Integration of power optimizers in photovoltaic systems is standard practice in some parts of the world. Manufacturers claim that optimizers can significantly reduce electrical losses due to shading. Hence, it is important to investigate this claim and determine under what conditions it is economically warranted to utilize optimizers. In this thesis systems were modelled in PVSyst, for 6 different locations: Abu Dhabi, Borlänge, Madrid, New Delhi, Sydney, and Vienna. In each location there were 3 types of systems: a regular non-optimised system, a SolarEdge optimised system and a TIGO optimised system. Each of these systems had 10 variants where the amount of shading was varied. The system variants were simulated in PVSyst and the effect of power optimizers on electrical losses due to shading was analysed. Afterwards, payback periods were calculated for each system to determine under which conditions power optimizers are economically feasible. It was found that power optimizers significantly reduce electrical losses due to shading. In some scenarios, the losses were reduced by up to 58 %. However, in the current economic climate in 2018, it is not feasible to incorporate power optimizers, in photovoltaic systems in Abu Dhabi, New Delhi or Sydney. Furthermore, in Borlänge, Madrid, and Vienna, optimizers are only feasible if there are high levels of shading, which is not realistic for a regular photovoltaic system.

Algoritmos de busca do ponto de máxima potência (MPPT) são largamente utilizados para se obter a potência máxima fornecida em sistemas fotovoltaicos. Apesar de existirem diversas técnicas de MPPT, os métodos heurísticos de busca como o método da perturbação e observação (P&O) e o método da Condutância Incremental (InC) são os mais usuais por serem simples e confiáveis. Assim, é proposto uma lei de controle com realimentação da tensão de saída de um painel fotovoltaico (PV) de forma a manter o mesmo operando próximo ao ponto de máxima potência, possibilitando com isso uma melhora do desempenho do algoritmo de P&O e InC inclusive quando o painel PV é submetido a rápidas mudanças na irradiação solar. Além disso, devido às características não lineares dos painéis fotovoltaicos, a utilização de técnicas inteligentes que empregam controladores fuzzy para o controle da tensão terminal do PV, parece ser uma solução viável quando comparada aos controladores clássicos com PI e PID, principalmente, porque tais estruturas de controle proporcionam uma lenta resposta dinâmica e problemas de estabilidade relacionados às oscilações em torno do ponto de máxima potência, decorrente do funcionamento dos algoritmos P&O e InC. / Maximum power point tracking (MPPT) techniques are widely used to achieve the maximum output power of a photovoltaic (PV) system. Although there are many MPPT techniques, the heuristic search methods such as perturb and observe (P&O) and incremental conductance (InC) method are the most commonly used because they are simple and reliable in the pursuit of maximum power point. A control law with feedback of the output voltage of a photovoltaic (PV) panel is proposed, in order to maintain it working nearby the maximum power point, enabling an improvement in the performance of the algorithm for P&O and InC even when the PV array is subjected to rapid changes in solar irradiance. Moreover, due to the nonlinear characteristics of the photovoltaic panels, the technique that employ fuzzy logic control seems to be a viable option when compared with conventional proportional and integral or proportional, integral and derivative controllers, mainly because such control structures provide a slow dynamic response and stability issues related to oscillations around the maximum power point due to operation of P&O and InC algorithms.

