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Rahmat, Mohd Khairil. "Methods for reliability analysis of uninterruptible power supply (UPS) system." Thesis, University of Strathclyde, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444418.
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Schmidt, Uwe. "Uninterruptible power supply system using a dual converter in quasi-resonant mode." Thesis, Brunel University, 1995. http://bura.brunel.ac.uk/handle/2438/5410.
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Uninterruptible Power Supply (UPS) systems have become a standard to protect electronic devices such as servers and host computers. Also, the energy supply of whole buildings is linked with large UPS systems to ensure a steady power flow. Two system configurations are widely used which differ in price and their ability to protect very sensitive load. This thesis illustrates an analytical examination of all existing systems and concludes with the finding of new configurations with increased efficiency and reduced costs. A dual converter is proposed as the heart of the new UPS system. This converter links the necessary two sources of the UPS through a common transformer. The transformer operates at a high frequency which is enabled due to the resonant switching technique used. The results of this paper were achieved using mathematical analysis, electrical and electro-magnetic simulation as well as by experiments carried out on the self designed circuit boards in the laboratory. These boards were built in a modular way to enable series testing and thereby optimise the dimensioning of the system.
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Höglund, Jonatan. "Redundans vid manöver med hjälp av UPSpå elnätet." Thesis, Linnéuniversitetet, Sjöfartshögskolan (SJÖ), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-50407.
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Uys, Jacobus Johannes. "Dynamic digital control schemes for three-phase UPS inverters." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52810.
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Thesis (MScEng)--University of Stellenbosch, 2002.ENGLISH ABSTRACT: This thesis presents the design and implementation of a voltage controller for an Uninterruptible Power Supply (UPS) Inverter. The inverter is capable of producing a nearly sinusoidal output voltage waveform, thereby keeping the Total Harmonic Distortion (THD) to a minimum. Digital controllers introduce a time delay in the control law that causes system instability. Various control techniques, which includes Pade approximations and system augmentation, are investigated to eliminate the effect of the time delay. These controllers employ classical control as well as modem control techniques. The selection of the various control parameters is verified by mathematical equations. A load-disturbance compensation scheme, implementing feed-forward and gain scheduling, is also developed to improve voltage distortion when varying loads, such as non-linear loads, are connected to the system. It is shown that the constructed pulse-width modulated (PWM) control scheme can achieve fast dynamic response as well as a low THD.
AFRIKAANSE OPSOMMING: Hierdie verhandeling ondersoek die ontwerp en implementering van 'n spanningsbeheerder vir 'n ononderbroke kragtoevoer omsetter. Die stelsel produseer 'n uittree spannigsgolfvorm met 'n lae Totale Harmoniese Distorisie (THD). Digital beheerders veroorsaak 'n tydvertraging in die beheerwet wat stelsel onstabiliteit kan veroorsaak. Verskeie beheertegnieke wat gebaseer is op die Pade benaderings van die tydvertraging en stelsel aanpassings, is ondersoek. Hierdie beheerders maak gebruik van klassieke en moderne beheertegnieke. Die seleksie van die verskeie beheerderveranderlikes word gestaaf deur wiskundige vergelykings. Spannigsvervorming word tot 'n minimum beperk deur gebruik te maak van 'n lasveranderings-kompensasietegniek wat onderskeidelik vorentoe-voer en aanwins skedulering implementeer. Verder word daar bewys dat die pulswydte modulasie (PWM) beheerskema vinnige dinamiese gedrag asook 'n lae THD bewerkstellig.
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SANTOS, Gustavo Maciel dos. "Estudo do acoplamento de grupos Motor-Gerador com Uninterruptible Power Supply aplicando Wavelets e Redes Neurais Artificiais." Universidade Federal de Pernambuco, 2011. https://repositorio.ufpe.br/handle/123456789/5320.
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Previous issue date: 2011Com a sociedade globalizada e a evolução da informática, o conceito de horário comercial não é mais simples. Transações bancárias, negociações na bolsa de valores e compras pelo computador ocorrem em qualquer horário e as empresas precisam garantir a disponibilidade de seus serviços sempre. Para garantir o fornecimento ininterrupto de energia para estes sistemas de informações são utilizados grupos motorgerador (GMG) e uninterruptible power supply (UPS). Quando há dificuldade de acoplamento entre os dois equipamentos, na prática, os projetistas superdimensionam o GMG em relação ao UPS sem embasamento teórico para esta ação. Este estudo propõe apresentar a correlação entre os dados de placa desses equipamentos e o distúrbio de tensão entre eles para proporcionar uma maior segurança no dimensionamento de sistemas com UPS e GMG. A metodologia desse estudo propõe o uso de Redes Neurais Artificiais (RNA s) para descrever esta correlação e transformada wavelet para destacar os distúrbios medidos e auxiliar na convergência da RNA em seu treinamento. Os resultados obtidos com as redes desenvolvidas neste trabalho sugerem que o menor distúrbio no sinal, obtido devido ao acoplamento de UPS e GMG, ocorrerá se as potências dos equipamentos (dados de placa) forem próximas, independente do nível de carregamento do sistema. À medida que esta relação se distancia do valor unitário, a perturbação aumenta e um UPS com potência menor que o GMG contribui mais com a distorção do sinal do que ao contrário
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Cetinkaya, Suleyman. "Repetitive Control Of A Three-phase Uninterruptible Power Supply With Isolation Transformer." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608150/index.pdf.
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A repetitive control method for output voltage control of a three phase uninterruptible power supply (UPS) with isolation transformer is investigated. In the method voltage control loop is employed in the stationary dq frame. The controller eliminates the periodic errors on the output voltages due to inverter voltage nonlinearity and load disturbances. The controller design and implementation details are given. The controller is implemented on a 5-kVA UPS prototype which is
constructed in laboratory. Linear and nonlinear loads for balanced and unbalanced load operating conditions are considered. The steady-state and dynamic performance of the control method are investigated in detail. The theory of the control strategy is verified by means of simulations and experiments.
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Kamran, Farrukh. "A new UPS topology and deadbeat control techniques for improved utility interface compatibility." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/15773.
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Milad, Muftah A. "UPS system : how current and future technologies can improve energy efficiency in data centres." Thesis, Brunel University, 2017. http://bura.brunel.ac.uk/handle/2438/14664.
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A data centre can consist of a large group of networked servers and associated power distribution, networking, and cooling equipment, all that application consumes enormous amounts of energy as a small city, which are driving to a significant increase in energy inefficiency problems in data centre, and high operational costs. Also the massive amounts of computation power contained in these systems results in many interesting distributed systems and resource management problems. In recent years, research and technologies in electrical engineering and computer science have made fast progress in various fields. One of the most important fields is the energy consumption in data centre. In recent years the energy consumption of electronic devices in data centre, as reported by. Choa, Limb and Kimb, nearly 30000000 kWh of power in a year, may consume by a large data centre and cost its operator around £3,000,000 for electricity alone. Some of the UK sites consume more than this. In the UK data centre the total power required are amid 2-3TWh per year. Energy is the largest single component of operating costs for data centres, varying from 25-60%. Agreeing to many types of research, one of the largest losses and causes of data centre energy inefficiency power distribution is from the uninterruptible power supply (UPS). So a detailed study characterized the efficiencies of various types of UPSs under a variety of operating conditions, proposed an efficiency label for UPSs, also investigate challenges related to data centre efficiency, and how all new technologies can be used to simplify deployment, improve resource efficiency, and saving cost. Data centre energy consumption is an important and increasing concern for data centre managers and operators. Inefficient UPS systems can contribute to this concern with 15 percent or more of utility input going to electrical waste within the UPS itself. For that reason, maximizing energy efficiencies, and reduce the power consumption in a data centre has become an important issue in saving costs and reducing carbon footprint, and it is necessary to reduce the operational costs. This study attempts to answer the question of how can future UPS topology and technology improve the efficiency and reduce the cost of data centre. In order to study the impact of different UPS technologies and their operating efficiencies. A model for a medium size data centre is developed, and load schedules and worked diagrams were created to examine in detail and test the components of each of the UPS system topologies. The electrical infrastructure topology to be adopted is configured to ‘2N’ and ‘N+1’ redundancy configuration for each UPS systems technologies, where ‘N’ stands for the number of UPS modules that are required to supply power to data centre. This work done at RED engineering designs company. They are professionals for designing and construction of a new Tier III and Tier IV data centres. The aim of this work is to provide data centre managers with a clearer understanding of key factors and considerations involved in selecting the right UPS to meet present and future requirements.
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Oliveira, Lincoln Moura de. "A New Conception of Multilevel Inverter for UPS Application." Universidade Federal do CearÃ, 2009. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=11289.
