Dissertations / Theses on the topic 'Switched Mode Converters'

Switched-mode power converters are some of the most widely used power electronics circuits due to their advantages of high conversion efficiency, flexible output voltage, light weight. A variety of control methods have been developed for the switched-mode power converters. However, in many practical situation, additional constraints need to be considered, e.g., safety measurement, current limiting or soft-starting, gross changes of operation point with guaranteed system stability, which has not been fully addressed in the available research works. On the other hand, the majority of the control design for power converters are based on the state-space averaged approach which involves considerable approximation in analysis and synthesis. Hence, advanced control techniques are in demand, which should be more constraints friendly and based on more precise models. In this thesis, much attention has been spent on designing controllers for both DC-DC converters and DC-AC inverters based on hybrid modelling and Lyapunov stability theory. Due to the existence of the power switches, switched-mode power converters are hybrid systems with both continuous dynamics and discrete transition events. Instead of linearizing the converter model around a specific operating point, hybrid modelling captures both dynamics, which results in more accurate models. Firstly, a novel sampled-data control approach is proposed for DC-DC converters. DC-DC converters are modeled as sampled-data switched affine systems according to the status of the power switch. In order to avoid the delay of the switching signal, an on-line prediction method is adopted to estimate the system state at the next switching instant. Based on the switched affine model and the predicted system state, a novel switching control algorithm is synthesized by using the switched Lyapunov theory. The proposed approach is able to not only drive the output to a prescribed set point from any initial condition, but also track a varying reference signal, and the switching frequency can be adjusted online with guaranteed stability. In addition, with this approach, Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM) operations can be treated in a unified way. Experimental verification has been carried out to test the effectiveness and merits of the proposed method. Furthermore, to compensate the information loss due to limited access to the state, a multiple sampling scheme is employed to derive a discrete-time switched affine model with an augmented measurement output for DC-DC converters. Based on the model, an output-feedback switching control law, which drives the system state to a set of attainable switched equilibria, is synthesized by using a quadratic state-space partition. The multiple sampling scheme not only facilitates the controller synthesis, but also improves the energy efficiency of the converter by allowing a lower switching frequency. In addition, hybrid modelling techniques have been extended to more complicated cases – DC-AC inverters as the increasing number of power switches and the time-variant nature of the references. A current controller based on the hybrid model of the three-phase two-level inverter has been developed, which can drive the inverter currents tracking the desired power references in realtime and keep a unity power factor at the same time. This method has been extended to three-phase NPC inverters later on. However, in order to solve the neutral point balancing issue, a capacitor voltages prediction algorithm, modified from model predictive control, has been adopted. It should also be mentioned that a novel hybrid model for a grid-connected single-phase NPC inverter also has been presented, which models not only the dynamic of the inverter but also the dynamic of the current reference. An experimental test platform including a three-phase NPC inverter and a FPGA control board has been designed to demonstrate the implementation of the proposed control scheme in practice.

This thesis details novel control schemes and design techniques with the aim of improving the performance of several switched-mode power converter topologies. These improvements include higher steady-state and transient efficiencies for hard-switching converters and the automatic current limiting provision for LLC resonant converters. The thesis initially attempts to use linear closed-loop controllers to improve the transient response of synchronous buck converters, enabling them to be designed with a lower open-loop bandwidth so that the system can achieve higher efficiency. Three types of controllers were investigated viz: the PID, the state-feedback and the predictive controller. All three controllers exhibit similar step responses, which are the maximum transient responses achievable by the linear controllers with the given requirements. The thesis then examines the parallel converter (i.e. a converter with two parallel connected power modules (PMs)) in detail with a view to improve the efficiency and to minimise the current ripple experienced by the output capacitor. Two control schemes and a design technique for the parallel converter are proposed, to simultaneously improve its efficiency and power density. The parallel converter in this research consists of two non-identical rated PMs (termed main PM and auxiliary PM), with the transient response requirement allocated to the auxiliary PM, thereby allowing the main PM to operate at a lower frequency for higher steady-state efficiency. The first control scheme activates the auxiliary PM only when a pre-determined deviation in load/output voltage is exceeded under a load step. Thus, eliminating the losses contributed by the low efficiency auxiliary PM for small load step changes. The second control scheme shapes the auxiliary PM inductor current to be equal and opposite to the main PM current ripple, which when combined reduce the current ripple as experienced by the output filter capacitor, thereby allowing a lower value (and hence physically smaller) capacitor to be selected for higher power density. In order to improve the converter's steady-state efficiency further, the minimum load condition is allocated to the auxiliary PM in the new design technique. These allow both the main PM inductance and its switching frequency to be lower for higher efficiency. In recent years, the LLC has received much attention owing to its favourable operating characteristics including high efficiency and high power density. Usually one chooses to operate at or very close to the load independent point (LIP) since very little control effort is required to regulate the converter's output voltage in response to changes in the load. However under fault conditions where the load tends towards a short circuit, excessive currents can flow and thus control action need to be taken to protect both the converter and the load. The final topic of the thesis hence studies the characteristics of an LLC resonant converter with current-limiting capacitor-diode clamp and develops a new equivalent circuit model to predict the behaviour under overload conditions. A detailed analysis of the converter is presented using the proposed model, from which a design methodology is derived allowing the optimum circuit components to be selected to achieve the required current limiting/protection characteristics.

