High-frequency dc-dc converters are nowadays widely used in a diversity of power electronic applications. High operating frequencies entail a reduction in size of the passive components, such as inductors, capacitors and power transformers. By operating the converter at higher frequencies with conventional hard-switching topologies, the transistor switching losses increase at both turn-on and turn-off. High-voltage converters in the power range of 1-10MW will therefore have excessive switching losses if the switching frequency is higher than 4 kHz. In order to achieve a high-frequency operation with moderate switching losses a number of soft-switched topologies have been studied in [Dem1]. The favourable DC-DC converter was found to be the Dual-Active Bridge when a bi-directional power flow is demanded. Additionally, the Single-Active Bridge (SAB) topology was introduced for the first time. In this thesis the two topologies are thoroughly studied. The dynamic small-signal models are presented and the dynamic behaviour of the converters is discussed in deep. Different control strategies are presented concerning the two converters and the advantages and the disadvantages of the different control strategies are stated. Critical issues as efficiency and stability are presented separately for the two converters. / QC 20101005

In low power, battery-operated, portable applications, like cell phones, PDAs, digital cameras, etc., miniaturization at a low cost is a prominent driving factor behind product development and marketing efforts. As such, power supplies in portable applications must not only conform and adapt to their highly integrated on-chip and in-package environments but also, more intrinsically, respond quickly to fast load dumps to achieve and maintain high accuracy. The frequency-compensation network, however, limits speed and regulation performance because, in catering to all combinations of the output capacitor, its equivalent series resistance Resr, and the power inductor resulting from tolerance and modal design targets, it must compensate the worst-case condition and therefore restrain the performance of all other possible scenarios. Sigma-delta control, which addresses this issue in buck converters by easing its compensation requirements and offering one-cycle transient response, has not been able to simultaneously achieve high bandwidth, high accuracy, and wide LC-Resr compliance in boost (step-up) converters. This thesis investigates and presents techniques to achieve sigma-delta control in boost converters by essentially using explicit current and voltage control loops. The proposed techniques are developed conceptually and analytical expressions for stability range and transient response are derived. The proposed concepts are validated and quantified through PCB and IC prototypes to yield 1.41 to 6 times faster transient response than the state of the art in current-mode boost supplies, and this without any compromise in LC-Resr compliance range.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A distributed power supply composed of multiple DC-DC converters connected in parallel offers several advantages in comparison to a centralized solution. Among these benefits are the following: redundancy, system modularity, increased reliability, improved thermal ow on the system and reduction in the physical size of the units. Its main purpose is to evenly share the output current between the converters. In practice, this specification is rarely achieved without the use of a specific control strategy for sharing, since each converter produces output dependent on the tolerances of the components and the line impedance that connects the unit to the load bus. This imbalance in the shared current can cause excessive stress on the units operating outside of their specifications, increasing their chances of failure. Also, it is desirable that any points of failure are minimized or eliminated by adopting a decentralized control strategy, minimizing connections between units. In this work, the generalized model of output current for a i -th converter from a source with n converters connected in parallel is obtained. To obtain this model, each converter present in the system is modeled as a controlled voltage source, connected to the load bus through an individual line resistance. As the main contribution, two strategies to control current sharing between converters are proposed, based on parallelism without communication between modules, specifically the droop control. To validate the design, the simulation results for a power supply containing three converters in parallel applied to a LED street lamp fixture are shown and analyzed. At the end of this document, the conclusions and suggestions for future work involving the subject are developed. / Uma fonte distribuída de potência composta por vários conversores CC-CC conectados em paralelo oferece diversas vantagens em comparação a uma solução centralizada. Entre esses benefícios, destacam-se os seguintes: redund^ancia, modularidade do sistema, aumento da confiabilidade, melhoria no uxo térmico do sistema e redução no tamanho físico das unidades. Seu principal objetivo é compartilhar uniformemente a corrente de saída entre os conversores. Na prática, esta especificação é raramente atingida sem o emprego de uma estratégia de controle específica para o compartilhamento, visto que cada conversor produz saída dependente das tolerâncias de seus componentes e da impedância de linha que o conecta ao barramento de carga. Este desequilíbrio nas correntes compartilhadas pode ocasionar estresse excessivo nas unidades operando fora de suas especificações, aumentando suas chances de falha. Ainda, é desejável que quaisquer pontos de falha sejam minimizados ou eliminados através da adoção de uma estratégia de controle descentralizada, minimizando conexões entre os conversores. Neste trabalho, o modelo generalizado de corrente para um i -ésimo conversor constituinte de uma fonte com n conversores conectados em paralelo é obtido. Para obtenção deste modelo, modelou-se cada conversor presente no sistema como uma fonte de tens~ao controlada, conectado ao barramento de carga através de uma resistência de linha individual. Como principal contribuição, são apresentadas duas estratégias de controle para compartilhamento de corrente entre conversores, baseados no paralelismo sem comunicação entre módulos, mais especificamente o controle por decaimento. Para validar o projeto, são mostrados e analisados os resultados de simulação para uma fonte de potência contendo três conversores em paralelo aplicados a uma lâmpada de LEDs para iluminação pública. No final deste documento, as conclusões e sugestões para futuros trabalhos envolvendo o tema são elaboradas.