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FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgicoThis work deals with the theoretical analysis, design methodology and laboratory implementation of a 3kVA on-line mode Uninterruptible Power Supply (UPS) composed by a multilevel inverter based on a transformer with multiple secondaries and an active power factor correction input stage composed by a diode rectifier in series with a boost converter.The main motivation for this study is to assess the benefits of multilevel inverters in low power (<10kVA) applications. A 3kVA Uninterruptible Power Supply (UPS) with output and input voltage of 220V and 60Hz, has been implemented. Simulation and experimental results for a single phase prototype are conducted to validate the proposed idea. The utilization of low frequency operation inverters promotes low EMI, lower switches stresses, very low commutation losses and consequently higher efficiency. The multilevel converter here used isolates the load from the grid due to the multi-windings transformer intrinsic to the topology. The on-line mode of the UPS (no battery mode) has been implemented. Simulation and experimental results for a single-phase prototype are presented to validate the proposed converter. The UPS presented an efficiency of 90%
Este trabalho apresenta a anÃlise teÃrica, metodologia de projeto e implementaÃÃo do modo rede de um sistema ininterrupto de energia (UPS) na configuraÃÃo on-line, utilizando um inversor multinÃvel e um prÃ-regulador com correÃÃo de fator de potÃncia. O inversor baseia-se num transformador que opera em baixa freqÃÃncia com mÃltiplos secundÃrios isolados, em que a tensÃo multinÃvel na saÃda à formada atravÃs da combinaÃÃo dos enrolamentos secundÃrios do transformador por chaves de potÃncia estÃticas operando em baixa freqÃÃncia. O prÃ-regulador à composto por uma ponte completa de diodos em sÃrie com um conversor boost. A motivaÃÃo para este estudo consiste em avaliar os benefÃcios da utilizaÃÃo de inversores multinÃveis em baixas potÃncias (<10kVA) em UPS, com Ãnfase nos rendimentos das topologias. A utilizaÃÃo do inversor multinÃvel operando em baixa freqÃÃncia garante menores Ãndices de EMI, menores esforÃos de tensÃo e corrente nos semicondutores da estrutura, desprezÃveis perdas por comutaÃÃo e consequentemente maior rendimento. A estrutura utilizada possui ainda a caracterÃstica de garantir isolamento galvÃnico da rede elÃtrica com a carga atravÃs da utilizaÃÃo do transformador intrÃnseco desta topologia. O prÃregulador possui uma topologia que garante facilidade de implementaÃÃo e alto rendimento. O modo rede de um sistema ininterrupto de energia de 3kVA com tensÃo de entrada e saÃda de 220V e 60Hz, foi implementado. As simulaÃÃes e os resultados experimentais para um protÃtipo monofÃsico sÃo apresentados para a validaÃÃo da estrutura. O rendimento mÃximo obtido para o protÃtipo foi de 90%.
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Jacobsson, Erik. "Dimensionering av UPS-system och generatorer för reservkraftsystem på sjukhus och flygplatser." Thesis, Karlstads universitet, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-69399.
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Sjukhus och flygplatser är precis som resten av samhället, beroende av el. Med dagens teknik är sjukhus och flygplatser högteknologiska ochväldigt störningskänsliga för elbortfall,vilket gör det viktigt att ha en stabil och säker kraftförsörjning utan avbrott. Ett avbrott i strömförsörjningen kan orsaka allvarliga,till och med livsfarliga konsekvenser. Att säkerställa ett bra och redundant reservkraftsystemär väsentligt för sjukhusen och flygplatserna. Syftet med studien var att undersöka samt ta fram reservkraftsystem med redundansförsjukhus och flygplatser. Under arbetets gång har litteraturstudie om generatorer och UPS-system (uninterruptible power supply) gjorts samt intervjuer med experter inom båda ämnena. Resultat visar de fundamentala delarna som är viktiga att ta hänsyn till vid dimensionering av reservkraftsystem. Men det visar också på att det finns många faktorersom spelar in vid dimensionering av systemen, vilket leder till att alla system ser olika ut och det finns inte riktigtnågon specifik mall att följa.Hospitals and airports are just like the rest of society, dependent onelectricity. With today's technology, hospitals and airports are highly technological and highly sensitiveto electricity loss. Thatmakes it important to have stable and secure power supply without interruptions. An interruption of power supply can cause serious even fatal consequences. Ensuring a good and redundant reserve power system is essential for hospitals and airports. The purpose of the study was to investigate and provide good redundant solutions for reserve systems in hospitals and airports. During the course of the thesis, literature studies ofgenerators and UPS (uninterruptible power supply) systems have been conducted as well as interviews with experts in both subjects.Results show the fundamental aspects that should be taken into account when dimensioning reserve power systems. But it also shows that there are many aspects that affectthe system dimensioning, which means that all systems look different and there is no specific template to follow.
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Vieira, Carlos Eduardo. "UPS híbrida: integração de uma fonte alimentação ininterrupta com um sistema de geração fotovoltaico." Master's thesis, Instituto Politécnico de Setúbal. Escola Superior de Tecnologia de Setúbal, 2016. http://hdl.handle.net/10400.26/16849.
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Dissertação submetida como requisito parcial para
obtenção do grau de Mestre em Engenharia
Eletrotécnica e de Computadores – perfil de
Energias Renováveis e Sistemas de PotênciaEste trabalho apresenta estruturas híbridas para um sistema de alimentação ininterrupta (UPS) com a integração de um sistema fotovoltaico (PV). Atualmente, a forma mais segura de fornecer energia para os equipamentos críticos ou sistemas de processamento de dados é efetuada a partir da utilização de uma UPS do tipo on-line. Por outro lado, normalmente não é requerida mesma segurança de uso num sistema fotovoltaico. Nesta dissertação serão apresentadas topologias para a integração de ambas tecnologias, de modo a gerar e fornecer energia de qualidade para as cargas críticas. Tendo em consideração a integração do sistema PV na UPS, logo esta também poderá funcionar desvinculada da rede, desde que a energia produzida pelo PV seja suficiente. A primeira das soluções é baseada numa estrutura de dupla conversão clássica. No entanto, será apresentada uma solução alternativa baseada numa topologia de conversão do tipo multinível. Esta última estrutura, propõe a utilização de duas UPS interligadas por único transformador trifásico de enrolamentos abertos, na entrada e na saída do sistema. Os barramentos DC são independentes e conectados aos respectivos conversores de controlo do sistema PV e das baterias. Esta nova estrutura apresenta diversas vantagens, tais como, maior fiabilidade no fornecimento de energia para cargas críticas e na qualidade da forma de onda de saída. Para além das estruturas propostas, serão apresentados os correspondentes circuitos de controlo. Ambos os sistemas foram simulados em Matlab/ Simulink de modo a verificar através dos diversos resultados o potencial das soluções propostas.
This work presents hybrid structures for an uninterruptible power supply (UPS) with the integration of a photovoltaic system (PV). Currently, the safest way to supply energy to critical equipment or data processing system is established with the use of an online UPS. On other hand, normally it is not required to use the same security in a PV system. In this dissertation will present topologies for integration of both technologies in order to generate and provide quality power to critical loads. Considering the integration of the PV system in a UPS, therefore it may also work disconnected from the grid, as long as the energy produced by the PV is sufficient. The first of these solutions is based on a classical double conversion structure. However, it will be presented an alternative solution based on a multilevel conversion topology. This latter structure, proposes the use of two UPS connected by only one three- phase transformer of open windings, at the input and output of the system. The DC links are independent and connected to the respective control converters of the PV system and batteries. This new structure introduces many advantages such as high reliability in supplying power to critical loads and in the quality of the output waveform. In addition to the proposed structures, the corresponding control circuits will be presented. Both systems were simulated in Matlab/ Simulink in order to verify through various results the potential of the proposed solutions.
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Pedral, Jacques, and Josef Abriren. "Analys av lågspänningsfördelning till signalanläggningar." Thesis, KTH, Data- och elektroteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-192837.
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I denna rapport utreds hur systemdesignen av lågspänningsfördelningen för järnvägen kan kostnadseffektiviseras. I dagsläget har det utarbetats en norm kring systemdesignen som tenderar att efterbildas från år till år vilket har medfört brist på innovation inom området. Syftet med arbetet var att designa två typstationer med signalställverken M11 respektive M95, där placering samt nominell storlek av UPS:er skulle fastställas för att tillhandahålla en kostnadseffektiv lösning. Dessutom skulle kablage dimensioneras för typstationerna samt se över möjligheten att ersätta UPS:er med likriktarsystem. Stationerna baserades på två redan existerande driftplatser, Fagersta C (M11) och Skänninge (M95). Slutligen skulle olika energilagringsalternativ för UPS-system jämföras för att tillhandahålla det lämpligaste alternativet. Genom simuleringar och beräkningar i bland annat datorprogrammet El-Vis har lågspänningsfördelningen dimensionerats för typstationerna. Arbetet visar på att ett distribuerat UPS-system är att föredra ur ett ekonomiskt perspektiv gentemot ett centraliserat UPS-system. Vidare har det konstaterats att likriktarsystemet Rectiverter kan ersätta UPS:er samt att ackumulatorer är det mest passande energilagringsalternativet.This report identifies how the system design of low voltage power distribution of the railway can be more cost effective. In the current situation there is a norm on the system design that tends to be replicated each year. This has brought a lack of innovation in the field. The purpose of the thesis was to come up with two model stations with the interlocking system M11 respectively M95, where the positioning and nominal size of the UPS:s would be determined to provide a cost effective solution. Furthermore, the cable dimensioning of the model stations was computed as well as the possibility of replacing UPS-systems with rectifier-systems. The model stations were based on two already existing operating sites, Fagersta C (M11) and Skänninge (M95). Lastly, different energy storage alternatives for UPS-systems were compared to acquire the most appropriate choice. Through simulations and calculations in, inter alia, the computer program El-Vis, the low voltage power distribution was dimensioned for the model stations. The thesis shows that a distributed UPS-system is preferred in an economical point of view compared to a centralized UPS-system. Furthermore, the thesis establishes that the rectifier system Rectiverter can replace UPS:s. It also states that accumulators are the most suitable alternative for energy storage.
