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Плахтий, Александр Андреевич. "Улучшение электромагнитной совместимости преобразователей тяговых подстанций постоянного с питающей и контактной сетями". Thesis, Украинский государственный университет железнодорожного транспорта, 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/22054.
Повний текст джерелаАнотація:
Диссертация на соискание учѐной степени кандидата технических наук по специальности 05.09.12 – полупроводниковые преобразователи электроэнергии. – Национальный технический университет "Харьковский политехнический институт" – Харьков - 2016.
Диссертация посвящена исследованию электромагнитных процессов в активных четырех-квадрантных выпрямителей с системами управления построенных на базе гистерезисной и широтно-импульсной модуляции, которые обеспечивают высокие показатели электромагнитной совместимости с питающей и контактной сетью. Выполнен анализ путей улучшения электромагнитной совместимости и возможности реализации рекуперации в выпрямительных установках тяговых подстанций постоянного тока. Сделан вывод, что наиболее перспективной схемой выпрямительного агрегата тяговой подстанции является схема активного трехфазного четырехквадрантного выпрямителя напряжения построенная на базе схемы автономного инвертора напряжения. Разработаны системы автоматического управления двухуровневого и трехуровневого АВН с реализации широтно-импульсной модуляции. Преимуществом разработанных систем управления является постоянная и значительно меньшая частота коммутации ключей, что обуславливает физическую реализуемость системы, а также снижение динамических потерь в преобразователе, и как следствие повышение КПД преобразователя. При этом трехуровневый АВН в сравнении с двухуровневым обладает большим числом ступеней модуляции напряжения, что обуславливает улучшенные показатели качества электроэнергии. Разработана система автоматического управления компенсационного АВН, который состоит из нескольких параллельных мостов, которые запитаны от одной сети и работают на одну нагрузку. Синхронизация каналов управления отдельных мостов с реализацией сдвига опорного сигнала ШИМ на угол ξ, обеспечивает взаимную компенсацию высших гармоник входных токов и выходного напряжения, чем достигаетсся улучшение параметров электромагнитной совместимости: коэффициент мощности 99,83%; коэффициент гармонических искажений 1,82%; коэффициент пульсаций выходного напряжения 0,1824%; мешающее напряжение в контактной сети 1,123В.<br>Thesis for candidate degree of technical sciences of speсiality 05.09.12 – Semiconductor converters of electric energy – National Technical University "Kharkov Politechnical Institute" – Kharkov - 2016.
The thesis is dedicated to investigation of electromagnetic processes and EMC parameters of the two-level, three-level and parallel three-phase four quadrant active rectifiers with power factor correction with novel automated control systems based on hysteresis modulation and PWM. Control characteristics and automated control system of active four quadrant active rectifiers with hysteresis modulation and PWM was designed. Studies have shown principle weaknesses of the hysteresis modulation. It’s high and variable switching frequency and high losses in IGBT. Automated control system based on PWM has strong advantage – constant switching frequency, that improves efficiency of convertor and EMC parameters.
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Плахтій, Олександр Андрійович. "Покращення електромагнітної сумісності перетворювачів тягових підстанцій постійного струму з живлячою та контактною мережами". Thesis, НТУ "ХПІ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/22051.
Повний текст джерелаАнотація:
Дисертація на здобуття вченого ступеня кандидата технічних наук за фахом 05.09.12 – напівпровідникові перетворювачі електроенергії. – Національний технічний університет "Харківський політехнічний інститут" – Харків - 2016.
Дисертація присвячена дослідженню електромагнітних процесів в активних трифазних випрямлячах напруги з корекцією коефіцієнта потужності з системами автоматичного управління побудованих на базі гістерезисної на широтно-імпульсної модуляції, які забезпечують високі показники електромагнітної сумісності з живлячою та контактною мережами. Отримані регулювальні характеристики АВН з гістерезисною системою управління на основі яких розроблена система автоматичного управління з реалізацією двонаправленої передачею енергії. Дослідження активних випрямлячів з гістерезисною системою управління показали реалізацію високих показників електромагнітної сумісності, проте і виявили її принципові недоліки, а саме високу і змінну частоту комутації, що значно ускладнює її фізичну реалізацію на існуючий базі IGBT транзисторів та зумовлює значні втрати в перетворювачі. Визначені аналітичні співвідношення максимальної частоти комутації ключів АВН з гістерезисною системою управління від параметрів живлячої мережі, схеми заміщення АВН, навантаження та величини уставки гістерезиса. Розроблена система управління компенсаційного активного випрямляча напруги, який складається із декількох паралельних або послідовних мостів, які заживлені від однієї мережі живлення і працюють на одне навантаження. Синхронізація каналів управління окремих мостів з реалізацією зсуву опорного сигналу ШІМ на кут зсуву ψ дозволяє реалізувати взаємну компенсацію вищих гармонік вхідного струму та вихідної напруги, чим досягається покращення показників електромагнітної сумісності: коефіцієнт потужності 99,83%; коефіцієнт гармонійних спотворень 1,82%; коефіцієнт пульсацій вихідної напруги 0,1824%; заважаючи напруга у контактній мережі 1,123В.<br>Thesis for candidate degree of technical sciences of speсiality 05.09.12 – Semiconductor converters of electric energy – National Technical University "Kharkov Politechnical Institute" – Kharkov - 2016.
The thesis is dedicated to investigation of electromagnetic processes and EMC parameters of the two-level, three-level and parallel three-phase four quadrant active rectifiers with power factor correction with novel automated control systems based on hysteresis modulation and PWM. Control characteristics and automated control system of active four quadrant active rectifiers with hysteresis modulation and PWM was designed. Studies have shown principle weaknesses of the hysteresis modulation. It’s high and variable switching frequency and high losses in IGBT. Automated control system based on PWM has strong advantage – constant switching frequency, that improves efficiency of convertor and EMC parameters.
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Perera, Aravinda. "Virtual Synchronous Machine-based Power Control in Active Rectifiers for Micro Grids." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19202.
Повний текст джерелаАнотація:
This dissertation presents an analytical study on virtual synchronous machine-based power control in active rectifiers for micro grids supported by prototype modelling, simulation results and discussions.Popularity and demand of the distributed energy resources and renewable energy sources are increasing due to their economic and environmental friendliness. Concept of micro grid with an active rectifier (AR) interface has been found to be promising for smart integration of such distributed generation units. Having the presence of a synchronous generator (SG) in a micro grid introduces several advantages in terms of stability and reliability in the power system. This is mainly owed to the inertia, damping and load sharing properties of SG. This in return, gives rise to the question if an AR of a micro grid can imitate the behaviour of a synchronous generator, can the stability and reliability introduced by SG be replicated in a micro grid. A research on the state-of-the-art for uninterruptible power supplies (UPS) has been carried out to identify the implementation and the control strategies of redundancy and parallel operation as UPS has been an established technology over the last decades. The theoretical study on virtual synchronous machine (VSM) concept in the fall, 2011, has been extended in developing a model with classical inner current control and outer voltage control loops based on the synchronous reference frame.The complete active rectifier model has been able to emulate the inertia, damping and load sharing properties of a SG and redundancy and expandability of parallel UPS systems. It must be emphasized that due to the flexibility of the virtual machine parameters and the absence of magnetic saturation and eddy current losses, a much improved performance have been achieved with a VSM compared to a synchronous generator.Simulations have been carried out for single and parallel operation of active rectifiers in island and grid-tied modes with satisfactory stability, damping and power sharing features.Key words – Active rectifier, virtual synchronous machine, micro grid, uninterruptible power supply, load sharing, redundancy, island mode, grid-tied mode, synchronous reference frame
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Müller, Jonas [Verfasser]. "Active Toe-Angle Compensation / Jonas Müller." München : Verlag Dr. Hut, 2013. http://d-nb.info/1035049937/34.
Повний текст джерела
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Bush, Robert Walton. "Design of an active acceleration compensation robot." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/19314.
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Anwar, Saeed. "Active Power Compensation of Microgrid Connected Systems." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1406653103.
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Carpenter, Paul Andrew. "Active filter current compensation for transmission optimisation." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/24291.
Повний текст джерелаАнотація:
This dissertation is based on the fact that any m-wire electrical system can be modelled as m-equivalent Thevenin voltages and impedances when viewed from any node. The dissertation describes how to calculate the optimal distribution of currents, so a specific amount of power can flow through and reach the network equivalent Thevenin voltages with minimal losses. The optimal current distribution method uses a recently patented method which calculates the optimal currents for each of the wires which are shown to be obtained from the Thevenin parameters and power flow at any instant in time at any node. Once the ideal currents are found, these can be obtained by active and passive devices to inject a specific amount of power (positive and negative) as to compensate existing currents. The focus is particularly on the proof of concept by simulations and physical experiments with work not specifically described in the patent with more emphasis on the optimisation to active compensation. It is explained and shown how this can be implemented using the Malengret and Gaunt method. This method reduces the cost in application where not all the currents need to be processed through a converter (e.g. inverter) but only the difference between the existing and desired optimal currents. A smaller shunt parallel converter can result with ideal current flow without the need for interrupting the currents as described in the present patent. The methodology is explained and demonstrated by simulation.
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Decker, Michael Wilhelm. "Active acceleration compensation for transport of delicate objects." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/21258.
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Pinfold, W. R. "An active motion compensation system using multiple bodies." Thesis, University of Strathclyde, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381330.
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Pomierski, Wojciech. "Position signal filtering for hydraulic active heave compensation system." Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71095.
Повний текст джерелаАнотація:
In the paper a new position signal filtering method with position prediction is presented along with test results using a simulation tool. The complete active heave compensation system performance with input signal filtering is also shown. The control system uses an input acceleration signal taken from the motion reference unit, which usually contains noise that is not acceptable for the position controller. Currently, a Kalman filter is used which is okay to use for certain conditions. The filter works similarly to how it is used for autonomous applications where two input positions are necessary, one from position sensors and another one taken from the model. The challenge is that there is no physical wave model available for the Kalman filter used for offshore position control and the waves are not predictable. It was found that a Kalman filter with a special signal prediction instead of the model input can be used. This position prediction helps to avoid system delays and the potential of missing the signal for a short period of the time.
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Granjon, Pierre. "Contribution à la compensation active des vibrations des machines électriques." Phd thesis, Grenoble INPG, 2000. http://tel.archives-ouvertes.fr/tel-00101286.