This dissertation examines the application of various classical root finding methods to digital maximum power point tracking (DMPPT). An overview of root finding methods such as the Newton Raphson Method (NRM), Secant Method (SM), Bisection Method (BSM), Regula Falsi Method (RFM) and a proposed Modified Regula Falsi Method (MRFM) applied to photovoltaic (PV) applications is presented. These methods are compared among themselves. Some of their features are also compared with other commonly used maximum power point (MPP) tracking methods. Issues found when implementing these root finding methods based on continuous variables in a digital domain are explored. Some of these discussed issues include numerical stability, digital implementation of differential operators, and quantization error. Convergence speed is also explored. The analysis is used to provide practical insights into the design of a DMPPT based on classical root finding algorithms. A new DMPPT based on a MRFM is proposed and used as the basis for the discussion. It is shown that this proposed method is faster than the other discussed methods that ensure convergence to the MPP. The discussion is approached from a practical perspective and also includes theoretical analysis to support the observations. Extensive simulation and experimental results with hardware prototypes verify the analysis. / text

H παρούσα διπλωματική εργασία μελέτα τις τεχνικές ανίχνευσης του σημείου μέγιστης ισχύος (Maximum Point Tracking, MPPT) φωτοβολταϊκής συστοιχίας και την προσομοίωση μιας εξ αυτών (Διαταραχής και Παρατήρησης, P&O) για μεταβαλλόμενη ένταση ηλιακής ακτινοβολίας και μεταβαλλόμενο φορτίο. Η προσομοίωση έγινε με το πρόγραμμα MATLAB/SIMULINK. Στο πρώτο κεφάλαιο γίνεται μια εισαγωγή στις μορφές ενέργειας που χρησιμοποιούνται σήμερα και οι οποίες χωρίζονται σε δύο κατηγορίες, τις συμβατικές και τις ανανεώσιμες. Στο δεύτερο κεφάλαιο αναλύεται η φωτοβολταϊκή τεχνολογία, παρουσιάζονται τα ηλεκτρικά χαρακτηριστικά και οι ενεργειακές καταστάσεις του φωτοβολταϊκού στοιχείου και δίνεται ο ορισμός του Σημείου Μέγιστης Ισχύος (Maximun Power Point, MPP), του Συντελεστή Πλήρωσης (Fill Factor, FF) και του Συντελεστή Απόδοσης (Performance Ratio, PR). Στο τρίτο κεφάλαιο γίνεται μια παρουσίαση των μετατροπέων DC/DC διακοπτικού τρόπου λειτουργίας που χρησιμοποιούνται στα συστήματα MPPT και αναλύονται οι βασικές τοπολογίες τους. Το τέταρτο κεφάλαιο αναφέρεται στους μονοφασικούς αντιστροφείς και αναλύεται η ημιτονοειδή PWM τεχνική ελέγχου των αντιστροφέων. Στο πέμπτο κεφάλαιο γίνεται παρουσίαση των σημαντικότερων τεχνικών MPPT. Η κάθε τεχνική έχει ως στόχο την συνεχή ταύτιση του σημείου λειτουργίας με το εκάστοτε σημείο μέγιστης ισχύος. Αναφέρονται τα κύρια πλεονεκτήματα και μειονεκτήματα της κάθε μεθόδου ξεχωριστά, δίνοντας ιδιαίτερη βαρύτητα στην τεχνική «Διαταραχής και Παρατήρησης» (P&O) που θεωρείται η πιο διαδεδομένη και εύχρηστη λόγω της απλότητας στην υλοποίησή της. Στο έκτο κεφάλαιο αναλύεται ξεχωριστά ο τρόπος που υλοποιήθηκε το κάθε υποσύστημα που συνθέτει το συνολικό υπό εξέταση σύστημα και παρουσιάζονται τα αποτελέσματα της προσομοίωσης του συστήματος. Τέλος οδηγούμαστε στο συμπέρασμα ότι ο αλγόριθμος επιτυγχάνει την απορρόφηση της διαθέσιμης ισχύος της φωτοβολταϊκής λειτουργίας αλλά παρουσιάζει δυσλειτουργία κάτω από μεταβολές της ακτινοβολίας. / This diploma thesis examines the Maximum Power Point Tracking (MPPT) techniques for photovoltaic array and the simulation one of them (Perturb and Observe, P&O) for changing level of solar irradiation and changing load. Simulation was made with MATLAB/SIMULINK. Τhe first chapter is an introduction to the types of energy used today and which are divided into two categories, conventional and renewable. The second chapter analyzes the photovoltaic technology, presents the electrical characteristics and the energy states of the photovoltaic element and we define the Maximun Power Point (MPP), the Fill Factor (FF) and Performance Ratio (PR). The third chapter is a presentation of switch mode DC / DC converters used in MPPT systems and analyze the basic topologies. The fourth chapter deals with single-phase inverters and analyzed the sinusoidal PWM control technique of inverters. In the fifth chapter we present the most important technical MPPT. We indicate the main advantages and disadvantages of each method separately, paying special attention to the technique “Perturb and Observe” (P&O), which is considered the most popular and easy to use because of its simplicity in implementation. The sixth chapter the simulation of the whole MPPT system is discussed. We present the modeling of each system separately and we show the results. Finally the study comes to conclusion that the algorithm achieves the enhancement of the available power of the photovoltaic array but it has erratic behaviour under changes of irradiation.