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Barden, Alisson Thomas. "Projeto e análise de controladores robustos aplicados a inversores trifásicos de fontes ininterruptas de energia (UPS)." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/141945.
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O objetivo principal deste trabalho é o desenvolvimento de controladores robustos baseados no princípio do modelo interno, em referenciais síncrono e estacionário, para aplicação ao estágio de saída de uma fonte ininterrupta de energia (UPS) a fim de minimizar a distorção na tensão de saída causada pela conexão de cargas não lineares balanceadas e desbalanceadas. A formulação em referencial estacionário (abc) é realizada através da aplicação de controladores com múltiplos modos ressonantes, a fim de se estabelecer erro nulo ao seguimento de referência senoidal e rejeição de distúrbios na tensão de saída devido às correntes com elevado conteúdo harmônico drenadas pelas cargas. Além disso, o controle é formulado em referencial síncrono (dq0) utilizando controladores Proporcional-Integral (PI) convencionais muito difundidos na maioria das aplicações comerciais de UPS. O projeto de ambos controladores é realizado utilizando uma metodologia de controle robusto com realimentação de estados, onde os parâmetros dos controladores são determinados através da resolução de um problema de otimização convexa sujeito a um conjunto de restrições na forma de desigualdades matriciais lineares (LMI). Uma análise comparativa de desempenho é realizada entre controladores com um modo ressonante (sintonizado na fundamental) e o PI em dq0, pois apresentam estruturas funcionalmente equivalentes sob a ótica do princípio do modelo interno aplicada a seus respectivos referenciais. Além do mais, demonstra-se a melhoria no desempenho com o uso dos controladores múltiplo ressonantes em referencial estacionário onde escolhe-se as frequências de ressonância de cada modo de maneira a suprimir os efeitos de harmônicas específicas na tensão de saída da UPS. A análise comparativa entre os controladores propostos é realizada através de simulações numéricas, utilizando os procedimentos de ensaio dinâmico e estático e as exigências estabelecidas pela norma internacional IEC 62040-3.The main objective of this work is the development of robust controllers based on the internalmodel principle, in synchronous and stationary frames, applied to the output stage of an uninterruptible power supply (UPS), in order to minimize the output voltage distortion caused by the connection of balanced and unbalanced nonlinear loads. The formulation in stationary abc-frame is accomplished through the aplication of a multiple resonant controller, so that, it is possible to achieve zero-error tracking of the sinusoidal reference and disturbances rejection on the output voltage due to the high amount of harmonic currents drained by the loads. Moreover, a controller in synchronous reference frame (dq0 axis) is formulated through the application of conventional Proportional-Integral (PI) controllers which are widely used in comercial UPS applications. The design of both controllers is formulated using a state-feedback robust controlmethod, in which the controller parameters are determined by solving a convex optimization problem subject to a set of LMI constraints. A comparative analysis on the performance of the single-mode resonant controller (tuned at the fundamental frequency) and the PI controller is performed, because these controllers are functionally equivalent in the sense of the internal model principle applied to their respective frames. Furthermore, the improvement in performance is demostrated with the use of multiple resonant controllers in stationary abc-frame where the resonance frequencies are chosen to suppress the effects of a specific harmonic in the UPS output voltage. The comparative analysis of the proposed controllers is performed through numerical simulations, making use of the dynamical and steady-state test methods and performance requirements defined by the IEC 62040-3 international stardard.
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Pan, Haibo 1973. "SMES for power quality improvement and uninterruptible power supply." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33342.
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The history of applied superconductor-based equipment in industry, especially in power system, is briefly reviewed. The thesis presents a development of a superconducting magnetic energy storage system for power quality improvement and uninterruptible power supply (PQ/UPS SMES). The configuration of such a system and its control concept are analyzed in full details. Evaluation tests of an SMES system operating on a simple power system are presented and analyzed. They validate the applicability of such a system, as an attractive alternative for power quality improvement and uninterruptable power supply.The PQ/UPS SMES system as well as the power network has been modeled using Matlab/Simulink simulation environment for convenience. The Simulink models of all relevant components are also presented. Finally, all the evaluation tests are also done in Simulink simulation environment.
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Annunziato, Rafael Christiano. "Projeto e implementação de método para conexão paralela de UPSs com compartilhamento de potência." Universidade Tecnológica Federal do Paraná, 2012. http://repositorio.utfpr.edu.br/jspui/handle/1/312.
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Este trabalho apresenta o projeto e a implementação prática de um método completo para ser utilizado na conexão de UPSs monofásicos em paralelo. Existe um algoritmo que executa o droop de fase/frequência, e um novo método que trabalha com e sem comunicação de dados entre os inversores. Quando a comunicação está ativa, um novo algoritmo é utilizado, inserindo um resistência virtual variável, junto com o compartilhamento de potência ativa, obtendo um baixo valor de THD (Total Harmonic Distortion) na tensão de saída e bom compartilhamento de potência. Quando a comunicação de dados não funciona, uma resistência virtual constante é inserida, aumentando a THD de saída com carga não-linear, mas ainda proporcionando um bom compartilhamento de potência ativa. A vantagem é poder obter um bom desempenho quando a comunicação de dados está operando, mas, no caso de sua falha, o sistema ainda funciona, proporcionando maior confiabilidade. A implementação possui um algoritmo de emulação de carga eletrônica, com o propósito de executar testes de produção, baseado no mesmo algoritmo de paralelismo, apenas mudando algumas variáveis.This work presents the design and experimental implementation of a complete paralleling method to be used for parallel single-phase UPSs connection. There is a algorithm that performs a phase/frequency droop, and a new method to work with or without data communication among the inverters. When communication is working, a new algorithm is used, inserting a variable virtual resistance in the output, along with active power sharing, obtaining a low output voltage THD (Total Harmonic Distortion) value and good power sharing. Without communication a constant virtual resistance is inserted, increasing the output THD with non-linear load, but still allowing a good active power sharing. The advantage is to obtain a good performance operation with communication, but, in case of communication failure, the system still works providing more reliability. The implementation have a electronic load emulation algorithm, with purpose to execute factory tests, based in the same parallelism algorithm, just changing some variables.
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Beber, DG. "DSP controlled three phase to single phase uninterruptible power supply." Master's thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/5244.
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Includes bibliographical references.With the increase in use of electronic equipment such as personal computers, network stations and AC drive conrollers, an increased "polution" of the AC mains has resulted in the form of unwanted harmonics generated by the switching currents associated with these devices. Combined with the problem of mains "pollution" is the problem of balancing a large number of single phase loads onto a three phase supply, such as in a large computer network. This has resulted in more frequent supply voltage failure, causing substantial data and financial loss and in the extreme case death due to hospital equipment not being powered. Thus the need for an uninterruptible power supply (UPS) which is capable of resolving these problems. Taking these considerations into account, a three to single phase converter topology was developed and tested, using a Texas Instruments TMS320F243 Digital Signal Processor (DSP) for control of the system. The topology is based on a technique that utilises minimal semiconductor devices whilst still allowing for sinusoidal current to be drawn from the mains supply.
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Zhang, Hai Bo. "High-frequency switching parallel processing topology for AC uninterruptible power supply." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ40215.pdf.
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Cheng, Limin. "A universal controller for a single-phase uninterruptible power supply system." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0001/MQ42361.pdf.
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Mikros, Efthimios. "Mitigation of EMI/RFI produced by a 1.2 kW uninterruptible power supply." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from the National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA273149.
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Thesis (M.S. in Systems Engineering) Naval Postgraduate School, September 1993.Thesis advisor(s): Adler, Richard William. "September 1993." Includes bibliographical references. Also available online.
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Karsli, V. M. "An investigation into real-time microcontrolled single phase uninterruptible power supply systems." Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637763.
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Recent developments in power electronic switching devices and microprocessors have led to power electronic systems with high efficiency and reliability. Today, high performance and low cost are the requirements to be met for most practical systems. This work describes the development of real-time based Uninterruptible Power Supply systems (UPS) which can operate on-line and off-line. Synchronous operation is an inevitable condition in off-line UPS systems. Here, back-synchronisation after a power failure is achieved automatically with the pre-set values. A new modified regular sampled symmetric pulse width modulation method has been developed, it has many advantages especially in low frequency applications. High switching frequency (18 kHz) reduces significantly the filtration and noise problems in UPS systems. Phase delay associated with transformer, filter, load, and control algorithm might cause drastic power failures in by-pass switches, thus to overcome this problem, phase shift control algorithms are developed. PID control algorithm is simplified for real-time on-line operation at high switching frequency. The complete system is based on a single Intel 80C196KC microcontroller chip and the developed software has the flexibility for further development. The developed system has been tested in the laboratory under linear load condition and the results are given. The test results are found to be satisfactory for most load conditions.
