Dissertations / Theses on the topic 'Current voltage and power voltage characteristics'
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1
Svrček, Milan. "Metody pro dosažení maximálního výkonu FV modulů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-318171.
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This diploma thesis deals with the tracking of the maximum power point for photovoltaic panels and the methods used to achieve it. On this basis, two methods were designed and programmed and subsequently tested on three types of photovoltaic panels. In conclusion methods were appraised.
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Ghasemi, Negareh. "Improving ultrasound excitation systems using a flexible power supply with adjustable voltage and frequency to drive piezoelectric transducers." Thesis, Queensland University of Technology, 2012. https://eprints.qut.edu.au/61091/1/Negareh_Ghasemi_Thesis.pdf.
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The ability of a piezoelectric transducer in energy conversion is rapidly expanding in several applications. Some of the industrial applications for which a high power ultrasound transducer can be used are surface cleaning, water treatment, plastic welding and food sterilization. Also, a high power ultrasound transducer plays a great role in biomedical applications such as diagnostic and therapeutic applications. An ultrasound transducer is usually applied to convert electrical energy to mechanical energy and vice versa. In some high power ultrasound system, ultrasound transducers are applied as a transmitter, as a receiver or both. As a transmitter, it converts electrical energy to mechanical energy while a receiver converts mechanical energy to electrical energy as a sensor for control system. Once a piezoelectric transducer is excited by electrical signal, piezoelectric material starts to vibrate and generates ultrasound waves. A portion of the ultrasound waves which passes through the medium will be sensed by the receiver and converted to electrical energy. To drive an ultrasound transducer, an excitation signal should be properly designed otherwise undesired signal (low quality) can deteriorate the performance of the transducer (energy conversion) and increase power consumption in the system. For instance, some portion of generated power may be delivered in unwanted frequency which is not acceptable for some applications especially for biomedical applications.
To achieve better performance of the transducer, along with the quality of the excitation signal, the characteristics of the high power ultrasound transducer should be taken into consideration as well. In this regard, several simulation and experimental tests are carried out in this research to model high power ultrasound transducers and systems. During these experiments, high power ultrasound transducers are excited by several excitation signals with different amplitudes and frequencies, using a network analyser, a signal generator, a high power amplifier and a multilevel converter. Also, to analyse the behaviour of the ultrasound system, the voltage ratio of the system is measured in different tests. The voltage across transmitter is measured as an input voltage then divided by the output voltage which is measured across receiver. The results of the transducer characteristics and the ultrasound system behaviour are discussed in chapter 4 and 5 of this thesis.
Each piezoelectric transducer has several resonance frequencies in which its impedance has lower magnitude as compared to non-resonance frequencies. Among these resonance frequencies, just at one of those frequencies, the magnitude of the impedance is minimum. This resonance frequency is known as the main resonance frequency of the transducer. To attain higher efficiency and deliver more power to the ultrasound system, the transducer is usually excited at the main resonance frequency. Therefore, it is important to find out this frequency and other resonance frequencies. Hereof, a frequency detection method is proposed in this research which is discussed in chapter 2.
An extended electrical model of the ultrasound transducer with multiple resonance frequencies consists of several RLC legs in parallel with a capacitor. Each RLC leg represents one of the resonance frequencies of the ultrasound transducer. At resonance frequency the inductor reactance and capacitor reactance cancel out each other and the resistor of this leg represents power conversion of the system at that frequency. This concept is shown in simulation and test results presented in chapter 4.
To excite a high power ultrasound transducer, a high power signal is required. Multilevel converters are usually applied to generate a high power signal but the drawback of this signal is low quality in comparison with a sinusoidal signal. In some applications like ultrasound, it is extensively important to generate a high quality signal. Several control and modulation techniques are introduced in different papers to control the output voltage of the multilevel converters. One of those techniques is harmonic elimination technique. In this technique, switching angles are chosen in such way to reduce harmonic contents in the output side. It is undeniable that increasing the number of the switching angles results in more harmonic reduction. But to have more switching angles, more output voltage levels are required which increase the number of components and cost of the converter. To improve the quality of the output voltage signal with no more components, a new harmonic elimination technique is proposed in this research. Based on this new technique, more variables (DC voltage levels and switching angles) are chosen to eliminate more low order harmonics compared to conventional harmonic elimination techniques. In conventional harmonic elimination method, DC voltage levels are same and only switching angles are calculated to eliminate harmonics. Therefore, the number of eliminated harmonic is limited by the number of switching cycles. In the proposed modulation technique, the switching angles and the DC voltage levels are calculated off-line to eliminate more harmonics. Therefore, the DC voltage levels are not equal and should be regulated. To achieve this aim, a DC/DC converter is applied to adjust the DC link voltages with several capacitors. The effect of the new harmonic elimination technique on the output quality of several single phase multilevel converters is explained in chapter 3 and 6 of this thesis.
According to the electrical model of high power ultrasound transducer, this device can be modelled as parallel combinations of RLC legs with a main capacitor. The impedance diagram of the transducer in frequency domain shows it has capacitive characteristics in almost all frequencies. Therefore, using a voltage source converter to drive a high power ultrasound transducer can create significant leakage current through the transducer. It happens due to significant voltage stress (dv/dt) across the transducer. To remedy this problem, LC filters are applied in some applications. For some applications such as ultrasound, using a LC filter can deteriorate the performance of the transducer by changing its characteristics and displacing the resonance frequency of the transducer. For such a case a current source converter could be a suitable choice to overcome this problem. In this regard, a current source converter is implemented and applied to excite the high power ultrasound transducer. To control the output current and voltage, a hysteresis control and unipolar modulation are used respectively. The results of this test are explained in chapter 7.
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Шевченко, Сергій Юрійович. "Вплив вищих гармонік напруги на вибір та експлуатацію обмежувачів перенапруг для захисту систем електропостачання." Thesis, НТУ "ХПІ", 2015. http://repository.kpi.kharkov.ua/handle/KhPI-Press/18478.
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Дисертація на здобуття наукового ступеня доктора технічних наук за спецiальністю 05.09.03 - електротехнiчнi комплекси та системи. - Національний технічний університет "Харківський політехнічний інститут". Харків 2015 р.
Дисертація присвячена актуальній науково-технічній проблемі визначення пливу вищих гармонік напруги на вибір та експлуатацію обмежувачів перенапруг для захисту електротехнічних комплексів та систем, що має важливе значення та забезпечує підвищення ефективності та надійності функціонування систем електропостачання. В рамках даного напряму отримані наступні результати. Виконано аналіз існуючих вимог до вибору та експлуатації перенапруг нелінійних (ОПН) в системах електропостачання різних класів напруги; Проведено експериментальні дослідження електрофізичних характеристик варисторів та ОПН в зібраному стані провідних світових виробників при різних частотах прикладеної напруги та вольт амперних характеристик варисторів і ОПН в зібраному стані в зоні струмів витоку. Удосконалено математичну модель для вибору енергетичних характеристик ОПН при низькій якості електричної енергії в системі електропостачання на базі схем заміщення ОПН в зоні струмів витоку їх вольт-амперної характеристики (ВАХ). Запропановано метод визначення втрат активної потужності в ОПН на базі отриманих ВАХ в зоні струмів витоку, та проведено аналіз впливу несинусоїдальності напруги на величину енергії, що діє на ОПН, а також визначено вплив на нормальну роботу ОПН перенапруг грозового і комутаційного імпульсів струму та підвищеної напруги промислової частоти. Розроблено методи визначення ВАХ ОПН в зоні струмі витоку на основі отриманих експериментальних ВАХ ОПН, які базуються на нейронних мережах та апроксимацією ВАХ двома кривими першого порядку. Удосконалено математичну модель теплових режимів ОПН при низькій якості електричної енергії в системі електропостачання та виконані дослідження впливу різних чинників на теплову стабільність ОПН. Експериментально досліджено наявність порушень якості електричної енергії в системах електропостачання різних видів промисловості України. Удосконалено методи вибору ОПН в системах електропостачання різних номінальних напруг з низькою якістю електричної енергії. Сформульовані основні засади застосування та експлуатації ОПН при впливі вищіх гармонік напруги. Обгрунтовано використання тепловізорів та пірометрів для експлуатаційного контролю стану ОПН.The thesis for the degree of doctor of technical sciences, specialty 05.09.03 - Electrotechnical complexes and systems. - National Technical University "Kharkiv Polytechnic Institute". Kharkov 2015. Dissertation is devoted to actual scientific and technical problem of determining the effect of the higher harmonics of the voltage on the selection and exploitation of surge arresters for protection electricity supply systems is important and enhances the efficiency and reliability of power supply systems. In this area, the following results. The analysis of existing requirements for the selection and exploitation of surge arresters in electricity supply systems of different voltage classes. Experimental studies of electrophysical characteristics of varistors and surge arresters assembled the world's leading manufacturers in the different frequencies of the applied voltage and current voltage characteristics of varistors and surge arresters in an assembled state in the area of leakage current. Іmproved the mathematical model for selecting the energy characteristics of the arrester at a low power quality in the power supply system on the basis of equivalent circuits in the area of the arrester leakage current of the current-voltage characteristics (CVC). Offered the method for determination of active power losses in the arrester on the basis of the obtained current-voltage characteristics in the area of leakage current and the analysis of the impact of non-sinusoidal voltage to the amount of energy exerted on surge arresters, as well as determined the effect of the normal operation of surge arresters Surge lightning and switching current pulses and high frequency voltage. Developed the methods for determining the current-voltage characteristics in the area of the arrester leakage current on the basis of the experimental CVC arresters based on neural networks and approximation CVC two curves of the first order. Іmproved the mathematical model of thermal modes of surge arresters in low power quality in the power supply system and to study the effect of different factors on the thermal stability of the arrester. Experimentally investigated for poor quality of electricity supply systems of various types of industry of Ukraine; An improved method for selecting surge arresters in power supply systems of different rated voltages with low quality electric energy. Іmproved the basic principles for the use and operation of surge arresters under the influence of higher harmonic voltage. Justify the use of thermal imagers and pyrometers for operational monitoring of the arrester.
