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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Robust Extremum Seeking Control Design

Odoemene, Daniel Okezuo Tarasius January 2022 (has links)
No description available.
52

Contribution au Dimensionnement et à la Commande d’un Générateur de type Cascade de Machines Asynchrones à Double Alimentation / Contribution to the Sizing and Control of the Cascaded Doubly Fed Induction Generator

El achkar, Maria 12 December 2016 (has links)
Le travail présenté dans cette thèse est une contribution au dimensionnement et à la commande d’un générateur de type Cascade de Machines Asynchrones à Double Alimentation. Le modèle de la machine pour les simulations est basé sur une représentation modulaire qui découle du modèle de Park de deux machines asynchrones doublement alimentées distinctes, en respectant deux systèmes de référence. Le modèle dynamique est ensuite étendu pour décrire la machine dans un repère unifié. Cette représentation est cruciale pour le dimensionnement de la machine et la synthèse de la commande. Le domaine de fonctionnement de la cascade en régime permanent est exploré. Une méthode analytique générique est proposée pour établir les plages de puissances active-réactive. Les courbes limites sont définies par rapport aux grandeurs nominales de la machine. L’étude prend en compte l’effet de saturation du circuit magnétique. Il est prouvé que la capacité en puissance de la machine est déterminée par les valeurs maximales des courants statoriques et peut être soumise à plusieurs limitations. L’approche analytique est testée et validée par des mesures expérimentales. Deux cas sont considérés pour la commande de la cascade : un générateur raccordé au réseau et un générateur autonome. Pour la connexion au réseau l’application visée est les éoliennes de grande puissance. Une nouvelle méthode pour l’extraction de la puissance maximale d’une éolienne à vitesse variable est proposée. Le système est contrôlé dans le but de fournir une puissance maximale quasi-constante indépendamment des fluctuations du vent. En plus de l’optimisation de la puissance, le facteur de puissance est également ajusté selon les normes de raccordement standard imposées par les services système, et les limites de fonctionnement de l’unité intégrée. Une commande vectorielle sans capteur de tension, basée sur une orientation suivant un flux virtuel, est appliquée pour la régulation découplée des puissances active et réactive. Pour le fonctionnement en mode isolé, l’application visée est la génération électrique pour système avionique embarqué. Deux réseaux de distribution sont traités : réseau AC à fréquence fixe et réseau DC. Dans les deux cas, la commande est élaborée dans le but de maintenir une tension de sortie constante. Le fonctionnement de la cascade alimentant une charge triphasée déséquilibrée est également étudié. Des schémas de contrôle servant à la compensation du déséquilibre des tensions statoriques sont développés. Deux méthodes de compensation sont proposées : l’une basée sur le principe de deux repères tournants et l’autre sur un correcteur répétitif. Les approches présentées sont validées par simulation avec Matlab/Simulink et par expérimentation. / This thesis is a contribution to the power sizing and the control of a Cascaded Doubly Fed Induction Generator (CDFIG). The machine model for simulation is based on a modular representation, derived from the Park model of two distinct Doubly Fed Induction Machines expressed in their own reference frames. The dynamic model of the cascaded machine is then extended to be described in a unified reference frame. This representation is convenient for the sizing of the machine and for the design of the controller. The steady state power operating margins of the cascaded machine are investigated. A generic analytic method is suggested to derive the active-reactive power domain. The limit curves are defined in terms of the rated quantities of the machine. The study takes into account the magnetic circuit saturation effect. It is proven that the power capability of the machine is determined by the stator current maximum values and is subject to several limitations. The analytical approach is tested and validated by experimental measurements. The CDFIG is controlled in grid-connected and standalone operation modes. In grid-connected application, the attention is paid to high power wind generation systems. A new maximum power tracking of a variable speed wind turbine is suggested. The generating plant is carried to provide a quasi-constant maximum power regardless wind fluctuations. In addition to active power optimization the power factor is adjusted according to the grid code requirements and the operating domain of the integrated unit. A virtual flux oriented vector control is applied for the decoupled regulation of active and reactive powers, leading to grid voltage sensorless operation. In standalone operating mode, the study treats in particular the embedded aircraft power system generation. Two distribution networks are considered: constant frequency AC network and DC network. In both cases, the control aims to maintain a constant output voltage. The operation of the CDFIG supplying unbalanced three-phase load is further explored. Control schemes to cope with unbalanced stator voltage conditions are developed. Two compensation methods are elaborated: the first dealing with dual rotating frames and the second is based on repetitive controller. Simulations with Matlab/Simulink software and experiments validate the control approaches.
53

