This thesis presents a new simulation model for DC fuses used to protect semiconductor devices using PSCAD /EMTDC. The basic construction and operation of fuses is discussed, highlighting the difference between the operations of AC and DC fuses. The melting and arcing models of the fuse are implemented separately. The modeling concept is explained in detail and the model is validated with experimental results. / text

Made available in DSpace on 2018-08-02T00:00:46Z (GMT). No. of bitstreams: 1 tese_11381_Amanda Loureiro Nascimento.pdf: 5566345 bytes, checksum: 5395dbad693189a43064b03b3fb7e88b (MD5) Previous issue date: 2017-09-12 / A dissertação propõe a modelagem de um sistema híbrido isolado composto por arranjo fotovoltaico e conjunto de células a combustível do tipo membrana trocadora de prótons utilizando o software PSCAD. O texto traz a revisão dos principais conceitos relativos à energia fotovoltaica e à célula a combustível, além de apresentar trabalhos relacionados ao tema que motivaram a realização desse estudo. O módulo fotovoltaico é modelado a partir de folha de dados fornecida pelo fabricante, enquanto que a célula a combustível tem seu modelo baseado em estudo realizado anteriormente. Para garantir a potência do sistema, são feitas associações série-paralelo dos módulos fotovoltaicos e das células a combustível. A modelagem do sistema híbrido, que inclui inversores, conversor buck e filtros LCL, assim como o controle utilizado são apresentados de forma detalhada. As fontes atuam em conjunto para suprir as cargas no sistema isolado. Entretanto, o conjunto de células a combustível somente produz potência ativa quando o arranjo fotovoltaico é incapaz de suprir a demanda total, com exceção da partida do sistema. Por se tratar de sistema isolado e pela fonte solar fotovoltaica ter a característica de fonte intermitente, a referência dos sistemas de controle advém do conjunto de PEMFCs. O objetivo das simulações é verificar a dinâmica de funcionamento do sistema isolado mediante variações de radiação solar e de carga. Palavras-chave: Célula a combustível. Arranjo fotovoltaico. PEMFC. PSCAD. Sistema híbrido.

Atualmente, em virtude do aumento da demanda energética surgem diversas preocupações devido à escassez dos recursos energéticos tradicionais e os impactos ambientais proporcionados pelos mesmos. Neste contexto, para atender a demanda, diversos investimentos têm sido feitos no desenvolvimento de gerações alternativas e renováveis de energia, bem como na interconexão entre países para exportação de energia. Assim, os estudos exigem soluções mais eficazes para transmissão de energia elétrica, como os sistemas de transmissão High Voltage Direct Current (HVDC), uma alternativa aos sistemas de transmissão atuais, que são predominantemente em Corrente Alternada (CA). Dentre as principais vantagens dos sistemas HVDC, destaca-se a possibilidade de transmissão de grandes montantes de energia a longas distâncias com baixas perdas. Desta forma, eles estão susceptíveis às mais diversas condições meteorológicas e geográficas, em regiões isoladas, o que os tornam vulneráveis a descargas atmosféricas, afetando a segurança do sistema. Assim, neste trabalho, foi simulado um sistema HVDC, utilizando conversores Voltage Source Converter (VSC) do tipo modular multinível, do inglês Modular Multilevel Converter (MMC), frente descargas atmosféricas. Foram analisados diversos casos, visando verificar o comportamento dos conversores e validar a eficácia da utilização de para-raios de óxido metálico, comumente chamado de para-raios de óxido de zinco (ZnO), visto que este é um componente geralmente empregado em sistemas CA. O trabalho apresenta uma revisão acerca dos sistemas VSC-based HVDC (VSC-HVDC), tratando principalmente dos conversores MMC. Também foram descritos todos os modelos utilizados nas simulações, as quais foram realizadas através do software PSCAD/EMTDC. Concluiu-se que o correto dimensionamento e locação dos para-raios operam adequadamente em sistemas Corrente Contínua (CC). Um outro fato interresante é que a sobretensão gerada pelo surto atmosférico se propaga para o lado CA ao incidir no lado CC, mas o contrário não ocorre. / Nowadays, due to the increase in energy demand, several concerns arise due to the scarcity of traditional energy resources and the environmental impacts. In this context, to meet the demand, several investments have been made in the development of alternative and renewable generations of energy, as well as in the interconnection among countries for energy exports. Thus, studies require more effective solutions for electric power transmission, such as VSC-HVDC systems, an alternative to current transmission systems, which are predominantly in CA. Among the main advantages of VSC-HVDC systems, we can highlight the possibility of transmitting large amounts of energy over long distances with low losses. In this way, they are susceptible to the most diverse meteorological and geographic conditions, in isolated regions, which make them vulnerable to lightning, affecting the safety of the system. Thus, in this work, an HVDC system was simulated using VSC converters of the multilevel modular type (MMC) in front of lightnings. Several cases were analyzed in order to verify the behavior of the converters and validate the effectiveness of the use of metal oxide arresters, also known as ZnO arresters, since this is a commonly used component in CA systems. The work presents a review about the VSC-HVDC systems, mainly dealing with the MMC converters. We also described all the models used in the simulations, which were performed through the PSCAD/EMTDC software. It was concluded that the correct dimensioning and location of the arresters operate properly in CC systems. Another interresting fact is that the overvoltage generated by the lightning propagates to the AC side when it hits the CC side, but the reverse does not occur.