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Шевченко, Сергій Юрійович. "Вплив вищих гармонік напруги на вибір та експлуатацію обмежувачів перенапруг для захисту систем електропостачання." Thesis, НТУ "ХПІ", 2015. http://repository.kpi.kharkov.ua/handle/KhPI-Press/18479.
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Дисертація на здобуття наукового ступеня доктора технічних наук за спецiальністю 05.09.03 - електротехнiчнi комплекси та системи. - Національний технічний університет "Харківський політехнічний інститут". Харків 2015 р. Дисертація присвячена актуальній науково-технічній проблемі визначення пливу вищих гармонік напруги на вибір та експлуатацію обмежувачів перенапруг для захисту електротехнічних комплексів та систем, що має важливе значення та забезпечує підвищення ефективності та надійності функціонування систем електропостачання. В рамках даного напряму отримані наступні результати. Виконано аналіз існуючих вимог до вибору та експлуатації перенапруг нелінійних (ОПН) в системах електропостачання різних класів напруги; Проведено експериментальні дослідження електрофізичних характеристик варисторів та ОПН в зібраному стані провідних світових виробників при різних частотах прикладеної напруги та вольт амперних характеристик варисторів і ОПН в зібраному стані в зоні струмів витоку. Удосконалено математичну модель для вибору енергетичних характеристик ОПН при низькій якості електричної енергії в системі електропостачання на базі схем заміщення ОПН в зоні струмів витоку їх вольт-амперної характеристики (ВАХ). Запропановано метод визначення втрат активної потужності в ОПН на базі отриманих ВАХ в зоні струмів витоку, та проведено аналіз впливу несинусоїдальності напруги на величину енергії, що діє на ОПН, а також визначено вплив на нормальну роботу ОПН перенапруг грозового і комутаційного імпульсів струму та підвищеної напруги промислової частоти. Розроблено методи визначення ВАХ ОПН в зоні струмі витоку на основі отриманих експериментальних ВАХ ОПН, які базуються на нейронних мережах та апроксимацією ВАХ двома кривими першого порядку. Удосконалено математичну модель теплових режимів ОПН при низькій якості електричної енергії в системі електропостачання та виконані дослідження впливу різних чинників на теплову стабільність ОПН. Експериментально досліджено наявність порушень якості електричної енергії в системах електропостачання різних видів промисловості України. Удосконалено методи вибору ОПН в системах електропостачання різних номінальних напруг з низькою якістю електричної енергії. Сформульовані основні засади застосування та експлуатації ОПН при впливі вищіх гармонік напруги. Обгрунтовано використання тепловізорів та пірометрів для експлуатаційного контролю стану ОПН.The thesis for the degree of doctor of technical sciences, specialty 05.09.03 - Electrotechnical complexes and systems. - National Technical University "Kharkiv Polytechnic Institute". Kharkov 2015. Dissertation is devoted to actual scientific and technical problem of determining the effect of the higher harmonics of the voltage on the selection and exploitation of surge arresters for protection electricity supply systems is important and enhances the efficiency and reliability of power supply systems. In this area, the following results. The analysis of existing requirements for the selection and exploitation of surge arresters in electricity supply systems of different voltage classes. Experimental studies of electrophysical characteristics of varistors and surge arresters assembled the world's leading manufacturers in the different frequencies of the applied voltage and current voltage characteristics of varistors and surge arresters in an assembled state in the area of leakage current. Іmproved the mathematical model for selecting the energy characteristics of the arrester at a low power quality in the power supply system on the basis of equivalent circuits in the area of the arrester leakage current of the current-voltage characteristics (CVC). Offered the method for determination of active power losses in the arrester on the basis of the obtained current-voltage characteristics in the area of leakage current and the analysis of the impact of non-sinusoidal voltage to the amount of energy exerted on surge arresters, as well as determined the effect of the normal operation of surge arresters Surge lightning and switching current pulses and high frequency voltage. Developed the methods for determining the current-voltage characteristics in the area of the arrester leakage current on the basis of the experimental CVC arresters based on neural networks and approximation CVC two curves of the first order. Іmproved the mathematical model of thermal modes of surge arresters in low power quality in the power supply system and to study the effect of different factors on the thermal stability of the arrester. Experimentally investigated for poor quality of electricity supply systems of various types of industry of Ukraine; An improved method for selecting surge arresters in power supply systems of different rated voltages with low quality electric energy. Іmproved the basic principles for the use and operation of surge arresters under the influence of higher harmonic voltage. Justify the use of thermal imagers and pyrometers for operational monitoring of the arrester.
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Massi, Pavan Alessandro. "A hardware field simulator for photovoltaic materials applications." Doctoral thesis, Università degli studi di Trieste, 2008. http://hdl.handle.net/10077/2757.
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2006/2007Il presente lavoro riguarda la descrizione di un simulatore di campo fotovoltaico (in seguito simulatore). Il simulatore è un convertitore elettronico di potenza che, alimentato dalla rete elettrica, riproduce la caratteristica tensione corrente di un campo fotovoltaico (insieme di moduli fotovoltaici connessi in serie e in parallelo) operante in condizioni climatiche di temperatura e irraggiamento arbitrarie. Il nuovo dispositivo verrà impiegato nell’ambito del laboratorio fotovoltaico cui fa riferimento l’impianto in via di realizzazione sul tetto dell’edificio che ospita il Dipartimento dei Materiali e delle Risorse Naturali dell’Università di Trieste. Il simulatore viene proposto come utile strumento per i progettisti di dispositivi solari funzionanti in sistemi fotovoltaici connessi in rete. In particolare, il simulatore permetterà di prevedere il funzionamento di nuovi moduli fotovoltaici operanti in condizioni di ombreggiamento arbitrario e inseriti in un sistema fotovoltaico reale. L’uso del simulatore sarà particolarmente efficace nel caso di simulazioni di tecnologie in film sottile come, ad esempio, il silicio amorfo, il tellururo di cadmio, ecc. Il simulatore sarà anche necessario per testare i componenti che fanno parte di un sistema fotovoltaico connesso in rete, con particolare riferimento ai sistemi di condizionamento della potenza (detti anche inverter). Tali sistemi, oltre a convertire la tensione continua prodotta dai moduli fotovoltaici in una tensione compatibile e sincronizzata con quella della rete, devono garantire istante per istante l’inseguimento del punto di massima potenza estraibile dal campo fotovoltaico cui sono connessi. Il lavoro è stato suddiviso in cinque capitoli. Il primo capitolo fornisce una breve descrizione dello stato dell’arte e di alcune aspetti economici relativi alla tecnologia fotovoltaica. Nel secondo capitolo vengono richiamati il modello classico di una cella solare e le definizioni riguardo le sue caratteristiche principali (punto di massima potenza, efficienza, fill factor, ecc.). Nello stesso capitolo un’overview sui materiali e sulle tecnologie utilizzate nella realizzazione dei dispositivi fotovoltaici divide, come suggerito da Martin Green, le celle solari in tre diverse generazioni: la prima comprende i dispositivi realizzati in silicio cristallino (mono e policrisallino), la seconda quelli in film sottile (in silicio amorfo, tellururo di cadmio CdTe, diseleniuro di rame e indio CIS, diseleniuro di rame, indio e gallio CIGS, diseleniuro di rame, indio, gallio e zolfo CIGSS) e le celle di Graetzel, e la terza le celle multigiunzione, a banda intermedia e quelle organiche. Nel capitolo tre viene fornita una descrizione dei componenti costituenti un sistema fotovoltaico connesso in rete e viene proposto un nuovo metodo per la determinazione delle caratteristiche corrente tensione e potenza tensione prodotte da dispositivi fotovoltaici. Il metodo risulta efficace in quanto non necessita di misure sperimentali da effetture sui diversi dispositivi. I dati forniti nei comuni data sheet che vengono forniti a corredo dei moduli fotovoltaici sono sufficienti a determinarne il comportamento al variare della temperatura di funzionamento e del livello di radiazione solare. L’efficienza di un sistema fotovoltaico (Balance Of the System, BOS) viene calcolata nel capitolo quattro. Particolare enfasi viene data all’effetto di mismatching che è tanto più importante quanto più è elevato il livello di ombreggiamento presente sul piano dei moduli fotovoltaici costituenti l’impianto. Infine, l’ultimo capitolo riguarda la descrizione del simulatore e delle sue applicazioni.