Повний текст джерелаАнотація:
Ce travail de recherche est consacré à l'élaboration d'une méthode de compensation active des vibrations d'une machine tournante électrique. Son originalité tient au fait que les enroulements statoriques sont alimentés par<br />des courants de commande additionnels afin d'engendrer des forces radiales sur le stator. Celui-ci répond alors par des vibrations additionnelles qui interagissent avec les vibrations naturelles de la machine. Le but de ce<br />système de contrôle actif est donc de calculer la valeur ”optimale” de ces courants, permettant de minimiser la puissance des signaux vibratoires au niveau de capteurs accéléromètriques fixés à la périphérie du stator.<br />Dans un premier temps, la modélisation du transfert situé entre les commandes et les contre-vibrations engendrées conduit à un système linéaire et variant périodiquement dans le temps (LVPT). La fréquence fondamentale de ses variations est alors proportionnelle à la fréquence de rotation de la machine.<br />Après avoir montré l'insuffisance des méthodes classiques de contrôle actif pour cette application, une étude théorique détaillée des systèmes LVPT est réalisée. Elle conduit à la définition d'une matrice de transfert, jouant le même rôle que la fonction de transfert classique employée pour les systèmes linéaires et invariants dans le temps. Cette matrice permet d'écrire simplement la relation entre les entrées et les sorties du système<br />considéré dans le domaine fréquentiel.<br />Finalement, les résultats précédents sont utilisés afin de déterminer l'expression optimale des courants de commande minimisant la puissance des signaux de vibrations mesurés. Un algorithme récursif permet également de converger vers cet optimum, et de prendre en compte d'éventuelles variations des perturbations vibratoires à éliminer. Divers résultats, obtenus sur des signaux synthétiques puis sur des signaux vibratoires réels, illustrent les performances obtenues par ce système de contrôle actif. Il permet une réduction significative des vibrations<br />synchrones au phénomène de rotation, sans pour autant modifier les caractéristiques des autres. Enfin, son implantation en temps-réel dans un processeur numérique de traitement de signal est discutée et réalisée.
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Paschal, Matthew James 1964. "Compensation techniques for gain-bandwidth effects of active RC filters." Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/278081.
Повний текст джерелаАнотація:
The gain-bandwidth (GB) product of an operational amplifier (op amp) can effect the filtering characteristics of an infinite gain, multiple feedback, low pass active RC filter. In this thesis, the characteristics of ideal op amps and actual op amps are compared. The op amp is characterized by a dominant single pole, which is used to develop a third order voltage transfer function that describes the op amp's gain-bandwidth effects on the filter. Optimization theory is used to find adjusted values for the filter's elements to compensate for these GB effects. Of the sixty-five compensation design methods examined with the optimization program GOSPEL, twelve methods produced useful compensation results. The adjusted element values are tabulated and displayed in design graphs for several values of GB and quality factor, Q. The twelve design techniques were verified by simulating the filter with the adjusted element values using PSpice.
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Raju, N. Ravisekhar. "A decoupled converter topology for active compensation of power systems /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/5847.
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Argillander, Joakim. "Active Phase Compensation in a Fiber-Optical Mach-Zehnder Interferometer." Thesis, Linköpings universitet, Informationskodning, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-166419.
Повний текст джерелаАнотація:
This thesis investigates the phenomena of phase stability in a fiber-optical MZI (Mach-Zehnder Interferometer). The MZI is a key building block of optical systems for use in experiments with both continuous-wave light and with single photons. By splitting incoming light into two beams and allowing it to interfere with itself, an interference pattern is visible at the output, and this phenomena can be used to code information. This is the operating principle in, for example, QKD (Quantum Key Distribution) experiments. This interference requires coherence that is higher than the length difference between the beams that the incoming light is split into. Particularly the phase of the beams must be equal to achieve constructive interference. If one beam is phase-shifted (with respect to the other) due to the light having traversed a longer path, only partially constructive interference is achieved. If the phase shift also varies with time this leads to a system where experiments can no longer reliably be performed. Sources of these fluctuations are thermal, acoustic or mechanical. Fiber-optical interferometers are particularly sensitive to path length fluctuations of the waveguides as the fiber-optic medium contracts and elongates with temperature, and also has a larger surface area for circulating air to mechanically disturb the waveguides than bulk optics interferometers. In this thesis, a solution to environment-induced phase drift is presented by evaluating implementations of feedback algorithms for automatic control. The algorithms PID (Proportional-, Integral-, Derivative controller) and an ICA (IncrementalControl Algorithm) have been investigated and the performance of these controllers has been compared when used with, and without, optical enclosures. The algorithms are implemented in an FPGA (Field-Programmable Gate Array) and the controller actuates an electro-optical phase modulator that can add a phase shift to one of the light beams in the MZI. This thesis shows that significant improvement in the optical stability can be achieved with active control compared to an interferometer without active phase control.<br>Det här examensarbetet undersöker fenomenet fasstabilitet i en fiber-optisk MZI (Mach-Zehnder-Interferometer). MZI:n är en viktig byggsten i optiska system som används till experiment med både kontinuerligt emitterande lasrar och med enskilda fotoner. Genom att dela upp inkommande ljus i två strålar och låta det interferera med sig själv så bildas ett interferensmöster vid utgången vilket kan användas för att koda information. Det här är huvudprincipen bakom, till exempel, experiment inom QKD (kvantnyckeldistribution, eng: Quantum Key Distribution). Denna interferens förutsätter en koherens (högre än längdskillnaden mellan strålarna) mellan strålarna som det inkommande ljuset är uppdelat i. Särskilt måste fasen hos de bägge strålarna vara lika för att åstadkomma fullständig konstruktiv intereferens. Om en stråle är fasförskjuten (i förhållande till den andra) på grund av att ljuset har färdats en längre sträcka så uppnås endast delvis konstruktiv interferens. Om fasförskjutningen även varierar med tiden så leder det till ett system där experiment inte längre kan pålitligt utföras. Sådana fluktuationer är orsakade av termiskt, akustiskt samt mekaniskt varierande effekter. Fiberoptiska interferometrar är särskilt känsliga mot förändringar i vågledarnas längd. Detta på grund av att det fiberoptiska mediet dras ihop respektive sträcks ut med temperaturen, samt att fibern har en större ytarea som cirkulerande luft kan påverka mekaniskt jämfört med interferometrar konstruerade av bulkoptik. I det här examensarbetet presenteras en lösning på problemet med miljöinducerad fasskift genom att utvärdera reglertekniska återkopplande algoritmer. Algoritmerna PID (Proportionell-, Integrerande-, Deriverande regulator) samt ICA (Inkrementell Regleralgoritm, eng: Incremental Control Algorithm) har undersökts och deras prestanda har jämförts med samt utan avskärmning. Algoritmerna har implementerats i en FPGA (fältprogrammerbar grindmatris, eng: Field-Programmable Gate Array) och regulatorn styr en elektrooptisk fasmodulator som kan addera en fasförskjutning till en av ljusstrålarna i MZI:n. Resultat visar att passiv avskärmning inte är tillräckligt utan behöver användas tillsammans med aktiv reglering för att uppnå stabilitet över en längre tidsperiod. Detta examensarbete visar på att en signifikant förbättring i den optiska stabiliteten kan uppnås med aktiv reglering jämfört med en interferometer utan aktiv fasreglering.
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Liebig, Sebastian. "Optimization of rectifiers for aviation regarding power density and reliability." Doctoral thesis, Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-159936.
Повний текст джерелаАнотація:
The intentions of the so-called "More Electrical Aircraft" (MEA) are higher efficiency and lower weight. A main topic here is the application of electrical instead of hydraulical, pneumatical and mechanical systems. The necessary power electronic devices have intermediate DC-links, which are typically supplied by a three-phase system with active B6 and passive B12 rectifiers. A possible alternative is the B6 diode bridge in combination with an active power filter (APF). Due to the parallel arrangement, the APF offers a higher power density and is able to compensate for harmonics from several devices. The use of the diode bridge rectifier alone is not permitted due to the highly distorted phase current. The following investigations are dealing with the development of an active power filter for a three-phase supply with variable frequency from 360 to 800 Hz. All relevant components such as inductors, EMC-filters, power modules and DC-link capacitor are designed. A particular focus is put on the customized power module with SiC-MOSFETs and SiC-diodes, which is characterized electrically and thermally. The maximum supply frequency slope has a value of 50 Hz/ms, which requires a high dynamic and robustness on the control algorithm. Furthermore, the content of 5th and 7th harmonics must be reduced to less than 2 %, which demands a high accuracy. To cope with both requirements, a two-stage filter algorithm is developed and implemented in two independent signal processors. Simulations and laboratory experiments confirm the performance and robustness of the control algorithm. This work comprehensively presents the design of aerospace rectifiers. The results were published in conferences and patents<br>Hauptziele des sogenannten "More Electrical Aircraft" (MEA) sind Effizienzerhöhung und Gewichtseinsparung. Ein Schwerpunkt hierbei ist die Nutzung von elektrischen statt hydraulischen, pneumatischen und mechanischen Systemen. Die notwendigen Leistungselektroniken haben DC-Zwischenkreise, welche mittels aktiven B6 und passiven B12 Gleichrichtern aus dem Dreiphasennetz gespeist werden. Eine mögliche Alternative ist die B6 Diodenbrücke in Kombination mit einem aktiven Netzfilter, welcher aufgrund der parallelen Anordnung eine höhere Leistungsdichte aufweist und darüber hinaus mehrere Geräte gleichzeitig entstören kann. Die alleinige Nutzung einer Diodenbrücke ist aufgrund des hohen Anteils von Stromharmonischen nicht zulässig. Diese Arbeit beschäftigt sich mit der Entwicklung eines aktiven Filters für ein Dreiphasensystem mit variabler Frequenz von 360 bis 800 Hz. Es werden alle relevanten Bauteile wie Induktivitäten, EMV-Filter, Leistungsmodule und Zwischenkreiskondensator ausgelegt. Besonderes Augenmerk liegt auf dem kundenspezifischen Modul mit SiC-Dioden und SiCMOSFETs, welches vollständig elektrisch und thermisch charakterisiert wird. Die Änderung der Netzfrequenz beträgt bis zu 50 Hz/ms, was eine hohe Dynamik und Robustheit von der Filterregelung verlangt. Weiterhin ist im statischen Fall eine hohe Genauigkeit gefordert, da die 5. und 7. Harmonische auf unter 2% geregelt werden müssen. Um beiden Anforderungen gerecht zu werden, wird ein zweistufiger Regelungsalgorithmus entwickelt der auf zwei digitalen Signalprozessoren implementiert wird. Simulationen und Labormessungen bestätigen die Robustheit des Regelungskonzeptes. Diese Arbeit stellt umfassend die Entwicklung von Luftfahrtgleichrichtern dar. Die Ergebnisse wurden in Konferenzen und Patenten veröffentlicht
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Kevin, Bergman. "Design Active Rectifiers and Hybrid Energy Storage for A Farm of 10 Uppsala University Wave Energy Converter at Resonance." Thesis, Uppsala universitet, Institutionen för elektroteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-448948.
