Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / This work proposes study and implementation of a DC/DC Z-source converter operating in continuous conduction mode (CCM); It is applied to a photovoltaic system connected to a DC microgrid; aiming to inject the electricity supplied from PV array; To this end; the PV array is connected to the input of Z-source converter; which rises from 167V to 400V and injects the output current at the DC bus; using maximum power point tracking techniques (MPPT); The prototype implemented in the laboratory was developed for 1;38 kW output power; with the possibility to be fed either by a DC current source or DC voltage source; which does not happen with traditional converters (Buck; Boost; etc); The average efficiency achieved yield of 94%; As for the electric power processing from renewable sources; two heuristic methods were tested: Perturbe and Observe (P&O) and Conductance Incremental (IC); The average efficiency of the prototype; using the P&O technique in tracking maximum power was 79;9%; while using the second technique (IC) the average efficiency was a 82;5% ; / O presente trabalho propÃe o estudo e a implementaÃÃo de um conversor CC/CC Z-source; operando em modo de conduÃÃo contÃnuo (MCC); O mesmo à aplicado em um sistema fotovoltaico interligado a uma microrede CC; objetivando injetar a energia elÃtrica fornecida a partir de arranjo fotovoltaico;Para tal; o arranjo fotovoltaico à conectado na entrada do conversor Z-source; que a eleva de 167V para 400V e injeta a corrente de saÃda no barramento CC de 400V; utilizando tÃcnicas de rastreamento do ponto de mÃxima potÃncia (MPPT); O protÃtipo implementado em laboratÃrio foi desenvolvido para uma potÃncia nominal de saÃda de 1;38 kW com possibilidade de ser alimentado tanto por uma fonte CC de corrente ou uma fonte CC de tensÃo; diferenciando-se dos conversores tradicionais (Buck; Boost; etc); O mesmo alcanÃou um rendimento mÃdio de 94%; Quanto ao processamento de energia elÃtrica a partir de fontes renovÃveis; foram testados dois mÃtodos heurÃsticos: Pertube e Observe (P&O) e CondutÃncia Incremental (IC); A eficiÃncia mÃdia do protÃtipo usando a tÃcnica P&O no rastreamento da mÃxima potÃncia foi de 79;9%; enquanto usando a segunda tÃcnica alcanÃou-se uma eficiÃncia de 82;5% ;

Orientador: Luiz Felipe Mendes de Moura / Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-03T22:37:08Z (GMT). No. of bitstreams: 1 Martins_PaulinoCutrim_M.pdf: 1004109 bytes, checksum: 4a5643b8de366648397d80e7bfc388da (MD5) Previous issue date: 2004 / Mestrado / Refrigeração e Condicionamento Ambiental / Mestre Profissional em Engenharia Mecanica

Les travaux effectués dans cette thèse portent sur les problématiques de couplage de centrales photovoltaïques sur les réseaux de distribution haute tension africains. Ces réseaux sont pour la plupart caractérisés par leur instabilité, leur faible maillage et leur faible puissance installée. Une première partie traite des caractéristiques des centrales photovoltaïques connectées au réseau Haute Tension et leurs interactions avec ce dernier. Une deuxième partie de la thèse est consacrée à la modélisation des systèmes électriques (réseaux électriques, systèmes photovoltaïques etc.). Une approche de modélisation du générateur photovoltaïque pour des centrales de grande puissance a été proposée. Un cluster PV de 500 kWc a été proposé et simulé et ses performances évaluées. Les dispositifs de commande utilisés dans le cluster proposé prennent en compte les contraintes techniques nécessaires au transfert optimal de puissance et de la qualité de la tension entre le générateur PV et le réseau électrique. En application, une centrale PV de 20 MWc a été modélisée et simulée. L’impact de sa connexion sur le réseau national du Burkina a été évalué sur le plan de la stabilité en tension tant en fonctionnement normal qu’en situation de dysfonctionnement. L’approche de la stratégie de raccordement des centrales PV et l’impact de la modularité de ces dernières ont été aussi analysés. / The research work performed in this thesis focuses on the problems of coupling photovoltaic power plants to the African high-voltage distribution environments. African power systems are mostly characterized by a high degree of instability, low meshed and low power installed networks. The first part of this work deals with photovoltaic power plants connected to the high-voltage grid, its general behaviors and its interactions with the grid. The second part is devoted to the modeling of electrical power systems included photovoltaic systems. A modeling approach of a photovoltaic generator for large power plant was proposed. A photovoltaic cluster of 500 kWp system is proposed and simulated, and its performance evaluated. The design of the control systems used in the proposed cluster has taken into account the technical requirements needed for optimal power transfer and good quality of the voltage at the point of common coupling. Furthermore, a 20 MWp power plant connected to the national grid of Burkina Faso has been modeled and simulated, and their interactions have been evaluated in terms of voltage steady-state stability both in normal operation and in the dysfunction state. The approach to the strategy in terms of connecting PV power plants, and the impact of using modular photovoltaic power plants has also been analyzed.