Contribution to adaptative sliding mode, fault tolerant control and control allocation of wind turbine system / Contribution à la commande par modes glissants adaptative et tolérantes aux défauts : Application au système éolien

Liu, Xinyi 25 November 2016 (has links)
Les principaux défis pour le déploiement de systèmes de conversion de l'énergie éolienne est de maximiser la puissance électrique produite, malgré les variations des conditions météorologiques, tout en minimisant les coûts de fabrication et de maintenance du système. L'efficacité de la turbine éolienne est fortement dépendante des perturbations de l'environnement et des paramètres variables du système, tels que la vitesse du vent et l'angle de tangage. Les incertitudes sur le système sont difficiles à modéliser avec précision alors qu'ils affectent sa stabilité.Afin d'assurer un état de fonctionnement optimal, malgré les perturbations, le commande adaptative peut jouer un rôle déterminant. D'autre part, la synthèse de commandes tolérantes aux défauts, capables de maintenir les éoliennes connectées au réseau après la survenance de certains défauts est indispensable pour le bon fonctionnement du réseau. Le travail de cette thèse porte sur la mise en place de lois de commande adaptatives et tolérantes aux défauts appliqués aux systèmes de conversion de l'énergie éolienne. Après un état de l'art, les contributions de la thèse sont :Dans la première partie de la thèse, un modèle incertain non linéaire du système de conversion d'énergie éolienne avec un générateur à induction à double alimentation est proposé. Une nouvelles approches de commande adaptative par mode glissant est synthétisée et ensuite appliquée pour optimiser l'énergie issue de l'éolienne.Dans la deuxième partie, une nouvelle commande par modes glissants tolérante aux défauts et basée sur les modes glissants intégrales est présentée. Puis, cette méthode est appliquée afin de forcer la vitesse de la turbine éolienne à sa valeur optimale en prenant en compte des défauts qui surviennent sur l'actionneur. / The main challenges for the deployment of wind energy conversion systems (WECS) are to maximize the amount of good quality electrical power extracted from wind energy over a significantly wide range of weather conditions and minimize both manufacturing and maintenance costs. Wind turbine's efficiency is highly dependent on environmental disturbances and varying parameters for operating conditions, such as wind speed, pitch angle, tip-speed ratio, sensitive resistor and inductance. Uncertainties on the system are hard to model exactly while it affects the stability of the system. In order to ensure an optimal operating condition, with unknown perturbations, adaptive control can play an important role. On the other hand, a Fault Tolerant Control (FTC) with control allocation that is able to maintain the WECS connected after the occurrence of certain faults can avoid major economic losses. The thesis work concerns the establishment of an adaptive control and fault diagnosis and tolerant control of WECS. After a literature review, the contributions of the thesis are:In the first part of the thesis, a nonlinear uncertain model of the wind energy conversion system with a doubly fed induction generator (DFIG) is proposed. A novel Lyapunov-based adaptive Sliding Mode (HOSM) controller is designed to optimize the generated power.In the second part, a new output integral sliding mode methodology for fault tolerant control with control allocation of linear time varying systems is presented. Then, this methodology has been applied in order to force the wind turbine speed to its optimal value the presence of faults in the actuator.
54

