Στις μέρες μας οι συνεχώς αυξανόμενες ενεργειακές ανάγκες, καθώς και η απαίτηση των κοινωνιών για ένα πιο καθαρό περιβάλλον, έχουν κάνει τις ανανεώσιμες πηγές ενέργειας όλο και πιο ελκυστικές ως προς την εκμετάλλευση τους. Η αξιοποίηση της αιολικής ενέργειας στην παραγωγή ηλεκτρικής ενέργειας κερδίζει όλο και περισσότερο έδαφος. Η τεχνολογία των αιολικών συστημάτων αναπτύσσεται συνεχώς ,με αποτέλεσμα να υπάρχουν διάφορες κατηγορίες αυτών, ανάλογα με τη χρήση για την οποία προορίζονται. Στην παρούσα διπλωματική μου εργασία, μελετάται ένα αιολικό σύστημα μεταβλητών στροφών που χρησιμοποιεί μία παραλλαγή της επαγωγικής μηχανής Διπλής Τροφοδοσίας. Η διαφοροποίηση του έγκειται στον επιπλέον dc/ac μετατροπέα που χρησιμοποιείται, προκειμένου να ελέγξουμε την τάση που μπορεί να δει ο στάτης. Μ΄ αυτό τον τρόπο, το αιολικό σύστημα μιας γεννήτριας διπλής τροφοδοσίας γίνεται ακόμα πιο αξιόπιστο, συνεχίζοντας την παραγωγή ισχύος και παραμένοντας συνδεδεμένο με το δίκτυο σε περίπτωση σφάλματος στην πλευρά του δικτύου. Στη μελέτη αυτή, αφού εξαγάγαμε το μαθηματικό μοντέλο του συστήματος και το προσομοιώσαμε σε περιβάλλον Matlab - Simulink, δοκιμάσαμε το σύστημα σε συνθήκες ύπαρξης σφάλματος στο δίκτυο. Στο σύστημα εφαρμόστηκαν κλασικές τεχνικές ελέγχου,με στόχο τη διατήρηση της μέγιστης απομάστευσης ισχύος από το σύστημα, την αύξηση της αντοχής του σε σφάλματα από την πλευρά του δικτύου, καθώς και τη μη αποσύνδεση του συστήματος από το δίκτυο σε μία τέτοια περίπτωση. Τέλος, συγκρίναμε τη συμπεριφορά αυτού του συστήματος με τη συμπεριφορά ενός κλασικού αιολικού συστήματος με επαγωγική γεννήτρια Διπλής Τροφοδοσίας και παραθέσαμε τις διαφορές. / The increasingly energy demands in our days and also the modern societies demand for a greener environment, have made the electrical energy production from renewable energy sources more attractive. The use of wind energy in the electrical energy production is having more and more fervent supporters. The technology and the types of the wind systems varies, depending on the use and the environmental conditions. In my diploma thesis I designed, we will study a variation of a wind system with a variable speed operation with a Doubly Fed Induction Generator. In this system we also use a dc/ac converter in order to control the voltage which the stator can “see”. Using this converter the wind system with a DFIG is more reliable and remains connected to the ac grid, maintaining the maximum power production, in case of a fault on grid side. In this thesis, after we made the mathematical model with a great accuracy and simulated using Matlab - Simulink, we tested it under conditions of different voltage sags from the side of the grid. In order to control the system and maintaining the power production power at the maximum level, we used classic control methods, and as a result, we achieved to keep the maximum level of power production and to keep the wind system connected to the grid in a scenario of a grid side fault. Finally, we compared the behavior of the system we designed with the wind system with the classic DFIG and we presented the differences.