In recent years, high brightness light emitting diodes (HBLEDs) have increasingly attracted the interest of both industrial manufacturers and academic research community. Among the several aspects that make LED technology so attractive, the most appreciated characteristics are related to their robustness, high efficiency, small size, easy dimming capability, long lifetime, very short switch-on/switch-off times and mercury free manufacturing. Even if all such qualities would seem to give to solid state lighting a clear advantage over all the other kinds of competing technologies, the issues deriving from the need of LED technology improvement, on one hand, and of the development of suitable electronic ballasts to properly drive such solid state light sources, on the other, have so far hindered the expected practical applications. The latter problem, in particular, is nowadays considered the main bottleneck in view of a widespread diffusion of solid state technology in the general lighting market, as a suitable replacement of the still dominant solutions, namely halogen and fluorescent lamps. In fact, if it is true that some aspects of the devices’ technology (e.g. temperature dependent performance, light quality, efficiency droop, high price per lumen, etc…) still need further improvements, it is now generally recognized that one of the key requirements, for a large scale spread of solid state lighting, is the optimization of the driver. In particular, the most important specifications for a LED lamp ballast are: high reliability and efficiency, high power factor, output current regulation, dimming capability, low cost and volume minimization (especially in domestic general lighting applications). From this standpoint, the main goal is, therefore, to find out simple switched mode power converter topologies, characterized by reduced component count and low current/voltage stresses, that avoid the use of short lifetime devices like electrolytic capacitors. Moreover, if compactness is a major issue, also soft switching capability becomes mandatory, in order to enable volume minimization of the reactive components by increasing the switching frequency in the range of the hundreds of kHz without significantly affecting converter’s efficiency. It is worth mentioning that, in order to optimize HBLED operation, also other matters, like the lamp thermal management concern, should be properly addressed in order to minimize the stress suffered by the light emitting devices and, consequently, the deterioration of the light quality and of the expected lamp lifetime. However, being this work focused on the issues related to the research of innovative driving solutions, the aforementioned thermal management problems, as also all the topics related to the improvement of solid state devices’ technology, will be left aside. The main goal of the work presented in this thesis is, indeed, to find out, analyze and optimize new suitable topologies, capable of matching the previously described specifications and also of successfully facing the many challenges dictated by the future of general lighting. First of all, a general overview of solid state lighting features, of the state of the art of lighting market and of the main LED driving issues will be provided. After this first introduction, the offline driving concern will be extensively discussed and different ways of approaching the problem, depending on the specific application considered, will be described. The first kind of approach investigated is based on the use of a simple structure relying on a single power conversion stage, capable of concurrently ensuring: compliance with the standards limiting the input current harmonics, regulation of the load current and also galvanic isolation. The constraints deriving from the need to fulfil the EN 61000-3-2 harmonics standard requirements, when using such kind of solution for low power (<15W) LED driving purposes, will be extensively discussed. A low cost, low component count, high switching frequency converter, based on the asymmetrical half bridge flyback topology, has been studied, developed and optimized. The simplicity and high compactness, characterizing this solution, make it a very good option for CFL and bulb replacement applications, in which volume minimization is mandatory in order to reach the goal of placing the whole driving circuitry in the standard E27 sockets. The analysis performed will be presented, together with the design procedure, the simulation outcomes and the different control and optimization techniques that were studied, implemented and tested on the converter's laboratory prototype. Another interesting approach, that will be considered, is based on the use of integrated topologies in which two different power conversion stages are merged by sharing the same power switch and control circuitry. In the resulting converter, power factor correction and LED current regulation are thus performed by two combined semi-stages in which both the input power and the output current have to be managed by the same shared switch. Compared with a conventional two-stages configuration, lower circuit complexity and cost, reduced component count and higher compactness can be achieved through integration, at cost of increased stress levels on the power switch and of losing a degree of freedom in converter design. Galvanic isolation can be provided or not depending on the topologies selected for integration. If non-isolated topologies are considered for both semi-stages, the user safety has to be guaranteed by assuring mechanical isolation throughout the LED lamp case. The issue, deriving from the need of smoothing the pulsating power absorbed from the line while avoiding the use of short lifetime electrolytic capacitors, will be addressed. A set of integrated topologies, used as HBLED lamp power supplies, will be investigated and a generalized analysis will be presented. Their input line voltage ripple attenuation capability will be examined and a general design procedure will be described. Moreover, a novel integrated solution, based on the use of a double buck converter, for an about 15W rated down-lighting application will be presented. The analysis performed, together with converter design and power factor correction concerns will be carefully discussed and the main outcomes of the tests performed at simulation level will be provided. The last kind of approach to be discussed is based on a multi-stage structure that results to be a suitable option for medium power applications, like street lighting, in which compactness is not a major concern. By adopting such kind of solution it is, indeed, possible to optimize converter’s behavior both on line and on load side, thereby guaranteeing both an effective power factor correction at the input and proper current regulation and dimming capability at the output. Galvanic isolation can be provided either by the input or the output stage, resulting in a standard two stage configuration, or by an additional intermediate isolated DC-DC stage (operating in open loop with a constant input/output voltage conversion ratio) that namely turns the AC/DC converter topology into a three stage configuration. The efficiency issue, deriving from the need of multiple energy processing along the path between the utility grid and the LED load, can be effectively addressed thanks to the high flexibility guaranteed by this structure that, relaxing the design constraint, allows to easily optimize each stage. A 150W nominal power rated ballast for street solid state lighting applications, based on the latter (three stage) topology, has been investigated. The analysis performed, the design procedure and the simulations outcomes will be carefully described, as well as the experimental results of the tests made on the implemented laboratory prototype.
Negli ultimi anni i dispositivi LED di potenza ad elevata luminosità (HBLED) hanno attirato in misura sempre crescente l'interesse della comunità scientifica, sia all'interno del mondo accademico che di quello industriale. Tra le varie caratteristiche, che rendono questo tipo di tecnologia interessante, le qualità più apprezzate sono certamente: la robustezza, l'elevata efficienza, le piccole dimensioni, la facilità di modulazione dell'intensità luminosa, il lungo tempo di vita, l'estrema rapidità di accensione e spegnimento e l'assenza di mercurio. Nonostante tutti questi aspetti sembrino dare alla tecnologia a stato solido un netto vantaggio rispetto alle tecnologie concorrenti, l'utilizzo dei LED di potenza nel campo dell'illuminazione rimane a tutt'oggi abbastanza limitato. La necessità di ulteriori progressi nella tecnologia dei dispositivi, da un lato, e dello sviluppo di soluzioni in grado di garantirne il corretto ed efficiente pilotaggio, dall'altro, ne hanno, infatti, fino ad ora frenato la diffusione rispetto alle attese. Quest'ultimo aspetto, in particolare, è al giorno d'oggi considerata il vero "collo di bottiglia" in vista dell'impiego su larga scala della tecnologia a stato solido, in sostituzione delle soluzioni, tutt'ora dominanti nel mercato dell'illuminazione, basate sull'utilizzo di lampade alogene e a fluorescenza. Se, da un lato, infatti, è vero che alcuni aspetti della tecnologia dei dispositivi (e.g. variabilità delle prestazioni con la temperatura, qualità della luce, calo dell'efficienza luminosa con l'aumentare della corrente, elevato costo per lumen, ecc...) necessitano di essere ulteriormente perfezionati, dall'altro è ormai universalmente riconosciuto che l'elemento chiave per l'ampia diffusione dell'illuminazione a stato solido è proprio l'ottimizzazione dello stadio di alimentazione. In particolare, le specifiche più importati che un ballast per lampade a LED è tenuto a soddisfare sono: elevata affidabilità ed efficienza, elevato fattore di potenza, capacità di regolazione della corrente di uscita e di modulazione del flusso luminoso, basso costo e minimo ingombro (soprattutto nell'illuminazione domestica). L'obiettivo principale è, quindi, riuscire ad ideare soluzioni basate sull'utilizzo di topologie semplici, caratterizzate da ridotto numero di componenti e limitati livelli di stress di corrente e tensione, che non prevedano l'impiego di componenti con breve tempo di vita come i condensatori elettrolitici. Inoltre, nelle applicazioni in cui la compattezza è considerata uno degli aspetti di maggior rilievo, anche la capacità di operare in soft-switching diviene una specifica indispensabile. Ciò è infatti necessario al fine di permettere la minimizzazione del volume delle componenti reattive, tramite l'aumento della frequenza di commutazione nel range delle centinaia di kHz, senza compromettere l'efficienza del convertitore. Per completezza, vale la pena di ricordare che, per ottimizzare il funzionamento dei LED ad elevata luminosità, andrebbero presi in considerazione anche altri aspetti, come ad esempio le problematiche legate alla gestione del calore dissipato dalla lampada, importanti al fine di limitare gli stress termici subiti dai dispositivi e, di conseguenza, migliorare la qualità della luce emessa e massimizzare il tempo di vita della lampada. Tuttavia, essendo il lavoro presentato in questa tesi centrato sulle questioni relative allo stadio di alimentazione, i suddetti problemi di gestione termica, come anche gli aspetti relativi allo sviluppo della tecnologia dei dispositivi non verranno esaminati. L'obiettivo principale del lavoro che verrà descritto nel corso dei prossimi capitoli, è, infatti, la ricerca di soluzioni innovative per il pilotaggio da rete elettrica di lampade basate su tecnologia a stato solido. Verranno pertanto approfonditamente trattate le tematiche relative ad analisi, ottimizzazione e sviluppo di topologie che siano in grado di soddisfare i requisiti precedentemente enunciati e di affrontare con successo le sfide proposte dalla continua evoluzione dello scenario del "general lighting". Per prima cosa, sarà fornita una visione di insieme riguardante lo stato dell'arte del mercato dell'illuminazione, le caratteristiche dei dispositivi di illuminazione a stato solido ed i principali aspetti relativi al loro pilotaggio. Dopo questa prima sezione introduttiva, la tematica relativa all'alimentazione da rete elettrica di tali dispositivi verrà approfonditamente discussa. Differenti modi di approcciare il problema, a seconda della specifica applicazione considerata, verranno discussi. Il primo tipo di approccio che verrà esaminato si basa sull'uso di una semplice struttura, formata da un singolo stadio di conversione di potenza. Essa è in grado di fornire al contempo il rispetto degli standard che limitano il contenuto armonico della corrente di ingresso, l'isolamento galvanico e la regolazione della corrente e dell'intensità luminosa in uscita. I vincoli, dettati dall'esigenza di garantire il rispetto della normativa EN 61000-3-2, in applicazioni di bassa potenza (<15W) prive di uno stadio dedicato alla correzione del fattore di potenza, verranno approfonditamente trattati. Saranno, poi, illustrati i risultati dello studio, sviluppo ed ottimizzazione di un convertitore a singolo stadio, operante ad elevata frequenza di commutazione, basato sulla topologia flyback a mezzo ponte asimmetrico. La semplicità, il ridotto numero di componenti ed il basso costo, che caratterizzano tale tipo di soluzione, la rendono adatta all'alimentazione di lampade per il settore residenziale, in cui la compattezza dello stadio di alimentazione è di fondamentale importanza al fine di consentirne l'alloggiamento nei classici socket E27. L'analisi effettuata, la procedura di progetto ed risultati ottenuti in simulazione ed a livello sperimentale durante lo studio di tale topologia verranno accuratamente descritti e discussi. Un altro interessante tipo di approccio che verrà considerato si basa sull'utilizzo di topologie integrate, nelle quali due diversi stadi di conversione vengono uniti tramite la condivisione dello stesso interruttore di potenza e della relativa circuiteria di comando. Nel convertitore che ne risulta, la correzione del fattore di potenza e la regolazione della corrente nei LED saranno dunque garantite dalla combinazione dei due semi-stadi, il cui interruttore comune dovrà essere in grado di gestire sia la potenza di ingresso che la corrente di uscita. Rispetto alla configurazione a due stadi convenzionale, la soluzione ottenuta tramite l'integrazione consente una minore complessità circuitale, un ridotto numero di componenti e, di conseguenza, una maggiore compattezza ed un minor costo. Tutto ciò viene guadagnato a scapito di un maggiore livello di stress nei componenti e della perdita di un grado di libertà nel progetto del convertitore. L'isolamento galvanico può essere garantito o meno a seconda del tipo di topologie che vengono selezionate per l'integrazione. Se la scelta ricade su topologie non isolate, la sicurezza dell'utente andrà comunque garantita isolando meccanicamente l'involucro della lampada. I problemi legati alla necessità di smorzare la componente alternata della potenza assorbita dalla rete, evitando al contempo l'utilizzo di componenti con basso tempo di vita, come i condensatori elettrolitici, verranno discussi. A tal proposito si studieranno le caratteristiche di un insieme di topologie integrate, al fine di fornirne un'analisi ed una procedura di design generalizzate. Se ne esaminerà, inoltre, la capacità di attenuare la componente ondulatoria della tensione di ingresso che viene trasferita al carico, dove si traduce in un'oscillazione della corrente di alimentazione fornita ai LED. Verrà proposta, poi, una soluzione basata su una topologia derivante dall'integrazione di due convertitori di tipo step-down (abbassatori di tensione), per applicazioni di "down-lighting", dimensionata per una potenza di circa 15W. Se ne discuteranno, in particolare, i dettagli di maggiore interesse relativi all'analisi effettuata, alla procedura di progetto ed ai risultati dei test effettuati in ambiente di simulazione. L'ultimo tipo di approccio considerato prevede, infine, l'utilizzo di una topologia multi-stadio, ritenuta una scelta appropriata soprattutto per applicazioni lighting di potenza elevata (>60W), come l'illuminazione stradale, in cui la compattezza dell'alimentatore non è ritenuta un aspetto di primaria importanza. Tramite questo tipo di soluzione è, infatti, possibile ottimizzare le prestazioni del convertitore sia dal lato della rete che dal lato del carico. Si riescono a garantire, in tal modo, un'efficace correzione del fattore di potenza, un adeguato controllo della corrente di uscita ed un'appropriata modulazione del flusso luminoso emesso dalla lampada. L'isolamento galvanico può essere fornito dallo stadio di ingresso o da quello di uscita o da un aggiuntivo stadio DC-DC intermedio, operante a catena aperta con rapporto di conversione di tensione costante. In quest'ultimo caso la struttura del convertitore, si trasforma, dalla classica configurazione a due stadi, in una topologia a triplo stadio. Il problema che nasce dalla necessità di assicurare un elevato livello di efficienza del sistema, nonostante l'interposizione di ripetuti stadi di conversione dell'energia tra la rete ed il carico a LED, può essere efficacemente risolto grazie alla flessibilità che caratterizza tale tipo di struttura. L'aumento del numero dei gradi di libertà in fase progettuale permette, infatti, di ottimizzare con semplicità ogni singolo stadio. Per comprovare limiti e potenzialità di tale tipo di approccio, si è deciso di studiare un ballast (dimensionato per una potenza nominale di 150W) basato sulla topologia a triplo stadio precedentemente menzionata, per applicazioni nell'ambito dell'illuminazione stradale. L'analisi condotta, la procedura di progetto ed i risultati delle simulazioni effettuate verranno discussi nel dettaglio, così come i risultati sperimentali dei test di laboratorio effettuati sul prototipo costruito.

Uno de los campos más importantes de la Electrónica de Potencia es el de los convertidores de potencia conmutados, que debido a sus características de alto rendimiento energético, reducido tamaño, posibilidades de regulación del factor de potencia y de elevación de tensión, etc., están presentes en un gran número de las etapas de alimentación de los equipos electrónicos actuales.
Las mejoras tecnológicas en ámbitos como el de la integración de circuitos han permitido importantes reducciones en el tamaño de los equipos (por ejemplo en los ordenadores). Sin embargo, este proceso de reducción de tamaño que, además, suele venir unido a unas especificaciones más rígidas en cuanto a costes, rendimiento, seguridad y prestaciones en general, no se ha producido en igual medida en las etapas de alimentación. El estudio de los convertidores conmutados es por lo tanto un campo necesitado de esfuerzos de investigación y desarrollo.
Para potencias superiores a 25 W, y especialmente en potencias superiores a 150 W, una de las estrategias utilizadas para mejorar las prestaciones de los convertidores es el uso del denominado "interleaving" o entrelazado , definido como la puesta en paralelo de N convertidores idénticos desfasando sus señales de control de forma uniforme a lo largo del periodo de conmutación.
Con el objetivo principal de reducir al máximo los rizados de la tensión de salida y de la corriente de entrada, en esta tesis se estudian casos particulares de "interleaving" en estructuras convertidoras continua-continua que utilizan el convertidor elevador ("boost") como célula básica y cuyas tensiones de salida son, idealmente y operando en modo de conducción continua, múltiplos enteros positivos de la tensión de entrada, de ahí la denominación de multiplicadores de tensión que aparece en el título de tesis propuesto. Posteriormente se analizan las posibilidades de regulación de tensión que presentan algunos de los casos de estudio, a costa de incrementar los rizados.

