Design and analysis of a system consisting of a variable-speed synchronous generator that supplies an active dc load (inverter) through a three-phase diode rectifier requires adequate modeling in both time and frequency domain. In particular, the system's control-loops, responsible for stability and proper impedance matching between generator and load, are difficult to design without an accurate small-signal model. A particularity of the described system is strong non-ideal operation of the diode rectifier, a consequence of the large value of generator's synchronous impedance. This non-ideal behavior influences both steady state and transient performance. This thesis presents a new, average model of the system. The average model accounts, in a detailed manner, for dynamics of generator and load, and for effects of the non-ideal operation of diode rectifier. The model is non-linear, but time continuous, and can be used for large- and small-signal analysis. The developed model was verified on a 150 kW generator set with inverter output, whose dc-link voltage control-loop design was successfully carried out based on the average model. / Master of Science

A general purpose computer model for the SCR is developed. The model, consisting of both a circuit analog and parameter estimation procedure, is uniformly applicable to popular computer aided design and analysis programs such as SPICE2 and SCEPTRE. The circuit analog is based on the intrinsic three PN junction structure of the SCR and is similar to Nienhus' model. The parameter estimation procedure requires only manufacturer's specification sheet quantities as a database. It employs some of the concepts developed by Hu for a SPICE2 SCR model. This uniform model, denoted the J³ SCR model, is shown to be a useful design aid through computer simulation of fault transients which may occur in a"Schwarz" converter. The transients simulated would not be observable without use of a highly accurate continuous topology non-linear SCR model such as is developed here. / Ph. D.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22658号 / 工博第4742号 / 新制||工||1741(附属図書館) / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 篠原 真毅, 教授 守倉 正博, 教授 小嶋 浩嗣 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Pulse width modulation (PWM) rectifiers are extensively used in battery charger, regulated dc voltage source, UPS systems, ac line conditioner and motor drives. The conventional control schemes for these rectifiers require PLL, transformations, and input voltage sensing, which increase the cost and complexity of the controller. Simple control schemes based on resistance emulation control are developed in this thesis work for different PWM boost rectifiers. Modeling, analysis and design methods for these rectifier systems are presented. The effect of computational delay involved in digital implementation on the performance of the above rectifier systems is studied. A single-switch boost rectifier system is presented, which operates in DCM and in CCM for an output power less than and greater than 50% rated load, respectively, exploiting the best features of both the operating modes. A generalized feedforward control is presented to improve the dynamic response of output voltage of single-phase boost rectifiers against input voltage, load current and reference voltage disturbances. Feedforward control requires additional voltage and/or current measurements. A state observer is presented for estimating the inductor current of a buck rectifier, and two disturbance observers are presented to estimate the input voltage and the load current of a boost rectifier. These observers eliminate the need of additional sensors for implementing the feedforward control. The resistance emulation control is extended to four-wire PWM rectifier. Two control methods are presented. The first method makes the input currents of the rectifier proportional to their respective input voltages, while the second one balances its input currents even under unbalanced input voltage condition. A detailed analysis of line and neutral current distortions of four-wire converter is presented. A three-carrier based PWM scheme is presented, which significantly reduces the neutral current of the rectifier compared to conventional PWM scheme, when three single-phase inductors are used, and considerably reduces both line and neutral current distortions, when a three-limb inductor is used. A regenerative test setup containing two back-to-back connected three-phase PWM converters is presented for testing high-power converters in the active and reactive power circulation mode. The proposed scheme considerably reduces the cost of testing, and hence, the overall production cost of the converters compared to load-bank testing. A mathematical model is presented for the above system. A suitable control method is presented to control the two converters of the back-to-back system. A new PWM scheme is presented, which considerably reduces the requirement of the dc bus voltage of the back-to-back system compared to conventional PWM schemes. All theoretical predictions are experimentally validated. The experimental results are presented.