A new concept, the multi level voltage/current reinjection ac/dc conversion, is described in this thesis. Novel voltage and current source converter configurations, based on voltage and current reinjection concepts are proposed. These converter configurations are thoroughly analyzed in their ac and dc system sides. The fundamentals of the reinjection concept is discussed briefly, which lead to the derivation of the ideal reinjection waveform for complete harmonic cancellation and approximations for practical implementation. The concept of multi level voltage reinjection VSC is demonstrated through two types of configurations, based on standard 12-pulse parallel and series connected VSC modified with reinjection bridges and transformers. Firing control strategies and steady state waveform analysis are presented and verified by EMTDC simulations. The multi level current reinjection CSC is also described using two configurations based on standard 12-pulse parallel and series connected CSC modified with associated reinjection circuitry. Firing control strategies and steady state waveform analysis are presented and verified by EMTDC simulations. Taking the advantage of zero current switching in the main bridge valves, achieved through multi level current reinjection, an advanced multi level current reinjection scheme, consisting thyristor main bridges and self-commutated reinjection circuitry is proposed. This hybrid scheme effectively incorporates self-commutated capability into a conventional thyristor converter. The ability of the main bridge valves to commutate without the assistance of a turn-off pulse or line commutating voltage under the zero current condition is explained and verified by EMTDC simulations. Finally, the applications of the MLCR-CSC are discussed in terms of a back to back HVDC link and a long distance HVDC transmission system. The power and control structures and closed loop control strategies are presented. Dynamic simulation is carried out on PSCAD/EMTDC to demonstrate the two systems ability to respond to varying active and reactive power operating conditions.

In this dissertation, two high-frequency (HF) transformer isolated single-stage integrated ac-dc converters are proposed for a small scale permanent magnet synchronous generator (PMSG) based wind energy conversion system (WECS). These two types of single-stage integrated ac-dc converters include expected functions of HF isolation, power factor correction (PFC), and output regulation in one single-stage. Fixed-frequency phase-shift control and soft-switching operation are employed in both proposed ac-dc converters. After reviewing the literature and discussing pros and cons of the existing topologies, it is preferred that three identical single-phase single-stage integrated converters with interleaved connection configuration are suitable for the PMSG. For the single-phase converter, two new HF isolated single-stage integrated resonant ac-dc converters with fixed-frequency phase-shift control are proposed. The first proposed circuit is HF isolated single-stage integrated secondary-side controlled ac-dc converter. The other proposed circuit is HF isolated single-stage dual-tank LCL-type series resonant ac-dc converter, which brings better solutions compared to the first converter, such as high power factor and low total harmonic distortion (THD) at the ac input side. Approximate analysis approach and Fourier series methods are used to analyze these two proposed converters. Design examples for each one are given and designed converters are simulated using PSIM simulation package. Two experimental circuits are also built to verify the analysis and simulation. The simulated and experimental results reasonably match the theoretical analysis. Then the proposed HF isolated dual-tank LCL-type series resonant ac-dc converter is used for three-phase interleaved connection in order to satisfy requirements of PMSG based WECS. A design example for this three-phase interleaved configuration is given and simulated for validation under several operating conditions. / Graduate / 0544 / duyimian@uvic.ca

Σκοπός της παρούσας εργασίας ήταν να γίνει μια εκτενής καταγραφή και παρουσίαση των ηλεκτρονικών μετατροπέων που χρησιμοποιούνται για τη διασύνδεση των Ανανεώσιμων Πηγών Ενέργειας (Α.Π.Ε) στο δίκτυο. Αφού γίνεται αρχικά μια αναφορά στις Α.Π.Ε και στα Ηλεκτρονικά Ισχύος, στη συνέχεια παρουσιάζονται οι διαφορετικές τοπολογίες των ηλεκτρονικών μετατροπέων που μπορούν να χρησιμοποιηθούν σε κάθε εφαρμογή. Για τους μετατροπείς, εξηγείται πρώτα η λειτουργία τους και στη συνέχεια αναφέρονται τα πλεονεκτήματα και μειονεκτήματα της κάθε τοπολογίας προκειμένου να παρέχεται στον αναγνώστη η δυνατότητα γρήγορης, εύκολης και άμεσης σύγκρισης. Επίσης, παρουσιάζονται κατάλληλα συστήματα για την αποθήκευση της ενέργειας προερχόμενη από Α.Π.Ε. Τέλος, προσομοιώνεται το ίδιο φωτοβολταϊκό σύστημα χρησιμοποιώντας τρεις διαφορετικούς μετατροπείς, διαφορετικής τοπολογίας ο κάθε ένας, προκειμένου να συγκριθούν και να αναλυθούν τα αποτελέσματα με βάση τη θεωρητική ανάλυση που έχει προηγηθεί. / The aim of this dissertation was to present the power-electronic systems for the grid integration of renewable energy sources. Once both the renewable energy sources and the power electronics are discussed, different topologies of power converters that can be used in such systems are presented. Converters’ operation is firstly explained, followed by a list of advantages and disadvantages of them so as the reader can make an easy, fast and direct comparison. Storage systems appropriate for renewable energy sources systems are also shown. At the end, a simulation of a photovoltaic system with three different kinds of inverter is performed in order to compare and analyze the results based on the theoretical analysis previously presented.

