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1
Mayes, Peter Richard. "A novel AC/DC bidirectional power converter". Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239439.
Testo completo
2
Ahmad, Khan Naveed. "Power Loss Modeling of Isolated AC/DC Converter". Thesis, KTH, Elektrisk energiomvandling, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-109717.
Testo completoAbstract (sommario):
Several research activities at KTH are carried out related to Isolated AC/DC converters in order to improve the design and efficiency. Concerning the improvement in the mentioned constraints, losses of the elements in the prototype converter are modeled in this thesis work. The obtained loss model is capable of calculating the losses under different circumstances. The individual contribution of losses for each element at different conditions can be obtained, which is further useful in improving the design and therefore, efficiency. The losses in different elements of the converter, including power semiconductor devices, RC-snubbers, transformer and filter inductor at different operating points can be computed by using the obtained model. The loss model is then validated by comparing the analytical results with the measurements. The results based on developed loss model show consistency with the measured losses. The comparison at different conditions shows that, the difference between measured and analytical results ranges between 10% to 20 %. The difference is due to those losses which are disregarded because of their negligible contribution. On the other hand, it is also observed that if the neglected losses are counted, the difference reduces up to 10%.
3
Wang, Kunrong. "High-Frequency Quasi-Single-Stage (QSS) Isolated AC-DC and DC-AC Power Conversion". Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/29394.
Testo completoAbstract (sommario):
The generic concept of quasi-single-stage (QSS) power conversion topology for ac-dc rectification and dc-ac inversion is proposed. The topology is reached by direct cascading and synchronized switching of two variety of buck or two variety of boost switching networks. The family of QSS power converters feature single-stage power processing without a dc-link low-pass filter, a unidirectional pulsating dc-link voltage, soft-switching capability with minimal extra commutation circuitry, simple PWM control, and high efficiency and reliability.
A new soft-switched single-phase QSS bi-directional inverter/rectifier (charger) topology is derived based on the QSS power conversion concept. A simple active voltage clamp branch is used to clamp the otherwise high transient voltage on the current-fed ac side, and at the same time, to achieve zero-voltage-switching (ZVS) for the switches in the output side bridge. Seamless four-quadrant operation in the inverter mode, and rectifier operation with unity power factor in the charger (rectifier) mode are realized with the proposed uni-polar center-aligned PWM scheme. Single-stage power conversion, standard half-bridge connection of devices, soft-switching for all the power devices, low conduction loss, simple center-aligned PWM control, and high reliability and efficiency are among its salient features. Experimental results on a 3 kVA bi-directional inverter/rectifier prototype validate the reliable operation of the circuit. Other single-phase and three-phase QSS bi-directional inverters/rectifiers can be easily derived as topological extensions of the basic QSS bi-directional inverter/rectifier.
A new QSS isolated three-phase zero-voltage/zero-current-switching (ZVZCS) buck PWM rectifier for high-power off-line applications is also proposed. It consists of a three-phase buck bridge switching under zero current and a phase-shift-controlled full-bridge with ZVZCS, while no intermediate dc-link is involved. Input power and displacement factor control, input current shaping, tight output voltage regulation, high-frequency transformer isolation, and soft-switching for all the power devices are realized in a unified single stage. Because of ZVZCS and single-stage power conversion, it can operate at high switching frequency while maintaining reliable operation and achieving higher efficiency than standard two-stage approaches. A family of isolated ZVZCS buck rectifiers are obtained by incorporating various ZVZCS schemes for full-bridge dc-dc converters into the basic QSS isolated buck rectifier topology. Experimental and simulation results substantiate the reliable operation and high efficiency of selected topologies.
The concept of charge control (or instantaneous average current control) of three-phase buck PWM rectifiers is introduced. It controls precisely the average input phase currents to track the input phase voltages by sensing and integrating only the dc rail current, realizes six-step PWM, and features simple implementation, fast dynamic response, excellent noise immunity, and is easy to realize with analog circuitry or to integrate. One particular merit of the scheme is its capability to correct any duty-cycle distortion incurred on only one of the two active duty-cycles which often happens in the soft-switched buck rectifiers, another merit is the smooth transition of the input currents between the 60o sectors. Simulation and preliminary experimental results show that smooth operations and high quality sinusoidal input currents in the full line cycle are achieved with the control scheme.Ph. D.
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Perera, Lasantha Bernard. "Multi Level Reinjection ac/dc Converters for HVDC". Thesis, University of Canterbury. Electrical and Computer Engineering, 2006. http://hdl.handle.net/10092/1085.
Testo completoAbstract (sommario):
A new concept, the multi level voltage/current reinjection ac/dc conversion, is described in this thesis. Novel voltage and current source converter configurations, based on voltage and current reinjection concepts are proposed. These converter configurations are thoroughly analyzed in their ac and dc system sides. The fundamentals of the reinjection concept is discussed briefly, which lead to the derivation of the ideal reinjection waveform for complete harmonic cancellation and approximations for practical implementation. The concept of multi level voltage reinjection VSC is demonstrated through two types of configurations, based on standard 12-pulse parallel and series connected VSC modified with reinjection bridges and transformers. Firing control strategies and steady state waveform analysis are presented and verified by EMTDC simulations. The multi level current reinjection CSC is also described using two configurations based on standard 12-pulse parallel and series connected CSC modified with associated reinjection circuitry. Firing control strategies and steady state waveform analysis are presented and verified by EMTDC simulations. Taking the advantage of zero current switching in the main bridge valves, achieved through multi level current reinjection, an advanced multi level current reinjection scheme, consisting thyristor main bridges and self-commutated reinjection circuitry is proposed. This hybrid scheme effectively incorporates self-commutated capability into a conventional thyristor converter. The ability of the main bridge valves to commutate without the assistance of a turn-off pulse or line commutating voltage under the zero current condition is explained and verified by EMTDC simulations. Finally, the applications of the MLCR-CSC are discussed in terms of a back to back HVDC link and a long distance HVDC transmission system. The power and control structures and closed loop control strategies are presented. Dynamic simulation is carried out on PSCAD/EMTDC to demonstrate the two systems ability to respond to varying active and reactive power operating conditions.
5
Stejskal, Jiří. "Měnič 12V DC/230V AC". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218761.
Testo completoAbstract (sommario):
This diploma thesis describes particular parts of power inverter such as gate driver, DSC, LC filter, low power supply, DC/DC converter and four-quadrant bridge and manner of its control by digital signal controller. Inverter is designated for generating of a mobile artificial electric grid (for example in a car).
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You, Keping Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "A new bidirectional AC-DC converter using matrix converter and Z-source converter topologies". Awarded by:University of New South Wales, 2007. http://handle.unsw.edu.au/1959.4/37450.
