Dissertations / Theses on the topic 'High Voltage Application'
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Wikström, Mats Olof Tobias. "MOS-controlled switches for high-voltage application /." Zürich, 2001. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=14025.
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Mwaniki, Fredrick Mukundi. "High voltage boost DC-Dc converter suitable for variable voltage sources and high power photovoltaic application." Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/37320.
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Important considerations of a photovoltaic (PV) source are achieving a high voltage and drawing currents with very little ripple component from it. Furthermore, the output from such a source is variable depending on irradiation and temperature. In this research, literature review of prior methods employed to boost the output voltage of a PV source is examined and their limitations identified. This research then proposes a multi-phase tapped-coupled inductor boost DC-DC converter that can achieve high voltage boost ratios, without adversely compromising performance, to be used as an interface to a PV source. The proposed converter achieves minimal current and voltage ripple both at the input and output. The suitability of the proposed converter topology for variable input voltage and variable power operation is demonstrated in this dissertation. The proposed converter is also shown to have good performance at high power levels, making it very suitable for high power applications.
Detailed analysis of the proposed converter is done. Advantages of the proposed converter are explained analytically and confirmed through simulations and experimentally. Regulation of the converter output voltage is also explained and implemented using a digital controller. The simulation and experimental results confirm that the proposed converter is suitable for high power as well as variable power, variable voltage applications where high voltage boost ratios are required.Dissertation (MEng)--University of Pretoria, 2013.
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Electrical, Electronic and Computer Engineering
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Dettmer, Hartmut. "MOS controlled power devices for high voltage application /." [S.l.] : [s.n.], 1994. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10825.
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Zhou, Yao. "High voltage DC/DC converter for offshore wind application." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/18749.
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With the increasing interest in offshore wind power, the related technologies, including HVDC networks, are gaining similar levels of attention. For large scale wind farms far from shore, high voltage DC transmission can provide several advantages over traditional high voltage AC transmission. This thesis focuses on DC/DC converters, a core part of the HVDC network, especially for use in the high voltage, high power and offshore wind environment. The thesis examines a wide range of possible DC/DC converter topologies for the application. Different topologies are compared and evaluated in detail for use in a high power situation. Based on these results, three DC/DC converter topologies are selected for more detailed modelling. The simulation processes and results are presented in the thesis, which reveals the limitations and behaviour of the topologies when they are used at the MW level. In addition, the high power semiconductor switching devices are discussed and evaluated for each topology. To assess the suitability of the DC/DC converter topologies in the offshore wind application, the selected converter topologies are also analysed and modelled combined with a PMSG wind turbine. Finally, a down-scaled DC/DC converter prototype is built to verify the analysis and simulation results.
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Loh, Chee Keong Richard Marcus. "Phase shifted bridge converter for a high voltage application." Thesis, University of Edinburgh, 2003. http://hdl.handle.net/1842/12459.
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In airborne applications, the size and weight of equipment are critical parameters. The power supply for an airborne radar needs to have a high output power density while operating with a high efficiency. Conventional Travelling Wave Tube (TWT) radars require a high voltage power supply for operation and is prone to arcing. As the radar is a crucial piece of equipment, its power supply must be designed to withstand such operation. The Phase Shifted Pulse Width Modulation Zero Voltage Switching Full Bridge Converter has been the subject of many papers due to its ability to provide high output powers with high efficiency. As the output inductive/capacitive filters used by the present low voltage, high current, phase shifted converters are unsuitable for high output voltage applications, it is replaced with a capacitive filter, altering the basic operation of the converter. In this thesis the theory and design implementation of the Phase Shifted Bridge with Capacitive Filter (PSBCF) is described. Two auxiliary circuits developed for the conventional phase shifted bridge are analysed and implemented in the new PSBCF. Detailed cycle-by-cycle transient simulations on PSPICE are used to study the converters' behaviour and these are verified with experimental results. An averaged model of the PSBCF running in PSPICE is described and verified using the cycle-by-cycle transient simulations. Finally, the features and limitations of the PSBCF converter and the use of the auxiliary circuits are discussed and evaluated against each other and against the currently used airborne TWT radar power converter to demonstrate that this technology is a viable replacement.
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Mohamad, Azwadi. "Surface fluorinated epoxy resin for high voltage DC application." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/410354/.
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Charge build up under high voltage DC is a significant concern in the transmission system as its presence may distort the local electric field. By chemically treat polymeric insulation via direct fluorination, and plasma enhanced fluorination process, the charge transport characteristics of the material can be modified. In doing so, excellent surface properties similar to those of fluoropolymers can be attained without compromising the bulk properties of the original polymeric insulation. The change in chemical components at the surface of polymeric insulation should lead to a corresponding change in dielectric properties at the surface and consequently may suppress the occurrences of charge build up. In this research, epoxy resin samples with various surface fluorinating conditions were formulated and treated. The samples then were characterised by SEM and EDX analysis, Raman spectroscopy, and DC surface conductivity measurements. To further explain the effects of fluorination treatment, modelling of the electric field and current density distribution had been carried out. Surface potential decay tests from corona discharge, as well as PEA measurements, show that there is a significant change in decay characteristics with the introduction of surface fluorinated layer. The decay mechanisms responsible for the observed phenomena were thoroughly discussed. The effect of moisture absorption on the treated surface was studied and proved to be the limiting factor in the improvement of dielectric properties of fluorination treatment. Finally, surface DC flashover test using a pair of finger electrodes were performed. This research proved that the introduction of the fluorinated surface layer on epoxy resins does play a major role in improving the surface dielectric properties for the use as insulation spacer in high voltage DC GIS systems.
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Werelius, Peter. "Development and application of high voltage dielectric spectroscopy for diagnosis of medium voltage XLPE cables." Doctoral thesis, KTH, Electrical Systems, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3278.
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When polymer power cables were introduced into mediumvoltage applications in the late 1960s, the degradationphenomenon later referred to aswater treeingwas still unknown. However, this changedwithin a relatively short space of time. Just 5-10 years afterthese first polymer applications, faults began to appear thatcould be attributed to the new phenomenon-water treeing. Sincethen, cable manufacturers have been improving their designsgradually, and cables produced today are assumed to have muchlower susceptibility to water trees. However, water treeing isstill assumed to be the most important degradation process inthese applications.
There are huge amounts of polymer cable installations thatare degraded by water trees. Since many of these cables areinstalled in the same grid nets, one cable fault oftengenerates another. If two or more cables fail at the same time,the consequences can be extensive. A non-destructive diagnosticmethod makes it possible to assess cables and take action priorto failures.
This thesis presents the results of research work on thedevelopment of a measurement technique and diagnostic methodfor the assessment of medium voltage XLPE cables in the field.The method used is called high voltage dielectric spectroscopy,and involves the measurement of capacitance and loss as afunction of frequency at high voltages. The method is used in ashort frequency range of approximately one decade in thelow-frequency region (normally from 1 down to 0.1 Hz). Thevoltage levels used initially are all below the service-voltagelevel. If the cable is assessed to be free from water trees, aslightly increased voltage can be used.
Based on dielectric-spectroscopy measurements, specificwater-tree analysis and breakdown tests, a set of measurementprocedures and criteria that take into account differences incable designs has been proposed for the assessment of mediumvoltage XLPE cables. The characteristic responses of XLPEcables (in both non and water-tree-deteriorated cases) make itpossible to separate the cable response from the influence ofaccessories. Field experience shows thatwater-tree-deteriorated cables with relatively low breakdownstrengths can remain in service for many years.
Keywords:dielectric spectroscopy, high voltage,variable frequency, diagnostics, non-destructive diagnostics,cables, medium voltage, polymer, XLPE, water trees, watertreeing
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Motto, Kevin. "Application of High-Power Snubberless Semiconductor Switches in High-Frequency PWM Converters." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/35778.
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For many years, power electronics in the high-power area was performed with extremely slow semiconductor switches. These switches, including the thyristor and the Gate Turn-Off (GTO) thyristor, had the capacity to handle very high voltages and currents but lacked the ability to perform high frequency switching. Low-power converters, such as computer power supplies and low horsepower motor drives, have employed high-frequency switching for years and have benefited from very nice output waveforms, good control dynamic performance, and many other advantages compared to low frequency switching. Recent improvements in high-power semiconductor technology has brought switching performance similar to that of the low-power MOSFETs and IGBTs to the high-power area through the advancement of the IGBT's ratings to create the High Voltage IGBT (HVIGBT) and the development of new GTO-derived devices including the Integrated Gate Commutated Thyristor (IGCT) and the Emitter Turn-Off (ETO) thyristor. These new devices all feature high switching speed and the capability to turn off without the requirement for a turn-off snubber. With these new device technologies the high-power field of power electronics can realize dramatic improvements in the performance of systems for utility applications and motor drives.
However, with these high-speed switches come new issues relating to noise, protection, performance of diodes, and thermal management in high-frequency applications. This thesis addresses the application of these new devices, especially the ETO and the IGCT.
Examples of each device technology (IGBT, IGCT, and ETO) have been characterized in both their switching performance and conduction loss. The tests performed show how these new devices may be applied to various applications. The switching loss, especially related to turn-off, is the dominant factor in the power dissipation of the high-power switches, so knowledge of these characteristics are very important in the system design.
To demonstrate the operation of the ETO, two power converters were constructed. The first was a 100 kW DC/DC converter, which demonstrated the operation of the ETO in a typical building block configuration, the half-bridge. The second system, a 1 MegaVolt-Amp (MVA) three-phase inverter, demonstrated the ETO in an application where the switching frequency and power level were both high. The test results demonstrate the expected characteristics of the high-frequency converters. The development of the ETO's gate driver is described.
During the inverter testing, a new failure mode was found involving a parasitic diode within the ETO. This failure mode was analyzed and solutions were proposed. One of the proposed solutions was implemented and there were no more failures of this type. Another possible failure mode regarding a circulating current in an IGCT-based system is also analyzed.
Soft-switching techniques can help reduce the switching loss in power semiconductor switches. Several topologies were considered for application in the high-power area, and one was selected for further investigation. A prototype Zero Current Transition (ZCT) circuit was developed using an IGCT as the main switch. The turn-off loss was reduced dramatically through the tested ZCT circuit, and the diode recovery was also alleviated.Master of Science
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Bashour, Rami. "High voltage optical fibre sensor for use in wire relay electrical protection systems." Thesis, University of Derby, 2016. http://hdl.handle.net/10545/621343.