Este trabalho aborda a detecção da condição de ilhamento e de seus impactos em redes de distribuição e em gerações distribuídas que empregam conversores CC-CA. Na literatura são encontradas dois grupos de técnicas para este tipo de aplicação. As técnicas passivas, que identificam a condição de ilhamento através do ajuste dos limites de variação dos relés de proteção, e as técnicas ativas, que inserem um sinal de realimentação positiva de forma a tornar o sistema instável no momento da desconexão. As técnicas ativas, por apresentarem um menor tempo de detecção e simples implementação em hardware, são preferencialmente utilizadas, apesar da injeção de distúrbios no sistema de controle da geração distribuída. O estado-da-arte em termos de detecção de ilhamento consiste em desenvolver uma técnica que possua alta capacidade de detecção, porém sem injeção de distúrbios no sistema de geração distribuída quando conectado à rede de distribuição. Neste trabalho, são abordadas duas formas para a redução da injeção de distúrbios e do tempo de detecção. Em uma primeira abordagem é proposto um projeto ótimo para o algoritmo de sincronização PLL (phase-locked loop), o qual permite a redução do ganho de realimentação positiva para técnicas em frequência e, consequentemente, a redução da injeção de distúrbios. Em uma segunda abordagem é utilizada a metodologia fuzzy de forma a garantir a detecção da condição de ilhamento sem nenhuma injeção de distúrbios no sistema de controle. Resultados de simulação e experimentais, obtidos por meio de uma bancada experimental controlada por DSP, são apresentados para validar as propostas presentes nesta dissertação / This thesis deals with the islanding detection and its impact on distribution networks when distributed generation systems are driven by DC-AC converters. Two groups of techniques are found in the literature. The passive techniques in which adjusting the variation limits of protective relays identify the islanding condition, and the active techniques that insert a positive feedback signal in order to make the system unstable when the contingency is on progress. The active techniques present a reduced detection time and simple hardware implementation. They are preferably used in despite of the injection of disturbances in the control system. In this thesis two ways to reduce injection of disturbances and detection time are proposed. In a first approach is shown an optimal design for the synchronization algorithm PLL (Phase-Locked Loop) which allows to reduce the positive feedback gain in frequency techniques in order to decrease the injection of disturbances. In a second approach a fuzzy methodology is used to ensure the islanding detection with the aforementioned requirements. Simulation analysis and experimental results are presented to validate the proposed approach

Made available in DSpace on 2014-06-11T19:22:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-12-03Bitstream added on 2014-06-13T20:29:04Z : No. of bitstreams: 1 fernandes_rc_me_ilha.pdf: 1607084 bytes, checksum: d60bd1d35a36564730a6c9f6b43790ab (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho propõe um novo conversor CA-CC trifásico de múltiplos pulsos com estágios CC-CC elevadores de tensão controlados pela técnica de histerese constante. Nesta proposta não são empregados indutores de interfase. A finalidade deste conversor é a de possibilitar um barramento CC regulado para aplicações embarcadas, acionamentos elétricos e afins, sempre com preocupações relacionadas aos aspectos de Qualidade de Energia Elétrica. Assim, a proposta deve apresentar elevado fator de potência, baixa distorção harmônica total de corrente drenada da rede elétrica. Ampla revisão bibliográfica, reunindo as propostas mais recentes da literatura para conversores com mesma finalidade, é feita para que sejam estudadas as estruturas de potência, técnicas de controle, versatilidade, possibilidade de isolamento galvânico e robustez. Em seguida, é detalhada a proposta principal deste trabalho por meio da apresentação do equacionamento do autotransformador, dos estágios elevadores de tensão e da técnica de controle. Esta análise permite que sejam feitas simulações com todos os elementos do conversor CA-CC e então, se desenvolva o projeto físico dos elementos magnéticos e se escolham os componentes eletrônicos do protótipo. O número reduzido de componentes de controle e a simplicidade dos circuitos de potência são grandes atrativos da proposta discutida. Todas as informações relevantes são descritas detalhadamente e, sempre que possível, meios alternativos de solucionar problemas são também apresentados, de forma que fiquem claras as possibilidades de melhoria da técnica empregada. A operação conjunta de todos os elementos mais a técnica de controle foi validada, de maneira que se comprovou, por meio de ensaios, todos os princípios de funcionamento