In this thesis the integration of photovolatic (PV) generation and energy storage into the electrical grid is discussed. Although the studied system is for grid tied applications, here the integration of the PV generation and the energy storage system (ESS) on the DC-side of the system is addressed. The work contained in this thesis focuses on the integration of the DC-working parts before interfacing them with the grid through the use of an inverter and seeks an increasing in the energy that the system can deliver.First, a study of classical systems that present well-differentiated parts is presented: PV generation, a lithium-ion battery based ESS, the utility grid and a residential electricity consumer. PV installations of 3 and 10kWp are considered together with storage capacities ranging from 1 to 9kWh. This yields interesting insights on how the system works based on the timing of the generation and consumption of energy. The results are used to highlight the weaknesses of the selected converter arrangement for the interfacing of the PV source and the ESS. Results show that the system is rather stiff and lacks from conversion efficiency when it needs to work in a wide range of powers, mainly due to low consumer power demand during battery discharge. In this first part of the thesis, three solutions to workaround the efficiency problem are proposed: reducing the difference between the ESS and the DC-bus voltages, using isolated converters to interface the ESS, or adopting a new arrangement of the parts of the system. One of the first two proposed solutions should be adopted if the same system topology is to be kept. These two solutions address the efficiency problem when the ESS is involved in the energy conversion. The third solution is proposed as alternative to the classical systems that use a DC-bus to exchange power with the different parts of the system. The new proposed arrangement features a distributed maximum power point (DMPPT) type system that includes storage at module level. DMPPT systems are able to track the maximum power point (MPPT) of each panel separately by connecting a small power electronic converter (PEC) to each PV panel. They are specially useful when the PV installation receives uneven irradiance, i.e. shadows are present in some of the panels, increasing the annual yield of PV energy from 7 to 30% as reported in the literature. Unfortunately, this kind of systems cannot always handle high irradiance mismatches, and fail to track the maximum power point (MPP) throughout the whole installation in some cases. Including batteries at module level instead of connecting them to the DC-bus, allows for increasing the MPPT range of the system, virtually to any severity of irradiance mismatch (depending on the state of charge (SoC) of the battery pack), as well as adding storage capability to the system. The novel proposed system is able to workaround the problems of using non-isolated converters, achieving PV energy conversion efficiencies from 86% (for at least 10% of the peak power) to 90% and storage charge/discharge efficiencies ranging from 86% to 95%. Besides, it brings the opportunity to exploit the synergies of having storage at module level in systems that combine renewable energies and storage. Moreover, DMPPT systems achieve superior PV generation under partially shaded conditions when compared to classical PV arrays increasing the PV generation when compared to classical or centralized PV installations up to 45% in power as reported in the literature.In the second part of the thesis, the proposed novel DMPPT topology is presented. The whole system is fully designed from scratch, including PECs, sizing of the different parts of the modules, embedded control loops of the modules and supervisory control of the whole system. Finally, the results obtained from running the proposed system are shown and discussed, and suggestions given on how to operate and protect the system. Experimental results are obtained using a 1.5kWp PV power and 1.5kWh capacity test bench built for that purpose.The proposed system is able to generate PV energy, store the energy coming from PV generation and inject the generated and stored energy into the grid. The proposed system extends the MPPT capability of storage-less series-connected DMPPT systems. This is achieved by using the batteries not only to store energy when required, but also to compensate the power mismatch across DMPPT modules of the same string when the output voltage of the modules becomes a limit. It also presents a modular and upgradable approach to PV systems including storage. This modularity also brings fault tolerance, and an ability to continue working after failure of one or more of the DMPPT modules by partially or completely isolating the faulty module (depending on the nature of the fault). Moreover, the addition of the DC-DC converters allows for the use of different PV panels in the system, i.e. from different manufacturers or technologies.In conclusion, the presented system is very flexible, can be designed for a wide range of power levels and energy storage sizes, and presents improved reliability when compared to other series-connected DMPPT systems. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / O presente trabalho apresenta o estudo de um conversor CC/CC com dois estÃgios para aplicaÃÃo no desenvolvimento de sistemas autÃnomos de energia elÃtrica. O conversor sob estudo consiste basicamente da associaÃÃo de dois conversores CC/CC, em que entre eles à inserido um banco de baterias para dar continuidade ao fornecimento de energia em perÃodos em que nÃo hà radiaÃÃo solar. Todos os conversores utilizados para a composiÃÃo do sistema sÃo do tipo boost utilizando a cÃlula de comutaÃÃo de trÃs estados (CCTE). O primeiro conversor tem a funÃÃo enviar energia desde os painÃis fotovoltaicos a um banco de baterias de 48 V e permitir a operaÃÃo dos painÃis fotovoltaicos no ponto de mÃxima potÃncia (MPP- Maximum Power Point). O segundo estÃgio à constituÃdo por um conversor de alto ganho de tensÃo, cujo papel à elevar a tensÃo do banco de baterias de 48 V para uma tensÃo de 400 Vcc, formando assim o barramento de saÃda do sistema em tensÃo contÃnua. Para garantir a regulaÃÃo da tensÃo em 400 Vcc, foi implementada a tÃcnica de controle LQR (Linear Quadratic Regulator). Para o projeto do controle LQR à utilizado uma metodologia simplificada para a obtenÃÃo de um modelo reduzido do conversor de alto ganho de tensÃo. Para cada estÃgio à apresentado seu estudo teÃrico, anÃlise de perdas e dimensionamento dos componentes para o atendimento das especificaÃÃes de projeto. Para verificar a anÃlise teÃrica foi montado um protÃtipo para cada estÃgio e os resultados experimentais sÃo apresentados neste trabalho. / This work presents a study of a DC/DC converter with two stages for implementation of a stand-alone photovoltaic power system. The converter under study consists of two DC/DC converters, in which between them is inserted a battery bank to give continuity to the energy supply in periods when there isnât solar radiation. All converters used for the composition of the system are of type boost based on the three-state switching cell (TSSC). The first converter has function of to send energy from photovoltaic panels to a battery bank of 48 V formed by four batteries of 12V connected in series, and its function is to allow the photovoltaic panels operation at the maximum power point (MPP). The second stage consists of a converter of high voltage gain, whose role is to raise the 48 V battery bank voltage to 400V DC output bus voltage. To ensure the regulation of voltage at 400 V DC, was implemented the control LQR (Linear Quadratic Regulator). To design the controller LQR, a simplified methodology to obtain a model of the high-gain voltage converter is used. For each stage is presented its theoretical study, analysis and the components were designed and specified. To verify the theoretical analysis, was developed a prototype for each stage and the experimental results are presented in this work.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / With global need to reduce energy consumption, the search for more efficient technologies has become the focus of many studies. Among these technologies, it can mention the photovoltaic solar energy and LEDs, which have shown an expansion in recent decades. Photovoltaic generation is shown as an attractive energy source because it is renewable and its raw material is practically inexhaustible. While LEDs have a promising advance in lighting and is used in several applications. To integrate these technologies, this paper proposes the study of a DC-DC step-up switched-capacitor (SC) converter for LEDs applied to photovoltaic stand-alone systems. The proposed circuit differs from other topologies SC to insert an inductor in series with the input source, which can operate in discontinuous conduction mode (DCM), reducing losses switching, or continuous conduction mode (CCM), allowing the reduction of conduction losses in the circuit. The converter is driven by the frequency modulation, which is obtained as a function of input voltage. For this reason, the current in the LEDs can be stabilized without the need for sensor or feedback. The prototype developed in the laboratory was designed for a lamp of 54 W and operating at high frequency (up to 165 kHz), allowing the reduction of the circuit volume. Experimental results of the circuit in DCM and CCM show that the converter has a high yield, validating the proposal. / Tendo em vista a tendÃncia da reduÃÃo do consumo de energia no mundo, a busca por tecnologias mais eficientes tem se tornado o foco de muitos estudos. Dentre estas tecnologias, pode-se citar a energia solar fotovoltaica e os LEDs, que vem apresentando uma expansÃo nas ultimas dÃcadas. A geraÃÃo fotovoltaica se mostra como uma atrativa fonte de energia, por ser