The use of SMPS (Switched mode power supply) in embedded systems is continuously increasing. The technological requirements of these systems include simultaneously a very good voltage regulation and a strong compactness of components. SEPIC ( Single-Ended Primary Inductor Converter) is a DC/DC switching converter which possesses several advantages with regard to the other classical converters. Due to the difficulty in control of its 4th-order and non linear property, it is still not well-exploited. The objective of this work is the development of successful strategies of control for a SEPIC converter on one hand and on the other hand the effective implementation of the control algorithm developed for embedded applications (FPGA, ASIC) where the constraints of Silicon surface and the loss reduction factor are important. To do it, two non linear controls and two observers of states and load have been studied: a control and an observer based on the principle of sliding mode, a deadbeat predictive control and an Extended Kalman observer. The implementation of both control laws and the Extended Kalman observer are implemented in FPGA. An 11-bit digital PWM has been developed by combining a 4-bit Δ-Σ modulation, a 4-bit segmented DCM (Digital Clock Management) phase-shift and a 3-bit counter-comparator. All the proposed approaches are experimentally validated and constitute a good base for the integration of embedded switching mode converters

Orientador: Ernesto Ruppert Filho
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
Made available in DSpace on 2018-08-21T00:56:13Z (GMT). No. of bitstreams: 1 Dias_AgnaldoVieira_M.pdf: 2229736 bytes, checksum: 725a7fa267bc30780c457689e4356336 (MD5) Previous issue date: 2012
Resumo: O estudo da utilização de conversores CC/CC isolados e elevadores de tensão para a alimentação de moduladores de pulsos é apresentado neste trabalho. Foi selecionada a topologia em ponte completa, dando-se enfoque ao problema das capacitâncias parasitas envolvidas no circuito, que aparecem de forma acentuada em transformadores elevadores de tensão e filtros indutivos de saída e são altamente indesejáveis quando se opera em regime chaveado. Essas capacitâncias são tratadas através de uma forma de amortecimento, onde a energia armazenada nas mesmas é devolvida à fonte primária ao final de cada semiciclo de chaveamento, tentando obter-se menor volume, maior rendimento e menor dissipação de calor no conversor. Além disso, um circuito de regulação de carga é utilizado para garantir uma maior estabilidade de pulso e contornar problemas típicos de moduladores de pulsos utilizados em radares, como o efeito de backswing. O modulador de pulsos utilizado como carga para esse sistema opera com uma tensão de alimentação de 1kV, frequência de repetição de pulsos (PRF) de 585Hz e consome uma potência da ordem de 2,1kW. O conversor CC/CC é alimentado por um barramento CC não regulado de 280V
Abstract: The study of high-voltage isolated DC/DC converters used to supply pulse modulators is presented on this dissertation. The Full Bridge topology was selected, focusing in problems caused by parasitic capacitances in the circuit. This characteristic, which appears sharply in high voltage transformers and in inductors of output filter, is highly undesirable when the circuit is operated in switching mode. These capacitances are handled using a soft commutation technique, where their stored energy are returned to the primary source in the end of each switching cycle, trying to get a low size, high efficiency and low heat dissipation in the converter. Moreover, a charging regulator circuit is used to ensure good pulse stability and avoid typical problems in the pulse modulators use, such as the backswing effect. The pulse modulator used as load for this converter operates with a supply voltage of 1kV, pulse repetition frequency (PRF) of 585Hz and consumes 2.1 kW. The converter input is supplied by a 280V unregulated DC bus
Mestrado
Energia Eletrica
Mestre em Engenharia Elétrica

En aquesta tesi s'utilitza la noció de resistor lliure de pèrdues (LFR) per dissenyar fonts d'alimentació destinades a iluminació eficient com son els light emmiting diodes (LEDs), làmpades d'alta intensitat de descàrrega (HID) i làmpades d'inducció sense electrodes (IEFL), amb la finalitat de reduir el consum elèctric tant en aplicacions domèstiques com industrials. Aprofitant la naturalesa del LFR, es a dir, un resistència emulada al port d'entrada y una font de potència al port de sortida, les làmpades mencionades anteriorment son alimentades a potència constant independentment del tipus de làmpada i de la seva impedància. La técnica de control en mode de lliscament ha sigut aplicada als convertidors per imposar el comportament de LFR treballant en mode de conducció contínu (CCM) en alguns casos, i en d'altres a la frontera entre CCM i mode de conducció discontinu (DCM). Aquesta técnica de control que s'ha utilitzat al llarg de la tesi, ha estat implementada mitjançant técniques de control analògiques i digitals, permetent regular la llum de les làmpades.
En esta tesis se usa la noción de resistor libre de pérdidas (LFR) para diseñar fuentes de alimentación destinadas iluminación eficiente como por ejemplo light emmiting diodes (LEDs), lamparas de alta intensidad de descarga (HID) y lámparas de inducción sin electrodos (IEFL), con el fin de reducir el consumo eléctrico tanto en aplicaciones domésticas como industriales. Aprovechando la naturaleza del LFR, es decir, una resistencia emulada en el puerto de entrada y una fuente de potencia en el puerto de salida, las lámparas mencionadas anteriormente son alimentadas a potencia constante independientemente del tipo de lámpara e impedancia de la misma, . La técnica de control en modo de deslizamiento es aplicada en los convertidores para imponer el comportamiento de LFR trabajando en modo de conducción continuo (CCM) en algunos casos, y en otros en la frontera entre CCM y modo de conducción discontinuo (DCM). Ésta técnica de control que se a implementado a lo largo de toda la tesis ha sido implementada mediante técnicas de control tanto analógicas como digitales permitiendo regular la luz de las lámparas.
In this thesis, the notion of loss-free resistor (LFR) is used systematically to design power supplies for efficient lighting, namely light emitting diodes (LEDs), high intensity-discharge lamps (HID) and induction electrode-less fluorescent lamps (IEFLs) with the aim of reducing the electrical energy consumption in domestic or industrial applications. The different lamps previously mentioned are supplied at constant power independently of the lamp type and impedance, taking advantage of the LFR nature, i.e. an emulated resistance in the input port and a power source in the output port. The sliding -mode control technique is applied in the converters to impose the LFR behaviour in continuous conduction mode (CCM) in some cases, and in the boundary between CCM and discontinuous conduction mode (DCM) in other cases. This control technique has been implemented throughout the thesis by either analogue or digital controllers and allows regulating the light emitted by the lamps.

Measurement-based behavioral electromagnetic interference (EMI) models have been shown earlier to accurately capture the EMI behavior of switched power converters. These models are compact, linear, and run in frequency domain, enabling faster and more stable simulations compared to the detailed lumped circuit models. So far, the behavioral EMI modeling techniques are developed and applied to the converter's input side only. The resulting models are therefore referred to as "terminated EMI models". Under the condition that the output side of the converter remains fixed, these models can predict the input side EMI for any change in the impedance of the input side network. However, any change at the output side would require re-extraction of the behavioral model. Thus the terminated EMI models are incapable of predicting the change in the input side EMI due to changes at the output side of the converter or vice versa. The above mentioned limitation has been overcome by an "un-terminated EMI model" proposed in this dissertation. Un-terminated EMI models are developed here to predict both the common-mode (CM) and the differential (DM) noise currents at the input and the output sides of a motor-drive system. The modeling procedure itself has been simplified and now requires fewer measurements and results in less noise in the identified model parameters. Both CM and DM models are then combined to predict the total noise in the motor drive system. All models are validated by experiments and their limitations identified. A significant portion of this dissertation is then devoted to the application of behavioral EMI models in the design of EMI filters. Comprehensive design procedures are developed for both DM and CM filters in a motor-drive system. The filters designed using the proposed methods are experimentally shown to satisfy the DO-160 conducted emissions standards. The dissertation ends with a summary of contributions, limitations, and some future research directions.
Ph. D.

Les travaux présentés ici proposent des convertisseurs d’énergie à haut rendement et très large dynamique de tension d’entrée, c'est-à-dire capables de fonctionner avec un rendement énergétique élevé sur une plage de tension d’entrée étendue (typiquement de 9V à 200V). De multiples tensions de réseaux sont standards dans l’industrie : elles sont spécifiques à un domaine (aéronautique, ferroviaire, …) et dépendent de la source primaire d’alimentation électrique (batterie d’accumulateurs, génératrice, …). Au sein d’un équipement embarqué, plusieurs réseaux peuvent cohabiter : une alimentation principale 110V et une alimentation de secours sur batterie 12V, par exemple. Le besoin de convertisseurs large dynamique d’entrée est donc une réalité, mais il n’existe sur le marché que peu de convertisseurs capables de réaliser une dynamique d’entrée supérieure à dix. Dans un premier temps, nous avons étudié les enjeux et les problématiques liés à la large dynamique d’entrée, afin de mieux cerner les limitations des topologies de puissance classiques. Nous avons ensuite traité le cas d’une architecture de conversion d’énergie de type série, dont nous avons amélioré le rendement énergétique grâce à l’utilisation de circuits d’aide à la commutation. Cette solution ayant des performances limitées, nous avons proposé de nouvelles architectures de convertisseurs DC/DC, de type parallèle, capables de supporter des dynamiques de tension d’entrée supérieures à vingt et ayant un rendement énergétique élevé (supérieur à 80%). Nous avons également étudié et mis en œuvre des stratégies de commande, numériques et analogiques, permettant de contrôler ces nouvelles topologies complexes
Power converters are present in virtually every embedded system, but many standards of DC networks exist: the supply voltage is depending on how the power is generated (battery, alternator …) and can range from 12V to more than 115V. When an equipment must comply with a 110V main supply and 12V back-up supply, the use of a wide input voltage range DC/DC converter is mandatory. Since classical switched mode power converters cannot achieve simultaneously high efficiency and wide input voltage range, manufacturers rarely propose DC/DC converters with an input voltage range greater than 10. This work tackles the issue of wide input voltage power conversion. After discussing about designs trade off and problems that stem from a wide input range, we try to improve the overall efficiency of a classical buck-boost converter, by using non dissipative switching-aid circuits. We also proposed a novel two stages power converter capable of dealing with very wide input voltage ranges (more than 20), without a reduction of the power efficiency. Since those new converters are far more difficult to control, some theoretical analysis was performed and some practical tests were done using complex controls laws

