Dissertations / Theses on the topic 'I-V curve'

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior
The IxV curves tracers for PV modules are used as a method of diagnosis of problems such as shadowing, faulty connections and degradation conditions. There are several types and brands tracers commercially available, but their costs are quite high in the Brazilian market due to the need to import. This thesis describes the development and validation of a IxV curve tracer for PV modules based on the electronic load method using MOSFET as load to the module. By appropriate variation of the MOSFET gate-source voltage signal was possible to acquire the points of voltage and current of the PV modules terminals. These points were recorded using a data acquisition board with PIC18F2550, which is controlled by a computer via a USB with a graphical interface to the user. This interface was developed in MATLAB software ensuring greater flexibility and functionality to the device. For PV module temperature measurements PT100 sensors were used and measurements of solar irradiance was used a pyranometer LP02 model Hukseflux Thermal Sensor manufacturer, these sensors were connected to a supervisory system consists of a PC and a programmable logic controller (PLC). The validation process was conducted by comparing the electrical parameters provided by the developed tracer and the commercial tracer MINI-KLA. From this comparison an error was generated for each parameter. Three PV modules of different electrical characteristics (20 Wp, 87 Wp e 160 Wp) were used and there was similarity between the curves of the developed tracer with the curves of the commercial tracer. The average of errors of the electrical parameters for the 3 PV modules was less than 5% at no shading conditions. In two conditions of shading, the IxV curves provided by the two tracers for the KC 85 T PV module were compared and it was observed in the first situation that the MINI-KLA tracer could characterize only partially the curve while the tracer developed could characterize the curve fully, in the second situation there was great similarity between the curves of the two tracers with maximum percentage difference in the electrical parameters equal to 5.41%.
Os traÃadores de curva IxV para mÃdulos FV sÃo utilizados como um mÃtodo de diagnÃstico de problemas como sombreamento, conexÃes defeituosas e condiÃÃes de degradaÃÃo. Existem diversos tipos e marcas de traÃadores disponibilizados comercialmente, mas seus custos sÃo bastante elevados no mercado brasileiro devido à necessidade de importaÃÃo. A presente dissertaÃÃo aborda o desenvolvimento e a validaÃÃo de um traÃador de curva IxV para mÃdulos FV baseado no mÃtodo de carga eletrÃnica com uso de MOSFET como carga para o mÃdulo. AtravÃs da adequada variaÃÃo do sinal de tensÃo de gate-source do MOSFET foi possÃvel adquirir os pontos de tensÃo e corrente nos terminais dos mÃdulos FV. Estes pontos foram registrados atravÃs de uma placa de aquisiÃÃo de dados, com PIC18F2550, que à controlada via USB por um computador com uma interface grÃfica para usuÃrio. Esta interface foi desenvolvida com o software MATLAB, garantindo maior flexibilidade e funcionalidade ao dispositivo. Para mediÃÃes da temperatura do mÃdulo FV foram utilizados sensores PT100 e para as mediÃÃes de irradiÃncia solar foi utilizado um piranÃmetro modelo LP02 do fabricante Hukseflux Thermal Sensor; estes sensores foram utilizados atravÃs de um sistema supervisÃrio composto por um PC e um controlador lÃgico programÃvel (CLP). O processo de validaÃÃo foi realizado atravÃs da comparaÃÃo dos parÃmetros elÃtricos fornecidos pelo traÃador desenvolvido e pelo traÃador comercial MINI-KLA. A partir desta comparaÃÃo um erro foi gerado para cada parÃmetro. Foram utilizados 3 mÃdulos FV de diferentes caracterÃsticas elÃtricas (20 Wp, 87 Wp e 160 Wp) e observou-se proximidade entre as curvas do traÃador desenvolvido com as curvas do traÃador comercial. A mÃdia dos erros para os 3 mÃdulos relativa aos parÃmetros elÃtricos obtidos com os 2 traÃadores foi inferior a 5% em condiÃÃes sem sombreamento. Em duas condiÃÃes de sombreamento, as curvas IxV fornecidas pelos dois traÃadores relativas ao mÃdulo FV KC 85 T foram comparadas e observou-se na primeira situaÃÃo que o traÃador MINI-KLA conseguiu caracterizar apenas parcialmente a curva enquanto que o traÃador desenvolvido conseguiu caracterizar a curva totalmente, na segunda situaÃÃo observou-se grande proximidade entre as curvas dos dois traÃadores com diferenÃa percentual mÃxima nos parÃmetros elÃtricos igual a 5,41%.

The subject of my thesis is a variant I/57 in the section Semetín-Bystřička. The proposed route of communication, was part of an existing communications maintained for its full utilization. Were drawn four proposed variants of the solution, 3 variants are trying their best to use existing communication Jablůnka the village, one suggested option B that leads outside the existing road.

O presente trabalho consiste no desenvolvimento de um módulo electrónico de baixo custo, capaz de adquirir e traçar as curvas I-V (corrente versus tensão) de módulos fotovoltaicos, assim como medir outras grandezas utilizadas no diagnóstico de degradação, nomeadamente, tensão em circuito aberto, corrente de curto-circuito, radiação solar e temperatura. Numa primeira fase do trabalho decorrida no IPB, foram implementadas/testadas algumas montagens electrónicas com vista a verificar as possibilidades de implementação e validar a que melhor se coadunava para a implementação prática. De seguida, já no Ciemat, tomou-se conhecimento das distintas técnicas e procedimentos do Laboratório de Energia Solar Fotovoltaica para a realização de ensaios e medidas em módulos fotovoltaicos. Após a consolidação de conhecimentos, foi projectado, desenhado e construído um traçador de curvas I-V cumprindo os requisitos propostos, ou seja, de baixo custo e configuração simples. O módulo electrónico construído foi baseado na carga de um condensador de potência, uma carta de aquisição de dados e um comutador para duas opções de medida: módulos fotovoltaicos “convencionais” (10 A, 50 V) e módulos fotovoltaicos de lâmina delgada (2 A, 110 V). This work is based on the development of a low cost electronic module, able of acquiring and trace IV curves (current versus voltage) of photovoltaic modules, as well as measuring other quantities of the degradation diagnose, particularly open circuit voltage, current short circuit, radiation and temperature. On a former phase of this work, which took place at IPB, there were implemented/tested some electronic montages in order to verify the implementation possibilities and validate which suits better for the practical implementation. On a second phase, taking place at CIEMAT, there were acknowledged several techniques and procedures of the Photovoltaic Energy Laboratory for the execution of tests and measures on photovoltaic modules. After knowledge consolidation, it was projected, designed and built an IV tracer, according to the proposed requisites, as so, low cost and simple configuration. The electronic module built on his project, was based on the load of a power condenser, on data acquisition hardware and a two-measuring switch: conventional photovoltaic modules (10 A, 50 V), and thin-blade photovoltaic modules (2 A, 110 V).

