Η παρούσα διπλωματική εργασία πραγματεύεται τη μελέτη μίας διάταξης φωτοβολταϊκών πλαισίων εναλλασσόμενου ρεύματος (AC-PV module) και τη σύνδεση αυτής στο δίκτυο χαμηλής τάσης. Επιπρόσθετα πραγματεύεται την κατασκευή του μονοφασικού αντιστροφέα που ενσωματώνεται στην εν λόγω τοπολογία. Η εργασία αυτή εκπονήθηκε στο Εργαστήριο Ηλεκτρομηχανικής Μετατροπής Ενέργειας του Τμήματος Ηλεκτρολόγων Μηχανικών και Τεχνολογίας Υπολογιστών της Πολυτεχνικής Σχολής του Πανεπιστημίου Πατρών. Απώτερος σκοπός της εργασίας είναι η συνολική κατασκευή μίας διάταξης δύο βαθμίδων για τη διασύνδεση ενός φωτοβολταϊκού πλαισίου (Φ/Β) με το δίκτυο χαμηλής τάσης. Οι διατάξεις αυτές περιλαμβάνουν μια πρώτη βαθμίδα ανύψωσης της τάσης του Φ/Β πλαισίου και μια δεύτερη βαθμίδα που μετατρέπει τη συνεχή τάση σε εναλλασσόμενη (αντίστροφέας) και παράγει ρεύμα συμφασικό με την τάση του δικτύου (μοναδιαίος συντελεστής ισχύος). Αρχικά παραθέτουμε συγκρίνουμε τις τεχνολογίες διασύνδεσης Φ/Β στο δίκτυο χαμηλής τάσης στοχεύοντας στο να εντάξουμε ομαλά τον αναγνώστη στην υπό μελέτη τοπολογία. Στη συνέχεια παραθέτουμε μια βήμα προς βήμα θεωρητική ανάλυση όλων των εμπλεκομένων μονάδων της τοπολογίας. Πιο συγκεκριμένα πέραν της ανάλυσης των φωτοβολταικών χαρακτηριστικών, συγκρίνουμε και προσομοιώνουμε δύο τοπολογίες μετατροπέων συνεχούς τάσης σε συνεχή (boost και flyback). Επιπρόσθετα μελετούμε και προσομοιώνουμε τη μέθοδο παλμοδότησης του μονοφασικού αντιστροφέα, που είναι γνωστή υπό τον όρο "Ημιτονοειδής Διαμόρφωση του Εύρους Παλμών" (sPWM). Επόμενο βήμα αποτέλεσε η λεπτομερής διαστασιολόγηση ολόκληρου τού υπό μελέτη συστήματος και η μετέπειτα προσομοίωση της κάθε μονάδας του ξεχωριστά. Αφού διασφαλίσουμε ότι οι αυτοτελείς μοντελοποιημένες μονάδες λειτουργούν με επιτυχία προχωρούμε στην προσομοίωση της πλήρους διάταξης τόσο απουσία κλειστού βρόχου ελέγχου όσο και παρουσία αυτού. Τέλος αναλύουμε τα τεχνικά χαρακτηριστικά του αντιστροφέα που κατασκευάστηκε, καθώς και των κυκλωμάτων από τα οποία αποτελείται. και περιγράφουμε τη διαδικασία παραγωγής του κώδικα προγραμματισμού του μικροελεγκτή. Παράλληλα παραθέτουμε παλμογραφήματα και μετρήσεις που προέκυψαν από τα πειράματα που διενεργήσαμε μετά την ολοκλήρωση της κατασκευής σε εργαστηριακό περιβάλλον. / Analysis and practical implementation of a two stage topology for connection between PV modules and the common grid.