The thesis consists of an introduction and four appended papers. In the introduction we give an overview of pulse-modulated systems and provide a few examples of such systems. Furthermore, we introduce the so-called dynamic phasor model which is used as a basis for analysis in two of the appended papers. We also introduce the harmonic transfer function and finally we provide a summary of the appended papers. The first paper considers stability analysis of a class of pulse-width modulated systems based on a discrete time model. The systems considered typically have periodic solutions. Stability of a periodic solution is equivalent to stability of a fixed point of a discrete time model of the system dynamics. Conditions for global and local exponential stability of the discrete time model are derived using quadratic and piecewise quadratic Lyapunov functions. A griding procedure is used to develop a systematic method to search for the Lyapunov functions. The second paper considers the dynamic phasor model as a tool for stability analysis of a general class of pulse-modulated systems. The analysis covers both linear time periodic systems and systems where the pulse modulation is controlled by feedback. The dynamic phasor model provides an $\textbf{L}_2$-equivalent description of the system dynamics in terms of an infinite dimensional dynamic system. The infinite dimensional phasor system is approximated via a skew truncation. The truncated system is used to derive a systematic method to compute time periodic quadratic Lyapunov functions. The third paper considers the dynamic phasor model as a tool for harmonic analysis of a class of pulse-width modulated systems. The analysis covers both linear time periodic systems and non-periodic systems where the switching is controlled by feedback. As in the second paper of the thesis, we represent the switching system using the L_2-equivalent infinite dimensional system provided by the phasor model. It is shown that there is a connection between the dynamic phasor model and the harmonic transfer function of a linear time periodic system and this connection is used to extend the notion of harmonic transfer function to describe periodic solutions of non-periodic systems. The infinite dimensional phasor system is approximated via a square truncation. We assume that the response of the truncated system to a periodic disturbance is also periodic and we consider the corresponding harmonic balance equations. An approximate solution of these equations is stated in terms of a harmonic transfer function which is analogous to the harmonic transfer function of a linear time periodic system. The aforementioned assumption is proved to hold for small disturbances by proving the existence of a solution to a fixed point equation. The proof implies that for small disturbances, the approximation is good. Finally, the fourth paper considers control synthesis for switched mode DC-DC converters. The synthesis is based on a sampled data model of the system dynamics. The sampled data model gives an exact description of the converter state at the switching instances, but also includes a lifted signal which represents the inter-sampling behavior. Within the sampled data framework we consider H-infinity control design to achieve robustness to disturbances and load variations. The suggested controller is applied to two benchmark examples; a step-down and a step-up converter. Performance is verified in both simulations and in experiments.
QC 20100628

Switch Mode Power Supplies are very important components in present day electronics and have continued to thrive and grow over the past 25 years. This thesis looks inside how the SMPS have evolved over the passage of years with special emphasis to the Synchronous Buck Converter. It also discusses why there is a strong potential to further the study related to designs based around a Synchronous Buck Converter for portable applications. The main objective of the thesis is to look into the controller design for minimizing size, enhancing efficiency and reliability of power converters in portable electronic equipment such as mobile phones and PDAs. The thesis aims to achieve this using a 90 nm process with an input voltage of 1.55V and an output of 1V with a power dissipation of 200mW.

A power electronic switch-mode three-leg converter is a flexible converter and hence very useful for practical teaching of several disciplines within electric power engineering. It can be used as a half-bridge, full-bridge and three-phase converter, to mention a few, and enables the user to study many different power electronic topologies. The converter, controlled by a microcontroller, can also be used for teaching digital control of power electronics. Its output can be varied in frequency, magnitude and waveforms, and can also be measured by the microcontroller. The flexibility of the converter makes it possible to utilize it in drive circuits for a wide range of loads and can therefore also be used for teaching electric drive systems.This thesis shows a solution of how to design the switch-mode three-leg power electronic converter. The converter is designed and implemented on a printed circuit board (PCB) together with other necessary components. To meet the safety requirements of the problem description, the power rating is low, 12 A * 50 V, and the power circuit is isolated from the microcontroller on the PCB. The microcontroller chosen is the Texas Instruments PiccoloTM ControlCARD and pulse-width modulation and analog-to-digital conversion is implemented with real-time programming.This system developed is verified, except for the MOSFET drivers and measurement circuits. As time was limited, the laboratory work had to be ended in favor of writing the report. Unfortunately, this made it impossible to test the full system setup. A full description of the changes to be implemented for the whole system to be functioning and further tested is provided.A system for using the converter designed in a DC motor drive, by utilizing two of the bridge-legs as a full-bridge converter, is studied. The programming code is tailored for the specific purpose and speed measurements and control algorithms were added. Due to the converter not functioning, the testing of the DC motor drive could not be performed. However, full planning and controller implementation was done.

A method to obtain the exact control-to-output and input-to-output transfer functions for switched DC-to-DC pulse-width modulated power converters is applied to different combinations of operating conditions such as continuous conduction mode (CCM), discontinuous conduction mode (DCM), and discontinuous voltage mode (DVM) and methods of control such as normal voltage mode (NVM), current programming mode (CPM), and V-squared control. The majority of these combinations have not previously had their transfer functions of interest derived to the accuracy provided by the method. The derivation of the method is covered, and the results from its application are verified by simulation. The simulation method is also justied and proposed as an improvement to the methods used by simulation engines for switched mode power supply design such as SIMPLIS.

Increasing the power density of power electronic converters while reducing or maintaining the same cost, offers a higher potential to meet the current trend inrelation to various power electronic applications. High power density converters can be achieved by increasing the switching frequency, due to which the bulkiest parts, such as transformer, inductors and the capacitor's size in the convertercircuit can be drastically reduced. In this regard, highly integrated planar magnetics are considered as an effective approach compared to the conventional wire wound transformers in modern switch mode power supplies (SMPS). However, as the operating frequency of the transformers increase from several hundred kHz to MHz, numerous problems arise such as skin and proximity effects due to the induced eddy currents in the windings, leakage inductance and unbalanced magnetic flux distribution. In addition to this, the core losses whichare functional dependent on frequency gets elevated as the operating frequency increases. Therefore, this thesis provides an insight towards the problems related to the high frequency magnetics and proposes a solution with regards to different aspects in relation to designing high power density, energy efficient transformers.The first part of the thesis concentrates on the investigation of high power density and highly energy efficient coreless printed circuit board (PCB) step-down transformers useful for stringent height DC-DC converter applications, where the core losses are being completely eliminated. These transformers also maintain the advantages offered by existing core based transformers such as, high coupling coefficient, sufficient input impedance, high energy efficiency and wide frequencyband width with the assistance of a resonant technique. In this regard, several coreless PCB step down transformers of different turn’s ratio for power transfer applications have been designed and evaluated. The designed multilayered coreless PCB transformers for telecom and PoE applications of 8,15 and 30W show that the volume reduction of approximately 40 - 90% is possible when compared to its existing core based counterparts while maintaining the energy efficiency of the transformers in the range of 90 - 97%. The estimation of EMI emissions from the designed transformers for the given power transfer application proves that the amount of radiated EMI from a multilayered transformer is lessthan that of the two layered transformer because of the decreased radius for thesame amount of inductance.The design guidelines for the multilayered coreless PCB step-down transformer for the given power transfer application has been proposed. The designed transformer of 10mm radius has been characterized up to the power level of 50Wand possesses a record power density of 107W/cm3 with a peak energy efficiency of 96%. In addition to this, the design guidelines of the signal transformer fordriving the high side MOSFET in double ended converter topologies have been proposed. The measured power consumption of the high side gate drive circuitvitogether with the designed signal transformer is 0.37W. Both these signal andpower transformers have been successfully implemented in a resonant converter topology in the switching frequency range of 2.4 – 2.75MHz for the maximum load power of 34.5W resulting in the peak energy efficiency of converter as 86.5%.This thesis also investigates the indirect effect of the dielectric laminate on the magnetic field intensity and current density distribution in the planar power transformers with the assistance of finite element analysis (FEA). The significanceof the high frequency dielectric laminate compared to FR-4 laminate in terms of energy efficiency of planar power transformers in MHz frequency region is also explored.The investigations were also conducted on different winding strategies such as conventional solid winding and the parallel winding strategies, which play an important role in the design and development of a high frequency transformer and suggested a better choice in the case of transformers operating in the MHz frequency region.In the second part of the thesis, a novel planar power transformer with hybrid core structure has been designed and evaluated in the MHz frequency region. The design guidelines of the energy efficient high frequency planar power transformerfor the given power transfer application have been proposed. The designed corebased planar transformer has been characterized up to the power level of 50W and possess a power density of 47W/cm3 with maximum energy efficiency of 97%. This transformer has been evaluated successfully in the resonant converter topology within the switching frequency range of 3 – 4.5MHz. The peak energy efficiency ofthe converter is reported to be 92% and the converter has been tested for the maximum power level of 45W, which is suitable for consumer applications such as laptop adapters. In addition to this, a record power density transformer has been designed with a custom made pot core and has been characterized in thefrequency range of 1 - 10MHz. The power density of this custom core transformer operating at 6.78MHz frequency is 67W/cm3 and with the peak energy efficiency of 98%.In conclusion, the research in this dissertation proposed a solution for obtaining high power density converters by designing the highly integrated, high frequency(1 - 10MHz) coreless and core based planar magnetics with energy efficiencies inthe range of 92 - 97%. This solution together with the latest semiconductor GaN/SiC switching devices provides an excellent choice to meet the requirements of the next generation ultra flat low profile switch mode power supplies (SMPS).

The use of variable speed drive (VSD) systems in the appliance industry is growing due to emerging high volume of fractional horsepower VSD applications. Almost all of the appliance VSDs have no input power factor correction (PFC) circuits. This results in harmonic pollution of the utility supply which could be avoided. The impact of the PFC circuit in the overall drive system efficiency, harmonic content, magnitude of the system input current and input power factor is particularly addressed in this dissertation along with the development of analytical methods applicable to the steady-state analysis of input power factor corrected VSD systems. Three different types of motors - the switched reluctance motor (SRM), permanent magnet brushless dc motor (PMBDC) and dc motor (DCM) are employed in this study. The C-dump converter topology, a single switch per phase converter, is adopted for the prototype SRM- and PMBDC-based VSD systems. The conventional full-bridge converter is used for DCM-based VSD systems. Four-quadrant controllers, utilizing PI speed and current control loops for the PMBDC- and DCM-based VSD system, are developed and their design results are verified with experiment and simulation. A single-quadrant controller with a PI speed feedback loop is employed for the SRM-based VSD system. The analysis of each type of VSD system includes development of loss models and establishment of proper operational modes. The magnitude of the input current harmonic spectra is measured and compared with and without a front-end PFC converter. One electromagnetic compatibility (EMC) standard, IEC 1000-3-2 which describes the limitation on harmonic current emission is modified for 120V ac system. This modified standard is utilized as the reference to evaluate the measured input current harmonics. The magnitude of input current harmonics for a VSD system are greatly reduced with PFC preregulators. While the input PFC circuit draws a near sinusoidal current from an ac source, it lowers the overall VSD system efficiency and increases cost of the overall system.
Ph. D.

Digitally-controlled, high power universal telecommunication power supply modules have been developed. In this work, the converter control strategy, and its design and implementation first, by means of parallel-operated, dual, 8-bit microcontrollers, and then by using a high processing power digital signal processor (DSP) have been emphasized. The proposed dual-processor based digital controller provides an extended operating output voltage range of the power supplies, user programmable current limit setting, serial communication based active load current sharing with automatic master-slave selection among parallel-operated modules, user selectable number of back-up battery cells, programmable temperature compensation curves, and automatic derating without extra hardware requirement. Overload and output short-circuit protection features are also controlled by software. One of the processors in the digital controller is employed for user interface purposes such as long term records, display, and alarm facilities, and remote control, which are inherently slow processes. The fast processing speed required by output voltage setting, current limit, and load current sharing however is to be fulfilled by a second processor dedicated to the adjustment of output voltages of modules. Tight dynamic load regulation requirement of a telecommunication power supply has been fulfilled by a 150 MIPS DSP, in place of a low cost, 8-bit microcontroller. The implemented digitally-controlled, 1.8 kW, 0-70V telecommunication power supplies have been tested successfully in several locations in the field.