Magíster en Ciencias de la Ingeniería, Mención Eléctrica. Ingeniera Civil Eléctrica
El desierto de Atacama anida abundantes recursos naturales en sus 105.000 km2. Éste contiene las reservas más grandes de cobre y productos no metálicos del mundo, y los niveles mundiales de irradiancia más altos con un promedio anual de 2.500 kWh/m2 de Irradiancia Horizontal Global (GHI), 3.500 kWh/m2 de Irradiancia Directa Normal (DNI) y de 4.000 horas de sol. A pesar de tener muchas ventajas, también presenta desafíos importantes. A modo de ejemplo, se sabe que las dosis anuales de UV-B en el desierto de Atacama son cerca de un 40% más altas que las típicas del norte de África. Esta parte del espectro no genera más electricidad y podría perjudicar los materiales utilizados en los módulos fotovoltaicos (FV), reduciendo su vida útil. Por ende, un módulo vidrio/vidrio (bifacial) especialmente diseñado para nuestro desierto es parte de la I+D+i FV en el programa solar nacional. Para materiales y diseños de módulos FV ya existentes, datos acerca de observaciones sobre su degradación son variables en su nivel de detalle, consistencia, calidad y significancia estadística. Además, la información disponible acerca de fallas típicas de módulos FV instalados en el desierto de Atacama es escasa o inexistente. A partir del contexto señalado, el objetivo principal de esta tesis es diseñar e implementar una herramienta de inspección para recolectar datos (IDCTool, por sus siglas en inglés), con el fin de evaluar módulos FV que operan en condiciones climáticas desérticas y caracterizarlos. La propuesta se basa en el estado-del-arte de prácticas en terreno junto con la definición de un conglomerado de criterios para su uso en soluciones FV de baja escala. Su implementación incluye el desarrollo de una encuesta, equipos y herramientas; y procedimientos para pruebas en terreno y análisis. IDCTool fue usada para una campaña en la región de Arica y Parinacota, la que es representativa de climas desérticos. Los resultados obtenidos fueron analizados de acuerdo con el procedimiento propuesto. La propuesta metodológica de esta tesis se validó mediante la campaña de Arica. Los 15 sitios visitados (comuna de Arica) fueron clasificados en 4 zonas: la costa, el centro de la ciudad, el valle y el desierto. Durante la campaña se inspeccionó 95 módulos FV, de los cuales se encontraron 9 fabricantes distintos. Los módulos operando por más tiempo llevaban 13 años instalados, los más nuevos llevaban 2 años. Todos los módulos inspeccionados estaban compuestos por un vidrio frontal, una lámina polimérica trasera y marco de aluminio. Según los resultados, no se presentaron fallas en cables, conectores ni celdas solares. La falla más típica fue el efecto soiling con 52 casos de soiling ligero y 39 de soiling fuerte. Otras fallas típicas fueron corrosión menor de la puesta a tierra (18 casos) y corrosión del marco (12 casos). En relación a los parámetros eléctricos, la mayor degradación se observó en la potencia nominal con una caída máxima de 39,08% y una caída promedio de 13,19±6,22%. En relación a la diferencia de temperatura de operación de los módulos FV con respecto a la temperatura ambiente, la mayor diferencia fue 24,45°C con un promedio de 11,67°C. Se encontró que la celda más caliente de todo el universo inspeccionado operaba a 99,4°C, mientras que en promedio las celdas más calientes operaban a 64,0°C. Con respecto a las anormalidades térmicas, se encontraron 2 módulos FV con patrón PID y 12 módulos mostraron celdas homogéneamente muy calientes. El trabajo realizado indica que la herramienta desarrollada, incluyendo la metodología para el análisis, entrega datos en formato estándar capaces de caracterizar módulos FV. Los datos analizados fueron estudiados mediante sus tendencias con el uso de herramientas estadísticas. Por ende, fue posible realizar conclusiones y recomendaciones. A pesar de esto, y debido a la falta de módulos inspeccionados, los fenómenos encontrados durante la campaña no pueden ser generalizados. En efecto, nuestro análisis no está validado por evidencia estadística sólida. En este contexto, el desarrollo de una base de datos significativa, mediante el uso de la IDCTool, será el mejor conjunto de datos como punto de partida para comenzar a hacer recomendaciones concluyentes para desarrollos en el ámbito FV.

O presente trabalho apresenta o desenvolvimento de um traçador de curvas I-V para aplicação em arranjos fotovoltaicos a serem medidos em campo. Este sistema utiliza a carga capacitiva como método de polarização do gerador fotovoltaico sendo o chaveamento realizado por transistores bipolares de porta isolada (IGBT). Para controle do chaveamento dos IGBTs e aquisição dos pontos I-V, a placa Arduino foi aplicada demostrando-se adequada para a proposta. Para tanto foi escrito, em uma variação da linguagem de programação C++, o programa de controle desta placa. Foram construídos circuitos auxiliares de amplificação de sinal para realizar as medidas de corrente e de irradiância, sendo nestes casos, usados como sensores um resistor shunt e uma célula de referência calibrada, respectivamente. Para medida da temperatura foi aplicado o sensor de temperatura LM35 que apresentou resultados satisfatórios. Os dados adquiridos pela placa Arduino são salvos em um cartão de memória para posterior análise. A análise de incertezas foi realizada usando métodos estatísticos, onde foram determinados os erros sistemáticos e aleatórios para cada canal de medição. O protótipo construído foi aplicado no levantamento da curva I-V de um gerador fotovoltaico composto de uma série de 3 módulos instalada no terraço do prédio que abriga o simulador solar do Laboratório de Energia Solar da Universidade Federal do Rio Grande do Sul (LABSOL) e o seu resultado foi comparado com o sistema traçador de curvas do laboratório. O resultado, de maneira geral, foi satisfatório quando comparado com a medida a 2 fios pelo sistema do LABSOL, mas apresentou um erro maior quando comparado à medida a 4 fios. Este protótipo também foi submetido a um teste para avaliar sua capacidade de apresentar a curva I-V de forma adequada quando são provocados defeitos na série de módulos. O resultado apresentado pelo protótipo se mostrou bastante semelhante ao do apresentado pelo sistema do LABSOL. De maneira geral, pode-se afirmar que o protótipo, baseado em seus resultados, mostrou-se adequado para aplicação em medidas em campo de curvas I-V de arranjos fotovoltaicos.
This work presents the development of an IV tracer for in field measurement of PV arrays. This system uses a capacitive load as a method for polarizing the photovoltaic generator, with the switching being performed by insulated gate bipolar transistors (IGBT). To control switching of the IGBTs and acquisition of the IV curve, an Arduino board was applied, and was proved to be adequate for this purpose. The Arduino board control program was written in a variation of C++ language. Auxiliary circuits for amplifying the signal were built to measure electric current and irradiance, being in such cases used as sensors a shunt resistor and a calibrated reference solar cell, respectively. For obtaining the temperature, the LM35 temperature sensor was employed, presenting satisfactory results. The data acquired by the Arduino board are saved on a memory stick for later analysis. The uncertainty analysis was performed by using statistical methods, in which the systematic and random errors for each measurement channel were determined. The assembled prototype was applied for measuring the IV curve of a photovoltaic generator composed of a string of 3 modules located on the roof of one of the buildings from Solar Energy Laboratory of the Federal University of Rio Grande do Sul (LABSOL) and its result was compared with the IV tracer used on the laboratory. The result was, generally, satisfactory when compared with the two-wire measurement by the laboratory’s system, but showed a larger error when compared with the four-wire measurement. This prototype was also submitted to a test to evaluate its capacity of adequately presenting the IV curve when defects are induced on the string. The result presented by the prototype was quite similar to that obtained from LABSOL’s system. In general, it is possible to affirm that the prototype, based on its results, proved to be adequate for in field measurement of photovoltaic arrays.

