The increasing global energy demand calls for attention on renewable energy development. Among the available technology, the photovoltaic (PV) panels is a popular solution. Thus, targeted Power Conditioning Systems (PCSs) are drawing increased attention in research. Microconverter is one of the PCS that can support versatile applications in various power line architectures. This work focuses on the comparison of circuit secondary side architectures for LLC converter for microconverter application. As the research foundation, general characteristic of solar energy and PV panel operation are introduced for the understanding of the needs. Previous works are referenced and compared for advantages and limitation. Base on conventional secondary resonant full bridge LLC converter, the two sub-topologies of different secondary rectification network: active, full bridge secondary and active voltage doubler output end LLC converter are presented in detail. The main operating principle is also described in mathematical formula with the corresponding cycle-by-cycle operation to ensure the functional equality before proceeding to performance comparison. Circuit efficiency analysis is conducted on the main power stage and the key components with frequency consideration. The hardware circuit achieved the designed function while the overall hardware efficiency result agrees with analysis. In the implementation, the transformer is costume built for the system pacification. Another part is the parasitic effect analysis. At a high operating frequency and to achieve very high-frequency operation, parasitic effect need to be fully understood and considered as it may have the dominating effect on the system. / Master of Science

Growing concerns about climate change have led to the world experiencing an unprecedented push towards renewable energy. Economic drivers and government policies mean that small, distributed forms of generation, like solar photovoltaics, will play a large role in our transition to a clean energy future. In this thesis, a novel DC-DC converter known as the Coupled Inductors Combined Cuk-SEPIC' (CI-CCS) converter is explored, which is particularly attractive for these photovoltaic applications. A topological modification is investigated which provides several benefits, including increased power density, efficiency, and operational advantages for solar energy conversion. The converter, which is based on the combination of the Cuk and SEPIC converters, provides a bipolar output (i.e. both positive and negative voltages). This converter also offers both step-up and step-down capabilities with a continuous input current, and uses only a single, ground-referenced switching device. A significant enhancement to this converter is proposed: magnetic coupling of the converter's three inductors. This can substantially reduce the CI-CCS converter's input current ripple - an important benefit for maximum power point tracking (MPPT) in photovoltaic applications. The effect of this coupling is examined theoretically, and optimisations are performed - both analytically and in simulations - to inform the design of a 4 kW prototype CI-CCS converter, switched at a high frequency (100 kHz) with a silicon carbide (SiC) MOSFET. Simulation and experimental results are then presented to demonstrate the CI-CCS converter's operation and highlight the benefits of coupling its inductors. An efficiency analysis is also undertaken and its sources of losses are quantified. The converter is subsequently integrated into a domestic photovoltaic system to provide a practical demonstration of its suitability for such applications. MPPT is integrated into the CI-CCS DC-DC converter, and a combined half bridge/T-type converter is developed and paired with the CI-CCS converter to form an entirely transformerless single-phase solar energy conversion system. The combination of the CI-CCS converter's bipolar DC output with the combined half bridge/T-type converter's bipolar DC input allows grounding at both the photovoltaic panels and the AC grid's neutral point. This eliminates high frequency common mode voltages from the PV array, which in turn prevents leakage currents. The entire system can be operated in grid-connected mode - where the objective is to maximise power extracted from the photovoltaic system, and is demonstrated in stand-alone mode - where the objective is to match solar generation with the load's power demands.

This thesis introduces a new method especially designed to control the instantaneous power in voltage sourced converters operating under unbalanced conditions, including positive, negative and zero sequence content. A transformation technique, labelled mno transformation, was developed to enable the decomposition of the total instantaneous power flowing on three-phase transmission topologies into constant and oscillating terms. It is applied to three-wire and four-wire schemes, especially accommodating zero sequence unlike previous approaches. Classical and modern electric power theories are presented, particularly focusing on their definitions for adverse AC scenarios. The main mathematical transformations conceived to analyze such situations are summarized, showing their respective advantages and disadvantages. An enhanced instantaneous power theory is introduced. The novel proposed power equations, named mno instantaneous power components, expands the application of the p-q theory, which is attached to the αβ0 transformation. The mno instantaneous power theory is applied to develop an innovative power control method for grid connected voltage sourced converters in order to minimize power oscillations during adverse AC scenarios, particularly with zero sequence content. The method permits to sustain constant instantaneous three-phase power during unbalanced conditions by controlling independently the constant and the oscillating terms related to the instantaneous power. The effectiveness of the proposed control approach and the proposed power conditioning scheme was demonstrated using electromagnetic transient simulation of a VSC connected to an AC system. / May 2017