The subject of this work is a power electronic device, hereafter named photovoltaic field simulator, which converts the grid voltage into a current voltage characteristic. This characteristic replicates the behavior of a real photovoltaic field working in arbitrary conditions of irradiance and temperature. After building, the photovoltaic field simulator will be used in the photovoltaic laboratory which is connected to the experimental photovoltaic plant which will be installed on the roof top of the Materials and Natural Resources Department of Trieste University. The photovoltaic field simulator will be used for photovoltaic module parameters design with particular reference to its behavior when inserted in a photovoltaic field operating under shaded conditions. The use of the simulator will be particularly effective when simulating thin-film technologies as, for example, amorphous silicon, cadmium telluride, and etc. The photovoltaic field simulator will also be used for testing the components of grid connected photovoltaic systems with particular reference to the power conditioning units (also named inverters). These systems, which convert the direct current produced by the photovoltaic modules into a utility grade current (typically alternate and sinusoidal at a frequency of 50-60Hz), must extract maximum power from the photovoltaic field. The work is divided into five chapters. In the first a brief description of photovoltaic technology and its economic aspects is given. Chapter two is on classic solar cell modelling basics and on the definition of the parameters of photovoltaic technology (maximum power point, efficiency, fill factor, and etc.). In the same chapter a materials and technologies overview splits, as suggested by Martin Green, solar cells in three different generations: the first comprises crystalline silicon (mono and polycrystalline) devices, the second thin-film devices (amorphous silicon, cadmium telluride CdTe, copper indium diselenide CIS, copper indium gallium diselenide CIGS, copper indium gallium sulphur diselenide CIGSS), and the Graetzel cells, while the third multi-junction, intermediate band and organic photovoltaic devices. The third chapter briefly describes photovoltaic grid connected system components. In particular a new model for plotting photovoltaic current voltage and power voltage characteristics is provided. The method is original because only module data sheet parameters are used and experimental measurements are not needed in order to determine the photovoltaic modules behavior with reference to irradiance and working temperatures changes. In chapter four the Balance of a photovoltaic System (BOS) is calculated. In particular the importance of the mismatching effect of photovoltaic modules due to shaded conditions is shown. The last chapter is on simulator description and its applications.
XX Ciclo
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Hölling, Matthias. "Adaptive current and voltage measurement device for low voltage distribution in power nets /." [S.l.] : [s.n.], 2000. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13985.
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Ren, Huilin. "Current Voltage Characteristics of a Semiconductor Metal Oxide Sensor." Fogler Library, University of Maine, 2001. http://www.library.umaine.edu/theses/pdf/RenH2001.pdf.
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McClusky, Scott Logan. "HIGH VOLTAGE RESONANT SELF-TRACKING CURRENT-FED CONVERTER." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/254.
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High voltage power supply design presents unique requirements, combining safety, controllability, high performance, and high efficiencies. A new Resonant Self-Tracking Current-Fed Converter (RST-CFC) is investigated as a proof-of-concept of a high voltage power supply particularly for an X-ray system. These systems require fast voltage rise times and low ripple to yield a clear image.
The proposed converter implements high-frequency resonance among discrete components and transformer parasitics to achieve high voltage gain, and the self-tracking nature ensures operation at maximum gain while power switches achieve zero-voltage switching across the full load range. This converter exhibits an inherent indefinite short-circuit capability. Theoretical results were obtained through simulations and verified by experimental results through a complete test configuration. Converter topology viability was confirmed through hardware testing and characterization.
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Špinar, Marek. "Ověření provozní výkonnosti a optimalizace FVE." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-241950.
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The Master´s thesis deals with issues of operational performance of two photovoltaic power plants. In the thesis is stated the history of photovoltaics, description of photovoltaic effect, used materials and production technology of the most used material in PV industry – Silicon. The basic parts and parameters of photovoltaic power plant are described. Thesis also solves, how could be done the first and periodically control due to relevant directives. The ways of diagnostics potentional failures, methods of measuring and the exam of monitoring system are stated. Practice part is focused on measuring and comparing operational performance of FVE Kurdějov and FVE Šakvice II. Operational performance was calculated from exported data for years 2014 and 2015. The thesis also contains measuring of each string connected to inventors, which are installed on the power plant. The result is an identification of strings with decreased operational performance. Based on that was created recommendations for optimalization and increase of the performance. The last part is software for simulation of photovoltaic power plant. This SW calculates potentional energy, which could be produced in a day with available data export. The calculation is defined by parameters, which are assigned.
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Chen, Wei. "Low Voltage High Current Power Conversion with Integrated Magnetics." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30518.
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Very low voltage, high current output requirement have necessitated improvements in power supply's density and efficiency. Existing power conversion techniques cannot meet very stringent size and efficiency requirements. By applying the proposed magnetic integration procedure, new integrated magnetic circuits featuring low loss, simple structure, and ripple cancellation technique are then developed to overcome the limitations of prior art. Both cores and windings are integrated. Consequently, the power loss and the size of the integrated magnetic device are greatly reduced. Detailed analysis and design considerations of the proposed circuits are presented. As a result of applying the proposed technique, very high density, high efficiency, low voltage, high current power modules were developed. A typical example features an isolated 3.3V/30A power module with a power density of 130W/in3 and an efficiency of 90% at 500 KHz switching frequency.Ph. D.
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Solanki, Jitendra [Verfasser]. "High power factor high-current variable-voltage rectifiers / Jitendra Solanki." Paderborn : Universitätsbibliothek, 2015. http://d-nb.info/1072683474/34.
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Mugala, Gavita. "High frequency characteristics of medium voltage XLPE power cables." Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-560.
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Twining, Erika. "Voltage compensation in weak distribution networks using shunt connected voltage source converters." Monash University, Dept. of Electrical and Computer Systems Engineering, 2004. http://arrow.monash.edu.au/hdl/1959.1/9701.
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Chen, Cheng. "The Impact of Voltage Dip Characteristics on Low Voltage Ride Through of DFIG-based Wind Turbines." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-254388.
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In last decade, there is a large increase in installed capacity of wind power. Asmore wind power is integrated into utility networks, related technologychallenges draw much attention. The doubly fed induction generator (DFIG) isthe mainstream choice for wind turbine generator (WTG) in current market andthe object of this thesis. It is very sensitive to voltage dips. The enhancement oflow voltage ride through (LVRT) is one of the most important issues for DFIG,and many works have already been done to provide solutions.In current works, the voltage dip waveforms that are applied in LVRTrelated works are largely different from waveforms in reality, because they failto consider the the effect of realistic wind farm configurations on waveforms ofvoltage dips and significant influences of additional characteristics of voltagedips. The true impact of the voltage dip needs to be assessed in performanceevaluation and development of LVRT methods. To support the development ofpractical LVRT capacity enhancement solutions, the application of voltage dipknowledge is definitely demanded.In this thesis, the characteristics of realistic waveform voltage dips in windfarm are analyized based on voltage dip knowldege from power quality field,measured voltage dip from industry and realistic wind farm configurations.Classical analysis theory is applied to explain the principles of the impact ofvoltage dip characteristics on dynamic behavior of DFIG. The impacts of manywidely neglected characteristics such as phase angle jump (PAJ), point on wave(POW) of initiation and recovery, voltage recovery process, transformerconfigurations, load effect are revealed and verified by simulations. The impactof many voltage dip characteristics on DFIG are studied for the first time.De senaste tio åren har sett en stor ökning av installerad effekt av vindkraft.Mer vindkraft i elnäten har lett till större uppmärksamhet om dess tekniskautmaningar. Den dubbelmatad asynkrongenerator (DFIG) är idag denvanligaste förekommande typen i vindkraftverk. Den är mycket känslig förspänningssänkningar. Förbättring av tålighet för spänningssänkningar (LVRT)är en av de viktigaste frågorna för DFIG, och många studier har redan söktlösningar.I befintliga studier om LVRT har spänningssänkningarna skiljt sig väsentligtfrån verkliga vågformer, då de inte har tagit hänsyn till realistiskavindparkkonfigurationer och betydande påverkan av ytterligare egenskaper hosspänningssänkningar. För att stödja utvecklingen av praktiska LVRT lösningarbehövs mer kunskap om spänningssänkningar för att bedöma dess verkligainverkan.Detta examensarbete förbättrar LVRT analysen av DFIG genom att tillämpakunskap om spänningssänkningar från elkvalitetsområdet, tillsammans medrealistiska vindparkskonfigurationer. Inflytandet av ändringar i fasvinkel(PAJ), fasvinkeln vid sänkning och återhämtning (POW), spänningsåterhämtning, transformatorkonfigurationer, last och många andra egenskaperav spänningssänkningar ingår också. Inflytandet av många egenskaper avspänningssänkningar studeras här akademiskt för första gången. Denkaraktäristik av realistiska spänningssänkningar som inträffar vid generatornspoler, och de effekter dessa har, studeras och förklaras genom teoretisk analysoch intensiva simuleringar.
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Franchi, Jimmy. "Investigation of the electronicstructures of single molecularjunctions from current voltage characteristics." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-129288.
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Molecular electronics has lately shown significant progress due to rapid advances in investigative methods and is vital to the future of the electronic industry since the fundamental limits of the solid state transistors are closer than ever. To reach the application of using single molecules as electronic components, it is imperative to investigate the electronic structure of a single molecule connected to metal electrodes. This research has focused on examining current voltage behavior to clarify the electronic structure using transition voltage spectroscopy (TVS) and a single level tunneling (SLT) model. In an approximate model, TVS can be used to determine the molecule frontier orbital-electrode energy gap (EF -ξ0) and in most cases prove molecular presence in the junction. The SLT model can be tted to experimental data to obtain molecule-electrode bond strength and molecule-electrode energy gap. The measurement system prepared and tested was a mechanically controlled break junction. It has ability not only to test current voltage characteristics but also probe external magnetic and electric eld modulation eects. The current-voltage characteristics of benzenedithiol, hexanedithiol and a recently synthesized oligothiophene molecule with five thiophene rings were measured and analysed by using TVS and tting the SLT model. Most of the current-voltage characteristics could be tted using the SLT model. Analysis revealed that the variation in molecular conductance is mainly due to variation in molecule-electrode coupling strength and not due to the EF -ξ0 energy gap. Dierent EF -ξ0 were discovered for the three dierent molecules. It was shown that the transition voltage roughly approximates the EF -ξ0 energy gap by comparing the TVS results to the results obtained from fitting the SLT model.