Testo completoAbstract (sommario):
This thesis proposes a new bidirectional three-phase AC-DC power converter using matrix converter and Z-source inverter topologies. Advantages of the AC-DC matrix converter are the inherently controllable power factor, the tight DC voltage regulation, the wide bandwidth with quick response to load variation, the single-stage buck-voltage AC-to-DC power conversion; advantages of the z-source inverter are the increased reliability by allowing the shoot-through between upper and lower power switches of one inverter leg, insensitivity to DC bus voltage due to the extra freedom of controlling DC-link voltage. The proposed Matrix-Z-source converter (MZC) marries up both advantages of AC-DC matrix converter and Z-source inverter. It can achieve voltage-boost DC-AC inversion capable of variable voltage variable frequency (VVVF) AC output; it can achieve voltage-buck AC-DC rectification capable of inherent control over AC current phase angle and DC output regulation with a (VVVF) AC source supply. Both foresaid performance in DC-AC inversion and AC-DC rectification can be implemented in a simple open-loop control manner. Three constraints of VSI, in the bidirectional AC-DC power conversion, are the peak AC voltages are always less than DC-link voltage, closed-loop control has to be employed when DC regulation and/or AC current phase angle control are required, and AC voltage is sensitive to the variation of the DC-link voltage in DC-AC inversion. The voltage-boost inversion and/or voltage-buck rectification of MZC overcomes the first constraint; thus MZC enables the AC machine voltage increased higher than DC-link voltage hence advantages of running AC machine at relatively high voltages are enabled. The direct DC voltage regulation and inherent AC-current-phase-angle control of MZC overcomes the second constraint in an open-loop manner; hence a simplified system design is obtained with sufficient room for the further improvement by closed-loop control schemes. The extra freedom in controlling DC-link voltage of MZC overcomes the third constraint hence a DC source voltage adaptable inverter is obtained. This thesis focuses on the study of the feasibility of the proposed MZC through theoretical analysis and experimental verification. At first, the proposed MZC is conceptually constructed by examining the quadrant operation of AC-DC matrix converter and Z-source inverter. After the examination of the operating principles of both AC-DC matrix converter and Z-source inverter, the configuration of MZC is then proposed. The MZC has two operating modes: DC-AC inversion and AC-DC rectification. Circuit analysis for both operating modes shows that the new topology does not impose critical conflict in circuit design or extra restriction in parameterization. On the contrary, one version of the proposed MZC can make full advantage of Z-source network components in both operating modes, i.e. a pair of Z-source inductor and capacitor can be used as low-pass filter in AC-DC rectification. The modulation strategy, average modeling of system, and features of critical variables for circuit design of the proposed MZC were examined for each operating mode. Simulations of the proposed MZC and its experimental verification have been presented. Analytical models of conduction and switching losses of the power-switch network in different operating mode have shown that the losses in the MZC compare favorably with conventional VSI for a range of power factor and modulation indices.
7
Chewele, Youngie Klyv. "Model predictive control of AC-to-AC converter voltage regulator". Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86339.
Testo completoAbstract (sommario):
Thesis (MEng)--Stellenbosch University, 2014.ENGLISH ABSTRACT: The development of fast and efficient processors, programmable devices and high power semiconductors has led to the increased use of semiconductors directly in the power supply path in order to achieve strict power quality standards. New and advanced algorithms are used in the process and calculated on-line to bring about the required fast response to voltage variations. Losses in high voltage semiconductors increase with increased operating frequencies. A balance between semiconductor power losses and power quality is achieved through control of power semiconductor switching frequencies. A predictive control algorithm to achieve high power quality and limit the power losses in the high power semiconductor switches through switching frequency control is discussed for a tap switched voltage regulator. The quality of power, voltage regulator topology and the control algorithm are discussed. Simulation results of output voltage and current are shown when the control algorithm is used to control the regulator. These results are verified by practical measurements on a synchronous buck converter.
AFRIKAANSE OPSOMMING: Die ontwikkeling van vinnige en doeltreffende verwerkers, programmeerbare toestelle en hoëdrywings halfgeleiers het gelei tot 'n groter gebruik van halfgeleiers direk in die kragtoevoer pad om streng elektriese toevoer kwaliteit standaarde te bereik. Nuwe en gevorderde algoritmes word gebruik in die proses en word aan-lyn bereken om die nodige vinnige reaksie tot spanningswisselinge te gee. Verliese in hoë-spannings halfgeleiers verhoog met hoër skakel frekwensies. 'n Balans tussen die halfgeleier drywingsverliese en spanningskwalteit is behaal deur die skakel frekwensie in ag te neem in die beheer. 'n Voorspellinde-beheer algoritme om ‘n hoë toevoerkwaliteit te bereik en die drywingsverliese in die hoëdrywingshalfgeleier te beperk, deur skakel frekwensie te beheer, is bespreek vir 'n tap-geskakelde spanning reguleerder. Die toevoerkwaliteit, spanningsreguleerder topologie en die beheer algoritme word bespreek. Simulasie resultate van die uittree-spanning en stroom word getoon wanneer die beheer algoritme gebruik word om die omsetter te beheer. Hierdie resultate is deur praktiese metings op 'n sinkrone afkapper.
8
Mino, Kazuaki. "Novel hybrid unidirectional three-phase AC-DC converter systems /". [S.l.] : [s.n.], 2009. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=18185.
Testo completo
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Daniele, Matteo. "A single-stage power factor corrected AC/DC converter". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0018/MQ39474.pdf.
Testo completo
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Trubitsyn, Aleksey. "High efficiency DC/AC power converter for photovoltaic applications". Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/60190.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.Includes bibliographical references (p. 217-218).
This thesis presents the development of a microinverter for single-phase photovoltaic applications that is suitable for conversion from low-voltage (25-40V) DC to high voltage AC (e.g. 240VAC,RMS). The circuit topology is based on a full-bridge series resonant inverter, a high-frequency transformer, and a novel half-wave cyclo-converter. The operational characteristics are analyzed, and a multidimensional control technique is utilized to achieve high efficiency, encompassing frequency control and inverter and cyclo-converter phase shift control. An experimental prototype is demonstrated in DC/DC conversion mode for a wide range of output voltages. The proposed control strategy is shown to allow for accurate power delivery with minimal steps taken towards correction. The prototype achieves a CEC averaged efficiency of approximately 95.1%. Guidelines for optimization are presented along with experimental results which validate the method.
by Aleksey Trubitsyn.
S.M.
11
Santos, Heron Alves dos. "Design of a controlled single-phase ac-dc converter for interconnection of DC and AC buses of a microgrid". Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=12977.
Testo completoAbstract (sommario):
The recent growth expectation of the participation of solar-photovoltaic energy sources in the power generation matrix has significantly increased the number of grid-connected systems. For connection to power grid, it is essential to use a dc-ac converter, which is able to suit the characteristics of the power provided by the photovoltaic modules to grid parameters. This dissertation presents a project proposal of a 2 kW single phase dc-ac converter for connecting a 311 V dc bus to a 220 Vrms ac bus of a microgrid. The proposed converter is bidirectional and allows, when necessary, the power flow from ac to dc bus. The study shows, through simulation and prototype implementation in the laboratory, that with the application of an appropriate control strategy it is possible to control the direction of power flow, as well as properly modulating the current flowing between two buses, dc, powered by photovoltaic panels and the battery bank, and the ac, at grid side. The prototype had a yield of about 91% and has injected electric current with low harmonic content (THDi less than 5%).A recente expectativa de crescimento da participaÃÃo da energia solar-fotovoltaica na matriz de geraÃÃo de energia elÃtrica aumentou significativamente o nÃmero de conexÃes desses sistemas à rede elÃtrica. Para que a interligaÃÃo com a rede elÃtrica convencional seja possÃvel, à indispensÃvel a utilizaÃÃo de conversores CC/CA, capazes de adequar as caracterÃsticas da energia disponibilizada pelos mÃdulos fotovoltaicos aos padrÃes da rede. Esta dissertaÃÃo apresenta uma proposta de projeto de conversor CC/CA de 2 kW para conexÃo de dois barramentos de uma microrrede, um CC em 311 V e outro CA em 220 Vrms. O conversor proposto à bidirecional e permite, quando necessÃrio, o fluxo de energia elÃtrica do barramento CA para o CC. O estudo realizado mostra, atravÃs de simulaÃÃes e de implementaÃÃo de protÃtipo em laboratÃrio, que com a aplicaÃÃo de uma estratÃgia de controle adequada à possÃvel controlar o sentido do fluxo de potÃncia do conversor, assim como modular apropriadamente a corrente que flui entre dois barramentos, o CC, alimentado por painÃis fotovoltaicos e por banco de baterias, e o barramento CA, do lado da rede elÃtrica. O protÃtipo desenvolvido apresentou rendimento de cerca de 91% e forneceu corrente elÃtrica de baixo conteÃdo harmÃnico (THDi menor que 5%).