Thesis (MEng)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: The development of fast and efficient processors, programmable devices and high power semiconductors has led to the increased use of semiconductors directly in the power supply path in order to achieve strict power quality standards. New and advanced algorithms are used in the process and calculated on-line to bring about the required fast response to voltage variations. Losses in high voltage semiconductors increase with increased operating frequencies. A balance between semiconductor power losses and power quality is achieved through control of power semiconductor switching frequencies. A predictive control algorithm to achieve high power quality and limit the power losses in the high power semiconductor switches through switching frequency control is discussed for a tap switched voltage regulator. The quality of power, voltage regulator topology and the control algorithm are discussed. Simulation results of output voltage and current are shown when the control algorithm is used to control the regulator. These results are verified by practical measurements on a synchronous buck converter.
AFRIKAANSE OPSOMMING: Die ontwikkeling van vinnige en doeltreffende verwerkers, programmeerbare toestelle en hoëdrywings halfgeleiers het gelei tot 'n groter gebruik van halfgeleiers direk in die kragtoevoer pad om streng elektriese toevoer kwaliteit standaarde te bereik. Nuwe en gevorderde algoritmes word gebruik in die proses en word aan-lyn bereken om die nodige vinnige reaksie tot spanningswisselinge te gee. Verliese in hoë-spannings halfgeleiers verhoog met hoër skakel frekwensies. 'n Balans tussen die halfgeleier drywingsverliese en spanningskwalteit is behaal deur die skakel frekwensie in ag te neem in die beheer. 'n Voorspellinde-beheer algoritme om ‘n hoë toevoerkwaliteit te bereik en die drywingsverliese in die hoëdrywingshalfgeleier te beperk, deur skakel frekwensie te beheer, is bespreek vir 'n tap-geskakelde spanning reguleerder. Die toevoerkwaliteit, spanningsreguleerder topologie en die beheer algoritme word bespreek. Simulasie resultate van die uittree-spanning en stroom word getoon wanneer die beheer algoritme gebruik word om die omsetter te beheer. Hierdie resultate is deur praktiese metings op 'n sinkrone afkapper.

Dissertação para obtenção do grau de Mestre em Engenharia Electrotécnica e de Computadores
Pipeline Analog-to-digital converters (ADCs) are the most popular architecture for high-speed medium-to-high resolution applications. A fundamental, but often unreferenced building block of pipeline ADCs are the reference voltage circuits. They are required to maintain a stable reference with low output impedance to drive large internal switched capacitor loads quickly. Achieving this usually leads to a scheme that consumes a large portion of the overall power and area. A review of the literature shows that the required stable reference can be achieved with either on-chip buffering or with large off-chip decoupling capacitors. On-chip buffering is ideal for system integration but requires a high speed buffer with high power dissipation. The use of a reference with off-chip decoupling results in significant power savings but increases the pads of chip, the count of external components and the overall system cost. Moreover the amount of ringing on the internal reference voltage caused by the series inductance of the package makes this solution not viable for high speed ADCs. To address this challenge, a pipeline ADC employing a multiplying digital-to-analog converter (MDAC) with current-mode reference shifting is presented. Consequently, no reference voltages and, therefore, no voltage buffers are necessary. The bias currents are generated on-chip by a reference current generator that dissipates low power. The proposed ADC is designed in a 65 nm CMOS technology and operates at sampling rates ranging from 10 to 80 MS/s. At 40 MS/s the ADC dissipates 10.8 mW from a 1.2 V power supply and achieves an SNDR of 57.2 dB and a THD of -68 dB, corresponding to an ENOB of 9.2 bit. The corresponding figure of merit is 460 fJ/step.

Established climate changes and increasing regulations on fossil fuels makes it important toexplore different options for electric power generation from renewable energy sources. In 2015Sweden had the highest proportion of renewable energy in the European Union and electricitygeneration contributes the most to the proportion of renewable energy. An interestingopportunity to a further improvement on the number of renewable energy sources is wavepower. Wave power is based on the conversion of energy available in the motion of the wavesto electric power. Electric power generation from wave power plants has been studied since1970 and the major obstacles for its development have been the high costs of the plants and lowefficiencies. The KTH researcher PhD Anders Hagnestål, has developed a new type of wavepower generator with significant improvements on the machine’s efficiency. This master thesisdeals with the electrical energy conversion of the electric power provided by the generator. Thedesign and construction of single-phase switch-mode converter used for the electricalconversion AC/DC and DC/AC of the generated electric power is discussed and explained. Theconstructed single-phase converter showed a good electrical design. Nevertheless, importantimprovements are needed in the operating speed of the used microcontroller.
Etablerade klimatförändringar och ett ökat antal regler för fossila bränslen gör det viktigt attutforska olika alternativ för elproduktion från förnybara energikällor. År 2015 hade Sverige denhögsta andelen förnybar energi i EU och elproduktionen bidrar mest till andelen förnybarenergi. En intressant möjlighet till ytterligare förbättringar av antalet förnybara energikällor ärvågkraft. Vågkraft är baserad på omvandling av energi som finns i vågornas rörelse till elkraft.Elkraftproduktion från vågkraftverk har studerats sedan 1970 och de största hindren för dessutveckling har varit de höga kostnaderna för kraftverket och låg effektivitet. KTH-forskarenPhD Anders Hagnestål har utvecklat en ny typ av vågkraftgenerator med betydandeförbättringar av maskinens effektivitet. Detta examensarbete behandlar elenergiomvandlingenav elenergin som generatorn tillhandahåller. Designen och konstruktionen av enfasig switchmodeeffektomvandlare som används för den elektriska omvandlingen AC/DC och DC/AC avden genererade elenergin diskuteras och förklaras. Den konstruerade enfasomvandlaren hadeen bra elektrisk design. Ändå behövs väsentliga förbättringar i den använda mikroprocessornshastighet.

In this thesis a multifunctional DC/DC converter board will be developed for utilization as an educational experiment set in the switched-mode power conversion laboratory of power electronic courses. The board has a generic power-pole structure allowing for easy configuration of various power converter topologies and includes buck, boost, buck-boost, flyback, and forward converter topologies. All the converters can be operated in the open-loop control mode with a switching frequency range of 30-100 kHz and a maximum output power of 20 W. Also the buck converter can be operated in voltage mode control and the buck-boost converter can be operated in peak-current-mode control for the purpose of demonstrating the closed loop control performance of DC/DC converters. The designed board allows for experimentation on the DC/DC converters to observe the macroscopic (steadystate/ dynamic, PWM cycle and low frequency) and microscopic (switching dynamic) behavior of the converters. In the experiments both such characteristics can be clearly observed such that students at basic learning level (involving only the macroscopic behavior), and students at advanced learning level (additionally involving the parasitic effects) can benefit from the experiments. The thesis reviews the switch mode conversion principles, gives the board design and proceeds with the experiments illustrating the capabilities of the experimental system.

In this thesis
analysis, design and implementation of a DC-DC converter with active clamp forward topology is presented. The main objective of this thesis is generating a rectified sinusoidal voltage at the output of the converter. This is accomplished by changing the reference signal of the converter. The converter output is applied to an inverter circuit in order to obtain sinusoidal waveform. The zero crossing points of the converter is detected and the inverter drive signals are generated in order to obtain sinusoidal waveform from the output of the converter. Next, the operation of the DC-DC converter and sinusoidal output inverter coupled performance is investigated with resistive and inductive loads to find out how the proposed topology performs. The design is implemented with an experimental set-up and steady state and dynamic performance of the designed power supply is tested. Finally an evaluation of how better performance can be obtained from this kind of arrangement to obtain a sinusoidal output inverted is thoroughly discussed

The most essential unit required for all the electronic devices is the Power Supply Unit (PSU). The main objective of power supply designers is to reduce the size, cost and weight, and to increase the power density of the converter. There is also a requirement to have a lower loss in the circuit and hence in the improvement of energy efficiency of the converter circuit. Operating the converter circuits at higher switching frequencies reduces the size of the passive components such as transformers, inductors, and capacitors, which results in a compact size, weight, and increased power density of the converter. At present the switching frequency of the converter circuit is limited due to the increased switching losses in the existing semiconductor devices and in the magnetic area, because of increased hysteresis and eddy current loss in the core based transformer. Based on continuous efforts to improve the new semi conductor materials such as GaN/SiC and with recently developed high frequency multi-layered coreless PCB step down power transformers, it is now feasible to design ultra-low profile, high power density isolated DC/DC and AC/DC power converters. This thesis is focussed on the design, analysis and evaluation of the converters operating in the MHz frequency region with the latest semi conductor devices and multi-layered coreless PCB step-down power and signal transformers. An isolated flyback DC-DC converter operated in the MHz frequency with multi-layered coreless PCB step down 2:1 power transformer has been designed and evaluated. Soft switching techniques have been incorporated in order to reduce the switching loss of the circuit. The flyback converter has been successfully tested up to a power level of 10W, in the switching frequency range of 2.7-4 MHz. The energy efficiency of the quasi resonant flyback converter was found to be in the range of 72-84% under zero voltage switching conditions (ZVS). The output voltage of the converter was regulated by implementing the constant off-time frequency modulation technique. Because of the theoretical limitations of the Si material MOSFETs, new materials such as GaN and SiC are being introduced into the market and these are showing promising results in the converter circuits as described in this thesis. Comparative parameters of the semi conductor materials such as the vi energy band gap, field strengths and figure of merit have been discussed. In this case, the comparison of an existing Si MOSFET with that of a GaN MOSFET has been evaluated using a multi-layered coreless PCB step-down power transformer for the given input/output specifications of the flyback converter circuit. It has been determined that the energy efficiency of the 45 to 15V regulated converter using GaN was improved by 8-10% compared to the converter using the Si MOSFET due to the gate drive power consumption, lower conduction losses and improved rise/fall times of the switch. For some of the AC/DC and DC/DC applications such as laptop adapters, set-top-box, and telecom applications, high voltage power MOSFETs used in converter circuits possess higher gate charges as compared to that of the low voltage rating MOSFETs. In addition, by operating them at higher switching frequencies, the gate drive power consumption, which is a function of frequency, increases. The switching speeds are also reduced due to the increased capacitance. In order to minimize this gate drive power consumption and to increase the frequency of the converter, a cascode flyback converter was built up using a multi-layered coreless PCB transformer and this was then evaluated. Both simulation and experimental results have shown that with the assistance of the cascode flyback converter the switching speeds of the converter were increased including the significant improvement in the energy efficiency compared to that of the single switch flyback converter. In order to further maximize the utilization of the transformer, to reduce the voltage stress on MOSFETs and to obtain the maximum power density from the power converter, double ended topologies were chosen. For this purpose, a gate drive circuitry utilising the multi-layered coreless PCB gate drive transformer was designed and evaluated in both a Half-bridge and a Series resonant converter. It was found that the gate drive power consumption using this transformer was less than 0.8W for the frequency range of 1.5-3.5MHz. In addition, by using this gate drive circuitry, the maximum energy efficiency of the series resonant converter was found to be 86.5% with an output power of 36.5W.