Orientador: Falcondes Jose Mendes de Seixas / Banca: Dionizio Paschoareli Junior / Banca: Guilherme de Azevedo e Melo / Banca: Luiz Carlos Gomes de Freitas / Banca: Roger Gules / Resumo: Os conversores ou retificadores multipulsos se apresentam como uma técnica passiva para melhorar a qualidade de energia na rede elétrica. Eles proporcionam baixa Distorção Harmônica Total de corrente (DHTi), resultando um elevado Fator de Potência (FP) e baixa ondulação na tensão de saída. Neste contexto apresenta-se um abrangente levantamento bibliográfico, com o intuito de classificar as inúmeras topologias CA-CC trifásicas. As topologias retificadoras CA-CC estudadas nesta tese utilizam transformadores não-isolados, ou autotransformadores, cujas conexões são denominadas de Estrela e Delta-diferenciais, que resultam em retificadores multipulsos. Como atrativo essas topologias apresentam baixas taxas kVA (parcela de potência processada pelos núcleos), o que leva a reduzidos peso e volume. São estruturas confiáveis e robustas, apresentam baixa complexidade de construção e produzem pequena interferência eletromagnética. Outra grande vantagem destas estruturas é a possibilidade de obter qualquer valor de tensão de saída para qualquer nível de tensão de entrada. Como contribuição deste trabalho, análises matemáticas e fasoriais foram realizadas para cada uma das configurações com topologias Delta e Estrela, obtendo expressões generalizadas com relação ao número de pulsos do retificador para cada uma delas. A partir deste equacionamento foi possível obter expressões unificadas para duas das configurações de diferentes topologias (denominadas de A e C). A análise unificada foi realizada tanto para tensão como para corrente, resultando no equacionamento utilizado no desenvolvimento de uma nova ferramenta de simulação e projeto para os retificadores com essas duas configurações. A partir da análise matemática de cada configuração foi possível desenvolver uma nova metodologia... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Nowadays the theme of Power Quality has been one of the most discussed topics. Several techniques for power factor correction are presented in the literature. The multipulse converters or rectifiers resurge as a passive technique to improve the power quality in the mains. They provide low Total Harmonic Distortion of current (THDi), high Power Factor (PF) and low ripple on the output voltage. This thesis shows a comprehensive bibliographic research with the purpose of classifying the several AC-DC three-phase topologies that improve the power quality in the mains. The topologies studied in this thesis use non-isolated transformers and are called as generalized Wye and Delta-differential connections. These connections show an advantage of low kVA-rating (power processed by the core), reducing weight and volume of these rectifier structures. The multipulse rectifiers are reliable and robust, they show low complexity construction and low electromagnetic interference. Another advantage for these connections is the possibility to choose any value of the output voltage for any level of input voltage. Several configurations for Wye and Delta topologies are presented. One of the contributions of this thesis were the mathematical and fasorial analysis made for all configurations in order to obtain generalized expressions related to the pulse numbers for each configuration. From this equation was possible to obtain unified expressions for two configurations of different topologies (denominated A and C). The analysis was realized for voltage and current, result in an equation used in the development of a new simulation tool and designed for the rectifiers with this two configurations. Through the mathematical analysis it was possible to realize a study connecting the rectifier average output voltage and... (Complete abstract click electronic access below) / Doutor

L.D. Smullin and W.N. Coffey. / "November 12, 1948." / Bibliography: p. 14. / Army Signal Corps Contract No. W36-039-sc-32037 Project No. 102B. Dept. of the Army Project No. 3-99-10-022.

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 97-99). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Chicago, Department of Chemistry, 2002. / Includes bibliographical references. Also available on the Internet.

There is ever-increasing demand in telecommunication system, data server and computer equipment for low voltage, high current power supply. LLC resonant converter is a good topology on primary side of the converter because it has soft switching and resonant conversion. However, the passive rectifier in the secondary side has high power dissipation. Synchronous rectifier is a popular method to reduce this rectification loss. Although there are many types of synchronous rectifier for PWM converter, most of them do not function well in LLC resonant converters. It is because the wave form of LLC resonant converter is different from PWM. The objective of this research is to reduce the power dissipation and physical size at the same time. In this thesis, a novel current driven synchronous rectifier with saturable current transformer and dynamic gate voltage control for LLC resonant Converter is presented. This novel circuit reduces the rectification loss and size of the current transformer in the synchronous rectifier. This synchronous rectifier has several outstanding characteristics compared with generic voltage driven and current driven synchronous rectifier. The saturable feature reduces the current transformer turns. Inherent dynamic gate voltage controlled by saturable current transformer reduces gate loss in the MOSFET. A novel driving circuit is proposed for accurate turn off time. It reduces loss significantly. This synchronous rectifier is completely self-contained which can replace the rectifier diode as a drop in replacement. It is insensitive to parasitic inductance. In order to explain the current transformer saturable, a model of saturable current transformer is proposed. A prototype demonstrates the advantages of the proposed current driven synchronous rectifier. Furthermore, a novel integrated synchronous rectifier is presented which provides a more compact system. The synchronous rectifier current transformer is integrated with the main transformer which reduces the number of circuit joints in power path. Each soldering joint generates significance loss in power converter. A pair of 0.5mΩ soldering joint in 25A current path produces 0.62W loss. The placement of the integrated current transformer is important. A criterion for the placement of the current transformer within the main transformer is to avoid interference to the current transformer from the magnetic flux of the main transformer. Thus, a placement method to integrate the current transformer into the main transformer is proposed. An integrated current transformer model is suggested to explain the operation of the integrated synchronous rectifier. A prototype demonstrates the advantages of the integrated synchronous rectifier. / published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

