efficiency up to 93.6%.
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Chen, Jian-Hao, and 陳建豪. "Constant-Frequency Hysteresis-Current-Controlled DC-DC Converter with Active-Current-Sensing Techniques." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/3j6734.
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Hsieh, Ying-Cheng, and 謝英成. "Adjustable Hysteresis Current Control Scheme for Induction Motor Drive." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/33810276516938647117.
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碩士<br>中華科技大學<br>機電光工程研究所碩士班<br>101<br>Abstract
The traditional six-switch three-phase (6S3Ph) inverter is used to variable speed drive for AC motors and uninterruptible power systems over the years. However, The current control method in power electronic circuits play an important role, especially the PWM(Pulse Width Modulation) converter is widely used in AC motor drives and continuous AC power supply. The conventional methods including triangular wave or space-vector-based chopper control or hysteresis control, rather the former is a fixed switching frequency, the latter is a variables witching frequency. This thesis presents an adjustable hysteresis current control. The scheme is consisting of two single-phase switching voltage source to supply the three-phase induction machine drive. The technology is based on single-phase four-switch inverter hysteresis current controlled that can reduce the switching frequency and obtain lower harmonic performance to improved third-level phase variable voltage source with hysteresis of inverter. In this research, the output load torque and THD are used to adjust value of current waveform and hysteresis, respectively. The method could reduce the switching frequency and lose under the limit maximum THD value.ThePSimsofeware simulation and verified that the method is simple and effective.
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Kuo, Shin-Jr, and 郭信志. "A Novel Hysteresis Current Controller for Multilevel AC/DC Converters." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/55840900527899460062.
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碩士<br>國立清華大學<br>電機工程學系<br>90<br>Traditionally, only the output power quality specification is emphasized. Not much attention was paid to the harmonic pollution and power factor at the input AC line. However, with the increasingly rigid power quality requirement, more and more researches are devoted to the harmonic reduction and power factor correction in recent decade. As far as high voltage AC/DC converters are concerned, a multi-level hysteresis current controller is indeed a nice strategy to solve the about problem. However, existing multi-level hysteresis current controllers were designed based on an intuitive idea to choose a proper one among many voltage levels for the controllers. As a result, the resulting current errors may be outside the error bounds for some time period. In view of these, a novel multi-level hysteresis current control strategy is proposed based on the current error derivatives to improve the drawback of the existing methods.
In this thesis, first, a neutral-point-clamped (NPC) AC/DC converter configuration is chosen and some related control strategies proposed recently are roughly reviewed as starting background. The corresponding theoretical defect is also pointed out and demonstrated by simulation. Then, a novel multi-level hysteresis current control strategy is proposed with sound theoretical basis to correct the above drawbacks. In order to keep the merit of easy implementation of hysteresis current controllers, an approximate three-level hystersis current controller implementation is also proposed to avoid calculating the complex current error derivatives. Finally, a prototype is constructed and some experimental results are presented for verifying the feasibility of the proposed controller.
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Hsiang-YiChu and 朱湘儀. "Dual Buck Inverter with Constant Frequency Variable Hysteresis Current Control." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/90045155481958795728.
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碩士<br>國立成功大學<br>電機工程學系<br>102<br>The purpose of this thesis is to implement a dual buck inverter for tide power transfer system. Because the change of front-end tide power transfer system output AC voltage could be varying and low. By realized the first stage of boost converter to rectify and boost the voltage, then convert power to the second stage of dual buck inverter. The thesis presents a new control strategy of constant frequency with variable hysteresis width. It can design the filter and choose power components easily when using the new type control. Compare to conventional hysteresis current control, by constant frequency variable hysteresis current control, it reduces the total harmonic distortion and the ripple of output voltage. Furthermore, it raises the system of power conversion efficiency. Finally, the thesis proposed a prototype 500 watt dual buck inverter system is implemented. The maximum efficiency of the system is 97% and THD is less than 2%.
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ZHANG, LONG-KAI, and 張隆凱. "A Temperature-Based Hysteresis Buck Converter for Dynamic Current Sharing." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/dbe3cm.
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碩士<br>逢甲大學<br>電子工程學系<br>107<br>In this study, a temperature-based dynamic current sharing will be applied to improve reliability of uninterruptible power system (UPS).According to temperature information of each power supply module to redistribute output current, we let hotter power module supply lower current to load for achieve better thermal balance of UPS.In this design, we implement by the UMC 0.25µm CMOS technology.Input range 2.9V-3.1V and regular output voltage at 0.825V, maximum output current of each phase is 100mA. We also propose current sharing error correction to improve current sharing performance according to average current of each phase on condition without temperature difference. Final the current sharing error can within ±2% by use current sharing error correction circuit and efficiency higher than 75%.