O objetivo principal deste trabalho é avaliar a efetividade da previsão de geração de energia elétrica realizada por meio de simulação de um sistema fotovoltaico integrado por módulos de diferentes características, dispostos em série e conectados à rede de distribuição, sem inversor. Para isto foi utilizado o programa Crearray, desenvolvido no Laboratório de Energia Solar da UFRGS, que permite determinar o ponto de polarização do arranjo e comparar com dados medidos experimentalmente. Foi montado um arranjo fotovoltaico integrado com módulos de diferentes características conectados à rede de distribuição por meio de um inversor. A curva característica de cada um dos módulos foi determinada por ensaio em um simulador. Os dados da curva permitiram determinar os parâmetros dos modelos utilizados no programa Crearray. Para avaliar o funcionamento do programa os dados de tensão em corrente contínua foram inseridos no software e as respectivas correntes foram calculadas. Os valores de corrente calculados e os valores medidos mostraram a eficiência do programa em calcular a curva característica para diferentes condições de irradiância e de temperatura. Utilizando o mesmo programa encontrou-se o ponto de polarização do arranjo ao longo do tempo para o ponto de máxima potência e, desta forma, também a corrente e a potência máxima do lado de corrente contínua do sistema. Na comparação desta potência máxima teórica com a potência efetivamente medida no lado de corrente contínua do sistema, pôde-se constatar que nem sempre o inversor consegue determinar a tensão exata para estabelecer a potência máxima. Na comparação dos dados medidos e simulados observa-se concordância. Da comparação dos valores em horários sem interferência de sombras, foi obtida uma medição da eficiência do seguidor de máxima potência do inversor, em modo dinâmico. Observando os dados adquiridos também foi estimada a eficiência dinâmica de conversão do inversor para um dia. / The main objective of this dissertation is to confirm the forecast of electricity production through the simulation of a photovoltaic system. Such system is composed by modules with different characteristics, arranged in series and connected to the distribution network. The simulation was performed with the help of Crearray, a computer program developed at the Solar Energy Laboratory of UFRGS, which determines the bias point of the array and compares it with experimentally measured data. A photovoltaic array, constituted by modules with different characteristics, was assembled and connected to the distribution network through an inverter. The characteristic curve of each module was previously determined in a solar simulator test. The curve data was used to evaluate the parameters of the curve models used by Crearray software. To verify the correct operation of the program, the DC voltage data was entered to the software and the related current was calculated. The comparison between calculated and measured current values showed the Crearray ability to calculate the characteristic curve for different conditions of irradiance and temperature. Furthermore, the program was used to calculate the maximum power point of the array along the time and thus the delivered DC power. Comparing this theoretical maximum power with the power actually measured at the DC side of the system, it was verified that the inverter sometimes was not able to determine the correct bias voltage to extract the maximum power. Comparison of measured and simulated data showed an excellent concordance, except for certain times when there was shading on the reference cell. Comparing the values over periods without the interference of shadows, it was possible to estimate the MPPT efficiency of the inverter under dynamic mode. Analyzing the acquired data was also possible to estimate the inverter dynamic conversion efficiency for a day.

O objetivo principal deste trabalho é avaliar a efetividade da previsão de geração de energia elétrica realizada por meio de simulação de um sistema fotovoltaico integrado por módulos de diferentes características, dispostos em série e conectados à rede de distribuição, sem inversor. Para isto foi utilizado o programa Crearray, desenvolvido no Laboratório de Energia Solar da UFRGS, que permite determinar o ponto de polarização do arranjo e comparar com dados medidos experimentalmente. Foi montado um arranjo fotovoltaico integrado com módulos de diferentes características conectados à rede de distribuição por meio de um inversor. A curva característica de cada um dos módulos foi determinada por ensaio em um simulador. Os dados da curva permitiram determinar os parâmetros dos modelos utilizados no programa Crearray. Para avaliar o funcionamento do programa os dados de tensão em corrente contínua foram inseridos no software e as respectivas correntes foram calculadas. Os valores de corrente calculados e os valores medidos mostraram a eficiência do programa em calcular a curva característica para diferentes condições de irradiância e de