Gestion de l'énergie dans un système multi-sources photovoltaïque et éolien avec stockage hybride batteries/supercondensateurs / Energy management in a photovoltaic/wind hybrid power system with batteries/supercapacitors storage

Croci, Lila 18 December 2013 (has links)
Ce mémoire présente le travail de recherche effectué pour la conception d'une stratégie de commande originale, destinée aux systèmes de puissance hybrides en sites isolés. Le système considéré, voué à l'alimentation électrique d'une habitation, comprend deux sources, un groupe de panneaux photovoltaïques et une petite éolienne, et deux types de stockage, un banc de batteries lithium-ion et un de supercondensateurs. Face au problème de gestion de l'énergie dans un système hybride, et aux enjeux de maximisation de sa puissance produite, nous proposons de développer une stratégie de commande basée sur les flux d'énergie. pour cela, nous présentons dans un premier temps les modélisations d'Euler-Lagrange et hamiltonienne du système. Ces modèles permettent d'utiliser la propriété de passivité de celui-ci, et ainsi de synthétiser des commandes par injection d'amortissement pour chaque source, afin de maximiser sa production, et pour les supercondensateurs, dans le but d'assurer une répartition cohérente des flux d'énergie entre eux et les batteries. Les commandes sont finalement mises en œuvre dans un simulateur, puis dans un banc d'essai expérimental, afin d'une part de comparer leurs performances à celles de solutions préexistantes, et d'autre part de valider le bon fonctionnement du système hybride complet les utilisant. / This thesis presents the research about design of a new control strategy for stand-alone hybrid power systems. The considered system is composed of two sources, a group of photovoltaic panels and a low-power wind generator, and of two kinds of storage, a bank of lithium-ion batteries and one of supercapacitors. Faced with the problem of energy management in a hybrid power system, and with necessity of maximizing the produced power, we intend to develop an energy-based control strategy.For this purpose, we present the system's Euler-Lagrange modeling and Hamiltonian modeling. These models allow the use of the passivity property, and then the design of Passivity-Based Controllers for each source, in order to maximize its production, and for the supercapacitors, to ensure a fitted power sharing between batteries and them. The controllers are finally implemented in a simulator, and then in a experimental test bench, in order to compare their performances to pre-existent solutions, and tovalidate the control law for the global hybrid system.
55

Contribution for integrating urban wind turbine into electrical microgrid : modeling and control / Contribution à l'intégration des éoliennes urbaines dans un micro réseau électrique : modélisation et contrôle