Algoritmos de busca do ponto de máxima potência (MPPT) são largamente utilizados para se obter a potência máxima fornecida em sistemas fotovoltaicos. Apesar de existirem diversas técnicas de MPPT, os métodos heurísticos de busca como o método da perturbação e observação (P&O) e o método da Condutância Incremental (InC) são os mais usuais por serem simples e confiáveis. Assim, é proposto uma lei de controle com realimentação da tensão de saída de um painel fotovoltaico (PV) de forma a manter o mesmo operando próximo ao ponto de máxima potência, possibilitando com isso uma melhora do desempenho do algoritmo de P&O e InC inclusive quando o painel PV é submetido a rápidas mudanças na irradiação solar. Além disso, devido às características não lineares dos painéis fotovoltaicos, a utilização de técnicas inteligentes que empregam controladores fuzzy para o controle da tensão terminal do PV, parece ser uma solução viável quando comparada aos controladores clássicos com PI e PID, principalmente, porque tais estruturas de controle proporcionam uma lenta resposta dinâmica e problemas de estabilidade relacionados às oscilações em torno do ponto de máxima potência, decorrente do funcionamento dos algoritmos P&O e InC. / Maximum power point tracking (MPPT) techniques are widely used to achieve the maximum output power of a photovoltaic (PV) system. Although there are many MPPT techniques, the heuristic search methods such as perturb and observe (P&O) and incremental conductance (InC) method are the most commonly used because they are simple and reliable in the pursuit of maximum power point. A control law with feedback of the output voltage of a photovoltaic (PV) panel is proposed, in order to maintain it working nearby the maximum power point, enabling an improvement in the performance of the algorithm for P&O and InC even when the PV array is subjected to rapid changes in solar irradiance. Moreover, due to the nonlinear characteristics of the photovoltaic panels, the technique that employ fuzzy logic control seems to be a viable option when compared with conventional proportional and integral or proportional, integral and derivative controllers, mainly because such control structures provide a slow dynamic response and stability issues related to oscillations around the maximum power point due to operation of P&O and InC algorithms.

Submitted by PPG Engenharia El?trica (engenharia.pg.eletrica@pucrs.br) on 2018-01-16T12:25:22Z No. of bitstreams: 1 Dissertacao Henrique Cabral Final.pdf: 7113504 bytes, checksum: 991064508825d35b392d6e41b5e9023f (MD5) / Approved for entry into archive by Caroline Xavier (caroline.xavier@pucrs.br) on 2018-01-26T13:01:29Z (GMT) No. of bitstreams: 1 Dissertacao Henrique Cabral Final.pdf: 7113504 bytes, checksum: 991064508825d35b392d6e41b5e9023f (MD5) / Made available in DSpace on 2018-01-26T13:06:39Z (GMT). No. of bitstreams: 1 Dissertacao Henrique Cabral Final.pdf: 7113504 bytes, checksum: 991064508825d35b392d6e41b5e9023f (MD5) Previous issue date: 2016-08-29 / This work presents a study and a development of a current source microinverter, based on the ?uk converter operating in discontinuous conduction mode, for microgeneration purposes based on photovoltaic systems. In this sense, we carried out a steady-state analysis of the ?uk converter, in order to establish the design criteria for the ?uk microinverter. All peripheral systems required for the microinverter operation have also been developed, and are included in this study, namely: the MPPT, PLL, and islanding detection algorithms. All control systems, i.e., the MPPT, PLL, and anti-islanding detection algorithms, were implemented in the DS1104 R&D controller board, from dSPACE?, using MATLAB/Simulink? to program it. / Este trabalho apresenta o estudo e o desenvolvimento de um microinversor de corrente, baseado no conversor ?uk, operando no modo de condu??o descont?nua, para a aplica??o em microgera??o fotovoltaica. Inicialmente, s?o desenvolvidos estudos de car?ter qualitativo e quantitativo do comportamento do microinversor de corrente baseado no conversor ?uk, os quais culminaram no desenvolvimento de crit?rios para o dimensionamento do conversor ?uk, que desempenha um papel central na estrutura do microinversor proposto. Sistemas perif?ricos necess?rios para a opera??o do microinversor, assim como aqueles exigidos pelas concession?rias de energia el?trica para a aplica??o em sistemas de microgera??o s?o estudados e desenvolvidos nessa disserta??o. Para tanto, a implementa??o de todos os sistemas de controle, ou seja, os algoritmos de MPPT, de sincronismo, e de detec??o da opera??o ilhada, foram realizados em ambiente MATLAB/Simulink? associada ? uma placa de desenvolvimento do fabricante alem?o dSPACE?, modelo DS1104, a qual permite o controle em tempo real dos transistores do microinversor.