This thesis presents System Identification based On-Line Health Monitoring to analyse the dynamic behaviour of the Switch-Mode Power Converter (SMPC), detect, and diagnose anomalies in passive electronic components. The anomaly detection in this research is determined by examining the change in passive component values due to degradation. Degradation, which is a long-term process, however, is characterised by inserting different component values in the power converter. The novel health-monitoring capability enables accurate detection of passive electronic components despite component variations and uncertainties and is valid for different topologies of the switch-mode power converter. The need for a novel on-line health-monitoring capability is driven by the need to improve unscheduled in-service, logistics, and engineering costs, including the requirement of Integrated Vehicle Health Management (IVHM) for electronic systems and components. The detection and diagnosis of degradations and failures within power converters is of great importance for aircraft electronic manufacturers, such as Thales, where component failures result in equipment downtime and large maintenance costs. The fact that existing techniques, including built-in-self test, use of dedicated sensors, physics-of-failure, and data-driven based health-monitoring, have yet to deliver extensive application in IVHM, provides the motivation for this research ... [cont.].

This thesis presents an active clamp forward converter for use in the Energy Harvesting From Exercise Machines project. Ideally, this converter will find use as the centerpiece in a process that links elliptical trainers to the California grid. This active clamp forward converter boasts a 14V-60V input voltage range and 150W power rating, which closely match the output voltage and power levels from the elliptical trainer. The isolated topology outputs 51V, higher than previous, non-isolated attempts, which allows the elliptical trainers to interact with a central grid-tied inverter instead of many small ones. The final converter operated at greater than 86% efficiency over most of the elliptical trainer’s input range, and produced very little noise, making it a solid choice for this implementation.

The aim of this thesis is design of adjustable switched mode power supply with symmetrical output of 25 V, and switched mode power supply with fixed output voltage of 5 V. Required maximum output current of each outputs is 3 A. At the beginning of the paper function of the basic SMPS topologies is described. Next all reqiured SMPSs are designed and chosen parts of the design are simulated. In the second half of the thesis assembly and testing of PCB are described as well as functions of programs. Last chapter contains results of meassurement of power supply paramters.

L’augmentation des performances des produits portables requièrent une exploitation la plus efficace possible de la batterie afin de permettre à ces produits d’être utilisés le plus longtemps possible avant d’être rechargés. Les circuits en aval ont besoin d’une source de tension stable qui peut varier pour chacun d’entre eux entre 1.0 V et 5.5 V à partir d’une tension d’entrée pouvant varier entre 2.5V et 5V. Un convertisseur DC-DC à 4 interrupteurs de type dévolteur-survolteur apparait comme une solution intéressante permettant des opérations de diminutions et d’augmentations de tension d’une part, et d’autres part le meilleur compromis entre rendement, performances dynamiques et coûts (en termes de place occupée sur le Silicium et sur la carte). ON Semiconductor a développé et produit un prototype en technologie CMOS 0.25 µm (procédé propriétaire) d’un tel convertisseur qui sert d’étude de cas pour la thèse. Le convertisseur opère selon plusieurs modes de fonctionnement (mode dévolteur, mode survolteur et mode dévolteur-survolteur) à cause d’un impératif de fonctionnement en fréquence de commutation fixe. Le mode dévolteur-survolteur est le sujet principal traité dans la thèse. Le mode dévolteur-survolteur, aussi appelé mode de transition, peut être implémenté via plusieurs Séquences de Topologie (SdT) possibles. Trois SdTs sont comparées en termes de rendement parmi lesquelles figure la SdT implémentée par le prototype. Les performances dynamiques du convertisseur dans ses différents mode de fonctionnement sont ensuite étudiées en dérivant les expressions analytiques des fonctions de transfert qui les caractérisent. Les modèles dérivés dans Matlab et Mathcad pour évaluer le rendement et les performances dynamiques du convertisseur sont ensuite utilisés pour développer un outil servant à obtenir un dimensionnement rapide de la boucle de contrôle du convertisseur. À partir de cette étape, la stabilité du convertisseur dans ses différents modes de fonctionnement est analysée en utilisant la théorie de Floquet et un modèle échantillonné-linéarisé du convertisseur permettant l’établissement d’une méthodologie de conception d’un tel convertisseur. Enfin, pour améliorer le rendement en mode de transition pour tous les points de fonctionnement, un algorithme contrôlant la valeur de l’hystérésis du comparateur utilisé dans la boucle de contrôle a été développé en Verilog, simulé dans l’environnement CADENCE et implémenté en FPGA. Cet algorithme peut améliorer le rendement de près de 3% en mode de transition comparé au réglage initial de la valeur d’hystérésis
The increase in the performances of the portable devices calls for an energy conversion from the battery that is the most efficient as possible in order to make the devices last as long as possible. The downstream circuits need a steady voltage supply which can vary for each one of them from 1.0 V to 5.5 V from an input voltage varying between 2.5 V and 5 V. A 4-Switch Buck-Boost (4SBB) DC-DC converter appears to be the solution which can perform step-up and step-down voltage perations and get the best trade-off between fficiency, dynamic performances and costs (in terms of Silicium and Board area). ON Semiconductor has developed and taped out in CMOS 0.25 µm (ON Semiconductor process) a 4SBB converter which serves as the case study of the thesis. The converter operates in multiple modes (namely Buck mode, Boost mode and Buck-Boost mode) due to fixed frequency operations. The Buck-Boost mode is the main topic dealt with in the thesis. The Buck-Boost mode, also called "transition mode", can be implemented using several possible Sequences of Topologies (SoT). Three SoTs are compared in terms of efficiency among which the one implemented in the converter. Then the dynamical performances of the converter are studied for the different modes of operations by deriving the analytical expressions of the relevant transfer functions. The models derived in Matlab and Mathcad to evaluate efficiency and dynamical performances are then used to develop a tool to get a rapid sizing of the converter’s control loop components. From this step, the stability of the converter is analyzed using Floquet’s theory and Sampled-Data modeling enabling the building of a design methodology to design such a converter. Finally, to enhance efficiency in Buck-Boost mode whatever the working conditions, an algorithm controlling the hysteresis value of the control loop’s comparator has been developed in Verilog, simulated in CADENCE and implemented in FPGA. This algorithm can improve efficiency by almost 3% in Buck-Boost mode compared to its default setting

The Power Supply Unit (PSU) plays a vital role in almost all electronic equipment. The continuous efforts applied to the improvement of semiconductor devices such as MOSFETS, diodes, controllers and MOSFET drivers have led to the increased switching speeds of power supplies. By increasing the switching frequency of the converter, the size of passive elements such as inductors, transformers and capacitors can be reduced. Hence, the high frequency transformer has become the backbone in isolated AC/DC and DC/DC converters. The main features of transformers are to provide isolation for safety purpose, multiple outputs such as in telecom applications, to build step down/step up converters and so on. The core based transformers, when operated at higher frequencies, do have limitations such as core losses which are proportional to the operating frequency. Even though the core materials are available in a few MHz frequency regions, because of the copper losses in the windings of the transformers those which are commercially available were limited from a few hundred kHz to 1MHz. The skin and proximity effects because of induced eddy currents act as major drawbacks while operating these transformers at higher frequencies. Therefore, it is necessary to mitigate these core losses, skin and proximity effects while operating the transformers at very high frequencies. This can be achieved by eliminating the magnetic cores of transformers and by introducing a proper winding structure. A new multi-layered coreless printed circuit board (PCB) step down transformer for power transfer applications has been designed and this maintains the advantages offered by existing core based transformers such as, high voltage gain, high coupling coefficient, sufficient input impedance and high energy efficiency with the assistance of a resonant technique. In addition, different winding structures have been studied and analysed for higher step down ratios in order to reduce copper losses in the windings and to achieve a higher coupling coefficient. The advantage of increasing the layer for the given power transfer application in terms of the coupling coefficient, resistance and energy efficiency has been reported. The maximum energy efficiency of the designed three layered transformers was found to be within the range of 90%-97% for power transfer applications operated in a few MHz frequency regions. The designed multi-layered coreless PCB transformers for given power applications of 8, 15 and 30W show that the volume reduction of approximately 40-90% is possible when compared to its existing core based counterparts. The estimation of EMI emissions from the designed transformers proves that the amount of radiated EMI from a three layered transformer is less than that of the two layered transformer because of the decreased radius for the same amount of inductance. Multi-layered coreless PCB gate drive transformers were designed for signal transfer applications and have successfully driven the double ended topologies such as the half bridge, the two switch flyback converter and resonant converters with low gate drive power consumption of about half a watt. The performance characteristics of these transformers have also been evaluated using the high frequency magnetic material made up of NiZn and operated in the 2-4MHz frequency region. These multi-layered coreless PCB power and signal transformers together with the latest semiconductor switching devices such as SiC and GaN MOSFETs and the SiC schottky diode are an excellent choice for the next generation compact SMPS.

KTH is funding a project whose goal is to send a satellite into space. This project is called MIST (Miniature Student Satellite) which is assembled by a team of students at KTH. On the satellite there are experiments that are invented by other teams, in two of those experiments a power supply is required. This thesis is a technical investigation on how to design the power supply to both of those experiments, which are called SiC and Piezo LEGS. Piezo LEGS will investigate how their nanosized motors will behave and function in a space environment. SiC will investigate how their silicone carbide transistors will be affected by the space environment. A team made of four other students was selected to produce SiC experiments and a PCB in which this work is included. A literature study was done to get a better understanding of how power supplies work and to know how to select a good power supply. When the power supplies were selected they were simulated to meet the requirements. The next step was to do a Printed Circuit Board(PCB) for the SiC experiment and Piezo LEGS to be able to test the power supplies functionality in the physical world. Both of the converters reached the required output and characteristics working on their respective PCB. More time is needed for long time testing and optimization on the PCB layouts.
MIST (Miniature Student Satellite) är ett av KTH subventionerat projekt vilket har som mål att skicka upp en satellit i rymden. Projektet kommer omfatta flera olika experiment. Piezo LEGS ska undersöka en motors funktionalitet i rymdmiljö. SiC ska undersöka hur Silicon carbide halvledare och transistorer påverkas av rymdmiljön. Båda experimenten kräver varsin strömförsörjning för att fungera. Detta projekt ska undersöka kraven på strömförsörjning samt testa prototypen av ett kretskort för densamma. Först genomfördes en förstudie av de två typer av regulatorer som vanligtvis används som strömförsörjning, den linjära regulatorn och switch-mode regulatorn för att förklara olika strömförsörjningsteknologier, samt ta reda på de olika miljökraven. Baserat på förstudiens resultat erhölls kunskap för hur tester ska tas fram för funktionalitet av regulatorerna så att de når kraven för MIST för att sedan kunna producera de båda regulatorerna. Målet är att resultatet av simuleringarna på strömförsörjningen ska stämma överens med utfallet av kretskorten som produceras. Mätningar genomfördes på prototyp kretskort som visade att simuleringarna var korrekta och gav strömförsörjningen rätt resultat på kretskorten. Några av funktionerna på regulatorerna hann ej testas på grund av tidsbrist och mycket framtida arbete kvarstår.