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The last few decades have a wide spread use of optical fibre sensors in many applications. Optical fibre sensors have significant benefits over existing conventional sensors such as; high immunity to electromagnetic interference, the ability to transmit signal over long distance at high bandwidth, high resolution, usage in hazardous environments and no need for isolation when working at high voltages. The measurement of high voltages is essential for electrical power systems as it is used as a source of electrical information for Relay Protection Systems (RPS) and load management systems. Electrical Power Systems need to be protected from faults. Faults can range from short circuits, voltage dips, surges, transients etc. The Optical High Voltage sensor developed is based on the principle that the Lead Zirconate Titanate (PZT) electrostriction displacement changes when a voltage is applied to it. The displacement causes the fibre (FBG) which is bonded to the PZT material to have a resultant change in the wavelength. An optical fibre sensor prototype has been developed and evaluated that measures up to 250 V DC. Simulation using ANSYS software has been used to demonstrate the operational capability of the sensor up to 300kV AC. This sensor overcomes some of the challenges of conventional sensors issues like electromagnetic interference, signal transmission, resolution etc. R BASHOUR 2 A novel optical fibre high voltage based on the Kerr effect has been demonstrated. The The Kerr effect was determined using Optsim (R-Soft) software and Maxwell software was used to model an optical Kerr Cell. Maxwell software is an electromagnetic/electric field software used for simulating, analysing, designing 2D and 3D electromagnetic materials and devices. It uses highly accurate Finite Element techniques to solve time varying, static, frequency domain electric and electromagnetic fields. A Relay Protection System on electrical networks was discussed in detail. Keywords: Fibre Bragg Grating, Fibre Optics Sensors, Piezoelectricity, Kerr effect, Relay Protection Systems.
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Asgarifar, Hajarossadat. "Application of high voltage, high frequency pulsed electromagnetic field on cortical bone tissue." Thesis, Queensland University of Technology, 2012. https://eprints.qut.edu.au/53105/1/Hajarossadat_Asgarifar_Thesis.pdf.
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Over the last few decades, electric and electromagnetic fields have achieved important role as stimulator and therapeutic facility in biology and medicine. In particular, low magnitude, low frequency, pulsed electromagnetic field has shown significant positive effect on bone fracture healing and some bone diseases treatment. Nevertheless, to date, little attention has been paid to investigate the possible effect of high frequency, high magnitude pulsed electromagnetic field (pulse power) on functional behaviour and biomechanical properties of bone tissue.
Bone is a dynamic, complex organ, which is made of bone materials (consisting of organic components, inorganic mineral and water) known as extracellular matrix, and bone cells (live part). The cells give the bone the capability of self-repairing by adapting itself to its mechanical environment. The specific bone material composite comprising of collagen matrix reinforced with mineral apatite provides the bone with particular biomechanical properties in an anisotropic, inhomogeneous structure.
This project hypothesized to investigate the possible effect of pulse power signals on cortical bone characteristics through evaluating the fundamental mechanical properties of bone material. A positive buck-boost converter was applied to generate adjustable high voltage, high frequency pulses up to 500 V and 10 kHz.
Bone shows distinctive characteristics in different loading mode. Thus, functional behaviour of bone in response to pulse power excitation were elucidated by using three different conventional mechanical tests applying three-point bending load in elastic region, tensile and compressive loading until failure. Flexural stiffness, tensile and compressive strength, hysteresis and total fracture energy were determined as measure of main bone characteristics. To assess bone structure variation due to pulse power excitation in deeper aspect, a supplementary fractographic study was also conducted using scanning electron micrograph from tensile fracture surfaces.
Furthermore, a non-destructive ultrasonic technique was applied for determination and comparison of bone elasticity before and after pulse power stimulation. This method provided the ability to evaluate the stiffness of millimetre-sized bone samples in three orthogonal directions.
According to the results of non-destructive bending test, the flexural elasticity of cortical bone samples appeared to remain unchanged due to pulse power excitation. Similar results were observed in the bone stiffness for all three orthogonal directions obtained from ultrasonic technique and in the bone stiffness from the compression test. From tensile tests, no significant changes were found in tensile strength and total strain energy absorption of the bone samples exposed to pulse power compared with those of the control samples. Also, the apparent microstructure of the fracture surfaces of PP-exposed samples (including porosity and microcracks diffusion) showed no significant variation due to pulse power stimulation. Nevertheless, the compressive strength and toughness of millimetre-sized samples appeared to increase when the samples were exposed to 66 hours high power pulsed electromagnetic field through screws with small contact cross-section (increasing the pulsed electric field intensity) compare to the control samples. This can show the different load-bearing characteristics of cortical bone tissue in response to pulse power excitation and effectiveness of this type of stimulation on smaller-sized samples.
These overall results may address that although, the pulse power stimulation can influence the arrangement or the quality of the collagen network causing the bone strength and toughness augmentation, it apparently did not affect the mineral phase of the cortical bone material. The results also confirmed that the indirect application of high power pulsed electromagnetic field at 500 V and 10 kHz through capacitive coupling method, was athermal and did not damage the bone tissue construction.
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Gean, Richard T. "Comparison of PWM and resonant technologies in a high voltage DC application." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/42080.
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High voltage transformers inherently contain undesirable parasitic reactances. A resonant circuit formed by the leakage inductance and parasitic reflected capacitance, makes various resonant technologies practical for high voltage dc applications. The components of a typical high voltage power stage will be investigated in order to identify these parasitics and determine their influence on converter operation. Proto-type high voltage converters will be designed and built using PWM and quasi-resonant techniques and experimental results will be given.
Dc analysis will be performed for the PWM and the quasi-resonant designs in order to obtain insight into the actual operation of the two converters. The design of the two proto-type converters will be reviewed and design guidelines will be established.
Master of Science
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Ivanenko, Yevhen. "Estimation of electromagnetic material properties with application to high-voltage power cables." Licentiate thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-64265.
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Efficient design of high-voltage power cables is important to achieve an economical delivery of electric power from wind farms and power plants over the very long distances as well as the overseas electric power. The main focus of this thesis is the investigation of electromagnetic losses in components of high-voltage power cables. The objective of the ongoing research is to develop the theory and optimization techniques as tools to make material choices and geometry designs to minimize the high-frequency attenuation and dispersion for HVDC power cables and the power losses associated with HVAC cables. Physical limitations, dispersion relationships and the application of sum rules as well as convex optimization will be investigated to obtain adequate physical insight and a priori modeling information for these problems. For HVAC power cables, the objectives are addressed by performing measurements and estimation of complex valued permeability of cable armour steel in Papers I and II. Efficient analytical solutions for the electromagnetic field generated by helical structures with applications for HVAC power cables have been obtained in Paper III. For HVDC power cables, estimation of insulation characteristics from dielectric spectroscopy data using Herglotz functions, convex optimization and B-splines, has been investigated in Papers V and VI. The unique solution requirements in waveguide problems have been reviewed in Paper IV.
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Joorabian, M. "Application of artificial intelligence for accurate fault location on transmission systems." Thesis, University of Bath, 1996. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336234.
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Ye, Hanyu [Verfasser]. "Application of Non-Linear Microvaristor-Filled Materials in High-Voltage Devices and Algorithmic Optimization of High-Voltage Simulations Based on Surrogate Models / Hanyu Ye." Wuppertal : Universitätsbibliothek Wuppertal, 2015. http://d-nb.info/1071414860/34.
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Fice, Martyn John. "The application of high-voltage electron lithography to the fabrication of semiconductor lasers." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293002.
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Mohd, Noor Mohd Junaizee. "Application of knowledge-based fuzzy inference system on high voltage transmission line maintenance." Thesis, Queensland University of Technology, 2004. https://eprints.qut.edu.au/16050/1/Mohd_Junaizee_Mohd_Noor_Thesis.pdf.
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A majority of utilities conduct maintenance of transmission line components based on the results of routine visual inspection. The inspection is normally done by inspectors who detect defects by visually checking transmission line components either from the air (in helicopters), from the ground (by using high-powered binoculars) or from the top of the structure (by climbing the structure).
The main problems with visual inspection of transmission lines are that the determination of the defects varies depending on the inspectors' knowledge and experience and that the defects are often reported qualitatively using vague and linguistic terms such as "medium crack", "heavy rust", "small deflection". As a result of these drawbacks, there is a large variance and inconsistency in defect reporting (which, in time, makes it difficult for the utility to monitor the condition of the components) leading to ineffective or wrong maintenance decisions. The use of inspection guides has not been able to fully address these uncertainties.
This thesis reports on the application of a visual inspection methodology that is aimed at addressing the above-mentioned problems. A knowledge-based Fuzzy Inference System (FIS) is designed using Matlab's Fuzzy Logic Toolbox as part of the methodology and its application is demonstrated on utility visual inspection practice of porcelain cap and pin insulators. The FIS consists of expert-specified input membership functions (representing various insulator defect levels), output membership functions (indicating the overall conditions of the insulator) and IF-THEN rules. Consistency in the inspection results is achieved because the condition of the insulator is inferred using the same knowledge-base in the FIS rather than by individual inspectors. The output of the FIS is also used in a mathematical model that is developed to suggest appropriate component replacement date.
It is hoped that the methodology that is introduced in this research will help utilities achieve better maintenance management of transmission line assets.
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Mohd, Noor Mohd Junaizee. "Application of knowledge-based fuzzy inference system on high voltage transmission line maintenance." Queensland University of Technology, 2004. http://eprints.qut.edu.au/16050/.
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A majority of utilities conduct maintenance of transmission line components based on the results of routine visual inspection. The inspection is normally done by inspectors who detect defects by visually checking transmission line components either from the air (in helicopters), from the ground (by using high-powered binoculars) or from the top of the structure (by climbing the structure).
The main problems with visual inspection of transmission lines are that the determination of the defects varies depending on the inspectors' knowledge and experience and that the defects are often reported qualitatively using vague and linguistic terms such as "medium crack", "heavy rust", "small deflection". As a result of these drawbacks, there is a large variance and inconsistency in defect reporting (which, in time, makes it difficult for the utility to monitor the condition of the components) leading to ineffective or wrong maintenance decisions. The use of inspection guides has not been able to fully address these uncertainties.