12
Shen, Jian. "GTO Pulsed Width Modulated (PWM) converter for railway traction applications". Thesis, University of Salford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308484.
Testo completo
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MARCIANO, Daniele. "Analysis of Multistage DC/AC converter based on Pulsating DC link principle". Doctoral thesis, Università degli studi di Cassino, 2022. https://hdl.handle.net/11580/90998.
Testo completoAbstract (sommario):
Nowadays the different application fields of the Power Electronics and the industries are demanding incessant enhancements of the features of power converter as efficiency, reliability and power density. To answer to this request, the researchers are pushing the limits of these features thanks to the growing use of Wide band-gap (WBG) power devices, new improvements in the field of power magnetics and new topologies of converter. The aim of this thesis is present the results of complete analysis of new topology of insulated DC/AC converter, based on the Pulsating DC link principle. A preliminary study of the topologies used in the field of multistage isolated DC/AC converter is presented, focusing the attention on the solutions based on Fixed DC link and the new architectures based on topology innovations and particular design. In particular in the horizon of the novel and innovative DC/AC insulated topologies, the attention was focalized on the Pulsating DC link Converter (PDLC), reliable architecture featured by pulsating evolution of the DC link thanks to the elimination of the intermediate filter. A novel version of the PDLC topology is presented, highlighting the interesting feature of the Zero Voltage Transition (ZVT) of the VSI stage, thanks to an accurate use of the pulsating DC link. Moreover it has been demonstrated how the action of Active Clamp circuit is strictly necessary, to minimize the overvoltage problem on the DC link voltage and manage the overvoltage associated energy. Successively a complete analysis of the proposed topology during the energising phases is reported, showing the equivalent representation of the PDLC and the relative differential equation system. According to this results a multiparametric analysis of the converter is performed, using accurate LTspice simulations, for different combinations of influence parameters. Thanks to this analysis, the design guidelines for the main components of the converter, as transformer and Active Clamp circuit, have been defined. Regarding the modulation techniques for this topology, a complete overview of the different operating principles is presented as well as the review of the techniques presented in literature. The attention has been focused on the techniques based on the ZVT of the inverter stage, since they permit the reduction of the switching losses of this stage. Specifically two different modulation techniques based on the described principle are presented, showing the different operating principles and the relative implementations. The main difference between the two techniques is the relationship between the switching frequencies of the main power stages, that is a fundamental aspect in PDLC topology and influences the features of the modulation technique. To validate the analytical analysis and simulation results, a 30kW prototype of proposed PDLC topology has been implemented and the main details of the implementation are provided. To conclude the thesis, the prototype was fully characterized on resistive load and the principal results are presented, highlighting the ZVT of the Inverter stage and the results achieved with the two different modulation techniques.
14
Steckler, Pierre-Baptiste. "Contribution à la conversion AC/DC en Haute Tension". Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI075.
Testo completoAbstract (sommario):
Le courant alternatif (AC) se prêtant bien à la majorité des problématiques de production, de transport et de distribution de l'électricité, on comprend qu'il soit massivement utilisé. Cependant, depuis plus d'un siècle, les bénéfices du courant continu haute tension (HVDC, pour High Voltage Direct Current) pour les longues distances sont bien connus. Aux interfaces, des convertisseurs AC/DC sont requis, leur composition évoluant au fil des avancées technologiques. Après avoir présenté les spécificités du HVDC et les contraintes qu'il introduit sur les convertisseurs AC/DC, ce manuscrit se focalise sur trois topologies : Modular Multilevel Converter (MMC), Alternate Arm Converter (AAC) et Series Bridge Converter (SBC). Elles sont présentées, dimensionnées et analysées en détail, puis comparées de façon quantitative en utilisant des indicateurs de performance originaux. Il en ressort que le MMC et le SBC sont particulièrement intéressants. La méthode de commande conventionnelle du MMC est ensuite présentée et ses propriétés structurelles sont mises en évidence. Une première loi de commande originale est présentée, avec des performances similaires mais une complexité inférieure à l'état de l'art. La seconde est non linéaire, basée sur la théorie de la platitude différentielle, et permet un suivi de puissance très rapide tout en assurant la stabilité exponentielle globale du système. Ces lois de commande sont évaluées en simulation, avec un modèle moyen et un modèle détaillé intégrant 180 sous-modules par bras. La dernière partie concerne le SBC. Après l'avoir modélisé, des résultats concernant une analyse structurelle de la topologie sont présentés ainsi qu'une loi de commande originale. Le rôle fondamental du transformateur pour les convertisseurs à structure série comme le SBC est souligné. Enfin, les performances de la loi de commande proposée sont testées en simulationAs Alternating Current (AC) is well suited for most of the production, transmission, and distribution applications, its massive use is easy to understand. However, for over a century, the benefits of High Voltage Direct Current (HVDC) for long-distance energy transmission are well known. To connect both, AC/DC converters are mandatory, whose nature evolves with technological progress. After the problematic induced by HVDC on AC/DC converters is presented, this manuscript is focused on three topologies: Modular Multilevel Converter (MMC), Alternate Arm Converter (AAC) and Series Bridge Converter (SBC). They are presented, sized, analyzed thoroughly, and compared in quantitative terms, using original key performance indicators. It appears that MMC and SBC are particularly promising. The conventional control method of the MMC is then presented, and its structural properties are highlighted. A first original control law is presented, with similar performances but less complexity than the state-of-the-art. A second control law, non-linear and based on differential flatness theory, is introduced. It allows a very fast power tracking response while ensuring the global exponential stability of the system. These control laws are tested in simulation, using an average model and a detailed model with 180 sub-modules per arm. The last part is dedicated to the SBC. After a modeling step, some results regarding its structural analysis are presented, and an original control law is introduced. The essential role of the transformer for series converters like the SBC is highlighted. Finally, the performance of the proposed control law is assessed in simulation
15
Yang, Xiaoguang Miu Karen Nan. "Unbalanced power converter modeling for AC/DC power distribution systems /". Philadelphia, Pa. : Drexel University, 2006. http://hdl.handle.net/1860/1231.
Testo completo
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Gitau, Michael N. "Optimal PWM switching strategy for single-phase AC-DC converters". Thesis, Loughborough University, 1994. https://dspace.lboro.ac.uk/2134/7205.