This thesis entails the design and fabrication of a smartphone charger that is powered by a bicycle dynamo hub. In addition to the design and validation of the charger prototype, this thesis involves the testing and characterization of the dynamo hub power source, the design and construction of specialized test equipment, and the design and prototyping of a handlebar-mounted case for the smartphone and charging electronics. With the intention of making the device a commercial product, price, aesthetics, and marketability are of importance to the design. An appropriate description of the charger circuit is a microcontroller-based energy management system, tailored to meet strict power demands of current smartphones. The system incorporates a switched-mode power supply, lithium polymer battery, microcontroller, and specialized protection circuitry. Prototype testing confirms that the circuit meets the charging requirements of the smartphone at bicycle speeds ranging from 7 miles per hour to as high as 55 miles per hour.

The diploma thesis is describing how forward converter works. The diploma thesis presents the function of forward converter with demagnetizing winding and presents the function of two-switched forward converter. The diploma thesis descibes the behaviour of continuous current mode and discontinuous current mode. The diploma thesis explains the reasons for implementation feedback and presents the basic types of compensations. The project deals with AC analysis of two-switched forward converter with continuous peak current mode control. The Analog prototyping metod is used for digital control design. The function of the converter was tested in laboratory. The laboratory results have been compared with the theoretical and the simulation results.

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O presente trabalho propÃe o estudo do conversor boost CC-CC de alto ganho de tensÃo baseado na cÃlula de comutaÃÃo de trÃs estados e nas cÃlulas multiplicadoras de tensÃo (mc). Este trabalho investiga um modelo matemÃtico para o citado conversor. A anÃlise proposta à baseada na ferramenta âmodelagem do interruptor PWM para conversores CC-CCâ. O modelo deve ser encontrado por uma simples inspeÃÃo do circuito do conversor. Deve ser possÃvel aplicÃ-lo para realizar diversas anÃlises, como em regime permanente, regime transitÃria e anÃlise de pequenos sinais por meio de um uma abordagem unificada. Considerando um dado nÃmero de cÃlulas multiplicadoras de tensÃo, duas situaÃÃes sÃo analisadas com esta ferramenta: operaÃÃo com uma Ãnica cÃlula multiplicadora de tensÃo (mc=1) e vÃrias cÃlulas multiplicadoras de tensÃo (mc> 1). O mÃtodo proposto à validado por simulaÃÃes e à verificada sua efetividade. AlÃm disso, à analisado neste trabalho o controle modo corrente mÃdia convencional, o qual à aplicado em uma das configuraÃÃes em estudo. O rendimento do conversor e a efetividade do controlador proposto sÃo demonstrados por resultados experimentais para um protÃtipo do laboratÃrio de 1 kW.
The present work proposes the study of the boost converter based on three-state switching cell and voltage multipliers cells (mc). A mathematical model of the aforementioned converter is investigated here. The proposed analysis is based on the tool named âPWM-Switch Modeling of DC-DC Convertersâ. The model must be found by a simple inspection of the converterâs circuit. It is possible to apply such model in order to realize various analyses such as steady-state, transient, and small-signal analysis in a single and same model. Considering the number of voltage multipliers cells (mc), two situations are analyzed: operation with a single multiplier cell (mc=1) and operation with multiple voltage multiplier cells (mc>1).The proposed method was validated through simulations and its effectiveness was verified. In addition to this, conventional average current mode control is also applied to one of the studied configurations. The performance of the converter and the effectiveness of the proposed controller are demonstrated by experimental results obtained from a 1-kW laboratory prototype.

Switched mode power converters are a major source of conducted electromagnetic interference (EMI). The popular technique for mitigation of conducted EMI uses EMI filters. EMI filters may be classified in two types based on the components used: Passive EMI filters and Active EMI filters. Active EMI filters use active components like transistors and opamps for mitigation of conducted EMI. Active EMI filters are a promising alternative to the traditional passive LC filter. The compact active circuit can replace bulky inductors and large capacitors. However, active EMI filters are yet to find wide-scale appeal due to issues pertaining to circuit complexity, component count, cost and reliability. In this thesis the aforementioned active EMI filter issues have been addressed by following a unique design approach. We identified circuits in a switched mode power converter that could play the role of an active EMI filter. We added active EMI filtering functionality to certain start-up, power management, fault protection and sensing circuits by reutilizing their existing circuit components. The challenge lay in ensuring that the original functionality of the circuit is not compromised while it plays the role of an active filter. The merging of two or more functions in a single circuit helped reduce cost, component count, circuit complexity and board space and is the underlying theme of this thesis. This approach led to four new multi-role active EMI filter designs that are proposed in this thesis: 1. Feedback type, series active DM filter as part of an input inrush current limiting circuit, power distribution switch circuit and/or soft latching power switch circuit. 2. Feedforward type, input, shunt active DM filter as part of a high side current sense circuit. 3. Feedback type, output, shunt active DM filter as part of an output under-voltage protection circuit. 4. Feedback type, utility side, shunt DM or CM filter as part of a power line communication module's analog front-end. We claim that our multi role active filters are commercially viable because of the reduction in cost, component count and board space with improvements in reliability and efficiency when compared to equivalent stand alone active filters.

Modelling and simulation are essential ingredients of the analysis and design process in power electronics. It helps a design engineer gain an increased understanding of circuit operation. Accordingly, for a set of specifications given, the designer will choose a particular topology, select component types and values, estimate circuit performance etc. Typically hierarchical modelling, analysis and simulation rather than full detailed simulation of the system provides a crucial insight and understanding. The combination of these insights with hardware prototyping and experiments constitutes a powerful and effective approach to design. Obtaining the mathematical model of the power electronic systems is a major task before any analysis or synthesis or simulation can be performed. There are circuit oriented simulators which uses inbuilt mathematical models for components. Simulation with equation solver needs mathematical models for simulation which are trimmed according to user requirement. There are various methods in the literature to obtain these mathematical models. However, the issues of multi-domain system modelling and causality of the energy variables are not sufficiently addressed. Further, specifically to power converter systems, the issue of switching power models with fixed causality is not addressed. Therefore, our research focuses on obtaining solutions to the above using relatively untouched bond graph method to obtain models for power electronic systems. The power electronic system chosen for the present work is Switched Mode Power Converters (SMPC’s) and in particular PWM DC-DC converters. Bond graph is a labelled and directed graphical representation of physical systems. The basis of bond graph modelling is energy/power flow in a system. As energy or power flow is the underlying principle for bond graph modelling, there is seamless integration across multiple domains. As a consequence, different domains (such as electrical, mechanical, thermal, fluid, magnetic etc.) can be represented in a unified way. The power or the energy flow is represented by a half arrow, which is called the power bond or the energy bond. The causality for each bond is a significant issue that is inherently addressed in bond graph modelling. As every bond involves two power variables, the decision of setting the cause variable and the effect variable is by natural laws. This has a significant bearing in the resulting state equations of the system. Proper assignment of power direction resolves the sign-placing problem when connecting sub-model structures. The causality will dictate whether a specific power variable is a cause or the effect. Using causal bars on either ends of the power bond, graphically indicate the causality for every bond. Once the causality gets assigned, bond graph displays the structure of state space equations explicitly. The first problem we have encountered in modelling power electronic systems with bond graph is power switching. The essential part of any switched power electronic system is a switch. Switching in the power electronic circuits causes change in the structure of the system. This results in change in dynamic equations of the circuit according to position of the switch. We have proposed the switched power junctions (SPJ) to represent switching phenomena in power electronic systems. The switched power junctions are a generalization of the already existing 0-junction and 1-junction concepts of the bond graph element set. The SPJ’s models ideal switching. These elements maintain causality invariance for the whole system for any operational mode of the system. This means that the state vector of the resulting state equation of the system does not change for any operating mode. As SPJs models ideal power switching, the problem of stiff systems and associated numerical stability problems while simulating the system is eliminated. Further, it maintains one to one correspondence with the physical system displaying all the feasible modes of operation at the same time on the same graph. Using these elements, the switched mode power converters (SMPC's) are modelled in bond graph. Bond graph of the converter is the large signal model of the converter. A graphical procedure is proposed that gives the averaged large signal, steady state and small signal ac models. The procedure is suitable for the converters operating in both Continuous Conduction Mode (CCM) and in Discontinuous Conduction Mode (DCM). For modelling in DCM, the concept of virtual switch is used to model the converter using bond graph. Using the proposed method, converters of any complexity can be modelled incorporating all the advantages of bond graph modelling. Magnetic components are essential part of the power electronic systems. Most common parts are the inductor, transformer and coupled inductors which contain both the electric and magnetic domains. Gyrator-Permeance approach is used to model the magnetic components. Gyrator acts as an interface between electric and magnetic domain and capacitor model the permeance of the magnetic circuits. Components like inductor, tapped inductor, transformer, and tapped transformer are modelled. Interleaved converters with coupled inductor, zero ripple phenomena in coupled inductor converters as well as integrated magnetic Cuk converter are also modelled. Modelling of integrated magnetic converters like integrated magnetic forward converter, integrated magnetic boost converter are also explored. To carry out all the simulations of proposed bond graph models, bond graph toolbox is developed using MATLAB/SIMULINK. The MATLAB/SIMULINK is chosen since it is general simulation platform widely available. Therefore all the analysis and simulation can be carried out using facilities available in MATLAB/SIMULINK. Symbolic equation extraction toolbox is also developed which extracts state equations from bond graph model in SIMULINK in symbolic form.