This thesis reports on the application of a visual inspection methodology that is aimed at addressing the above-mentioned problems. A knowledge-based Fuzzy Inference System (FIS) is designed using Matlab's Fuzzy Logic Toolbox as part of the methodology and its application is demonstrated on utility visual inspection practice of porcelain cap and pin insulators. The FIS consists of expert-specified input membership functions (representing various insulator defect levels), output membership functions (indicating the overall conditions of the insulator) and IF-THEN rules. Consistency in the inspection results is achieved because the condition of the insulator is inferred using the same knowledge-base in the FIS rather than by individual inspectors. The output of the FIS is also used in a mathematical model that is developed to suggest appropriate component replacement date.
It is hoped that the methodology that is introduced in this research will help utilities achieve better maintenance management of transmission line assets.
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Kawano, Kayoko. "Application of the ultra high resolution, low voltage scanning electron microscopy in the materials science." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/application-of-the-ultra-high-resolution-low-voltage-scanning-electron-microscopy-in-the-materials-science(341c7955-1da7-49be-9dd3-a3f3248bae05).html.
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The efficiency of low voltage scanning electron microscopy, which presents near-surface information, has been well known for a long time. However, it is not widely known that the high resolution capability can only be achieved when the surface reveals the original characteristics of the materials without any deterioration due contamination. Therefore, initial attention in this study is directed at clarifying the efficient use of the ultra high resolution, low voltage SEM (UHRLV SEM), (Ultra55, Zeiss). The SEM images and the selected electrons for detection, and damage that occurs through UHRVL SEM observation are also researched. Subsequently, the most efficient specimen preparation technique, which is appropriate for the characteristics of the individual materials, is investigated for galvanized steel, ultrasonically welded alloys of Al6111 and AZ31 alloy, Ti6Al4V alloy honeycomb structure and a ceramic sensor. The outcomes of appropriate specimen preparation technique and use of the extremely Low-Voltage below 2.0 kV, are presented in the results section. The study also presented the challenge of improving the low compositional contrast for the dissimilar materials of aluminium and magnesium, and to reduce charging effects in an insulating material comprising a ceramic sensor. As an application of the surface prepared by the process in this study, 3D tomography is also introduced.
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Lee-Davey, Jon. "Application of machine olfaction principles for the detection of high voltage transformer oil degradation." Thesis, Cranfield University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405216.
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Zhang, Lanhua. "Derivation of Parabolic Current Control with High Precision, Fast Convergence and Extended Voltage Control Application." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/73319.
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Current control is an important topic in modern power electronics system. For voltage source inverters, current control loop ensures the waveform quality at steady state and the fast response at transient state. To improve the current control performance, quite a few nonlinear control strategies have been presented and one well-known strategy is the hysteresis current control. It achieves fast response without stability issue and it has high control precision. However, for voltage source inverter applications, hysteresis current control has a wide switching frequency range, which introduces additional switching loss and impacts the design of harmonic filter. Other nonlinear current control strategies include one-cycle control, non-linear carrier control, peak current control, charge control, and so on. However, these control strategies are just suitable for specific topologies and it cannot be directly used by voltage source inverters.
The recently proposed parabolic current control solves the frequency variation problem of hysteresis current control by employing a pair of parabolic carriers as the control band. By the use of parabolic current control, approximate-constant switching frequency can be achieved. Due to the cycle-by-cycle control structure, it inherently has fast response speed and high precision. These advantages make it suitable for voltage source inverters, including stand-alone inverters, grid connected inverters, active power filters, and power factor correction applications.
However, parabolic current control has some limitations, such as dead-time effects, only working as bipolar PWM, complex hardware implementation, non-ideal converging speed. These problems are respectively solved in this dissertation and solutions include dead-time compensation, the implementation on dual-carrier unipolar PWM, sensorless parabolic current control, single-step current control. With the proposed dead-time compensation strategy, current control precision is improved and stable duty-cycle range are extended. Dual-carrier PWM implementation of parabolic current control has smaller harmonic filter size and lower power loss. Sensorless parabolic current control decreases the cost of system and enhances the noise immunity capability. Single-step current control pushes the convergence speed to one switching operation with simple implementation. High switching frequency is allowed and power density can be improved. Detailed analysis, motivation and experimental verification of all these innovations are covered in this dissertation.
In addition, the duality phenomenon exists in electrical circuits, such as Thevenin's theorem and Norton's theorem, capacitance and inductance. These associated pairs are called duals. The dual of parabolic current control is derived and named parabolic voltage control. Parabolic voltage control solves the audible noise problem of burst mode power converters and maintains high efficiency in the designed boost converter.Ph. D.
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van, der Wielen Klaas Peter. "Application of high voltage breakage to a range of rock types of varying physical properties." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/14522.
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High voltage breakage is a relatively novel comminution technology that uses highly energetic electrical discharges to induce electrical breakdown in rocks. Advantages of the technology in terms of weakening of rocks to ease comminution, as well as improved liberation compared to mechanical fragmentation methods have been demonstrated. However, a detailed understanding of the fragmentation mechanism and its selectivity, as well as how to optimise the process in terms of efficiency and treatment outcomes was still lacking prior to this thesis. The focus of this study was on how process variables and rock properties interact with high voltage breakage to enable more tailored treatment depending on the desired processing result. Twenty different rock types were extensively characterised in terms of geomechanical, mineralogical and electrical properties and treated at different voltages, number of pulses and discharges, electrode gaps and pulse rates. The resulting particle size distribution was investigated in detail, as well as liberation and weakening of selected rock types. In addition, process mineralogical aspects of the treatment were investigated using QEMSCAN® and a scanning electron microscope. Data in this thesis suggest total spark energy input is the main variable determining fragmentation and liberation outcomes of high voltage treatment. Some materials were found to exhibit a threshold voltage below which less fragmentation than expected occurred, but the main controlling factor for spark energy input is the number of discharges applied to a sample. The process efficiency was found to be strongly dependent on the discharge ratio, but also exhibited a strong rock-specific aspect. In general, low energy inputs and process water conductivity combined with a high voltage gradient and pulse rate were found to be most conducive to efficient high voltage processing. Based on fragmentation and weakening results, as well as liberation and process efficiency it is suggested that treatments in the 1 – 5 kWh t 1 range are most suitable for weakening and liberation applications of the technology. Voltages above 140 kV should be sufficient for most purposes, but this depends on the minimum voltage gradient required to reliably develop discharges in a rock type. Furthermore, feed sizes above 14 mm were found to be more suited to high voltage breakage, which is likely the result of the number of discharges available relative to the number of particles being treated. The voltage of a discharge dictates how many discharges are required to achieve a given energy input, and therefore the exact voltage chosen for a high voltage treatment is a function of feed size as well as efficiency and fragmentation considerations. The evolution of P80 of a high voltage treatment product with energy can be estimated with reasonable accuracy from a relationship incorporating porosity and acoustic impedance. Additionally, the decrease of the mass percentage of feed size material after a given energy input was found to be strongly correlated to a function including tensile strength and relative bulk permittivity. Other rock properties that were found to correlate significantly to high voltage breakage include mica and quartz content. Based on correlations between high voltage breakage indicators, tensile strength and acoustic impedance, as well as imaging of the alteration left by several plasma streamers it is concluded that shock waves are the dominant fragmentation mechanism, and that fragmentation occurs predominantly in a tensile stress regime. There is evidence that the selective fragmentation observed during high voltage breakage is a result of both fracturing along grain boundaries (inter-granular fragmentation) and preferential fracturing of certain mineral phases (intra-granular fragmentation). Intra-granular breakage behaviour is clearly evident from some of the data presented in this thesis. Quartz seems to respond strongly to high voltage treatment-induced stresses, which may be favourable from a process mineralogical perspective. Direct imaging of fractures has also yielded evidence for inter-granular selective fracturing, and strong enrichment of sulphides after treatment at low energy inputs also indicates selective, inter-granular breakage. In addition to the selective fragmentation there is also a selective component to the electrical efficiency of the process. Consequently, the selective nature of high voltage breakage is a feature that recurs in several aspects of the technology.
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Davari, Pooya. "High frequency high power converters for industrial applications." Thesis, Queensland University of Technology, 2013. https://eprints.qut.edu.au/62896/1/Pooya_Davari_Thesis.pdf.
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The main contribution of this project was to investigate power electronics technology in designing and developing high frequency high power converters for industrial applications. Therefore, the research was conducted at two levels; first at system level which mainly encapsulated the circuit topology and control scheme and second at application level which involves with real-world applications. Pursuing these objectives, varied topologies have been developed and proposed within this research. The main aim was to resolving solid-state switches limited power rating and operating speed while increasing the system flexibility considering the application characteristics. The developed new power converter configurations were applied to pulsed power and high power ultrasound applications for experimental validation.
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Yeh, Chih-Shen. "Synchronous-Conduction-Mode Tapped-Inductor Buck Converter for Low-Power, High-Density Application." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/81722.
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General-purpose step-down converter is essential in electronic system for processing energy from high-voltage rail to low-voltage circuits. The applications can be found at the auxiliary supplies in automobile, industrial and communication systems. Buck converter is a common circuit topology to fulfill step-down conversion, especially in low-power application since it is well-studied and straightforward. However, it suffers from low duty cycle under high step-down condition, and typically operates in continuous conduction mode (CCM) that generates large switching loss. On the other hand, as an extension of the buck converter, tapped-inductor (TI) buck converter has larger duty cycle while maintaining the structural simplicity. Therefore, the main objective of this thesis is to explore the potential of TI buck converter as a wide conversion range, high power density and high efficiency topology for low power application. To achieve high efficiency at switching frequency of MHz-level, synchronous conduction mode (SCM) is applied for turn-on losses elimination.