Single stage cycloconverters generally incorporate hard switching at turn on and soft switching at turn off. This hard switching at turn on combined with the slow switching speeds of thyristors (the switch of choice for standard cycloconverters) limits their use to lower frequency applications. This thesis explores the analysis and design of a pulse density modulated (PDM), soft switching cycloconverter. Unlike standard cycloconverters, the controller in this converter does not adjust thyristor firing angles. It lets only complete half cycles of the input waveform through to the output. This allows and requires a much greater frequency step down from the input to the output. The advantages, shortcomings and tradeoffs of this topology are explored as this converter is designed, built and tested. The resulting cycloconverter has many deficiencies, but proves the concept of the PDM soft switching technique. Cases for further improvement and study are outlined. In the end, this converter shows much promise for applications requiring a high step down in frequency, as well as where the lower electromagnetic interference (EMI) of soft switching may be beneficial.

Aujourdhui, les énergies renouvelables deviennent progressivement des énergies à part entière qui rivalisent avec des énergies fossiles du point de vue coût et performance de production. Cependant, souvent leurs systèmes de conversion de lénergie en électricité souffre dun manque doptimisation qui en font encore des systèmes trop chers et présentant des déficiences importantes en rendement et en fiabilité. Pour cela, bien quil existe de plus en plus de travaux de recherches prouvant la viabilité de ce type de sources comme par exemple, lénergie photovoltaïque (PV) ou lénergie éolienne, beaucoup de réticentes existent pour installer ces systèmes à grande échelle autant en production de masse que chez des particuliers. A côté des autres laboratoires français, le LAAS-CNRS a choisi dapporter sa contribution sur la partie «Système» de la chaîne de conversion. En effet, du fait de lexistence de problèmes de non-optimisation électrique des systèmes et du manque déquipes de recherche sintéressant à ces axes, les points à résoudre se situaient alors autant sur la partie conversion électrique que thermique du générateur PV. Les premiers travaux entrepris se sont donc focalisés sur loptimisation de la partie conversion électrique. Pour cela, en sappuyant sur la création, le développement et lévolution constante du site de démonstration de 1kW crête PV entièrement instrumenté au sein même du LAAS, différentes architectures de conversion électriques dédiées au PV, ont été développées, notamment en collaboration avec lUniversité Rovira i Virgili de Tarragone (URV) et lUniversité Polytechnique Catalane de Barcelone (UPC). Très rapidement, nous nous sommes aperçus que, même si les systèmes PV faisaient des progrès considérables, ils ne pourraient à eux seuls représenter une source dénergie fiable. En effet, les variations de production étant fortement couplés aux données météorologiques, la production ne pouvait pas forcément être assurée lorsque lutilisation se n faisait sentir. Nous avons donc pensé à coupler les systèmes PV à dautres sources dénergie ainsi à travers des moyens de stockage. La maturité des études sur le photovoltaïque montre, quant à elle, de nouveaux débouchés, notamment sur les systèmes embarqués et les microsystèmes de très faibles puissances. Nous avons donc développé un nouvel axe de recherche depuis 2000 au sein du LAAS-CNRS sur les micro-sources et micro-convertisseurs intégrés dédiés aux microsystèmes. En effet, aujourdhui, les études menées sur loptimisation de convertisseurs statiques dénergie peuvent se généraliser à un certain nombre dapplications vis à vis de leur alimentation. Les objectifs sont de minimiser la taille et le volume tout en limitant les coûts de développement des nouveaux produits et en réduisant notamment les phases de prototypage réel. En effet, quel que soit le type dapplication visée (militaire, spatial, télécommunications, etc&), les nouvelles alimentations doivent être compactes, semi-intégrées ou bien, dans un futur proche, totalement intégrées. Pour cela, elles doivent être modélisables avec une grande précision, en vue doptimiser, dès leur conception, les contraintes de coût, de montée en fréquence et de puissance massique. En résumé, le but, dans les années futures, est datteindre de forts rendements de conversion sur les nouvelles alimentations devant avoir des tailles compatibles avec leurs applications, dans la droite ligne des travaux accomplis.