De nos jours, l’énergie renouvelable est une solution durable pour remplacer les sources conventionnelles d’énergie. L’utilisation de réseaux photovoltaïques (PV) et d’éoliennes est devenue très populaire. Cependant, de cette énergie gratuite découlent de nouveaux défis. Certains des grands inconvénients de ces alternatives sont représentés par un faible taux de conversion de l'énergie et par la nécessité d'utiliser un système de stockage d'énergie Un autre bémol est aussi celui de l’efficacité réduite du transfert entre les réseaux PV et/ou les éoliennes, et les consommateurs. L’objectif de cette thèse est de présenter et de comparer différentes stratégies de commandes pour les systèmes alimentés par les sources d’énergies renouvelables. Un prototype destiné à des fins d’essais a été conçu. Cette thèse traite de différents aspects tels que la modélisation de panneaux PV, l’observateur non linéaire, un algorithme de contrôle basé sur une recherche du point de puissance maximum (Maximum modélisation d’un convertisseur abaisseur DC/DC,construire un Point Power Point Tracking), un algorithme de contrôle polynôme, la stabilité du système. Le chapitre 2 présente différents modèles de cellule photovoltaïque qui peuvent, en outre, être utilisés dans une boucle de contrôle. Une interface utilisateur graphique est créée pour faciliter le calcul de certains paramètres et de la courbe caractéristique de la tension voltage du panneau PV. De plus, un modèle à espace d’états et un modèle de fonction de transfert de certains convertisseurs DC/DC sont présentés. Le chapitre 3 se concentre sur l’élaboration d’un observateur Takagi-Sugeno (T-S) qui fournit la tension estimée du panneau PV. Ce dernier sera, plus tard, utilisé dans le bloc de commande ou pourra servir pour les diagnostics. Le chapitre 4 compare différents algorithmes MPPT classique, ainsi qu’un algorithme de contrôle avancé qui pourra être utilisé plus tard pour améliorer les performances des boucles de contrôles. Une étude de cas sur une commande de supervision utilisant une cellule à combustion est proposée. Le chapitre 5 est orienté vers une approche plus pratique. Il présente un système de contrôle distribué qui est géré via un serveur OPC. Un algorithme de control polynomial robuste R-S-Test élaboré, validé en simulation et testé sur une plateforme expérimentale. Un système d’acquisition de données enregistre les informations envoyées par chacune des boucles de contrôle et est capable de tracer les données en temps réel. Le chapitre 6 est dédié aux conclusions. Le chapitre 7 présente les codes des logiciels développés et certains schémas qui ont été utilisés durant les simulations. Le chapitre 8 liste la bibliographie. / Nowadays renewable energy is a long term solution for replacing the conventional sources of energy. The use of photovoltaic (PV) arrays and wind turbines has become very popular. Nevertheless, this “free energy” arises new challenges. Some of the big inconveniences of these alternatives are represented by a low conversion rate of the energy and the necessity of using an energy storing system. Another drawback is the reduced transfer efficiency between the PV arrays or/and wind turbines and the consumers. The goal of this thesis is to present and compare different control strategies for systems that are powered by renewable sources of energy. A prototype for testing purposes was designed. This thesis treats different aspects such as PV panel modelling, buck converter modelling, building a non-linear observer, a control algorithm based on maximum power point tracking (MPPT), a polynomial control algorithm, the stability of the system. Chapter 2 presents different photovoltaic cell models that can be further used in control loops. A graphic user interface is created for facilitating the computation of certain parameters and of the power-voltage / current-voltage characteristics of a PV panel. Furthermore, a state space model and a transfer function model of some DC/DC converters are presented. Chapter 3 focuses on elaborating a Takagi-Sugeno (T-S) observer which will provide the estimated voltage of the PV panel. The latter will later be used in the control block or it can serve for diagnosis purposes. Chapter 4 compares different classical MPPT algorithms, as well as advanced control algorithms which may be later used to improve the performances of the control loops. A case study on a supervisory control that uses fuel cells is proposed. Chapter 5 is oriented on a rather practical approach. It presents a distributed control system that is managed via an OPC server. A robust R-S-T polynomial controller is designed, validated in simulation and tested on a prototype. A data acquisition system stores the data sent by each of the control loops and is able to plot data in real time. Chapter 6 is dedicated to the conclusions. Chapter 7 presents the code of the developed software and some schematics that were used during simulations. Chapter 8 lists the bibliography.

