This study evaluates energy performance and economic analysis of variable refrigerant flow (VRF) systems in U.S. climate locations using widelyepted whole building energy modeling software, EnergyPlus. VRF systems are known for their high energy performance and thus can improve energy efficiency in buildings. To evaluate the energy performance of a VRF system, energy simulation modeling and calibration of a VRF heat pump (HP) type system is performed using the EnergyPlus program based on measured data collected from an experimental facility at Oak Ridge National Laboratory (ORNL). In the calibration procedures, the energy simulation model is calibrated, according to the ASHRAE Guideline 14-2014, under cooling and heating seasons. After a proper calibration of the simulation model, the VRF HP system is placed in U.S. climate locations to evaluate the performance variations in different weather conditions. An office prototype building model, developed by the U.S. Department of Energy (DOE), is used with the VRF HP system in this study. This study also considers net-zero energy building (NZEB) design of VRF systems with a distributed photovoltaic (PV) system. The NZEB concept has been considered as one of the remedies to reduce electric energy usages and achieve high energy efficiency in buildings. Both the VRF HP and VRF heat recovery (HR) system types are considered in the NZEB design, and a solar PV system is utilized to enable NZEB balances in U.S. climate locations by assuming that net-metering available within the electrical grid-level. In addition, this study conducts life cycle cost analysis (LCCA) of NZEBs with VRF HP and HR systems. LCCA provides present values at a given study period, discounted payback period, and net-savings between VRF HP and HR systems in U.S. climate locations. Preliminary results indicate that the simulated VRF HP system can reasonably predict the energy performance of the actual VRF HP system and reduce between 15-45% for HVAC site energy uses when compared to a VAV system in U.S. climate locations. The VRF HR system can be used to lower building energy demand and thus achieve NZEB performance effectively in some hot and mild U.S. climate locations.

M. Tech. (Electronic Engineering, Faculty of Engineering and Technology), Vaal University of Technology| / The lack of electricity in off-grid rural communities in South Africa (SA) and Africa as well as the budget constraints on these communities restrict these communities from connecting to any online resources (internet and e-books) for educational purposes, thus creating a major contributor to the global digital divide. Renewable energy sources such as solar energy, wind energy and biomass were presented as potential alternatives to grid-connected electricity for remote rural locations. Solar energy was identified as the amply available alternative energy resource in SA. Solar radiation was converted by photovoltaic technology to electricity. National power grid isolation (off-grid) was achieved by using a stand-alone photovoltaic system. Photovoltaic technology classification, material categorisation and system sizing for an e-learning centre was presented. Practical set-ups were utilised to determine the most cost-effective equipment mix of power utilization, power management/storage and ICT equipment to build a pilot e-learning centre. It was established that one photovoltaic panel can be employed to fully recharge a battery of a pilot e-learning centre with an operational period of 7 hours using the available sunlight hours. Owing to the susceptibility of the Vaal Triangle region to thunderstorms causing overcast conditions for days, a ratio of back-up battery capacity (Ah) to number of days (seven hours per day) without sunlight was determined. An algorithm was also derived for sizing the pilot e-learning centre for full scale implementation. Future research recommendations based on this study for a reduced system costs of an off-grid e-learning for rural communities powered by a renewable energy resource were presented. This will increase access to basic education in SA and reduce the global digital divide.