Testo completoAbstract (sommario):
The thesis describes an optimal selective harmonic elimination strategy suitable for singlephase AC-DC converter-fed traction drives. The objective is to eliminate low-order supply current harmonics, including those injected into the supply due to load-side current ripple. Other advantages that the switching strategy has to offer over phase-control include improved supply power factor, reduced VA consumption for a given demand speed and load, reduced torque and speed ripple and smaller armature circuit smoothing inductance. The effect of field current boost on the dynamic response of the drive is also described. It is shown that field boost helps to reduce the speed rise-time by increasing the electromagnetic torque available during acceleration periods. Closed-loop control of a 4-quadrant DC drive is described and a comparison made between the performance of PID-control and pseudo-derivative feedback control. It is shown that pseudo-derivative feedback control has several advantages to offer, amongst which are ease of tuning of the controller gains and a superior performance following load torque disturbances. A laboratory size drive system was designed and built, and used to validate simulation predictions for both the switching strategy and pseudo-derivative feedback control. A microcontroller based hardware implementation of both the switching strategy and a digital pseudo-derivative feedback controller was adopted, with the switching strategy being implemented using an off-line approach of precalculating the switching angles and storing these in look-up tables. The armature voltage controller comprises a dual-converter employing IGBTs as switching devices. The use of IGBTs allows higher switching frequencies at significant power levels than would be possible if GTOs were used. It also simplifies the gate drive circuit design and minimises the need to use snubber circuits.
17
Jassim, Bassim M. H. "Active current sharing control schemes for parallel connected AC/DC/AC converters". Thesis, University of Newcastle upon Tyne, 2014. http://hdl.handle.net/10443/3086.
Testo completoAbstract (sommario):
The parallel operation of voltage fed converters can be used in many applications, such as aircraft, aerospace, and wind turbines, to increase the current handling capability, system efficiency, flexibility, and reliability through providing redundancy. Also, the maintenance of low power parallel connected units is lower than one high power unit. Significant performance improvement can be attained with parallel converters employing interleaving techniques where small passive components can be used due to harmonic cancellation. In spite of the advantages offered by parallel connected converters, the circulating current problem is still a major concern. The term circulating current describes the uneven current sharing between the units. This circulating current leads to: current distortion, unbalanced operation, which possibly damages the converters, and a reduction in overall system performance. Therefore, current sharing control methods become necessary to limit the circulating current in a parallel connected converter system. The work in this thesis proposes four active current sharing control schemes for two equally rated, directly paralleled, AC/DC/AC converters. The first scheme is referred to as a “time sharing approach,” and it divides the operation time between the converters. Accordingly, in the scheme inter-module reactors become unnecessary, as these are normally employed at the output of each converter. However, this approach can only be used with a limited number of parallel connected units. To avoid this limitation, three other current sharing control schemes are proposed. Moreover, these three schemes can be adopted with any pulse width modulation (PWM) strategy and can be easily extended to three or more parallel connected units since they employ a modular architecture. The proposed current sharing control methods are employed in two applications: a current controller for three-phase RL load and an open loop V/f speed control for a three-phase induction motor. The performance of the proposed methods is verified in both transient and steady state conditions using numerical simulation and experimental testing.
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Alsolami, Mohammed Faham. "Wide Bandgap (WBG) Devices Based Switched Capacitor Multiport Multilevel SinglePhase AC/DC/AC Converter for UPS Applications". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461327268.
Testo completo
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Ismail, Nasser. "A single stage full bridge power factor corrected AC/DC converter". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq26004.pdf.
Testo completo
20
LI, QIANG. "A SINGLE-PHASE DUAL-OUTPUT AC-DC CONVERTER WITH HIGH QUALITY INPUT WAVEFORMS". UKnowledge, 2003. http://uknowledge.uky.edu/gradschool_theses/242.
Testo completoAbstract (sommario):
A single-phase, buck-boost based, dual-output AC-DC converter is studied in this thesis. The converter has two DC outputs with opposite polarities, which share the same ground with the input power line. The power stage performance, including the input filter, is studied and procedure to select power components is given. The circuit model is analyzed to develop appropriate control. Zerocrossing distortion of the source input current is addressed and a solution is proposed. Experimental results are satisfactory in that a high power factor line current results for steady-state operation.
21
Bulhosa, João Paulo Rodrigues. "Controlo de um conversor AC-DC-AC para turbinas eólicas baseadas no PMSG". Master's thesis, Instituto Politécnico de Bragança, Escola Superior de Tecnologia e de Gestão, 2009. http://hdl.handle.net/10198/2062.
Testo completoAbstract (sommario):
A dissertação teve como objectivo o estudo e implementação do controlo de um conversor AC-DC-AC, constituído por um conversor DC/DC elevador e um inversor de tensão monofásico, para efectuar a ligação à rede de turbinas eólicas baseadas no gerador síncrono de ímanes permanentes.
O controlo global do conversor AC-DC-AC seguiu uma estratégia na qual o controlo do conversor elevador e do inversor de tensão monofásico é implementado de modo independente. O primeiro visa maximizar a potência extraída da turbina através da implementação de um algoritmo de seguimento do ponto de potência máxima (MPPT), enquanto o segundo tem a função de extrair toda a energia proveniente do primeiro fornecendo-a à rede eléctrica com factor de potência unitário. Isto é conseguido com controlo em corrente através do qual se procura garantir que a corrente gerada pelo inversor está em fase com a tensão da rede.
O desenvolvimento do controlo foi realizado no programa Simulink. Os controladores foram dimensionados, implementados, testados e validados progressivamente, de modo a minimizar o número de parâmetros a ajustar ao mesmo tempo.
Foi desenvolvida uma interface gráfica, utilizando o programa ControlDesk, para permitir os ajustes necessários dos controladores e visualização de diversas variáveis do sistema. Esta fase do trabalho foi desenvolvida no Instituto Politécnico de Bragança, com vista à implementação prática.
Os trabalhos continuaram com a realização de um estágio, no âmbito do programa Erasmus, no CIEMAT – Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas e posteriormente no CEDEX - Centro de Estudios y Experimentación de Obras Públicas, em Madrid.
No CIEMAT foi apresentado o estado de desenvolvimento dos realizados no IPB, tendo em vista a implementação laboratorial. Os primeiros resultados experimentais foram obtidos no CEDEX com o controlo do conversor elevador. The goal of this dissertation was the analysis, implementation and control of an AC-DC-AC power converter built with a DC/DC step-up converter and a single phase inverter for grid-tied wind turbines based on permanent magnet synchronous generator.
The overall control of the converter AC-DC-AC followed a strategy in which the control of the step-up converter and the single phase inverter was implemented independently. The first is used to maximize the power available in the wind turbine through the implementation of an algorithm for the maximum power point tracking (MPPT), while the second is used to capture all the energy provided by the first and send it to the grid with unit power factor. This is achieved with current control of the inverter in order to ensure that the current generated by the inverter is in phase with the mains voltage.
The development of the monitoring program was carried out with the software Simulink. The PI controllers were designed, implemented, tested and validated step-by-step to minimize the number of parameters to adjust the same time.
A graphical interface was developed using the software ControlDesk to allow suitable adjustments of the control, and display several variables of the system. This stage of work was developed at the Instituto Politécnico de Bragança, in view of the practical implementation.