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Magozore, Caxton. "DSP phase angle controlled three phase to single phase uninterruptible power supply." Master's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/5177.
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Tate, D. "A microprocessor controlled error switching inverter used in the uninterruptible power supply environment." Thesis, University of Bath, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275883.
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Bengtsson, Tobias, and Håkan Hult. "Combining Solar Energy and UPS Systems." Thesis, KTH, Tillämpad termodynamik och kylteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-148042.
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Solar Power and Uninterruptible Power Supply (UPS) are two technologies that are growing rapidly. The demand for solar energy is mainly driven by the trend towards cheaper solar cells, making it economically profitable for a larger range of applications. However, solar power has yet to reach grid parity in many geographical areas, which makes ways to reduce the cost of solar power systems important. This thesis investigates the possibility and potential economic synergies of combining solar power with UPS systems, which have been previously researched only from a purely technical point of view. This thesis instead evaluates the hypothesis that a combined solar and UPS system might save additional costs compared to regular grid-tied systems, even in a stable power grid. The primary reason is that on-line UPS systems rectifies and inverts all electricity, which means that solar energy can be delivered to the DC part of the UPS system instead of an AC grid, avoiding the installation of additional inverters in the solar power system. The study is divided into three parts. The first part is a computer simulation using MATLAB, which has an explorative method and aims to simulate a combined system before experimenting physically with it. The second part consists of experiments on a physical prototype system based on basic UPS and solar power components. The third part is an economical assessment of investment costs and energy balances, comparing two separate systems (UPS and solar power separate) to one combined (UPS & solar power). The results from the prototype system show that adding solar power to an UPS system does not interfere with the UPS functionality in any major way, however for optimal performance some additional integration may be necessary. On the contrary, the additional power terminal that the solar panels constitute, can increase system performance during certain operational conditions. The result of the economic analysis shows that a combined system has potential for both a lower investment cost due to cheaper components and increased energy savings through lower conversion losses. The conclusion from the study is that a combined solar energy and UPS system is technically feasible. Furthermore, a combined system has clear economic advantages over two separate systems. This means that a combined system might be economically profitable even in situations where a separate system is not.Solenergi och avbrottsfri kraftförsörjning (UPS) är två tekniker som växer snabbt. Efterfrågan på solenergi ökar huvudsakligen på grund av den snabba utvecklingen mot billigare solceller, vilket lett till att solenergi blivit lönsamt i en större mängd applikationer. I många områden är solenergi dock fortfarande inte kostnadsmässigt konkurrenskraftigt jämfört med traditionella energikällor, vilket gör en fortsatt sänkning av kostnaderna för solenergi till en viktig fråga för solenergiindustrin. Detta examensarbete har som syfte att undersöka om det är tekniskt möjligt att kombinera solenergi med UPS-system samt potentialen för ekonomiska synergier med denna kombination. Tidigare forskning inom området har endast undersökt denna kombination från en rent teknisk synvinkel. Detta examensarbete driver istället hypotesen att ett kombinerat solenergi- och UPS-system kan leda till större kostnadsbesparingar jämfört med ett traditionellt nätanslutet solenergisystem, även i ett stabilt elnät som i Sverige. En on-line UPS skyddar en känslig last genom att kontinuerligt likrikta och sedan åter växelrikta inkommande ström för att därmed både isolera lasten från nätet samt höja strömkvalitén. I UPS-systemet finns därmed en likströmsdel dit solpanelerna direkt kan kopplas istället för att skicka den genererade solenergin ut på elnätet. Därmed undviks inköp och installation av sol-växelriktare i solenergisystemet. Studien är uppdelad i tre delar. Första delen är en datorsimulering i MATLAB och syftar till att explorativt undersöka det kombinerade systemet för en optimerad design innan fysiska experiment utförs. Den andra delen av studien utgörs av experiment på ett fysiskt prototypsystem baserat på ett principiellt UPS- och solenergisystem. Den tredje delen av studien är en ekonomisk analys av både investeringskostnader och energibalanser som jämför ett kombinerat system (UPS & sol) med två separata system (UPS & sol separat). Resultaten från prototypsystemet visar att påkopplandet av solceller i en principiell UPS har mycket låg påverkan på UPS-systemets funktionalitet, samt att solcellerna som en extra energikälla under vissa driftförhållanden kan ha en positiv påverkan på UPS-systemet. För optimal prestanda kan dock en viss integration av systemen krävas. Resultatet från den ekonomiska analysen visar att ett kombinerat system har potential att sänka investeringskostnaden genom billigare komponenter. Ett kombinerat system kan även leda till en högre energibesparing jämfört med ett nätanslutet solenergisystem eftersom konverteringsförlusterna i UPS-systemet sjunker i det kombinerade systemet. Slutsatsen av studierna är att ett kombinerat solenergi- och UPS-system är tekniskt möjligt. Dessutom finns betydande ekonomiska synergier med ett kombinerat system. Detta innebär att ett kombinerat system kan vara lönsamt även i fall där ett separat solelsystem inte är det.
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Humphrey, Daniel Alan. "Fuel cells as a backup energy source for high availability network servers." Texas A&M University, 2008. http://hdl.handle.net/1969.1/86024.
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This thesis proposes an uninterruptible power supply, UPS for high availability
servers with fuel cells as its back up energy source. The system comprises a DC to DC
converter designed to accommodate the fuel cellâ s wide output voltage range. A server
power supply is specified, designed and simulated for use with this UPS. The UPS
interfaces internal to the server power supply, instead of providing standard AC power.
This topology affords enhanced protection from faults and increases overall efficiency of
the system by removing power conversions. The UPS is simulated with the designed
power supply to demonstrate its effectiveness.
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Marwali, Mohammad Nanda. "Digital control of pulse width modulated inverters for high performance uninterruptible power supplies." The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1100484647.
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Beran, Edward W. "An electromagnetic interference analysis of uninterruptible power supply systems in a data processing environment." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02Dec%5FBeran.pdf.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 2002.Thesis advisor(s): Richard W. Adler, Wilbur R. Vincent. Includes bibliographical references (p. 103-104). Also available online.
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Marwali, Mohammad Nanda Rahmana. "Digital control of pulse width modulated inverters for high performance uninterruptible power supplies." Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1100484647.
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Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains xviii, 224 p.; also includes graphics. Includes bibliographical references (p. 199-211).
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Olsson, Fredrik. "Konstruktion av UPS-modul." Thesis, Linköping University, Department of Electrical Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1397.
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This master thesis describes the development of an UPS module. UPS is an acronym for Uninterruptable Power Supply. The UPS module has been developed at the company AerotechTelub AB. The UPS module delivers the necessary voltage and current in case of a power interrupt. If a power interrupt occur, the computer system has one to three minutes available to store data and shut down correctly.
The UPS module consists of two parallel systems. Every system is built out of four parts. Part one consists of batteries and safety circuits, part two charges the batteries, partthree is a control unit, and part four delivers the voltage and current. The delivered voltage is 5 V and the current is 4 A.
Tests and verifications showed that the UPS module could supply a computer system with power for about one minute. The tests have been performed in a lab at AerotechTelub AB.
The UPS module is supposed to be mounted in a cassette. The cassette is then inserted in the computer system through a hole in the chassis. Thereby an opening of the computer system is avoided when the module is connected.
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Janáč, Josef. "Spínačová technologie v záložních zdrojích." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218405.
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Subject of this master’s thesis is ideological proposal of the UPS able to protect electronic equipment against short-term disruptions of network supply voltage. The entire facility is proposed on the basis of modern switching technologies . Properties of critical parts of the proposal are simulated and debugged with help of PSpice circuit simulator software. In project is also included the necessary design documents. The project is completed by realization of functional facility, measurement of it’s basic properties and comparison with assumption results.
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Barnes, Lemuel Gregory. "Voltage-source inverter output waveform compensation using adaptive intelligent control /." This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-10192006-115605/.
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Ghetti, Frederico Toledo. "Análise de variações topológicas aplicadas a uma UPS tipo delta monofásica." Universidade Federal de Juiz de Fora (UFJF), 2009. https://repositorio.ufjf.br/jspui/handle/ufjf/3505.
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
É apresentado, neste trabalho, um estudo sobre topologias alternativas de fontes ininterruptas de energia do tipo Delta, para o emprego em cargas monofásicas de até 1kVA. O estudo prevê a inserção de um conversor CC-CC entre o conversor shunt e o banco de baterias. Tal modificação em relação à UPS do tipo Delta convencional otimiza o projeto do banco de baterias e requisita um menor número de células em série para sua confecção. Além disso, a proposta elimina o uso de transformadores de baixa freqüência, considerados em alguns trabalhos anteriores, o que também contribui para a redução do peso e volume do sistema. Duas diferentes topologias para o conversor CC-CC foram investigadas e comparações de desempenho e viabilidade foram realizadas. A topologia que apresentou melhor desempenho nos quesitos custo, volume e peso, foi selecionada para testes em bancada. Ao final, resultados simulados e práticos são apresentados para validação do modelo.