Au Vietnam, plus d’un demi-million d’habitations n’ont pas d’accès à l’électricité. Elles se situent principalement dans des régions montagneuses ou sur des îles. Cependant, c’est un pays qui possède un grand potentiel en énergies renouvelables. Dans ce contexte, l’alimentation en électricité pour les sites isolés est une solution prometteuse en termes économique et environnemental. L’énergie solaire est la plus adaptée à l’alimentation en électricité des villages en raison d’un ensoleillement important et d’une maintenance relativement facile. Dans les systèmes de conversion d’énergie utilisant des sources d’énergies renouvelables, on utilise généralement des convertisseurs statiques simples. En effet, si l’on prend un système photovoltaïque, la poursuite du point de puissance maximale (MPPT) se fait à l’aide d’un convertisseur « boost » ou « buck-boost ». Ainsi, en cas de défaillance, le système est mis hors service. L’objectif de cette thèse est d’apporter des améliorations au niveau d’un système photovoltaïque autonome pouvant être utilisé dans un site isolé. Ainsi nous avons développé un algorithme de recherche du point de puissance maximale (MPPT) utilisant des convertisseurs DC-DC à trois niveaux (CBTN) permettant d’extraire le maximum de puissance d’un générateur photovoltaïque quelles que soient les variations climatiques (température, ensoleillement) ou de la charge. L’architecture à base de panneaux solaires associé à un système de stockage a nécessité la mise en place d’un superviseur flou afin de maîtriser la gestion des flux. Enfin, nous avons proposé une méthode de détection de défauts afin de gérer efficacement les cas de défaillance d’un élément du convertisseur multiniveaux. En effet, en cas de défauts, on doit pouvoir passer en mode dégradé pour pouvoir assurer un service proche du comportement nominal ou au moins minimal en attendant une maintenance corrective. / In Vietnam, more than half a million people do not have access to electricity. They are mainly in mountainous regions or on islands. However, this country has great potential for renewable energy. In this context, these sources of energy can be regarded as promising solutions both economically and environmentally for supplying electrical power. Solar energy is the most suitable to supply villages with electricity because of the plentiful solar radiation and relatively easy maintenance of the structures. In energy conversion systems using renewable energy sources, simple static converters are generally used. Indeed, if we explore a photovoltaic system, the maximum power point tracking (MPPT) is done using a boost or buck-boost converter. Thus, in case of failure, the system is simply switched off. The aim of this thesis is to make improvements to an autonomous photovoltaic system that can be used in an isolated site. Therefore, an MPPT algorithm using three-level DC-DC converters is developed to extract the maximum power of a photovoltaic generator, whatever the climatic variations (temperature, sunlight) or charge. The system’s architecture is based on solar panels associated with a storage system, which required the development of a fuzzy supervisor to control the flow management. Finally, we propose a fault detection method to efficiently manage the failure of a multi-level converter element. Indeed, if there is a fault, we must go into a degraded mode to provide a service close to normal or at least minimal functioning, pending maintenance.

Skolfastigheter is a municipality owned real estate company that manages most of the buildings used for lower education in Uppsala. The company is working in line with the environmental goals of the municipality by installing photovoltaic systems in schools and other educational buildings. Skolfastigheter are planning to install a photovoltaic system in a school in Stenhagen. The purpose of this study is to optimally design the proposed system. The system will be maximized, which in this study entails that the modules will be placed on every part of the roof where the insolation is sufficient. The system will also be grid connected. The design process includes finding an optimal placement of the modules, matching them with a suitable inverter bank and evaluating the potential of a battery storage. Economic aspects such as taxes, subsidies and electricity prices are taken into account when the system is simulated and analyzed. A sensitivity analysis is carried out to evaluate how the capacity of a battery bank affects the self-consumption, self-sufficiency and cost of the system. It is concluded that the optimal system has a total peak power of almost 600 kW and a net present value of 826 TSEK, meaning that it would be a profitable investment. A battery bank is excluded from the optimal design, since increasing the capacity of the bank steadily decreased the net present value and only marginally increased the self-consumption and self-sufficiency of the system.

Le Vietnam est un pays en voie d’industrialisation rapide ce qui engendre une croissance élevée des besoins énergétiques. La consommation énergétique du Vietnam est en augmentation mais pas de façon égale dans tout le pays. En effet, 66.9% de la population du Vietnam vit en zone rurale en 2014. Une grande partie de la population vit encore pauvrement dans des sites isolés avec des accès très restreint aux énergies. Le Vietnam Master Power Plan VII (2011) indique que 759.986 habitations n’ont pas accès à l’électricité.Cependant, le Vietnam est un pays qui possède un grand potentiel en énergie renouvelable (l’énergie solaire, l’énergie éolienne, l’énergie hydroélectrique, l’énergie Biomasse). Le Vietnam a élaboré une stratégie de développement des énergies renouvelables, afin de mobiliser toutes les ressources pour réduire la dépendance aux combustibles fossiles. Les sites isolés se situent principalement au Nord-Ouest du Vietnam, près de