Liu, Hongliang 27 January 2017 (has links)
L’intégration de l’énergie éolienne, qui est une ressource renouvelable très utilisée, n’est pas toujours facile pour le micro-réseau urbain. Dans cette thèse, une éolienne urbaine basée sur une machine synchrone à aimants permanents (MSAP) est étudiée pour être intégrée dans un micro-réseau urbain à courant continu. Un état de l'art concernant les énergies renouvelables, les micro-réseaux à courant continu et les stratégies de contrôle de la production d'énergie éolienne, est réalisée. Basé sur un modèle d’éolienne urbaine répondant à la demande du système électrique, qui se compose d’un émulateur de vent et de pales, un MSAP et un convertisseur DC/DC, cette thèse propose des méthodes de poursuite du point de puissance maximale satisfaisant à l’obligation de produire de l’énergie dans la mesure du possible. Une stratégie de contrôle à puissance limitée répond correctement. De simples à complexes, quatre algorithmes MPPT, P&O à pas fixe, P&O à pas variable avec la méthode Newton-Raphson améliorée, P&O à pas variable à base de logique floue et une méthode indirecte de type lookup table, sont étudiés et implémentés pour être comparés à l’aide de trois profils de vitesse du vent. Par expérimentation, les algorithmes MPPT et PLC sont comparés, analysés et discutés. Résumant tous les résultats expérimentaux, la méthode lookup table peut gérer toutes les exigences du mode de fonctionnement MPPT en présentant la meilleure performance, mais, dans le mode de fonctionnement PLC, la P&O à base de logique floue présente les meilleures performances. / The integration of the wind power, which is one mostly used renewable resource, is always one challenger for urban microgrid. In this thesis, one urban wind turbine based on a permanent magnet synchronous machine (PMSM) is studied in order to be integrated into a DC urban microgrid. A state of the art concerning the renewable energies, DC microgrid, and control strategies of wind power generation is done. Based on a model of urban wind turbine fitting the demand of urban electric system, which consists of an emulator of wind speed and blades, a PMSM and a DC/DC converter, this thesis proposes the maximum power point tracking (MPPT) methods satisfying the requirement of producing energy as much as possible, and power limited control (PLC) strategies answering the demand of flexible energy production. From simple to complex, four MPPT algorithms including Perturbation and Observation (P&O) fixed step-size method, P&O with improved Newton-Raphson method, P&O with fuzzy logic method and lookup table method are studied and implemented to be compared with each other using three wind velocity profiles. According to the experience about MPPT subject, four PLC algorithms are introduced and implemented to be analyzed and compared with each other with one power demand profile calculated randomly. Summarizing all experimental results, the lookup table method can handle all requirement of MPPT operating mode supplying the best performance, however, in the condition of more flexible power demand operating mode, the combination of P&O and fuzzy logic method presents the best performance and potential which can be achieved in future works.
56

Modeling, Optimization And Design Of A Solar Thermal Energy Transport System For Hybrid Cooking Application

