AC/DC Buck converters have been used widely in many applications from cell phones to vehicle battery chargers. Due to their importance many researchers have been studying their behavior to improve their efficiency and reduce their size and/or cost. One of the most common defects of these converters, whether they are used for high power or low power applications, is the unwanted ripples in the input voltage across the input stage. It is believed that these ripples are caused by the interaction between the converter itself or its controller with the rectifier required to change the AC input into DC followed by an input filter. Many strategies have been suggested to tackle this problem. A new strategy to improve the controller of that converter was suggested by M. Lenells [1] and it was based on a Hamiltonian model for the 3-phase AC/DC converter together with its rectifier. As a first step, we simulated this model for a single-phase DC/DC buck converter only using the so-called S-Functions in MATLAB/SIMULINK. Then we could find a control law that would reduce the ripples in the input voltage and keep the output voltage constant simultaneously. In this report, we present this model and its simulation to pave the way for the control and simulation of the 3-phase AC/DC converter.

En raison des progrès réalisés dans l’architecture et le contrôle des convertisseurs statique, beaucoup d’applications électrotechniques se comportent comme des dispositifs fonctionnant à puissance constante. Cette propriété conduit à modéliser ces systèmes autour d’un point de fonctionnement par des résistances négatives. Se pose alors un problème de stabilité quand ils sont connectés à des sources d’énergie munies ou non d’une commande. Dans une première partie de la thèse, les différents outils basés sur des spécifications d’impédance sont introduits et appliqués à l’étude des systèmes à puissance distribuée. Deux exemples électrotechniques sont traités ; le premier étudie l’association filtre d’entrée hacheur DC/DC. La seconde traite l’association filtre d’entrée actionneur électromécanique. Dans une second partie de la thèse, pour assurer la stabilité de deux dispositifs électrotechnique mis en cascade, l’auteur propose d’utiliser une commande globale non linéaire permettant d’assurer à la fois la stabilité du système tout en minimisant la taille de ses éléments passifs. Pour assurer un contrôle découplé des différentes sorties ainsi que la stabilité du système, l’auteur utilise une linéarisation de type entrée/sortie. Un régulateur à structure variable de type glissant assure les propriétés de robustesse vis-à-vis des variations paramétriques du système. L’architecture de commande proposée permet alors une diminution significative des éléments de stockage d’énergie dans le système / Because of the high efficiency of the power electronic converters, ideal regulation of their outputs makes the converter appears as a constant power load seen by its front end power stage. So they can be modeled as a negative resistance around an operating point. As a result, when such a converter is connected to a controlled or uncontrolled power source subsystem, the risk of instability has to be unpacked. To study the stability issue taken by such a system, we have detailed in a first step how to prove the local stability of Distributed Power System. The impedance criterions which are used to analysis the stability of cascaded systems are described. These criterions are applied in the case of two power electronics applications. The first one corresponds to a DC/DC switching converter with its input filter. The second one deals with the stability issues of a system constituted by an input filter and an inverter-motor drive system. In the second part of the thesis, a non linear global control of a cascaded power electronic system is investigated in order to ensure the stability of the whole system with a minimization of its passive components. To uncouple the control of all the outputs variables and ensure the system stability, an I/O linearization technique is proposed. Thanks to the use of a sliding controller, the resulting control architecture is robust as regard to parameters variations and allows a significant diminution of the passive component size