This dissertation presents a study on single-phase Delta-UPS topological alternatives for low power and low cost applications. The proposed topology has a DC-DC converter connected between the shunt inverter and the battery bank/series converter DC terminals, respectively. This modification will allow the downsizing of the DC battery bank as well as the removing of the series converter transformer. Two different topologies of the DC DC converter were investigated and a comparative study among them will be accomplished. Simulation results are presented and experimental results will be included to validate the proposed study.
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Aminou, Moussavou Anges Akim. "Modelling and analysis of microgrid control techniques for grid stabilisation." Thesis, Cape Peninsula University of Technology, 2014. http://hdl.handle.net/20.500.11838/1184.
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Thesis submitted in fulfilment of the requirements for the degree
Master of Technology: Electrical Engineering
in the Faculty of Engineering
at the
Cape Peninsula University of Technology
2014In recent times, renewable energy-based distributed generation (DG) has captivated the industrial sector and on a global scale this has become a leading research area. Distributed generation using wind, solar energy or biomass as a source of energy can produce electricity on a small scale. Therefore, there is a strong focus on using renewable energy as a safe alternative source of energy, especially because it can in future play a dominant role in the world’s energy production and help to tackle the increase of global warming caused by fossil energy. However, a major problem facing renewable energies is that they are highly dependent on weather conditions. Since the power generated by DG, as well as consumption, depends on the weather conditions, irregularity of production and consumption leads to frequency and voltage fluctuations, and it can become difficult to determine and monitor consumer usage at any given time. Distributed generation can then be subjected to discrepancies in consumer usage and this can lead to severe overloading. As a result, microgrids powered by DG, operating in a single, stand-alone controllable system mode, face new challenges in terms of balancing a cluster of loads. Balancing a cluster of loads by making sure at all times that the entire system operates without overloading, is an essential requirement for the proper operation of a power system. The microgrid load considered in this project is the sum of sensitive and non-sensitive loads, respectively 5 kW and 100 kW, which constitute load requirement of one village; this total load required by a number of villages is called a cluster load. Depending on the input power generated by a DG-based photovoltaic (PV) system, these loads can be controlled using a logic control switch (LCS). When the power produced is less than the minimum load required by a component of a cluster, overloading occurs. The purpose of using an LCS is to ensure that a stable system is maintained under various loads and resource conditions. An LCS is used to continuously monitor and adjust load through circuit breakers. It is a good alternative to load balancing for a cluster of villages in rural area where a microgrid is operating in stand-alone mode. The focus of this research is to design a photovoltaic system with a maximum capacity of 1 MW providing power to a cluster of rural villages, and operating in stand-alone mode, and then to apply different control techniques (droop control, dq0 reference frame + proportional integral (PI) controller, and PI controller alone) at the inverter terminal of the PV system, in order to evaluate the stability of the output voltage. Another goal of the research is to develop an energy management system (EMS) algorithm to support the PV system in reducing loads. Therefore, a iii stable system under various load and resource conditions, as well as suitable control mechanisms are required to model a PV system. There is a need for the modelling of a PV array using a physical modelling block in MATLAB (SIMULINK) software. The state flow provided by SIMULINK is used in this project to develop an algorithm for load balancing. The state flow gives possibilities of modelling complex algorithms by combining graphical and tabular representations to create sequential decision logic, derived from state transition diagrams and tables, flow charts and truth tables. Furthermore, the design of a microgrid using photovoltaic DG and an energy management system, has been developed. The present work mainly consists of a stand-alone microgrid operation, where the power generated must be equal to the load power. In addition, different control methods, consisting of a dq0 reference frame + PI controller, are analysed at the invertor terminal. Subsequently an LCS algorithm is developed; this is required to maintain the system within certain limits and prevents overloading. LCS algorithms are based on a flowchart and allow switching automatically selected loads, depending on the power (solar radiation) available. In addition, a flow chart provides an easy way of using a graphical transition state and state chart to establish a set of rules for the system. The simulation results show that both droop control and a dq0 reference frame + PI controller are much better than a PI controller alone; these results also compared well with similar studies found in the literature. Also, these results are further improved with an EMS in order to maintain the output voltage of the microgrid, by switching on and off certain loads depending on the input power. The modelling of the microgrid using DG, based on photovoltaic systems with a maximum capacity of 1 MW, supports and improves the PV system by reducing loads. Moreover, droop control, and dq0 transformation + PI control present a better result than PI controller alone.
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Mrázek, Petr. "Záložní zdroj (UPS)." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2015. http://www.nusl.cz/ntk/nusl-221364.
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The thesis deals with Uninterruptible Power Supply (UPS) and associated problems of backup power in case of unexpected outages of electricity. Start of work is dedicated to limitation of the electricity supplies, as well as their causes and consequences. Furthermore, brief history of UPS and subsequently distinguish between UPS’s architectures. There is also a description of the energy sources such as batteries, flywheels or fuel cells. Part of thesis describes security of electricity supply in health care facilities, including requirements for emergency power. The own design of UPS is described in the end.
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Janse, van Rensburg Jan Jacobus. "Development of a flywheel energy storage system : uninterrupted power supply (FLY-UPS) / Jan Jacobus Janse van Rensburg." Thesis, North-West University, 2007. http://hdl.handle.net/10394/2322.
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The School of Electrical, Electronic and Computer Engineering is in the process of establishing an active magnetic bearing (AMB) and high speed permanent magnet synchronous machine (PMSM) laboratory. This is done to gain knowledge on AMB, flywheel and high speed PMSM technologies. Some of the advantages of using AMBs are: no mechanical wear or friction, no need for lubrication, active vibration control and unbalance compensation. This project’s purpose is the development of an AMB suspended flywheel energy storage system. This system should be able to store energy for a certain period with minimal losses. Energy stored should then be readily available for use by a load such as a personal computer. This system will be similar to a conventional uninterrupted power supply (UPS). Instead of using a lead-acid cell to store the energy, a flywheel is used. The acronym for the system is FLY-UPS (FLYwheel Uninterrupted Power Supply). Charging the system should not take longer than 5 minutes using 2000 W of power. One of the system’s main function is to protect sensitive equipment from mains power spikes and short power interruptions. This system should be able to supply 2000Wfor at least 3 minutes, allowing enough time to switch sensitive equipment off in a controlled manner. Two heteropolar radial AMBs, one axial AMB, a high speed permanent magnet synchronous machine (PMSM) for propulsion and generating purposes, and a disc that will serve as the flywheel is the main components of this system. This system should be operated at a rotational speed of 30000 rpm. Development of this system facilitates testing of control algorithms and establishes knowledge on AMBs and flywheels. An important outcome of this project is delivering a working FLY-UPS system. Future research on advanced control techniques, low loss AMB’s and flywheel design optimising is made possible with the development of the FLY-UPS system.
An in depth investigation into rotor-dynamics and flywheels has been conducted. Research
into flywheels is relevant because recently there has been a growing focus on renewable energy. A modular approach was used in the design of the FLY-UPS system. A rotor-dynamic analysis has been done on the rotor/flywheel assembly, resulting in predicted displacements and the critical frequencies of the rotor/flywheel assembly. Analytical and computer aided strength analysis has been done on the rotor/flywheel assembly. Both the analytical and computer aided strength analysis concludes that the rotor/flywheel achieves the minimum factor of safety of 1.5. Measured critical frequencies correlate to the predicted critical frequencies. Predicted displacement does not correlate to the measured displacement. This is attributed to insufficient balancing of the rotor/flywheel. Rotational speed of the rotor/flywheel is currently limited to 7000 rpm, in stead of the required 30000 rpm, due to the greater displacements.
Further investigation into the reasons for the greater displacement is still required. A possible
solution to this problem is re-balancing the rotor/flywheel assembly. Further research is required on the dynamic stiffness of the AMBs. A delevitation system needs to be developed. Research has to be done on the accurate prediction of the behaviour of a rotor during delevitation. An investigation into the development of a carbon-fibre composite flywheel needs to be conducted. Measured against the outcomes, the project has been a success.Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2008.
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Oliveira, Alberto Quialheiro. "Modelo de leilão multiperíodo para sistemas hidrotérmicos em mercados pool de energia do dia seguinte /." Bauru, 2016. http://hdl.handle.net/11449/141893.
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Orientador: Leonardo NepomucenoBanca: Marcelo Augusto Cicogna
Banca: Edlaine Martins Soler
Resumo: Neste trabalho propõe-se um modelo de leilão multiperíodo para um mercado pool do dia seguinte de sistemas hidrotérmicos, que leve em consideração as restrições intertemporais do sistema termelétrico (e.g. potência máxima disponível e limites de rampa e período mínimo de operação e desligamento) e restrições hidráulicas (e.g. defluência, volume e balanço de água, altura de queda, alturas de montante e jusante do reservatório, limites de rampa de vazão defluente e função de produção). Também foram introduzidas no modelo as restrições de rede de transmissão, tais como o balanço e limites de fluxo de potência e representação das perdas. São descritas as técnicas de linearização das funções de altura de queda líquida, função de produção e função de perdas no sistema de transmissão. O modelo proposto é formulado como um problema de programação linear inteiro-misto, tendo sido resolvido utilizando as plataformas GAMS - CPLEX e IBM ILOG CPLEX Optimization Studio. Os resultados apresentados têm como foco principal a análise do impacto das restrições hidráulicas nos preços de equilíbrio de mercado e no despacho de geração de sistemas hidrotérmicos. Mostra-se que a operação de uma cascata hidráulica para o dia seguinte é orientada com base nas ofertas fornecidas pelas companhias geradoras no mercado de energia.