Prasanna, U R 07 1900 (has links) (PDF)
Cooking is an integral part of each and every human being as food is one of the basic necessities for living. Commonly used sources of energy for cooking are firewood, crop residue, cow dung, kerosene, electricity, liquefied petroleum gas(LPG), biogas etc. Half of the world’s population is exposed to indoor air pollution, mainly the result of burning solid fuels for cooking and heating. Wood cut for cooking purpose contributes tothe16 million hectares(above4% of total area of India) of forest destroyed annually. The World Health Organization(WHO) reports that in 23 countries 10% of deaths are due to just two environmental risk factors: unsafe water, including poor sanitation and hygiene; and indoor air pollution due to solid fuel usage for cooking. In under-developed countries, women have to walk 2kms on average and spend significant amount of time for collecting the firewood for cooking. The cooking energy demand in rural areas of developing countries is largely met with bio-fuels such as fuel wood, charcoal, agricultural residues and dung cakes, whereas LPG or electricity is predominantly used in urban areas. India has abandon amount of solar energy in most of the regions making it most ideal place for harvesting solar energy. With almost 300 sunny days each year, one can confidently relay on this source of energy. India’s geographical location is in such a way that theoretically it receives 5x1015 kWh/ year of solar energy. Solar cooking is the simplest, safest, environmental friendly and most convenient way to cook. It is a blessing for those who cook using firewood or cow dung, who walk for miles to collect wood, who suffer from indoor air pollution. Hence solar cooking is going to play major role in solving future energy problem. Solar based cooking has never been a strong contender in the commercial market or even close to being a preferred method of cooking. They have been relegated to demonstration appliances to show case the solar based concepts. In this mode, cooking is no longer a time independent activity that can be performed at any time of day. One is forced to cook only at certain times when there is sufficient insolation. The geography of the cooking activity also shifts away from the kitchen. The kitchen is no longer the hearth of the home as the actual cooking activity shifts to the roof tops or high insolation platforms. This further adds to the inconvenience apart from being unable to cook at night or during cloudy conditions or during most of the winter days. Another issue of significant inconvenience is the general social structure in most families of the developing countries wherein the cooking activity is carried out by the senior ladies of the home. They are generally not athletic enough to be moving to and from the kitchen and the roof top to carry out the cooking exercise. As the solar cookers are enclosed spaces, interactive cooking is not possible let alone having any control on the rate of cooking. These are some of the more significant issues in the social psyche that has abundantly impeded the acceptance of solar thermal based cooking appliances. These issues and problems are in fact the motivating factors for this thesis. Based on these motivating factors, this thesis aims to propose solutions keeping the following points as the major constraints. cooking should be performed in the kitchen. one should be able to perform the cooking activity independent of the time of day or insolation. the cooking activity should be interactive the time taken for cooking should be comparable with the conventional methods in vogue. there should be a reduction in the use of conventional energy. Using the constraints and the motivating factors discussed above as the central theme, this thesis proposes a method to transfer solar thermal energy to the kitchen and act as a supplement to the conventional source of energy like the LPG or other sources that are traditionally being used in the households. The method proposed is in fact a hybrid scenario wherein the solar thermal is used to supplement the traditional source. Solar photovoltaic cells are also used to power the electronics and apparatus proposed in this thesis. This thesis addresses in detail the issues in analysis, modeling, designing and fabrication of the proposed hybrid solar cooking topology. The main goal of the proposed system is to transfer heat from sun to the cooking load that is located in the kitchen. The topology includes an additional feature for storing the energy in a buffer. The heat is first transferred from the solar thermal collector to a heat storage tank(that acts as the buffer) by circulating the heat transfer fluid at a specific flow rate that is controlled by a pump. The stored heat energy that is collected in the buffer is directed into the kitchen by circulating the heat transfer fluid into the heat exchanger, located in the kitchen. This is accomplished by controlling the flow rate using another pump. The solar thermal collector raises the temperature of the thermic fluid. The collector can be of a concentrating type in order to attain high temperatures for cooking. Concentrating collector like linear parabolic collector or parabolic dish collector is used to convert solar energy into heat energy. Absorption of energy from the incident solar insolation is optimized by varying the flow rate of circulating thermic fluid using a pump. This pump is energized from a set of photovoltaic panels(PV cell) which convert solar energy into electrical energy. The energy absorbed from the solar thermal collector is stored in a buffer tank which is thermally insulated. Whenever cooking has to be carried out, the high temperature fluid from the buffer tank is circulated through a heat exchanger that is located in the kitchen. The rate of cooking can be varied by controlling both the flow rate of fluid from the buffer tank to heat exchanger and also by controlling the amount of energy drawn from the auxiliary source. If the available stored energy is not sufficient, the auxiliary source of energy is used for cooking in order to ensure that cooking is in-dependent of time and solar insolation. In the proposed hybrid solar cooking system, the thesis addresses the issues involved in optimization of energy extracted from sun to storage tank and its subsequent transfer from the storage tank to the load. The flow rate at which maximum energy is extracted from sun depends on many parameters. Solar insolation is one of the predominant parameters that affect the optimum flow rate. Insolation at any location varies with time on a daily basis (diurnal variations) and also with day on a yearly basis(seasonal variation). This implies that the flow rate of the fluid has to be varied appropriately to maximize the energy absorbed from sun. In the proposed system, flow rate control plays a very significant role in maximizing the energy transfer from the collector to the load. The flow rate of the thermic fluid in the proposed system is very small on the order of 0.02kg/s. It is very difficult to sense such low flows without disrupting the operating point of the system. Though there are many techniques to measure very low flow rates, they invariably disrupt the system in which flow rate has to be measured. Further, the low flow sensors are far too expensive to be included in the system. A reliable, accurate and inexpensive flow measuring technique has been proposed in this thesis which is non-disruptive and uses a null-deflection technique. The proposed measuring method compensates the pressure drop across the flow meter using a compensating pump. The analysis, modeling, design and fabrication of this novel flow meter are addressed. The design and implementation of different subsystems that involves the selection and design of solar concentrating collector and tracking are explained. Finally, it is essential to know the economic viability of the proposed system that is designed and implemented. To understand the economics, the life cycle cost analysis of the proposed system is presented in this thesis. The major contributions of this thesis are: Energy transport: Major challenge in energy transport is to bring heat energy obtained from the sun to the kitchen for cooking. Energy transferred from solar insolation to the cooking load has to be optimized to maximize the overall efficiency. This can be split in to two parts,(a) optimizing efficiency of energy transferred from the collect or to the energy buffer tank,(b) optimizing efficiency of energy transferred from the buffer tank to the load. The optimization is performed by means of a maximum power point tracking(MPPT) algorithm for a specific performance index. Modeling of the cooking system: There are several domains that exist in the solar cooking system such as electrical domain, thermal domain, and hydraulic domain. The analysis of power/energy flow across all these domains presents a challenging task in developing a model of the hybrid cooking system. A bond graph modeling approach is used for developing the mathematical model of the proposed hybrid cooking system. The power/energy flow across different domains can be seamlessly integrated using the bond graph modeling approach. In this approach, the various physical variables in the multi-domain environment are uniformly de-fined as generalized power variables such as effort and flow. The fundamental principle of conservation of power/energy issued in describing the flow of power/energy across different domains and thus constructing the dynamic model of the cooking system. This model is validated through experimentation and simulation. Flow measurement: A novel method of low fluid mass flow measurement by compensating the pressure drop across the ends of measuring unit using a compensating pump has been proposed. The pressure drop due to flow is balanced by feedback control loop. This is a null-deflection type of measurement. As insertion of such a measuring unit does not affect the functioning of the systems, this is also a non-disruptive flow measurement method. This allows the measurement of very low flow rate at very low resolution. Implementation and design of such a unit are discussed. The system is modeled using bond graph technique and then simulated. The flow meter is fabricated and the model is experimentally validated. Design Toolbox: Design of hybrid cooking system involves design of multi domain systems. The design becomes much more complex if the energy source to operate the system is hybrid solar based. The energy budget has to be evaluated considering the worst case conditions for the availability of the solar energy. The design toolbox helps in assessing the user requirement and help designing the cooking system to fulfill the user requirement. A detailed toolbox is proposed to be developed that can be used in designing/selecting sub-systems like collector, concentrator, tracking system, buffer tank, heat exchanger, PV panel, batteries etc. The toolbox can also be used for performing life cycle costing.
57