temperatura. Utilizando o mesmo programa encontrou-se o ponto de polarização do arranjo ao longo do tempo para o ponto de máxima potência e, desta forma, também a corrente e a potência máxima do lado de corrente contínua do sistema. Na comparação desta potência máxima teórica com a potência efetivamente medida no lado de corrente contínua do sistema, pôde-se constatar que nem sempre o inversor consegue determinar a tensão exata para estabelecer a potência máxima. Na comparação dos dados medidos e simulados observa-se concordância. Da comparação dos valores em horários sem interferência de sombras, foi obtida uma medição da eficiência do seguidor de máxima potência do inversor, em modo dinâmico. Observando os dados adquiridos também foi estimada a eficiência dinâmica de conversão do inversor para um dia. / The main objective of this dissertation is to confirm the forecast of electricity production through the simulation of a photovoltaic system. Such system is composed by modules with different characteristics, arranged in series and connected to the distribution network. The simulation was performed with the help of Crearray, a computer program developed at the Solar Energy Laboratory of UFRGS, which determines the bias point of the array and compares it with experimentally measured data. A photovoltaic array, constituted by modules with different characteristics, was assembled and connected to the distribution network through an inverter. The characteristic curve of each module was previously determined in a solar simulator test. The curve data was used to evaluate the parameters of the curve models used by Crearray software. To verify the correct operation of the program, the DC voltage data was entered to the software and the related current was calculated. The comparison between calculated and measured current values showed the Crearray ability to calculate the characteristic curve for different conditions of irradiance and temperature. Furthermore, the program was used to calculate the maximum power point of the array along the time and thus the delivered DC power. Comparing this theoretical maximum power with the power actually measured at the DC side of the system, it was verified that the inverter sometimes was not able to determine the correct bias voltage to extract the maximum power. Comparison of measured and simulated data showed an excellent concordance, except for certain times when there was shading on the reference cell. Comparing the values over periods without the interference of shadows, it was possible to estimate the MPPT efficiency of the inverter under dynamic mode. Analyzing the acquired data was also possible to estimate the inverter dynamic conversion efficiency for a day.

Este trabalho buscou entender a situação da atividade de fabricação de módulos fotovoltaicos no Brasil com o objetivo de avaliar a possibilidade de estimular a indústria nacional e o uso dessa fonte alternativa mais acentuadamente. Para tanto, foi necessário analisar os benefícios energéticos e econômicos da cadeia de produção, além de entender o estado da arte atual de todo o processo. É um ramo industrial que está sendo implantado no Brasil e este estudo teve como objetivo obter informações relevantes dos problemas e facilidades que os empreendedores enfrentam, e quais são os custos e benefícios à sociedade em geral, inclusive para obtenção dos sistemas fotovoltaicos pelo consumidor final. O trabalho contém uma avaliação do estado da produção e utilização dos sistemas de energia solar fotovoltaica no mundo e o que ocorre no Brasil. Buscou-se conhecer as possíveis, e/ou mais relevantes, ações regulatórias e iniciativas da área privada para viabilizar este ramo industrial. São considerados os impactos da atividade em pauta, procurando mostrar as relações de custo-benefício em projetos de geração centralizada (Leilões de Energia de Reserva) e de geração distribuída. / This study aims to understand the status of the manufacturing activity of photovoltaic modules in Brazil to evaluate the possibility of stimulating the local production and its widespread use. It was necessary to evaluate the energetic and economic benefits of the production chain. In addition, the study focused the understanding of the current state of the art of the whole process. Photovoltaic solar energy is an industrial branch recently receiving impulse in Brazil. This study aims to obtain relevant information about the difficulties faced by the entrepreneurs and the benefits and costs to the society. The study assess the state of the production and use of solar PV systems in the world and what happens in Brazil. At this study, we sought to understand what are the possible, and/or more relevant, regulatory actions and private area initiatives to enable this industrial branch and its diffusion to the final consumers. The impacts of the related activity are considered, trying to show the cost-benefit relationship in centralized generation projects (Reserve Energy Auctions) and distributed generation.