renovÃvel e sua matÃria-prima ser praticamente inesgotÃvel. Enquanto os LEDs apresentam um avanÃo promissor na iluminaÃÃo, sendo utilizado nas mais diversas aplicaÃÃes. Visando a integraÃÃo destas tecnologias, este trabalho propÃe o estudo de um conversor CC-CC elevador com capacitor comutado (Switched Capacitor - SC) para LEDs, aplicado a sistemas fotovoltaicos autÃnomos. O circuito proposto se difere de outras topologias SC por inserir um indutor em sÃrie com a fonte de entrada, o qual pode operar no modo de conduÃÃo descontÃnua (MCD), reduzindo as perdas por comutaÃÃo, ou no modo de conduÃÃo contÃnua (MCC), possibilitando a reduÃÃo das perdas por conduÃÃo do circuito. O conversor à acionado atravÃs da modulaÃÃo por frequÃncia, a qual à obtida em funÃÃo da tensÃo de entrada. Por este motivo, a corrente nos LEDs pode ser estabilizada sem a necessidade de sensores ou de realimentaÃÃo. O protÃtipo desenvolvido em laboratÃrio foi projetado para uma luminÃria de 54 W e operando em alta frequÃncia (atà 165 kHz), possibilitando a reduÃÃo do volume do circuito. Os resultados experimentais obtidos do circuito MCD e MCC sÃo analisados e validam a proposta, mostrando que o conversor apresenta rendimento elevado

Este trabalho propÃe o estudo de uma nova topologia, com dois estÃgios, de um conversor estÃtico, onde existe um fluxo de potÃncia auxiliar com o objetivo de aumentar o rendimento do sistema. O primeiro estÃgio à um conversor CA-CC com correÃÃo do fator de potÃncia (PFC) e o segundo estÃgio à um conversor CC-CC isolado em alta frequÃncia. Os dois estÃgios do conversor proposto sÃo modelados por equaÃÃes diferenciais e atravÃs desses modelos sÃo desenvolvidas tÃcnicas de controle nÃo linear para o funcionamento dos conversores em malha fechada. A correÃÃo do fator de potÃncia do primeiro estÃgio à realizada pela tÃcnica de controle PBC (passivity-based control), enquanto que a tensÃo de saÃda do primeiro estÃgio à realizada pelo controle I&I (immersion and invariance). O segundo estÃgio necessita controlar somente a tensÃo de saÃda atravÃs do controle backstepping, por se tratar de um conversor CC-CC. / This work proposes a study of a new static converter topology with two stages, where the first is an AC-DC converter with PFC and the second is a DC-DC converter isolated in high-frequency. In addition, the static converter has a secondary power flow to achieve a better efficiency from the system. The two converterâs stages are modeled as differential equations, and through those models nonlinear control techniques are developed for close loop operation. The power-factor correction in the first stage is performed by the PBC (passivity-based control) control technique, while the output voltage from the first stage is performed by the I&I (immersion and invariance) control. As the second stage is a DC-DC converter, it only needs to control the output voltage, which is achieved through the backstepping control.

O presente trabalho aborda a análise e o desenvolvimento de conversores CC-CC com alto ganho de tensão, para aplicações com fontes de energia de baixíssima tensão, porém capazes de fornecer altas correntes, como: painéis fotovoltaicos, células a combustível e baterias. O principal objetivo deste trabalho é elevar a tensão de uma única célula a combustível até um nível adequado de tensão para realizar a carga de uma bateria com tensão nominal de aproximadamente 12 V, de modo eficiente, com baixa ondulação na corrente de entrada do conversor e com baixa ondulação na tensão de saída. Para alcançar o objetivo proposto, dezenas de topologias de conversores foram estudadas, analisadas, simuladas e implementadas. O trabalho também apresenta uma comparação entre topologias de conversores CC-CC que realizam a transferência de energia por meio de indutores acoplados, com uma topologia de conversor que opera com transferência direta de energia por meio de um transformador. Por fim, os resultados experimentais são apresentados com o intuito de validar os resultados simulados e teóricos. / This work shows the analysis and development of DC-DC converters with high voltage gain, for applications with energy sources of low input voltage, but capable of providing high currents, such as: photovoltaic panels, fuel cells and batteries. The main objective of this work is to raise the voltage of a single fuel cell to a suitable vol-tage level to efficiently charge a battery with rated voltage of approximately 12 V, with low current ripple in the converter and with low output voltage ripple. To achieve the proposed objective, dozens of topologies of converters were studied, analyzed, simulated and implemented. This work shows a comparison between topologies of DC-DC converters that perform power transfer via coupled inductors, with a converter topology operating with direct energy transfer through a transformer. Finally, experimental results are presented in order to validate the theoretical and simulated results.