abstract: High-efficiency DC-DC converters make up one of the important blocks of state-of-the-art power supplies. The trend toward high level of transistor integration has caused load current demands to grow significantly. Supplying high output current and minimizing output current ripple has been a driving force behind the evolution of Multi-phase topologies. Ability to supply large output current with improved efficiency, reduction in the size of filter components, improved transient response make multi-phase topologies a preferred choice for low voltage-high current applications. Current sensing capability inside a system is much sought after for applications which include Peak-current mode control, Current limiting, Overload protection. Current sensing is extremely important for current sharing in Multi-phase topologies. Existing approaches such as Series resistor, SenseFET, inductor DCR based current sensing are simple but their drawbacks such low efficiency, low accuracy, limited bandwidth demand a novel current sensing scheme. This research presents a systematic design procedure of a 5V - 1.8V, 8A 4-Phase Buck regulator with a novel current sensing scheme based on replication of the inductor current. The proposed solution consists of detailed system modeling in PLECS which includes modification of the peak current mode model to accommodate the new current sensing element, derivation of power-stage and Plant transfer functions, Controller design. The proposed model has been verified through PLECS simulations and compared with a transistor-level implementation of the system. The time-domain parameters such as overshoot and settling-time simulated through transistor-level implementation is in close agreement with the results obtained from the PLECS model. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2017

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Neste trabalho à apresentado o estudo, modelagem e projeto de uma nova topologia de conversor CC-CC, o Conversor Buck QuadrÃtico CC-CC nÃo isolado (QBC). Inicialmente, foi realizada a anÃlise qualitativa e quantitativa da topologia proposta para operaÃÃo em modo de conduÃÃo contÃnua (MCC), verificando-se as etapas de operaÃÃo e obtendo-se as relaÃÃes de tensÃo e corrente para dimensionar os componentes de projeto do conversor, tambÃm foi realizada a modelagem do sistema atravÃs da representaÃÃo no espaÃo de estados. Em seguida, a fim de validar a topologia proposta, utilizou-se simulaÃÃo via PSpice. ApÃs essa etapa, iniciou-se a construÃÃo de um protÃtipo com 500 W de potÃncia total de saÃda, operando em 20 kHz. Os resultados experimentais obtidos confirmam que a topologia proposta pode ser utilizada em atividades prÃticas, como por exemplo, para o carregamento de baterias. / In this paper is presented the study, modeling and design of a new DC-DC converter topology, the Converter Quadratic Buck DC-DC non-isolated (QBC). Initially, was made the qualitative and quantitative analysis of the proposed topology of continuous conduction mode operation (MCC), the steps of operation and thus the relationship of voltage and current to size the components converter project, was also held the system modeling through representation on the State space. Then, in order to validate the proposed topology, was used simulation via PSpice. After this step, began the construction of a prototype with 500 W total power output, operating at 20 kHz. The experimental results obtained confirm that the proposed topology can be used in practical activities, for example, for battery charging.