O objetivo principal deste trabalho é avaliar a efetividade da previsão de geração de energia elétrica realizada por meio de simulação de um sistema fotovoltaico integrado por módulos de diferentes características, dispostos em série e conectados à rede de distribuição, sem inversor. Para isto foi utilizado o programa Crearray, desenvolvido no Laboratório de Energia Solar da UFRGS, que permite determinar o ponto de polarização do arranjo e comparar com dados medidos experimentalmente. Foi montado um arranjo fotovoltaico integrado com módulos de diferentes características conectados à rede de distribuição por meio de um inversor. A curva característica de cada um dos módulos foi determinada por ensaio em um simulador. Os dados da curva permitiram determinar os parâmetros dos modelos utilizados no programa Crearray. Para avaliar o funcionamento do programa os dados de tensão em corrente contínua foram inseridos no software e as respectivas correntes foram calculadas. Os valores de corrente calculados e os valores medidos mostraram a eficiência do programa em calcular a curva característica para diferentes condições de irradiância e de temperatura. Utilizando o mesmo programa encontrou-se o ponto de polarização do arranjo ao longo do tempo para o ponto de máxima potência e, desta forma, também a corrente e a potência máxima do lado de corrente contínua do sistema. Na comparação desta potência máxima teórica com a potência efetivamente medida no lado de corrente contínua do sistema, pôde-se constatar que nem sempre o inversor consegue determinar a tensão exata para estabelecer a potência máxima. Na comparação dos dados medidos e simulados observa-se concordância. Da comparação dos valores em horários sem interferência de sombras, foi obtida uma medição da eficiência do seguidor de máxima potência do inversor, em modo dinâmico. Observando os dados adquiridos também foi estimada a eficiência dinâmica de conversão do inversor para um dia. / The main objective of this dissertation is to confirm the forecast of electricity production through the simulation of a photovoltaic system. Such system is composed by modules with different characteristics, arranged in series and connected to the distribution network. The simulation was performed with the help of Crearray, a computer program developed at the Solar Energy Laboratory of UFRGS, which determines the bias point of the array and compares it with experimentally measured data. A photovoltaic array, constituted by modules with different characteristics, was assembled and connected to the distribution network through an inverter. The characteristic curve of each module was previously determined in a solar simulator test. The curve data was used to evaluate the parameters of the curve models used by Crearray software. To verify the correct operation of the program, the DC voltage data was entered to the software and the related current was calculated. The comparison between calculated and measured current values showed the Crearray ability to calculate the characteristic curve for different conditions of irradiance and temperature. Furthermore, the program was used to calculate the maximum power point of the array along the time and thus the delivered DC power. Comparing this theoretical maximum power with the power actually measured at the DC side of the system, it was verified that the inverter sometimes was not able to determine the correct bias voltage to extract the maximum power. Comparison of measured and simulated data showed an excellent concordance, except for certain times when there was shading on the reference cell. Comparing the values over periods without the interference of shadows, it was possible to estimate the MPPT efficiency of the inverter under dynamic mode. Analyzing the acquired data was also possible to estimate the inverter dynamic conversion efficiency for a day.

M. Tech. (Engineering, Electrical, Department Electronic Engineering, Faculty of Engineering and Technology), Vaal University of Technology / In order to facilitate sustainable development, it is necessary to further improve and increase the energy efficiency and use of renewable energy and its related technologies. The main limiting factors to the extensive use of photovoltaic (PV) modules include the high initial investment cost and the relatively low conversion efficiency. However, other factors, such as an increase in ambient temperature, exert a considerable negative influence on PV modules, with cell efficiencies decreasing as the cell’s operating temperature increases. Higher PV module surface temperatures mean lower output voltages and subsequent lower output power. Therefore, this dissertation focuses on optimizing the available output power from a PV module by investigating and controlling the effect that the PV module’s surface temperature exerts on the amount of electrical energy produced. A pilot study was conducted by using a PV module set to three different tilt angles with an orientation angle and temperature sensors placed at different points. This was done to determine temperature distribution on the PV module surfaces as well as identify which tilt angle produces the highest PV module surface temperature. The main study was designed to investigate the electrical performance of a PV module with different cooling systems (water and forced air) as against a referenced measurement (no cooling). The cooling systems will be switched on and off at specific time intervals with the help of an electronic timer circuit incorporating a PIC microcontroller. The pilot study was conducted for a 50 week period where the results indicated a direct correlation between temperature rise and voltage decrease. The PV module’s temperature is highest at a tilt angle of 16° during the day and lowest at night time. It further reveals that the PV module’s front and back surface temperature can be distinctly different, with the highest recorded values occurring at the back of the PV module. The main study was conducted for a period of 15 weeks with results indicating that the water cooling system resulted in an average higher output power of 49.6% when compared to the reference system (no cooling system). Recommendations are made that sufficient space should be included between the module frames and mounting structure to reduce high operating temperatures owing to poor air circulation.