da proposta de conversor CA-CC. Pelos resultados experimentais, obteve-se corrente drenada... / This work proposes a new AC-DC three-phase multipulse converter with DC-DC boost stages and constant hysteresis control. The objective of this converter is to provide a reliable DC bus for on-board applications, electric motor drives and similars, always considering power quality issues. Thus, the proposal presents high power factor and low harmonic distortions in the currents from the mains. A wide revision is made on other recent proposals found in the scientific literature. Different topologies are compared considering power circuits, control techniques, isolation possibility and robustness. The second chapter presents the details on the main proposal of this work and also the mathematical equations that describe the autotransformer, boost converters and control strategy. Later, simulation results are commented and discussed and the physical design is detailed. The output filter elements, power components and control elements are specified. Experimental results including main waveforms, efficiency, voltage regulation and temperature rise are presented for the autotransformer. The boost stages are also tested and its results are discussed. Finally, the proposed AC-DC converter is tested and the control technique applied to the power stage is validated

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work presents the research and development of a connection method for static converters, called Optimized Cascade, which aims to reduce the redundant power processing in multiple stage topologies for LED driving. An initial analysis of possible solutions available on the literature is conducted, where different kinds of solutions are demonstrated, their characteristics and how they can be classified. Afterward, an analysis of the general characteristics of the optimized cascade is presented, as well as the method employed to reduce the bus capacitance value. This reduction aims to replace the electrolytic capacitor for alternative technologies, in order to increase the lifespan of the LED driver. One of the inovations of this work is the proposal of a project methodology, focusing the conversion efficiency and the capacitance reduction. Besides that, a mathematical model of the optimized cascade was derived, so as to establish the impact of the bus voltage ripple on the LED current. From this model, it has been possible to determine parameters for choosing the best operating mode for the second stage and the estimation of capacitance reduction-. Also, some controllers were analyzed to control the PC stage, on which the resonant controller has been proposed for demanding projects, regarding the capacitance value and LED current ripple. Finally, two prototypes were mounted and tested, where an efficiency of thereabout 90% was get with a power factor of 0; 99, along with total compliance with the power quality parameters and flicker. In both prototypes film capacitors were employed, contributing to enhance the lifespan of the converter, making it compatible with LED lifespan. / Este trabalho apresenta o estudo e desenvolvimento de um método de conexão de conversores, chamado Cascata Otimizada, o qual visa reduzir o processamento redundante de energia em topologias de múltiplos estágios para acionamento de LEDs. Uma análise preliminar das soluções disponíveis atualmente na literatura acadêmica é realizada, na qual são demonstrados diferentes tipos de soluções, suas características e como podem ser classificadas. Em seguida, uma análise das características gerais da cascata otimizada é apresentada, bem como o método empregado para redução da capacitância de barramento. Tal redução visa a substituição de capacitores eletrolíticos por tecnologias alternativas, com o intuito do aumento da vida útil do driver. Uma das inovações deste trabalho é a proposição uma metodologia de projeto, com foco na eficiência e na redução da capacitância. Além disso, também foi elaborado um modelo matemático, de forma a determinar o impacto da ondulação da tensão no barramento sobre a corrente nos LEDs. A partir desse modelo, foi possível estabelecer parâmetros para a escolha do melhor modo de operação para o segundo estágio e estimação da redução do capacitor de barramento. Também foram analisados diversos controladores para o segundo estágio, sendo proposto o uso do controle ressonante para projetos mais exigentes com respeito ao valor do capacitor de barramento e da ondulação na corrente de saída. Por fim, dois protótipos foram montados e testados, obtendo uma eficiência de aproximadamente 90%, fator de potência de 0;99 e total observância aos parâmetros de qualidade de energia e flicker. Em ambos os protótipos foram empregados capacitores de filme, o que contribui para elevar a vida útil do conversor, compatibilizando-a com a vida útil da carga LED.