Ce travail concerne l’étude, le dimensionnement et la réalisation d’un convertisseur continu-continu, associé à une source de type pile à combustible. Pour l’application envisagée, ce convertisseur a un rapport de transformation élevé voisin de 12. De plus l’ondulation de courant est limitée à 1% du courant moyen maximal. La mise en cascade de deux convertisseurs a été retenue pour obtenir un rapport de transformation élevé. Le premier étage est un Boost entrelacé associé à un filtre d’entrée de type L-C, qui permettent de réduire fortement l’ondulation du courant de source. Le second étage est un Boost à trois niveaux qui permet de diminuer les contraintes en tension sur les interrupteurs, et de réduire ainsi les pertes du convertisseur. La commande du convertisseur est ensuite définie en se basant sur l’utilisation d’un régulateur non linéaire. La gestion globale du système est effectuée par la régulation de la tension intermédiaire et de la puissance transitée à la charge en utilisant les principes des commandes « plates ». Enfin un banc de tests à puissance réduite (3 kW) a été réalisé, afin de valider le fonctionnement du convertisseur et les régulations proposées / This work deals with the study, design and building of a DC-DC converter, which is associated with a fuel cell source. According to the application, this converter should have a high voltage ratio which is about 12, and it is able to limit the ripple current of source below 1% of the maximum average current. A cascaded structure composed by two converters has been chosen and allows obtaining a high voltage ratio. The first stage is an interleaved Boost associated with a L-C input filter, to reduce ripple of the current delivered by the source. The second stage is a three-level Boost which reduces the voltage stress of the switches, thereby reducing losses of the converter. The control of the converter is defined basing on the use of a non-linear regulator. Thanks to use the flatness control, the global control is realized through the regulation of the intermediate voltage and of the power transited to the load. Finally, a small power test converter (3 kW) has been realized, in order to validate the converter operation and the proposed control

Les téléphones et tablettes de dernière génération embarquent une puissance de calcul numérique très importante nécessitant une puissance électrique d’alimentation toute aussi significative. Afin de réduire la consommation énergétique des composants numériques complexes des terminaux mobiles, des techniques de modulation dynamique de la tension d’alimentation et de la fréquence de fonctionnement du cœur de calcul numérique sont utilisées. Le convertisseur DC/DC qui assure l’alimentation du cœur numérique doit donc faire face à de forts transitoires de charge, de tension de référence et de tension de source. Le contrôle en mode glissant d’un convertisseur DC/DC permet un bon compromis entre les performances transitoires du convertisseur, la réalisation via des composants analogiques et la puissance dissipée par le contrôleur. C’est pourquoi ce type de contrôle apparait être adapté au contrôle de convertisseurs DC/DC alimentant des cœurs numériques. Cette thèse a pour objet l’étude des alimentations sur carte électronique où le contrôleur et l’étage de puissance sont intégrés sur puce tandis que les composants de puissance passifs sont montés sur le circuit imprimé. Le contrôle en mode glissant à fréquence de découpage fixe d’un convertisseur DC/DC a été démontré avec des résultats significatifs. Cependant les performances transitoires d’un tel convertisseur sont amoindries en raison des délais introduits par une fréquence de découpage fixe. Une nouvelle structure de régulation de fréquence de découpage d’un convertisseur DC/DC contrôlé en mode glissant est proposée dans cette thèse. Cette structure régule la fréquence de découpage moyenne du convertisseur tout en maintenant la réponse transitoire du convertisseur asynchrone par rapport à l’horloge de référence. Une analyse de stabilité qui prend en compte les spécificités d’un tel système est aussi proposée. Le convertisseur a été conçu sur un procédé CMOS 130nm de STMicroelectronics. La fréquence de découpage est maintenue volontairement faible pour conserver un rendement élevé avec des composants passifs externes. Le prototype présente un rendement supérieur à 80% entre 2.4mW et 960mW de puissance de sortie. / Mobile applications necessitate nowadays huge digital-resources. Power management of a digital System-On-Chip (SOC) is based on dynamic voltage scaling. DC/DC converters used to supply the digital SoCs are facing stringent constraints with respect to load-transients, line-transients and reference tracking. Hysteretic control is known as the most convenient control scheme with a fair trade-off between transient performances, analog implementation and power consumption, particularly for one-phase architecture. The thesis focuses on-board DC/DC with a significant constraint on footprint (i.e. on components count and values). Fixed switching-frequency hysteretic control has been experimented with significant results. Transient performances are reduced due to latency introduced in the switching frequency control. The present study focuses on the improvement of the concept as well as its implementation and the analysis of stability. A new analog implementation of the sliding-mode control is presented with switching-frequency control using a particular analog phase-locked-loop but preserve transient performances. The DC/DC converter is implemented in CMOS 130nm by STMicroelectronics. The switching frequency range has been voluntarily limited and excludes the possible integration of passive components for the sake of silicon access. A hybrid demonstrator is presented with efficiency higher than 80\% between 2.4 mW and 960 mW output power.