A geração de energia solar fotovoltaica tem crescido anualmente em utilização. Com o aumento dos custos de geração de energia elétrica, fontes renováveis de energia como essa crescem em interesse, até mesmo em aplicações residenciais de microgeração. Este trabalho apresenta o projeto, construção e ensaios de um rastreador solar autônomo, com controle e aquisição de dados de sensoriamento baseado em sistemas embarcados totalmente projetados e produzidos no país, com o objetivo de se aumentar o ganho de energia elétrica gerada a partir de painéis solares de mercado. O projeto do firmware de controle e os algoritmos utilizados foram adaptados continuamente até se atingir os melhores resultados. Foi utilizado um painel solar comum de mercado para realizar os testes, e as placas de circuito impresso projetadas foram confeccionadas localmente. A tomada de dados em diferentes ensaios mostrou que o rastreamento solar de fato aumentou o ganho de energia elétrica com um painel solar comum de mercado, mesmo com alguns problemas a serem corrigidos em uma próxima pesquisa. Assim, a pesquisa realizada confirmou o ganho de energia elétrica para o painel solar escolhido. / Photovoltaic solar generators have grown annually in use. With the increase in electricity generation costs, renewable sources of energy like that grow in interest, even in residential microgeneration applications. This work presents the design, construction and testing of a standalone solar tracker, with control and acquisition of sensors data based on embedded systems totally designed and produced in the country, aiming to increase the power generated from retail solar panels. The firmware design and used algorithms have been continuously adapted to achieve the best results. It was used a standard solar panel to perform the tests, and the designed printed circuit boards were manufactured locally. The data taken in different tests showed that the solar tracking actually increased the power generated with a standard solar panel, even with some problems in the design that have to be corrected in a future implementation. So the project was validated and can be used, including microgeneration in ordinary houses.

A geração solar fotovoltaica em painéis de silício tem se destacado como uma maneira limpa e renovável de atender à demanda por energia elétrica. Este trabalho apresenta o projeto, construção e testes de um sistema autônomo para obtenção da curva IV e caracterização de painéis fotovoltaicos comerciais instalados em campo. Após um estudo do problema de medição de painéis solares, uma especificação da Solução foi concebida. Com base na especificação, foram realizados o projeto elétrico, a construção de protótipos, a escrita do software de medição e os testes de validação em laboratório. Para validação definitiva do hardware desenvolvido, foram realizados testes em campo utilizando um painel solar comercial. Após a tomada de dados e análise dos resultados, conclui-se que o dispositivo concebido atende aos requisitos especificados e cumpre sua proposta inicial. A metodologia empregada neste trabalho pode ser utilizada para geração de outros instrumentos com finalidade similar ou idêntica. / Photovoltaic solar generators, using silicon panels, have grown popular as a clean and renewable way to supply electrical energy. This work presents the project, construction and testing of an autonomous system for IV curve tracing and characterization of commercial photovoltaic panels deployed in the field. After a study how to properly measure solar panels, a Solution was put in a form of a specification. From specifications, the following phases took place: electrical project, prototype construction, software development and lab testing. To perform final validation of the developed hardware, a field test with a commercial solar panel was performed. After collecting and analyzing data from, it was concluded that the design fulfills the required specifications and intended goals. The methodology employed in this work and be utilized to generate other measuring instruments with similar or identical function.