Nel corso della loro vita utile, gli impianti fotovoltaici sono soggetti ad un degrado continuo dei componenti con conseguente decremento della produzione attesa, nonché a guasti, avarie o malfunzionamenti. Per monitorare le prestazioni nel tempo e per individuare eventuali diminuzioni di performance, vengono utilizzate tecniche quali l’analisi dei dati di produzione e l’esecuzione di prove strumentali in campo. Data la carenza di procedure circa le tecniche sopra menzionate, sia nella modalità di esecuzione sia nella rappresentazione dei risultati, emersa dallo studio dello stato dell’arte, il principale obiettivo di questo lavoro è quello di definire un processo organico per indagare le performance d’impianto e per elaborare proposte di intervento atte ad incrementarne le prestazioni. A partire dalle analisi condotte sui dati provenienti da impianti fotovoltaici reali e dalle prove strumentali in campo, lo studio propone procedure per l’analisi dei di monitoraggio e per l’individuazione e l’esecuzione delle prove da svolgere e la successiva interpretazione e rappresentazione dei risultati. Inoltre, definisce proposte di intervento da mettere in atto per risolvere eventuali criticità emerse nelle fasi di indagine. In aggiunta, il presente lavoro ha perseguito due obiettivi parallelamente a quello principale sopra esposto. Il primo obiettivo ha riguardato l’esecuzione di “curve I-V” (corrente-tensione) su alcuni moduli fotovoltaici mediante l’impiego di un dispositivo per i flash test e l’individuazione della correlazione quantitativa tra alcuni tipici difetti riscontrabili con la termografia ad infrarossi su un modulo e il decremento di potenza associato. Il secondo obiettivo ha visto un focus all’accuratezza delle curve I-V attraverso il confronto tra i risultati delle misure in campo e quelli ottenuti in laboratorio attraverso l’impiego del flash-tester; la conclusione è la scarsa affidabilità delle curve I-V svolte in campo come strumento per valutare l’underperformance dell’impianto.
During their lifetime, photovoltaic plants are subject to a normal degradation of their components, and they are consequently characterized by decrease of the expected production. Techniques such as production data analysis and instrumental tests are performed in order to monitor performance over time and to identify power decrease. Examining the state of the art, a lack of procedures related to the abovementioned techniques, both in the execution mode and in the results representation, has emerged. The main aim of this work is to define an organic process to investigate the performance of photovoltaic plants and to elaborate intervention proposals in order to increase their production. Based on the analyses that have been performed on the data from real photovoltaic plants and instrumental tests, this work defines the procedures to analyze the data extracted from the monitoring systems and proposes the procedures to identify and perform the tests to be carried out and the subsequent interpretation and representation of the results. In addition, the present work has pursued two other objectives parallel to the main one described above. Using the I-V curves determined by means of an indoor solar flash test device, it has been possible to evaluate production loss associated to specific thermal defects that can be detected through infrared thermography on the photovoltaic modules. A specific focus was also dedicated to the accuracy of I-V curves through the comparison between the measurements that are performed in the field and those obtained in the laboratory by means of an indoor solar flash test device. This study has led to a relevant conclusion: the I-V curves, that are carried out in the field, are characterized by an inadequate reliability and they cannot be considered a valid technique to evaluate the underperformance of a photovoltaic plant.

Molecular electronics pursues the use of molecules as fundamental electronic components. The inherent properties of molecules such as nano-size, low cost, scalability, and self-assembly are seen by many as a perfect complement to conventional silicon electronics. Molecule based electronics has captured the attention of a broad cross section of the scientific community. In molecular electronic devices, the possibility of having channels that are just one atomic layer thick, is perhaps the most attractive feature that takes the attention to graphene.The conductivity, stability, uniformity, composition, and 2D nature of graphene make it an excellent material for electronic devices. In this thesis we focused on Zigzag Graphene NanoRibbon(ZGNR) as a transmission channel. Due to the importance of an accurate description of the quantum effects in the operation of graphene devices, a full-quantum transport model has been adopted: the electron dynamics has been described by Density Functional Theory(DFT) and transport has been solved within the formalism of Non-Equilibrium Green’s Functions (NEGF). Using DFT and NEGF methods, the transport properties of ZGNR and ZGNR doped with Si are studied by systematically computing the transmission spectrum. It is observed that Si barrier destroyed the electronic transport properties of ZGNR, an energy gap appeared for ZGNR, and variations from conductor to semiconductor are displayed. Its followed by a ZGNR grown on a SiO2 crystal substrate, while substituting the Graphene electrodes with the Gold ones, and its effect on transmission properties have been studied. Improvement in transmission properties observed due to the formation of C-O bonds between ZGNR and substrate that make the ZGNR corrugated. Finally, we modeled a nano-scale Field Effect Transistor by implementing a gate under SiO2 substrate. A very good I-ON/I-OFF ratio has been observed although the device thickness.

Les systèmes photovoltaïques (PV) sont régulièrement exposés à de nombreux défauts entraînant des pertes de production coûteuses. Le travail proposé dans cette thèse porte sur l’amélioration de l’efficacité énergétique d’un microgrid à courant continu en minimisant les pertes liées à l’apparition des défauts PV. D’abord, nous avons présenté un état de l’art sur les défauts les plus fréquents et les méthodes de leur diagnostic. L’analyse de la littérature nous a orienté vers le choix d’une approche de diagnostic pilotée par les données. Ensuite, la méthode de l’Analyse en Composantes Principales (ACP) a été proposée pour la détection et la classification du défaut d’ombrage pour un module PV de 250 Wc. Nous avons exploité dans un premier temps toute la courbe I(V) acquise en conditions climatiques réelles. Un taux de réussite minimal de classement de 87.38% est obtenu en phase d’apprentissage et un taux de 97% est obtenu en phase de test. En deuxième temps, nous avons appliqué l’ACP en utilisant seulement les coordonnées MPP pour la détection de l’ombrage. Les données sont discriminées avec un taux de classification de 100%. L’Analyse Linéaire Discriminante (ALD) a été optée pour la prédiction des classes des nouvelles mesures MPP. Finalement, une étude des effets de trois défauts typiques a été menée à l’échelle d’une centrale PV de 250 kWc. Elle s’est basée sur les courbes I(V) simulées en considérant plusieurs sévérités pour chaque défaut. La sensibilité de la courbe I(V) centrale a été notée pour la dégradation de contact entre les strings PV et pour le défaut d’ombrage partiel à partir de 10%. Le défaut de court-circuit des modules PV, pour toutes les sévérités simulées, affecte beaucoup plus les courbes I(V) des strings
Photovoltaic (PV) systems are frequently subjected to several faults leading to costly production losses. The proposed work focuses on the improvement of the energy efficiency of a DC micro-grid by minimizing the losses related to the occurrence of PV faults. First, we presented a state of the art on the most recurrent faults and their diagnosis methods. The literature review has led us to adopt a data-driven diagnosis approach. Then, the Principal Component Analysis (PCA) method was proposed for PV shading fault detection and classification for a PV module of 250 Wp. The PCA was first performed using the entire I(V) curve obtained under real climatic conditions. A minimum classification success rate of 87.38% is obtained in the training step and 97% is obtained in the validation step. PCA was then applied using only the MPP coordinates to detect the shading fault. The data is discriminated with a classification rate of 100%.Linear Discriminant Analysis (LDA) was opted to predict the new MPP outdoor measurements’classes. Finally, a faults effects analysis study was carried out for three typical faults on the scale of a PV array of 250 kWp. The study was based on the simulated I(V) curves, considering differents severities of each fault. The sensitivity of the I(V) curve of the whole PV plant was observed for both the contact degradation between PV strings and the partiel shading starting from a severity of 10%. The short-ciruit fault of the PV modules has considerably more effect on the strings’ I(V) curves