The operation principle and power stage design of SCM TI buck is first introduced. The design of high switching frequency coupled inductor is emphasized since its size plays a critical role in power density. Loss breakdown is also provided to perform a comprehensive topological study. Secondly, detailed zero-voltage-switching (ZVS) condition of SCM TI buck is derived so that the converter does not experience redundant circulating energy. The experimental results of 15-W SCM TI buck converter prototypes are provided with 90.7% of peak power stage efficiency. The size of coupled inductor is down to 116 mm3. To enhance light-load efficiency, a variable frequency control scheme based on derived ZVS conditions is implemented with the switching frequency ranging from 2 MHz to 2.9 MHz.Master of Science
General-purpose step-down converter is essential in electronic system for processing energy from high-voltage rail to low-voltage circuits. The applications can be found at the auxiliary supplies in automobile, industrial and communication systems. Typically, the ultimate goals of general-purpose step-down converter are versatility, high efficiency and compact size. Recently, tapped-inductor (TI) buck converter is studied since it could overcome the drawback of commonly used buck converter under high step-down conversion. Therefore, the potential of TI buck converter as a general-purpose step-down converter candidate is explored in this thesis, including control method, hardware design, etc. The thesis verifies that TI buck converter could have compact size while remaining efficient and adaptable.
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Reynes, Hugo. "Conception d'un module électronique de puissance pour application haute tension." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI035.
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Satisfaire les besoins en énergie de manière responsable est possible grâce aux énergies renouvelables, notamment éoliennes et solaires. Cependant ces centres de captation d’énergie sont éloignés dans zones de consommation. Le transport de l’énergie via des réseaux HVDC (haute tension courant continu) permet un rendement et une flexibilité avantageuse face au transport HVAC (haute tension courant alternatif). Ceci est rendu possible grâce aux convertisseurs utilisant l’électronique de puissance. Les récents développements sur les semi-conducteurs à large bande interdite, plus particulièrement le carbure de silicium (SiC) offrent la possibilité de concevoir ces convertisseurs plus simples, utilisant des briques technologiques de plus fort calibre (≤ 10 kV). Cependant le packaging, essentiel à leur bon fonctionnement, ne suit pas ces évolutions. Dans cette thèse, nous explorons les technologies actuelles ainsi que les limites physique et normatives liées au packaging haute tension. Des solutions innovantes sont proposées pour concevoir un module de puissance haute tension, impactant que faiblement les paramètres connexes (résistance thermique, isolation électrique et paramètres environnementaux). Les éléments identifiés comme problématiques sont traités individuellement. La problématique des décharges partielles sur les substrats céramiques métallisés est développée et une solution se basant sur les paramètres géométriques a été testée. Le boitier standard type XHP-3 a été étudié et une solution permettant de le faire fonctionner à 10 kV à fort degré de pollution a été développéeThe supply of carbon-free energy is possible with renewable energy. However, windfarms and solar power plants are geographically away from the distribution points. Transporting the energy using the HVDC (High Voltage Direct Current) technology allow for a better yield along the distance and result in a cost effective approach compared to HVAC (High Voltage Alternative Current) lines. Thus, there is a need of high voltage power converters using power electronics. Recent development on wide bandgap semiconductors, especially silicon carbide (SiC) allow a higher blocking voltage (around 10 kV) that would simplify the design of such power electronic converters. On the other hand, the development on packaging technologies needs to follow this trend. In this thesis, an exploration of technological and normative limitation has been done for a high voltage power module design. The main hot spot are clearly identified and innovative solutions are studied to provide a proper response with a low impact on parasitic parameters. Partial Discharges (PD) on ceramic substrates is analyzed and a solution of a high Partial Discharge Inception Voltage (PDIV) is given based on geometrical parameters. The XHP-3 like power modules are studied and a solution allowing a use under 10 kV at a high pollution degree (PD3) is given
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Ackermann, Roland. "Propagation of terawatt-femtosecond laser pulses and its application to the triggering and guiding of high-voltage discharges." Phd thesis, Université Claude Bernard - Lyon I, 2006. http://tel.archives-ouvertes.fr/tel-00133125.
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La propagation d'une impulsion térawatt ultra-brµeve dans l'atmosphère peut s'accompagner du phénomène de filamentation. La lumière se trouve alors auto-guidée dans des plasmas appelés filaments dont le diamètre est de l'ordre de 100 µm et la longueur peut s'étendre jusqu'à quelques centaines de mètres. De plus, le spectre initial de l'impulsion est considérablement élargi. Ces propriétés ouvrent la possibilité d'améliorer la technique LIDAR et de contrôler la foudre. Nous avons montré que les filaments survivent à la propagation dans une turbulence forte et peuvent se développer sous une pression atmosphérique réduite et sous la pluie. Pour la première fois, la lumière blanche genérée par une impulsion ultra-brève, multi-térawatt a été détectée à une altitude de 20 km.En collaberation avec des installations haute-tension, nous avons déterminé la durée de vie du plasma du filament et la longueur sur laquelle il est possible de guider des décharges électriques. Nous avons pu augmenter l'efficacité de déclenchement avec une configuration à double impulsion. Enfin, nous avons montré que le déclenchement et le guidage sont possibles sous une pluie artificielle.
Ces résultats se sont révélés très encourageants en vue d'expériences LIDAR à lumière blanche et du contrôle de la foudre.
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Basar, Joseph James. "Improvement of Ground-Fault Relaying Selectivity through the Application of Directional Relays to High-Voltage Longwall Mining Systems." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/9888.
Full textAbstract:
The continuing trend toward larger longwall mining systems has resulted in the utilization of higher system voltages. The increase in system voltage levels has caused the industry to face complexities not experienced with the lower-voltage systems. One such complexity arises from the larger system capacitance that results from the outby configuration commonly used on 4,160-V longwall power systems. Simulations show that during a line-to-ground fault, the larger system capacitance can cause a situation where the ground current sensed by the ground-fault relays in unfaulted circuits is greater than the mandated ground-fault relay pick-up setting. Simulations show that ground-fault relaying selectivity is potentially lost as a result of this situation. Two alternatives were identified which could improve ground-fault relaying selectivity. They are: the application of a directional relaying scheme and increasing the ground-fault relay pick-up setting. It was determined that directional relays have an application to high-voltage longwall power systems as the ground current sensed by the relay in the unfaulted circuits is out of phase with the ground-fault current sensed by the relay in the faulted circuit. Furthermore, it was determined that raising the ground-fault relay pick-up setting by a factor of eight would also improve ground-fault relaying selectivity. A safety analysis considering the potential for electrocution and the power dissipated by the maximum fault resistance showed that increasing the pick-up setting by a factor of eight would have no detriment to safety. Therefore, either method would improve ground-fault relaying selectivity on high-voltage longwall mining systems, yet because of the escalating size of longwall systems, a directional relaying scheme is a longer term solution.Master of Science
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El-Gamal, Mourad. "Generalized log-domain integrator structure & its application to the synthesis of high-frequency and low-voltage log-domain filters." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0006/NQ44420.pdf.
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Messali, Amir. "Contribution to Rotor Position and Speed Estimation for Synchronous Machine Drive Using High Frequency Voltage Injection : Application to EV/HEV Powertrains." Thesis, Ecole centrale de Nantes, 2019. http://www.theses.fr/2019ECDN0048.
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Cette thèse s’inscrit dans le cadre de la chaire Renault/Centrale Nantes sur l’amélioration des performances des véhicules électriques (EV/HEV). Elle est dédiée à la problématique de l’estimation de la position/vitesse des moteurs synchrones à aimants permanents (MSAP) sans capteur mécanique, en utilisant les techniques d’injection de signaux haute fréquence (HF) sur toute la plage de vitesse des MSAP. Dans ce cadre, plusieurs contributions ont été proposées dans les parties de démodulation/traitement du signal et d’algorithmes de poursuite des techniques d’injection HF, afin d’améliorer l’estimation de la position/vitesse des MSAP par rapport aux méthodes existantes. Dans la partie démodulation/traitement du signal des techniques d’injection HF, les contributions ont consisté à proposer des solutions originales permettant de réduire les effets de filtrage dans la chaine d’estimation et de rendre cette dernière indépendante des paramètres (électriques) de la machine. Dans la partie poursuite, les contributions portent essentiellement sur l’exploitation de la fonction signe de l’erreur de position (à la place de l’erreur de position) comme information de mesure, pour estimer la position, la vitesse et l’accélération des MSAP sans capteurs mécaniques avec des observateurs par modes glissants d’ordre 1 (classiques, étapes par étapes et adaptatifs). Les contributions proposées dans les deux parties ont pour avantages d’une part, de robustifier la chaine d’estimation en la rendant indépendante des paramètres électriques et mécaniques. Et d’autre part, d’améliorer la précision et les performances de la chaine d’estimation, et par conséquent du contrôle des MSAP sans capteurs mécaniques, dans les phases transitoires et en régimes permanents avec une méthode de réglage aisée. Les méthodes d’estimation développées ont été testées en simulation et en expérimentation sur un banc d’essai de machines électriques. Les résultats obtenus ont permis de mettre en évidence les performances de ces méthodes en terme de suivi de trajectoire et de robustesse sur toute la plage de fonctionnement des MSAP sans capteurs mécaniquesThis thesis is part of the Renault / Centrale Nantes Chair on improving the performance of electric vehicles (EV / HEV). It is dedicated to the problem of estimating the position / speed of self-sensing permanent magnet synchronous motors (PMSM) without mechanical sensors, using high frequency (HF) signal injection techniques over the full speed range of PMSM. In this context, several contributions have been proposed in the demodulation / signal processing and tracking algorithms parts of HF injection techniques, in order to improve the estimation of the position / speed of the MSAP compared to the existing methods. In the demodulation / signal processing part of the HF injection techniques, the contributions consisted of proposing original solutions making it possible to reduce the filtering effects in the estimation chain and to make the latter independent of the electrical machine parameters. In the tracking part, the contributions mainly concern the use of the function sign of the position error (instead of the position error) as measurement information, to estimate the position, the speed and the acceleration of self-sensing PMSM with firstorder sliding mode observers (conventional, step-by-step and adaptive). The contributions proposed in both parts have the advantages of robustifying the estimation chain by making it independent of electrical and mechanical parameters on the one hand. On the other hand, they allow improving the accuracy and performance of the estimation chain, and therefore the control of self-sensing PMSM, in transient and steady-state phases with an easy tuning method. The estimation methods developed were tested in simulation and experimentation on a test bench of electrical machines. The results obtained made it possible to highlight the performances of these methods in terms of trajectory tracking and robustness over the entire operating range of PMSM self-sensing control
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Bonkarev, Maxim [Verfasser], and Harald [Akademischer Betreuer] Schwarz. "Concept analysis for High-Voltage Direct-Current circuit breakers for application in a network of HVDC transmission / Maxim Bonkarev ; Betreuer: Harald Schwarz." Cottbus : BTU Cottbus - Senftenberg, 2015. http://d-nb.info/1114283959/34.