Atualmente, em virtude do aumento da demanda energética surgem diversas preocupações devido à escassez dos recursos energéticos tradicionais e os impactos ambientais proporcionados pelos mesmos. Neste contexto, para atender a demanda, diversos investimentos têm sido feitos no desenvolvimento de gerações alternativas e renováveis de energia, bem como na interconexão entre países para exportação de energia. Assim, os estudos exigem soluções mais eficazes para transmissão de energia elétrica, como os sistemas de transmissão High Voltage Direct Current (HVDC), uma alternativa aos sistemas de transmissão atuais, que são predominantemente em Corrente Alternada (CA). Dentre as principais vantagens dos sistemas HVDC, destaca-se a possibilidade de transmissão de grandes montantes de energia a longas distâncias com baixas perdas. Desta forma, eles estão susceptíveis às mais diversas condições meteorológicas e geográficas, em regiões isoladas, o que os tornam vulneráveis a descargas atmosféricas, afetando a segurança do sistema. Assim, neste trabalho, foi simulado um sistema HVDC, utilizando conversores Voltage Source Converter (VSC) do tipo modular multinível, do inglês Modular Multilevel Converter (MMC), frente descargas atmosféricas. Foram analisados diversos casos, visando verificar o comportamento dos conversores e validar a eficácia da utilização de para-raios de óxido metálico, comumente chamado de para-raios de óxido de zinco (ZnO), visto que este é um componente geralmente empregado em sistemas CA. O trabalho apresenta uma revisão acerca dos sistemas VSC-based HVDC (VSC-HVDC), tratando principalmente dos conversores MMC. Também foram descritos todos os modelos utilizados nas simulações, as quais foram realizadas através do software PSCAD/EMTDC. Concluiu-se que o correto dimensionamento e locação dos para-raios operam adequadamente em sistemas Corrente Contínua (CC). Um outro fato interresante é que a sobretensão gerada pelo surto atmosférico se propaga para o lado CA ao incidir no lado CC, mas o contrário não ocorre. / Nowadays, due to the increase in energy demand, several concerns arise due to the scarcity of traditional energy resources and the environmental impacts. In this context, to meet the demand, several investments have been made in the development of alternative and renewable generations of energy, as well as in the interconnection among countries for energy exports. Thus, studies require more effective solutions for electric power transmission, such as VSC-HVDC systems, an alternative to current transmission systems, which are predominantly in CA. Among the main advantages of VSC-HVDC systems, we can highlight the possibility of transmitting large amounts of energy over long distances with low losses. In this way, they are susceptible to the most diverse meteorological and geographic conditions, in isolated regions, which make them vulnerable to lightning, affecting the safety of the system. Thus, in this work, an HVDC system was simulated using VSC converters of the multilevel modular type (MMC) in front of lightnings. Several cases were analyzed in order to verify the behavior of the converters and validate the effectiveness of the use of metal oxide arresters, also known as ZnO arresters, since this is a commonly used component in CA systems. The work presents a review about the VSC-HVDC systems, mainly dealing with the MMC converters. We also described all the models used in the simulations, which were performed through the PSCAD/EMTDC software. It was concluded that the correct dimensioning and location of the arresters operate properly in CC systems. Another interresting fact is that the overvoltage generated by the lightning propagates to the AC side when it hits the CC side, but the reverse does not occur.