Dynamic I-V curves constitute a naturalistic approach to electrophysiological neuronal characterization. Instead of analyzing a cells response to simple current injections and waiting for the cell membrane to stabilize, a dynamic I-V curve is generated by injecting a more naturalistic, dynamic input and analyzing the membrane response over a prolonged period of time. While this data is inherently noisy, it can be averaged out over longer recordings to produce accurate and detailed information on the current-voltage relationship of the cell membrane. For a number of different striatal neurons, a comparison is made between membrane properties as determined through conventional methods, and those same parameters extracted from the dynamic I-V curve. These are not always in agreement, although for some parameters like the membrane resistance and capacitance, the correlation is strong enough to be statistically significant. Furthermore, the dynamic I-V curve allows estimation of membrane resistance over a wide voltage range, unlike the traditional method, yielding a better insight in the summed opening and closing of voltage-gated ion channels. When these extracted parameters are then applied in a refractory Exponential Integrate and Fire model, the model is able to accurately mimic the response of the real neuron with minimal computational complexity.
Dynamiska I-V-kurvor utgör en fysiologiskt relevant ansats för att elektrofysiologiskt karakterisera neuroner. Istället för att analysera en cells svar på enkla ströminjektioner och vänta på att cellmembranet stabiliseras så genereras en dynamisk I-V-kurva genom att injicera en mer naturtrogen dynamisk input och sedan analysera membransvaret över en längre tidsperiod. Trots att denna typ av data i grunden är brusig kan man genom medelvärdesbildning producera noggrann och detaljerad information om ström- spänningsrelationen för cellmembranet. En jämförelse har gjorts mellan ett antal olika striatala neuronertyper för embranegenskaper bestämda genom konventionella metoder och motsvarande parametrar extraherade från den dynamiska I-V-kurvan. Parameteröverenstämmelsen är inte alltid god, men för parametrar som membranresistans och membrankapacitans så är korrelationen ändå stark nog att bli statisktiskt signifikant. Vidare, den dynamiska I-V-kurvan ger också möjlighet att estimera membranresistansen över ett brett spänningsintervall, till skillnad mot traditionella metoder. Detta medger en bättre insikt i hur spänningsstyrda jonkanaler öppnar eller stänger. När de extraherade parametrarna tillämpas på en integrerande tröskelfyrningsmodell av refraktär exponentiell typ så kan modellen mycket noggrannt beskriva neuronens respons och detta med minimal beräkningskomplexitet.

Les piles à combustible se positionnent aujourd’hui comme une alternative technologique séduisante face aux solutions classiquement utilisées pour le stockage d’énergie. De par leur rendement de conversion en énergie électrique et leur haute densité énergétique, les grands acteurs du secteur aéronautique en voient une solution intéressante pour réduire l’impact environnemental des avions. C’est dans cette optique que s’inscrit la présente thèse, visant à contribuer au développement de méthodologies destinées au suivi de l’état de santé d’une pile à combustible à membrane échangeuse de protons (Proton Exchange Membrane Fuel Cell PEMFC). Il a été montré, dans un premier temps, que l’ensemble des constituants d’une pile était soumis à des contraintes pouvant engendrer des défaillances irréversibles ou des pertes de performances. Cette synthèse a permis de mettre en exergue la nécessité de disposer de méthodes de diagnostic permettant de suivre l’état de santé de la pile. Dans ce sens, des outils basés sur le principe de l’identification paramétrique ont été mis en avant. Il s’agit dans un premier temps de pouvoir, à partir de caractérisations expérimentales, être capable de mettre en œuvre une procédure appropriée permettant d’identifier les paramètres d’un modèle représentant au mieux le comportement du composant. Et dans un temps second, de construire par l’intermédiaire des paramètres identifiés des indicateurs (signatures) liés à l’état de santé de la pile. Dans le cadre de cette thèse, nous nous sommes intéressés plus particulièrement à deux types de prise d’informations : la courbe de polarisation (V-I), et la Spectroscopie d’Impédance Electrochimique (SIE). Il a été montré dans cette thèse, que seule l’exploitation conjointe de ces 2 types de mesures permet une caractérisation pertinente de l’état de santé de la pile. Deux modèles «couplés» ont été ainsi développés : un modèle quasi-statique dont les paramètres sont identifiés à partir de la courbe de polarisation et un modèle dynamique identifié à partir des données de la SIE. Il a été mis en avant dans le cadre de cette thèse, la nécessité de développer un modèle dynamique dit «sans a priori» dont la formulation peut varier au cours du temps. Ainsi, si des phénomènes liés à un changement de caractéristique apparaissent, la structure du modèle pourra s’adapter pour en permettre la prise en compte. Le processus global partant de la connaissance a priori jusqu’à l’identification des paramètres des modèles a été développé au cours des chapitres de cette thèse. Outre la bonne reproduction des données expérimentales et la séparation des pertes dans les domaines quasi-statique et dynamique, l’approche permet de percevoir certaines défaillances à travers les paramètres des modèles développés. La prise en compte du couplage statique-dynamique a fait apparaître la notion « d’impédance résiduelle ». En effet, un biais entre la pente locale de la courbe de polarisation et la résistance basse fréquence de la SIE est systématiquement observé. L’impédance résiduelle prise en compte dans la modélisation permet d’absorber ce décalage tout en garantissant une cohérence entre les mesures de la V-I et de la SIE. Une tentative d’explication des phénomènes physico-chimiques liés à cette impédance a également fait partie de l’ensemble des objectifs de cette thèse. D’un point de vue expérimental, l’idée du travail est dans un premier temps de générer des variations ciblées et maîtrisées du comportement de la pile et d’observer leurs impacts sur les paramètres identifiés. Pour ce faire, l’idée proposée est de travailler sur une mono-cellule dont la modification des composants est aisée. Le jeu de composants (membranes différentes, différents dosages en platine …) avait permis de mettre en évidence l’impact de chaque modification sur les données expérimentales et ainsi sur le modèle avant de tester la validité de l’approche sur des campagnes de vieillissement de stacks
Nowadays, Fuel cells (FCs) are considered as an attractive technological solution for energy storage. In addition to their high efficiency conversion to electrical energy and their high energy density, FCs are a potential candidate to reduce the environmental impact of aircrafts. The present PhD thesis can be located within this context, and especially contributes to the development of methodologies dedicated to the monitoring of the state of health (SoH) of Proton Exchange Membrane Fuel Cells (PEMFCs). FCs are submitted to ageing and various operating conditions leading to several failures or abnormal operation modes. Hence, there is a need to develop tools dedicated to the diagnosis and fuel cell ageing monitoring. One of reliable approaches used for the FC SoH monitoring is based on parametric identification of a model through experimental data. Widely used for the FC characterization, the polarization curve (V-I) and the Electrochemical Impedance Spectroscopy (EIS) coupled with a model describing the involved phenomena may provide further information about the FC SoH. Two models were thus developed: a quasi-static model whose parameters are identified from the polarization curve and a dynamic one identified from EIS data. The need to develop a dynamic model whose formulation may vary over time “without a priori” has been reported in this thesis. The original approach of this thesis is to consider conjointly both characterizations during all the proposed analysis process. This global strategy ensures the separation of the different fuel cell phenomena in the quasi-static and dynamic domains by introducing into each parametrization process (one for the quasi-static model and one for the dynamic model) parameters and/or laws stemming from the other part. The global process starting from the a priori knowledge until the identification of the models parameters was developed during the chapters of this thesis. In addition to the good reproduction of experimental data and the separation of the losses in both static and dynamic domains, the method makes it possible to monitor the FC SoH via the evolution of models parameters. The fact to take into account the coupling between quasi-static and dynamic models revealed the notion of a “residualimpedance”. This impedance makes it possible to overcome the recurrent experimental observation made by the daily users of EIS: there is a not-clearly explained difference between the low frequency resistance of the EIS and the slope of the polarization curve for a given currentndensity. Theoretically the two quantities have to tend towards the same value. In others words, a part of the impedance spectra is not clearly and easily exploitable to characterize fuel cell performance. This topic has been discussed in the literature in the last years. An attempt to explain physico-chemical phenomena related to this impedance is also a part of objectives of this thesis. From an experimental point of view, before applying this method to ageing monitoring, it was indeed necessary to “calibrate” it regarding its relative complexity. In this way, experiments with a single cell with different sets of internal components (different membrane thicknesses and different platinum loadings in the Active Layer (AL)) were achieved and analyzed by applying the proposed method. Therefore, the method was evaluated in the framework of three ageing campaigns carried out with three 1 kW PEM stacks

This thesis analyzes the design and performance of a photovoltaic (PV) emulator. With increasing interest in renewable energies, large amounts of money and effort are being put into research and development for photovoltaic systems. The larger interest in PV systems has increased demand for appropriate equipment with which to test PV systems. A photovoltaic emulator is a power supply with similar current and voltage characteristics as a PV panel. This work uses an existing power supply which is manipulated via Labview to emulate a photovoltaic panel. The emulator calculates a current-voltage (I-V) curve based on the user specified parameters of panel model, irradiance and temperature. When a load change occurs, the power supply changes its current and voltage to track the calculated I-V curve, so as to mimic a solar panel. Over 250 different solar panels at varying irradiances and temperatures are able to be accurately emulated. A PV emulator provides a controlled environment that is not affected by external factors such as temperature and weather. This allows repeatable conditions on which to test PV equipment, such as inverters, and provides a controlled environment to test an overall PV system.