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Kumar, Avinash. "An adaptive hysteresis band current controlled unified power quality conditioner." Thesis, 2013. http://ethesis.nitrkl.ac.in/4658/1/211EE2124.pdf.
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Presence of Harmonics is one of the major power quality problems in the present power system. It is demanded that the utility should ideally provide a balanced and pure sinusoidal three-phase voltage of constant amplitude to the loads. But, with the excessive use of non-linear loads (ASD, Computers, Laser printers, SMPS, Rectifier etc.) power distribution system is getting polluted by harmonics and reactive power disturbances. Harmonics cause a number of undesirable effects like heating, equipment damage and Electromagnetic Interference effects in the nearby communication system. Active power filter (APF) or Active power line conditioner (APLC) is a suitable solution to compensate the adverse effects of harmonics and reactive power simultaneously. There are various topologies of APFs, one of them is Unified power Quality Conditioner (UPQC) which has two inverters connected back to back with same dc link. In this paper a three-phase–three wire UPQC, is proposed for harmonic compensation at point of common coupling (PCC) which are present due to the presence of non-linear load. Reference signals were generated using synchronous reference frame theory (SRF). While the gating signals were generated using Adaptive Hysteresis Band Current Controller (AHCC). Simulation of the proposed UPQC model was done using MATLAB/SIMULINK and result shows that it achieves superior capability of mitigating the effects of voltage sag/swell and reduces the THD of source current within the IEEE standard of harmonic limit. while AHCC successfully maintains the switching frequency almost constant.
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Ho, Chumg-Lin, and 何中麟. "Design and Implementation of New Hysteresis-Current Controlled Buck Converter and Current Feedback Voltage Regulator." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/rgn644.
Full textAbstract:
碩士<br>國立臺北科技大學<br>電腦與通訊研究所<br>97<br>The major research of this thesis can be divided into two parts. In the first part shows the new hysteresis-current-controlled buck converter. It contains some sub-circuiths, inclusive of a power MOS, a current sensing circuit, a sample and hold circuit, a hysteresis-current comparator circuit, a non-overlapping circuit, a driving circuit, a compensator circuit and a zero current detector circuit. The current sensing circuit can fully sense the inductor current and the zero current detector circuit improves effectively at the light load. The proposed circuits have been implemented with TSMC 0.35μm DPQM CMOS processes and the chip area is 0.888mm x 0.949mm with PAD.
In the second part of this thesis, the LDO building block includes an error amplifier, a pass element, an off-chip capacitor and resistors. The error amplifier is used to detect the reference and the feedback voltages. It is generated an output voltage proportional to the difference between these two voltages (reference and feedback voltages), which in turn biases the pass transistor through a base driver circuit. The error amplifier and driver circuit base negative feedback loop that maintains the regulator output voltage at the desired level. Voltage regulators can be used in SOC usually need fast transient response and low power consumption. The current feedback for fast response is provided by Current conveyor II (CCII) based on LDO.
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Chiang, Ming-Che, and 江明哲. "Energy Efficiency-Improved Hysteresis Current Controllers Design for Induction Motor Drives." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/41894366043945445630.
Full textAbstract:
碩士<br>國立東華大學<br>電機工程學系<br>102<br>In general, hysteresis current control on voltage-fed inverters is a simple and effective control method for AC motor drives. This is because the control method can give a good and fast transient response of the 3-phase currents. However, the drawbacks of the variable switching frequency and high-frequency harmonic are usually introduced in the motor drives.
In this thesis, an adaptive hysteresis current control method for indirect field-oriented induction motor drive is presented. In the adaptive hysteresis current control, the hysteresis band is adaptively tuned according th the condition of the stator current and rotor flux so as to fix the switching frequency to decrease the high-frequency harmonics. After that, various dead-time schemes about delayed turning on and off of the power switches are proposed. From analysis of the testing results, a better dead-time scheme that can effectively reduce the power consumption and increase the power factor is given.
To confirm the validity of the proposed methods, simulation results from a three-phase induction motor system are illustrated, and from the illustration, some conclusions are given for the proposed methods in this thesis.