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GALLESI, FEDERICO. "Investigation, Experimental Development, and Field Application of Non-Invasive Sensors for Partial Discharge Measurement." Doctoral thesis, Università degli studi di Genova, 2022. http://hdl.handle.net/11567/1082296.
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Electrical insulating systems represent one of the weakest elements of the entire electrical equipment. In fact, the lifetime of any electrical device depends on the capability of its insulation to last in time. In general, all organic materials, and in particular all dielectrics, are subjected to ageing. The ageing process is caused by different stresses: thermal, electrical, mechanical and environmental. By focusing on the electrical stress, it is possible to state that it is fundamentally characterized by two phenomena: the presence of an electric field and/or the presence of partial discharges (PDs), a phenomenon in which the interelectrode zone is partially short-circuited causing degradation of the material. It is clear, therefore, how partial discharges are both the symptom and the cause of the deterioration of the insulating materials. Thus, the measurement of this phenomenon leads to obtain an “image” of the status of the insulating system allowing to perform a predictive diagnostic by an expert user or by sophisticate artificial intelligence algorithms. These diagnostic techniques lead to reduce the maintenance costs since they allow to perform a condition-based maintenance that is carried out only when this is necessary, according to the real state of the component.
To measure the partial discharge activity there are different methods, but it is possible to classify them into two groups: electrical detection methods and non-electrical detection methods. If the electrical methods typically need invasive procedures to perform the partial discharge measurement, the non-electrical ones, on the contrary, can be implemented on the electrical component without any change (non-invasive) in the normal operating of the equipment.
The focus of this research activity is to study, develop and optimize prototypes, test them in laboratory and in real applications of different non-invasive sensors in order to measure partial discharges. Two kind of sensors are analysed: Transient Earth Voltage Sensors and High Frequency Current Transformers ones.
Transient Earth Voltage Sensors are based on the homonymous operating principle, and they can be used when the electrical apparatus is placed inside a metal box like switchgears or gas insulated systems. Starting from a first investigation on the effect of the geometrical dimensions of different sensors prototype in order to maximize the signal output, a first preliminary on-field test campaign is performed on an industrial air insulated medium voltage switchgear. Then, the entire partial discharge measurement system configuration, based on a definitive version of TEV sensor, is optimized and tested on the industrial test set-up, by comparing the obtained PD pattern with those collected from an IEC 60270 standard compliant measurement system. The results suggest how the non-invasive PD measurement system provides information comparable to those collected by the standard-compliant one.
The High Frequency Current Transformer Sensors are studied and optimized during an experimental laboratory activity where different magnetic core material and different sensor configurations are tested. The results allow to implement the HFCT sensor on an optimized PD measurement system introduced to perform a research investigation on the phenomenon of electrical treeing on HVDC cable insulation, carried out during an exchange program at the RWTH Aachen University in Germany. The aim of this investigation is to understand the behaviour of the electrical treeing with different voltage frequencies and amplitudes during long-term tests since some preliminary tests give unexpected results. In fact, it is generally accepted that increasing the frequency leads to an accelerated ageing process, mainly due to partial discharge activity, and therefore, to a reduced time to breakdown. The collected results show that increasing the applied voltage frequency, the time to breakdown increases since the electrical treeing shape changes. During this analysis, PD measurement is carried out in order to monitor the electrical treeing evolution during the degradation process by adopting the optimized HFCT-based measurement system.
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Moreau, Nicolas. "Decharge nanoseconde dans l'air et en melange air / propane. Application au declenchement de combustion." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00633260.
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Cette étude a pour objet les décharges haute-tension nanoseconde dans l'air à des pressions supérieures ou égale à la pression atmosphérique, en géométrie pointe-plan, et leur application au déclenchement de combustion en mélange air/propane. Ces décharges fortement hors-équilibres sont susceptibles de former une concentration significative d'espèces réactives et nous analysons leur capacité à allumer un mélange combustible. Le générateur conçu est capable de fournir une impulsion de tension carrée de 40 à 80 kV avec un front de montée raide de 3 ns. A la pression atmosphérique, nous observons un type de décharge peu commun dans les précédentes études expérimentales de décharges couronnes : la décharge diffuse. On retrouve une décharge de type filamentaire en augmentant la distance pointe-plan ou en augmentant la pression, toutes choses égales par ailleurs. Nous mettons en avant par imagerie CCD rapide deux phases de développement de ces décharges, également analysées à l'aide de simulations COMSOL. Pour une pression de 1 bar, l'application de ces décharges à un mélange combustible air/propane provoque un allumage à la pointe, avec une énergie minimale de décharge de 8±2 mJ. L'inflammation est obtenue pour une impulsion de tension unique, et la richesse minimum pour l'obtenir est 0,7. La question de la contribution de l'apport radicalaire en comparaison de l'apport thermique à l'apparition du noyau de flamme se pose. L'analyse paramétrique basée sur l'effet de l'atome d'oxygène sur les délais d'inflammation montre qu'il est nécessaire de convertir entre 0,5 et 0,8% d'oxygène moléculaire pour pouvoir allumer à délai équivalent et avec 100 K de moins par rapport à une auto-inflammation. Par ailleurs, la température du gaz à 1 mm de la pointe a été mesurée par spectroscopie Raman spontanée, en collaboration avec le laboratoire CORIA (Rouen) : cette température reste proche de l'ambiante pour une énergie de 30 mJ et une concentration de propane de 1,7 %. Ainsi les radicaux jouent probablement un rôle non négligeable dans le déclenchement de combustion par décharge nanoseconde mono-impulsionnelle.
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Tse, Jonathan Michael. "High-Voltage Signal Generator for Biomedical Applications." Thesis, University of Canterbury. Electrical and Computer, 2011. http://hdl.handle.net/10092/7326.
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Electroporation is the process where externally applied electric fields cause significantly increased permeability of the cell membrane. The increased permeability allows the transport of external compounds into the cell. This is important for applications in electrochemotheropy, electrofusion and drug delivery.
Electroporation also has applications in the disinfection of liquids. Given a high enough electric field across the cell membrane, the electroporation process can become irreversible, leading to cell destruction. With the cell membrane under an intense electric field, the cell membrane structure fails causing the cell to die. Conventional liquid beverage disinfection systems rely on slow heating methods requiring large power
requirements; this can reduce the taste and quality of some liquids.
Pulse generators provide the necessary electric fields to produce the required voltage potential across the cell membrane. The usefulness of electroporation depends on
several parameters such as amplitude, frequency and rise/fall times of the electric field. The wave shape also has a bearing on performance, and is limited by the pulse generator
topology. A multilevel bipolar waveform is desired with operating frequencies above about 1 kHz. The cascaded H-bridge or full-bridge topology is the most useful as it capable of producing multilevel bipolar waveforms at high frequency.
This thesis presents the design and implementation of a multilevel high-voltage pulse generator, capable of creating very high-voltage AC pulses. MOSFET switching devices in conjunction with good layout practices were used to provide required fast switching speeds. The full-bridge topology is used to create a multilevel output profile through cascading of multiple stages. As a full-bridge topology inherently creates a
RCL resonant network, there are many challenges associated with mitigating high-frequency noise sources.
Two separate stages are built, a low voltage stage capable of outputting up to 200 Vp and a high voltage stage capable of switching up to 1 kVp. A control board was also built for pulse signal generation and user configuration of the output waveforms. The designed pulse generator can produce short pulses of up to 1.4 kVp at frequencies of up to 350 kHz using primarily resistive loads (that simulate a conductive liquid load).
Little high frequency switching noise was observable on the output waveform. A single stage pulse generator was also tested with actual liquid loads using an electrode chamber, demonstrating electroporation. The liquid load testing was performed on water and milk derived from milk powder. Results showed that the liquid loads were consistent with primarily resistive loads.
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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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Rodriguez, John Israel 1972. "Distributing switch circuits for high voltage pulse applications." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80609.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (p. 145).
by John Israel Rodriguez.
M.Eng.
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Ghasemi, Zarir. "Stacking of IGBT devices for fast high-voltage high-current applications." Thesis, University of Strathclyde, 2007. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21731.
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The development of solid-state switches for pulsed power applications has been of considerable interest since high-power semiconductor devices became available. However, the use of solid-state devices in the pulsed power environment has usually been restricted by device limitations in either their voltage/current ratings or their switching speed. The stacking of fast medium-voltage devices, such as IGBTs, to improve the voltage rating, makes solid-state switches a potential substitute for conventional switches such as hard glass tubes, thyratrons and spark gaps. Previous studies into stacking IGBTs have been concerned with specific devices, designed or modified particularly for a specific application. The present study is concerned with stacking fast and commercially available IGBTs and their application to the generation of pulsed electric field and the switching of a high intensity Xenon flashlamp. The aim of the first section of the present study was to investigate different solid-state switching devices with a stacking capability and this led to the choice of the Insulated Gate Bipolar Transistor (IGBT). It was found that the collector-emitter voltage decreases in two stages in most of the available IGBTs. Experiments and simulation showed that a reason for this behaviour could be fast variations in device parasitic parameters particularly gate-collector capacitance. Choosing the proper IGBT, as well as dealing with problems such as unbalanced voltage and current sharing, are important aspects of stacking and these were reported in this study. Dynamic and steady state voltage imbalances caused by gate driver delay was controlled using an array of synchronised pulses, isolated with magnetic and optical coupling. The design procedure for pulse transformers, optical modules, the drive circuits required to minimise possible jitter and time delays, and over-voltage protection of IGBTmodules are also important aspects of stacking, and were reported in this study. The second purpose of this study was to investigate the switching performance of both magnetically coupled stacks, in pulse power applications such as Pulse Electric Field (PEF) inactivation of microrganisms and UV light inactivation of food-related pathogenic bacteria. The stack, consisting of 50 1.2 kV IGBTs with the voltage and current capabilities of 10 kV, 400 A, was incorporated into a coaxial cable Blumlein type pulse - generator and its performance was successfully tested with both magnetic and optical coupling. As a second application of the switch, a fully integrated solid-state Marx generator was designed and assembled to drive a UV flashlamp for the purpose of microbiological inactivation. The generator has an output voltage rating of 3 kV and a peak current rating of 2 kA, although the modular approach taken allows for a number of voltage and current ratings to be achieved. The performance of the switch was successfully tested over a period of more than 10⁶ pulses when it was applied to pulse a xenon flashlamp.