LUNA, M. L. M. Desenvolvimento e validação de traçador de curva I x V para módulos fotovoltaicos. 2016. 126 f. Dissertação (Mestrado em Engenharia Elétrica) - Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2016.
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The IxV curves tracers for PV modules are used as a method of diagnosis of problems such as shadowing, faulty connections and degradation conditions. There are several types and brands tracers commercially available, but their costs are quite high in the Brazilian market due to the need to import. This thesis describes the development and validation of a IxV curve tracer for PV modules based on the electronic load method using MOSFET as load to the module. By appropriate variation of the MOSFET gate-source voltage signal was possible to acquire the points of voltage and current of the PV modules terminals. These points were recorded using a data acquisition board with PIC18F2550, which is controlled by a computer via a USB with a graphical interface to the user. This interface was developed in MATLAB software ensuring greater flexibility and functionality to the device. For PV module temperature measurements PT100 sensors were used and measurements of solar irradiance was used a pyranometer LP02 model Hukseflux Thermal Sensor manufacturer, these sensors were connected to a supervisory system consists of a PC and a programmable logic controller (PLC). The validation process was conducted by comparing the electrical parameters provided by the developed tracer and the commercial tracer MINI-KLA. From this comparison an error was generated for each parameter. Three PV modules of different electrical characteristics (20 Wp, 87 Wp e 160 Wp) were used and there was similarity between the curves of the developed tracer with the curves of the commercial tracer. The average of errors of the electrical parameters for the 3 PV modules was less than 5% at no shading conditions. In two conditions of shading, the IxV curves provided by the two tracers for the KC 85 T PV module were compared and it was observed in the first situation that the MINI-KLA tracer could characterize only partially the curve while the tracer developed could characterize the curve fully, in the second situation there was great similarity between the curves of the two tracers with maximum percentage difference in the electrical parameters equal to 5.41%.
Os traçadores de curva IxV para módulos FV são utilizados como um método de diagnóstico de problemas como sombreamento, conexões defeituosas e condições de degradação. Existem diversos tipos e marcas de traçadores disponibilizados comercialmente, mas seus custos são bastante elevados no mercado brasileiro devido à necessidade de importação. A presente dissertação aborda o desenvolvimento e a validação de um traçador de curva IxV para módulos FV baseado no método de carga eletrônica com uso de MOSFET como carga para o módulo. Através da adequada variação do sinal de tensão de gate-source do MOSFET foi possível adquirir os pontos de tensão e corrente nos terminais dos módulos FV. Estes pontos foram registrados através de uma placa de aquisição de dados, com PIC18F2550, que é controlada via USB por um computador com uma interface gráfica para usuário. Esta interface foi desenvolvida com o software MATLAB, garantindo maior flexibilidade e funcionalidade ao dispositivo. Para medições da temperatura do módulo FV foram utilizados sensores PT100 e para as medições de irradiância solar foi utilizado um piranômetro modelo LP02 do fabricante Hukseflux Thermal Sensor; estes sensores foram utilizados através de um sistema supervisório composto por um PC e um controlador lógico programável (CLP). O processo de validação foi realizado através da comparação dos parâmetros elétricos fornecidos pelo traçador desenvolvido e pelo traçador comercial MINI-KLA. A partir desta comparação um erro foi gerado para cada parâmetro. Foram utilizados 3 módulos FV de diferentes características elétricas (20 Wp, 87 Wp e 160 Wp) e observou-se proximidade entre as curvas do traçador desenvolvido com as curvas do traçador comercial. A média dos erros para os 3 módulos relativa aos parâmetros elétricos obtidos com os 2 traçadores foi inferior a 5% em condições sem sombreamento. Em duas condições de sombreamento, as curvas IxV fornecidas pelos dois traçadores relativas ao módulo FV KC 85 T foram comparadas e observou-se na primeira situação que o traçador MINI-KLA conseguiu caracterizar apenas parcialmente a curva enquanto que o traçador desenvolvido conseguiu caracterizar a curva totalmente, na segunda situação observou-se grande proximidade entre as curvas dos dois traçadores com diferença percentual máxima nos parâmetros elétricos igual a 5,41%.

Telemetry system, Optimisation, Sensoric networks, Smart Grid, Internet of Things, Sensors, Information security, Cryptography, Cryptography algorithms, Cryptosystem, Confidentiality, Integrity, Authentication, Data freshness, Non-Repudiation.

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Com a crescente demanda de energia elétrica ao redor do mundo, cada vez mais as fontes renováveis de energia vêm adquirindo espaço na matriz energética mundial. Nesse contexto, a energia fotovoltaica tem se destacado com altos índices de crescimento. Contudo, com a sua inserção faz-se necessário dispor de meios para avaliação do desempenho dos módulos fotovoltaicos, que pode ser realizado através da obtenção de sua curva característica I-V. A partir desta os parâmetros elétricos do módulo podem ser definidos, além de ser um indicador de possíveis falhas de fabricação, conexão ou possível sombreamento das células. Através do uso de simuladores solares, tornou-se mais rápido e confiável a obtenção de tal curva. No entanto, os altos custos de um simulador limitam o acesso a tal tipo de medição e, além disso, estes se restringem ao ensaio individual de módulos. Este trabalho busca avaliar uma metodologia para aquisição de curva I-V sob sol-real. Para isto, foram utilizadas duas cargas capacitivas e um módulo de referência para medida de irradiância e temperatura de operação do gerador fotovoltaico. As condições padrões de teste são obtidas por meio do que é descrito na norma IEC 60891. Módulos de tecnologia de silício foram testados e seus resultados confrontados com o do simulador solar presente no laboratório do GEDAE/UFPA. Os resultados obtidos indicam que dependendo da forma de cálculo e considerações acerca da medição da temperatura, esta pode ser uma metodologia adequada para medição de módulos fotovoltaicos em campo.
With the increasing demand for electricity worldwide, renewable energy sources are increasingly acquiring space in the world’s energy matrix. In this context, photovoltaic energy has stood out with high growth rates. However, it is necessary to have means to evaluate the performance of the photovoltaic modules. This can be done by means of its characteristic I-V curve, from which the module’s electrical parameters can be evaluated and used as an indicator of possible manufacturing faults, connection or shading. The use of solar simulators is a faster and more reliable to obtain such I-V curve. However, the high costs of a simulator limits access to such measurement, moreover, it is limited to measure only a single PV module. This work seeks to evaluate a methodology for the I-V curve acquisition under outdoor conditions by using two capacitive loads and a reference module as irradiance and temperature sensor. The standard test conditions are obtained by means of IEC 60891 procedures. Silicon technology modules were tested and their results were compared with indoor measurement, using the solar simulator located at GEDAE/UFPA solar laboratory. The results indicated that, depending on which calculation method and considerations related to temperature, this can be a suitable methodology for the measurement of a photovoltaic module.