Abstract: This work presents a brief description of an energy market structure, as well as its agents, economic division and service and time horizon classification. The Brazilian mar-ket, single-period and multiperiod auction are also described, as much as a concise presen-tation of a hydroelectric generation system. It's proposed for a day-ahead pool market, a multiperiod auction for hydrothermal system which takes into account the intertempo-ral constraints from a thermoelectric system (e.g. maximum available power output and ramp rate limits, minimum up and down time) and hydraulic constraints (e.g. defluence, volume and water balance, net head, forebay and tailrace levels of reservoir, water release ramp rate limits and the unit performance curves). It was also associated to the problem the transmission constraints, such as balance and flow power limits and power loss. On account of being a problem with such features, the linearization techniques of the net head, unit performance curves and power loss function are described. The proposed mo-del is based on a mixed integer linear programming problem, which used the GAMS -CPLEX and IBM ILOG CPLEX Optimization Studio to its resolution. Finally there are two reported situations to analyze the impact of the hydraulic constrains on the bidding prices, as well as the in˛uence of the selling prices on the total spillage of the hydroelectric plants. The model is projected for a hydro predominance plant cascade.
Mestre
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Bayram, Yasemin Çalış Hakan. "PIC kontrollü kesintisiz güç kaynağı tasarımı ve gerçekleştirilmesi /." Isparta : SDÜ Fen Bilimleri Enstitüsü, 2007. http://tez.sdu.edu.tr/Tezler/TF01126.pdf.
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Welgemoed, Frans Marx. "Shunt reactive compensation of voltage dips and unbalance." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5315.
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Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: The use of power electronic converters provides a more efficient, accurate and dynamic solution to reactive compensation. In this thesis the application of power electronic converters to shunt reactive compensation will be discussed. In particular voltage dips and voltage unbalance are considered as both can be mitigated by means of shunt reactive compensation. A pre-existing uninterruptible power supply is adapted to operate as a shunt reactive compensator. The uninterruptible power supply consists of a 250 kVA three phase voltage source inverter. The modifications are limited to software and control algorithms that do not alter the normal operation of the uninterruptible power supply. Control algorithms are designed and discussed in detail. A typical double loop control strategy is implemented on the power electronic converter. The inner loop consists of a dead-beat current controller. The outer loop consists of three proportional and integral controllers controlling the DC-bus voltage, AC voltage and voltage unbalance respectively. Voltage dips and unbalance are compensated for using only reactive power. Focus is placed on producing a result can be used easily in practice.
AFRIKAANSE OPSOMMING: Drywings elektroniese omsetters wat gebruik word vir newe reaktiewe kompensasie lewer meer effektiewe, akkurate en dinamiese resultate. In hierdie tesis word die toepassing van drywings elektroniese omsetters vir newe reaktiewe kompensasie bespreek. Daar word meer spesifiek na spannings duike en spannings wanbalans gekyk aangesien albei met newe reaktiewe kompensasie verminder kan word. ’n Bestaande nood kragbron is aangepas om as n newe reaktiewe kompenseerder te funksioneer. Die nood kragbron bestaan hoofsaaklik uit ’n 250 kVA drie fase omsetter spanningsbron. Die aanpassings is beperk tot sagteware en beheer algoritmes wat nie die oorspronklike funksionaliteit van die nood krag bron beinvloed nie. Beheer algoritmes word ontwerp en deeglik bespreek. ’n Tipiese dubbel lus beheer strategie word op die drywings elektroniese omsetter toegepas. Die binnelus bestaan uit ’n voorspellende stroom beheerder. Die buite-lus bestaan uit drie proportioneel en integraal beheerders wat onderskeidelik die GS-bus spanning, WS spanning en spanning wanbalans reguleer. Spannings duike en wanbalans is verminder deur slegs reaktiewe drywing te gebruik. Die doel was ook om ’n prakties bruikbare resultaat te lewer.
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Tomášek, Petr. "Zajištěné napájení vlastní spotřeby parní elektrárny." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-217821.
Full textAbstract:
This thesis examines issues connected to safe uninterruptible power supplies. The term safe uninterruptible power supply is used for an aggregate of devices providing power for appliances that participate in safe rapid shutdown of a power plant in case power from a usual source fails. The thesis is divided into two parts – theoretical and practical. Theoretical part deals with possibilities and ways of realizing an aggregation of safe uninterruptible power supply. Various devices that can appear in the section of a safe uninterruptible power supply are listed and each device is characterized. Appliances that can be provided for by the sources of safe uninterruptible power supply are mentioned as well. These appliances are listed in accordance with ČSN standard nr. 381120. The theoretical part concludes with new trends in realization of safe uninterruptible power supplies. One of these sources is a clean source technology that can also be implemented in various ways. Practical part contains a suggestion of a safe uninterruptible power supply for particular steam power plant. This suggested safe uninterruptible power supply consists of rectifiers, batteries, inverters and a dieselgenerator. Calculated parameters of each device at the conclusion of the practical part are followed by a diagram of the suggested section of safe uninterruptible power supply.
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Badeda, Julia [Verfasser], Dirk Uwe [Akademischer Betreuer] Sauer, and Antonello [Akademischer Betreuer] Monti. "Modeling and steering of multi-use operation with uninterruptible power supply systems utilizing the example of lead-acid batteries / Julia Badeda ; Dirk Uwe Sauer, Antonello Monti." Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/121517148X/34.
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Ohn, Sungjae. "Circuits and Modulation Schemes to Achieve High Power-Density in SiC Grid-connected Converters." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/89550.
Full textAbstract:
The emergence of silicon-carbide (SiC) devices has been a 'game changer' in the field of power electronics. With desirable material properties such as low-loss characteristics, high blocking voltage, and high junction temperature operation, they are expected to drastically increase the power density of power electronics systems. Recent state-of-the-art designs show the power density over 17 ; however, certain factors limit the power density to increase beyond this limit. In this dissertation, three key factors are selected to increase the power density of SiC-based grid-connected three-phase converters. Throughout this dissertation, the techniques and strategies to increase the power density of SiC three-phase converters were investigated.
Firstly, a magnetic integration method was introduced for the coupled inductors in the interleaved three-phase converters. Due to limited current-capacity compared to the silicon insulated-gate bipolar transistors (Si-IGBTs), discrete SiC devices or SiC modules, operate in parallel to handle a large current. When three-phase inverters are paralleled, interleaving can be used, and coupled inductors are employed to limit the circulating current. In Chapter 2, the conventional integration method was extended to integrate three coupled inductors into two; one for differential-mode circulating current and the other for common-mode circulating current. By comparing with prior research work, a 20% reduction in size and weight is demonstrated.
From Chapter 3 to Chapter 5, a full-SiC uninterruptible power supply (UPS) was investigated. With the high switching frequency and fast switching dynamics of SiC devices, strategies on electromagnetic inference become more important, compared to Si-IGBT based inverters. Chapter 3 focuses on a common-mode equivalent circuit model for a topology and pulse width modulation (PWM) scheme selection, to set a noise mitigation strategy in the design phase. A three terminal common-mode electromagnetic interference (EMI) model is proposed, which predicts the impact of the dc-dc stage and a large battery-rack on the output CM noise. Based on the model, severe deterioration of noise by the dc-dc stage and battery-rack can be predicted. Special attention was paid on the selection of the dc-dc stage's topology and the PWM scheme to minimize the impact. With the mitigation strategy, a maximum 16 dB reduction on CM EMI can be achieved for a wide frequency range.
In Chapter 4, an active PWM scheme for a full-SiC three-level back-to-back converter was proposed. The PWM scheme targets the size reduction of two key components: dc-link capacitors and a common-mode EMI filter. The increase in switching frequency calls for a large common-mode EMI filter, and dc-link capacitors in the three-level topology may take a considerable portion in the total volume. To reduce the common-mode noise emission, different combinations of the voltage vectors are investigated to generate center-aligned single pulse common-mode voltage. By such an alignment of common-mode voltage with different vector combinations, noise cancellation between the rectifier and the inverter can be maximally utilized, while the balancing of neutral point voltage can be achieved by the transition between the combinations. Also, to reduce the size of the dc-link capacitor for the three-level back-to-back converter, a compensation algorithm for neutral point voltage unbalance was developed for both differential-mode voltage and the common-mode voltage of the ac-ac stage. The experimental results show a 4 dB reduction on CM EMI, which leads to a 30% reduction on the required CM inductance value. When a 10% variation of neutral point voltage can be handled, the dc-link capacitance can be reduced by 56%.