The work continued during an internship within the framework of Erasmus in CIEMAT - Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas and later in CEDEX - Centro de Estudios y Experimentación de Obras Públicas, in Madrid.
In CIEMAT, the state of development of the work developed in IPB was presented, and continued in view of the implementation in laboratory. The first experimental results were obtained in CEDEX with the control of the step-up converter.
22
Anderson, Glenn Warwick Jan. "Hybrid simulation of AC-DC power systems". Thesis, University of Canterbury. Electrical and Computer Engineering, 1995. http://hdl.handle.net/10092/1176.
Testo completoAbstract (sommario):
Transient stability studies are primarily concerned with the generator response of ac power systems and use only steady state type equations to model HVdc converter terminals. These equations are adequate for small disturbances at the converter terminals but cannot accurately represent a converters behaviour during, and through its recovery of, a significant transient disturbance. A detailed three phase electromagnetic analysis is necessary to describe the converters correct behaviour. This thesis describes an accurate and effective hybrid method combining these two types of studies, for analyzing dynamically fast devices such as HVdc converters within ac power systems. Firstly, conventional techniques are reviewed for both a transient stability analysis of power systems and for an electromagnetic transient analysis of HVdc converters. This review deals in particular with the two programs that constitute the hybrid developed in this thesis. Various techniques are then examined to efficiently and accurately pass the dynamic effects of an HVdc link to an ac system stability study, and the dynamic effects of an ac system to a detailed HVdc link study. An optimal solution is derived to maximise the inherent advantages of a hybrid. Finally, the hybrid is applied to a test system and its effectiveness in performing its task is shown.
23
Wu, Yue-Lin, e 吳岳霖. "Bi-Directional AC/DC Converter". Thesis, 2005. http://ndltd.ncl.edu.tw/handle/454xtz.
Testo completoAbstract (sommario):
碩士國立臺北科技大學
電機工程系所
93
The thesis is dedicated to the design and implementation the bi-directional AC/DC converters for the front-end of inverter. The developed converter is modulated by space vector modulation and the related controlled quantities are referred to synchronous frame. The controller consists of multiple control loops, which include inner current loop and external voltage loop to achieve fast response. The inner loop is based upon direct current control and the voltage decouple to achieve current tracking, and the external loop controls the output voltage to follow the desired DC voltage value by balancing of instantaneous power between input and output. The developed converter improves the input power factor to approximate unity power factor and reduces the total harmonic distortion of current less than 5%. The low order harmonics are reduced and thereby decreasing the harmonic pollution. The specifications of the system include: the input voltage is AC 220 V/60 Hz, output power 1 kW, carrier frequency is 15 kHz, power factor is higher than 0.9, and the total harmonic distortion of current is less than 5%. The simulation software is developed based upon the platform of Matlab® -Simulink® and the experimental set-up is based on the dSPACE digital control board. The power devices of converter are controlled by the three-phase gating signals generated by space vector modulation technique. To reduce the number of sensor, a current estimation method is proposed to give the DC-link current. The feasibility of the proposed method is verified by simulation and experimental results.
24
Rout, Rashmi Ranjan, e Durga Prasad Tripathy. "AC to DC Converter Using Microcontroller". Thesis, 2009. http://ethesis.nitrkl.ac.in/301/1/AC2DC.pdf.
Testo completoAbstract (sommario):
The aim of the project is to obtain a controlled DC output from a standard single phase 230V, 50Hz power supply. For this we first rectified the ac voltage using four diodes. Then the rectified DC voltage is used to get controlled DC voltage output using an IGBT with a pulse of variable duty cycle, generated by a microcontroller. By varying the duty cycle of the square wave pulse the average output DC voltage is regulated. For user interfacing, a knob is used to set the required voltage. This is achieved by converting the analog signal input, from the knob, to digital signal by using the internal Analog to Digital converter present in the microcontroller. The microcontroller sets the duty cycle of the PWM wave according to the ADC value obtained. This PWM wave is given as input to the IGBT to regulate its duty cycle, and hence the average output voltage is regulated. This is basically the open loop regulation of voltage. If the load varies, then we have to use closed loop control to automatically increase the duty cycle of the gate pulse to the IGBT if the output voltage falls below a set point and vice versa. The negative feedback loop is based on PID loop control. Thus the output voltage is continuously tuned with the set point voltage.
25
Wang, Sheng-Yuan, e 王聖淵. "System integration of AC-DC and DC-DC Converter". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/9a3zhg.
Testo completoAbstract (sommario):
碩士崑山科技大學
電子工程研究所
107
As the trend of electric vehicles is becoming clearer, the charging system is also charged by AC to DC. The main purpose of this thesis is to develop and discuss the application of an AC-DC and DC-DC integration. Can be applied to charging systems or other related consumer electronics. DC-DC Converter developed a system with DC48V, switching frequency of 60kHz~65kHz and power of 60W in the form of Flyback. And with AC-DC system.
26
LIN, TSE-YU, e 林哲宇. "AC-DC Power Converter with DC Decoupling Circuit". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/71621339711881941783.
Testo completoAbstract (sommario):
碩士國立高雄海洋科技大學
微電子工程研究所
105
AC-DC power converters have been widely used in the applications of electronic equipment for supplying electric power and battery charger. In this thesis, a AC-DC power converter, composed of a totem-pole bridgeless boost power factor corrector and a DC decoupling circuit, is developed. By controlling the power electronics, the input current of totem-pole bridgeless boost power factor corrector will be sinusoidal and in phase with the utility voltage to perform the unity power factor. The DC decoupling circuit is composed of a power-electronic arm and a passive power filter. The operation of DC decoupling circuit is simulated to be a virtual AC impedance connected to the DC output in series to suppress the AC ripple of output current for the totem-pole bridgeless boost power factor. Accordingly, the capacity of filter capacitor for the totem-pole bridgeless boost power factor is reduced such that the use of electrolytic capacitor can be avoided to prolong the service life and improve the reliability. A hardware prototype based on the control chips of digital signal processor (DSP) will be developed to verify the performance of the proposed AC-DC power converter.
27
Jan, CHih-Chiang, e 詹智強. "Study of Directly-Converted-Type DC/AC and AC/AC converters for UPS". Thesis, 1996. http://ndltd.ncl.edu.tw/handle/66199330272462907879.
Testo completoAbstract (sommario):
碩士國立成功大學
電機工程研究所
84
In this thesis, a directly-converted-type dc/ac and ac/ac converter topology for UPS is proposed. Using the technique of the Buck-Boost circuit, a reliable sinusoidal ac output is presented at load end for the case of ac or dc input. Voltage- mode and current-mode control methods are investigated to deal with various loads and sources. Good output characteristics are achieved in the voltage-mode control for dc input. However, when ac input is applied, the output will distort. In order to solve this problem , the current- mode control is addressed. In the current mode control, by way of additional current feedback loop is used, the proposed system can obtain the better output profile. To verify the proposed scheme, the prototype is implemented. The experiment results are agreed with the theoretical analysis.
28
Ho, Wen-Jung, e 何文榕. "Optimizing Single-Phase AC/DC/AC Converter with PFC-Preregulator Improvement". Thesis, 1997. http://ndltd.ncl.edu.tw/handle/30363357595270470618.