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Sosnowski, J. "Influence of Nano-defects on Current-voltage Characteristics of HTc Superconductors." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35112.
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Theoretical analysis is presented of the influence on the current-voltage characteristics of the nanosized
defects, which may be created by heavy ions irradiation or can arise in technological process, for instance
during the winding procedure of the superconducting coil. Results of calculations, performed basing
on developed model of the interaction of pancake type vortices appearing in HTc superconductors with
nano-sized defects are presented. The energy balance for flux creep process is deduced and current-voltage
characteristics calculated in the function of static magnetic field, in accordance with experimental behavior.
This static analysis has been extended further on the case of the time-varying magnetic field in which
existence of dynamical anomalies is predicted, according to our previous experimental data.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35112
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Tiancheng, Zhang, and Zhang Yunlin. "High voltage Direct Current lines in the Chinese electric power system." Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-12757.
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Ridenour, Daniel Keith. "Examination of Power Systems Solutions Considering High Voltage Direct Current Transmission." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/63927.
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Since the end of the Current Wars in the 19th Century, alternating current (AC) has dominated the production, transmission, and use of electrical energy. The chief reason for this dominance was (and continues to be) that AC offers a way minimize transmission losses yet transmit large power from generation to load. With the Digital Revolution and the entrance of most of the post-industrialized world into the Information Age, energy usage levels have increased due to the proliferation of electrical and electronic devices in nearly all sectors of life. A stable electrical grid has become synonymous with a stable nation-state and a healthy populace.
Large-scale blackouts around the world in the 20th and the early 21st Centuries highlighted the heavy reliance on power systems and because of that, governments and utilities have strived to improve reliability. Simultaneously occurring with the rise in energy usage is the mandate to cut the pollution by generation facilities and to mitigate the impact grid expansion has on environment as a whole. The traditional methods of transmission expansion are beginning to show their limits as utilities move generation facilities farther from load centers, which reduces geographic diversity, and the integration of nondispatchable, renewable energy sources upsets the current operating regime. A challenge faces engineers - how to expand generation, expand transmission capacity, and integrate renewable energy sources while maintaining maximum system efficiency and reliability.
A technology that may prove beneficial to the operation of power system is high voltage direct current transmission. The technology brings its own set of advantages and disadvantages, which are in many ways the complement of AC. It is important to update transmission planning processes to account for the new possibilities that HVDC offers. This thesis submits a discussion of high voltage direct current transmission technology itself and an examination of how HVDC can be considered in the planning process.Master of Science
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Gammon, Tammy Lea. "Improved arcing-fault current models for low-voltage power systems (<1kV)." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/15675.
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Jimenez, Carrizosa Miguel. "Hierarchical control scheme for multi-terminal high voltage direct current power networks." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112039/document.
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Cette thèse traite de la commande hiérarchique de réseaux à courant continu multi-terminaux à haute tension (MT-HVDC) intégrant des sources d'énergie renouvelables à grande échelle. Le schéma de contrôle proposé est composé de quatre ‘couches’ : le contrôle local où se trouvent les convertisseurs de puissance, avec une échelle de temps de l’ordre de la milliseconde ; le contrôle primaire qui est décentralisé et appliqué à plusieurs terminaux avec une échelle du temps de l’ordre de la seconde ; un niveau de commande où la communication est prise en compte et où l’approche de Modèle du Commande Prédictive (MPC) assure la planification de la tension et de la puissance à leur état d'équilibre, pour l'ensemble du système; enfin, le contrôleur de niveau supérieur, qui est principalement basé sur les techniques d'optimisation, où les aspects économiques sont pris en compte (il s’agit du réglage dit tertiaire).Au niveau des convertisseurs, un accent particulier est mis sur les convertisseurs bidirectionnels DC/DC. Dans cette thèse, trois topologies différentes sont étudiées en profondeur: deux phases Dual Active Bridge (DAB), trois phases DAB, et l’utilisation de la technologie Modular Multilevel converter (MMC) comme convertisseur DC/DC. Pour chaque topologie, une commande non-linéaire spécifique est discutée. D’autre part une nouvelle fonction pour le convertisseur DC/DC est étudiée. Il s’agit de son utilisation comme disjoncteur à courant continu (DC-CB). En ce qui concerne le contrôle primaire, qui permet de maintenir le niveau de tension continue dans le réseau, nous avons étudié trois philosophies de contrôle: celle de maître/esclave, celui du contrôle « voltage margin control » et celle de la commande du statisme (droop control). Enfin, nous avons choisi d'utiliser le droop control, entre autres, parce que la communication entre les nœuds n’est pas nécessaire. Concernant la commande secondaire, son principal objectif est de planifier le transfert de puissance entre les nœuds du réseau, qui fournissent la tension et la puissance de référence aux contrôleurs locaux et primaires, même lorsque des perturbations apparaissent. Dans cette partie, nous avons proposé une nouvelle approche pour résoudre les problèmes de flux de puissance (équations non-linéaires) basée sur le théorème du point fixe de l’application contractive. Ceci permet d'utiliser plus d'un slack bus, contrairement à l’approche classique basée sur la méthode de Newton-Raphson. Par ailleurs, le réglage secondaire joue un rôle très important dans les applications pratiques, en particulier lorsque les sources d'énergie renouvelables (variables dans le temps). Dans de tels cas, il est intéressant de considérer des dispositifs de stockage afin d'améliorer la stabilité de tout le système. Il est également possible d'envisager différents types de prévisions (météo, charge, ..) basées sur la gestion des réserves de stockage. Toutes ces caractéristiques ont suggéré l'utilisation d'une approche MPC. Dans ce contexte, plusieurs critères d'optimisation ont été considérés, en particulier la minimisation des pertes de transmission ou des congestions dans le réseau.La tâche principale de réglage tertiaire est de d'atteindre l'optimisation économique de l'ensemble du réseau. Dans cette thèse, nous avons pu maximiser le profit économique du système en agissant sur le marché réel, et en optimisant l'utilisation des périphériques de stockage. Dans le but de mettre en œuvre la philosophie de contrôle hiérarchique présentée dans cette thèse, nous avons construit un banc d'essai expérimental. Cette plate-forme dispose de quatre terminaux reliés entre eux par l'intermédiaire d'un réseau à courant continu, et connectés au réseau principal de courant alternatif. Ce réseau DC peut fonctionner à un maximum de 400 V, et avec une courant maximal de 15 AThis thesis focuses on the hierarchical control for a multi-terminal high voltage direct current (MT-HVDC) grid suitable for the integration of large scale renewable energy sources. The proposed control scheme is composed of 4 layers, from the low local control at the power converters in the time scale of units of ms; through distributed droop control (primary control) applied in several terminals in the scale of unit of seconds; and then to communication based Model Predictive Control (MPC) that assures the load flow and the steady state voltage/power plan for the whole system, manage large scale storage and include weather forecast (secondary control); finally reaching the higher level controller that is mostly based on optimization techniques, where economic aspects are considered in the same time as longer timespan weather forecast (tertiary control).Concerning the converters' level, special emphasis is placed on DC/DC bidirectional converters. In this thesis, three different topologies are studied in depth: two phases dual active bridge (DAB), the three phases DAB, and the use of the Modular Multilevel Converter (MMC) technology as DC/DC converter. For each topology a specific non-linear control is presented and discussed. In addition, the DC/DC converter can provide other important services as its use as a direct current circuit breaker (DC-CB). Several operation strategies are studied for these topologies used as DC-CB.With respect to primary control, which is the responsible to maintain the DC voltage control of the grid, we have studied several control philosophies: master/slave, voltage margin control and droop control. Finally we have chosen to use droop control, among other reasons, because the communication between nodes is not required. Relative to the secondary control, its main goal is to schedule power transfer between the network nodes providing voltage and power references to local and primary controllers, providing steady state response to disturbances and managing power reserves. In this part we have proposed a new approach to solve the power flow problem (non-linear equations) based on the contraction mapping theorem, which gives the possibility to use more than one bus for the power balance (slack bus) instead of the classic approach based on the Newton-Raphson method. Secondary control plays a very important role in practical applications, in particular when including time varying power sources, as renewable ones. In such cases, it is interesting to consider storage devices in order to improve the stability and the efficiency of the whole system. Due to the sample time of secondary control is on the order of minutes, it is also possible to consider different kinds of forecast (weather, load,..) and to achieve additional control objectives, based on managing storage reserves. All these characteristics encourage the use of a model predictive control (MPC) approach to design this task. In this context, several possibilities of optimization objective were considered, like to minimize transmission losses or to avoid power network congestions.The main task of tertiary control is to manage the load flow of the whole HVDC grid in order to achieve economical optimization. This control level provides power references to the secondary controller. In this thesis we were able to maximize the economic profit of the system by acting on the spot market, and by optimizing the use of storage devices. In this level it is again used the MPC approach.With the aim of implementing the hierarchical control philosophy explained in this thesis, we have built an experimental test bench. This platform has 4 terminals interconnected via a DC grid, and connected to the main AC grid through VSC power converters. This DC grid can work at a maximum of 400 V, and with a maximum allowed current of 15 A
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Bhattacharya, Subroto. "Simulation of transient phenomena in high voltage direct-current converter systems." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26959.
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In this thesis models for the simulation of transient phenomena in high voltage direct-current systems are developed. The new converter model is versatile and the solution algorithm is free from numerical oscillations. A new generic inverter control described in this thesis is based on a predictive approach. Steady-state and transient simulations of two-terminal and multi-terminal (i.e., a parallel converter system) high voltage direct-current systems are carried out using the new converter system model. Comparison between the two-terminal transient simulation results and the high voltage direct-current simulator outputs shows good agreement.