L’objectif de ce travail de thèse a été d’étudier une alternative à la cellule photovoltaïque à hétérojonction classique de silicium amorphe/cristallin avec un matériau (GaP) qui permettrait une amélioration de rendement grâce à ses propriétés optiques et électriques. L’étude du potentiel des hétérojonctions GaP/Si pour des applications PV nous a amené à étudier chacun des aspects critiques inhérents à leur réalisation. La préparation chimique de la surface des substrats et les mécanismes qui contrôlent la structuration de la surface de Si(100) ont été étudiés afin d’obtenir une surface de silicium mono-domaine (à marches diatomiques) et faiblement rugueuse par homoépitaxie (dépôts par UHV-CVD). Cette étude a été complétée par l’étude de l’influence de la préparation de surface (préparation chimique et homoépitaxie) du substrat sur la qualité cristalline du GaP déposé en deux étapes par MEE et MBE. La croissance de GaP par MEE a par la suite été effectuée sur des substrats de Si(100) ayant uniquement subi une préparation chimique de surface. Les paramètres de la séquence de croissances MEE ont été étudiés et ajustés afin d’optimiser la phase de nucléation du GaP. La qualité structurale des dépôts a été évaluée par des caractérisations par AFM et DRX. Les couches minces de faibles épaisseurs (20nm) présentent une faible rugosité de surface équivalente à une homoépitaxie et une fraction volumique de MTs inférieure à la limite de détection. La croissance MEE permet d’assurer une nucléation 2D. Cependant les caractérisations par TEM et STM révèlent la présence de parois d’antiphase. En parallèle, la simulation de structures HET GaP/Si (effectuée grâce au programme AFORS-HET) et la réalisation de diodes et de démonstrateurs cellules GaP/Si ont permis de démontrer les optimisations apportées par l’utilisation d’un émetteur de GaP. Ces composants ont été étudiés par caractérisations optiques et électriques. Nous avons constaté une limitation des performances due à la présence de pièges à l’interface et dans le volume. Ces différentes études ont donc permis d’identifier les verrous technologiques à lever pour exploiter pleinement les cellules à hétérojonctions GaP sur silicium afin d’obtenir des hauts rendements photovoltaïques. / The main objective of this thesis is to study an alternative to conventional amorphous/crystalline silicon heterojunction solar cell using gallium phosphide (GaP) as an emitter layer. This would allow a performance improvement because of its optical and electrical properties. The potential of GaP/Si heterojunction solar cells have been evaluated by studying each of the critical issues inherent to their fabrication process. The chemical preparation of the substrates surface and the mechanisms controling the structure of the Si (100) surface have been studied in order to obtain a single domain silicon surface (with diatomic steps) and slightly roughened by homoepitaxy (UHV-CVD). This work was completed by the study of the impact of surface preparation (chemical preparation and homoepitaxy) of the substrate on the crystalline quality of GaP deposited in two steps by MBE and MEE. The growth of GaP by MEE was subsequently carried out on Si(100) substrates having only undergone a chemical surface preparation. MEE growth sequence parameters were studied and adjusted to optimize GaP nucleation. The structural quality of the thin films was evaluated by AFM and XRD characterizations. Thin films of 20 nm have lower surface roughness equivalent to an homoepitaxy and a volume fraction of MTs below the detection limit. The MEE growth ensures a 2D nucleation. However, TEM and STM characterizations reveal the presence of antiphase boundaries. In parallel, simulations of the structure HET GaP/Si (with AFORS-HET) have been performed to evaluate the potential of the structure. First, diodes and demonstrator cells with GaP/Si junction have been fabricated and optically/electrically characterized. Limitations in performance due to the presence of traps at the interface and silicon volume degradation have been observed. All this work has allowed us to identify the technological issues to overcome in order to fully exploit the GaP/Si heterojunction cells to improve solar cell performance.