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Christou, Ilias. "Optimisation of high voltage electrical systems for aerospace applications." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/optimisation-of-high-voltage-electrical-systems-for-aerospace-applications(9b8c70c0-7c82-4191-9199-bb05360f1b40).html.
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Increased electrical power demands are being experienced on the new generation of aircraft due to an increased reliance on electrical technology of systems such as air conditioning, de-icing systems and electrical flight control actuation. Distribution of power at higher AC and DC voltages is therefore now being seen in modern aircraft to avoid the penalties incurred due to high cable weights. Voltages have increased past the minimum of Paschen's law resulting in a risk that life limiting partial discharge (PD) damage can occur in the insulation systems. This thesis uses a theoretical analysis backed by PD experimental results to investigate the optimal operating voltage of a cabling system. In addition, it proposes a methodology for optimizing the operating voltage level based on an analysis of the power carrying capability of cabling within a fixed and a non-fixed volume system and the derivation of the cable weight as a function of voltage. Furthermore the power carrying capability of a certain round cable system is compared with an insulated flat conductor system as in a printed circuit board (PCB). An initial assessment has been carried out to determine whether more power can be delivered via insulated flat solid conductors as in a PCB, instead of using round cables. The reason why there is a need to investigate this aspect, is because using new PCB technology can offer several advantages over traditional cabling harnesses. The work done has shown that the optimal operating point (e.g. maximum power to weight ratio) for an aircraft power system, does not improve after certain voltage levels. A tradeoff between cable weight and power transfer is required and furthermore the use of DC systems can result in higher power transfers than conventional three phase/400Hz AC systems. The PCB maximum power transfer assessment has also shown that insulated flat conductor systems can offer higher power transfer efficiencies. In addition, experimental AC and DC PD tests on certain unscreened aerospace cables (laid out in different configurations), have shown that the theoretical analysis employed to determine cable safe operating voltages gives conservative results.
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Holmgren, Jens. "Investigation of alternative current measurements in high-voltage applications." Thesis, Linköping University, Department of Science and Technology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8149.
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ABB:s MACH2 system uses a number of currents to ignite thyristors for AC/DC-trassfformation and they are measured for control and protection. The measurement methods used today has major drawbacks. Two alternative techniques are investigated, one based on the Hall-Effect (HED) and the other based on Anisotropic Magnetoreistanse (AMR), both techniques sensing the magnetic field produced by currents in a conductor. The HED hawe low sensitivity so some kind of flux concentrators is needed. This adds volume, costs and complexity to the device. The AMR technique is much more sensitive than the HED. Unfortunately AMR are also much more sensitive for high over currents that may damage the devise, and they are not as common on te market. By testing linearity, step response and frequency dependency for some components, my conclusion is that HED components with toroidal flux concentrators utilizing magnetic feedback (Closed Loop, CL) may be used in this particular application. A drawback with CL are that they, when measuring sharp edged step signals, suffer from overshoots at the output that might activate the over current protection.
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Zhang, Yi. "Modelling of photoconductive switches in high voltage power applications." Thesis, University of Brighton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239720.
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Rogers, Michael. "High-speed low-voltage line driver for SerDes applications." Thesis, Oxford Brookes University, 2009. https://radar.brookes.ac.uk/radar/items/d7f9d856-ae6d-4eab-bb7d-aa54376560d6/1/.
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The driving factor behind this research was to design & develop a line driver capable of meeting the demanding specifications of the next generation of SerDes devices. In this thesis various line driver topologies were analysed to identify a topology suited for a high-speed low-voltage operating environment. This thesis starts of by introducing a relatively new high-speed communication Device called SerDes. SerDes is used in wired chip-to-chip communications and operates by converting a parallel data stream in a serial data stream that can be then transmitted at a higher bit rate, existing SerDes devices operate up to 12.5Gbps. A matching SerDes device at the destination will then convert the serial data stream back into a parallel data stream to be read by the destination ASIC. SerDes typically uses a line driver with a differential output. Using a differential line driver increases the resilience to outside sources of noise and reduces the amount of EM radiation produced by transmission. The focus of this research is to design and develop a line driver that can operate at 40Gbps and can function with a power supply of less than IV. This demanding specification was decided to be an accurate representation of future requirements that a line driver in a SerDes device will have to conform to. A suitable line driver with a differential output was identified to meet the demanding specifications and was modified so that it can perfonn an equalisation technique called pre-distortion. Two variations of the new topology were outlined and a behavioural model was created for both using Matlab Simulink. The behavioural model for both variants proved the concept, however only one variant maintained its perfomance once the designs were implemented at transistor level in Cadence, using a 65nm CMOS technology provided by Texas Instruments. The final line driver design was then converted into a layout design, again using Cadence, and RC parasitics were extracted to perfom a post-layout simulation. The post layout simulation shows that the novel line driver can operate at 40Gbps with a power supply of 1 V - O.8V and has a power consumption of 4.54m W /Gbps. The Deterministic Jitter added by the line driver is 12.9ps.
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Githiari, Anthony Njoroge. "The design of semiconductor switches for high voltage applications." Thesis, University of Cambridge, 1996. https://www.repository.cam.ac.uk/handle/1810/272513.
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Khanna, Puneet. "High voltage conversion for MEMS applications using micromachined capacitors." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000551.
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Zabihi, Sasan. "Flexible high voltage pulsed power supply for plasma applications." Thesis, Queensland University of Technology, 2011. https://eprints.qut.edu.au/48137/1/Sasan_Zabihi_Sheykhrajeh_Thesis.pdf.
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Demands for delivering high instantaneous power in a compressed form (pulse shape) have widely increased during recent decades. The flexible shapes with variable pulse specifications offered by pulsed power have made it a practical and effective supply method for an extensive range of applications. In particular, the release of basic subatomic particles (i.e. electron, proton and neutron) in an atom (ionization process) and the synthesizing of molecules to form ions or other molecules are among those reactions that necessitate large amount of instantaneous power. In addition to the decomposition process, there have recently been requests for pulsed power in other areas such as in the combination of molecules (i.e. fusion, material joining), gessoes radiations (i.e. electron beams, laser, and radar), explosions (i.e. concrete recycling), wastewater, exhausted gas, and material surface treatments. These pulses are widely employed in the silent discharge process in all types of materials (including gas, fluid and solid); in some cases, to form the plasma and consequently accelerate the associated process.
Due to this fast growing demand for pulsed power in industrial and environmental applications, the exigency of having more efficient and flexible pulse modulators is now receiving greater consideration. Sensitive applications, such as plasma fusion and laser guns also require more precisely produced repetitive pulses with a higher quality. Many research studies are being conducted in different areas that need a flexible pulse modulator to vary pulse features to investigate the influence of these variations on the application. In addition, there is the need to prevent the waste of a considerable amount of energy caused by the arc phenomena that frequently occur after the plasma process. The control over power flow during the supply process is a critical skill that enables the pulse supply to halt the supply process at any stage.
Different pulse modulators which utilise different accumulation techniques including Marx Generators (MG), Magnetic Pulse Compressors (MPC), Pulse Forming Networks (PFN) and Multistage Blumlein Lines (MBL) are currently employed to supply a wide range of applications. Gas/Magnetic switching technologies (such as spark gap and hydrogen thyratron) have conventionally been used as switching devices in pulse modulator structures because of their high voltage ratings and considerably low rising times. However, they also suffer from serious drawbacks such as, their low efficiency, reliability and repetition rate, and also their short life span. Being bulky, heavy and expensive are the other disadvantages associated with these devices. Recently developed solid-state switching technology is an appropriate substitution for these switching devices due to the benefits they bring to the pulse supplies. Besides being compact, efficient, reasonable and reliable, and having a long life span, their high frequency switching skill allows repetitive operation of pulsed power supply. The main concerns in using solid-state transistors are the voltage rating and the rising time of available switches that, in some cases, cannot satisfy the application’s requirements. However, there are several power electronics configurations and techniques that make solid-state utilisation feasible for high voltage pulse generation. Therefore, the design and development of novel methods and topologies with higher efficiency and flexibility for pulsed power generators have been considered as the main scope of this research work. This aim is pursued through several innovative proposals that can be classified under the following two principal objectives.
• To innovate and develop novel solid-state based topologies for pulsed power generation
• To improve available technologies that have the potential to accommodate solid-state technology by revising, reconfiguring and adjusting their structure and control algorithms.
The quest to distinguish novel topologies for a proper pulsed power production was begun with a deep and through review of conventional pulse generators and useful power electronics topologies. As a result of this study, it appears that efficiency and flexibility are the most significant demands of plasma applications that have not been met by state-of-the-art methods. Many solid-state based configurations were considered and simulated in order to evaluate their potential to be utilised in the pulsed power area. Parts of this literature review are documented in Chapter 1 of this thesis.
Current source topologies demonstrate valuable advantages in supplying the loads with capacitive characteristics such as plasma applications. To investigate the influence of switching transients associated with solid-state devices on rise time of pulses, simulation based studies have been undertaken. A variable current source is considered to pump different current levels to a capacitive load, and it was evident that dissimilar dv/dts are produced at the output. Thereby, transient effects on pulse rising time are denied regarding the evidence acquired from this examination. A detailed report of this study is given in Chapter 6 of this thesis.
This study inspired the design of a solid-state based topology that take advantage of both current and voltage sources. A series of switch-resistor-capacitor units at the output splits the produced voltage to lower levels, so it can be shared by the switches. A smart but complicated switching strategy is also designed to discharge the residual energy after each supply cycle. To prevent reverse power flow and to reduce the complexity of the control algorithm in this system, the resistors in common paths of units are substituted with diode rectifiers (switch-diode-capacitor). This modification not only gives the feasibility of stopping the load supply process to the supplier at any stage (and consequently saving energy), but also enables the converter to operate in a two-stroke mode with asymmetrical capacitors. The components’ determination and exchanging energy calculations are accomplished with respect to application specifications and demands. Both topologies were simply modelled and simulation studies have been carried out with the simplified models. Experimental assessments were also executed on implemented hardware and the approaches verified the initial analysis. Reports on details of both converters are thoroughly discussed in Chapters 2 and 3 of the thesis.