Uma contribuição ao estudo de algoritmos de rastreamento de máxima potência de sistemas fotovoltaicos utilizando a equação de Monod

Camilo, Jones Clemente January 2018 (has links)
Orientador: Prof. Dr. Alfeu Joãozinho Sguarezi Filho / Coorientador: Prof. Dr. Joel David Melo Trujillo / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, Santo André, 2018. / Neste trabalho é proposto um algoritmo de rastreamento de máxima potência com a utilização da equação de Monod. O algoritmo aplica-se em sistemas fotovoltaicos conectados à rede elétrica. Os resultados e as comparações mostram que o algoritmo proposto apresenta algumas vantagens em comparação ao algoritmo de perturbação e observação para diversas condições de operação, em especial quando os painéis são submetidos a sombreamento parcial. / In this work we propose an algorithm of maximum power point tracking with using the Monod Equation. The algorithm applies to photovoltaic systems connected to the grid. The results and the comparition show that the algoritmo proposal has some advantages compared to algoritm Perturb and Observe in many situation of operation, in special when the fotovoltaics painels have parcial shading.
58

Regulace provozu autonomních solárních systémů / Control system used in autonomous solar system

Slezák, Pavel January 2008 (has links)
This thesis dealing with description and of autonomous solar systems and algorithms for control of decision-making mechanism. Optimal set of these machanism has effeect in raise of efficiency in hole autonomous system. In practical purposes propose create one by using microprocesor ATMEGA8, which measure all electrical data in system and control all decisions of implemented algorithm.
59

Controle chaveado de sistemas com incertezas utilizando otimizadores não derivativos /