Testo completoAbstract (sommario):
博士國立臺灣大學
電機工程學系
85
The research of the dissertation focuses on the topologies of single-phase AC/DC/AC converter with pre-staged power-factor- correction (PFC). In the beginning, new topologies for PFC- prestaged AC/DC/AC converter are presented. The introduction of common-neutral connection simplifies the conventional connection of AC/DC/AC structure, and gives new topologies that still have good performance, conform with output safety regulations and have other advantages such as requiring fewer power devices and having loweconduction losses. Then a new on-line uninterruptible power supply (UPS) structure is also presented. It consists of a dual-functional PFC substituting for an inevitable battery- voltage booster thereby simplifying the complexity of power stage. Finally an even simpler topology of power stage for UPS applications is to be shown. This new single-conversion UPS mainly consists of a minimized power converter structure which is capable of providing specified constant output voltage, phase-controlled battery charr, and input-power-factor improvement.
29
Su, Hsin-Ping, e 蘇心平. "A Multi-carrier PWM for AC-DC-AC Converter Without DC Link Electrolytic Capacitor". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/70517992308602431561.
Testo completoAbstract (sommario):
碩士中華大學
電機工程學系碩士班
102
Abstract This study proposes a multi-carrier pulse width modulation (PWM) for AC-DC-AC converter without DC link electrolytic capacitor. The AC-DC-AC converter consists of an AC-DC active front-end converter, a DC-AC voltage source inverter, and a 20uF ceramic capacitor in DC link. The DC bus voltage controller with load compensator is utilized to maintain the voltage of the DC link capacitor at designed value. Furthermore, the multi-carrier PWM is utilized to reduce the common-mode voltage (CMV) of AC-DC active front-end converter and DC-AC inverter. The simulation and test result are presented to validate the performances of the proposed scheme. Keywords— AC-DC-AC converter; active front-end converter; inverter; multi-carrier PWM .
30
LinDean-Feng e 林鼎峰. "A novel DC/AC power converter system". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/55400784237530649325.
Testo completoAbstract (sommario):
碩士崑山科技大學
電機工程研究所
95
The cost of fossil energy was rsien up, recently. This has promoted the importance of the renewable energy. A small capacity DC/AC power conversion interface for renewable energy will be developed in this thesis. This power conversion interface including a DC/DC power converter and a DC/AC power converter. The PWM modualtion strategy is used in the DC/DC power converter to generate a rectifier sinusoidal current. The DC/AC inverter, opaerated in the low switching frequency, converts the the rectifier sinusoidal current to a sinuoidal current and feeds to the utility. Because the DC/AC inverter is opaerated in the low switching frequency, it can reduce the switching loss. Hence, the power efficiency of the entire system can be increased. Moreover, the DC capacitor between the DC/DC power converter and the DC/AC inverter can be omited.This can increase the reliability of the DC/AC power conversion interface. A prototype is developed and tested to demonstrate the performance of the proposed DC/AC power conversion interface. The experimental results show that the proposed DC/AC power conversion interface has the expected performance.
31
Hong-WeiDeng e 鄧弘緯. "DSP Controlled AC-DC Bidirectional Power Converter". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/55249315633117041500.
Testo completo
32
Wang, Sing-han, e 王星翰. "Robust Repetitive Control of DC/AC Converter". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/27477995344361845446.
Testo completoAbstract (sommario):
碩士國立中山大學
電機工程學系研究所
101
This thesis applies digital repetitive control to a single-phase DC-to-AC converter, with some proposed designs to improve stability and enhance performance of the converter under various load variations. A practical DC-to-AC converter is required to convert DC power to stable AC power with low harmonic distortion when attached to various linear or nonlinear loads. This thesis combines repetitive control with feedback dithering modulation and optimal state feedback to control the converter. The repetitive control is responsible for regulating output power and eliminating harmonics, while the feedback dithering modulation for switching the power transistors with reduced switching noise and the state feedback for stabilizing the converter under various load variations. The presented control and modulation schemes of the power converter are implemented on an FPGA (Field Programmable Gate Array). The experiments confirm the excellent performance and robustness of the converter, indicating a total harmonic distortion of less than 0.5% for the converter when attached to various linear or nonlinear loads.
33
WU, XI-ZHEN, e 吳喜楨. "Interleaved DC-AC Converter With Decoupling Circuit". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/rhk4xt.
Testo completoAbstract (sommario):
碩士國立高雄科技大學
微電子工程系
107
DC-AC power converters have been widely used in solar power generation systems. This paper presents an interleaved DC-AC converter with a DC decoupling circuit. It consists of an interleaved DC-AC power converter and a decoupling circuit. The interleaved DC-AC power converter is controlled to convert the DC power to AC power and generate a sinusoidal current in phase with the utility voltage. The decoupling circuit is composed of two power electronic switches and passive filters. The decoupling circuit is used to decouple the DC component and double-frequency component, so as to suppress the double-frequency ripple of DC bus for the interleaved DC-AC power converter. Accordingly, the electrolytic capacitor can be replaced by a film capacitor to improve the reliability of solar power generation system. A DSP controlled prototype is developed and test to verify the performance of interleaved DC-AC converter with DC decoupling circuit.
34
Chen, Hsin-hsuan, e 陳信炫. "Development of AC-DC-AC Power Converter for Small Wind Power Systems". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/14261835836303093220.
Testo completoAbstract (sommario):
碩士國立臺灣科技大學
電機工程系
98
This thesis presents the analysis and design of power converters for small wind generators. The system consists of three-phase permanent-magnet synchronous generator, rectifier and inverter, which can transfer the generator power from varying-frequency and varying-voltage to single-phase for grid connection. The ac-dc power converter uses three-phase independent connections of totem-pole converter to keep dc-link voltage constant and exercise maximum power-point tracking. The single-phase inverter can provide the generator power to grid. The proposed system uses Matlab-Simulink/Simpower to simulate rectifier and inverter. The simulated results obtained serve as the basis for system implementation and performance evaluation. The high-performance and low-cost digital signal processor TMS320F2808 is used to control the power converter. An experimental system is built. The power converter supplies 780W with the current total harmonic distortion of generator of about 14.11%, while the current total harmonic distortion of single-phase output under grid connection is about 10.97%. The corresponding overall efficiency of 86.6 % is obtained using three-phase independent connections of totem-pole power converter.
35
Li, Cheng-Chang, e 李承璋. "Study and Realization of a DSP-Based High-Performance AC/DC/AC Converter". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/19980591023974352170.
Testo completoAbstract (sommario):
碩士國立宜蘭大學
電機工程學系碩士班
97
A digital signal processor (DSP) -based high performance AC/DC/AC converter is studied and realized in this thesis, whose main contribution is the replacement of the former analog controller by digital system, which is trying to implement the simplicity, less interference noise and great reduction of system scale of the control circuit. Besides, the proposed digital controller can achieve the technique of average-current mode control and sinusoidal pulse width modulation (SPWM), which can retain the merit of high power factor and low input current harmonic, on the rectifier side, and the merit of stable AC output voltage and good dynamic regulation, on the inverter side, respectively. In this thesis, the function of soft-switching is derived through zero voltage switching (ZVS) strategy, namely, switching losses of main switch is lowered and higher efficiency is achieved. Finally, computer simulation and experimental results are presented in this thesis for verification.