In Chapter 5, a 20 kW full-SiC UPS prototype was built to demonstrate a possible size-reduction with the proposed PWM scheme, as well as a selection of topologies and PWM schemes based on the model. The power density and efficiency are compared with the state-of-the-art Si-IGBT based UPSs.
Chapter 6 seeks to improve power density by a change in a modulation method. Triangular conduction mode (TCM) operation of the three-level full-SiC inverter was investigated. The switching loss of SiC devices is reported to be concentrated on the turn-on instant. With zero-voltage turn-on of all switches, the switching frequency of a three-level three-phase SiC inverter can be drastically increased, compared to the hard-switching operation. This contributes to the size-reduction of the filter inductors and EMI filters. Based on the design to achieve a 99% peak efficiency, a comparison was made with a full-SiC three-level inverter, operating in continuous conduction mode (CCM), to verify the benefit of the soft switching scheme on the power density. A design procedure for an LCL filter of paralleled TCM inverters was developed. With 3.5 times high switching frequency, the total weight of the filter stage of the TCM inverter can be reduced by 15%, compared to that of the CCM inverter.
Throughout this dissertation, techniques for size reduction of key components are introduced, including coupled inductors in parallel inverters, an EMI filter, dc-link capacitors, and the main boost inductor. From Chapter 2 to 5, the physical size or required value of these key components could be reduced by 20% to 56% by different schemes such as magnetic integration, EMI mitigation strategy through modeling, and an active PWM scheme. An optimization result for a full-SiC UPS showed a 40% decrease in the total volume, compared to the state-of-the-art Si-IGBT solution. Soft-switching modulation for SiC-based three-phase inverters can bring a significant increase in the switching frequency and has the potential to enhance power-density notably. A three-level three-phase full-SiC 40 kW PV inverter with TCM operation contributed to a 15% reduction on the filter weight.Doctor of Philosophy
The power density of a power electronics system is regarded as an indicator of technological advances. The higher the power density of the power supply, the more power it can generate with the given volume and weight. The size requirement on power electronics has been driven towards tighter limits, as the dependency on electric energy increases with the electrification of transportation and the emergence of grid-connected renewable energy sources. However, the efficiency of a power electronics system is an essential factor and is regarded as a trade-off with the power density. The size of power electronics systems is largely impacted by its magnetic components for filtering, as well as its cooling system, such as a heatsink. Once the switching frequency of power semiconductors is increased to lower the burden on filtering, more loss is generated from filters and semiconductors, thus enlarging the size of the cooling system. Therefore, considering the efficiency has to be maintained at a reasonable value, the power density of Si-based converters appears to be saturated. With the emergence of wide-bandgap devices such as silicon carbide (SiC) or gallium nitride (GaN), the switching frequency of power devices can be significantly increased. This is a result of superior material properties, compared to Si-based power semiconductors. For grid-connected applications, SiC devices are adopted, due to the limitations of voltage ratings in GaN devices. Before commercial SiC devices were available, the power density of SiC- based three-phase inverters was expected to go over 20 𝑘𝑊 𝑑𝑚3 ⁄ . However, the state-of-the art designs shows the power density around 3 ~ 4 𝑘𝑊 𝑑𝑚3 ⁄ , and at most 17 𝑘𝑊 𝑑𝑚3 ⁄ . The SiC devices could increase the power density, but they have not reached the level expected. The adoption of SiC devices with faster switching was not a panacea for power density improvement. This dissertation starts with an analysis of the factors that prevent power density improvement of SiC-based, grid-connected, three-phase inverters. Three factors were identified: a limited increase in the switching frequency, large high-frequency noise generation to be filtered, and smaller but still significant magnetic components. Using a generic design procedure for three-phase inverters, each chapter seeks to frame a strategy and develop techniques to enhance the power density. For smaller magnetic components, a magnetic integration scheme is proposed for paralleled ac-dc converters. To reduce the size of the noise filter, an accurate modeling approach was taken to predict the noise phenomena during the design phase. Also, a modulation scheme to minimize the noise generation of the ac-ac stage is proposed. The validity of the proposed technique was verified by a full-SiC three-phase uninterruptible power supply with optimized hardware design. Lastly, the benefit of soft-switching modulation, which leads to a significant increase in switching frequency, was analyzed. The hardware optimization procedure was developed and compared to hard-switched three-phase inverters.
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Kanduri, Venkata Ramanujam. "Distributed generation impact on fault response of a distrubution [i.e., distribution] network." Master's thesis, Mississippi State : Mississippi State University, 2004. http://library.msstate.edu/etd/show.asp?etd=etd-11122004-151757.
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Gray, Matthew Alan. "A comparative analysis of proportional-integral compensated shunt active power filters." Master's thesis, Mississippi State : Mississippi State University, 2004. http://library.msstate.edu/etd/show.asp?etd=etd-11092004-083404.
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Dóša, Vladimír. "Výstavba datových center." Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2011. http://www.nusl.cz/ntk/nusl-223046.
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This thesis presents and describes new global trends among build and operation of datacenters. Further it contains practical application of particular examples, and the theory is supplemented by new findings from given field.
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Trůčka, Martin. "Návrh zajištění bezpečnosti DC v silové infrastruktuře a jeho dopad na ekonomiku podniku." Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2010. http://www.nusl.cz/ntk/nusl-222587.
Full textAbstract:
The aim of this thesis is a description of a proposal to ensure safety of DC in power infrastructure and its impact on economics of an enterprise. The first part is focused on the analysis of the whole situation. The work also contains other possibilities of solution with respect to theoretical resources. The attention is also drawn to a particular procedure to minimize the financial loss of the company caused by a power failure and to a plan for providing maximum protection against this power failure.
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Aucamp, Christiaan Daniël. "Model predictive control of a magnetically suspended flywheel energy storage system / Christiaan Daniël Aucamp." Thesis, North-West University, 2012. http://hdl.handle.net/10394/8601.
Full textAbstract:
The goal of this dissertation is to evaluate the effectiveness of model predictive control (MPC)
for a magnetically suspended flywheel energy storage uninterruptible power supply (FlyUPS).
The reason this research topic was selected was to determine if an advanced control technique
such as MPC could perform better than a classical control approach such as decentralised
Proportional-plus-Differential (PD) control.
Based on a literature study of the FlyUPS system and the MPC strategies available, two MPC
strategies were used to design two possible MPC controllers were designed for the FlyUPS,
namely a classical MPC algorithm that incorporates optimisation techniques and the MPC
algorithm used in the MATLAB® MPC toolbox™. In order to take the restrictions of the system
into consideration, the model used to derive the controllers was reduced to an order of ten
according to the Hankel singular value decomposition of the model.
Simulation results indicated that the first controller based on a classical MPC algorithm and
optimisation techniques was not verified as a viable control strategy to be implemented on the
physical FlyUPS system due to difficulties obtaining the desired response. The second
controller derived using the MATLAB® MPC toolbox™ was verified to be a viable control
strategy for the FlyUPS by delivering good performance in simulation.
The verified MPC controller was then implemented on the FlyUPS. This implementation was
then analysed in order to validate that the controller operates as expected through a
comparison of the simulation and implementation results. Further analysis was then done by
comparing the performance of MPC with decentralised PD control in order to determine the
advantages and limitations of using MPC on the FlyUPS.
The advantages indicated by the evaluation include the simplicity of the design of the controller
that follows directly from the specifications of the system and the dynamics of the system, and
the good performance of the controller within the parameters of the controller design. The
limitations identified during this evaluation include the high computational load that requires a
relatively long execution time, and the inability of the MPC controller to adapt to unmodelled
system dynamics.
Based on this evaluation MPC can be seen as a viable control strategy for the FlyUPS, however
more research is needed to optimise the MPC approach to yield significant advantages over
other control techniques such as decentralised PD control.Thesis (MIng (Computer and Electronic Engineering))--North-West University, Potchefstroom Campus, 2013
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Barnes, Lemuel Gregory III. "Voltage-source inverter output waveform compensation using adaptive intelligent control." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/39997.
Full textAbstract:
A single-layer neural network-based voltage compensation technique which generates minimum-distortion sinusoidal output voltages from a three-phase PWM inverter used for uninterruptible power supplies (UPS) is described. The proposed compensation technique is implemented in a microprocessor-based controller constructed in the stationary d-q frame where the controller sampling rate is twice the inverter switching frequency. The structure of a feed-forward artificial neural network connects network inputs and outputs through multiple linear or nonlinear
neuron models, and processes these input/output data associations in a
parallel distributed manner. Network inputs in the form of UPS load voltage commands and load current feedback are propagated forward in the network each controller sampling period generating the inverter output voltage commands, the network outputs, which are converted to three phase inverter switching Signals using the space vector PWM waveform generation process.Ph. D.
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Venturini, William Alegranci. "Fonte ininterrupta de energia trifásica de alto desempenho sem transformador com dupla funcionalidade do estágio de entrada e sistema de controle digital." Universidade Federal de Santa Maria, 2016. http://repositorio.ufsm.br/handle/1/8594.