Στην διπλωματική εργασία που ακολουθεί, παρουσιάζεται η προσομοίωση και μελέτη ενός υβριδικού συστήματος διανεμημένης παραγωγής. Το σύστημα που εξετάζεται είναι ένα υβριδικό σύστημα ηλεκτροπαραγωγής που αποτελείται από μία ανεμογεννήτρια, μια φωτοβολταϊκή συστοιχία και μία γεννήτρια diesel. Για τη προσομοίωση του συστήματος χρησιμοποιείται το πρόγραμμα σχεδίασης και προσομοίωσης ηλεκτρικών συστημάτων PSCAD. Η εργασία επικεντρώνεται στη δομή και λειτουργία του συστήματος τόσο στην μόνιμη κατάσταση λειτουργίας όσο και στη συμπεριφορά του συστήματος σε διάφορα μεταβατικά φαινόμενα. Τα μεταβατικά φαινόμενα που εξετάζονται είναι τα εξής: • Μείωση προσπίπτουσας ακτινοβολίας σε φωτοβολταϊκη συστοιχία • Αποσύνδεση Ανεμογεννήτριας από το δίκτυο • Τριφασικό βραχυκύκλωμα ως προς την γή στον ζυγό της γεννήτριας diesel • Απότομη αύξηση του φορτίου Στο 1ο Κεφάλαιο, γίνεται μια αναφορά στα υβριδικά συστήματα παραγωγής ηλεκτρικής ενέργειας, στα συστήματα κατανεμημένης παραγωγής, στις δομές τους και στις ανανεώσιμες πηγές ενέργειας. Επίσης αναφέρονται μερικές εφαρμογές τους. Στο 2ο Κεφάλαιο, περιγράφονται ξεχωριστά τα στοιχεία παραγωγής ηλεκτρικής ενέργειας καθώς και τα υπόλοιπα στοιχεία του υβριδικού συστήματος διανεμημένης παραγωγής που απαρτίζουν την εργασία. Ταυτόχρονα παρουσιάζονται και αναλύονται οι μαθηματικές σχέσεις σύμφωνα με τις οποίες λειτουργεί το σύστημα. Στο 3ο Κεφάλαιο, εισερχόμαστε στο περιβάλλον του προγράμματος μοντελοποίησης PSCAD, παρουσιάζεται και περιγράφεται η δομή και τα στοιχεία που αποτελούν το υβριδικό δίκτυο ηλεκτροπαραγωγής, ενώ γίνεται και αναφορά στις προδιαγραφές που πρέπει να τηρούνται από το σύστημα διανεμημένης παραγωγής. Στο 4ο Κεφάλαιο, παρατηρείται η συμπεριφορά ολόκληρου του συστήματος στην μόνιμη κατάσταση λειτουργίας καθώς και των επιμέρους υποσυστημάτων. Στο 5ο Κεφάλαιο, εξετάζεται η συμπεριφορά ολόκληρου του συστήματος καθώς και των επιμέρους υποσυστημάτων στις διαταραχές που έχουμε περιγράψει παραπάνω. Στο 6ο Κεφάλαιο και τελευταίο, καταλήγουμε σε συμπεράσματα τα οποία προέκυψαν από την μελέτη του υβριδικού συστήματος που παρουσιάστηκε. / The thesis that follows, presents the simulation and design of a hybrid distributed system of electrical power generation. The system presented, consists of a wind turbine, a photovoltaic array and a diesel generator. For the system simulation we use the drawing and simulation of electrical systems program, PSCAD. The project focuses on the structure and operation of the system both at steady -permanent state and in system behavior in various transient situations. The transients considered are the following: • Reduction in incident solar radiation into array • Wind Turbine disconnection from the network • Three-phase short circuit as for ground under the rule of the diesel generator • Sharp load increase In 1st chapter, there is a reference to hybrid power generation systems, distributed generation systems, their structures and the renewable sources of energy. Also some applications are mentioned. In 2nd chapter, there is a description of the elements that produce electrical energy and the other elements of the hybrid system of distributed production of electrical energy which are used in the system. At the same time there are presented and analyzed the mathematical relations under which the system operates. In 3rd chapter, we enter the interface of the PSCAD modeling program, present and describe the structure and components of the hybrid power grid, while we also make a reference to the specifications that have to be met by the system of distributed production. In 4th chapter, is examined the behavior of the whole system as well as of the individual subsystems in steady-permanent state. In 5th chapter, is examined the behavior of the entire system as well as of the individual subsections during the disturbances which we have described above. In 6th chapter and last, we come to conclusions that emerged from the study of the hybrid system presented.