Στην περιγραφόμενη διπλωματική εργασία μελετώνται τα αυτόνομα φωτοβολταϊκά συστήματα και γίνεται η μελέτη για την τροφοδότηση μιας αγροικίας στην περιοχή της Πάτρας. Τέτοια συστήματα αποτελούνται από φωτοβολταϊκά πλαίσια, συσσωρευτές και ηλεκτρονικές διατάξεις. Τα πλαίσια είναι αυτά που συλλέγουν την ηλιακή ακτινοβολία και μέσω ενός μηχανισμού, που λέγεται φωτοβολταϊκό φαινόμενο, την μετατρέπουν σε ηλεκτρική ενέργεια. Οι συσσωρευτές αποθηκεύουν ηλεκτρική ενέργεια, την οποία εκμεταλλευόμαστε όταν η ζήτηση είναι μεγαλύτερη από την παραγωγή. Οι ηλεκτρονικές διατάξεις, δηλαδή ο μετατροπέας τάσης και ο ελεγκτής φόρτισης, ευθύνονται για την μετατροπή της συνεχούς ισχύος σε εναλλασσόμενη καθώς, επίσης, και για την ομαλή λειτουργία του συστήματος. Αφού γίνει παρουσίαση όλης της θεωρίας και των μαθηματικών τύπων που απαιτούνται, γίνεται εφαρμογή τους μέσω του σχεδιασμού του κατάλληλου φωτοβολταϊκού συστήματος για την τροφοδότηση της αγροικίας. / The subject of this diploma thesis is the study of stand-alone photovoltaic systems. Such systems include photovoltaic modules, batteries, inverters and charge controllers as well. The photovoltaic modules collect solar energy and transform it into electrical energy via a mechanism that is called photovoltaic effect. Batteries storage electrical energy and are used when the electrical demand is greater than the energy generated by the modules. Inverters are used to convert DC power into AC power and charge controllers connect or disconnect the batteries from the system, as needed. After presenting the theory data required, a stand-alone photovoltaic system is designed so as to supply a country house.

Une cellule photovoltaïque organique (OPV) consiste en un empilement de couches minces et comporte une électrode transparente, constituée le plus souvent par une couche mince d’oxyde d’indium dopé à l’étain (ITO). Des matériaux alternatifs sans indium, déposables par voie liquide à l’air ambiant, et sur de grandes surfaces souples plus adaptées à la filière OPV, sont actuellement l’objet d’un grand nombre de recherches. Les nanofils d’argent (Ag NWs) représentent un sérieux candidat pour remplacer l’ITO et sont l’objet de ce travail de thèse. Une méthode de dépôt des Ag NWs par spray à air sur des substrats de PET a été développée en vue de réaliser des films conducteurs et transparents sur une grande surface souple. Puis ces électrodes transparentes ont été intégrées dans des cellules OPV sur substrat souple avec des rendements comparables à l’ITO. Les dépôts par voie liquide ont été privilégiés (spray-coating, Dr Blade), excepté pour l’électrode supérieure en argent, évaporée sous vide. Enfin les cellules ont été interconnectées en série pour former un module OPV, plus efficace en termes de puissance électrique délivrée. Une étude sur l’ablation sélective de couches de l’empilement OPV par laser est également présentée pour la fabrication de modules. / An organic photovoltaic (OPV) cell consists of a thin-layer stack which includes a transparent electrode, usually made of indium tin-doped oxide (ITO). Alternative, indium-free materials, deposited in air with a wet deposition process on large, flexible substrates that are more compatible with the OPV field are currently widely investigated. Silver nanowires (Ag NWs), which represent a serious candidate to replace ITO, are the subject of this thesis. In this work a method to deposit Ag NWs on PET substrates by air spray-coating has been developed : efficient patterned conductive and transparent coatings could be processed on a large, flexible substrate. This transparent electrode was then integrated in flexible and large area OPV cells, with efficiencies comparable to ITO. Wet deposition techniques were preferred except for the silver top electrode, evaporated under vacuum. OPV cells were eventually interconnected in series in order to make an OPV module, delivering a higher electrical output. A study on selective laser ablation of layers in the OPV stack is also shown towards module processing.