Dans le contexte du concept de l’avion «plus électrique », l’électricité prend une part croissante dans les systèmes embarqués aéronautiques. Ainsi, de nombreuses évolutions ont eu lieu, concernant les réseaux de bord, notamment l’architecture du réseau qui est devenue de plus en plus complexe, intégrant de nombreux équipements de différentes natures ; ceci entraîne de multiples questions relatives à la qualité et la stabilité du réseau. C’est dans ce contexte que s’inscrivent ces travaux de thèse, qui aboutissent d’une part à la mise en œuvre de méthodes d’analyse de la stabilité et de la qualité du réseau aéronautique embarqué et d’autre part à l’analyse de couplage entre plusieurs équipements connectés sur un seul réseau. Les études menées au cours de ces travaux reposent sur l’utilisation des expressions analytiques représentant le comportement fréquentiel de réseaux continus. Une méthode de calcul basée sur les lois de la physique a été développée et validée par des approches de simulation et d’expérimentation. Par ailleurs, en absence d’un modèle analytique, nous choisissons de déterminer l'expression littérale du modèle équivalent du réseau à partir de l'identification des données issues de l’approche expérimentale en se basant sur des algorithmes d'optimisation. Ces modèles analytiques sont associés aux critères mathématiques de stabilité (Routh-Hurwitz, MiddleBrook), et aux contraintes de qualité imposées par les standards aéronautiques, dans le but de dimensionner les éléments de filtrage à placer entre le réseau et l’équipement. Le calcul des composants assurant le filtrage repose sur la recherche d’une solution optimale : nous introduisons les algorithmes d’optimisation utilisés en première étape, et nous proposons par la suite une formulation de la procédure de calcul des paramètres du filtre pour une meilleure illustration des résultats intéressants pour un concepteur de réseau. Enfin, nous clôturons ce travail par une analyse des couplages entre plusieurs équipements connectés sur un réseau continu et nous concluons par une approche expérimentale afin d’appuyer les résultats théoriques. / In the concept of the "more electric" aircraft, power takes an increasing proportion in aeronautic embedded systems. So many changes have occurred on board networks, including the network architecture that has become more and more complex, integrating many different types of equipment that causes quality and stability issues on the network. In this context that this thesis is inscribed, firstly it leads to the implementation of methods for stability and quality analyzing of the embedded network and secondly to coupling analysis of several devices connected to a single network. Studies conducted in this work are based on analytical expressions representing the frequency behavior of networks. A compute based on fundamental physical laws has been developed and validated by simulation and experimental approaches. Moreover, in the absence of an analytical model, we choose to determine the literal expression of the equivalent model of the network by identifying data, come from the experimental approach, using optimization algorithms. These analytical models are associated with mathematical criteria: Routh-Hurwitz, Middlebrook, and quality constraints imposed by aeronautic standards, in order to size the elements of the filter cell placed between the voltage source and the equipment to ensure the stability and quality of the entire system. The sizing of cell parameters based on optimal search by means of optimization algorithms in the first step, and then we propose a formulation of the calculation procedure of the filter parameters to illustrate some interesting results for designer’s network. Finally, we close this work with a coupling analysis of several devices connected to a single DC bus and we conclude by an experimental approach to support the theoretical results.

The dissertation presents a generalized average-current-mode control technique (GACMC), which is an extension of the average-current-mode control (ACMC) for single-phase ac-dc boost converters with power factor correction (PFC). Traditional ACMC is generalized in a sense that it offers improved performance in the form of significant reduction of the current control loop bandwidth requirement for a given line frequency in unidirectional and bidirectional boost PFC converters, and additional functionality in the form of reactive power control capability in bidirectional converters. These features allow using a relatively low switching frequency and slow-switching power devices such as insulated-gate bipolar transistors (IGBTs) in boost PFC converters, including those designed for higher ac line frequencies such as in aircraft power systems (360–800 Hz). In bidirectional boost PFC converters, including multilevel topologies, the GACMC offers a capability to supply a prescribed amount of reactive power (with leading or lagging current) independently of the dc load power, which allows the converter to be used as a static reactive power compensator in the power system. A closed-loop dynamic model for the current control loop of the boost PFC converter with the ACMC has been developed. The model explains the structure of the converter input admittance, the current phase lead phenomenon, and lays the groundwork for development of the GACMC. The leading phase admittance cancellation (LPAC) principle has been proposed to completely eliminate the current phase lead phenomenon and, consequently, the zero-crossing distortion in unidirectional converters. The LPAC technique has been adapted for active compensation of the input filter capacitor current in bidirectional boost PFC converters. The dynamic model of the current control loop for bidirectional boost PFC converters was augmented to include a reactive power controller. The proposed control strategy enables the converter to process reactive power and, thus, be used as a reactive power compensator, independently of the converter operation as an ac-dc converter. Multiple realizations of the reactive power controller have been identified and examined in a systematic way, along with their merits and limitations, including susceptibility to the ac line noise. Frequency response characteristics of reactive elements emulated by means of these realizations have been described. Theoretical principles and practical solutions developed in this dissertation have been experimentally verified using unidirectional and bidirectional converter prototypes. Experimental results demonstrated validity of the theory and proposed practical implementations of the GACMC. / Ph. D.

The study, description, design and implementation of selected blocks of multiband shortwave radio station are dealt with in the thesis. Focus is placed on the concept of multiband shortwave radio stations, with an emphasis on high frequency and intermediate frequency circuits. The first chapter is devoted to description of the transceiver block diagram which is designed as superheterodyne. The design of bandpass input filters, intermediate frequency crystal filters and output filters is described. Simulation results and the measured characteristics of the implemented functional blocks are presented. Furthermore, the amplifier circuits which maintain impedance matching of individual blocks are discussed. SSB signal generation in the transmitter part of radio station and final stage power amplification are depicted.