An alternating-current/direct-current initialization procedure for the Electromagnetic
Transients Program (EMTP) has been investigated and a novel initialization
algorithm has been suggested in this thesis.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Xie, Chunchao. "Determinism of power supply harmonic impedance by direct methods." Thesis, Staffordshire University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272819.
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Geury, Thomas. "Smart matrix converter-based grid-connected photovoltaic system for mitigating current and voltage-related power quality issues on the low-voltage grid." Doctoral thesis, Universite Libre de Bruxelles, 2017. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/243967.
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The increasing penetration of distributed energy resources, in particular Photovoltaic (PV) production units, and the ever-growing use of power electronics-based equipment has led to specific concern about Power Quality (PQ) in the Low-Voltage (LV) grid. These include high- and low-order current harmonics as well as voltage distortion at the point of common coupling. Solutions to overcome these issues, meeting international grid codes, are being proposed in the context of smart energy management schemes.This work proposes a novel three-phase topology for a PV system with enhanced PQ mitigation functionality, tackling the corresponding control challenges.First, a single-stage current-source inverter PV system with active filtering capability is preferred to the more common two-stage voltage-source inverter topology with additional voltage-step-up converter. The system also guarantees a nearly unitary displacement power factor in the connection to the grid and allows for Maximum Power Point Tracking (MPPT) with direct control of the PV array power. The grid-synchronised dq-axis grid current references are generated for the mitigation of nonlinear load low-order current harmonics, without the need for additional measurements. Active damping is used to minimise grid-side filter losses and reduce high-order harmonics resulting from the converter switching.Results on a 500W laboratory prototype confirm that active damping reduces the switching harmonics in the grid currents and active filtering properly mitigates the low-order current harmonics. The MPPT algorithm works effectively for various irradiance variations. Second, a PV system with a novel Indirect Matrix Converter (IMC)-based unified power quality conditioner topology is developed for enhanced current and voltage compensation capability, with compactness and reliability advantages. PQ issues such as current harmonics, and voltage sags, swells, undervoltage and overvoltage are mitigated by the shunt and series converters, respectively.The more common Space Vector Modulation (SVM) method used in IMCs is developed for this specific topology. In particular, a new shunt converter modulation method is proposed to additionally control the PV array current with zero switching vectors, resulting in a specific switching sequence.A direct sliding mode control method is also studied separately for the shunt and series converters, so that the zero-vector modulation method of the shunt converter can be used, with no sensitive synchronisation of the switching signals; this contrasts with the SVM method. A new dc link voltage modulation method with 12 voltage zones, instead of 6, is proposed to help overcome the limitation in the choice of shunt converter switching vectors due to the positive dc link voltage constraint.Results are obtained for the direct method on a 1 kW laboratory prototype with optimised IMC dc link connection and alternative shunt converter switching transitions to guarantee a positive dc link voltage. Current and voltage compensation capabilities are confirmed by tests in various operating conditions.Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
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Kondo, Takeshi. "Current-voltage characteristics of organic semiconductors interfacial control between organic layers and electrodes /." Diss., Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-05022007-122219/.
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Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2008.Dr. Marder Seth R, Committee Chair ; Dr. Kippelen Bernard, Committee Co-Chair ; Dr. Brďas Jean-Luc E, Committee Member ; Dr. Perry Joseph W, Committee Member ; Dr. Srinivasarao Mohan, Committee Member.
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Suri, Ramaa Saket. "Design of Voltage Boosting Rectifiers for Wireless Power Transfer Systems." Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1505212/.
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This thesis presents a multi-stage rectifier for wireless power transfer in biomedical implant systems. The rectifier is built using Schottky diodes. The design has been simulated in 0.5µm and 130nm CMOS processes. The challenges for a rectifier in a wireless power transfer systems are observed to be the efficiency, output voltage yield, operating frequency range and the minimum input voltage the rectifier can convert. The rectifier outperformed the contemporary works in the mentioned criteria.
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Gannett, Robert Ashley. "Control Strategies for High Power Four-Leg Voltage Source Inverters." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/34251.
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In recent decades there has been a rapidly growing demand for high quality, uninterrupted power. In light of this fact, this study has addressed some of the causes of poor power quality and control strategies to ensure a high performance level in inverter-fed power systems. In particular, specific loading conditions present interesting challenges to inverter-fed, high power systems. No-load, unbalanced loading, and non-linear loading each have unique characteristics that negatively influence the performance of the Voltage Source Inverter (VSI). Ideal, infinitely stiff power systems are uninfluenced by loading conditions; however, realistic systems, with finite output impedances, encounter stability issues, unbalanced phase voltage, and harmonic distortion. Each of the loading conditions is presented in detail with a proposed control strategy in order to ensure superior inverter performance. Simulation results are presented for a 90 kVA, 400 Hz VSI under challenging loading conditions to demonstrate the merits of the proposed control strategies.
Unloaded or lightly loaded conditions can cause instabilities in inverter-fed power systems, because of the lightly damped characteristic of the output filter. An inner current loop is demonstrated to damp the filter poles at light load and therefore enable an increase in the control bandwidth by an order of magnitude. Unbalanced loading causes unequal phase currents, and consequently negative sequence and zero sequence (in four-wire systems) distortion. A proposed control strategy based on synchronous and stationary frame controllers is shown to reduce the phase voltage unbalance from 4.2% to 0.23% for a 100%-100%-85% load imbalance over fundamental positive sequence control alone. Non-linear loads draw harmonic currents, and likewise cause harmonic distortion in power systems. A proposed harmonic control scheme is demonstrated to achieve near steady state errors for the low order harmonics due to non-linear loads. In particular, the THD is reduced from 22.3% to 5.2% for full three-phase diode rectifier loading, and from 11.3% to 1.5% for full balanced single-phase diode rectifier loading, over fundamental control alone.Master of Science
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Lam, Hoi-yee. "Voltage-current trajectory a 2-dimensional approach to understand electrical load signatures /." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B3890861X.
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Mbeutcha, France Gaspari. "A High-Side Wideband Current and Voltage Sensor for Radio-Frequency Power Amplifiers." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/17464/.
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The radio-frequency power amplifier (RF PA) is one of the critical elements within the wireless, as it is expected to provide a suitable output power with high efficiency and linearity. Improving the power efficiency of the RF power amplifier is a key challenge of the modern wireless communications, especially in the presence of wideband modulations signals. In fact, to achieve this goal, various techniques are investigated, including supply voltage modulation (e.g., envelope- tracking). In the supply-modulated Pas employed in modern telecom base stations, it is important to measure the dynamic current drained by the power amplifier and the dynamic voltage at the supply terminal.
This thesis project is focused on the design and realization of a high-side wideband (frequency response from dc up to > 100 MHz) voltage and current sensor suitable for supply-modulated power amplifiers. In order to be used with Gallium Nitride (GaN) PAs, the sensor must be able to withstand dynamic supply voltages up to 80 V and dynamic drain currents up to 2 A. The proposed current sensor is based on a shunt resistor approach, where the voltage drops across the resistor is firstly attenuated, and then amplified by a balanced differential circuit consisting of two cascaded stages. The voltage sensor consists of an operational amplifier configured as a buffer.
The first part of the project, developed at the DEI EDM Lab (UNIBO), was dedicated to the analysis of the sensing architecture, the simulation of the resulting circuit. The design of the board its characterization and board test were realized in at the Warsaw University of Technology in Poland.
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Myhre, Jørgen Chr. "Electrical Power Supply to Offshore Oil Installations by High Voltage Direct Current Transmission." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Information Technology, Mathematics and Electrical Engineering, 2001. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-383.
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This study was initiated to investigate if it could be feasible to supply offshore oil installations in the North Sea with electrical power from land. A prestudy of alternative converter topologies indicated that the most promising solution would be to investigate a conventional system with reduced synchronous compensator rating.
The study starts with a summary of the state of power supply to offshore installations today, and a short review of classical HVDC transmission. It goes on to analyse how a passive network without sources influences the inverter. The transmission, with its current controlled rectifier and large inductance, is simulated as a current source. Under these circumstances the analysis shows that the network frequency has to adapt in order to keep the active and reactive power balance until the controllers are able to react. The concept of firing angle for a thyristor is limited in a system with variable frequency, the actual control parameter is the firing delay time.
Sensitivity analysis showed some astonishing consequences. The frequency rises both by an increase in the active and in the reactive load. The voltage falls by an increase in the active load, but rises by an increase in the inductive load.
Two different control principles for the system of inverter, synchronous compensator and load are defined. The first takes the reference for the firing delay time from the fundamental voltage at the point of common coupling. The second takes the reference for the firing delay time from the simulated EMF of the synchronous compensator. Of these, the second is the more stable and should be chosen as the basis for a possible control system.
Two simulation tools are applied. The first is a quasi-phasor model running on Matlab with Simulink. The other is a time domain model in KREAN. The time domain model is primarily used for the verification of the quasi-phasor model, and shows that quasi-phasors is still a valuable tool for making a quick analysis of the main features when the details of the transients are of less importance.
The study indicates that power supply by HVDC transmission from land to offshore oil installations could be technically feasible, even without the large synchronous compensators normally required. It has been shown that in a network only supplied by an inverter, variations of active and reactive loads have significant influence on both voltage and frequency. Particularly it should be noted that the frequency shows a positive sensitivity to increases in load. This could make the system intrinsically unstable in the case of a frequency dependent load such as motors.