Technology advancements enable and encourage higher system electrifications in various applications. More electrified applications need more capable and higher performing sources of energy in terms of power delivery, power regeneration, and energy capacity. For example, in electric, hybrid electric, and plug-in hybrid electric vehicle applications (EVs, HEVs, and PHEVs), the power and energy ratings of the vehicle energy storage system (ESS) have a direct impact on the vehicle performance. Many researchers investigated and studied various aspects of hybrid energy storage systems (HESS) wherein multiple ESSs are combined together to share system loads, increase ESS capabilities, and cycle life. Various configurations and their application specific topologies were also proposed by other researchers; the potential of HESS has been proven to be very promising. In this research, the goal is to present the theory of a HESS configuration that has not been discovered thus far. This HESS configuration is called a series-parallel reconfigurable HESS (SPR-HESS) since it is capable of recombining multiple storage systems into different series, parallel, or series-parallel configurations, via power electronic converters, to accommodate different operation modes and load requirements. Simulations, as well as experimental verifications, are presented in this thesis. / Thesis / Doctor of Philosophy (PhD)

Cette thèse traite de la commande hiérarchique de réseaux à courant continu multi-terminaux à haute tension (MT-HVDC) intégrant des sources d'énergie renouvelables à grande échelle. Le schéma de contrôle proposé est composé de quatre ‘couches’ : le contrôle local où se trouvent les convertisseurs de puissance, avec une échelle de temps de l’ordre de la milliseconde ; le contrôle primaire qui est décentralisé et appliqué à plusieurs terminaux avec une échelle du temps de l’ordre de la seconde ; un niveau de commande où la communication est prise en compte et où l’approche de Modèle du Commande Prédictive (MPC) assure la planification de la tension et de la puissance à leur état d'équilibre, pour l'ensemble du système; enfin, le contrôleur de niveau supérieur, qui est principalement basé sur les techniques d'optimisation, où les aspects économiques sont pris en compte (il s’agit du réglage dit tertiaire).Au niveau des convertisseurs, un accent particulier est mis sur les convertisseurs bidirectionnels DC/DC. Dans cette thèse, trois topologies différentes sont étudiées en profondeur: deux phases Dual Active Bridge (DAB), trois phases DAB, et l’utilisation de la technologie Modular Multilevel converter (MMC) comme convertisseur DC/DC. Pour chaque topologie, une commande non-linéaire spécifique est discutée. D’autre part une nouvelle fonction pour le convertisseur DC/DC est étudiée. Il s’agit de son utilisation comme disjoncteur à courant continu (DC-CB). En ce qui concerne le contrôle primaire, qui permet de maintenir le niveau de tension continue dans le réseau, nous avons étudié trois philosophies de contrôle: celle de maître/esclave, celui du contrôle « voltage margin control » et celle de la commande du statisme (droop control). Enfin, nous avons choisi d'utiliser le droop control, entre autres, parce que la communication entre les nœuds n’est pas nécessaire. Concernant la commande secondaire, son principal objectif est de planifier le transfert de puissance entre les nœuds du réseau, qui fournissent la tension et la puissance de référence aux contrôleurs locaux et primaires, même lorsque des perturbations apparaissent. Dans cette partie, nous avons proposé une nouvelle approche pour résoudre les problèmes de flux de puissance (équations non-linéaires) basée sur le théorème du point fixe de l’application contractive. Ceci permet d'utiliser plus d'un slack bus, contrairement à l’approche classique basée sur la méthode de Newton-Raphson. Par ailleurs, le réglage secondaire joue un rôle très important dans les applications pratiques, en particulier lorsque les sources d'énergie renouvelables (variables dans le temps). Dans de tels cas, il est intéressant de considérer des dispositifs de stockage afin d'améliorer la stabilité de tout le système. Il est également possible d'envisager différents types de prévisions (météo, charge, ..) basées sur la gestion des réserves de stockage. Toutes ces caractéristiques ont suggéré l'utilisation d'une approche MPC. Dans ce contexte, plusieurs critères d'optimisation ont été considérés, en particulier la minimisation des pertes de transmission ou des congestions