Full textAbstract:
Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorThis master s thesis proposes a three-phase transformerless double-conversion UPS with digital control system and reduced overall cost. The topology is composed of an input stage, a battery bank, an inverter, an auxiliary circuit and transfer switches. The input stage assumes the three-phase rectifier function with LCL filter in normal operation mode and is responsible for discharge the battery bank in backup mode. This configuration reduces the system cost since an available circuit is used to discharge the battery bank. In conventional double-conversion UPS topologies the input stage remains inactive during the backup mode and an additional circuit is employed for this purpose. The auxiliary circuit is formed by an inductor and a switching leg and is used as a battery charger during normal operation mode and is additionally used to balance the bus capacitors voltages in backup mode. In this configuration, the auxiliary circuit can be designed for only a fraction of the UPS rated power, also providing lower total system cost. Transfer switches change the configuration of the input stage and the auxiliary circuit according to the UPS operating mode. The detailed operation of the topology, modelling, digital control structure, and the results obtained by simulation are showed. Finally a 20 kVA prototype is implemented and experimental results are acquired for the validation of the employed design methodology as well as the proposed circuit functionality.
Esta dissertação de mestrado propõem uma topologia de fonte ininterrupta de energia (UPS - Uninterruptible Power Supplies) trifásica de dupla conversão sem transformador com custo reduzido e sistema de controle digital. A UPS proposta é composta por um estágio de entrada, um banco de baterias, um inversor, um circuito auxiliar e chaves de transferência. O estágio de entrada assume a função de retificador trifásico com filtro LCL em modo normal de operação da UPS e é responsável pela descarga do banco de baterias em modo bateria de operação. Esta configuração reduz o custo do sistema, pois permite que seja aproveitado um circuito disponível e dimensionado para a potência nominal da UPS para a descarga do banco de baterias. Em topologias convencionais de UPSs de dupla conversão o estágio de entrada permanece ocioso durante este modo de operação e um circuito adicional é empregado para este fim. O circuito auxiliar é formado por um indutor e um braço de interruptores e é utilizado como carregador de baterias em modo normal de operação e adicionalmente é utilizado para realizar o equilíbrio das tensões dos capacitores de barramento em modo bateria. Com esta configuração, o circuito auxiliar pode ser dimensionado para apenas uma fração da potência nominal da UPS, propiciando também a redução do custo total do sistema. As chaves de transferência alteram as configurações do estágio de entrada e do circuito auxiliar de acordo com o modo de operação da UPS. É apresentada a operação detalhada da topologia, a modelagem, a estrutura de controle digital utilizada e os resultados obtidos via simulação. Por fim, um protótipo de 20 kVA é implementado e resultados experimentais são adquiridos para a validação da metodologia de projeto empregada bem como da funcionalidade do circuito proposto.
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Rocha, Fabio Dalla Vecchia. "Carregador de baterias bidirecional com tranformador planar." Universidade Tecnológica Federal do Paraná, 2013. http://repositorio.utfpr.edu.br/jspui/handle/1/653.
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CAPESEste trabalho traz um estudo da aplicação do conversor Full-Bridge bidirecional como um carregador de banco de baterias em um barramento CC de fontes de energia renováveis. O problema principal destas fontes é que são sazonais e não oferecem uma continuidade de fornecimento de potência. Assim, o uso de banco de baterias, conectado a um barramento CC compartilhado com outras fontes renováveis traz contribuições na continuidade do fornecimento de energia. O conversor proposto neste trabalho visa conectar o banco de baterias ao barramento CC e ao mesmo tempo que faz a integração dos modos de carga e descarga em um único conversor. Adicionalmente, para reduzir volume, é utilizado um transformador planar que oferece alta eficiência (máximo de 99,5%) e uma reduzida relação volume/potência. O conversor foi desenvolvido para carregar um banco de baterias de 192V. No modo de descarga, ele é suado para alimentar um barramento CC de 400V com uma potência máxima de 1,34kW. Apesar do uso do conversor full-bridge não ser novidade nestes tipos de aplicação, dois fatores serviram de motivação para este trabalho: o uso do transformador planar e a tendência mundial de integração de fontes renováveis.
This work presents a study of the application of the Full-bridge bidirectional DC converter as a battery bank charger in a DC bus of renewable energy sources. The main problem is that these sources are seasonal and do not offer a continuously power supply. Thus, the use of a battery bank connected to a DC bus shared with other renewable sources brings contributions in the continuity of power supply. The converter proposed in this work aims to connect the battery bank to the DC bus at the same time it integrates the charging and discharging modes into a single converter. Additionally, to reduce the volume, it is used a planar transformer that provides high efficiency (up to 99.5%) and a reduced volume/power ratio. The converter is designed to charge a bank of batteries of 192V. At the discharge mode, it is designed to feed a 400V DC bus with maximum power of 1.34 kW. Despite the use of the full-bridge converter is not new in these types of application, two factors served as motivation for this work: the use of planar transformer and the global trend of integration of renewable sources.
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Gnoatto, Claudio Lucas. "Estratégias de controle repetitivo para aplicação em sistemas de alimentação ininterrupta de energia." Universidade Tecnológica Federal do Paraná, 2011. http://repositorio.utfpr.edu.br/jspui/handle/1/222.
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CAPESEste trabalho tem como objetivo a análise, projeto e implementação de estratégias de controle repetitivo para aplicação em sistemas de alimentação ininterrupta de energia (UPS - Uninterruptible Power Supply). Inicialmente, a revisão da literatura aborda os controladores mais aplicados neste propósito. Uma visão geral sobre sistemas UPS é realizada, com foco em diferentes topologias e o projeto de um filtro indutivo capacitivo (LC), para reduzir o conteúdo harmônico proveniente das comutações do inversor, é discutido. Na sequência, uma estratégia de controle é proposta. Nesta estratégia um termo feedforward é utilizado para gerar a forma de onda da tensão de saída e um controlador do tipo proporcional derivativo (PD) é inserido para compensar distúrbios não cíclicos. Para compensação de distúrbios cíclicos, algumas técnicas de controle repetitivo são analisadas e implementadas. A adição destes controladores apresenta bom desempenho, porém, quando o sistema sofre interferências, as características dinâmicas destes controladores são afetadas. Modificações são realizadas para tornar o sistema menos suscetível a ruídos de alta frequência e a distúrbios aperiódicos. Ainda, é proposto um controlador repetitivo com adaptação do ganho que apresenta robustez suficiente para boa regulação de tensão mesmo na presença de distúrbios aperiódicos e interferências eletromagnéticas. Por fim, é descrita a implementação de uma plataforma flexível, baseado em um inversor PWM controlado por um processador digital de sinais com periféricos para aquisição de dados e geração de PWM, DSC TMS320F28335. A partir desta plataforma, foram obtidos resultados experimentais para um protótipo de uma UPS monofásica, os quais comprovam o desempenho das técnicas de controle apresentadas e propostas.
This work presents an analysis, design and implementation of repetitive control strategies applied to uninterruptible power supplies (UPS) systems. At the beginning, a literature review of the main controllers concerning this purpose is shown. A global vision of UPS systems with focus on different topologies is made and the project of an inductive capacitive filter (LC) is presented where the goal is to reduce harmonic content due to the inverter switching. After that, a control strategy is presented. In this strategy a feed forward term is used to generate the wave form shape of the output voltage and a Proportional Derivative (PD) controller is introduced to compensate non cyclic disturbances. For the compensation of cyclic disturbs some repetitive control techniques are analyzed and implemented. The inclusion of these controllers provides a good performance for the output system, however, when the system is exposed to interferences, the dynamic characteristics of these controllers are affected. Modifications are presented to make the system less susceptible for high frequencies noise and aperiodic disturbs. In addition, a repetitive controller with gain adaptation is proposed with sufficient robustness to obtain a good voltage regulation even in the presence of aperiodic disturbances and electromagnetic interferences. Finally, the implementation of a flexible platform is presented, based on PWM inverter controlled by a digital signal processor with data acquisition and generation PWM peripherals, DSP TMS320F28335. From this platform, experimental results for a monophasic UPS prototype was obtained, which ones prove the performance of the control techniques presented and proposed.
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Lin, Jiann Wen, and 林建文. "Implementation of Uninterruptible Power Supply (UPS) with Fuzzy Control theory." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/72406060283127025716.
Full textAbstract:
碩士國立彰化師範大學
工業教育學系
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The purpose of this thesis is to apply fuzzy control for realization of uninterruptible power system (UPS). With the information industry prospering, personal computer and related equipment become more and more important. The UPS takes a vital role of guardian for the critical equipment. At present, the basic requirement of the UPS is to generate an AC output voltage of constant amplitude irrespective of load and supply conditions. The conventional approach uses a complex and expensive analog control circuit to achieve the above requirements. In this thesis, a control circuit with a microprocessor is implemented to obtain low cost and superior performance. It mainly consists of a minimized structure of power converter, which is capable of providing specified constant output voltage and pulse width modulation (PWM) battery charger. In order to improve the output characteristics of UPS, however, the fuzzy control theory is applied to atuomatic voltage regulation (AVR) control and the prediction of theUPS residual time. The steady-state operating principle of the UPS topology mentioned above and its new control strategy are illustrated. Finally, the experimental results of low-cost and high-performance small scale 300 VA UPS circuit with PWM battery charging are described and discussed.