Renewable energy-hydrogen systems for remote area power supply (RAPS) constitute an early niche market for sustainable hydrogen energy. The primary objective of this research has been to investigate the possibility of direct coupling of a PV array to a proton exchange membrane (PEM) electrolyser by appropriate matching of the current-voltage characteristics of both the components. The degree to which optimal matching can be achieved by direct coupling has been studied both theoretically and experimentally. A procedure for matching the maximum power point output of a PV array with the PEM electrolyser load to maximise the energy transfer between them has been presented. The key element of the matching strategy proposed is to vary the series-parallel stacking of individual cells in both the PV array and the PEM electrolyser so that the characteristic current (I) -voltage (V) curves of both the components align as closely as possible. This procedure is applied to a case study of direct coupling a PV array comprising 75 W panels (BP275) to a PEM electrolyser bank assembled from 50 W PEM electrolyser stacks (h-tec StaXX7). It was estimated theoretically that the optimal PV-electrolyser combination would yield an energy transfer of over 94% of the theoretical maximum on annual basis. This combination also gave the lowest hydrogen production cost on a lifecycle basis. An experimental test of this theoretical result for direct coupling was conducted over a period of 728 hours, with an effective direct-coupling operational time of about 467 hours (omitting the hours of zero solar radiation). Close agreement between the theoretically predicted and actual energy transfer from the PV array to the electrolyser bank in this trial was found. The difference between theoretical and experimental hydrogen production was less then 1.2%. The overall solar-to-hydrogen energy conversion efficiency was found to be 7.8%. The electrolysers were characterised before and after the direct coupling experiment, and showed a small decline in Faraday efficiency and energy efficiency. But this decline was less than the uncertainties in the measured values, so that no firm conclusions about electrolyser degradation can be drawn at this stage. Another direct-coupling experiment, using a larger scale PV-electrolyser system, that is, a 2.4 kW PV array at RMIT connected to the 'Oreion Alpha 1' stand-alone 2 kW PEM electrolyser developed by the CSIRO Energy Technology, was also successfully conducted for a period of 1519 hours (with 941 hours of effective operational time of the electrolyser). Energy-efficient direct coupling of a PV array and electrolyser as examined in this thesis promises to improve the economic viability of solar-hydrogen systems for remote power supply since the costs of an electronic coupling system employing a maximum power point tracker (MPPT) and dc-to-dc converter (around US$ 700/ kW) are avoided.

Η παρούσα διπλωματική εργασία πραγματεύεται την ανάλυση της λειτουργίας των θερμοηλεκτρικών στοιχείων, τη συγκριτική μελέτη μεθόδων απομάστευσης μέγιστης ισχύος από αυτά καθώς και την κατασκευή διάταξης για την πειραματική σύγκριση των μεθόδων αυτών στο εργαστήριο. Η εργασία αυτή εκπονήθηκε στο Εργαστήριο Ηλεκτρομηχανικής Μετατροπής Ενέργειας του Τμήματος Ηλεκτρολόγων Μηχανικών και Τεχνολογίας Υπολογιστών της Πολυτεχνικής Σχολής του Πανεπιστημίου Πατρών. Κύριος στόχος είναι η επιλογή ορισμένων μεθόδων εντοπισμού του σημείου απομάστευσης μέγιστης ισχύος, που μπορούν να εφαρμοστούν σε διάταξη θερμοστοιχείων και η μελέτη αυτών ώστε να εξαχθούν συγκριτικά