This thesis examines converter topologies suitable for Module Integrated Converters (MICs) in grid interactive photovoltaic (PV) systems, and makes a contribution to the development of the MIC topologies based on the two-inductor boost converter, which has received less research interest than other well known converters. The thesis provides a detailed analysis of the resonant two-inductor boost converter in the MIC implementations with intermediate constant DC links. Under variable frequency control, this converter is able to operate with a variable DC gain while maintaining the resonant condition. A similar study is also provided for the resonant two-inductor boost converter with the voltage clamp, which aims to increase the output voltage range while reducing the switch voltage stress. An operating point with minimized power loss can be also established under the fixed load condition. Both the hard-switched and the soft-switched current fed two-inductor boost converters are developed for the MIC implementations with unfolding stages. Nondissipative snubbers and a resonant transition gate drive circuit are respectively employed in the two converters to minimize the power loss. The simulation study of a frequency-changer-based two-inductor boost converter is also provided. This converter features a small non-polarised capacitor in a second phase output to provide the power balance in single phase inverter applications. Four magnetic integration solutions for the two-inductor boost converter have also been presented and they are promising in reducing the converter size and power loss.

Les recherches actives sur les matériaux photovoltaïques et sur les systèmes de gestion de cette énergie sont à la base de ces progrès constants. Le LAAS travaille depuis plusieurs années dans cette optique d'amélioration et d'optimisation de l'énergie électrique produite par les systèmes solaires photovoltaïques. L'insertion d'un étage d'adaptation entre un générateur photovoltaïque (PV) et une charge optimise le transfert d'énergie. Ainsi, cet étage, commandé par une MPPT (Maximum Power Point Tracking), permet de rechercher en permanence le point maximum de puissance délivré par le module PV. Afin d'accroître encore les performances énergétiques des systèmes solaires, cette thèse s'est délibérément orientée vers une architecture fortement distribuée. Cette approche, consistant à répartir la gestion du générateur PV, permet de se rapprocher au plus près de la production photovoltaïque et ainsi en optimiser la puissance électrique globalement produite. Pour cela, nous avons développé des prototypes de micro-convertisseurs dédiés aux applications faibles puissances photovoltaïques. Les mesures journalières effectuées nous ont permis d'étudier avec précision l'intérêt de l'architecture distribuée et d'obtenir des résultats de validation montrant les perspectives à venir. Plusieurs solutions d'architectures se dégagent avec différents bilans des gains énergétiques qu'elles apportent.

Switched-Capacitor Converters (SCC) suffer from a fundamental power loss deficiency which make their use in some applications prohibitive. The power loss is due to the inherent energy dissipation when SCC operate between or outside their output target voltages. This drawback was alleviated in this work by developing two new classes of SCC providing binary and arbitrary resolution of closely spaced target voltages. Special attention is paid to SCC topologies of binary resolution. Namely, SCC systems that can be configured to have a no-load output to input voltage ratio that is equal to any binary fraction for a given number of bits. To this end, we define a new number system and develop rules to translate these numbers into SCC hardware that follows the algebraic behavior. According to this approach, the flying capacitors are automatically kept charged to binary weighted voltages and consequently the resolution of the target voltages follows a binary number representation and can be made higher by increasing the number of capacitors (bits). The ability to increase the number of target voltages reduces the spacing between them and, consequently, increases the efficiency when the input varies over a large voltage range. The thesis presents the underlining theory of the binary SCC and its extension to the general radix case. Although the major application is in step-down SCC, a simple method to utilize these SCC for step-up conversion is also described, as well as a method to reduce the output voltage ripple. In addition, the generic and unified model is strictly applied to derive the SCC equivalent resistor, which is a measure of the power loss. The theoretical predictions are verified by simulation and experimental results.