Conventional MGs have been recently modified to use solid-state transistors (i.e. Insulated gate bipolar transistors) instead of magnetic/gas switching devices. Resistive insulators previously used in their structures are substituted by diode rectifiers to adjust MGs for a proper voltage sharing. However, despite utilizing solid-state technology in MGs configurations, further design and control amendments can still be made to achieve an improved performance with fewer components. Considering a number of charging techniques, resonant phenomenon is adopted in a proposal to charge the capacitors. In addition to charging the capacitors at twice the input voltage, triggering switches at the moment at which the conducted current through switches is zero significantly reduces the switching losses. Another configuration is also introduced in this research for Marx topology based on commutation circuits that use a current source to charge the capacitors. According to this design, diode-capacitor units, each including two Marx stages, are connected in cascade through solid-state devices and aggregate the voltages across the capacitors to produce a high voltage pulse. The polarity of voltage across one capacitor in each unit is reversed in an intermediate mode by connecting the commutation circuit to the capacitor. The insulation of input side from load side is provided in this topology by disconnecting the load from the current source during the supply process. Furthermore, the number of required fast switching devices in both designs is reduced to half of the number used in a conventional MG; they are replaced with slower switches (such as Thyristors) that need simpler driving modules. In addition, the contributing switches in discharging paths are decreased to half; this decrease leads to a reduction in conduction losses. Associated models are simulated, and hardware tests are performed to verify the validity of proposed topologies. Chapters 4, 5 and 7 of the thesis present all relevant analysis and approaches according to these topologies.
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Marzoughi, Alinaghi. "Investigating Impact of Emerging Medium-Voltage SiC MOSFETs on Medium-Voltage High-Power Applications." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/81822.
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For decades, the Silicon-based semiconductors have been the solution for power electronics applications. However, these semiconductors have approached their limits of operation in blocking voltage, working temperature and switching frequency. Due to material superiority, the relatively-new wide-bandgap semiconductors such as Silicon-Carbide (SiC) MOSFETs enable higher voltages, switching frequencies and operating temperatures when compared to Silicon technology, resulting in improved converter specifications. The current study tries to investigate the impact of emerging medium-voltage SiC MOSFETs on industrial motor drive application, where over a quarter of the total electricity in the world is being consumed.
Firstly, non-commercial SiC MOSFETs at 3.3 kV and 400 A rating are characterized to enable converter design and simulation based on them. In order to feature the best performance out of the devices under test, an intelligent high-performance gate driver is designed embedding required functionalities and protections. Secondly, total of three converters are targeted for industrial motor drive application at medium-voltage and high-power range. For this purpose the cascaded H-bridge, the modular multilevel converter and the 5-L active neutral point clamped converters are designed at 4.16-, 6.9- and 13.8 kV voltage ratings and 3- and 5 MVA power ratings. Selection of different voltage and power levels is done to elucidate variation of different parameters within the converters versus operating point.
Later, comparisons are done between the surveyed topologies designed at different operating points based on Si IGBTs and SiC MOSFETs. The comparison includes different aspects such as efficiency, power density, semiconductor utilization, energy stored in converter structure, fault containment, low-speed operation capability and parts count (for a measure of reliability). Having the comparisons done based on simulation data, an H-bridge cell is implemented using 3.3 kV 400 A SiC MOSFETs to evaluate validity of the conducted simulations.
Finally, a novel method is proposed for series-connecting individual SiC MOSFETs to reach higher voltage devices. Considering the fact that currently the SiC MOSFETs are not commercially available at voltages higher above 1.7 kV, this will enable implementation of converters using medium-voltage SiC MOSFETs that are achieved by stacking commercially-available 1.7 kV MOSFETs. The proposed method is specifically developed for SiC MOSFETs with high dv/dt rates, while majority of the existing solutions could only work merely with slow Si-based semiconductors.Ph. D.
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Almohammed, Fouad. "Application des électrotechnologies pour une valorisation optimisée de la betterave à sucre dans un concept de bioraffinerie." Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2328/document.
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Ce travail de thèse concerne l’utilisation des électrotechnologies pour une valorisation optimisée de la betterave à sucre conformément au concept de bioraffinerie. Les électro-technologies appliquées sont les champs électriques pulsés (CEP) et les décharges électriques de haute tension (DEHT). L’étude s’attache d’une part à l’optimisation d’un procédé alternatif pour l’extraction du sucre par pressage alcalin à froid assisté par CEP. D’autre part, elle propose des nouvelles voies pour la valorisation de deux coproduits de l’industrie betteravière qui sont les radicelles et la pulpe de betterave. Dans la première partie, le traitement électrique par CEP couplé au chaulage permet une meilleure désintégration du tissu betteravier. Il permet d’accélérer les cinétiques du pressage, d’améliorer le rendement ainsi que la qualité du jus et d’alléger la procédure de purification en aval de l’extraction. Une étude paramétrique d’optimisation a permis d’identifier le meilleur itinéraire d’application de ce nouveau procédé d’extraction. Les cossettes fraîches de betterave sont prétraitées par CEP à 600 V/cm pour 10 ms (Q = 2,7 Wh/kg). Les cossettes électroporées sont ensuite pressées à froid pour extraire 75 % du jus. Les cossettes pressées subissent un pressage alcalin avec 10 % du lait de chaux. Afin d’extraire le sucre résiduel dans le gâteau de pressage obtenu, deux étapes de pressage supplémentaires avec une étape intermédiaire d’hydratation sont nécessaires. Ce procédé optimisé permet de bien épuiser les cossettes en sucre (perte en sucre de 0,23 % et matière sèche de pulpes de 39 %) pendant une courte durée d’extraction (30 min) avec un faible soutirage (108 %) par rapport au procédé de diffusion. Il permet ainsi des économies significatives de matière et d’énergie surtout pour les étapes d’extraction du jus et de séchage de pulpes. Par rapport au procédé conventionnel, le gain énergétique s’élève à 91,96 × 106 kWh pour une usine traitant 10 000 t/j de betteraves pendant une campagne de 110 jours. De plus, le procédé proposé permet de simplifier la procédure de purification et de réduire de 50 à 60 % la quantité de chaux utilisée. Dans la deuxième partie de cette étude, deux procédés de transformation ont été proposés et optimisés à l’échelle laboratoire pour la valorisation des radicelles et de la pulpe de betterave à sucre. Les radicelles ont été utilisées pour produire du bioéthanol. Le jus brut de radicelles a été extrait par pressage à froid assisté par CEP. La production du bioéthanol a été achevée par fermentation alcoolique. Le prétraitement par CEP (450 V/cm, 10 ms) a permis d’accélérer la cinétique de pressage, d’augmenter le rendement en solutés (79,85 % vs. 16,8 %) et d’obtenir un jus plus concentré (10 % vs. 5,2 %). Le procédé optimisé permet de produire environ 41,75 L de bioéthanol par tonne de radicelles lorsque l’on applique un prétraitement par CEP contre seulement 8,2 L de bioéthanol sans prétraitement électrique confirmant ainsi le potentiel de ce nouveau schéma de valorisation. La pulpe de betterave déshydratée ayant une matière sèche de 92,8 % a été utilisée pour l’extraction de pectines. L’étude réalisée a montré que l’application d’un prétraitement par DEHT permet d’intensifier l’extraction des pectines. Le gain relatif de rendement en pectines est de 25,3 % pour une énergie consommée de 76,2 kJ/kg. Le schéma de bioraffinage proposé pourra aider au maintien de la filière betteravière en France après la suppression de système de quotas sucriers dans l’Union européen qui entrera en vigueur le 1er octobre 2017This work discusses the use of electrotechnologies for an optimized valorization of sugar beet according to the concept of biorefinery. The applied electrotechnologies are pulsed electric fields (PEF) and high-voltage electrical discharges (HVED). The study firstly aims at optimizing an alternative method for sugar extraction by PEF assisted cold alkaline pressing. On the other hand, it proposes new ways for valorizing two by-products of sugar beet industry, which are sugar beet tails and pulps. In the first part, PEF treatment combined with liming leads to a better disintegration of beet tissue. It permits accelerating of pressing kinetics, improvement of juice yield and quality, and reduction of subsequent purification procedure. A parametric optimization study identified the best application itinerary of the proposed extraction process. Fresh sugar beet cossettes are pretreated by PEF at 600 V/cm for 10 ms (Q = 2.7 Wh/kg). The electroporated cossettes are then pressed to extract 75% of intracellular juice. Compressed cossettes are subjected to an alkaline pressing with 10% lime milk. In order to extract the residual sucrose in the obtained press-cake, two additional steps of pressing with an intermediate hydration are required. This optimized process allows well exhausting the sugar cossettes (sugar loss of 0.23% and pulp dry matter of 39%) for a short extraction (30 min) and with low draft (108%) compared to diffusion method. Thus, it allows substantial saving in materials and energy especially for juice extraction and pulp drying. Compared to the conventional method, the energy saving amounted to 91.96 × 106 kWh for a sugar beet factory treating 10 000 tons per day for a campaign of 110 days. In addition, the proposed method simplifies the purification procedure of raw juice and reduces the used amount of lime from 50 to 60%. In the second part of this study, two processing methods were proposed and optimized at lab-scale for valorization of sugar beet tails and pulps. Sugar beet tails were used to produce bioethanol. Raw juice of beet tails was extracted by PEF assisted cold pressing. Bioethanol production was then done by alcoholic fermentation. Pretreatment of beet tails with PEF (450 V/cm, 10 ms) permits accelerating the pressing kinetics, increasing the yield of solutes (79.85% vs. 16.8%), and leads to a more concentrated juice (10% vs. 5.2%). The optimized process permits the production of about 41.75 L of bioethanol per ton of beet tails when PEF pretreatment is applied against only 8.2 L of bioethanol without PEF confirming the potential of this new valorization scheme. Dried beet pulp having a dry matter of 92.8% was used for pectin recovery. The present study showed that the application of HVED pretreatment leads to intensify pectin extraction. The relative gain of pectin yield is 25.3% with an energy consumption of 76.2 kJ/kg. The proposed biorefinery scheme could protect the sugar beet industry in France after the suppression of the sugar quota system in the European Union, which will take effect on 1st October 2017
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Kopeček, Pavel. "Analýza, vlastnosti a aplikace komerčně dostupných napěťových násobiček." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219161.