Повний текст джерела
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Abolhassani, Mehdi Towliat. "Integrated electric alternators/active filters." Texas A&M University, 2004. http://hdl.handle.net/1969.1/268.
Повний текст джерелаАнотація:
In response to energy crisis and power quality concerns, three different methodologies to integrate the concept of active filtering into the alternators are proposed. Wind energy, due to its free availability and its clean and renewable character, ranks as the most promising renewable energy resource that could play a key role in solving the worldwide energy crisis. An Integrated Doubly-fed Electric Alternator/Active filter (IDEA) for wind energy conversion systems is proposed. The proposed IDEA is capable of simultaneous capturing maximum power of wind energy and improving power quality, which are achieved by canceling the most significant and troublesome harmonics of the utility grid and power factor correction and reactive power compensation in the grid. The back-to-back current regulated power converters are employed to excite the rotor of IDEA. The control strategy of rotor-side power converter is based on position sensoreless field oriented control method with higher power density. Analysis and experimental results are presented to demonstrate the effectiveness of the proposed IDEA. In next step, an integrated synchronous machine/active filter is discussed. The proposed technology is essentially a rotating synchronous machine with suitable modification to its field excitation circuit to allow dc and ac excitations. It is shown that by controlling the ac excitation, the 5th and 7th harmonics currents of the utility are compensated. The proposed method is cost effective because it can be applied to existing standby generators in commercial and industrial plants with minimal modification to the excitation circuits. To boost the gain of harmonic compensatory, an advanced electric machine is proposed. An Asymmetric Airgap Concentrated Winding Synchronous Machine (AACWSM) with ac and dc excitation was designed and employed. It is shown that the AACWSM with its unique design, in addition to power generation capability, could be used to compensate the most dominant current harmonics of the utility. The proposed AACWSM can compensate for the 5th and 7th harmonics currents in the grid by controlling the ac field excitation. In addition, the 11th and 13th harmonics currents are also significantly reduced. This system can be used at medium and low voltages for generation or motoring mode of operation.
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Towliat, Abolhassani Mehdi. "Integrated electric alternators/active filters." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/268.
Повний текст джерелаАнотація:
In response to energy crisis and power quality concerns, three different methodologies to integrate the concept of active filtering into the alternators are proposed. Wind energy, due to its free availability and its clean and renewable character, ranks as the most promising renewable energy resource that could play a key role in solving the worldwide energy crisis. An Integrated Doubly-fed Electric Alternator/Active filter (IDEA) for wind energy conversion systems is proposed. The proposed IDEA is capable of simultaneous capturing maximum power of wind energy and improving power quality, which are achieved by canceling the most significant and troublesome harmonics of the utility grid and power factor correction and reactive power compensation in the grid. The back-to-back current regulated power converters are employed to excite the rotor of IDEA. The control strategy of rotor-side power converter is based on position sensoreless field oriented control method with higher power density. Analysis and experimental results are presented to demonstrate the effectiveness of the proposed IDEA. In next step, an integrated synchronous machine/active filter is discussed. The proposed technology is essentially a rotating synchronous machine with suitable modification to its field excitation circuit to allow dc and ac excitations. It is shown that by controlling the ac excitation, the 5th and 7th harmonics currents of the utility are compensated. The proposed method is cost effective because it can be applied to existing standby generators in commercial and industrial plants with minimal modification to the excitation circuits. To boost the gain of harmonic compensatory, an advanced electric machine is proposed. An Asymmetric Airgap Concentrated Winding Synchronous Machine (AACWSM) with ac and dc excitation was designed and employed. It is shown that the AACWSM with its unique design, in addition to power generation capability, could be used to compensate the most dominant current harmonics of the utility. The proposed AACWSM can compensate for the 5th and 7th harmonics currents in the grid by controlling the ac field excitation. In addition, the 11th and 13th harmonics currents are also significantly reduced. This system can be used at medium and low voltages for generation or motoring mode of operation.
19
Liebig, Sebastian. "Optimization of rectifiers for aviation regarding power density and reliability." Doctoral thesis, Universitätsverlag der Technischen Universität Chemnitz, 2014. https://monarch.qucosa.de/id/qucosa%3A20187.
Повний текст джерелаАнотація:
The intentions of the so-called "More Electrical Aircraft" (MEA) are higher efficiency and lower weight. A main topic here is the application of electrical instead of hydraulical, pneumatical and mechanical systems. The necessary power electronic devices have intermediate DC-links, which are typically supplied by a three-phase system with active B6 and passive B12 rectifiers. A possible alternative is the B6 diode bridge in combination with an active power filter (APF). Due to the parallel arrangement, the APF offers a higher power density and is able to compensate for harmonics from several devices. The use of the diode bridge rectifier alone is not permitted due to the highly distorted phase current.
The following investigations are dealing with the development of an active power filter for a three-phase supply with variable frequency from 360 to 800 Hz. All relevant components such as inductors, EMC-filters, power modules and DC-link capacitor are designed. A particular focus is put on the customized power module with SiC-MOSFETs and SiC-diodes, which is characterized electrically and thermally. The maximum supply frequency slope has a value of 50 Hz/ms, which requires a high dynamic and robustness on the control algorithm. Furthermore, the content of 5th and 7th harmonics must be reduced to less than 2 %, which demands a high accuracy. To cope with both requirements, a two-stage filter algorithm is developed and implemented in two independent signal processors. Simulations and laboratory experiments confirm the performance and robustness of the control algorithm.
This work comprehensively presents the design of aerospace rectifiers. The results were published in conferences and patents.<br>Hauptziele des sogenannten "More Electrical Aircraft" (MEA) sind Effizienzerhöhung und Gewichtseinsparung. Ein Schwerpunkt hierbei ist die Nutzung von elektrischen statt hydraulischen, pneumatischen und mechanischen Systemen. Die notwendigen Leistungselektroniken haben DC-Zwischenkreise, welche mittels aktiven B6 und passiven B12 Gleichrichtern aus dem Dreiphasennetz gespeist werden. Eine mögliche Alternative ist die B6 Diodenbrücke in Kombination mit einem aktiven Netzfilter, welcher aufgrund der parallelen Anordnung eine höhere Leistungsdichte aufweist und darüber hinaus mehrere Geräte gleichzeitig entstören kann. Die alleinige Nutzung einer Diodenbrücke ist aufgrund des hohen Anteils von Stromharmonischen nicht zulässig.
Diese Arbeit beschäftigt sich mit der Entwicklung eines aktiven Filters für ein Dreiphasensystem mit variabler Frequenz von 360 bis 800 Hz. Es werden alle relevanten Bauteile wie Induktivitäten, EMV-Filter, Leistungsmodule und Zwischenkreiskondensator ausgelegt. Besonderes Augenmerk liegt auf dem kundenspezifischen Modul mit SiC-Dioden und SiCMOSFETs, welches vollständig elektrisch und thermisch charakterisiert wird. Die Änderung der Netzfrequenz beträgt bis zu 50 Hz/ms, was eine hohe Dynamik und Robustheit von der Filterregelung verlangt. Weiterhin ist im statischen Fall eine hohe Genauigkeit gefordert, da die 5. und 7. Harmonische auf unter 2% geregelt werden müssen. Um beiden Anforderungen gerecht zu werden, wird ein zweistufiger Regelungsalgorithmus entwickelt der auf zwei digitalen Signalprozessoren implementiert wird. Simulationen und Labormessungen bestätigen die Robustheit des Regelungskonzeptes.
Diese Arbeit stellt umfassend die Entwicklung von Luftfahrtgleichrichtern dar. Die Ergebnisse wurden in Konferenzen und Patenten veröffentlicht.
20
Stöppler, Guido [Verfasser]. "Active compensation of structural oscillations on high dynamic gantry machines / Guido Stöppler." Aachen : Shaker, 2005. http://d-nb.info/1186588349/34.
Повний текст джерела
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Bach, Susan Elizabeth. "Chirp compensation in active mode-locked semiconductor diode laser using a DFB." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/36504.
Повний текст джерела
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Ndiaye, Abdoul Ousmane. "Compensation active des ondulations de couple d'un moteur synchrone à aimants permanents." Besançon, 2002. http://www.theses.fr/2002BESA2038.
Повний текст джерелаАнотація:
Le travail effectué dans ce mémoire présente une méthode de compression des ondulations de couple d'un moteur synchrone à aimants permanents sans pièces polaires. L'objectif est l'amélioration de la qualité de la conversion électromécanique en minimisant les ondulations de couple et les vibrations. Le mémoire commence par une présentation des caractéristiques de couple du moteur synchrone étudié et les différentes causes des ondulations de son couple. Dans le deuxième chapitre, nous avons développé une méthode permettant, à partir du développement harmonique de la force électromotrice d'un moteur asynchrone à aimants sans pièces polaires, de calculer un nombre minimal d'harmoniques de courant permettant de compenser les ondulations de couple tout en optimisant le rendement. Les troisième et quatrième chapitres présentent le banc d'essai et l'étude expérimentale des vibrations. Le banc permet d'une part d'imposer différentes formes d'ondes de courant au moteur asynchrone à l'aide d'un système de contrôle et de commande réalisés avec l'outil dSPACE et d'autre part de relever le comportement vibratoire de l'ensemble du système (banc-moteur)<br>The work carried out in this thesis presents a method of torque ripple compensation in permanent magnets synchronous motor without polar parts. The aim is the improvement of the electromechanical conversion quality by minimizing the torque ripple and the vibrations. The thesis starts with a presentation of the torque characteristics of the studied synchronous motor and the different causes of its torque ripples. In the second chapter, a computation method of optimal current harmonics is developed : starting from the back electromotive force harmonics of a magnet synchronous motor without polar parts, a minimal number of current harmonics are calculated to cancel the torque ripple while optimizing the efficiency. The third and fourth chapters present the test bench and the experimental study of the vibrations. The bench makes it possible one the one hand to fed synchronous motor with various current waveforms using a control system realized with the dSPACE tool and on the other hand to measure the vibrations of the system (bench-motor)
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da, Silva Neddef N. (Nedio). "Active phased array transceiver:an operational compensation for a multiple phase shifter system." Master's thesis, University of Oulu, 2018. http://jultika.oulu.fi/Record/nbnfioulu-201805151790.