36
Liao, Di, e 廖荻. "Study and Implement of a Bi-Directional Bridgeless AC-Switch AC/DC Converter". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/f2n2zt.
Testo completoAbstract (sommario):
碩士國立臺灣科技大學
電子工程系
106
This thesis aims to study and design an output power 750 W, AC-side 230 V, DC-side 750 V bi-directional high efficiency and high power density for power converter of green energy system. For wider range of applications, this thesis implements synchronous rectification to achieve bi-directional power transference and the bridgeless topology for higher rectification-model efficiency, the inverter-model applied is a T-type inverter topology. On other the hand, the digital control used to replace analog control, the analog control is economical and simple but compared with digital control, it are some disadvantages such as not able to be using advance control technology and so on. Therefore, this thesis realize average current mode control for rectification-model and unipolar PWM control for invert-model base on digital signal processor. Finally, a high power density bi-directional converter has been achieved, the rectification-model efficiency about 98.11% and inverter-model efficiency around 96.2% in full-load.
37
Yeh, Y. T., e 葉有倉. "Study of Direct-Conversion-Type DC/AC Converter". Thesis, 1998. http://ndltd.ncl.edu.tw/handle/27729734261528696054.
Testo completo
38
黃士航. "Study of the improved AC/DC power converter". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/63103249095295520196.
Testo completo
39
-Yi, Jhang Jian Jyun, e 張簡駿逸. "AC-DC Power Converter with Unity Power Factor". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/42464490460403641181.
Testo completoAbstract (sommario):
碩士國立高雄海洋科技大學
微電子工程研究所
101
In this paper, an AC-DC power converter with unity power factor is proposed. The proposed AC-DC power converter is configured by two cascade–connected power factor correctors, a buck power converter and a forward power converter. One of power factor correctors is switched in high-frequency pulse-width modulation, and the other one is switched in the frequency the that of input AC voltage. Accordingly, the cascade operation of two power factor correctors can generate a five-level AC voltage in the input terminal so as to reduce the capacity of input filter. As compared with the conventional power factor corrector, the output voltage of power factor corrector in the proposed AC-DC converter is reduced by half. Thus, the switching voltage of high-frequency power factor corrector is also reduced by half. Hence, the switching power loss of high-frequency power factor corrector is reduced and the electromagnetic interference of AC-DC power converter is alleviated. In addition, the input current of AC-DC power converter will be controlled by the high-frequency power factor corrector to be a sinusoidal waveform in phase with the input AC voltage so as to attain unity power factor. The buck power converter and the forward power converter are applied to integrate the output voltages of power factor correctors to an output voltage supplying to the load. A prototype with a digital signal processor based controller is developed and tested to verify the performance of the proposed AC-DC power converter.
40
HSU, JUI-PO, e 徐瑞柏. "Three-phase Impedance-Source Bidirectional AC/DC Converter". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/n5b7ft.
Testo completoAbstract (sommario):
碩士國立臺灣科技大學
電子工程系
105
In this thesis, the topology of three-phase AC-DC converters is studied. An impedance source (Z-source) topology together with traditional three-phase six-switch circuit to achieve the buck/boost function in single-stage structure. Traditional voltage source or current source inverter has the limitation that output voltage can only be less than or greater than the input voltage. The impedance source topology has combination of inductors, capacitors, and one auxiliary switch. The input port is neither a voltage source nor a current source. Therefore, the output voltage can be either higher or lower than the input. Besides, eliminating the potential hazard of short-through or open-circuit in voltage-source or current-source circuits, Z-source circuit possesses better reliability. In one of the two operation modes, the auxiliary switch can be passively mode, resulting an easier control mechanism. The control algorithm for a Z-source can be an extension based on convention control algorithm. This thesis implements a three-phase Z-source AC-DC converter with input voltage of 150 V and 200 V, output voltage of 110 Vrms and 500 W output power. According to the test results, it is confirmed that the effect can be buck/boost in single-stage structure.
41
Mallik, Dhara I. "Design of isolated DC-DC and DC-DC-AC converters with reduced number of power switches". Thesis, 2017. https://doi.org/10.7912/C2H652.
Testo completoAbstract (sommario):
Indiana University-Purdue University Indianapolis (IUPUI)There are various types of power electronic converters available in recent days. In some applications (e.g. PC power supply), it is required to supply more than one load from a single power supply. One of the main challenges while designing a power converter is to increase its e ciency especially when the number of power switches employed is relatively large. While several loads are supplied from a single source, if the power loss in the switches cannot be reduced, then the expected utilization of using a single source is not very feasible. To reduce the loss and increase e ciency, the thesis presents a novel design with reduced number of switches. The scope of this thesis is not limited to the dc-dc converter only, the converter to supply three phase ac loads from a single dc source is also presented. This discussion includes an improved fault tolerant configuration of the inverter part. The generated waveforms from the simulations are included as a demonstration of satisfactory results.
42
Liaw, Yisheu, e 廖怡咰. "Analysis and Design of Digital Signal Processor Applied to the AC/DC/AC Converter". Thesis, 2000. http://ndltd.ncl.edu.tw/handle/45711160642468305694.
Testo completoAbstract (sommario):
碩士國立雲林科技大學
電機工程技術研究所
88
A current control technique based on the space vector modulation for a three-phase rectifier is adopted to the AC/DC/AC system. This control technique calculated the voltage in front of the switches of rectifier. Then by the space vector modulation, the rectifier can correct the power factor. The vector control method is used to construct the driving system of the induction motor. The optimal conduction time of the AC/DC/AC converter is achieved by the optimal voltage vector and time selector. Because the two converters are active in the same time, the power can be directly delivered to the three-phase induction motor. Thus instead of the bulky electrolytic capacitor in the dc link, small capacitors can be used. A quasi-parallel resonant DC link circuit can be applied to the induction motor system to implement the soft-switching inverter. In all signal processings, TI TMS320C240 digital signal processor is regarded as the heart of the system to complete the related software. From the results of experiments, it is proved that it can achieve the power factor correction and the stable AC/DC/AC operation even with the smaller capacitor.
43
Luo, You Gang, e 羅有綱. "High-performance AC/DC converters". Thesis, 1995. http://ndltd.ncl.edu.tw/handle/85254283529982708794.
Testo completo
44
Chen, Hsin-Hon, e 陳信宏. "Digital power factor correction circuit of AC/DC converter". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/67968339218317731054.
Testo completoAbstract (sommario):
碩士國立清華大學
電子工程研究所
92
This thesis introduces some type of the power converters and themechanism of power factor correction (PFC) circuits; and present the study and implementation of digital power factor correction circuit that uses TSMCCMOS 0.35 um technology to realize PFC circuit. With the growing of VLSI technology, the development of industry and electronic products all need more reliable, cheap and intelligent power control system. How to control several watts even tens of kilowatts power transformation without consuming too much energy during transforming is the topic for scholars to study and implementation. In the other word, how to use energy efficiently will be an aim to power electronics. PFC circuits play an important role to improve the efficiency and to minimize the power pollution .When people pay attention to environmental protection, some people also care about the pollution about power system. Many countries in Europe and North America make some standards to constrain some power products, IEEE 519 and IEC 1000-3-6 for example. PFC circuit can achieve high power correction factor and minimize the total harmonic distortion, so nowadays many powerproducts include the PFC function in them. Many IC design concepts base on digital and analog circuits , these two types both have advantages and disadvantages. The PFC circuits are also divided into two types---digital and analog. This thesis will compare these two types, and combine some advantages of digital and analog circuits to realize the PFC circuit. Because the majority of the PFC circuit is digital, it still called ‘digital PFC circuit’. Finally, this work uses TSMC CMOS 0.35 um technology to simulate PFC circuit, then the power factor achieves 0.999 and total harmonic distortion achieves 2.09% when full loading.