It was not a part of the study to optimize controllers, but even with simple controllers it was possible to keep the frequency within limits given by norms and regulations, but the voltages were dynamically outside the limits, though not very far. These voltage overswings take place in the first few instances after a disturbance, so it takes unrealistically fast controllers to handle them. They are partly due to the model, where the land based rectifier and the DC reactors are simulated by a constant current source, but partly they have to be handled by overdimensioning of the system.
The simulations indicate that it should be technically possible to supply an oil platform with electrical power from land by means of HVDC transmission with small synchronous compensators. Whether this is financially feasible has not been investigated. Neither has it been considered whether the necessary equipment can actually be installed on an oil platform.
Recently both ABB and Siemens have presented solutions for HVDC transmission in the lower and medium power range based on voltage source converters based on IGBTs. Fully controllable voltage source HVDC converters have properties that may be better suited than conventional line commutated current source thyristor inverters, to supply weak or passive networks, such as offshore oil installations, with electrical power. But they also have some disadvantages, and a complete technical and financial comparison must be performed in order to decide about any potential project.
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Bicer, Nazan. "A Current Source Converter Based Statcom For Reactive Power Compensation At Low Voltage." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/2/12612007/index.pdf.
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This research work is devoted to the analysis, design and development of the Current-Source Converter (CSC) based distribution-type Static Synchronous Compensator (D-STATCOM) for low-voltage applications in reactive-power control in order to achieve i) faster transient response in reactive-power control, ii) lower current harmonic distortion, iii) lower power losses and iv) minimum storage elements in comparison with conventional solutions. The developed CSC-D-STATCOM includes a low-pass input filter and a three phase forced-commutated CSC which is composed of six insulated gate bipolar transistors (IGBT) with built-in series diodes. The analysis and the control of the CSC-D-STATCOM are carried out in dq-synchronous reference frame in order to obtain the reference current waveform which is to be generated by switching the IGBTs at 3kHz with the use of space vector modulation.
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Giraneza, Martial. "High voltage direct current (HVDC) in applications for distributed independent power providers (IPP)." Thesis, Cape Peninsula University of Technology, 2013. http://hdl.handle.net/20.500.11838/1077.
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Thesis submitted in fulfillment of the requirements for the degree
Master of Technology: Electrical Engineering
in the Faculty of Engineering
at the Cape Peninsula University of Technology
2013The development of power electronics did remove most of technical limitations that high voltage direct current (HVDC) used to have. HVDC, now, is mostly used for the transmission of bulk power over long distances and for the interconnection of asynchronous grid. Along with the development of the HVDC, the growth of power demand also increased beyond the utilities capacities. Besides the on-going increasing of power demand, the reforms in electricity market have led to the liberalization and the incorporation of Independent power providers in power system operation. Regulations and rules have been established by regulating authority for grid integration of Independent power providers. With the expected increase of penetration level of those new independent power providers, result of economic reason and actual green energy trend, best method of integration of those new power plants are required. In this research HVDC technology, namely VSC-HVDC is used as interface for connecting independent power providers units to the grid. VSC-HVDC has various advantages such as short-circuit contribution and independent control of active and reactive power. VSC-HVDC advantages are used for a safe integration of IPPs and make them participate to grid stabilization. MATLAB/Simulink simulations of different grid connected, through VSC-HVDC system, IPPs technologies models are performed. For each IPP technology model, system model performances are studied and dynamics responses during the disturbance are analyzed in MATLAB/ Simulink program. The simulation results show that the model satisfy the standard imposed by the regulating authority in terms of power quality and grid support. Also the results show the effect of the VSC-HVDC in preventing faults propagation from grid to integrated IPPs units.
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Lam, Hoi-yee, and 林凱儀. "Voltage-current trajectory: a 2-dimensional approach to understand electrical load signatures." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B3890861X.
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Fuentes-Rosado, J. "Test characteristics and operation of surge arrester elements." Thesis, Cardiff University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283894.
Full textAbstract:
This Thesis presents the development of an empirical and simple computer model for a voltage response of a ZnO element The derived model consists of a linear capacitor and atime-varying resistance. The data necessary for the derivation of the model is collected from testing on three ZnO elements with three different linear circuits. The front times of the voltage responses of the ZnO elements range from nanoseconds to submicroseconds. The front times of the current impulses being used to produce the voltage impulses varies from nanoseconds to microseconds. The voltages having nanosecond front times are measured with attenuators and the voltages with sub-microsecond-front time with a capacitor divider. Currents associated with the nanosecond-front-time voltages are measured with a technique founded on transmission line concepts. Currents associated with the submicrosecond-front-time voltages are obtained with a current shunt The response time of the capacitor divider and of the current shunt fall outside the ranges of the ratios of front time to response times specified in the IEC standard. Distortion introduced by the measuring devices into the measured signals is investigated with computer simulation. Conical transmission lines were constructed to test the voltage response of a toroidal ZnO element to the nanosecond-front-time current impulses. Analysis of the voltage response to the current impulses with sub-and-microsecond-front times indicates that at the beginning of the response, of a ZnO element it behaves as an approximately linear capacitor and subsequently as a capacitor in parallel with a timevarying resistance. The turn-on of the resistive behaviour occurs at approximately the first current peak The discrete voltage relating to the first current peak is named here the threshold voltage. This discrete voltage also denotes the tum-off of the resistive behaviour on the wave tail. The values of the apparent capacitances and permittivities of the ZnO elements are obtained. The apparent permittivities of the three ZnO elements are similar. The computed and measured variations of the resistance show good agreement The simulated and computed voltage responses of a ZnO element also show good agreement Atoroidal ZnO element is tested with the nanosecond-front-time current impulses. Analysis of the voltage response and the current-impulse shape by q-v curves and comparison of the measured responses to those of lumped linear capacitors show that a)the response of the ZnO element is capacitive and b) the capacitor characteristic is quasilinear. The simulated and computed voltage responses show good agreement The deviation from linearity originates from both the limited response of the attenuators and mismatches between the conical transmission lines and the section of the coaxial cable of the used current generator. The voltage response of miniature ZnO elements (also tested with the nanosecond-front time current impulses) show resistive behaviour. This Thesis also presents the design, construction and operation of a measuring system based on Rogowski coils. The model used for the analysis of the measuring system is an extended version of an existing model of a Rogowski coil. The model being introduced here can account for the interaction of the Rogowski coil with the remainder of the measuring system. This is applied successfully to the measurement of an impulse current flowing through a ZnO element
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Miwa, Hidekazu. "High-Efficiency Low-Voltage High-Current Power Stage Design Considerations for Fuel Cell Power Conditioning Systems." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/42519.
Full textAbstract:
Fuel cells typically produce low-voltage high-current output because their individual cell voltage is low, and it is nontrivial to balance for a high-voltage stack. In addition, the output voltage of fuel cells varies depending on load conditions. Due to the variable low voltage output, the energy produced by fuel cells typically requires power conditioning systems to transform the unregulated source energy into more useful energy format. When evaluating power conditioning systems, efficiency and reliability are critical. The power conditioning systems should be efficient in order to prevent excess waste of energy. Since loss is dissipated as heat, efficiency directly affects system reliability as well. High temperatures negatively affect system reliability. Components are much more likely to fail at high temperatures. In order to obtain excellent efficiency and system reliability, low-voltage high-current power conditioning systems should be carefully designed.
Low-voltage high-current systems require carefully designed PCB layouts and bus bars. The bus bar and PCB trace lengths should be minimized. Therefore, each needs to be designed with the other in mind. Excessive PCB and bus bar lengths can introduce parasitic inductances and resistances which are detrimental to system performance. In addition, thermal management is critical. High power systems must have sufficient cooling in order to maintain reliable operation.
Many sources of loss exist for converters. For low-voltage high-current systems, conduction loss and switching loss may be significant. Other potential non-trivial sources of loss include magnetic losses, copper losses, contact and termination losses, skin effect losses, snubber losses, capacitor equivalent series resistance (ESR) losses, and body diode related losses. Many of the losses can be avoided by carefully designing the system. Therefore, in order to optimize efficiency, the designer should be aware of which components contribute significant amounts of loss. Loss analysis may be performed in order to determine the various sources of loss. The system efficiency can be improved by optimizing components that contribute the most loss.
This thesis surveys some potential topologies suitable for low-voltage high-current systems. One low-voltage high-current system in particular is analyzed in detail. The system is called the V6, which consists of six phase legs, and is arranged as a three full-bridge phase-shift modulated converter to step-up voltage for distributed generation applications. The V6 converter has current handling requirements of up to 120A. Basic operation and performance is analyzed for the V6 converter. The loss within the V6 converter is modeled and efficiency is estimated. Calculations are compared with experimental results. Efficiency improvement through parasitic loss reduction is proposed by analyzing the losses of the V6 converter. Substantial power savings are confirmed with prototypes and experimental results. Loss analysis is utilized in order to obtain high efficiency with the V6 converter. Considerations for greater current levels of up to 400A are also discussed. The greater current handling requirements create additional system issues. When considering such high current levels, parallel devices or modules are required. Power stage design, layout, and bus bar issues due to the high current nature of the system are discussed.Master of Science
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Nightingale, Wendy Denise. "Electrical characteristics if an identified insect motoneurone cell body : a current- and voltage-clamp." Thesis, University of St Andrews, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329911.
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Jacobs, D. M. (Danver Maxwill). "Voltage control of medium to high power three-phase inverter supply systems." Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52608.