αποτελέσματα για τις μεθόδους αυτές. Στην παρούσα διπλωματική εργασία διεξήχθη η απαραίτητη βιβλιογραφική αναζήτηση, η μελέτη των μεθόδων απομάστευσης μέγιστης ισχύος, η μελέτη των ιδιαίτερων χαρακτηριστικών των θερμοστοιχείων και η μοντελοποίηση τους ως γεννήτριες ηλεκτρικής ενέργειας. Αρχικά έγινε η αναζήτηση στη βιβλιογραφία των ιδιοτήτων και των χαρακτηριστικών λειτουργίας των θερμοστοιχείων για κατανόηση της λειτουργίας τους. Έγινε μελέτη των ιδιαιτεροτήτων τους και των διαφορών τους από τα άλλα συστήματα που έχουν εφαρμοστεί μέθοδοι απομάστευσης μέγιστης ισχύος, καθώς και αναζήτηση για εύρεση μοντέλου κατάλληλου για την προσομοίωση τους. Στη συνέχεια έγινε βιβλιογραφική αναζήτηση για τις μεθόδους απομάστευσης μέγιστης ισχύος που έχουν εφαρμοστεί σε θερμοστοιχεία, αλλά και σε άλλα συστήματα, όπως ανεμογεννήτριες και φωτοβολταϊκά συστήματα. Μελετήθηκε η φιλοσοφία της κάθε μίας και μεταξύ αυτών έγινε επιλογή των καταλληλότερων για την εφαρμογή τους σε θερμοστοιχεία. Το επόμενο βήμα ήταν η προσομοίωση τόσο του θερμοστοιχείου βάσει ενός εκ των μοντέλων που υφίστανται στη βιβλιογραφία, σε περιβάλλον Matlab/Simulink, όσο και των μεθόδων απομάστευσης μέγιστης ισχύος που επιλέχθηκαν. Στόχος είναι η καλύτερη κατανόηση των χαρακτηριστικών των θερμοστοιχείων και η διεξαγωγή πρώιμης σύγκρισης βάσει των αποτελεσμάτων των προσομοιώσεων. Τέλος μελετήθηκε και κατασκευάστηκε πειραματική διάταξη, κατάλληλη για την εφαρμογή των μεθόδων απομάστευσης μέγιστης ισχύος. Βάσει των μετρήσεων που λήφθηκαν με αυτή τη διάταξη έγινε η τελική σύγκριση μεταξύ των μεθόδων που επιλέχθηκαν. / This diploma thesis deals with the analysis of the operation of thermoelectric elements, and with a comparative study on methods of maximum power bleed and constructing a provision for the experimental comparison of these methods. This work was conducted in the Laboratory of Electromechanical Energy Conversion, Department of Electrical and Computer Engineering, Faculty of Engineering, University of Patras. The main objective is to choose between certain maximum power point tracking methods that can be applied on thermocouples and study them in order to draw comparative results for these methods. In this diploma thesis the necessary literature search was conducted. Also a study on maximum power point tracking methods, and a study on the characteristics of thermocouples was conducted for modeling them as generators of electricity. Initially, a literature search on the properties and operating characteristics of the thermocouples was done in order to understand their function. We investigated their specificities and their differences from other systems where maximum power point tracking methods have been applied, in order to find a suitable model for their simulation. Then a literature search, for maximum power point tracking methods that are applied to thermocouples and other systems such as wind generators and photovoltaic systems, was done. The philosophy of each one of them was studied and were selected the most suitable for application on thermocouples. The next step was to simulate both the thermocouple, under one of the existing models in the literature, and the methods for maximum power point tracking that were selected, on Matlab / Simulink. The objective is to better understand the characteristics of thermocouples and to conduct an early comparison based on the simulation results. Finally an experimental device suitable for implementing the methods was studied and built. Based on the measurements obtained with this device the final comparison between the methods was made.