Electricity is a perishable commodity; once it is generated it needs to be consumed or stored. Electric energy storage provides both power and energy capacity. Power capacity applications reduce the need for generation, while energy capacity allows for energy consumption to be decoupled from generation. Previous research was done to develop an algorithm for determining the power (MW) and energy (MWh) capacities of a battery energy storage system (BESS) to mitigate the adverse impacts of high levels of photovoltaic (PV) generation. The algorithm used a flat feeder profile, and its performance was demonstrated on the equinoxes and solstices. Managing feeder power leads to fewer voltage fluctuations along the length of the feeder, potentially mitigating load management issues caused by variability of renewable generation and load profile. These issues include lighting flicker, compressor seizing, equipment shut-off, loss of motor torque, frequent transformer tap changes and even voltage collapse due to loss of reactive power support. The research described in this thesis builds on this algorithm by incorporating a smoothed feeder profile and testing it over an entire year. Incorporating a smoothing function reduces the requisite BESS energy capacity necessary to provide firming and shaping to accommodate the stochastic nature of PV. Specifically, this method is used to conduct a year-long study on a per second basis, as well as a one-minute basis, for a distribution feeder. Statistical analytical methods were performed to develop recommendations for appropriately sizing the BESS. This method may be used to determine the amount of PV generation that could be installed on a distribution feeder with a minimal investment in the BESS power and energy capacities that would be required to manage the distribution feeder power. Results are presented for PV penetration levels of 10%-50% of the distribution feeder capacity and show that the use of a smooth feeder profile reduces the required energy capacity by a minimum factor of 10 when compared to a flat feeder profile. Results indicated that it is sufficient to have a one-minute sampling rate, as it provides the necessary granularity to model cloud-induced fluctuations. This method can be applied to any distribution feeder where a load profile and a PV profile are available.