Full textAbstract:
Thesis (MScEng)--University of Stellenbosch, 2001.ENGLISH ABSTRACT: In this thesis a new voltage control method is developed for a three-phase inverter supply system. The inverter supply system consist of a Permanent Magnet Generator, a three-phase rectifier, a three-phase inverter plus LC-filter and a three-phase transformer in series. This system supplies power to a network or to a stand-alone load. The main focus of this thesis is on the control aspects of the inverter and the LC-filter. Different voltage control systems are investigated and compared to each other. From these methods the proposed voltage control method is developed where only the output voltages are measured to establish good voltage control. All these voltage control methods are also simulated with a software package. The proposed voltage control method compares very well with other voltage control methods. The results that are obtained in the simulations are satisfactory. The proposed voltage control method is also implemented in an 8 kW laboratory scale model and, again, very good practical results are obtained. A TMS320F240 nsp controller is used to implement the proposed voltage control method. The controller compensates well for load steps, and these results compare well to an alternative voltage control method, which was also evaluated practically.
AFRIKAANSE OPSOMMING: In hierdie tesis IS 'n nuwe spanningsbeheermetode ontwikkel VIr 'n drie-fase wisselrigter kragtoevoerstelsel. Die wisselrigter kragtoevoerstelsel bestaan uit 'n Permanent Magneet Generator, 'n drie-fase gelykrigter, 'n drie-fase wisselrigter plus Le-filter, en 'n drie-fase transformator in serie. Hierdie stelsel voorsien krag aan 'n netwerk sowel as aan 'n alleenstaande las. Die hooffokus van hierdie tesis is op die beheeraspekte van die wisselrigter en Le-filter. Verskillende spanningsbeheermetodes is deeglik ondersoek en vergelyk met mekaar. Uit hierdie metodes is dan die voorgestelde beheermetode ontwikkel waar slegs die uittreespanning gemeet word om goeie spanningsbeheer te kan doen. Al hierdie spanningsbeheermetodes is dan gesimuleer met 'n sagteware pakket. Die voorgestelde spanningsbeheermetode vergelyk baie goed met die ander spanningsbeheermetodes. Die resultate verky in die simulasies is ook baie bevredigend. Die voorgestelde beheermetode is ook geïmplementeer op 'n 8 kW laboratorium skaalmodel en weereens is baie goeie praktiese resultate verky. 'n TMS320F240 DSP-beheerder is gebruik om die voorgestelde beheermetode mee te implementeer. Die beheerder kompenseer baie goed vir lastrappe en vergelyk ook goed met 'n ander spanningsbeheermetode wat prakties ge-evalueer is.
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Al-Ziayree, Ali Mahdi Lafta. "Contactless, high resolution characterization of current and voltage waveforms within high power communication amplifiers." Thesis, Cardiff University, 2018. http://orca.cf.ac.uk/110309/.
Full textAbstract:
Characterisation of high-power communications-based amplifiers (PAs) has generated many thousands of research papers and much of this work assumes the transistors at the heart of these (PAs) to be a ‘large’ holistic entity. Given that high-power communications-based transistors are made up of multiple, parallel transistors on a single substrate, it is this intermediate scale range, within the periphery of the device, but much larger than the geometrical scale of the epitaxy and the lithography, that requires deeper investigation. Raman-based thermography may add a dimension of spatially varying heat dissipation but ‘lifting the bonnet’ of the transistor and making internal contactless measurements of current and voltage is the only way to fully account for the myriads of parasitic effects that have been observed by countless researchers. To date, however, very little research has been conducted on quantifying the individual spatial voltages within the transistor in order to fully characterise it. Miniaturised contactless current and voltage probes are theorised, designed, characterised and optimised in this thesis to deliver a robust and reliable means of transistor characterisation at these internal spatial dimensions. The contactless voltage probe presented in this work has a spatial resolution four times finer than the previously reported voltage probe, with a useful bandwidth up to 7 GHz and a controllable passive gain up to 20 dB at the desired operating frequency. The pinnacle of this thesis delivers a novel shielded contactless current probe, capable of high-resolution scanning, culminating in a ‘quasi-calibrated’ measurement of the distributed currents within a multi-finger LDMOS transistor operating at high power and high frequency. The spatial resolution of this shielded contactless current probe is 62.5 μm with 22.7 dB average rejection ratio to the electric field, and it has a broad bandwidth up to 9 GHz. To date, this type of contactless current measurement has not been reported elsewhere.
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López, Julià Toni. "Prospects of voltage regulators for next generation computer microprocessors." Doctoral thesis, Universitat Politècnica de Catalunya, 2010. http://hdl.handle.net/10803/77908.
Full textAbstract:
Synchronous buck converter based multiphase architectures are evaluated to
determine whether or not the most widespread voltage regulator topology can
meet the power delivery requirements of next generation computer
microprocessors. According to the prognostications, the load current will rise to
200A along with the decrease of the supply voltage to 0.5V and staggering tight
dynamic and static load line tolerances. In view of these demands, researchers face
serious challenges to bring forth compliant solutions that can further offer
acceptable conversion efficiencies and minimum mainboard area occupancy.
Among the most prominent investigation fronts are those surveying
fundamental technology improvements aiming at making power semiconductor
devices more effective at high switching frequency. The latter is of critical
importance as the increase of the switching frequency is fundamentally recognized
as the way forward to enhance power density conversion. Provided that switching
losses must be kept low to enable the miniaturization of the filter components, one
primary goal is to cope with semiconductor and system integration technologies
enabling fast dynamic operation of ultra-low ON resistance power switches.
This justifies the main focus of this thesis work, centered around a
comprehensive analysis of the MOSFET switching behavior in the synchronous
buck converter.
The MOSFETs dynamic operation, far from being well describable with the
traditional clamped inductive hard-switching mode, is strongly influenced by a
number of frequently ignored linear and nonlinear parasitic elements that must be
taken into account in order to fully predict real switching waveforms, understand
their dynamics, and most importantly, identify and quantify the related
mechanisms leading to heat generation. This will be revealed from in-depth
investigations of the switched converter under fast switching speeds and heavy
load.
Recognizing the key relevance of appropriate modeling tools that support this
task, the second focal point of the thesis aims at developing a number of suitable
models for the switching analysis of power MOSFETs.
Combined with a series of design guidelines and optimization procedures, these
models form the basis of a proposed methodological approach, where numerical
computations replace the usually enormous experimental effort to elucidate the
most effective pathways towards reducing power losses. This gives rise to the
concept referred to as virtual design loop, which is successfully applied to the
development of a new power MOSFET technology offering outstanding dynamic
and static performance characteristics. From a system perspective, the limits of the
power density conversion will be explored for this and other emerging
technologies that promise to open up a new paradigm in power integration
capabilities.
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Tong, Sai-kit. "A computer-aided measurement system for monopolar high-voltage direct-current coronating lines /." [Hong Kong] : University of Hong Kong, 1986. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12321771.
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Hossin, Mohamad Abdalla. "Evaluation of gallium arsenide Schottky Gate Bipolar Transistor for high-voltage power switching applications." Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263129.
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湯世傑 and Sai-kit Tong. "A computer-aided measurement system for monopolar high-voltage direct-current coronating lines." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1986. http://hub.hku.hk/bib/B31207467.
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Yao, Liangbin. "HIGH CURRENT DENSITY LOW VOLTAGE ISOLATED DC-DC CONVERTERSWITH FAST TRANSIENT RESPONSE." Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3205.
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With the rapid development of microprocessor and semiconductor technology, industry continues to update the requirements for power supplies. For telecommunication and computing system applications, power supplies require increasing current level while the supply voltage keeps decreasing. For example, the Intel's CPU core voltage decreased from 2 volt in 1999 to 1 volt in 2005 while the supply current increased from 20A in 1999 to up to 100A in 2005. As a result, low-voltage high-current high efficiency dc-dc converters with high power-density are demanded for state-of-the-art applications and also the future applications. Half-bridge dc-dc converter with current-doubler rectification is regarded as a good topology that is suitable for high-current low-voltage applications. There are three control schemes for half-bridge dc-dc converters and in order to provide a valid unified analog model for optimal compensator design, the analog state-space modeling and small signal modeling are studied in the dissertation and unified state-space and analog small signal model are derived. In addition, the digital control gains a lot of attentions due to its flexibility and re-programmability. In this dissertation, a unified digital small signal model for half-bridge dc-dc converter with current doubler rectifier is also developed and the digital compensator based on the derived model is implemented and verified by the experiments with the TI DSP chip. In addition, although current doubler rectifier is widely used in industry, the key issue is the current sharing between two inductors. The current imbalance is well studied and solved in non-isolated multi-phase buck converters, yet few discusse this issue in the current doubler rectification topology within academia and industry. This dissertation analyze the current sharing issue in comparison with multi-phase buck and one modified current doubler rectifier topology is proposed to achieve passive current sharing. The performance is evaluated with half bridge dc-dc converter; good current sharing is achieved without additional circuitry. Due to increasing demands for high-efficiency high-power-density low-voltage high current topologies for future applications, the thermal management is challenging. Since the secondary-side conduction loss dominates the overall power loss in low-voltage high-current isolated dc-dc converters, a novel current tripler rectification topology is proposed. Theoretical analysis, comparison and experimental results verify that the proposed rectification technique has good thermal management and well-distributed power dissipation, simplified magnetic design and low copper loss for inductors and transformer. That is due to the fact that the load current is better distributed in three inductors and the rms current in transformer windings is reduced. Another challenge in telecommunication and computing applications is fast transient response of the converter to the increasing slew-rate of load current change. For instance, from Intel's roadmap, it can be observed that the current slew rate of the age regulator has dramatically increased from 25A/uS in 1999 to 400A/us in 2005. One of the solutions to achieve fast transient response is secondary-side control technique to eliminate the delay of optocoupler to increase the system bandwidth. Active-clamp half bridge dc-dc converter with secondary-side control is presented and one industry standard 16th prototype is built and tested; good efficiency and transient response are shown in the experimental section. However, one key issue for implementation of secondary-side control is start-up. A new zero-voltage-switching buck-flyback isolated dc-dc converter with synchronous rectification is proposed, and it is only suitable for start-up circuit for secondary-side controlled converter, but also for house-keeping power supplies and standalone power supplies requiring multi-outputs.Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering PhD
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Borzdov, A. V., V. M. Borzdov, D. V. Pozdnyakov, and F. F. Komarov. "Influence of Impact Ionization Process on Current-Voltage Characteristics of Nanoscale Silicon n-Channel MOSFET." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35371.