Повний текст джерелаАнотація:
Abstract. The upcoming fifth-generation mobile technology relies on the implementation of beamforming techniques to fulfill the requirements proposed for the 2020 roll-out. One of the processes for stepping up this technique from the high-end applications to the telecommunication mass market is to be able to test, analyze and tune the product according to the specifications. After the manufacturing process, the phased antenna array, beamforming and beam-steering system must be tested against a prediction model, and corrected against deviations due to the uniqueness of the components, with the objective to conform the final product to be in accordance with specifications, while at low cost and time. The aim of this work is to propose and test different procedures for calibrating the phase component of an RF phased array transceiver with multiple phase-shifters. The different proposed procedures are compared in an over-the-air measurement through the performance when applying the beamforming and beam-steering techniques.
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Spro, Ole Christian B. "Reactive Power Compensation and Active Filtering Capabilities of the Step-down AC Chopper." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-23617.
Повний текст джерелаАнотація:
The Step-down AC Chopper (hereby referenced as "AC Chopper") has been presented in recent academic papers as a possible solution for reactive compensation. The goal of this project was to investigate and evaluate the topology to see if the praise could be justified. In addition, this project set a goal to take the research one step further by investigating if the uses of the AC Chopper could be expanded to include active filtering. The ability of the AC Chopper converter to produce harmonic current was investigated. This was the first step in developing the AC Chopper's active filtering functionality. Theorems were developed and simulations were performed with both open and closed loop control. The results show that using the AC Chopper to produce harmonic current is very difficult if not impossible. This is due to intrinsic characteristics of the topology which leads to the converter producing multiple harmonics for a single control input frequency. Hence it was concluded that the AC Chopper is not fit for performing active filtering and that the results do not support continuing any further research on the AC Chopper's filtering capabilities.A prototype of the converter was developed and built to compare the simulations against real observed behavior. The development process has been well documented in this thesis. Open loop control of the prototype was successfully implemented. The results show a good relation between the theory and the measured values. There are certain challenges connected to the realization of the AC Chopper, and the ways of dealing with these challenges have been described herein. The topology was also compared to available technology to evaluate the competitiveness regarding reactive compensation at fundamental frequency. The AC Chopper was not found advantageous compared to the VSI, a modern available solution. The efficiency of the AC Chopper has been found to be slightly higher in simulation, but this has yet to be validated with tests on real prototypes. In addition to lacking the filtering capabilities, the AC Chopper has other disadvantages including expensive components and greater volume. Together the findings in this report suggests that the AC Chopper should be limited to use in single phase systems for reactive compensation at fundamental frequency in open loop control.
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Sverdrup-Thygeson, Jørgen. "Modeling and Simulation of an Active Hydraulic Heave Compensation System for Offshore Cranes." Thesis, Norwegian University of Science and Technology, Department of Engineering Cybernetics, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9531.
Повний текст джерелаАнотація:
<p>This thesis deals with the mathematical modeling of hydraulic heave compensation systems. When performing operations such as launch and recovery of remote operated vehicles and lowering subsea installation parts to the sea floor, it is important to attenuate unwanted load motion caused by elongation of the cable and heave motion of the vessel. Quite often, such operations must be put off while waiting for the weather to calm down. Extending the window of operations by developing equipment that can handle varying sea states can result in significant cost savings. There exist both electric and hydraulic heave compensation devices, but the main focus of this thesis is on the hydraulic configurations. A mathematical model is developed in Simulink, and simulations are performed for long-crested seas with values corresponding to the average sea conditions in the North Sea.</p>
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Bó, Antônio Padilha Lanari. "Compensation Active de Tremblements Pathologiques des Membres Supérieurs via la Stimulation Electrique Fonctionnelle." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20162/document.
Повний текст джерелаАнотація:
Le tremblement, défini comme un mouvement rythmique involontaire, est un des mouvements anormaux les plus fréquents. Le tremblement n'est pas une pathologie mortelle, mais elle diminue souvent considérablement la qualité de vie de la personne. Les traitements efficaces ne sont pas encore disponibles, puisque les solutions pharmacologiques et chirurgicales souffrent encore de limitations en termes d'efficacité, de risques et de coûts. Une alternative consiste à utiliser des technologies d'assistance, tels que les exosquelettes ou la Stimulation Électrique Fonctionnelle (SEF).Néanmoins, la conception de systèmes actifs de compensation des tremblements présente plusieurs défis. Un tel système doit être capable, par exemple, d'atténuer les tremblements tout en minimisant la fatigue, la douleur et l'inconfort induit. Il doit aussi distinguer entre le tremblement et le mouvement volontaire, afin de réduire les interférences sur les mouvements intentionnels.Cette thèse se concentre donc sur l'évaluation de l'usage de la SEF pour atténuer le tremblement. Une première contribution concerne le développement des modèles neuromusculosquelettiques pour étudier l'influence des boucles réflexes sur la dynamique du tremblement, ainsi que la modulation de l'impédance de l'articulation via la co-contraction induite par la SEF. Un algorithme pour estimer en ligne le tremblement et ses caractéristiques tout en filtrant le mouvement volontaire a été proposé et validé sur patients. Enfin, un système SEF pour atténuer le tremblement basé sur le contrôle d'impédance a été conçu et évalué sur patients, alors qu'une deuxième stratégie en boucle fermée a été testée sur des sujets sains<br>Tremor, defined as an involuntary, approximately rhythmic and roughly sinusoidal movement, is one of the most common movement disorders. It is not a life-threatening pathology, but it often decreases significantly the person's quality of life. Today, effective treatments for pathological tremor are not yet available, since current pharmacological and surgical alternatives still present limitations with respect to effectiveness, risks, and costs. A different approach is the use of assistive technologies, such as upper limb exoskeletons or Functional Electrical Stimulation (FES).Nevertheless, the design of active tremor compensation systems based on these technologies presents several challenges. Such a system must be able, for instance, to attenuate tremor while minimizing the induced fatigue, pain, and discomfort. Also, it must be able to distinguish between pathological tremor and voluntary motion, in order to reduce interference on intentional movements.This thesis is focused then in evaluating the use of FES to attenuate the effects of tremor. A first contribution concerns the use of neuromusculoskeletal models to study the effects reflex pathways may produce on tremor dynamics, as well as how FES-induced co-contraction may modulate joint impedance. Also, an online algorithm to estimate tremor and its features while simultaneously filtering voluntary motion has been proposed and validated with tremor patients. Finally, a FES system to attenuate tremor based on impedance control has been designed and evaluated on tremor patients, while a second strategy using closed-loop FES control has been tested on healthy subjects
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Davies, David Bradley. "Analysis of active compensation for shock, vibration, and wind-up in disk drives." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13301.
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Soares, Guilherme Márcio. "Capacitance reduction in off-line led drivers by using active ripple compensation techniques." Universidade Federal de Juiz de Fora (UFJF), 2017. https://repositorio.ufjf.br/jspui/handle/ufjf/6044.
Повний текст джерелаАнотація:
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Previous issue date: 2017-11-18<br>CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>Este documento apresenta uma nova técnica para a minimização da ondulação de baixa frequência, típica de conversores para o acionamento de LEDs alimentados a partir da rede elétrica. Esta estratégia baseia-se na modulação em baixa frequência da razão cíclica do conversor de modo que a ondulação de corrente possa ser reduzida e, consequentemente, as capacitâncias de filtragem do conversor possam ser minimizadas. Esta técnica foi desenvolvida para a aplicação em conversores de malha única, como é o caso de conversores de estágio único ou mesmo dois estágios integrados. A modulação da razão cíclica é projetada de maneira que o comportamento de baixa frequência das principais variáveis do conversor seja alterado, permitindo uma redução da ondulação da corrente de saída ao custo de um incremento cotrolado no conteúdo harmônico da corrente de entrada. Duas possíveis metodologias para a implementação da técnica proposta são discutidas ao longo do trabalho. A primeira envolve a injeção de harmônicas específicas no sinal da razão cíclica do conversor através de ramos adicionais na estrutura de controle. Esta abordagem foi aplicada para projetar um controlador de LEDs baseado em um conversor flyback e também em uma topologia integrada baseada na conexão cascata de dois conversores Buck-boost. Este estudo inicial foi expandido para outros conversores e uma análise generalizada acerca da influência da modulação da razão cíclica no comportamento de controladores de LED alimentados a partir da rede elétrica é apresentada. A segunda metodologia para a implementação da compensação ativa da ondulação de baixa frequência do conversor é baseada na otimização de um controlador proporcional-integral a fim de que tal elemento influencie não só no comportamento dinâmico do circuito, mas também na característica de baixa frequência do conversor. Por fim são discutidas as principais contribuições da tese e algumas propostas para trabalhos futuros são apresentadas<br>This document presents a novel approach for low-frequency output current ripple minimization in off-line light-emitting diode (LED) drivers. This strategy is based on the large-signal modulation of the duty-cycle so that the output ripple can be reduced and, consequently, the required filtering capacitances of the converter can be somehow decreased. This technique is devised to be used on converters in which a single control loop is employed, such as off-line single-stage or integrated converters. The duty-cycle modulation is used to change the shape of the main waveforms of the converter, especially the input and output currents. This allows for a reduction of the output current peak-to-peak ripple while the harmonic content of the input current is increased but kept within the limits imposed by the IEC standard. Two methodologies for implementing the proposed technique are discussed along the text. The first one is related to the injection of harmonic components to the duty cycle signal by means of additional branches inserted in the conventional control structure. This approach was applied to design an off-line flyback-based LED driver and also a circuit based on the Integrated Double Buck-boost converter. This first study was expanded to other topologies and a generalized analysis regarding the impact of the duty cycle modulation on off-line converters is then presented. The second methodology for implementing the ripple compensation is based on the optimization of a proportional-integral controller so that this element is designed to influence not only in the dynamic behavior of the circuit, but also in its low-frequency characteristic. Finally, the main contributions of this work are discussed and the proposals for future works are presented.
29
Reyes-Moraga, Eduardo Felipe. "Predictive control of a direct series resonant converter with active output voltage compensation." Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/31263/.