nÃo hà / Esta tese de doutorado apresenta duas novas topologias de conversores CA-CC com uso de neutro comum: conversor de cinco nÃveis intercalado e conversor de cinco nÃveis tipo T. AlÃm disso, uma nova forma de implementaÃÃo da tÃcnica de controle indireto da corrente (Indirect Current Control - ICC) à apresentada. Assim, para comprovaÃÃo da praticidade dos conversores apresentados, toma-se como base o conversor CA-CC de trÃs nÃveis convencional e entÃo à realizada uma anÃlise comparativa de desempenho entre esses trÃs conversores CA-CC monofÃsicos para aplicaÃÃo em no-breaks. Os conversores analisados possuem como caracterÃstica comum a correÃÃo do fator de potÃncia, o controle digital realizado por FPGA e a conexÃo da fonte de alimentaÃÃo com o estÃgio de saÃda, facilitando o uso de inversor e by-pass para no-breaks. O primeiro conversor analisado à o conversor de trÃs nÃveis convencional que apresenta como principal caracterÃstica o reduzido nÃmero de componentes. O segundo conversor analisado à o conversor de cinco nÃveis intercalado que apresenta como principal caracterÃstica as reduzidas perdas de comutaÃÃo e conduÃÃo. Finalmente, o terceiro conversor analisado à o conversor de cinco nÃveis tipo T que apresenta como principais caracterÃsticas: reduzidas perdas de comutaÃÃo e conduÃÃo; os elementos magnÃticos operam com o dobro da frequÃncia de comutaÃÃo reduzindo desta maneira o peso e o volume. A anÃlise teÃrica dos conversores monofÃsicos, os conceitos bÃsicos sobre o controle digital e a tÃcnica de modulaÃÃo, a metodologia de projeto, simulaÃÃo e resultados experimentais dos protÃtipos construÃdos sÃo apresentados para validar o princÃpio de funcionamento dos conversores propostos. / This thesis presents two novel topologies of AC-DC converters with common neutral: five-level interleaved converter and five-level T type converter. Besides, a novel type of implementation of Indirect Current Control (ICC) is also presented. Thus, a comparative analysis of performance between three single phase AC-DC converters for UPS applications is realized. The analyzed converters have as common characteristics: power factor correction, digital control using FPGA and connection between input power supply and converter output enabling the use of UPS inverter and by-pass. The first one analyzed converter is the conventional three level converter which presents as main feature reduced numbers of power semiconductors and components. The second one analyzed converter is the five level interleaving converter which presents as main feature reduced conduction and commutation losses. Finally, the last one analyzed converter is the T type five level converter which presents as main features: reduced conduction and commutation losses and magnetic components operating with the double of switching frequency reducing weight and volume. Theoretical analysis of the single phase converters, basics concepts of digital control and modulation technique, design procedure, simulation and experimental results of lab models are presented in order to validate the principle of operation of the proposed converters.