Microgrid is a relatively new concept which has gained significant attention recently due to the increasing penetration of distributed energy sources. It brings many benefits to the traditional distribution system. Couples of microgrid testbeds in the forms of either hardware facilities or software simulation systems have been developed to study microgrid issues in many institutes throughout the world. In the work presented in this thesis, a microgrid system model in PSCAD/EMTDC was developed. The proposed microgrid system includes fundamental power system component models, two renewable energy source models (wind and solar) and one energy storage source model. Different case studies were conducted. The results from the simulation case studies showed that the proposed microgrid system in PSCAD had satisfactory performance under different scenarios with renewable energy sources. The proposed microgrid system model can be used for further research on microgrid issues.

Microgrid is a relatively new concept which has gained significant attention recently due to the increasing penetration of distributed energy sources. It brings many benefits to the traditional distribution system. Couples of microgrid testbeds in the forms of either hardware facilities or software simulation systems have been developed to study microgrid issues in many institutes throughout the world. In the work presented in this thesis, a microgrid system model in PSCAD/EMTDC was developed. The proposed microgrid system includes fundamental power system component models, two renewable energy source models (wind and solar) and one energy storage source model. Different case studies were conducted. The results from the simulation case studies showed that the proposed microgrid system in PSCAD had satisfactory performance under different scenarios with renewable energy sources. The proposed microgrid system model can be used for further research on microgrid issues.

Different HVDC grid types and the respective protection options are discussed. An earthed bi-pole HVDC grid was modeled in PSCAD, and using simulation results, the necessity of di/dt limiting inductors to contain the rise of fault currents within the capacity of current hybrid DC breakers is demonstrated. The impact of different inductor sizes on current rise was studied. A fault detection and localization scheme using the rate of change of voltage (ROCOV) measured at the line side of the di/dt limiting inductors is proposed. The protection system was modeled and tested under different fault types and locations. The results show that the proposed method of HVDC grid protection is feasible using the current hybrid DC breaker technology. A systematic procedure for setting the necessary protection threshold values is also demonstrated.