Because of its excellent and unique physical properties, ZnO nanowires have been widely used in numerous scientific fields such as sensors, solar cells, nanogenerators, etc. Although it is believed that single crystal ZnO has a much higher electron transfer rate than TiO₂, it was found that ZnO nanowire-based dye-sensitized solar cells (DSSCs) have lower efficiencies than TiO₂ nanoparticle-based DSSCs because the density and surface area of ZnO nanowires are usually lower than that of TiO₂ nanoparticles, limiting the cell's light absorption, and because the open-root structure of ZnO nanowires results in electron back transfer that causes charge shortage of the cell. Here, experimental studies were performed that utilize strategic manipulations of the design of the ZnO nanowire based DSSCs in efforts to address and solve its key challenges. It was shown that by incorporating various blocking layers into the design of the cell, the performance of the DSSC can be improved. Specifically, by placing a hybrid blocking layer of TiO₂-P4VP polymer between the substrate and the ZnO nanowires, the conversion efficiency of the cell was 43 times higher than that of a cell without this blocking layer due to the reduction of electron back transfer. Furthermore, in efforts to improve the surface area of the ZnO nanowire array, unique three dimensional structures of ZnO nanowires were fabricated. It was found that by significantly improving the overall density and surface area of the ZnO nanowire array through distinctive hierarchal nanowire structures, the light harvesting efficiency and electron transport were enhanced allowing the DSSC to reach 5.20%, the highest reported value for 3D ZnO NW based DSSCs. Additionally, the development of a theoretical model was explored in efforts to investigate how the geometry of ZnO nanowires affects the incident photon-to-current conversion efficiency of 1D ZnO nanowire-based N719-sensitized solar cells at the maximum absorption wavelength of 543 nm.

Dans les dernières années, le respect de l’environnement est devenu une des grandes préoccupations des clients du secteur automobile. Les constructeurs cherchent à réduire les émissions carbones de ses produits et les véhicules hybrides ou purement électriques apparaissent comme une alternative viable aux véhicules thermiques. Un des éléments importants de la réussite de la commercialisation des véhicules électriques est la recharge de la batterie qui peut être effectuée par différents moyens, avec des chargeurs embarqués/débarqués, à domicile ou sur la voie-publique. Dans ce domaine un système de charge performant doit notamment être robuste vis-à-vis des contraintes extérieures( perturbations réseaux, impédances de ligne, charges de plusieurs véhicules en même temps), avoir un bon rendement entre la puissance puisée à la prise et celle délivrée à la batterie, maitriser les courants harmoniques rejetés sur le réseau électrique (respect des différentes contraintes réglementaires liées aux perturbations émises). Pour répondre à ces exigences les travaux de cette thèse proposent des commandes innovantes des convertisseurs de puissance contenus dans les chargeurs électriques. Dans un premier temps, la modélisation des convertisseurs de puissance est réalisée en moyenne à la période de commutation et en moyenne généralisée pour d´écrire le processus de génération des harmoniques des courants et tensions des convertisseurs. Des lois de commande non-linéaire fondées sur la théorie de stabilité au sens de Lyapunov sont proposées de fac¸on à induire un comportement en boucle fermée satisfaisant les exigences souhaitées pour les convertisseurs de puissance. La partie commande est complétée par une partie d’observation nécessaire pour l’estimation des signaux non-mesurés et pour l’extraction harmonique. Enfin dans la dernière partie de la thèse, les différentes stratégies de commande sont validées par rapport aux exigences via une co-simulation en reproduisant l’architecture de logiciel model in the loop utilisée dans l’industrie / In the last few years the question of respecting the environment became a central concern of car users. The electric cars respond to the public trend of reducing the toxic emissions of conventional cars. The success of electric cars depends on the charging of the batteries, charging done either at home or on the public domain.The charging system has to respond to the following performance criteria:-robustness to exterior constraints: network perturbations, line impedance, multiple simultaneous charging of vehicles.-a good efficiency for the power transfer between the received power and the power delivered to the battery.-respecting the power distributer constrains for network harmonic pollution.These three points impose the need for efficient control laws for the battery charger. In this context, the power converters (AC / DC - DC / DC) are key components in electrical chargers , an improved control law of these elements can provide a better level of performance for the charger.This work is a continuation of previous work that resulted in several theses with CIFRE funding, in collaboration with Renault in the context of the electric car (but not only):- From an industrial viewpoint, the doctoral student will draw on the expertise, experience and Renault's test facilities in the field of electric traction in the automotive transport.- From an academic point of view the work will benefit from the skills of the working group 'System control’ within the L2S laboratory, in the field of multi-physics modelling, design of control laws and optimization.Supervision will be provided by:- Emmanuel Godoy (Professor, HDR, advisor) and Dominique Beauvois (professor, co-director) of the academic point of view.- Pedro Kvieska (Engineer, Doctor, Ecole Centrale de Nantes) for industrial management within Renault.Objectives of the thesisThe first two years of thesis work will focus on methodological studies of dedicated control laws. During the third year the work will be focused on the implementation of the proposed architectures and control strategies by: implementing of the new control strategies as prototypes on test bench and on the transferability of the proposed control approaches.A big part of the last year will naturally be devoted to the writing of the doctoral thesis and the preparation of the defence.