la frontière avec le Laos et la Chine, où il existe un grand potentiel d’énergie hydraulique et/ou solaire. Il faut quand même signaler que ces énergies sont souvent saisonnières et, par exemple, une microcentrale hydroélectrique ne peut pas satisfaire la demande en énergie électrique lors de la saison sèche. Donc, un système utilisant deux sources d’énergies renouvelables (panneaux photovoltaïques et microcentrale hydroélectrique) est l’une des solutions optimales pour alimenter en électricité un site isolé au Vietnam. L’objectif de cette thèse est la gestion optimale de l’électricité renouvelable d'un tel système.Afin de satisfaire à une utilisation maximale, le principe de suivi du point maximum (ou Maximum Power Point Tracking – MPPT) est mis en application. Pour la chaine de conversion photovoltaïque, un contrôleur flou à une entrée est proposé afin de suivre le point de puissance maximale du panneau solaire.Pour la chaine de conversion hydroélectrique, une turbine Pelton couplée à un générateur synchrone à rotor bobiné permet d’alimenter en électricité une charge triphasée. Une plateforme d'essais est réalisée dans le laboratoire CReSTIC, IUT de Troyes pour effectuer une validation expérimentale du système de régulation d’une Microcentrale hydroélectrique.Pour la réalisation d’un système de production d’électricité hybride, un superviseur flou est conçu pour obtenir un comportement optimal du système. Après, une étude sur les avantages et inconvénients de ce type de systèmes hybrides pour un site isolé a été effectuée (amélioration de la formation des adultes, augmentation du temps de travail pendant la nuit, réduction du coût du carburant).Ce travail contribue à la connaissance d'une gestion optimale des énergies renouvelables pour site isolé en révélant les avantages et les qualités de l’utilisation des ressources d’énergie renouvelables au gouvernement et à d’autres investisseurs locaux ou internationaux au Vietnam. / As a rapidly industrializing country, the economy of Vietnam's has become very energy intensive. Thought, 66.9% of Vietnam's population lives in rural area in 2014. Many people still live in remote farming areas that are stricken with poverty. The Vietnam Master Power Plan VII (2011) indicates that still 818,947 households are not connected to the national grid, and 759,986 households do not have any access to electricity.Vietnam has high potential on renewable energy resources (Wind, Solar, Hydro, Biomass, and Geothermal). Using hybrid renewable energy system is considered to be one of the most feasible options to bring electricity to local people to improve life quality. The off-grid communities in Vietnam are located mainly in the north-west of Vietnam, near the border with Laos and China, where exist a great potential on Hydro power and/or solar power. A micro hydro power plant cannot satisfy the load demand, especially in dry season. Therefore, additional energy sources such as PV arrays have been suggested to complement power efficiency. Thus, this working discusses the pre-feasibility for small hybrid power generation system consisting of a PV generating unit with storage and a micro hydro generation unit for off-grid areas in Vietnam.The objective of this thesis is to optimize the production of renewable electricity for this type of small hybrid power generation system. For the photovoltaic conversion system, a one input fuzzy logic controller for maximum power point tracking is designed. For the Micro-hydro power plants (MHPP), a Pelton turbine is coupled to a would rotor synchronous generator to supply electricity for a three phase load. To keep the MHPP frequency and voltage outputs constant (50 Hz, 230 V) in spite of changing user loads, the controller is necessary. The experimental results of MHPP frequency and voltages control show the ability of our controller. For the realization of small hybrid power generation, a fuzzy supervisor is adapted to obtain an optimal behavior of the system. Finally, a study on the advantages of this type of hybrid system is carried out (improvement of adult training, increased night working hours, and reduction fuel costs). This thesis contributes to the knowledge of Renewable Energy (RE) by revealing the suitable usability and prospects of RE resources to the government and other local or international investors in Vietnam.

Neste trabalho buscou-se apresentar e analisar os resultados da utilização da Geração Distribuída (GD) Fotovoltaica pelo consumidor residencial (microgerador) e seus efeitos nas relações com a Distribuidora de energia elétrica nos âmbitos técnico, comercial e regulatório, baseados nas Resoluções Normativas 482 e 687 da ANEEL. As conclusões demonstraram haver um desequilíbrio nesta relação. Isto é, nem sempre o retorno financeiro se mostrou viável ao microgerador, tampouco interessante para a Distribuidora. Isto posto, o trabalho expõe uma modelagem tal para que a distribuidora passe a atuar de forma ativa na disseminação da GD. Por fim, modela-se um sistema que pretende aliar o potencial energético solar por parte do consumidor de baixa renda, em troca de fornecimento de energia elétrica limpa e renovável. / This work intended to present and assess the results of the application of Photovoltaic Distributed Generation (DG) by the residential consumer (microgenerator) and the effects on the relations with the distribution utility within the technical, commercial and regulatory, based on the Normative Resolutions 482 and 687 from ANEEL. The conclusions show an unbalance in this relation. Thus, the feasibility for the microgenerator is not assured nor it could interest the utility. That being said, the work presents a model so that the utility starts actively acting to disseminate the DG. Finally, a system is modeled intending to ally the solar power potential from the low-income consumer in exchange of clean and renewable power.