dans le réseau.La tâche principale de réglage tertiaire est de d'atteindre l'optimisation économique de l'ensemble du réseau. Dans cette thèse, nous avons pu maximiser le profit économique du système en agissant sur le marché réel, et en optimisant l'utilisation des périphériques de stockage. Dans le but de mettre en œuvre la philosophie de contrôle hiérarchique présentée dans cette thèse, nous avons construit un banc d'essai expérimental. Cette plate-forme dispose de quatre terminaux reliés entre eux par l'intermédiaire d'un réseau à courant continu, et connectés au réseau principal de courant alternatif. Ce réseau DC peut fonctionner à un maximum de 400 V, et avec une courant maximal de 15 A. / This thesis focuses on the hierarchical control for a multi-terminal high voltage direct current (MT-HVDC) grid suitable for the integration of large scale renewable energy sources. The proposed control scheme is composed of 4 layers, from the low local control at the power converters in the time scale of units of ms; through distributed droop control (primary control) applied in several terminals in the scale of unit of seconds; and then to communication based Model Predictive Control (MPC) that assures the load flow and the steady state voltage/power plan for the whole system, manage large scale storage and include weather forecast (secondary control); finally reaching the higher level controller that is mostly based on optimization techniques, where economic aspects are considered in the same time as longer timespan weather forecast (tertiary control).Concerning the converters' level, special emphasis is placed on DC/DC bidirectional converters. In this thesis, three different topologies are studied in depth: two phases dual active bridge (DAB), the three phases DAB, and the use of the Modular Multilevel Converter (MMC) technology as DC/DC converter. For each topology a specific non-linear control is presented and discussed. In addition, the DC/DC converter can provide other important services as its use as a direct current circuit breaker (DC-CB). Several operation strategies are studied for these topologies used as DC-CB.With respect to primary control, which is the responsible to maintain the DC voltage control of the grid, we have studied several control philosophies: master/slave, voltage margin control and droop control. Finally we have chosen to use droop control, among other reasons, because the communication between nodes is not required. Relative to the secondary control, its main goal is to schedule power transfer between the network nodes providing voltage and power references to local and primary controllers, providing steady state response to disturbances and managing power reserves. In this part we have proposed a new approach to solve the power flow problem (non-linear equations) based on the contraction mapping theorem, which gives the possibility to use more than one bus for the power balance (slack bus) instead of the classic approach based on the Newton-Raphson method. Secondary control plays a very important role in practical applications, in particular when including time varying power sources, as renewable ones. In such cases, it is interesting to consider storage devices in order to improve the stability and the efficiency of the whole system. Due to the sample time of secondary control is on the order of minutes, it is also possible to consider different kinds of forecast (weather, load,..) and to achieve additional control objectives, based on managing storage reserves. All these characteristics encourage the use of a model predictive control (MPC) approach to design this task. In this context, several possibilities of optimization objective were considered, like to minimize transmission losses or to avoid power network congestions.The main task of tertiary control is to manage the load flow of the whole HVDC grid in order to achieve economical optimization. This control level provides power references to the secondary controller. In this thesis we were able to maximize the economic profit of the system by acting on the spot market, and by optimizing the use of storage devices. In this level it is again used the MPC approach.With the aim of implementing the hierarchical control philosophy explained in this thesis, we have built an experimental test bench. This platform has 4 terminals interconnected via a DC grid, and connected to the main AC grid through VSC power converters. This DC grid can work at a maximum of 400 V, and with a maximum allowed current of 15 A.