Η παρούσα διπλωματική εργασία πραγματεύεται τη μελέτη και κατασκευή μονοφασικών ανορθωτικών διατάξεων για εργαστηριακούς σκοπούς. Η εργασία αυτή εκπονήθηκε στο Εργαστήριο Ηλεκτρομηχανικής Μετατροπής Ενέργειας του Τμήματος Ηλεκτρολόγων Μηχανικών και Τεχνολογίας Υπολογιστών της Πολυτεχνικής Σχολής του Πανεπιστημίου Πατρών. Σκοπός είναι η κατασκευή των τριών ελεγχόμενων μονοφασικών ανορθωτών με θυρίστορ, δηλαδή του ανορθωτή ενός παλμού, του ανορθωτή δύο παλμών με μετασχηματιστή μεσαίας λήψης και της ανορθωτικής γέφυρας με τέσσερα θυρίστορ. Απώτερος στόχος είναι η πραγματοποίηση μετρήσεων τάσης και ρεύματος σε διάφορα σημεία των διατάξεων καθώς και η επικοινωνία της κατασκευής με ηλεκτρονικό υπολογιστή μέσω του οποίου θα πραγματοποιείται ο έλεγχος των διατάξεων και θα προβάλλονται οι μετρήσεις, ώστε να χρησιμοποιηθεί η διάταξη για εργαστηριακούς σκοπούς. Αρχικά εξετάζεται η δυνατότητα που υπάρχει να υλοποιηθούν και οι τρείς μονοφασικές ανορθωτικές διατάξεις με χρήση τεσσάρων μόνο θυρίστορ και ενός γενικού κυκλώματος ισχύος αντί να κατασκευαστούν τρείς ξεχωριστοί μετατροπείς. Για τον σκοπό αυτό μπορούν να χρησιμοποιηθούν ρελέ τα οποία μεταβάλλουν την τοπολογία του κυκλώματος ισχύος ανάλογα με το ποιά ανορθωτική διάταξη είναι επιθυμητό να υλοποιείται κάθε φορά. Στη συνέχεια εξετάζονται θέματα που αφορούν την επικοινωνία της διάταξης με το χρήστη και με τον ηλεκτρονικό υπολογιστή, με σκοπό την επιλογή του τρόπου λειτουργίας της καθώς και της γωνίας έναυσης των μετατροπέων, την παλμοδότηση των θυρίστορ, τον έλεγχο των ρελέ του κυκλώματος ισχύος και την τροφοδοσία των τυλιγμάτων τους, καθώς και τη χρήση μετρητικών στοιχείων τάσης και ρεύματος για την πραγματοποίηση ηλεκτρικών μετρήσεων στο κύκλωμα ισχύος. Για τη διεκπεραίωση των περισσοτέρων από αυτές τις λειτουργίες, κυρίαρχο ρόλο έχει ο μικροελεγκτής DSPIC30F4011. Το επόμενο βήμα είναι η δημιουργία ενός εικονικού οργάνου (VI) στην εφαρμογή LabVIEW μέσω του οποίου πραγματοποιείται ο έλεγχος της κατασκευής μέσω ηλεκτρονικού υπολογιστή και προβάλλονται οι μετρήσεις που προέρχονται από τα μετρητικά στοιχεία του κυκλώματος ισχύος. Τέλος, κατασκευάζονται οι διατάξεις στο εργαστήριο και στη συνέχεια πραγματοποιούνται μετρήσεις με σκοπό την επιβεβαίωση και την αξιολόγηση της λειτουργίας της κατασκευής. / This thesis deals with the design and construction of single-phase rectifier devices for laboratory purposes . The work was conducted in Electromechanical Energy Conversion Laboratory , Department of Electrical and Computer Engineering of the University of Patras . The aim is the construction of the three single phase controlled thyristor rectifiers, the one pulse rectifier , the two pulses rectifier with split-winding transformer and the four thyristors bridge rectifier. The uppermost goal is to perform measurements of voltage and current at various points of the power circuit and to carry out construction-computer communication through which the construction can be controlled and electrical measurements can be viewed.