Повний текст джерелаАнотація:
Modern high power supplies are based on resonant converters in order to use high frequency reactive elements (for reduced size) without sacrificing converter efficiency. In an effort to achieve compact high power supplies, direct power converter topologies have been considered, since these are mainly characterised by their high power density. A direct resonant converter topology combines matrix converters with conventional resonant converters. This work focused on achieving high quality input/output power and high efficiency. Thus, this thesis presents the research on the control of a direct series resonant converter. Since the resonant converter allows a sinusoidal high frequency output current to be generated, zero current switching (ZCS) was considered to reduce the power losses. Hence, since the converter is switched at every zero crossing of the output current (fixed period), model predictive control was considered. Different predictive approaches for controlling the input and output currents were developed and analysed, however, owing to the characteristics of the topology, these strategies resulted in a suboptimal control. Therefore, in order to improve the input and output qualities (reduce distortion), an output voltage compensation strategy was proposed. This compensation approach is based on adding an H-bridge converter in series between the matrix converter and the resonant tank. This converter improves the voltage applied to the resonant tank, thus, reducing the distortion at the output and, as a consequence, also the distortion at the input. The H-bridge converter utilises only a small capacitor on the dc side in comparison with conventional resonant converters and operates at a low voltage. Simulations were carried out using MATLAB/Simulink and an experimental prototype was built to validate the strategies proposed, achieving a reduction of the input current THD from 4.4% to 2.7%, a reduction of the output current distortion of approximately 40% and an analytically derived efficiency of 89.5%.
30
Ochs, David S. "Design of detailed models for use in fast aeroelastic simulations of permanent-magnet direct-drive wind turbines." Thesis, Kansas State University, 2012. http://hdl.handle.net/2097/15042.
Повний текст джерелаАнотація:
Master of Science<br>Department of Electrical and Computer Engineering<br>Ruth Douglas Miller<br>This thesis presents the design of two models for permanent-magnet direct-drive wind turbines. The models are of a 10 kW and a 5 MW wind turbine, which are representative of residential scale and commercial scale turbines respectively. The models include aerodynamic and mechanical simulations through the FAST software, as well as concurrent electrical simulations through the SimPowerSystems toolbox for MATLAB/Simulink. The aim is to provide wind turbine designers and researchers with a comprehensive simulation tool that they can use to design and test many different aspects of a wind turbine. The particular novelty of these models is their high level of detail in electromechanical simulations. For each model, a generator speed controller was designed in a reference frame attached to the generator’s rotor, and was executed with a 3-phase active rectifier using space-vector pulse-width modulation. Also for each model, active and reactive power controllers were designed in a reference frame synchronous with the grid, and were executed with a 3-phase inverter using space-vector pulse-width modulation. Additionally, a blade pitch controller was designed for the 5 MW model. Validation of the models was carried out in the MATLAB/Simulink environment with satisfactory results.
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Reader, Daniel Martin. "Nonlinear Mr Model Inversion for Semi-Active Control Enhancement With Open-Loop Force Compensation." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/32660.
Повний текст джерелаАнотація:
The increased prevalence of semi-active control systems is largely due to the emergence of cost effective commercially available controllable damper technology such as Magneto-Rheological (MR) devices. Unfortunately, MR dampers exhibit highly nonlinear behavior, thus presenting an often over-looked complexity to the control system designer. With regards to controlling dampers, the well-known Skyhook Damping control algorithm has enjoyed great success for both fully active and semi-active control problems. The Skyhook design strategy is to create a control force that emulates what a passive linear damper would create when connected to an inertial reference frame. Skyhook control is device independent since it generates a desired control force command output that must be produced by the control system. <p>
For simplicity, MR dampers are often assumed to have a linear relationship between the current input and the force output at a given relative velocity. Often this assumption is made implicitly and without knowledge of the underlying nonlinearity. This thesis shows that the overall performance of a semi-active Skyhook control system can be improved by explicitly inverting the nonlinear relationship between input current and output force. The proposed modification will work with any semi-active control algorithm, such as Skyhook, to insure that the controller performance is at least as good as the performance without the proposed modification. This technique is demonstrated through simulation on a quarter-vehicle system.
Hysteretic damping effects are incorporated into the modification by application of simple open loop force compensation. Laboratory testing of the hysteretic inversion process was performed with the goal of emulating an ideal linear damper without hysteresis. These results are compared with the implicit assumption thus providing a basis for validating the benefits of the improved methodology.<br>Master of Science
32
Chen, Weiqun. "A Microcontroller Configured Active Analog Phase Shifter at 1.96GHz." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1273841250.
Повний текст джерела
33
Humphreys, Heather Celeste. "Modeling and compensation for biodynamic feedthrough in backhoe operation." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37254.
Повний текст джерелаАнотація:
Biodynamic feedthrough occurs in many types of operator controlled machines where the operator is a passenger and the motion of the controlled machine excites motion of the human operator, creating unwanted feedback. It is a significant cause for control performance degradation in backhoes. In this research, the problem of biodynamic feedthrough is investigated in a backhoe control system. For simplification, the system is limited to a single degree of freedom. Several controller based approaches are investigated to reduce cab vibration, while maintaining cylinder tracking performance. These controllers are tested in hardware, with and without the human operator and associated biodynamic feedthrough. The effect of this cab vibration reduction on biodynamic feedthrough is tested in a small set of human subject tests. The results indicate that some vibration reduction and improvement in the operator's control performance can be achieved by adding cab vibration compensation.
34
Prasai, Anish. "Direct dynamic control of impedance for VAR and harmonic compensation." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42816.
Повний текст джерелаАнотація:
Reactive power is critical to reliable operation of the modern AC power system. There is a plethora of motor-loads, transformers, and power-electronic loads connected to the power grid, which consume reactive power for normal operation. Transmission lines also consume reactive power when they are loaded above their surge impedance loading (SIL). Reactive power can exact opportunity cost due to reduced capacity of the lines to carry real power, which in turn lowers revenue. Most transmission owners (TOs) levy large penalties against load serving entities (LSEs), industrial facilities, and other end-use customers, who consume more than their allotted amount, as measured by their power factor. These penalties are to incentivize their customers to meet their reactive power needs locally as well as to recuperate the TOs' financial losses.
Harmonic pollution is another factor that prevents the optimal operation of the grid and the connected loads. Harmonics are attributable to proliferation of the diode-rectifier- or thyristor-rectifier-interfaced loads such as variable speed ac drives and power supplies in server farms, electric arc furnaces, and other non-linear loads, which are widely employed by the industrial sector. With wider adoption of harmonic-rich loads by the consumer sector as well, such as HDTVs and compact fluorescent lamps (CFLs), greater level of triplen harmonics associated with single-phase loads are also increasingly seen on the distribution grid. The increasing penetration of renewable resources and electrification of light-duty vehicles are expected to further aggravate the stresses and congestion on the utility grid.
Reactive power compensation is necessary for supporting the AC grid and maintaining a healthy voltage stability margin. Compensation can also enhance the utilization of system capacity, lower system losses, provide fault ride-through, and enable a quick fault recovery. Existing VAR and harmonic compensation technologies are either too expensive or inadequate to meet the dynamic needs of the modern and the future power system.
This dissertation presents a novel class of Dynamic VAR and Harmonic Compensators (DVHCs) for supplying or absorbing reactive power and providing harmonic filtering, where the compensation is in shunt with the line and the load. The underlying concept is based on augmenting a static or passive component like a capacitor or an inductor with a direct AC converter and imbuing the passive component with dynamic properties. The direct AC converter can be configured as a buck, a boost, or a buck-boost. A `fail-normal' switch is an integral part of the DVHCs that bypasses the converter when it fails, preserving the original functionality and the reliability of the passive component. The DVHCs are modular and scalable such that they can be employed in applications ranging from residential and industrial with voltages less than 480 V, to power distribution level with voltages as high as 35 kV. The Dynamic Inductor (D-IND) and the Dynamic Capacitor (D-CAP) are subclasses of the DVHCs. As the applications for supplying leading VARs are more prevalent, the primary focus of this work is on the buck, the boost, and the buck-boost configurations of the D-CAP.
To understand the characteristics and operation of the DVHCs, this work has developed time-domain models for analyzing the transient and dynamic behavior; frequency-domain models for understanding the harmonic interactions and the steady-state relationships between switch duty and current harmonics; and small-signal models for studying the dynamics of the converter due to various perturbations. The small-signal models also enable extraction of transfer functions in designing controllers and assessing stability margins.
Control architectures and techniques are presented for effectively controlling the D-CAP when commutating the semiconductor devices with both high and low switching frequencies.
In modularly scaling the DVHCs to higher voltages, three medium-voltage topologies are discussed. They are based on series-connecting fractionally-rated devices, AC flying capacitors, and series cascading multiple two-level cells. These implementations allow direct connect to the medium-voltage grid, thereby obviating the use of transformers, and subsequently reducing the losses, cost, complexity, and footprint. A novel AC snubber concept is proposed to provide safe commutation of the AC switches, fault tolerance by managing the energy trapped in parasitics and filters, and to enable dynamic and static voltage sharing when integrated around the series-connected devices.
Design equations for selecting and rating the devices and components in the buck, the boost, and the buck-boost configurations of the D-CAP are presented. Three sets of example designs, with one at low-voltage and two at medium-voltage, are discussed to demonstrate the typical size and ratings of the various components under realistic operating conditions.
Measurements and the related discussions of a 40 kVA buck D-CAP prototype built to validate the effectiveness of the proposed concepts are presented.
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Lowinsky, Luc Anthony. "Nouvelle topologie de Compensateur de Puissance Réactive pour les Réseaux Ferrés 25 kV / 50 Hz." Thesis, Toulouse, INPT, 2010. http://www.theses.fr/2010INPT0036/document.