Philosophiae Doctor - PhD (Chemistry) / Renewable energy has become the centrepiece of research in resolving the energy crisis. One of the forms of renewable energy is solar energy. This form of energy is costly to develop. Organic molecules are promising materials for the construction of next generation photovoltaic cells considering their advantage of lower cost compared to crystalline silicon that is currently used in solar cells. This forms the basis of this research, which focused on the synthesis and characterisation of poly(3- hexylthiophene) P3HT, stannum (Sn) nanoparticles and stannum-based bimetallic stannum-titanium (SnTi), stannum-chromium (SnCr) and stannum-vanadium (SnV) nanoparticles for the application in the construction of heterojunction photovoltaic cells (PVCs).

Electric Vehicles (EVs) are seen as one of the solutions to some of the world’s global current problems, such as global warming and air pollution, due to non-existent operational emissions and increased efficiency. There are multiple types of EVs, one of them being Battery Electric Vehicles (BEVs) which in most cases utilizes a Li-Ion battery pack as energy storage. Li-Ion batteries for EV applications are deemed to have reached End of Life (EoL) at 80%-70% of the battery’s initial energy capacity, the degradation is caused by calendar and cycle aging. Calendar aging is dependent on storage temperature and State of Charge (SoC), controlling these factors are therefore of importance when storing battery packs to minimize aging. Diagnostics of battery packs is also useful for determining second-life applications, State of Health (SoH) or other future usage. AFRY has therefore an interest in developing a product that would enable diagnostics and charging/discharging of off-vehicle battery packs, as regular chargers and tools are not compatible with battery packs separated from its vehicle. This thesis is a part of a project to develop a product that enables diagnostics and charging/discharging for different types off-vehicle battery packs. Due to time limitation of the thesis work this report focuses on the hardware design of the Power Conversion Module (PCM) from a charging/discharging perspective. This thesis project will propose a theoretical PCM from received requirements and choose appropriate components for this subsystemfrom a charging/discharging perspective. The design requirements were gathered through interviews, archive analysis and literature studies and argued for. This to achieve an understanding of the requirements that the system design needs to fulfill. A system design proposal of the PCM was presented and a component analysis of the included components was conducted. The proposed solution should in theory enable charging/discharging of battery packs, but further work and studies needs to be performed to validate the results in practice. Some calculations and variables were inferredwith the help of discussions, due to lack of information and time. The goal of the thesis was fulfilled, and the wider project objective was partially fulfilled within the boundaries of this thesis project.

Fossil fuel consumption throughout the world is drawing attention to the need for alternative energy sources to provide for the large demand for energy. It is becoming more apparent everyday that fossil fuels are unreliable sources of energy due to the volatile pricing of such commodities as well as the toll that these energy sources take on the environment. Fossil fuels are non-renewable sources of energy that when burned to create energy produce bi-products that are extremely harmful to the global environment. Today, renewable energy sources such as wind and solar energy are playing larger roles as sources of electricity and are providing new jobs as well as research opportunities both in academia and in industry. It is for this reason that wind turbine energy harvesting is the topic of this thesis and how the efficiency of wind turbine power conversion systems can be improved to become a more viable source of energy. Large wind turbines, along with their power conversion electronics, exist today for the sole purpose of serving a large population of consumers with "green" electricity. Unfortunately, systems designed for low power wind turbines do not utilize advanced methods of maximizing energy draw from wind turbines both from hardware and software point of views. This theses is presents a method of efficient energy extraction and conversion from low power wind turbines to charge lead ac id batteries.