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The current-voltage characteristics of nanoscale silicon n-channel MOSFET with 50 nm channel length are calculated in the present study. Both the electron and hole transport are simulated by means of the en-semble Monte Carlo method. The importance of electron impact ionization process in the transistor chan-nel for drain biases higher than 1 V is shown.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35371
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Nightingale, Wendy Denise. "Electrical characteristics of an identified insect motoneurone cell body : a current- and voltage-clamp study." Thesis, University of St Andrews, 1989. http://hdl.handle.net/10023/14077.
Full textAbstract:
1. The electrical characteristics of the cell body of an identified excitatory motoneurone (cell 3) from the cockroach (Periplaneta americana) have been studied under current- and voltage-clamp. 2. Under voltage-clamp depolarising command pulses evoked an outward current which increased with the magnitude of the command step up to approximately +100mV, a component of the current developed more slowly and took longer to reach a maximum. With increasing depolarisation the outward current response fell to a lower level before further increasing. This current response gave rise to a characteristic N-shape I-V relationship. The position of the negative conductance region depends on the time current measurements are taken after the onset of the command pulse. 3. Externally applied cadmium (1mM) or manganese ions (5mM) abolished the slowly developing current responsible for the hump in the I-V relationship. These results indicate that calcium ions are required for the activation of this component of the outward current. Verapamil (50?M) also reduced this current component and appeared to be non-specific in reducing another current component. Furthermore, verapamil caused inactivation of the remaining current which was more marked for long duration (500ms) command pulses. 4. Externally applied TEA+ (at concentrations greater than 25mM) blocked the calcium-dependent current and a calcium-independent component. Under current-clamp TEA+ (50mM) unmasked a broad action potential. 5. Externally applied aminopyridines did not enhance excitability under current-clamp. Under voltage-clamp aminopyridines had significant effect in shifting the voltage dependence of the hump in the I-V relationship toward more negative potentials. 6. When holding at -90mV and stepping to more positive potentials there was no indication of an early, fast, transient component similar to IA. If present at all, IA made only a minor contribution to the total outward currents. 7. A double command pulse regime was used to study tail currents whereby a standard pre-pulse (pulse (I)) was immediately followed by a test pulse (pulse (II)) to various command potentials. Tail current measurements were taken during pulse (II). The tail currents showed strong outward rectification and were severely reduced in saline containing cadmium ions (ImM). 8. The tail-current reversal potential was dependent on the pulse (I) magnitude and duration. Preliminary results indicated that increasing the pulse (I) magnitude caused a negative shift in reversal potential. Increasing the pulse (I) duration from 10ms to 50ms caused a positive shift in the reversal potential equivalent to a two-fold increase in extracellular cation concentration. 9. A five-fold increase (from 3.1 to 15mM) in external potassium ion concentration produced a small and variable shift in reversal potential, which did not conform to that predicted by the Nernst equation. A five-fold decrease (from 235 to 47mM) in external chloride ion concentration had little effect on the tail current reversal potential but did cause a slight reduction in the outward currents. Furthermore, the voltage dependency of the hump in the I-V relationship was shifted toward more negative potentials. 10. Action potentials induced by intracellular citrate injection were only slightly enhanced by a four-fold increase (from 9 to 36mM) in external calcium ion concentration. They were reversibly reduced to a graded spike in saline containing verapamil (10?M) and reversibly abolished by manganese ions (40mM), but were relatively unaffected by sodium-free saline. These observations suggest that calcium ions were the major ion carrying the inward current under these conditions. 11. Carbon dioxide-induced action potentials were reversibly reduced to a graded spike in sodium-free or manganese saline (40mM) whereas tetrodotoxin (50nM) irreversibly abolished action potentials for wash period up to 20mins. These observations suggest that both calcium and sodium ions were responsible for the inward current under these conditions. 12. The regenerative component of the axotomy-induced action- potentials was reversibly reduced in sodium-free saline and only partially reduced with some broadening in calcium-free or manganese saline (40mM). Either treatment alone was insufficient to completely abolish or reduce the action potential to a graded spike. A combination of Na-free saline with manganese ions (40mM) caused a more complete block by reducing the regenerative component to a graded spike. These results suggest that sodium ions, and to a lesser extent, calcium ions were responsible for the inward current under these conditions.
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Kalyani, Radha Padma. "A nonlinear optimization approach for UPFC power flow control and voltage security." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.mst.edu/thesis/pdf/Kalyani_completeThesis_09007dcc80438f59.pdf.
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Thesis (Ph. D.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed November 29, 2007) Includes bibliographical references.
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Ntshangase, Zola. "A study of fire-induced air-gap voltage breakdown characteristics under HVDC conditions." Thesis, 2012. http://hdl.handle.net/10413/8300.
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This dissertation investigates the role that is played by high temperatures of air gaps on the
breakdown voltage levels under DC positive and negative polarity applied voltages. Due to
past experience of AC transmission lines tripping as a result of sugar-cane fires that occur
under these lines during cultivation seasons, this study was initiated to investigate this effect
under DC applied voltages.
Results were obtained from laboratory work conducted and these were closely analysed to
understand the behaviour of air gaps under these conditions. A 17mm2 square-cut brass rodrod
electrode configuration was used to carry out these tests at the various air gap
temperatures. These were induced by a gas burner for both the positive and negative
polarities at 200C – 3000C for the 10 mm – 150 mm air gap range and 200C – 1500C for the
200 mm – 500 mm air gap range. Later particles were introduced into the air gap to
determine the subsequent behaviour. These were introduced vertically from the top into an
air gap via a vibrating micro sieve mechanism to regulate the consistency of the introduction
of these particles in the air gap.
A reduction of 55% and 50% was observed on the breakdown voltage under positive and
negative polarity applied voltages respectively from ambient conditions to 3000C.
Additionally the breakdown behaviour of both negative and positive DC was found to be
linear which is similar to the AC case. However, air gaps subjected to positive DC applied
voltages were found to portray an inferior dielectric strength as opposed to the equivalent
negative DC polarity.
The study found that the effect of particles in the air gap is practically negligible and that for
practical purposes, only the temperature effect plays a role due to the reduced air density at
high temperatures.
Empirical models for both the positive and negative DC polarities have been proposed by the
study that incorporate the effect of the temperature in the air gap to enable the determination
or prediction of the breakdown voltage level at various temperatures. These models may be
utilised for DC transmission line design for servitudes in areas that are known to be prone to
fires.Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.
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Shepard, Marshall Howard. "Low voltage power conversion." Master's thesis, 2003. http://hdl.handle.net/1885/148715.
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Chen, Hung-Shing, and 陳鴻興. "High-Voltage, Direct Current electric power transmission systems." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/16143227593366434479.
Full textAbstract:
碩士聖約翰科技大學
自動化及機電整合研究所
96
As result of liberalization on the electrical market, expend the system scale which becomes complicated day after day. Therefore, the network application on innovation and skill improvement is significant. HVDC (High Voltage Direct Current transmission) and FACTS (Flexible AC Transmission Systems) plays the important role on the innovation and skill improvement application. HVDC and FACTS applies in commercial use from 1950s. For AC transmission, HVDC becomes a reliable and cost saving alternative also it provides the operating friendly. This paper is to study the application of HVDC and its future proactive. Integrating HVDC and FACTS of AC system is frequently been applied, because it can simplify the system structure, control the loading, improve the efficacy of system dynamics and increase the reliability of the system. For the interconnection of large sized HVDC and FACTS electric system, it provides the advantages of skills and cost savings, especial obvious under the poor interconnection. Uses of HVDC, the system can connect to the long distance power-stations, such as offshore wind generate electric power. The advantages of the HVDC application is discussed and proved in this paper.
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Zheng, Bo-Ren, and 鄭博任. "Current-Voltage and Capacitance-Voltage Characteristics of Porous Structure and Its Applications on Sensors." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/26452987842140119011.
Full textAbstract:
碩士聖約翰科技大學
電子工程系碩士班
97
In the first, the n-type silicon wafers are used as the raw materials for porous silicon structures which can be served as ethanol sensors. It is found that different porous silicon structure would cause the different sensitivity on ethanol. With the advantages of low cost, easy fabrication, and large surface area density, the porous silicon can be the candidate of sensors. In our experiments, various sizes including the depth, width, and porosity of porous silicon structures cause different sensitivities of porous silicon sensors. To realize the relationship between the structures and their performance, the porous silicon samples are analyzed by SEM、3D Profile、FTIR and I-V/C-V measurements. Besides, a special etching container is designed for double-side porous silicon structure. In the study, the p-type silicon wafers are used as the raw materials. In the first, the porous silicon film is formed on the normal polished side. After that, the anode and cathode are changed during the process, and the porous silicon film is formed on the other side. Such double-side porous silicon samples are also analyzed by photoluminescence spectrometer, SEM, and I-V measurements. Such a design is useful for the double-side fabrication process.
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Yehia, Ali Mustafa Doaa Mokhtar. "Deliverable Power Characteristics in Low-Voltage DC Distribution System Based on Voltage Stability." Thesis, 2011. http://hdl.handle.net/2237/16630.
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