fator de potÃncia e recurso para operar com dois valores de tensÃo de entrada. O mesmo à aplicÃvel a sistemas ininterruptos de energia do tipo dupla conversÃo ou on-line com caracterÃsticas de tensÃo de entrada bivolt (110 Vca e 220 Vca) e desta maneira à descartada a utilizaÃÃo de um autotransformador com seletor de tensÃo. O conversor em estudo à composto por dois conversores CA-CC boost clÃssicos, em que, para uma tensÃo de entrada de 110 Vca as entradas sÃo conectadas em paralelo e para uma tensÃo de entrada de 220 Vca as entradas sÃo conectadas em sÃrie. A ideia à fazer com que se tenha uma divisÃo equilibrada na entrada de cada conversor quando a tensÃo da rede elÃtrica for 220 Vca. Assim cada conversor boost clÃssico recebe metade da tensÃo total de alimentaÃÃo do conversor proposto. A estratÃgia de controle à baseada no controle por modo corrente mÃdia aplicada a ambos os conversores para proporcionar a correÃÃo do fator de potÃncia e a regulaÃÃo da tensÃo de saÃda. Para verificar o estudo teÃrico foi desenvolvido o projeto do circuito de potÃncia e controle validando atravÃs de resultados de simulaÃÃo e experimentais para um protÃtipo de 2,4 kW. Para a conexÃo paralelo e sÃrie das entradas, os resultados obtidos foram satisfatÃrios e o conversor operou adequadamente. / This work presents a study of a Double Boost AC-DC Converter with power factor correction and dual input voltage operation capability via a selector switch. Such converter can be applied to on-line uninterruptible power supplies with dual voltage input characteristics, this way avoiding the usage of a low frequency autotransformer. The studied structure is composed by two AC-DC classical boost converters, in which for input voltage of 110 Vac both its inputs are connected in parallel, and, for 220 Vac, they are connected in series. The control strategy is based in the average current mode control applied to both converters, in order to provide the power factor correction and output voltage regulation. Simulation and experimental results for 2.4 kW are presented, and so are validate the theoretical study and design. Connecting the inputs in parallel and series, the results were satisfactory and the converter operated properly.

Modern power networks incorporate communications and information technology infrastructure into the electrical power system to create a smart grid in terms of control and operation. The smart grid enables real-time communication and control between consumers and utility companies allowing suppliers to optimize energy usage based on price preference and system technical issues. The smart grid design aims to provide overall power system monitoring, create protection and control strategies to maintain system performance, stability and security. This dissertation contributed to the development of a unique and novel smart grid test-bed laboratory with integrated monitoring, protection and control systems. This test-bed was used as a platform to test the smart grid operational ideas developed here. The implementation of this system in the real-time software creates an environment for studying, implementing and verifying novel control and protection schemes developed in this dissertation. Phasor measurement techniques were developed using the available Data Acquisition (DAQ) devices in order to monitor all points in the power system in real time. This provides a practical view of system parameter changes, system abnormal conditions and its stability and security information system. These developments provide valuable measurements for technical power system operators in the energy control centers. Phasor Measurement technology is an excellent solution for improving system planning, operation and energy trading in addition to enabling advanced applications in Wide Area Monitoring, Protection and Control (WAMPAC). Moreover, a virtual protection system was developed and implemented in the smart grid laboratory with integrated functionality for wide area applications. Experiments and procedures were developed in the system in order to detect the system abnormal conditions and apply proper remedies to heal the system. A design for DC microgrid was developed to integrate it to the AC system with appropriate control capability. This system represents realistic hybrid AC/DC microgrids connectivity to the AC side to study the use of such architecture in system operation to help remedy system abnormal conditions. In addition, this dissertation explored the challenges and feasibility of the implementation of real-time system analysis features in order to monitor the system security and stability measures. These indices are measured experimentally during the operation of the developed hybrid AC/DC microgrids. Furthermore, a real-time optimal power flow system was implemented to optimally manage the power sharing between AC generators and DC side resources. A study relating to real-time energy management algorithm in hybrid microgrids was performed to evaluate the effects of using energy storage resources and their use in mitigating heavy load impacts on system stability and operational security.