A energia solar fotovoltaica é a forma de produção de eletricidade que mais cresce no mundo. A potência instalada mundial, até o ano de 2010, era de cerca de 40 GWP e a previsão é de que, somente em 2011, este cifra seja aumentada em mais 24 GWP. O inversor é o elemento central dos sistemas fotovoltaicos. Além de executar a conversão da energia elétrica em corrente contínua para corrente alternada, ele também é responsável pelo gerenciamento da energia entregue à rede e pelo seguimento do ponto de máxima potência. O seguimento do ponto de máxima potência (MPPT) é um processo de controle no qual o inversor procura manter o gerador fotovoltaico operando em uma região da sua curva característica na qual o produto corrente × tensão tenha o seu valor máximo, de forma a otimizar a extração de potência do gerador fotovoltaico. A eficiência de MPPT é um número que indica o grau de precisão, tanto em termos de rapidez como de magnitude, com que o seguidor do ponto de máxima potência atinge o seu objetivo. Assim podem ser definidas duas eficiências de MPPT: a eficiência estática, associada a situações em que a irradiância solar permanece constante durante o intervalo considerado, e a eficiência dinâmica de MPPT, que considera os momentos de variação na intensidade da irradiância, resultantes, por exemplo, da passagem de nuvens. As eficiências de MPPT (especialmente a dinâmica) são de difícil determinação, porém a tarefa fica muito facilitada com a utilização de um simulador de arranjos fotovoltaicos. A norma européia EN 50530:2010 Overall Efficiency of Photovoltaic Inverters propôs uma metodologia para a determinação da eficiência dinâmica de MPPT utilizando perfis variáveis de irradiância a serem programados no simulador de arranjos fotovoltaicos. O objetivo central da tese é fazer uma análise experimental da eficiência dinâmica do seguimento de máxima potência de inversores conectados à rede através da comparação dos resultados de eficiência obtidos seguindo a metodologia definida na norma citada com resultados obtidos a partir de medições em tempo real ao longo de um dia, verificando a adequação da norma às situações de campo. Para a obtenção dos dados de entrada do simulador foram medidas, por diversos dias, a irradiância e temperatura de uma célula de referência. Os inversores foram conectados à saída do simulador de arranjos fotovoltaicos e foram reproduzidas as condições de irradiância e temperatura de três dias selecionados em função do grau de nebulosidade, com comportamento dinâmico semelhante aos perfis de irradiância da norma. Os resultados foram, na maioria dos casos, discordantes. Uma análise dos resultados parciais de eficiência dinâmica indicou como causa desta discrepância a dependência que a eficiência dinâmica de MPPT tem com a taxa de variação da irradiância. Conclui-se que, embora as seqüências de irradiância propostas pela norma constituam uma eficiente ferramenta para o diagnóstico de eventuais deficiências no comportamento do seguidor de máxima potência de inversores, a média dos valores de eficiência de MPPT calculados a partir delas não pode, em princípio, ser considerada como representativa de valores diários. / Photovoltaic solar energy is the fastest growing electricity source in the world. The worldwide capacity until 2010 was about 40 GWP and, by the end of 2011, this figure will be increased by another 24 GWP. The inverter is the pivotal element of PV systems. In addition to performing the conversion of electrical energy from direct current to alternating current, the inverter is also responsible for the management of the energy delivered to the grid and for performing the maximum power point tracking. The maximum power point tracking (MPPT) is a control process by which the inverter tries to keep the PV generator operating in a region of its characteristic curve where the product current × voltage reaches its maximum value. The MPPT efficiency is a figure that indicates the degree of precision, both in terms of speed and magnitude, that the MPPT reaches its goal. Thus, two MPPT efficiencies can be defined: the static efficiency, associated to situations in which the solar irradiance does not vary during the considered interval, and also the dynamic MPPT efficiency, which considers the variation of the irradiance intensity as a result, for example, of the passage of clouds. MPPT efficiencies (especially the dynamic) are hard to determine, but the task becomes much easier with the use of a photovoltaic array simulator. The European standard EN 50530:2010 Overall Efficiency of Photovoltaic Inverters proposes a methodology for determining the dynamic efficiency of MPPT using variable irradiance profiles to be programmed into the photovoltaic array simulator. The main objective of this thesis is to make an experimental analysis of the dynamic MPPT efficiency of grid connected inverters by comparing the efficiency results obtained by following the methodology defined in the referred standard with results obtained from real time measurements in the course of a day, checking the adequacy of the standard when applied to field situations. In order to obtain the input data for the simulator, the irradiance and temperature of a reference cell were measured for several days. The inverters were connected to the output of the array simulator, which reproduced the conditions of irradiance and temperature for three days selected according to the degree of cloudiness, having a dynamic behavior similar to the standard irradiance profiles. The results, in most cases, disagree. An analysis of partial results of dynamic efficiency indicated the dependence of the dynamic MPPT efficiency to the rate of irradiance change as the cause of this discrepancy. As a conclusion, it can be stated that, although the sequences of irradiance proposed by the standard are an efficient tool for the diagnosis of deficiencies in the behavior of the MPP tracker, the average efficiency of MPPT calculated from the sequences cannot, in principle, to be considered as representative of the daily values of dynamic MPPT efficiency.