Silva, Paulo Henrique Gonçalves Leonel da. January 2020 (has links)
Orientador: Marcelo Carvalho Minhoto Teixeira / Resumo: Nesta tese, utiliza-se um otimizador analógico não derivativo proposto por Teixeira & Żak em 1999 como principal ferramenta para os sistemas de controle dos projetos desenvolvidos. Tal otimizador é composto por blocos não lineares e pode ser classificado como um sistema neural artificial. Sistemas chaveados têm grande aplicação prática na otimização de sistemas e são caracterizados por possuírem subsistemas e uma lei de chaveamento que seleciona cada subsistema a cada momento. Deve-se definir condições para que seja possível projetar uma lei de chaveamento que atenda requisitos de projeto. O estudo de técnicas de controle extremal na solução de problemas de busca pelo rastreamento do máximo ponto de potência (do inglês: Maximum Power Point Tracking - MPPT), vem apresentando resultados interessantes na literatura e um tipo de sistema à qual essa técnica pode ser aplicada, é na geração fotovoltaica. Aplica-se o otimizador analógico citado na busca do MPPT de uma célula fotovoltaica, com o objetivo de observar o controle extremal atuando em um processo de otimização, estendendo o controle para quando existem variações de irradiação solar (cenário de uma possível passagem de nuvens). Também observa-se o comportamento do sistema quanto a manter seu correto funcionamento e estabilidade ultimate bounded. A contribuição principal desta tese foi uma nova proposta de utilização conjunta do otimizador de Teixeira & Żak no projeto de controladores ˙ chaveados baseados na minimização da d... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: On this thesis, a non-derivative analog optimizer, proposed by Teixeira & Żak in 1999, was used as the main tool for the proposed control system. Such optimizer is structured by nonlinear blocks and can be classified as an artificial neural system. Switched systems have great theoretical and practical application in systems optimization and are characterized by having subsystems, and a switching law that selects each subsystem at each moment. It is necessary to define conditions so that it is possible to design a switching law for the desired performance of the controlled system. The study of Extremum Seeking Control techniques in the solution of problems of Maximum Power Point Tracking has presented interesting results, and one type of system which this technique can be applied is in the photovoltaic generation. The analog optimizer is applied in the Maximum Power Point Tracking of a photovoltaic cell, with the objective of observing the actuation of the extremal seeking control in an optimization process, extending the control when there are solar irradiation variations (a possible clouds passage scenario). And also observe the behavior of the system and how to maintain its correct functioning and ultimate bounded stability. The main contribution of this thesis was a new procedure for using the mentioned analog optimizer in the design of switched controllers based on the minimization of the derivative of a Lyapunov function. This method allows the relaxed design of controll... (Complete abstract click electronic access below) / Doutor
60

Contribution to the DC-AC conversion in photovoltaic systems : Module oriented converters / Contribution à l’étude de la conversion DC-AC dans des systèmes photovoltaïques : Convertisseurs orientés au module PV

