Background: Wind turbines are a form of renewable energy, which generate electricity from wind energy, a practice dating back over 100 years. More recently, large-scale wind energy developments have started to employ one or several industrial wind turbines, which produce the majority of wind energy in Ontario. The production of electricity from the movement of industrial wind turbine motor blades creates both mechanical and aerodynamic noise. This type of environmental noise is a growing public health concern, especially for residents living close to industrial wind turbines. A body of evidence now exists to suggest that industrial wind turbine noise can impair health and contribute to annoyance and sleep disturbance. However, in Ontario, little is known about how industrial wind turbines impact people living in their vicinity. Objectives: This investigation was a cross-sectional study involving eight Ontario communities that contain greater than ten industrial wind turbines. The objectives of this study were to explore the association between proximity to industrial wind turbines and self-reported health effects, specifically quality of life (both physical and mental health) and sleep disturbance, in residents living close to wind turbines. Dose-response relationships were also explored in an attempt to investigate acceptable exposure levels and appropriate setback distances for industrial wind turbines. Methods: Eight wind farms in Ontario were selected for analysis. For this cross-sectional study, the ???Quality of Life and Renewable Energy Technologies Study??? survey was used to measure the impact of industrial wind turbines on health. Using Canada Post???s Unaddressed Admail Service, surveys were sent to 4,876 residences near industrial wind turbines in these eight communities. Survey responses were sent back to the University of Waterloo and data from the surveys were used for analysis. Descriptive analyses were performed and multiple regression models were run to investigate the effect of the main independent variable of interest (distance to nearest industrial wind turbine) on the various outcome variables. Descriptive statistics, including means and standard deviations were performed on a number of dependent and independent variables including age, sex, time in home, number of industrial wind turbines within 2,000 meters and sleep and health outcomes. Results: In total, 412 surveys were returned (8.45% response rate); 16 of these survey respondents did not provide their home address. Therefore, 396 surveys were included in the analysis. The mean self-reported distances of survey respondents to wind farms was 2,782 meters +-3,950 meters (range: 0.40-55,000 meters). The mean calculated distance from residence to the closest industrial wind turbine was 4,523 meters +-4,420 meters (range: 316-22,661 meters). The difference between the calculated and perceived distance measurements was statistically significant (P<0.001) with survey respondents reporting that they live, on average, 1,741 meters closer to wind farms than they actually do. The relationship between Pittsburgh Sleep Quality Index and ln(distance) was found to be statistically significant (P=0.01) when controlling for age, gender and county, meaning that as distance increased (move further away from an industrial wind turbine), Pittsburgh Sleep Quality Index decreased (i.e. sleep improved) in a logarithmic relationship. Among the eight Wind Turbine Syndrome index variables, the relationship between vertigo and ln(distance) was statistically significant (P<0.001) when controlling for age, gender, and county. Additionally, the relationship between tinnitus and ln(distance) approached statistical significance (P=0.08) when controlling for age, gender and county. Both vertigo and tinnitus were worse among participants living closer to industrial wind turbines. Conclusion: Study findings suggest that industrial wind turbines could have an impact on health. Using a sample of rural Ontario residents (although not necessarily representative of the target population), this study explored the quality of life (both physical and mental health) and sleep disturbance of residents living in the vicinity of industrial wind turbines. However, because of study limitations, there are many questions still to be answered before firm conclusions can be drawn. Based on the findings of this study it is recommended that further studies be carried out to examine the effects of low-level stressors, such as industrial wind turbine noise, on health. Specifically, study findings suggest that future research should focus on the effects of industrial wind turbine noise on sleep disturbance and symptoms of inner ear problems. Although the study findings could suggest that there is a possible association between various health outcomes and how far someone lives from an industrial wind turbine, it is important to remember that there are limitations to these conclusions.