Neste trabalho buscou-se apresentar e analisar os resultados da utilização da Geração Distribuída (GD) Fotovoltaica pelo consumidor residencial (microgerador) e seus efeitos nas relações com a Distribuidora de energia elétrica nos âmbitos técnico, comercial e regulatório, baseados nas Resoluções Normativas 482 e 687 da ANEEL. As conclusões demonstraram haver um desequilíbrio nesta relação. Isto é, nem sempre o retorno financeiro se mostrou viável ao microgerador, tampouco interessante para a Distribuidora. Isto posto, o trabalho expõe uma modelagem tal para que a distribuidora passe a atuar de forma ativa na disseminação da GD. Por fim, modela-se um sistema que pretende aliar o potencial energético solar por parte do consumidor de baixa renda, em troca de fornecimento de energia elétrica limpa e renovável. / This work intended to present and assess the results of the application of Photovoltaic Distributed Generation (DG) by the residential consumer (microgenerator) and the effects on the relations with the distribution utility within the technical, commercial and regulatory, based on the Normative Resolutions 482 and 687 from ANEEL. The conclusions show an unbalance in this relation. Thus, the feasibility for the microgenerator is not assured nor it could interest the utility. That being said, the work presents a model so that the utility starts actively acting to disseminate the DG. Finally, a system is modeled intending to ally the solar power potential from the low-income consumer in exchange of clean and renewable power.

O presente trabalho apresenta os estudos, especificaÃÃes, instalaÃÃo e operaÃÃo de um sistema fotovoltaico com a finalidade de fornecer energia elÃtrica a uma escola pÃblica, localizada em uma Ãrea isolada do sul do Estado do PiauÃ. O sistema foi proposto e seu protÃtipo constituÃdo por painel fotovoltaico, banco de baterias, carregador do banco de bateria e conversor CC/CC elevador, que alimenta as cargas em corrente contÃnua, projetado para uma autonomia de trÃs dias, mesmo em condiÃÃes mÃnimas de radiaÃÃo solar. A energia solar capturada pelo painel solar à armazenada em um banco de baterias estacionÃrias do tipo chumbo-Ãcido. O carregador de baterias trabalhando no ponto de mÃxima potÃncia (MPP) do painel à responsÃvel pelo carregamento deste banco. A carga à suprida pelo conversor CC/CC elevador de alto ganho (24 Vdc para 311 Vdc). O projeto completo do sistema à apresentado ao longo deste trabalho, bem como sÃo apresentados os principais resultados experimentais do protÃtipo mostrado e instalado em campo. / This work presents the studies, specifications, installation and operation of a photovoltaic system in order to provide electricity to a public school located in an isolated area of the southern state of PiauÃ. The system was proposed and its prototype constituted by photovoltaic panel, battery bank, charger from the battery bank and converter DC / DC elevator, that feed the chargers in direct current designed for a range of three days, even in minimum solar radiation. The solar energy captured by solar panel is stored in a stationary batteries, lead acid type. The battery charger working at maximum power point (MPP) of the panel is responsible for load bank. The load is supplied by the DC / DC converter lift high gain (24 Vdc to 311 Vdc). The complete design system and its control are presented throughout this work, as well as presented the main results of the experimental prototype shown and installed in the field.