Дисертаційна робота присвячена дослідженню морфології поверхні, структурно-фазового стану, оптичних та електрофізичних властивостей плівок ZnО та AlN, які отримані методами CVD, золь-гель та магнетронним розпиленням, проведено моделювання ВАХ СЕ на основі гетеропереходів n-ZnO/p-Si, n-ZnO/n-CdS/p-Si, n-ZnO/n-CdS/p-CIGS та визначені їх оптимальні фізичні та конструкційні характеристики. Проведено комплексне дослідження структури та субструктури полікристалічних плівок ZnO (ZnО:Al) та AlN залежно від фізико-технологічних умов їх конденсації. Встановлені режими отримання високоякісних конденсатів сполуки, придатних для використання у приладобудуванні. Вивчення електрофізичних властивостей шарів засвідчило, що при підвищенні легування плівок ZnO алюмінієм електропровідність плівок підвищувалася, а питомий опір відповідно зменшувався. Крім того, були чисельно виміряні основні електрофізичні властивості гетеропереходу n- ZnO/p-Si. Проведене чисельне моделювання основних електрофізичних характеристик гетеросистем на основі ZnO, був визначений коефіцієнт корисної дії для кожного з переходів. Вивчений вплив таких параметрів, як товщина поглинального шару, температура конденсації, тип поглинального шару, на поведінку вольт-амперних характеристик та квантового виходу гетеросистем. Було запропоновано та реалізовано моделювання гетеросистем n-ZnO/p-Si, n-ZnO/n-CdS/p-CIGS, n-ZnO/n-CdS/p-Si та n-ZnO/AlN/p-Si. Проведено порівняння модельних та експериментальних результатів. У результаті проведених експериментальних досліджень були визначені оптимальні режими отримання плівок ZnO та AlN, проведений структурно-фазовий аналіз, досліджені оптичні та електрофізичні властивості бездомішкових та легованих алюмінієм плівок оксиду цинку. При порівнянні експериментальних результатів та моделювання було визначено, що введення шару AlN у конструкцію СЕ покращує його характеристики. При цитуванні документа, використовуйте посилання http://essuir.sumdu.edu.ua/handle/123456789/29538
Диссертационная работа посвящена исследованию морфологии поверхности, структурно-фазового состояния, оптических и электрофизических свойств пленок ZnО и AlN, полученных методами CVD, золь-гель и магнетронным распылением. В работе также было проведено моделирование ВАХ солнечных элементов на основе оксида цинка. Проведено комплексное исследование, структуры и субструктуры поликристаллических пленок ZnO (ZnО:Al) и AlN в зависимости от физико-технологических условий их конденсации. Установлены режимы в температурном интервале от 573 до 773 К получения высококачественных конденсатов соединения. Показано, что при повышении температуры конденсации качество пленок заметно возрастает, улучшается их текстура, размер зерна и т. д. Кроме того, полученные в работе пленки ZnO имеют преимущественную текстуру роста (002). Исследование оптических свойств конденсатов показало, что при повышении концентрации алюминия в пленках существенно повышается оптическая ширина запрещенной зоны от 3,25 до 3,65 эВ, что в дальнейшем имеет перспективу применения данного соединения в качестве оконного слоя в тандемных солнечных элементах. Изучение электрофизических свойств слоев показало, что при повышении легирования пленок ZnO алюминием электропроводимость пленок повышалась, а удельное сопротивление соответственно уменьшалось. Кроме того, были численно измерены основные электрофизические свойства гетероперехода n-ZnO/p-Si, такие, как ток короткого замыкания, коэффициент заполнения, коэффициент полезного действия и т. д. Былопредложено и реализовано моделирование гетеросистем n-ZnO/p-Si, n-ZnO/n-CdS/p-CIGS, n-ZnO/n-CdS/p-Si и n-ZnO/AlN/p-Si. Проведено сравнение результаов моделтрования и экспериментальных результатов. Проведено численное моделирование основных электрофизических характеристик гетеросистем на основе ZnO, был определен коэффициент полезного действия для каждого из переходов. Изучено влияние таких параметров, как толщина поглощающего слоя, температура конденсации, тип поглощающего слоя на поведение вольт-амперных характеристик и квантового выхода гетеросистем. Проведено сравнение експериментальных результатов и результатов моделирования, проведена их корреляция. Установлено, что при повышении концентрации алюминия в пленках ZnO ширина запрещенной зоны материала значительно повышается, поэтому такие слои имеют перспективу использования в качестве оконных слоев солнечных элементов. При сравнении экспериментальных результатов и моделирования было определено, что внедрение слоя AlN в конструкцию СЭ улучшает его характеристики. Установлены режимы получения высококачественных конденсатов соединения, пригодных для использования в приборостроении. При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/29538
The thesis focuses on investigation of surface morphology, structural and phase state, optical and electro physical properties of ZnO and AlN films, obtained by the following methods: CVD, sol gel, and magnetron sputtering. In this work a modeling of current-voltage characteristics of solar cells based on ZnO was also carried out. In the work the complex investigation of structure and substructure features of polycrystalline ZnO (ZnO:Al) and AlN films was performed. There were determined the modes for obtainment of high-quality compound condensates that can be used in instrument engineering. It was shown that the increase of condensation temperature leads to the increase of film quality, improvement of their texture, grain size etc. Furthermore, the obtained ZnO films have the preferred growth texture (002). The investigation of film electro physical properties showed that the increase of doping of ZnO films by aluminum leads to increase of electrical conductivity, and to decrease of specific resistance. Furthermore, there were defined the basic elec-trophusical properties of n- ZnO/p-Si, hetero junction. During investigation there was proposed and realized a modeling of n-ZnO/p-Si, n-ZnO/n-CdS /p-CIGS, n-ZnO/n-CdS/p-Si and n-ZnO/AlN/p-Si hetero systems. The modeling and experimental results were compared. As a result of conducted experimental researches the optimal modes of ZnO and AlN film obtaining were determined, a structure-phase analysis was carried out, opti-cal and electro physical properties of pure and aluminum-doped ZnO films were in-vestigated. While comparing the modeling and experimental results there was deter-mined that implementation of AlN film into the solar cell structure improves its char-acteristics. It was defined, that the increase of Al concentration ZnO films leads to the increase of band gap of the material, so that such layers can be used as window layers in solar cells. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/29538

Magister Scientiae (Medical Bioscience) - MSc(MBS)
This study investigated the effects of TKIs on the growth and proliferation of MCF-7 breast carcinoma cells in culture. MCF-7 cells were exposed to different concentrations of TKIs alone and in combination with each other. Inhibition of cell growth by TKIs used individually occurred in a dose- and time-dependent manner. When EGFR Inhibitor I, EGFR Inhibitor II/BIBX1382 and the multi-specific EGFR/ErbB-2/ErB-4 Inhibitor were used in combination with each other at equimolar log dose concentrations, the combined effects on cell growth was significantly different to inhibitors used individually as reflected in a decreased EC50 (IC50) during combination treatments. Generally, for the combinations with DOX, CPL and the TKIs, synergistic as well as antagonistic effects were observed at isoeffective concentrations with resultant decreases in dose reduction indices (DRIs) implying greater efficacies with the respective combinations. In this study, conventional PCR was used to detect and illustrate the presence of the EGFR gene in the samples, while RT-qPCR was used to determine the mRNA expression levels of this gene in MCF-7 breast carcinoma cells

This work investigates the correlation of structural and photovoltaic properties of dyes used in dye-sensitized solar cells. Experimental methods, including ultraviolet-visible spectroscopy, fluorescence spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy are employed to study optical and electrochemical properties of dye molecules. Computational methods, including density functional theory and time-dependent density functional theory, are used to validate and predict the optical and electronic properties of dye molecules, in their isolated state and once embedded into a working electrode device environment that comprises a dye...TiO2 interface. The results chapters begin with the presentation of a series of quinodimethene dyes that are experimentally validated for their photovoltaic application, and associated computational studies reveal that an inner structural factor - a phenyl ring rotation occurring during the optical excitation process - leads to the competitive photovoltaic device performance of these dyes. Carbazole-based dyes are then systematically studied by computation, especially considering charge transfer paths and binding modes of these dyes on a titania surface. The theoretical models for the basic building block of this chemical family of dyes, known as MK-44, successfully support and explain structural discoveries from X-ray diffraction and reflectometry that impact of their function. A benzothiadiazole-based dye, RK-1, is then systematically studied by both experimental and computational methods, and the results show that the π-bridge composed of thiophene, benzothiadiazole and benzene rings leads to excellent charge separation; and the rotation of these rings during the optical excitation process may well be consistent with the fluorescence spectrum. Finally, the well-known ruthenium-based dyes are theoretically studied to determine the properties of different ligands connected to the metal core of the complex. Conformations with different NCS ligands are calculated in terms of energy and explain well the corresponding results from X-ray diffraction. Acid-base properties of carboxyl groups connected to pyridine ligands in N3 and N749 are theoretically calculated based on thermodynamics and density functional theory. Implicit and explicit models are both adopted to predict these acid dissociative constant values, which are generally in a good agreement with the reported experimental data. The thesis concludes with conclusions and a future outlook.