The performance of photovoltaic (PV) modules in terms of their ability to convert incident photon to electrical energy (efficiency) depends mostly on the spectral distribution of incident radiation from the sun. The incident spectrum finally perceived by the module depends strongly on the composition of the medium in which it has traveled. The composition of the earth’s atmosphere, which includes, amongst others, water vapour, gases such as carbon dioxide and oxygen, absorbs or scatters some of the sunlight. The incident solar spectrum is also modified by the diffuse aspect of radiation from the sky which strongly depends on aerosol concentration, cloudiness and local reflection of the earth’s surface. Although it is well known that the changes in outdoor spectrum affect device performance, little work has been conducted to support this theory. This is probably due to lack of spectral data or in certain instances where data is available, little knowledge of interpreting that data. The outdoor spectral data that one obtains in the field does not come clearly for just simple interpretation. Different analytical interpretation procedures have been proposed, all trying to explain and quantify the spectral influence on PV devices. In this study an assessment methodology for evaluating the effects of outdoor spectra on device performance parameters during the course of the day, seasons and or cloudy cover has been developed. The methodology consists of developing a device dependant concept, Weighted Useful Fraction (WUF) using the outdoor measured spectral data. For measuring PV module’s performance parameters, a current-voltage (I-V) tester was developed in order to monitor the performance of six different module technologies. The Gaussian distribution was used to interpret the data. For hot-spot analysis, different techniques were used, which include Infrared thermographic technique for identifying the hot-spots in the solar cells, SEM and EDX techniques. The AES technique was also used in order to identify other elements at hot-spots sites that could not be detected by the EDX technique. iii Results obtained indicate that multicrystalline modules performance is affected by the changes in the outdoor spectrum during summer or winter seasons. The modules prefer a spectrum characterized by WUF = 0.809 during summer season. This spectrum corresponds to AM 2.19 which is different from AM 1.5 used for device ratings. In winter, the mc-Si module’s WUF (0.7125) peaks at 13h00 at a value corresponding to AM 1.83. Although these devices have a wider wavelength range, they respond differently in real outdoor environment. Results for mono – Si module showed that the device performs best at WUF = 0.6457 which corresponds to AM 1.83 during summer season, while it operates optimally under a winter spectrum indicated by WUF of 0.5691 (AM2.58). The seasonal changes resulted in the shift in WUF during day time corresponding to the “preferred” spectrum. This shift indicates that these devices should be rated using AM values that correspond to the WUF values under which the device operates optimally. For poly-Si, it was also observed the WUF values are lower than the other two crystalline-Si counterparts. The pc-Si was observed to prefer a lower AM value indicated by WUF = 0.5813 during winter season while for summer it prefers a spectrum characterized by WUF = 0.5541 at AM 3.36. The performance of the single junction a-Si module degraded by 67 percent after an initial outdoor exposure of 16 kWh/m² while the HIT module did not exhibit the initial degradation regardless of their similarities in material composition. It was established that the WUF before degradation peaks at 15h00 at a value of 0.7130 corresponding to AM 4.50 while the WUF after degradation “prefers” the spectrum (WUF = 0.6578) experienced at 15h30 corresponding to AM value of 5.57. Comparing the before and after degradation scenarios of a-Si:H, it was observed that the device spends less time under the red spectrum which implies that the device “prefers” a full spectrum to operate optimally. The degradation of a-Si:H device revealed that the device spectral response was also shifted by a 7.7 percent after degradation. A higher percentage difference (61.8 percent) for spectral range for the HIT module is observed, but with no effects on device parameters. Seasonal changes (summer/winter) resulted in the outdoor spectrum of CuInSe2 to vary by WUF = 1.5 percent, which resulted in the decrease in Isc. This was ascertained by iv analyzing the percentage change in WUF and evaluating the corresponding change in Isc. The analysis showed that there was a large percentage difference of the module’s Isc as the outdoor spectrum changed during the course of the day. This confirmed that the 17 percent decrease in Isc was due to a WUF of 1.5 percent. In mc-Si solar cells used in this study, it was found that elemental composition across the entire solar cell was not homogenously distributed resulting in high concentration of transition metals which were detected at hot spot areas. The presence of transition metals causes hot-spot formation in crystalline solar cells. Although several transition elements exist at hot-spot regions, the presence of oxygen, carbon, iron and platinum was detected in high concentrations. From this study, it is highly recommended that transition elements and oxygen must be minimized so as to increase the life expectancy of these devices and improve overall systems reliability

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The thesis deals with the following question: 1. What are the renewable resources? 2. Types of renewable resource. 3. European Union approach to renewable resources: targets 4. Czech Republic approach to renewable resources: targets 5. Investment evaluation: Photovoltaic power plant.

The implementation of photovoltaic power plants is the result of the collaboration between developers, investors, financing institutions, municipalities and general contractors. Investors make informed decisions based on expert evaluations of financial and nonfinancial criteria of projects. The investor provides equity capital for the project and the bank provides a loan usually in the amount of 70-80% of the total investment cost. The investor looks for the optimal solution for his investment and for the preparation and implementation of the project. To achieve this the investor needs to have a very good understanding of the country specifics where the project is located. During the construction works, outside bodies are part of the undertaking, especially law firms, expert technical supervisors and risk managers. The completed project is then valued using industry-standard methods and it becomes part of the investor's portfolio. New knowledge acquired during the development process is managed and applied to other projects.

This feasibility study examines the return on investment in the construction of photovoltaic power plant for family house following a legislation change in 2014.