Στην παρούσα διατριβή αναπτύσσονται κατάλληλα μοντέλα για τις επιμέρους μονάδες φωτοβολταϊκού (ΦΒ) συστήματος συνδεδεμένου στο δίκτυο. Στόχος είναι να αντιμετωπιστούν ταυτόχρονα και αποτελεσματικά οι ιδιαιτερότητές του, που οφείλονται στη συμπεριφορά των διακοπτικών στοιχείων και στα μη γραμμικά χαρακτηριστικά της ΦΒ γεννήτριας και του μετασχηματιστή απομόνωσης. Αναπτύσσονται μέθοδοι που αυξάνουν την ταχύτητα εξομοίωσης. Αυτό επιτυγχάνεται με χρήση αυξητικών μοντέλων για τα μη γραμμικά στοιχεία και αποτελεσματικών αλγορίθμων για την αντιμετώπιση της μεταβλητής τοπολογίας. Τα μοντέλα που παρουσιάζονται μπορούν να χρησιμοποιηθούν για συνδεδεμένα στο δίκτυο ΦΒ συστήματα οποιασδήποτε διάταξης. Μέσω εξομοιώσεων της λειτουργίας ενός οικιακού ΦΒ συστήματος συνδεδεμένου στο δίκτυο διερευνάται η ευαισθησία της αρμονικής παραμόρφωσης τάσεων και ρευμάτων σε μεταβολές παραμέτρων του συστήματος. Στη συνέχεια παρουσιάζεται ένα νέο μοντέλο για τη ροή ενέργειας σε κυκλώματα με μη ημιτονοειδείς κυματομορφές. Το μοντέλο παρέχει μαθηματική περιγραφή μέσω του πολυδιανύσματος της ισχύος, το οποίο γεφυρώνει το χάσμα μεταξύ στιγμιαίας και φαινομένης ισχύος, όπως η μιγαδική ισχύς υπό ημιτονοειδείς συνθήκες. Το πολυδιάνυσμα της ισχύος επιτρέπει συστηματική και ενιαία αντιμετώπιση όλων των περιπτώσεων. Το μοντέλο ροής ενέργειας που παρουσιάζεται περιγράφει τις συνιστώσες ισχύος όχι μόνο ποσοτικά, αλλά και ποιοτικά. Από φυσικής πλευράς βασίζεται στη γενίκευση της έννοιας της αμοιβαίας σύζευξης. Η προσέγγιση που ακολουθείται επιτρέπει την φυσική ερμηνεία όλων των συνιστωσών της ισχύος, οι οποίες συνδέονται με μια αναπαράσταση μέσω ισοδυνάμου κυκλώματος. Οι προϋπάρχουσες μέθοδοι μπορούν να προκύψουν ως ειδικές περιπτώσεις του μοντέλου. Η βαθύτερη κατανόηση των φαινομένων ισχύος που παρέχει θέτει το θεωρητικό υπόβαθρο για την επίλυση πρακτικών προβλημάτων, όπως η αντιστάθμιση. Ακολούθως εξετάζεται η επιλογή του βέλτιστου μεγέθους παθητικών φίλτρων με παράλληλους συντονιζόμενους κλάδους. Η διερεύνηση λαμβάνει υπόψη όχι μόνο πηγές αρμονικών ρευμάτων λόγω μη γραμμικών φορτίων αλλά και την παρουσία προϋπάρχουσας αρμονικής παραμόρφωσης της τάσης. Μέσω αναλυτικής μεθόδου προκύπτουν εκφράσεις κλειστής μορφής για απλοποιημένες περιπτώσεις. Αυτές μπορούν να βοηθήσουν στην κατανόηση της επίδρασης διαφόρων παραμέτρων. Επίσης διαμορφώνεται η γενικότερη περίπτωση του προβλήματος και αντιμετωπίζεται με Γενετικούς Αλγόριθμους. Μέσα από εκτεταμένες εξομοιώσεις για διάφορα επίπεδα αρμονικών τάσης και ρεύματος, διερευνώνται διεξοδικά οι δυνατότητες των παθητικών φίλτρων. Τα πρακτικά συμπεράσματα που προκύπτουν μπορούν να βοηθήσουν στη λήψη αποφάσεων για τον έλεγχο των αρμονικών σε διάφορες εφαρμογές. / In this thesis, appropriate models for the individual components of a grid-connected photovoltaic (PV) system are developed. The aim is to simultaneously and efficiently handle its peculiarities, which are due to the switching action of the switching devices and the nonlinear characteristics of the PV generator and the isolation transformer. Methods that increase simulation speed are developed. This is accomplished by using incremental models for the nonlinear components and efficient algorithms to handle the variable topology. The presented models can be used for grid-connected PV systems of any configuration. Through simulations of the performance of a residential grid-connected PV system the sensitivity of the harmonic distortion of voltages and currents to variations in system parameters is investigated. Next, a novel model for the energy flow in circuits with nonsinusoidal waveforms is presented. This model provides a mathematical description through the power multivector, which bridges the gap between the instantaneous and apparent power, like the complex power does under sinusoidal conditions. The power multivector permits a systematic and uniform treatment of all cases. The presented energy flow model describes power components not only quantitatively but also qualitatively. From a physical perspective it is based on the generalization of the concept of mutual coupling. The approach that is followed permits the physical interpretation of all power components, which are associated with an equivalent circuit representation. Pre-existing methods can be derived as special cases of the model. The deeper understanding of power phenomena it provides sets the theoretical foundation for the solution of practical problems, such as compensation. Next, the optimal sizing of shunt, passive, single-tuned filters is examined. The investigation takes into account not only harmonic current sources due to nonlinear loads but also the presence of background voltage harmonic distortion. Through an analytical approach closed-form expressions are derived for simplified cases. These can help in the comprehension of the influence of various parameters. Moreover, the general case of this problem is formulated and solved using Genetic Algorithms. Through extensive simulations for various current and voltage harmonic levels, the potentialities of these filters are thoroughly investigated. The practical conclusions that are drawn can facilitate decisions regarding harmonic control in various applications.