碩士
國立中正大學
電機工程所
97
This thesis presents design and implementation of PV module I-V curve measurement circuits. PV module measurement circuits can be roughly divided into three types: SMPS(switch mode power supply), energy storage component and equivalent resistance. The SMPS measurement circuit in this study is connected to constant voltage load, so as we can recover energy during measurement, and combine I-V measurement function with a maximum power point tracker. The capacitor in energy storage element of the PV module measurement circuit is replaced by an inductor, and using this inductor to measure the I-V characteristics of a PV module is discussed. When using power MOSFET as equivalent resistance to measure PV module, we feed back its voltage and current to control gate voltage for changing its equivalent impedance. Finally, performances obtained from the three types of circuits are compared, and their analysis and discussion are verified with experimental measurement.

abstract: In the current photovoltaic (PV) industry, the O&M (operations and maintenance) personnel in the field primarily utilize three approaches to identify the underperforming or defective modules in a string: i) EL (electroluminescence) imaging of all the modules in the string; ii) IR (infrared) thermal imaging of all the modules in the string; and, iii) current-voltage (I-V) curve tracing of all the modules in the string. In the first and second approaches, the EL images are used to detect the modules with broken cells, and the IR images are used to detect the modules with hotspot cells, respectively. These two methods may identify the modules with defective cells only semi-qualitatively, but not accurately and quantitatively. The third method, I-V curve tracing, is a quantitative method to identify the underperforming modules in a string, but it is an extremely time consuming, labor-intensive, and highly ambient conditions dependent method. Since the I-V curves of individual modules in a string are obtained by disconnecting them individually at different irradiance levels, module operating temperatures, angle of incidences (AOI) and air-masses/spectra, all these measured curves are required to be translated to a single reporting condition (SRC) of a single irradiance, single temperature, single AOI and single spectrum. These translations are not only time consuming but are also prone to inaccuracy due to inherent issues in the translation models. Therefore, the current challenges in using the traditional I-V tracers are related to: i) obtaining I-V curves simultaneously of all the modules and substrings in a string at a single irradiance, operating temperature, irradiance spectrum and angle of incidence due to changing weather parameters and sun positions during the measurements, ii) safety of field personnel when disconnecting and reconnecting of cables in high voltage systems (especially field aged connectors), and iii) enormous time and hardship for the test personnel in harsh outdoor climatic conditions. In this thesis work, a non-contact I-V (NCIV) curve tracing tool has been integrated and implemented to address the above mentioned three challenges of the traditional I-V tracers. This work compares I-V curves obtained using a traditional I-V curve tracer with the I-V curves obtained using a NCIV curve tracer for the string, substring and individual modules of crystalline silicon (c-Si) and cadmium telluride (CdTe) technologies. The NCIV curve tracer equipment used in this study was integrated using three commercially available components: non-contact voltmeters (NCV) with voltage probes to measure the voltages of substrings/modules in a string, a hall sensor to measure the string current and a DAS (data acquisition system) for simultaneous collection of the voltage data obtained from the NCVs and the current data obtained from the hall sensor. This study demonstrates the concept and accuracy of the NCIV curve tracer by comparing the I-V curves obtained using a traditional capacitor-based tracer and the NCIV curve tracer in a three-module string of c-Si modules and of CdTe modules under natural sunlight with uniform light conditions on all the modules in the string and with partially shading one or more of the modules in the string to simulate and quantitatively detect the underperforming module(s) in a string.
Dissertation/Thesis
Masters Thesis Engineering 2020

abstract: The goal of any solar photovoltaic (PV) system is to generate maximum energy throughout its lifetime. The parameters that can affect PV module power output include: solar irradiance, temperature, soil accumulation, shading, encapsulant browning, encapsulant delamination, series resistance increase due to solder bond degradation and corrosion and shunt resistance decrease due to potential induced degradation, etc. Several PV modules together in series makes up a string, and in a power plant there are a number of these strings in parallel which can be referred to as an array. Ideally, PV modules in a string should be identically matched to attain maximum power output from the entire string. Any underperforming module or mismatch among modules within a string can reduce the power output. The goal of this project is to quickly identify and quantitatively determine the underperforming module(s) in an operating string without the use of an I-V curve tracer, irradiance sensor or temperature sensor. This goal was achieved by utilizing Radiovoltmeters (RVM). In this project, it is demonstrated that the voltages at maximum power point (Vmax) of all the individual modules in a string can be simultaneously and quantitatively obtained using RVMs at a single irradiance, single module operating temperature, single spectrum and single angle of incidence. By combining these individual module voltages (Vmax) with the string current (Imax) using a Hall sensor, the power output of individual modules can be obtained, quickly and quantitatively.
Dissertation/Thesis
Masters Thesis Engineering 2019

The study compares FIT (Feed-in tariff) and RPS (Renewable Portfolio Standard) as the two most commonly used support schemes for renewable energy sources (RES) in the EU. It examines a relationship of an Environmental Kuznets Curve (EKC) and by a practical experiment for public lighting in Prague the study proposes an ecological functioning of electricity grids in the EU with CO2 emissions reduction effect. The main contribution lies in the recency and originality of the econometric analysis and practical experiment. FIT and RPS analysis demonstrates that both schemes affect demand for electricity and increase its price. The econometric model was tested for 28 EU countries for 1990-2013. The results say that the EU is currently located on the downslope of the inverted U-shaped EKC with a turning point, after which the dependence begins to grow. Nevertheless, for the most of observations the turning point is too far to be a source of concern. Practical experiment has shown that installation of energy saving devices for electricity grids in the EU can bring satisfactory results in reducing CO2 emissions independently of state aid. More efficient use of existing energy sources, however, should rather serve as a complement to conventional support, phasing out with the development of RES technologies....