45
Cheng, Jen-Chun, e 鄭任鈞. "Implementation of the AC-DC Converter for LED Driver". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/5k47vp.
Testo completoAbstract (sommario):
碩士遠東科技大學
電機工程研究所
101
In this thesis, a AC-DC converter is proposed applied to the LED. The converter increase the inductance of the transformer secondary side as energy storage. Energy does not need the third winding transformer remanence, recovery to output. The pulse width modulation control strategy is used to control the active switches. This circuit Power factor correction is operated in discontinous coduction mode. Can be achieved near unity power factor and low input current total harmonic distortion. The operating principle and steady-state analysis are discussed in detail. Finally, AC input 90 ~ 264 V , DC output 39 ~ 46 V and output power 65 W is implemented to verify the performance of the proposed converter.
46
Han, Chia-Chung, e 韓家仲. "Seven-Level AC-DC Power Converter Based Battery Charger". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/34384411792801448041.
Testo completoAbstract (sommario):
碩士國立高雄海洋科技大學
微電子工程研究所
102
AC-DC power conversion has been widely used in the applications of electronic equipment for supplying electric power and battery charger. In this thesis, a seven-level AC-DC power converter based battery charger, composed of a seven-level AC-DC power converter and a dual-input buck power converter, is developed. The seven-level AC-DC power converter is configured by a diode rectifier and a dual-boost power converter. The output voltages of dual-boost power converter are controlled to be multiple relationships. By controlling the power electronics, the dual-boost power converter will generate a four-level DC voltage at the output dc terminals of diode rectifier. Accordingly, the voltage at the input AC terminals of diode rectifier is an AC voltage with seven levels. Since the level of the input AC voltage is increased, the switching power loss is reduced. In addition, the input filter and the electromagnetic interference (EMI) filter are reduced. The input current of seven-level AC-DC power converter is controlled to be sinusoidal and in phase with the utility voltage, it performs the harmonic suppression and unity power factor. Only two power electronic switches are used in the seven-level AC-DC power converter, both the power circuit and the control circuit are simplified. The dual-input buck power converter is used to regulate the output voltages of dual-boost power converter with multiple relationships and generate an output power to charge the battery set. A hardware prototype based on the control chips of digital signal processor (DSP) and complex programmable logic device (CPLD) will be developed to verify the performance of the proposed seven-level AC-DC power converter based battery charger.
47
Yang, Po-En, e 楊柏恩. "A High-performance AC/DC Converter for LED Lighting". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/11575557210736684859.
Testo completoAbstract (sommario):
碩士義守大學
電機工程學系碩士在職專班
102
This thesis proposes a novel LED driver consisting of a boost converter and a buck converter. Each converter adopts a power MOSFET as the active switch. Without useing any lossless snubber circuit and/or auxiliary switch, both active switches can operate at zero-voltage switching (ZVS) on by freewheeling the inductor currents of the converters to flow through the intrinsic diodes of the MOSFETs. The boost converter is operated at discontinuous-conduction mode (DCM) to perform the function of power-factor correction (PFC) to ensure almost unity power factor at the input line. The detailed circuit operations and analysis are provided. A prototype 60-W LED driver was built and tested. Experimental results show that the switching losses can be effectively reduced by operating the active switches at ZVS. The measured power factor and circuit efficiency are as high as 0.99 and 95.6%, respectively.
48
Agrawal, Ashish, Srikant Kayal e Bhaskar Munshi. "Study of Wind Turbine Driven Doubly Fed Induction Generator (DFIG) Using AC/DC/AC Converter". Thesis, 2009. http://ethesis.nitrkl.ac.in/311/1/studyofDFIG_pdf.pdf.
Testo completoAbstract (sommario):
In recent years, wind energy has become one of the most important and promising sources of renewable energy, which demands additional transmission capacity and better means of maintaining system reliability. The evolution of technology related to wind systems industry leaded to the development of a generation of variable speed wind turbines that present many advantages compared to the fixed speed wind turbines. These wind energy conversion systems are connected to the grid through Voltage Source Converters (VSC) to make variable speed operation possible. The studied system here is a variable speed wind generation system based on Doubly Fed Induction Generator (DFIG). The stator of the generator is directly connected to the grid while the rotor is connected through a back-to-back converter which is dimensioned to stand only a fraction of the generator rated power.
To harness the wind power efficiently the most reliable system in the present era is grid connected doubly fed induction generator. The DFIG brings the advantage of utilizing the turns ratio of the machine, so the converter does not need to be rated for the machine’s full rated power. The rotor side converter (RSC) usually provides active and reactive power control of the machine while the grid-side converter (GSC) keeps the voltage of the DC-link constant. The additional freedom of reactive power generation by the GSC is usually not used due to the fact that it is more preferable to do so using the RSC. However, within the available current capacity the GSC can be controlled to participate in reactive power generation in steady state as well as during low voltage periods. The GSC can supply the required reactive current very quickly while the RSC passes the current through the machine resulting in a delay. Both converters can be temporarily overloaded, so the DFIG is able to provide a considerable contribution to grid voltage support during short circuit periods. This report deals with the introduction of DFIG, AC/DC/AC converter control and finally the SIMULINK/MATLAB simulation for isolated Induction generator as well as for grid connected Doubly Fed Induction Generator and corresponding results and waveforms are displayed.
49
Pullaguram, Deepak Reddy. "Distributed control strategies for AC and DC microgrids". Thesis, 2018. http://eprint.iitd.ac.in:80//handle/2074/7925.
Testo completo
50
Mahakhuda, R. K. "Application of sliding mode controller in DC/AC and DC-DC power converter system". Thesis, 2014. http://ethesis.nitrkl.ac.in/5606/1/E-58.pdf.
Testo completoAbstract (sommario):
Maintaining good voltage regulation at output and having fast dynamic response under sudden load fluctuation are extremely important in distributed generation (DG) as well as uninterrupted power supply (UPS) systems. This work presents a fixed frequency hysteresis current (FFHC) controller, which is implemented on the basis of sliding mode control (SMC) technique and fixed frequency current controller with a hysteresis band. The controller have the benefit of hysteretic current control having fast dynamic responses and reduces the disadvantages of the variable switching frequency. For this work elliptical sliding surface was taken.These have been verified and compared with the carrier based pulse width modulated (PWM) voltage controller under the same load fluctuation. The proposed method is then applied to islanded single phase - voltage source inverter (VSI) system. The results show that the dynamic response is quite faster than that of widely used PWM-controlled inverter systems. The DC voltage that is required for the inverter input is supposed to given from the output of PV panel with buck converter.In PV system sliding mode control is used to track the maximum power point .Here inverter and buck converter connected to PV array are taken separately.