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This work deals with the analog multipliers, mainly of the voltage multipliers. Also the modifications of current output will appear here. The first part is devoted to a choice several multipliers and a description of their functions, the possible involvement and introduction of the most important catalog values. The next section deals with the simple application that contains at least one of the multipliers. Next was the implementation of selected applications and measure their actual performance parameters. Results are then compared with computer simulations. As final step is done of tolerance and sensitivity analysis of simulated configurations of circuits.
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Rong, Hua. "Development of 4H-SiC power MOSFETs for high voltage applications." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/79426/.
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Silicon carbide is a promising wide bandgap semiconductor for high-power, high-temperature and high frequency devices, owing to its high breakdown electric field strength, high thermal conductivity and ability to grow high quality SiO2 layers by thermal oxidation. Although the SiC power MOSFET (metal-oxide-semiconductor field effect transistor) is preferred as a power switch, it has suffered from low channel mobility with only single digit field effect mobility achieved using standard oxidation process (1200◦C thermal oxidation). As such, this thesis is focussed on the development of 4H-SiC MOSFETs (both lateral and vertical MOSFETs) to improve the channel mobility and breakdown characteristics of these devices. In this work, high temperature nitridation using N2O has been investigated on MOS capacitors and MOSFETs, both with gate oxides grown directly in N2O environment or in a O2 ambient followed by a N2O post-oxidation annealing process. Results have demonstrated that at high temperature (>1200◦C) there is a significant improvement in the interface trap density to as low as (1.5x10^11cm-2eV-1) and field effect channel mobility (19cm2/V.s) of 4H-SiC MOSFET compare with a lower temperature (between 800 and 1200◦C) oxidation (1x10^12cm-2eV-1 and 4cm2/V.s). Nitridation temperatures of 1300◦C was found to be the most effective method for increasing the field effect channel mobility and reducing threshold voltage. The number of working devices per sample also increased after N2O nitridation at 1300◦C as observed for both lateral and vertical MOSFETs. Other post oxidation techniques have also been investigated such as phosphorous passivation using solid SiP2O7 planar diffusion source (PDS). The peak value of the field effect mobility for 4H-SiC MOSFET after phosphorus passivation is approximately 80cm2/V.s, which is four times more than the valued obtained using high temperature N2O annealing. Different JTE structures have been designed and simulated including single-zone JTE, space modulated JTE (SMJTE) and the novel two-step mesa JTE structures. It was found that for the same doping concentration the SM two-zone JTE and SMJTE have higher breakdown voltage than the single zone JTE. With SMJTE, the device could achieve more than 90% of the ideal parallel plane voltage from simulations and 86% from the breakdown test of the fabricated devices.
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Fisher, Craig A. "Development of 4H-SiC PiN diodes for high voltage applications." Thesis, University of Warwick, 2014. http://wrap.warwick.ac.uk/62126/.
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Despite the excellent electrical and thermal properties of 4H-silicon carbide (SiC), the fabrication of high-voltage SiC power devices is still proving problematic, being hindered by material defects resulting in low carrier lifetimes and forward voltage drift, and suboptimum ohmic contacts to p-type material. The PiN diode is one such device that suffers from the aforementioned problems, though at the same time is sought after for high voltage power electronics applications due to the prospect of greatly reduced power losses and increased power handling capability than the Si devices currently in use. As such, this thesis is focussed on the development of these devices, investigating various device structures to achieve high reverse blocking voltages as well as developing novel fabrication processes to improve the electrical performance of the devices. Electrical characterisation of ohmic contacts to p-type 4H-SiC showed that Ti/Al-based metal schemes offered the lowest specific contact resistivity of approximately 2.2 x 10-6 Ω-cm2, which was achieved after annealing at 1000°C for 2 minutes. Physical analysis showed that these annealing conditions were optimum for formation of the Ti3SiC2 alloy at the metal-semiconductor interface, the presence of which was found to correlate with lower specific contact resistivity values. Electrical characterisation of first generation PiN diodes designed for blocking 3.3 kV showed that the fabricated devices had a differential on-resistance (Ron,dif f) of 17 Ωm -cm2 at 100 A/cm2 and 25°C, and near-ideal (η = 1.3) characteristics in the diffusion current regime. Based on the measured reverse saturation currents, the carrier lifetime of the fabricated devices was estimated to be 480 ns. Reverse leakage currents were found to vary significantly across the devices, from 5 nA/cm2 up to 200 μA/cm2 at 100 V reverse bias and 25°C. Second generation 3.3 kV PiN diodes, which featured a B-implanted JTE structure, were found to block a maximum reverse voltage of 2.8 kV, which was around 85% of the target value. PiN diodes fabricated with a drift region designed for blocking 10 kV underwent thermal oxidation processes at temperatures ranging from 1400°C to 1600°C in order to increase the carrier lifetime. Devices having undergone no lifetime enhancement treatment were found to have a Ron,dif f of 11.6 mΩ-cm2 at 100 A/cm2 and 25°C, and an ideality factor η = 1.5 in the diffusion current regime. PiN diodes that had undergone thermal oxidation were found to have improved forward characteristics, with devices oxidised at 1500°C exhibiting a Ron,dif f of around 9 mΩ-cm2 at 100 A/cm2 and 25°C, an improvement of nearly 25%. A novel combined thermal oxidation and annealing process was developed and applied to second generation 10 kV PiN diodes; a mean Ron,dif f of 4.45 mΩ-cm2 was achieved, and a carrier lifetime of 1.21 μs was extracted from reverse recovery characteristics; these were both significant improvements on both the second generation control sample and the first generation thermally oxidised PiN diodes.
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Efthymiou, Loizos. "GaN-on-silicon HEMTs and Schottky diodes for high voltage applications." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/274912.
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Gallium Nitride (GaN) is considered a very promising material for use in the field of power devices as its application in power systems would result in a significant increase in the power density, reduced power losses, and the potential to operate at high frequencies. The wide bandgap of the material allows a high critical electric field to be sustained which can lead to the design of devices with a shorter drift region, and therefore with lower on-state resistance, if compared to a silicon-based device with the same breakdown voltage. The use of an AlGaN/GaN heterostructure allows the formation of a two-dimensional electron gas (2DEG) at the heterointerface where carriers can reach very high mobility values. These properties can lead to the production of High Electron Mobility Transistors (HEMTs) and Schottky barrier diodes with superior performance, even when compared to devices based on state-of-the-art technologies such as Silicon Carbide or superjunctions. Furthermore, epitaxial growth of GaN layers on silicon wafers allows a significant reduction in the production cost and makes these devices competitive from a price perspective. This thesis will deal with a variety of topics concerning the characterization, design and optimization of AlGaN/GaN HEMTs and Schottky diodes with a 600 to 650V rating. Discussion will span several topics from device cross-section physics to circuit implementation and will be based on both experimental results and advanced modelling. More specifically, the thesis is concerned with the characterization of AlGaN/GaN Schottky diodes and extraction of their main parameters such as ideality factor, barrier height and series resistance. A thorough investigation of their reverse recovery performance and a comparison to competing technologies is also given. Several topics which concern the operation of AlGaN/GaN HEMTs are then discussed. The underlying physics of p-gate enhancement mode transistors are analysed followed by a discussion of the challenges associated with the implementation of these devices at a circuit level. Finally, a comparison of the performance of a specific area-saving layout (Bonding pad over active area) and a conventional design is given. The thesis aims to significantly enhance the understanding of the behaviour of these devices to enable better or new commercial designs to emerge.
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Osgood, Karina, Andy Moysenko, Amy Webb, Dennis Schneider, Ronald Colangelo, Kenneth McMullen, Robert Wert, and Peter Muller. "A TRANSMITTER CHIP SET FOR WIRELESS TELEMETRY APPLICATIONS." International Foundation for Telemetering, 2001. http://hdl.handle.net/10150/606411.
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International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, NevadaM/A-COM, Inc. has developed a highly integrated transmitter chip set for wireless telemetry applications under a U.S. Army Development Contract. The chip set is comprised of a voltage controlled oscillator (VCO), a silicon synthesizer/phase locked loop (PLL), and a family of power amplifiers (PA's). The chip-set is designed to operate over the military L and S Band frequencies as well as the lower commercial ISM band. Using these components, M/A-COM has produced IRIG compliant transmitter modules for ballistic telemetry applications. These modules have been successfully flight tested by the Army Research Laboratory at Aberdeen Proving Ground, Maryland. This paper reviews the transmitter system architecture and presents test data for the transmitter module and individual components.
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Amankwah, Emmanuel K. "A parallel hybrid modular multilevel converter for high voltage DC applications." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13845/.
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Reliability and efficiency of power transmission has been at the forefront of research for some time and is currently being given critical consideration due to the increased dependence on electrical energy. With the increased demand for electricity, engineers are considering different methods of supply arrangement to improve the security of electricity supply. High Voltage Direct Current (HVDC) transmission is a technology that avails itself for distance power transmission, interconnection of asynchronous networks and cross sea or offshore power transmission. The main element of an HVDC system is the AC/DC or DC/AC power converter. Recently, a new breed of power converters suitable for HVDC transmission has been the subject of considerable research work. These converters are modular in structure with high efficiency and their operation results in higher power quality, with reduced filtering components when compared to the use of Line Commutated and two-level or three-level Voltage Source Converter (VSC) based transmission systems. One such modular circuit is the Parallel Hybrid Modular Multilevel Voltage Source Converter (PH-M2L-VSC). This research investigates the operation and control of the PH-M2L-VSC for HVDC applications. Control schemes supporting the operation of the converter as would be expected of an HVDC VSC are proposed, including operation with an unbalanced AC network. Simulation results from a medium voltage demonstrator and experimental results from a laboratory scale prototype are presented to validate the methods proposed and enable a performance comparison to be made with other topologies.