Lopez Santos, Oswaldo 06 February 2015 (has links)
Ces dernières années, un intérêt croissant pour les systèmes électroniques de puissance a été motivé par l'émergence de sources d'énergie distribuées et renouvelables raccordées aux réseaux électriques. Dans ce contexte, la nécessité de topologies de faibles puissances alimentées par quelques modules photovoltaïques, en évitant l'utilisation de transformateurs, a ouvert l'étude de convertisseurs spéciaux et l’étude des stratégies de commande associées afin d’assurer la stabilité, la fiabilité et un rendement élevé du dispositif. Une possible solution est d’utiliser un dispositif générique connu dans la littérature scientifique et commerciale comme « micro-onduleur » ou «convertisseur intégré au module » qui avec le module photovoltaïque définit un produit « plug and play » appelé "module AC".Ce travail est consacré à l'étude d'un micro-onduleur monophasé avec deux étapes sans transformateur raccordée au réseau. La topologie proposée est composé d’un convertisseur DC-DC non isolé élévateur avec un gain quadratique et un onduleur réducteur lié au réseau connectés en cascade. Le convertisseur DC-DC extrait en permanence la puissance maximale du module photovoltaïque malgré les changements dans les conditions environnementales. L'étape DC-AC injecte la puissance extraite par l'étape DC-DC dans le réseau et assure un niveau élevé de qualité de l’énergie. Les efforts de recherche de ce travail sont concentrés sur la mise au point de commandes utilisant comment base, la théorie de contrôle par mode de glissement, qui conduit à une mise en œuvre simple avec une description théorique complète validée á partir de simulations et expérimentations.Après avoir décrit l'état de l’art dans le premier chapitre, le manuscrit est divisé en quatre chapitres, qui sont dédiés respectivement à l’algorithme de recherche du point de puissance maximale (MPPT), á l’étape de conversion DC-DC, á l'étape de conversion DC-AC et finalement au micro-onduleur complet. Un nouvel algorithme de recherche extrémal du point de puissance maximale est développé (SM-ESC). Pour la étape DC-DC, le convertisseur élévateur quadratique avec seulement un interrupteur contrôlé est étudié utilisant le concept de résistance sans perte par mode de glissement (de l’acronyme anglais : Sliding-Mode Loss-Free-Resistor – SM-LFR) afin d’obtenir un gain de tension élevé avec un fonctionnement sûr et compatible avec l’algorithme MPPT. Pour la étape DC-AC, le convertisseur de pont complet est contrôlé comme un onduleur de source de puissance (de l’acronyme anglais : Power Source Inverter - PSI) en utilisant une commande par mode de glissement qui poursuit une référence sinusoïdale de courant de sortie. Cette commande est complétée par une boucle de régulation de la tension du bus DC qui assure une haute qualité d’énergie injectée dans le réseau. Enfin, les trois étapes constitutives sont fusionnées pour obtenir un micro-onduleur complètement contrôlé par la technique de mode de glissement, ce qui constitue le principal résultat et contribution de cette thèse. / These last years, a growing interest in power electronic systems has been motivated by the emergence of distributed renewable energy resources and their interconnection with the grid. In this context, the need of low power topologies fed by a few photovoltaic modules avoiding the use of transformers opens the study of special converters and the associated control strategies ensuring stability, reliability and high efficiency. A resulted generic device known in the commercial and scientific literature as “microinverter” or “module integrated converter” performs a plug and play product together with the PV module called an “AC module”.This work is devoted to the study of a transformer-less single-phase double-stage grid-connected microinverter. The proposed topology has a non-isolated high-gain boost type DC-DC converter and a non-isolated buck type DC-AC converter connected in cascade through a DC bus. The DC-DC converter permanently extracts the maximum power of the PV module ensuring at the same time a good performance coping with power changes introduced by the change in the environmental conditions. The DC-AC stage injects the power extracted by the DC-DC stage into the grid ensuring a high level of power quality. The research efforts focus on the involved control functions based on the sliding mode control theory, which leads to a simple implementation with a comprehensive theoretical description validated through simulation and experimental results.After giving the state-of-the-art in the first chapter, the manuscript is divided into four chapters, which are dedicated to the Maximum Power Point Tracking (MPPT), the DC-DC stage and its control, the DC-AC stage and its control and the complete microinverter. A new Extremum Seeking Control (ESC) MPPT algorithm is proposed. The single-switch quadratic boost converter is studied operating as a Loss-Free-Resistor (LFR) obtaining a high DC output voltage level with a safe operation. The full-bridge converter is controlled as a Power Source Inverter (PSI) using a simple sliding-mode based tracking law, regulating the voltage of the DC bus and then ensuring a high power quality level in the grid connection. Finally, the three building blocks are merged to obtain a sliding mode controlled microinverter constituting the main result and contribution of the work

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