Повний текст джерелаАнотація:
Le travail présenté dans ce mémoire s’est déroulé dans le cadre d’une collaboration entre le groupe Convertisseur Statique du laboratoire LAPLACE et le département " Installations Fixes de Traction Electrique " de la Direction de l’Ingénierie de la SNCF. Aujourd'hui, la majorité du trafic sur le réseau ferré monophasé 25 kV / 50 Hz est assurée par des locomotives équipées de redresseurs contrôlés à thyristors. Du fait de l'augmentation du trafic, l'utilisation de ces locomotives nécessite la mise en place de moyen de compensation de puissance réactive afin de maintenir la tension caténaire à un niveau acceptable et de réduire la facture en énergie réactive. La correction du facteur de déplacement est réalisée en partie par des batteries de compensation fixes dont lapuissance est limitée par la tension maximale admissible à vide sur la caténaire. Afin d’adapter le niveau de compensation à la consommation, la partie fixe est complétée par un dispositif réglable basé sur une réactance contrôlée par des thyristors. Bien qu’il soit simple dans son principe, ce dispositif nécessite un filtrage des harmoniques en basse fréquence avec des circuits LC volumineux. L’objectif de cette thèse est de proposer une nouvelle topologie de compensateur de puissance réactive à haut rendement et utilisant un contrôle à modulation de largeur d’impulsion dans le but de minimiser le volume des éléments de filtrage. La première partie de ce mémoire est consacrée à une étude comparative de différentes topologies du point de vue des pertes dans les semi-conducteurs et du dimensionnement des éléments de filtrage associés. Les résultats de cette étude montrent que les topologies à base de gradateurs MLI, constituent les solutions les plus intéressantes pour réaliser le compensateur. La deuxième partie du travail concerne l’étude de l’insertion d’un compensateur à base de gradateurs MLI sur le réseau ferré avec la prise en compte des interactions harmoniques. Le cas d’étude concerne une sous-station où doit être implantée une compensation variable de 3 MVAR. Un relevé des courants délivrés par la sous-station a été effectué dans le but d’analyser leur contenu harmonique. Une modélisation de la sous-station et du compensateur est ensuite proposée et des simulations temporelles de l’ensemble sont réalisées en prenant en compte les formes d’ondes réelles des courants absorbés par les trains. Finalement, cette étude par simulation permet d’affiner le dimensionnement du compensateur à gradateurs MLI et des éléments de filtrage associés. Elle met en évidence l’avantage d’une solution, avec des gradateurs MLI en montage élévateur de tension, qui fonctionne sans transformateur et réutilise les batteries de compensation fixes déjà installées en sous-station à la fois comme diviseur de tension et éléments de filtrage. Afin de valider le principe de cette nouvelle topologie de compensateur statique de puissance réactive, un démonstrateur de 1,2 MVAR est mis en oeuvre et testé sur une plateforme d'essai de la SNCF<br>The work presented in this thesis is the result of collaboration between the Static Converters research group of LAPLACE Laboratory and the department "Installations Fixes de Traction Electrique" of the Engineering Division of the French Railways company, SNCF. Nowadays, most of the traffic in 25 kV – 50 Hz lines is achieved by old locomotives equipped with thyristor rectifiers. As traffic and load increase, reactive power compensation devices are required to keep the overhead line voltage at acceptable level and to reduce the spending for reactive power. The basic power factor correction is completed by fixed compensation banks. But the difficulty of such configuration is the no-load operation of overhead lines. The voltage can increase out of the 29 kV standard limit and to avoid this problem, variable reactive power compensator is often added to the fixed compensation banks. Nowadays, SNCF is equipped with thyristor based static VAR compensators (SVC). The main drawback of this topology is the requirement of a large LC shunt filter tuned for the third harmonic. The goal of this thesis is to find a new high-efficiency topology of STATic COMpensator (STATCOM) using PWM control to minimize the filtering components. The first part of this thesis focuses on a comparative study of different topologies in terms of semiconductor losses and filter elements size. The results of this study show that the topologies based on PWM AC Chopper are the most interesting solutions to achieve the compensator. The second part of the work concerns the influence of the connection of a STATCOM to a substation and focuses on the harmonic interactions with locomotives. The study case concerns a high traffic substation where a 3 MVAR STATCOM should be installed. Substation output current measurement was carried out in order to analyze its harmonic content. Models of the substation and the STATCOM are then proposed and simulations using real current waveforms are performed. Finally, this simulation study helps to refine the features of the AC Chopper topology and its filter elements. It highlights the advantage of a solution, with boost AC Choppers which operate without transformer and reuse the fixed compensation banks already installed in the substation as voltage divider and filter. To validate the principle of this new topology of STATCOM, a 1.2 MVAR prototype is built in LAPLACE laboratory and tested on a SNCF test platform
36
Dang, Anh X. H. "Theoretical and experimental development of an active acceleration compensation platform manipulator for transport of delicate objects." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17277.
Повний текст джерела
37
Haryani, Nidhi. "Zero Voltage Switching (ZVS) Turn-on Triangular Current Mode (TCM) Control for AC/DC and DC/AC Converters." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/96397.
Повний текст джерелаАнотація:
One of the greatest technological challenges of the world today is reducing the size and weight of the existing products to make them portable. Specifically, in electric vehicles such as electric cars, UAVs and aero planes, the size of battery chargers and inverters needs to be reduced so as to make space for more parts in these vehicles. Electromagnetic Interference (EMI) filters take up a more than 80 % of these power converters, the size of these filters can be reduced by pushing the switching frequency higher. High frequency operation (> 300 kHz) leads to a size in reduction of EMI filters though it also leads to an increase in switching losses thus compromising on efficiency. Thus, soft switching becomes necessary to reduce the losses, adding more electrical components to the converter to achieve soft switching is a common method. However, it increases the physical complexity of the system. Hence, advanced control methods are adopted for today's power converters that enable soft switching for devices specifically ZVS turn-on as the turn-off losses of next generation WBG devices are negligible. Thus, the goal of this research is to discover novel switching algorithms for soft turn-on.
The state-of the-art control methods namely CRM and TCM achieve soft turn-on by enabling bi-directional current such that the anti-parallel body diode starts conducting before the device is turned on. CRM and TCM result in variable switching frequency which leads to asynchronous operation in multi-phase and multi-converter systems. Hence, TCM is modified in this dissertation to achieve constant switching frequency, as the goal of this research is to be able to achieve ZVS turn-on for a three-phase converter. Further, Triangular Current Mode (TCM) to achieve soft switching and phase synchronization for three-phase two-level converters is proposed. It is shown how soft switching and sinusoidal currents can be achieved by operating the phases in a combination of discontinuous conduction mode (DCM), TCM and clamped mode. The proposed scheme can achieve soft switching ZVS turn-on for all the three phases. The algorithm is tested and validated on a GaN converter, 99% efficiency is achieved at 0.7 kW with a density of 110 W/in3.
The discussion of TCM in current literature is limited to unity power factor assumption, however this limits the algorithm's adoption in real world applications. It is shown how proposed TCM algorithm can be extended to accommodate phase shift with all the three phases operating in a combination of DCM+TCM+Clamped modes of operation. The algorithm is tested and validated on a GaN converter, 99% efficiency is achieved at 0.7 kVA with a density of 110 W/in3. TCM operation results in 33 % higher rms current which leads to higher conduction losses, as WBG devices have lower on-resistance, these devices are the ideal candidates for TCM operation, hence to accurately obtain the device parameters, a detailed device characterization is performed.
Further, proposed TCM+DCM+Clamped control algorithm is extended to three-level topologies, the control is modified to extract the advantage of reduced Common Mode Voltage (CMV) switching states of the three-level topology, the switching frequency can thus be pushed to 3 times higher as compared to state-of-the-art SVPWM control while maintaining close to 99 % efficiency. Two switching schemes are presented and both of them have a very small switching frequency variation (6%) as compared to state-of-the-art methods with >200% switching frequency variation.<br>Doctor of Philosophy<br>Power supplies are at the heart of today's advanced technological systems like aero planes, UAVs, electrical cars, uninterruptible power supplies (UPS), smart grids etc. These performance driven systems have high requirements for the power conversion stage in terms of efficiency, density and reliability. With the growing demand of reduction in size for electromechanical and electronic systems, it is highly desirable to reduce the size of the power supplies and power converters while maintaining high efficiency. High density is achieved by pushing the switching frequency higher to reduce the size of the magnetics. High switching frequency leads to higher losses if conventional hard switching methods are used, this drives the need for soft switching methods without adding to the physical complexity of the system. This dissertation proposes novel soft switching techniques to improve the performance and density of AC/DC and DC/AC converters at high switching frequency without increasing the component count. The concept and the features of this new proposed control scheme, along with the comparison of its benefits as compared to conventional control methodologies, have been presented in detail in different chapters of this dissertation.
38
Khalsa, Harnaak Singh. "Generalised power components definitions for single and three-phase electrical power systems under non-sinusoidal and nonlinear conditions." Monash University. Faculty of Engineering. Department of Electrical and Computer Systems Engineering, 2008. http://arrow.monash.edu.au/hdl/1959.1/42420.
Повний текст джерелаАнотація:
There is a need for generalised definitions of electrical powers to provide a simultaneous common base for measurement, compensation, power quality and identification of source of distortion. The major problem area today is definitions of powers in the presence of harmonics and nonlinear loads in the electrical power system. In such a scenario, there is a problem to accurately measure especially reactive (nonactive) power. This is important for accurate energy billing. Another important area is the mitigation equipment used to remove unwanted polluting quantities from the power system. Definitions of powers have an important role to play in providing the correct information for the optimal design and performance of such equipment. Evaluation of the quality of the power system to enable appropriate allocation costs to those causing deterioration in the power quality also cannot be discounted. To enable this cost allocation, there is a need to identify the polluters and the definitions should indicate degradation in power quality as well as identify the source of this degradation. Finally, it would be very useful if the definitions could also be used to perform a general analysis of the power system. This thesis commenced with investigation of the problem with an in-depth study of the existing definitions, and what other researchers have indicated about this problem, from the definitions perspective. The issues identified with current definitions are that some definitions do not possess the attributes that are related to source-load properties, and others are based on mathematical consideration and lack physical meaning. One issue in measurement of nonactive power is its nature of having zero average value. Another contributing factor is that the presence of source impedance is neglected in definitions. The use of RMS quantities to determine powers, especially instantaneous powers, in the presence of multi-frequency voltages and currents also contributes to the problem. Additionally, RMS based definitions are based on heating effect while not all sourceload relationships are totally of a heating nature. The RMS based definitions also do not satisfy the energy conservation principle. Another issue is that though harmonic currents are used, current definitions still utilise the RMS value of the voltage wave thus losing harmonic information. The solution is to decompose, as accurately as possible, the total instantaneous power into active and nonactive components utilising DC, fundamental and harmonics of voltage and current as well as being based on the power system properties. To enable this, the load model must closely represent the reality. This thesis presents the new instantaneous power definitions to achieve this. In addition to the fundamental, five sub-components for each of the active and nonactive parts are defined. The definitions are based on both the voltage and current DC, fundamental and harmonic components thus retaining harmonic information. Thus these definitions are not only mathematically based but also have a direct relationship with the load. The definitions do not make the assumption of zero source impedance. With good knowledge of the time profile of active and nonactive power components, an accurate time-domain measurement of the active and nonactive power is achieved. The components of powers introduced in the proposed definitions can be utilised to gauge power quality, to identify the source of distortion and to achieve optimal compensation. Based on the new instantaneous power definitions, the definitions for average values of the powers are also proposed. The recognition of positive going and negative going parts of the nonactive power waveform in defining the average nonactive power alleviates the problem of the “zero average nature” of nonactive power. It also retains energy information and satisfies the principle of energy conservation. The new definitions are evaluated for linear and non-linear loads in the presence of harmonics using benchmark case studies. Evaluation results demonstrate good performance of the proposed definitions. The practical applications of the definitions are explored with a number of examples from the areas of measurement of power and energy, compensation, detection of source of distortion and power quality. An application example showing the capability of the definitions in general analysis of a system is also presented. Good and useful results are obtained for all these examples. The proposed definitions are implemented on prototype systems with digital signal processors to demonstrate their practical usability. The proposed definitions are shown to be consistent with the traditional definitions under the conventional sinusoidal conditions, and their relationships to the commonly used existing definitions are also revealed.