Research in the field of Photonics is in part, directed at the application of light-emitting materials based on silicon platforms. In this work silicon wafers are modified by carbon ion implantation to incorporate silicon carbide, a known light-emitting material. Ion beam synthesis treatments are applied with implant energy of 20 keV, and ion fluences of 3, 5 and 10 × 1016 ions/cm2 at both ambient temperature and high temperature (400 °C). The samples are annealed at 1000 °C, after implantation. The carbon ion implanted silicon is characterized using Raman and Fourier transform infrared spectroscopic techniques, grazing-incidence X-ray diffraction, transmission electron microscopy and electron energy loss spectroscopy. The materials are observed to have a multilayer structure, where the ambient temperature implanted materials have an amorphous silicon layer, and an amorphous silicon layer with carbon-rich, nanoscale inclusions. The high temperature implanted materials have the same layers, with an additional polycrystalline Si layer at the interface between the implanted layer and the target substrate and the amorphous Si layer with SiC inclusions is reduced in thickness compared to the ambient temperature samples. The carbon-rich inclusions are confirmed to be SiC, with no evidence of carbon clusters in the materials observed using Raman spectroscopy. The carbon ion-implanted material is used to fabricate Schottky diodes having a semitransparent gold contact at the implanted surface, and an aluminum contact on the opposite side. The diodes are tested using current-voltage measurements between -12 and +15 V. No reverse breakdown is observed for any of the diodes. The turn-on voltages for the ambient temperature implanted samples are 2.6±0.1 V, 2.8±0.6 V and 3.9±0.1 V for the 3, 5 and 10 × 1016 ions/cm2 samples, respectively. For the high temperature implanted samples, the turn-on voltages are 3.2±0.1 V, 2.7±0.1 V, and 2.9±0.4 V for the implanted samples with same fluences. The diode curves are modeled using the Shockley equation, and estimates are made of the ideality factor of the diodes. These are 188±16, 224.5±5.8, and 185.4±9.2 for the ambient temperature samples, and 163.6±6.3, 124.3±5.3, and 333±12 for the high temperature samples. The high ideality factor is associated with the native oxide layer on the silicon substrate and with the non-uniform, defect-rich implanted region of the carbon ion implanted silicon. Red-orange visible light emission from the diodes is observed with voltage greater than the turn-on voltage applied across the diodes. The luminescence for the ambient temperature samples is attributed to porous silicon, and amorphous silicon. The high temperature implanted samples show luminescence associated with porous silicon, nanocrystalline silicon carbide, and defects in silicon related to ion implantation. The luminescent intensity observed for the ambient temperature samples is higher than for the high temperature samples. The dominant luminescence feature in the carbon ion-implanted silicon material is porous silicon, which is described by quantum confinement of excitons in silicon.

A busca por novas fontes de energia elétrica teve grande influência na utilização de energias renováveis, como a solar fotovoltaica, e torna-las mais eficientes e confiáveis é um passo importante para que sejam incluídas cada vez mais na matriz elétrica mundial. Em um sistema fotovoltaico, devido à sua exposição pelas condições ambientais, os módulos são mais propensos a danos e degradação. Neste trabalho o objetivo é fazer um estudo relativo ao diagnóstico de falhas e degradação em módulos fotovoltaicos, e como elas são identificadas por meio da curva I-V e seus principais parâmetros. Posteriormente, foram aplicadas técnicas de diagnóstico em contexto real em sistemas fotovoltaicos em funcionamento há vários anos. Para isto são apresentados modelos matemáticos e elétricos da célula fotovoltaica, e partindo deles, a extração dos principais parâmetros por algumas técnicas. Com isso, é feita uma implementação computacional em MATLAB/Simulink® do modelo de uma célula fotovoltaica, permitindo simulações variando irradiação e temperatura das células. Pode-se dividir o trabalho em três principais partes: estudo do efeito do sombreamento parcial, validação das técnicas de monitorização da resistência série por meio de emulação de falhas e aplicação das técnicas de diagnóstico em contexto real. Foram realizados testes para cada parte principal do trabalho, para obtenção das curvas I-V e P-V, por meio do traçador de curvas PVPM1000C. Os testes de sombreamento e com emulação de falhas, pode-se obter curvas com e sem falha, já que a mesma é provocada e eliminada conforme necessário, o que permite o cálculo de erros e perdas em cada situação. Já na aplicação em contexto real a simulação ganha maior importância, por ela que é possível comparar a curva obtida para verificação de distorções.Com os dados obtidos, conclui-se que é possível obter um diagnóstico para um sistema fotovoltaico utilizando a curva I-V por meio de sua inclinação, para uma estimação da resistência série com menor erro, ou utilizando-se apenas dos pontos principais para estimação do incremento da resistência, com erros aceitáveis. A combinação de uma análise visual dos módulos, com análise da curva e dos principais parâmetros seria o melhor cenário para um diagnóstico mais preciso.
The search for new sources of electricity has had a major influence on the use of renewable energies, such as solar photovoltaics, and making them more efficient and reliable is an important step towards their inclusion in the global electric matrix. In a photovoltaic system, due to their exposure to environmental conditions, modules are more prone to damage and degradation. In this work the objective is to make a study concerning the fault diagnosis and degradation in photovoltaic modules, and how they are identified through the I-V curve and its main parameters. Subsequently, real context diagnostic techniques were applied to photovoltaic systems in operation for several years. For this are presented mathematical and electrical models of the photovoltaic cell, and from them, the extraction of the main parameters by some techniques. With this, a computational implementation is made in MATLAB / Simulink® of the photovoltaic cell model, allowing simulations varying irradiation and temperature of the cells. The work can be divided into three main parts: a study of the effect of partial shading, validation of series resistance monitoring techniques by fault emulation and application of diagnostic techniques in the real context. Tests were performed for each main part of the work, to obtain the curves I-V and P-V, using the curve plotter PVPM1000C. The shading and fault emulation tests can be obtained with and without fail, since it is provoked and eliminated as necessary, allowing the calculation of errors and losses in each situation. In a real-world application, the simulation becomes more important, because it is possible to compare the curve obtained for verification of distortions. With the obtained data, it is concluded that it is possible to obtain a diagnosis for a photovoltaic system using the curve IV through its slope, for an estimation of the series error with smaller error, or using only the main points for estimation of the increment. of resistance, with acceptable errors. The combination of visual analysis of the modules, curve analysis, and main parameters would be the best scenario for a more accurate diagnosis.

碩士
國立中山大學
電機工程學系研究所
98
In this thesis, the investigation focuses on the analysis of the high frequency characteristics and the nonlinearity of the transistors. In view of the III-V semiconductors which have excellent high frequency performance and the advantage for high frequency circuit design, the 0.15μm InGaAs based pseudomorphic high electron mobility transistors provided by WIN semiconductor Corp. were used in this study. The high frequency measurement was utilized to extract both extrinsic and intrinsic components of the transistors, and further to establish the small signal equivalent model in each bias condition. According to the physical definition of the extracted gm, gds and the relationship with the output current, RF I-V curves could be determined through the integration procedure. The nonlinearity of the transistors can be attributed to the nonlinear input capacitance Cgs and Cgd, and the voltage dependent current source. The high frequency nonlinear models proposed in this thesis were based on classic Angelov model. For the high frequency application, the frequency dependent characteristics of the nonlinear sources would be taken into consideration through the combination of the RF I-V curves and extracted intrinsic components. Thus, the nonlinearities could be able to describe by nonlinear function through the fitting process and model the output performance completely. The accuracy of the models could be confirmed through the comparison between the simulation and the measurement result. Obviously, the high frequency models which include the high frequency effect and the nonlinear characteristics have excellent agreement with the experimental data.

碩士
國立臺灣大學
化學研究所
105
In this study, the electronic properties of an asymmetric (1) and a symmetric (2) tolane derivatives are measured by using scanning tunneling microscope (STM) with gold tip and substrate. The two ends of molecule 1 are cyano group and ethynyl group while the two headgroups of molecule 2 are both ethynyl. The ethynyl group forms C-Au covalent bond with gold electrode upon contact. Calculations via density functional theory (DFT) showed that molecule 1 has rectification ratio of 4.05 at ±1.5 V. This asymmetry in I-V curve arises from the strong coupling between ethynyl end of molecule 1 and electrode, which form a hybrid state that shifts into bias window at +1.5 V. Furthermore, molecule 2 exhibits negative differential resistance (NDR) characteristics around ±(0.8~1.2) V, resulting from the intensity drop HOMO (highest occupied molecular orbital), the transporting orbital, in the transmission function at ±1.2 V. The conductance values of molecule 1 and 2 obtained via STM break junction show that the conductivity of 1 is six fold lower than 2. This indicates that the C-Au bond strength is much stronger than CN-Au bond. To obtain statistical amount of molecular I-V curves, a feedback algorithm to control STM tip movement was developed to automatically form, hold, and sweep MMM junction. The average rectification ratio of molecule 1 at ±1.5 V is about 3, in good agreement with calculation results. On the other hand, some I-V curves of molecule 2 display negative NDR behavior around ±(0.9~1.2) V, and it’s on/off ratio also corresponds well with that calculated by DFT.