Στην παρούσα διπλωματική εργασία πραγματοποιείται μία τεχνικο-οικονομική μελέτη ενός διασυνδεδεμένου με το δίκτυο ηλεκτρικής ενέργειας της Δ.Ε.Η. φωτοβολταϊκού σταθμού παραγωγής ηλεκτρικής ενέργειας, με ονομαστική εγκατεστημένη ισχύ αιχμής 100kWp. Ο συγκεκριμένος φ/β σταθμός μελετήθηκε για το γεωγραφικό πλάτος της Πάτρας. Στις μέρες μας, η ανάπτυξη φ/β πάρκων παραγωγής ηλεκτρικής ενέργειας γνωρίζει μεγάλη άνθηση και το μέλλον σε αυτόν τον τομέα αναμένεται ακόμη πιο ευοίωνο, ειδικά για μία χώρα με τόσο πλούσιο ηλιακό δυναμικό όπως η Ελλάδα. Στο πρώτο κεφάλαιο γίνεται μία σύντομη αναφορά στην παγκόσμια, ευρωπαϊκή και ελληνική πραγματικότητα στον τομέα της παραγωγής ηλεκτρικής ενέργειας. Στο δεύτερο κεφάλαιο γίνεται μία λεπτομερής ανάλυση του φωτοβολταϊκού φαινομένου και γενικότερα της φωτοβολταϊκής τεχνολογίας. Επίσης, αναλύονται τα ηλεκτρικά χαρακτηριστικά των φ/β στοιχείων και οι σημαντικότεροι παράγοντες που τα επηρεάζουν. Στο τρίτο κεφάλαιο γίνεται η περιγραφή και ανάλυση των επιμέρους στοιχείων που συνθέτουν ένα φωτοβολταϊκό σύστημα. Στο τέταρτο κεφάλαιο εξηγούνται βασικές οικονομικές έννοιες και παρουσιάζονται τρόποι αξιολόγησης μίας επένδυσης. Στο πέμπτο κεφάλαιο πραγματοποιείται μία λεπτομερής τεχνική μελέτη του φ/β σταθμού παραγωγής ηλεκτρικής ενέργειας. Η μελέτη αυτή αφορά το σύνολο του ηλεκτρομηχανολογικού εξοπλισμού που θα χρησιμοποιηθεί (φ/β πλαίσια, αντιστροφείς, καλωδιώσεις, συστήματα προστασίας, βάσεις στήριξης, γειώσεις, σύστημα αντικεραυνικής προστασίας, τοπογραφική διάταξη κλπ). Επίσης, υπολογίζεται η τελική απόδοση του φ/β πάρκου. Στο έκτο κεφάλαιο πραγματοποιείται η οικονομική μελέτη του συστήματος και ερευνάται η οικονομική βιωσιμότητα ενός τέτοιου έργου. Εξετάζονται τρεις διαφορετικές περιπτώσεις χρηματοδότησης και επιλέγεται η πιο συμφέρουσα οικονομικά. Στο έβδομο κεφάλαιο πραγματοποιείται μία μελέτη-προσομοίωση του φ/β συστήματος στον υπολογιστή, με τη βοήθεια του προγράμματος PSCAD. Αρχικά μελετάμε κάθε επιμέρους στοιχείο ενός φ/β συστήματος ξεχωριστά και στη συνέχεια τα συνθέτουμε όλα μαζί και μελετάμε το συνολικό σύστημα. Παρουσιάζεται η απόκριση του συστήματος σε κανονικές συνθήκες λειτουργίας, η επίδραση που έχουν οι μεταβολές της ακτινοβολίας και της θερμοκρασίας, μελετώνται οι αρμονικές και τέλος εξετάζεται η απόκριση του συστήματος σε απότομες μεταβολές της ακτινοβολίας (π.χ. σε παροδική συννεφιά). / The aim of the present thesis is the analysis of a grid connected photovoltaic system, which generates all its produced electrical power to the grid and has a nominal power of 100 kWp. In nowadays there is a significant rise in photovoltaic investments and the immediate future is expected to be more auspicious. In the first chapter, there is a brief presentation of the global, European and Greek situation in the section of electricity generation. In the second chapter, a detailed analysis of the photovoltaic technology is presented. There is a description of the materials and technologies used to manufacture solar cells. Moreover, the electrical properties of cells and modules are explained in detail and also the factors affecting their efficiency. In the third chapter, the main parts of a photovoltaic system are presented in detail. In the fourth chapter, there is a theoretical economic analysis. Specifically, basic economic terms are explained and tools for investment assessment are given. In the fifth chapter, there is a detailed technical study of a grid connected photovoltaic system. All the electrical and mechanical equipment is concerned (pv modules, inverters, wiring, groundings, electrical protection equipment etc). Moreover, the annually produced electrical energy is being estimated. In the sixth chapter, an economic study is presented and the economic sustainability of the investment is investigated. In the seventh chapter, we use the program PSCAD in order to simulate and analyse the photovoltaic system in the computer. Firstly we analyse each part of the photovoltaic system separately and afterwards we compose all these parts together and we analyse the whole system. The system’s response in normal operating conditions, the impact of changes in solar radiation and in cells’ temperature, the harmonics and lastly the system’s response in rapid change of solar irradiance, are all studied in this chapter.

Electric power systems are a key infrastructure today. Power systems can be divided into three major parts: generation, transmission, and distribution. Out of these the distribution system is the most complex part and least studied system. In order to have continuous and reliable power to all customers it is necessary to have a good protection system. Major disturbances that are caused and last for a very short duration are called faults. With the advent of distributed generation (DG), the understanding of fault response has become more difficult. This thesis presents the study of the fault response and the factors that influence the fault response with and without DG. As a part of the fault analysis line to ground faults are placed at various locations on the I 13 node feeder test case. Simulations are conducted in PSCAD and the results are analyzed. At each node the voltage and the current changes at the time of the fault are recorded. A DG is added to the system and is located at various nodes for each fault and the impact of the DG on the fault voltage and current quantities is recorded. A comparison of the impact of faults at various locations is presented. The impact of faults without DG and with DG is also analyzed