39
Du, Toit Daniel Josias. "Predictive control of a series-input, parallel-output, back-to-back, flying-capacitor multilevel converter." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/18087.
Повний текст джерелаАнотація:
Thesis (MScEng (Electrical and Electronic Engineering))--Stellenbosch University, 2011.<br>ENGLISH ABSTRACT: This thesis investigates the viability of constructing a solid-state transformer (SST) with
a series-input, parallel-output connection of full-bridge, three-level
ying-capacitor converters.
It focusses on the active recti er front-end of the SST which is used to control
the input current to be sinusoidal and in-phase with the sinusoidal input voltage. A stack
of two converters are built and tested. The input current, as well as the
ying capacitor
voltages of the two active recti ers in the stack, are actively controlled by a nite-state
model-based predictive (FS-MPC) controller.
The use of multiple
ying-capacitor converters poses a problem when using FS-MPC
because of the large number of possible switching states to include in the prediction
equations. Three FS-MPC control algorithms are proposed to attempt to overcome the
problem associated with the large number of switching states. They are implemented
on an FPGA digital controller. The algorithms are compared on the bases of voltage
and current errors, as well as their responses to disturbances that are introduced into
the system. The simulation and experimental results that are presented shows that by
interleaving the control actions for the two converters, one can obtain fast and robust
responses of the controlled variables. The viability of extending the interleaving control
algorithm beyond two converters is also motivated.<br>AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek die moontlikheid van volbrug, drievlak vlieënde-kapasitoromsetters
wat gebruik word om 'n serie-intree, parallel-uittree drywingselektroniese transformator
(DET) te bou. Dit fokus op die aktiewe gelykrigter van die DET wat gebruik word om
die intreestroom te beheer om sinusvormig en in fase met die sinusvormige intreespanning
te wees. 'n Stapel van twee omsetters word gebou en getoets. Die intreestroom,
sowel as die vlieënde kapasitorspannings van die twee aktiewe gelykrigters in die stapel,
word aktief beheer met behulp van 'n eindige-toestand, model-gebaseerde voorspellende
beheerder (ET-MVB).
Die gebruik van veelvuldige vlieënde-kapasitoromsetters bemoeilik die implementering van
'n ET-MVB-beheerder as gevolg van die groot aantal skakeltoestande wat in die voorspellende
vergelykings in ag geneem moet word. Drie ET-MVB-algoritmes word voorgestel
om te poog om die probleme, wat met die groot aantal skakeltoestande geassosieer word,
te oorkom. Die algoritmes word in 'n FPGA digitale verwerker geïmplementeer. Die
algoritmes word vergelyk op grond van hul stroom- en spanningsfoute, asook hul reaksie
op steurings wat op die stelsel ingevoer word. Die simulasie en praktiese resultate toon
dat, deur die beheeraksies vir die twee omsetters te laat oorvleuel, die gedrag van die beheerde
veranderlikes vinniger en meer robuust is. Die moontlikheid om die oorvleuelende
beheeraksies uit te brei tot meer as twee omsetters word ook gemotiveer.
40
Ingram, David. "An Evaluation of Harmonic Isolation Techniques for Three Phase Active Filtering." Thesis, University of Canterbury. Electrical and Computer Engineering, 1998. http://hdl.handle.net/10092/1260.
Повний текст джерелаАнотація:
Recent advances in power electronics have lead to the wide spread adoption of advanced power supplies and energy efficient devices. This has lead to increased levels of harmonic currents in power systems, degrading the performance of electrical machinery and interfering with telecommunication services. Active filters provide a solution to these problems by compensating for the distorted currents drawn by non-linear loads. Optimal methods for controlling these active filters have been determined by computer simulation and experimental implementation. Methods used for isolating the harmonic content of an unbalanced three phase load current were compared by computer simulations. A technique based on the Fast Fourier Transform (FFT) was developed as part of this work and shown to perform favourably. Notch Filtering, Sinusoidal Subtraction, Instantaneous Reactive Power Theory, Synchronous Reference Frame and Fast Fourier Transform methods were simulated. The methods shown to be suitable for compensation of three phase unbalanced loads were implemented in a Digital Signal Processor to evaluate true performance. These methods were Notch Filtering, Sinusoidal Subtraction, Fast Fourier Transform, and a High Pass Filter based method. A completely digital hysteresis current controller for a three phase active filter inverter has been developed and implemented with a Field Programmable Gate Array. This controller interfaces directly to a digital signal processor and is resistant to electromagnetic interference. Results from the experimental hardware verified that the active filter model used for simulation is accurate, and may be used for further development of harmonic isolation methods. A technique using notch filtering gives the best performance for steady loads, with the FFT based technique giving the most flexible operation for a range of load current characteristics. Novel use of the FFT based harmonic isolation technique allows selective cancellation of individual harmonics, with particular application to multiple shunt filters connected in parallel.
41
Schneider, Jason C., and Neil L. Ebuen. "The potential effects of the Defense Business Board military compensation task groups 2011 recommendations on active-duty service member retirement." Thesis, Monterey, California. Naval Postgraduate School, 2012. http://hdl.handle.net/10945/27899.
Повний текст джерелаАнотація:
Outstanding Thesis<br>Approved for public release; distribution is unlimited<br>In July 2011, the Defense Business Board (DBB) made recommendations to the Secretary of Defense for modernizing the military retirement system. If implemented, the plan would significantly modify military retirement as it has existed since its inception, shifting it from a defined benefit plan to a defined contribution plan. In this study, we compared the current defined benefit retirement plan to a hypothetical, retrospective defined contribution plan using the constraints proposed by the Defense Business Board Military Compensation Task Group. We also gathered service members sentiments about the current military retirement system and proposed changes. This is an important topic because it revealed the potential financial effects on service members retirement savings, and government and departmental challenges should a new retirement system be implemented. In this study, we created a mathematical model to simulate accumulated savings under the proposed defined contribution (DC) plan, and then compared it to the lump-sum equivalent of the existing defined benefit (DB) plan. Our model considered three investment strategies for asset allocation for active-duty personnel (i.e., officer and enlisted) spanning a 20-year career beginning in January 1, 1991, and ending in December 31, 2010. Additionally, our study surveyed active-duty service members assigned to the Naval Postgraduate School and personnel assigned to the II Marines Expeditionary Force. Through the survey, we gathered feedback on service members attitudes toward military retirement, in general, and proposed changes to the military retirement system. For an officer, the model showed that under a DC plan, accumulated savings were only 37.5% of the lump-sum equivalent of total annuities received under the current DB plan. Likewise, for an enlisted service member, this value was 31.9%. The survey showed that an overwhelming majority of service members are in favor of retaining the current DB retirement system, or, if the retirement system must be replaced, doing so gradually.
42
Du, Toit Delyno Johannes. "ATM cash management for a South African retail bank." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/17977.
Повний текст джерелаАнотація:
Thesis (MScEng)--Stellenbosch University, 2011.<br>ENGLISH ABSTRACT: Cash can be seen as a fast moving consumer good. Approaching
cash as inventory within the ATM cash management environment
of a South African retail bank, provided the opportunity to apply
well known industrial engineering techniques to the financial industry.
This led to the application of forecasting, inventory management,
operational research and simulation methods.
A forecasting model is designed to address the multiple seasonalities
and calendar day effects that is prevalent in the demand for cash.
Special days, e.g. paydays, lead to an increase in demand for cash.
The weekday on which the special day falls will also influence the demand.
The multiplicative Holt-Winters method is combined with an
improvised distribution method to determine the demand for cash for
the region and per ATM. Reordering points are calculated and simulated
to form an understanding of the effect this will have on the ATM
network. Direct replenishment and the traveling salesman problem is
applied and simulated to determine the difference in using one or the
other.
Various simulation models are build to test the operational and financial
impact when certain variables are amended. It is evident
that more work is required to determine the optimal combination of
variable values, i.e. forecasting frequency, aggregate forecasting or
individual forecasting, reorder levels, loading levels, lead times, cash
swap or cash add, and the type of transportation method. Each one of
these are a science in itself and cannot be seen (calculated) in isolation
from the other as a change in one can affect the overall operational
efficiency and costs of the ATM network. The thesis proves that significant cost savings is possible, compared to
the current set-up, when applying industrial engineering techniques
to a geographical ATM network within South Africa.<br>AFRIKAANSE OPSOMMING: Kontant kan gesien word as vinnig bewegende verbruikersgoedere.
Deur kontant te benader as voorraad binne die ATM kontant bestuur
omgewing van ’n Suid Afrikaanse kleinhandelsbank, het dit die geleentheid
geskep om bekende bedryfsingenieurstegnieke toe te pas in die
finansiële industrie. Dit het gelei tot die toepassing van vooruitskatting,
voorraadbestuur, operasionele navorsing en simulasie metodes.
’n Vooruitskattingsmodel is ontwerp om die verskeie seisoenaliteite
en kalenderdae effekte wat deel uitmaak van die vraag na kontant
aan te spreek. Spesiale dae, bv. betaaldae, lei tot ’n toename in die
vraag na kontant. Die weeksdag waarop die spesiale dag voorkom
sal ook ’n invloed hê op die vraag. Die multiplikatiewe Holt-Winters
metode is gekombineer met ’n geïmproviseerde verspreidingsmetode
om die vraag na kontant vir die streek en per ATM the bepaal.
Bestellingsvlakke is bereken en gesimuleer om ’n prentjie te skep van
die invloed wat dit op die ATM netwerk sal hê. Direkte hervulling en
die handelsreisigerprobleem is toegepas en gesimuleer om die verskille
te bepaal tussen die gebruik van of die een of die ander.