Modelling and simulation are essential ingredients of the analysis and design process in power electronics. It helps a design engineer gain an increased understanding of circuit operation. Accordingly, for a set of specifications given, the designer will choose a particular topology, select component types and values, estimate circuit performance etc. Typically hierarchical modelling, analysis and simulation rather than full detailed simulation of the system provides a crucial insight and understanding. The combination of these insights with hardware prototyping and experiments constitutes a powerful and effective approach to design. Obtaining the mathematical model of the power electronic systems is a major task before any analysis or synthesis or simulation can be performed. There are circuit oriented simulators which uses inbuilt mathematical models for components. Simulation with equation solver needs mathematical models for simulation which are trimmed according to user requirement. There are various methods in the literature to obtain these mathematical models. However, the issues of multi-domain system modelling and causality of the energy variables are not sufficiently addressed. Further, specifically to power converter systems, the issue of switching power models with fixed causality is not addressed. Therefore, our research focuses on obtaining solutions to the above using relatively untouched bond graph method to obtain models for power electronic systems. The power electronic system chosen for the present work is Switched Mode Power Converters (SMPC’s) and in particular PWM DC-DC converters. Bond graph is a labelled and directed graphical representation of physical systems. The basis of bond graph modelling is energy/power flow in a system. As energy or power flow is the underlying principle for bond graph modelling, there is seamless integration across multiple domains. As a consequence, different domains (such as electrical, mechanical, thermal, fluid, magnetic etc.) can be represented in a unified way. The power or the energy flow is represented by a half arrow, which is called the power bond or the energy bond. The causality for each bond is a significant issue that is inherently addressed in bond graph modelling. As every bond involves two power variables, the decision of setting the cause variable and the effect variable is by natural laws. This has a significant bearing in the resulting state equations of the system. Proper assignment of power direction resolves the sign-placing problem when connecting sub-model structures. The causality will dictate whether a specific power variable is a cause or the effect. Using causal bars on either ends of the power bond, graphically indicate the causality for every bond. Once the causality gets assigned, bond graph displays the structure of state space equations explicitly. The first problem we have encountered in modelling power electronic systems with bond graph is power switching. The essential part of any switched power electronic system is a switch. Switching in the power electronic circuits causes change in the structure of the system. This results in change in dynamic equations of the circuit according to position of the switch. We have proposed the switched power junctions (SPJ) to represent switching phenomena in power electronic systems. The switched power junctions are a generalization of the already existing 0-junction and 1-junction concepts of the bond graph element set. The SPJ’s models ideal switching. These elements maintain causality invariance for the whole system for any operational mode of the system. This means that the state vector of the resulting state equation of the system does not change for any operating mode. As SPJs models ideal power switching, the problem of stiff systems and associated numerical stability problems while simulating the system is eliminated. Further, it maintains one to one correspondence with the physical system displaying all the feasible modes of operation at the same time on the same graph. Using these elements, the switched mode power converters (SMPC's) are modelled in bond graph. Bond graph of the converter is the large signal model of the converter. A graphical procedure is proposed that gives the averaged large signal, steady state and small signal ac models. The procedure is suitable for the converters operating in both Continuous Conduction Mode (CCM) and in Discontinuous Conduction Mode (DCM). For modelling in DCM, the concept of virtual switch is used to model the converter using bond graph. Using the proposed method, converters of any complexity can be modelled incorporating all the advantages of bond graph modelling. Magnetic components are essential part of the power electronic systems. Most common parts are the inductor, transformer and coupled inductors which contain both the electric and magnetic domains. Gyrator-Permeance approach is used to model the magnetic components. Gyrator acts as an interface between electric and magnetic domain and capacitor model the permeance of the magnetic circuits. Components like inductor, tapped inductor, transformer, and tapped transformer are modelled. Interleaved converters with coupled inductor, zero ripple phenomena in coupled inductor converters as well as integrated magnetic Cuk converter are also modelled. Modelling of integrated magnetic converters like integrated magnetic forward converter, integrated magnetic boost converter are also explored. To carry out all the simulations of proposed bond graph models, bond graph toolbox is developed using MATLAB/SIMULINK. The MATLAB/SIMULINK is chosen since it is general simulation platform widely available. Therefore all the analysis and simulation can be carried out using facilities available in MATLAB/SIMULINK. Symbolic equation extraction toolbox is also developed which extracts state equations from bond graph model in SIMULINK in symbolic form.

Increasing power density of switch mode power supplies, by increasing their switching frequency has becoming a challenging obstacle for EMI mitigation. The passive EMI suppression technique has always been the primary solution to fulfill the EMC requirement in terms of conducted emission limits. However, the call for stringent power supplies specifications renders the passive techniques less desirable, due to their increasing size and power losses. In other words, the greater the power density of the converter, the bigger the passive filter. Other suppression techniques such as the spread spectrum frequency modulation (SSFM), and soft switching, prove to have less performance and much complex to implement. The active analog EMI filters provide the basic noise suppression technique; however, their performance is dramatically impeded at higher frequency. This solution requires an additional small size passive filter to complete the EMC spectrum for conducted emissions. Digital active filtering techniques offer advantages of flexibility, fewer external components and reduced overall size and power losses as compared to conventional passive filtering techniques. In this thesis DSP-based and FPGA-based EMI control techniques to mitigate the conducted emissions of switch mode power converters are proposed. These techniques are implemented in-lieu of the passive filtering techniques, by keeping equal or better performance. Moreover, these solutions can be configured as a stand-alone or integrated into the converter digital controller algorithm. Finally, the proposed solutions are implemented into three types of power converters, namely, a AC-DC power factor corrected converter, DC-AC micro-inverter for Photovoltaic application, and DC-DC for Electric Vehicle (EV) battery charger. Analytical, simulation and experimental results are provided to verify the proposed solutions.
Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2011-11-07 10:48:49.191

Switched mode power supplies (SMPS) have found wide spread acceptance in all power processing applications. The design demand is moving towards higher power densities. For reduction in size and weight, it is imperative to process the power at a higher switching frequency. High switching frequency requires soft switching techniques to reduce the switching losses. Several families of soft switching converters have emerged in the past two decades. Analysis and modelling methods have been proposed in relation with these topologies. Active clamp converters are the recently introduced soft switching topologies. Steady state analysis and model of these converters have been reported in literature. This thesis presents a unified equivalent circuit oriented model for the family of active clamp converters. Analytical expressions for DC conversion ratio in terms of pole current and throw voltage are derived for all the DC-DC converters with active clamp. The special feature is that, the conversion ratio exhibits a load dependent drop (IRd), where I is the pole current and Rd is the damping resistance. The damping resistance Rd is a mathematical artifact to represent the voltage loss on account of delay in the turn-on of the active switch. There is no energy loss associated with this load dependent drop. This is conveniently expressed as an appropriate lossless resistance in the equivalent circuit model. The proposed equivalent circuit models are valid for both steady-state and dynamic performance. A spread sheet based design is presented for the basic DC-DC converters with active clamp. A prototype design following the spreadsheet is made. The performance of the same is validated and verified by simulation and measurements. Steady state and dynamic results are presented. The stability criterion for the active clamp converters under current programming is investigated. The same is verified through simulation and validated on a current programmed active clamp converter prototype. The active clamp converters suffer from a few disadvantages: Higher VA ratings of switches, load dependent ZVS performance and increased component count. Several soft switching topologies have been reported in literature. Efficiency improvement and increase in switching frequency are obtained to different degrees. This thesis proposes a new family of soft switching converters. This family of converters switch at constant frequency and maintains the advantages of traditional PWM converters. The proposed topology employs an auxiliary circuit to achieve soft switching. The auxiliary circuit consists of a dependent voltage source, an auxiliary switch, a series diode and a set of resonant elements (Inductor and capacitor). The switching transitions of both the active switch and the auxiliary switch are lossless. The novelty in the proposed circuit is the method of generating the dependent source required to enable zero current switching of the auxiliary switch. The dependent source is realized by a coupled winding in the energy storage inductor or tapped from the energy transfer transformer of non-isolated and isolated converters respectively. The proposed topology is applicable to most of the isolated and non-isolated DC-DC converters. The circuit equations governing the sub-intervals of the converter are expressed in terms of pole current and throw voltage. With such a definition, performance results and the design equations are identical for all types of DC-DC converters. Equivalent circuit models are obtained for the whole family of DC-DC converters. The proposed model is valid for steady state and dynamic performance. Analytical expressions of DC conversion ratio for all topologies, in terms of pole current and throw voltage are derived. The special feature is that, the conversion ratio exhibits a load dependent drop (IRd), where I is the pole current and Rd is the damping resistance. The damping resistance Rd is a mathematical artifact to represent the voltage loss on account of delay in the turn-on of the active switch. There is no energy loss associated with this load dependent drop. This is conveniently expressed as an appropriate lossless resistance in the equivalent circuit model. Design guidelines are established for the whole family of proposed converters; the same are validated through prototype converters.

Switched mode power supplies (SMPS) have found wide spread acceptance in all power processing applications. The design demand is moving towards higher power densities. For reduction in size and weight, it is imperative to process the power at a higher switching frequency. High switching frequency requires soft switching techniques to reduce the switching losses. Several families of soft switching converters have emerged in the past two decades. Analysis and modelling methods have been proposed in relation with these topologies. Active clamp converters are the recently introduced soft switching topologies. Steady state analysis and model of these converters have been reported in literature. This thesis presents a unified equivalent circuit oriented model for the family of active clamp converters. Analytical expressions for DC conversion ratio in terms of pole current and throw voltage are derived for all the DC-DC converters with active clamp. The special feature is that, the conversion ratio exhibits a load dependent drop (IRd), where I is the pole current and Rd is the damping resistance. The damping resistance Rd is a mathematical artifact to represent the voltage loss on account of delay in the turn-on of the active switch. There is no energy loss associated with this load dependent drop. This is conveniently expressed as an appropriate lossless resistance in the equivalent circuit model. The proposed equivalent circuit models are valid for both steady-state and dynamic performance. A spread sheet based design is presented for the basic DC-DC converters with active clamp. A prototype design following the spreadsheet is made. The performance of the same is validated and verified by simulation and measurements. Steady state and dynamic results are presented. The stability criterion for the active clamp converters under current programming is investigated. The same is verified through simulation and validated on a current programmed active clamp converter prototype. The active clamp converters suffer from a few disadvantages: Higher VA ratings of switches, load dependent ZVS performance and increased component count. Several soft switching topologies have been reported in literature. Efficiency improvement and increase in switching frequency are obtained to different degrees. This thesis proposes a new family of soft switching converters. This family of converters switch at constant frequency and maintains the advantages of traditional PWM converters. The proposed topology employs an auxiliary circuit to achieve soft switching. The auxiliary circuit consists of a dependent voltage source, an auxiliary switch, a series diode and a set of resonant elements (Inductor and capacitor). The switching transitions of both the active switch and the auxiliary switch are lossless. The novelty in the proposed circuit is the method of generating the dependent source required to enable zero current switching of the auxiliary switch. The dependent source is realized by a coupled winding in the energy storage inductor or tapped from the energy transfer transformer of non-isolated and isolated converters respectively. The proposed topology is applicable to most of the isolated and non-isolated DC-DC converters. The circuit equations governing the sub-intervals of the converter are expressed in terms of pole current and throw voltage. With such a definition, performance results and the design equations are identical for all types of DC-DC converters. Equivalent circuit models are obtained for the whole family of DC-DC converters. The proposed model is valid for steady state and dynamic performance. Analytical expressions of DC conversion ratio for all topologies, in terms of pole current and throw voltage are derived. The special feature is that, the conversion ratio exhibits a load dependent drop (IRd), where I is the pole current and Rd is the damping resistance. The damping resistance Rd is a mathematical artifact to represent the voltage loss on account of delay in the turn-on of the active switch. There is no energy loss associated with this load dependent drop. This is conveniently expressed as an appropriate lossless resistance in the equivalent circuit model. Design guidelines are established for the whole family of proposed converters; the same are validated through prototype converters.

碩士
國立交通大學
電機與控制工程學系
86
This thesis applies the sliding-mode theory to the design of DC- to-DCswitched power converters, which are Buck (with parasitic resistance), Boost and Buck-Boost converters and modeled as bilinear systems. Anew design scheme ofconventional pole- assignment method. Further based on the sliding-modetheory, a reaching-and-sliding region and a stable-sliding region are derived and most importantly the equilibrium point is bounded in theirintersection and shown to be asymptotically stable. In addition,variable structure method in phase-plane is suggested to steer the system into this intersection from the initial condition. One simplesttype of sliding function is also discussed, which only requires the measurement of inductor current. Finally, simulation results demonstratethe success of the proposed sliding-mode technique.