Le travail de recherche concrétisé par ce mémoire de thèse se trouve à l’intersection de deux domaines importants, la commande robuste des systèmes linéaires (LTI, LPV, en commutation) à temps discret affectés par des perturbations permanentes bornées et des contraintes et les ensembles invariants ellipsoïdaux maximal ou minimal. La première partie de ce mémoire se focalise sur l’analyse de la stabilité entrée-état (en anglais ISS) du système par rapport à une perturbation bornée et le calcul des ensembles invariants ellipsoïdaux minimal ou maximal (ou sous forme d’ellipsoïdes tronqués) satisfaisant les contraintes. La deuxième partie envisage la synthèse d’une commande par retour d’état ISS stable et robuste vis-à-vis de perturbations bornées, garantissant l’ellipsoïde invariant maximal satisfaisant les contraintes ; puis la synthèse d’une loi decommande par retour d’état et observateur ISS stable vis-à-vis de perturbations bornées, garantissant une certaine performance ; enfin la synthèse d’un paramètre de Youla afin de garantir la projection maximale sur le sous-espace de l’état initial. La projection obtenue possède alors un volume plus grand que celui obtenu sans le paramètre de Youla d’où une amélioration en termes de robustesse. Une dernière étape vise à obtenirun compromis entre la robustesse et la performance en utilisant des critères basés sur le placement de pôles ou sur la vitesse de décroissance de la fonction de Lyapunov. Tous les résultats théoriques obtenus sont exprimés sous forme d’inégalités matricielles et sont validés en simulation et de façon expérimentale dans le cadre de la commande d’un convertisseur de puissance. / The research concretized in this memory is located at the intersection of two important fields, the robust control of discrete-time linear systems (LTI, LPV, switched) affected by bounded disturbances and constraints and the ellipsoidal invariant sets theory.The first part of this memory focuses on the analysis of input-to-state stability (ISS) over a bounded perturbation and the computation of the maximal or minimal invariant ellipsoidal (or truncated ellipsoidal) set satisfying the constraints. The second part is considering the synthesis of a control state feedback law ISS stable and robust over bounded disturbances, ensuring the maximal ellipsoidal invariant set satisfying the constraints, then the synthesis of an observer-based control law ISS stable over bounded disturbances,ensuring a certain performance, and finally the design of a Youla parameter guaranteeing the maximal ellipsoidal projection on the initial state subspace. The resulting projection has a volume greater than the one obtained without the Youla parameter resulting an improvement in terms of robustness. A final step is to obtain a compromise between robustness and performance using criteria based on poles placement or on theLyapunov function decreasing rate. The theoretical results are expressed as matrix inequalities and are validated in simulation and and experimentally on a Buck DC-DC converter.

L'utilisation des convertisseurs de puissance pour des applications de la vie quotidienne devient de plus en plus importante. Les applications technologiques actuelles demandent simultanément un haut niveau de précision et de performance, ainsi les convertisseurs DC-DC ont un rôle très important dans les systèmes nécessitant la conversion et l’adaptation du niveau d'énergie. Nous nous intéressons dans le cadre des travaux de cette thèse à une analyse des approches de modélisation et de synthèse de loi de commande permettant d’assurer la stabilité et un certain niveau de performances dans l’ensemble du domaine de fonctionnement défini par un cahier des charges tout en prenant en compte la problématique de leur application dans un environnement industriel. L'objectif de nos travaux de recherche est donc de proposer des lois de commandes dont la synthèse est fondée sur une approche formalisé {modélisation + commande} en vue d’obtenir des lois de commande adaptées au point de fonctionnement. Les principes exploités sont fondés sur la commande et l’observation par modes glissants d’une part, et sur la théorie de passivité pour la synthèse des lois de commande, complétées par un couple {observateur d’état + estimateur de charge} dont la synthèse est fondée sur l’exploitation des principes d'immersion et invariance, d’autre part. Le souci de la validation expérimentale et de l’implantation des structures de commande avec du matériel disponible industriellement a été en permanence un fil conducteur. Pour démontrer l’efficacité des méthodes proposées, leur application expérimentale a été effectuée sur un convertisseur de type SEPIC. Ce convertisseur présente plusieurs avantages par rapport à autres convertisseurs. Cependant, il reste peu exploité, en dépit de ces avantages, en raison des difficultés pour obtenir des lois commande performantes permettant la stabilisation de sa tension de sortie dans tout l’ensemble du domaine de fonctionnement. / The use of power converters for real life applications is continuously increasing. Technological requirements include high precision levels and very good performances at the same time, where DC-DC converters have always played an important role in energy conversion-based systems. Our interest, throughout this thesis, is to analyze modeling and control law synthesis approaches in order to provide efficient control laws that are stable within the operating range, in response to certain specifications and also taking into account the problem of being industrially applicable. The aim of our research is hence to propose control law synthesis based on formalized {modeling + control} approaches, and adaptable to the operating point change. The exploited principles deal with Sliding Mode Observation and Control on one hand, and with the Passivity theory for control law synthesis coupled with the Immersion and Invariance principle for synthesizing {observers + load estimators} on the other. Also, the ease of implementing and validating the control law structures with common hardware available in the industry has always been a main issue throughout our study. In the view of illustrating the efficacy of the proposed methods, their experimental validation has been carried out on the SEPIC. This type of converter has many advantages compared to other converters. However, despite its advantages, it is still not well-exploited due to the difficulty in obtaining control laws capable of stabilizing its output voltage within a wide operating range.

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.