Veskeie simulasie modelle is gebou om die operasionele en finansiële
impak te toets, wanneer sekere veranderlikes aangepas word. Dit is
duidelik dat meer werk nodig is om die optimale kombinasie van veranderlike
waardes te bepaal, bv. vooruitskatting frekwensie, totale
vooruiskatting of individuele vooruitskatting, bestellingsvlakke, leitye,
kontant omruiling of kontant byvoeging, en die tipe vervoermetode.
Elkeen van hierdie is ’n wetenskap op sy eie en kan nie in isolasie gesien
en bereken word nie, want ’n verandering van een se waarde kan die
hele operasionele doeltreffendheid en kostes van die ATM netwerk
beïnvloed.
43
Xue, Kai. "Modal filtering for active control of floor vibration under impact loading." Kyoto University, 2018. http://hdl.handle.net/2433/232024.
Повний текст джерела
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Wang, Lei. "Design and implementation of a three-phase three-wire thyristor controlled LC-coupling hybrid active power filter with low dc-link voltage and wide compensation range." Thesis, University of Macau, 2017. http://umaclib3.umac.mo/record=b3691876.
Повний текст джерела
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Barka, Noureddine. "Développement d'un système de mesure en temps réel des erreurs dans les machines-outils à axes multiples pour une compensation active." Thèse, [Rimouski, Québec] : Université du Québec à Rimouski, 2005.
Знайти повний текст джерелаАнотація:
Thèse (M. Sc.) - Université du Québec à Rimouski, 2005.<br>Titre de lʹécran-titre (visionné le 31 août 2006). Mémoire présenté à l'Université du Québec à Rimouski comme exigence partielle du programme de maîtrise en ingénierie. Comprend un résumé. CaQRU CaQRU CaQRU Bibliogr.: f. 97-99. Paraît aussi en éd. imprimée. CaQRU
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Zafeiropoluos, Andreas. "An MMC-based topology with Dual-Active-Bridge power channels for load balancing in 50 Hz-railway applications." Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-201656.
Повний текст джерелаАнотація:
The purpose of this thesis report is to investigate challenges related to railway electrification. Inac-railway systems, trains are most often single-phase loads, which can create significantunbalances in the grid, when fed directly from two adjacent phases. To enhance power quality atthe railway feeding point, one alternative is to design the system such as the power is fed to thecatenary through Static Frequency Converters (SFCs), which can be a costly solution. Anotheroption is to use Static Compensators (STATCOMs) in shunt connections, handling only theunbalanced amount of power, in order to symmetrize the railway load as seen from the grid side.Modular multilevel converters (MMCs) are the state of the art solutions for medium- and highvoltage/power converter applications, such as load balancing and reactive-power compensation.This project will focus on analyzing Modular Multilevel Converter (MMC) topologies to be usedas load balancers in railway systems. However, the specific requirements of this application reveala potential weakness of MMCs. That is the asymmetrical character of the load may require muchhigher device rating in an MMC compared to a conventional converter, due to the symmetrizingcomponents to rebalance the capacitor voltages in the submodules.This project analyzes a reduced MMC-based topology with only two branches in order to meet therailway load-balancing characteristics. This chain-link compensator uses dc-dc converters tofacilitate power channels in order to restore the power imbalance, without overrating thesemiconductors in the main current path.<br>Syftet med detta examensarbete är att studera de svårigheter som elektrifierade järnvägar står inför.När systemet utgörs av växelström kan tågen ses som en enfas last, vilket kan skapa avsevärdaobalanser i nätet då det matas från två intilliggande faser. En alternativ systemdesign för att uppnåen god effekt leverans uppnås då effekten är matad till kontaktledningen genom statiska frekvensomräknare (SFCs), detta kan dock vara en kostsam lösning. Ett annat alternativ är att användastatisk shunt kompensation (STATCOMs) som selektivt kan hantera den obalanserade effekten föratt uppnå symmetri och balans i järnvägslasten, sett från nätets sida.Modulära multiomriktare (MMCs) är en ledande teknik för omriktare till applikationer på mellanochhögspännings nivå, till exempel för lastbalans och reaktiv kompensering. Detta projektanalyserar modulära multiomriktare för lastbalansering i järnvägssystem. Kraven för dennaapplikation leder till en potentiell svaghet i MMCs där den asymmetriska karaktären på lastenkräver högre märkeffekt jämfört med konventionella omriktare. Detta på grund av de komponentersom återskapar symmetri och balans i kondensator spänningarna i submodulerna.Här analyseras en reducerad variant av MMC-baserad topologi med enbart två grenar för att mötakraven på järnvägens lastbalans. Denna kedjelänk-kompensator använder dc-dc omriktare för attstyra effektflödet till lasten vid obalanserad effekt, utan att för den skull överdimensionerahalvledarna i den ordinarie strömvägen.
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Mérad, Manelle. "Investigations on upper limb prosthesis control with an active elbow." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066615/document.
Повний текст джерелаАнотація:
Les progrès de la mécatronique ont permis d’améliorer les prothèses du membre supérieur en augmentant le catalogue des mouvements prothétiques. Cependant, un fossé se creuse entre les capacités technologiques de la prothèse et leur méthode de contrôle. La commande myoélectrique, qui est la méthode la plus répandue, reste complexe, notamment pour les personnes amputées au niveau trans-huméral qui peuvent avoir un coude actif en plus de la main et du poignet motorisés. Une approche intéressante consiste à utiliser la mobilité du membre résiduel, présente chez la plupart des amputés trans-huméraux, pour contrôler des articulations prothétiques distales comme le coude. Les mouvements du coude sont couplés aux mouvements du membre résiduel selon un modèle de coordination épaule/coude saine. Cette thèse étudie une stratégie de commande d’un coude prothétique utilisant les mouvements du membre résiduel, mesuré par des centrales inertielles, et nos connaissances du contrôle moteur humain. Pour cela, un modèle de la coordination épaule/coude a été construit à partir d’enregistrements de gestes sains de préhension. Ce modèle, implémenté sur un prototype de prothèse, a été testé par 10 individus sains équipés du prototype afin de valider le concept, puis par 6 personnes amputées. Ces dernières ont aussi réalisé la tâche avec une commande myoélectrique conventionnelle afin de comparer les résultats. La commande couplant automatiquement les mouvements de l’épaule et du coude s’est montrée satisfaisante en termes de facilité d’utilisation et de réduction des stratégies de compensation<br>Progress in mechatronics has enabled the improvement of upper limb prosthetics increasing the grasps catalog. However, a gap has been growing between the prosthesis technological possibilities and the methods to control it. Indeed, common myoelectric control strategy remains complex, especially for transhumeral amputees who can have an active elbow in addition to a prosthetic wrist and hand. Since most transhumeral amputees have a mobile residual limb, an interesting approach aims at utilizing this mobility to control intermediate prosthetic joints, like the elbow, based on the shoulder/elbow coordination observed in healthy movements. This thesis investigates the possibility of controlling an active prosthetic elbow using the residual limb motion, measured with inertial measurement units, and knowledge of the human motor control. A primary focus has been targeting the reaching movement for which a model has been built using regression tools and kinematic data from several healthy individuals. The model, implemented on a prosthesis prototype, has been tested with 10 healthy participants wearing the prototype to validate the concept, and with 6 amputated individuals. These participants also performed the task with a conventional myoelectric control strategy for comparison purpose. The results show that the inter-joint coordination-based control strategy is satisfying in terms of intuitiveness and reduction of the compensatory strategies
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Hamed, Ibrahim. "Comparison between Active and Passive AC-DC Converters For Low Power Electromagnetic Self-Powering Systems : A theoretical and experimental study of low power AC-DC converters." Thesis, Mittuniversitetet, Institutionen för elektronikkonstruktion, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-39600.
Повний текст джерелаАнотація:
Electromagnetic based energy harvesting systems such as Variable reluctance energy harvesting systems (VREH) have shown to be an effective way of extracting the energy of rotating parts. The transducer can provide enough power to run an electronic sensing system, but the problem arises in finding an efficient way of rectifying that power to generate a stable energy supply to run a system, which this report will investigate. Active and passive voltage doublers have proven to be a suitable candidate in solving this issue due to the simplicity and the small footprint. This thesis will aim to compare active and passive voltage doublers under various scenarios in order to understand under which circumstances are active or passive voltage doublers to be preferred. From the conducted experimental measurements, this thesis concluded that active voltage doublers are recommended during high RPMs (>10 RPM) while passive voltage doublers (especially fullwave voltage doubler) is recommended at lower RPMs. Quality of power also plays a significant role in this study. Therefore, measurements have also been done for ripple and rise time. From the measurements, this thesis can conclude that the overall power quality was the best in Full-wave voltage doublers, while Active-voltage doublers had lower ripple than FWVDs at higher current loads.
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Wang, Yu. "Tunable C Band Coupled-C BPF with Resonators Using Active Capacitor and Inductor." Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1472479817.
Повний текст джерела
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Zhang, Yigong. "ACTIVE CURRENT INJECTION METHOD FOR LIMITING GROUND FAULT CURRENT HARMONICS IN UNDERGROUND COAL MINES." UKnowledge, 2014. http://uknowledge.uky.edu/mng_etds/15.
Повний текст джерелаАнотація:
Current practice in U.S. underground coal mine high-voltage distribution systems is to attempt to limit ground fault current to 25 Amperes and de-energize the circuit at 10 Amperes. However, the significant amount of system capacitance due to the use of shielded cables can cause ground fault current to be two or three times the intended ground fault limit. Consequently, this practice can cause several issues such as ground fault currents significantly exceeding the neutral grounding resistor current limit, loss of relay selectivity in the distribution system, and transient overvoltages in certain ground fault situations. These issues are solved to some extent by using a resonance grounded system, currently used in some other countries. However, a shortcoming of traditional resonance grounded systems is the inability to deal with the harmonic components existing in ground fault current. With the increasing use of nonlinear sources such as variable frequency drives, the proportion of harmonic components in ground fault current can be significant. Consequently, although the fundamental component can be almost fully compensated in a traditional resonance grounded system, the harmonic components can still be large enough to maintain arcing and cause personal injury and equipment damage. In this dissertation, a novel method is developed to perform real-time prediction of the harmonics in ground fault currents. Methods for neutralizing the ground fault current harmonics and identifying ground fault location are also developed. Results indicate that the combination of traditional high-resistance grounding and active current injection to neutralize harmonics in the ground fault has the potential to significantly reduce the total ground fault current and reduce arc and flash hazards during ground faults in high voltage distribution systems.