Σκοπός της συγκεκριμένης διπλωματικής εργασίας είναι η εξομοίωση ενός φωτοβολταϊκού συστήματος διασυνδεδεμένου στο τριφασικό δίκτυο με σκοπό τη μελέτη της λειτουργίας του και του καλύτερου σχεδιασμού του. Το σύστημα περιλαμβάνει τη φωτοβολταϊκή γεννήτρια, ένα φίλτρο διασύνδεσης της γεννήτριας με τον αντιστροφέα και ένα απλοποιημένο μοντέλο του τριφασικού συστήματος. Για την εξομοίωση του κυκλώματος το οποίο είναι χρονικά μεταβαλλόμενο λόγω της διακοπτικής λειτουργίας του μετατροπέα αναπτύσσεται μια συστηματική και αποτελεσματική μέθοδος για την ανάλυση κυκλωμάτων που περιέχουν e-R-L, C κλάδους και ιδανικούς διακόπτες. Χρησιμοποιώντας την τοπολογία του κυκλώματος και κατάλληλες μήτρες μετασχηματισμού οι εξισώσεις που περιγράφουν το αγώγιμο και μη αγώγιμο τμήμα του κυκλώματος προκύπτουν αυτόματα. Οι χρησιμοποιούμενες μήτρες μετασχηματισμού προκύπτουν με απλό και συστηματικό τρόπο από τις θεμελιώδης μήτρες του κυκλώματος. Σε κάθε βήμα προκύπτουν τα ρεύματα όλων των κλάδων του κυκλώματος από την επίλυση του αγώγιμου τμήματος αυτού και οι τάσεις των βαλβίδων που δεν άγουν από την επίλυση του μη αγώγιμου τμήματός του. Η μέθοδος είναι γενική και μπορεί να εφαρμοστεί για την μελέτη τυχόντων σφαλμάτων σε οποιοδήποτε τμήμα του κυκλώματος. Παρουσιάζονται τα αποτελέσματα της εξομοίωσης για λειτουργία του μετατροπέα ως ανορθωτή, ως αντιστροφέα, ως αντιστροφέα με φωτοβολταϊκή γεννήτρια και ως αντιστροφέα με φωτοβολταϊκή γεννήτρια και με ανιχνευτή σημείου μέγιστης ισχύος. Το χρησιμοποιηθέν μοντέλο θα μπορούσε να βελτιωθεί αν στην θέση του τριφασικού συστήματος χρησιμοποιηθεί ακριβέστερη αναπαράσταση του τριφασικού δικτύου στην οποία να περιλαμβάνεται και ο τριφασικός μετασχηματιστής ισχύος που διασυνδέει το φωτοβολταϊκό σύστημα με το AC δίκτυο. / The objective of this “Diploma Thesis” is the simulation of a grid connected photovoltaic (PV) system and the study of its operation. The system consists of a PV generator, a DC filter and a simplified model of the three-phase system. The method which was used for the simulation of the circuit (which is a varying topology circuit due to the switching operation of the converter) is a systematic, efficient and conceptually simple method for the analysis of circuits consisting of linear e, R, L, C elements and ideal switches. On the basis of well known network topological concepts a suitable transformation tensor is constructed at every step. This tensor constitutes a flexible and powerful tool to assemble automatically the necessary on-switch current and off-switch voltage equations required for any conduction pattern. The method is general and can be applied for the study of any random faults in any part of the circuit. Results of the simulation for operation of the converter as rectifier, as inverter with battery, as inverter with PV generator and as inverter with PV generator and with MPPT are presented. The used model could be improved if the three-phase system is more precisely represented by a power three-phase transformer which connects the PV system with the AC network.