Στα σύγχρονα συστήματα ηλεκτρικής ενέργειας, η άεργος ισχύς που παράγουν τα αιολικά πάρκα είναι ένα πολύ σοβαρό ζήτημα που πρέπει να μελετηθεί τόσο στη μόνιμη κατάσταση όσο και στη δυναμική και μεταβατική μετά από σφάλματα και μεγάλες διαταραχές. Στην παρούσα διπλωματική εργασία εκπονείται μελέτη που αφορά την κατανεμημένη παραγωγή και ιδιαίτερο βάρος δίνεται στην ανεμογεννήτρια μεταβλητών στροφών με επαγωγική μηχανή διπλής τροφοδοσίας (DFIG) και τα όρια που παρουσιάζει η λειτουργία της από περιοριστικούς παράγοντες όπως: 1) ρεύμα του στάτη, 2) τάση του δρομέα, 3) ρεύμα του δρομέα. Αρχικά μελετάται η γενική δομή ενός συστήματος ηλεκτρικής ενέργειας καθώς και τα βασικά χαρακτηριστικά του δικτύου. Περιγράφεται επίσης σύντομα η κανονική λειτουργία και η ευστάθεια των συστημάτων ηλεκτρικής ενέργειας καθώς και πως μπορεί να γίνει ρύθμιση της τάσης και της αέργου ισχύος δύο μεγεθών με ισχυρή συσχέτιση. Στην συνέχεια προχωράμε στην περιγραφή της διεσπαρμένης παραγωγής και την διείσδυσή της στο δίκτυο. Παρουσιάζονται τα πλεονεκτήματα καθώς και τα μειονεκτήματά της όπου αυτά υπάρχουν και περιγράφονται κάποια πολύ βασικά είδη της δίνοντας έμφαση στα είδη των ανεμογεννητριών. Στο κύριο μέρος της εργασίας περιγράφεται αρχικά το μοντέλο της ανεμογεννήτριας μεταβλητών στροφών με επαγωγική μηχανή διπλής τροφοδοσίας (DFIG) και παρουσιάζεται η θεωρητική επίδραση των παραπάνω περιοριστικών παραγόντων στην λειτουργία της. Στόχος της μελέτης είναι η προσομοίωση των παράπάνω σε μια πραγματική μηχανή κάτι που γίνεται στο Simulink του Matlab. Α) παρουσίαζονται τα όρια από τους τρείς περιοριστικούς παράγοντες. Β) περιγράφεται η επίδραση του μετασχηματισμού από αστέρα σε τρίγωνο στα τυλίγματα του στάτη. Γ) Σχεδιάζονται όλα τα όρια μαζί και παρατηρούμε ότι το όριο που κυριαρχεί σχετικά με την παραγωγή αέργου ισχύος είναι το ρεύμα του δρομέα ενώ το όριο που κυριαρχεί σχετικά με την απορρόφηση αέργου ισχύος είναι το ρεύμα του στάτη. Δ) Τέλος παρατηρούμε ότι η τάση του δρομέα επιδρά σαν όριο μόνο σε μεγάλες τιμές της ολίσθησης (είτε αρνητικής είτε θετικής ), αλλά κοντά στα όριά της είναι πολύ ευαίσθητη στις αλλαγές της τιμής της ολίσθησης. / In the modern regulations of transport of energy, reactive power by wind farms is a major concern that should be studied during both steady-state and dynamic-fault condition. This diploma thesis forms the distribution systems and particular weight is given in the wind turbine of variable speed with doubly fed induction generator (DFIG) and the operation limits from these factors: 1) stator current, 2) rotor voltage, 3) rotor current . Initially is studied the general structure of system of electric energy and the basic characteristics of the grid. Also are shortly described the regular operation and the stability of systems of electric and the regulation of voltage and reactive power- two sizes with powerful cross-correlation . Then we are going on with the description of distribution systems and the impact that wind turbines have in the grid where were connected. The advantages are presented as well as the disadvantages where these exist and we describe some of the very basic types of distributed generation giving accent in the types of wind generators. In the main part of work is described initially the model of wind turbine of variable speed with doubly fed induction generator (DFIG) and is presented the effect of the restrictive factors in the operation. Objective of study is the simulation in a real machine something that becomes in the Simulink of Matlab. A) The limitations in reactive power production, caused by the rotor current, the rotor voltage and the stator current are derived. B) The influence of switching from D to Y coupling of the stator is investigated. C) It is concluded that the limiting factor regarding reactive power production will typically be the rotor current limit, and that the limit for reactive power absorption will be the stator current limit. D) Further, it is concluded that the rotor voltage will only have a limiting effect at high positive and negative slips, but near the limitation, the reactive power capability is very sensitive to small changes in the slip.

Σήμερα στα συστήματα ηλεκτρικής ενέργειας μεγάλο ποσοστό της ισχύος παράγεται από αιολικά πάρκα αλλά και από θερμικούς σταθμούς. Η διείσδυση κατανεμημένης παραγωγής στα συστήματα χρειάζεται ιδιαίτερη μελέτη. Σε αυτή την εργασία ερευνήθηκε η λειτουργία ολόκληρων συστημάτων διανομής που περιείχαν διάφορα αιολικά πάρκα και θερμικούς σταθμούς. Αρχικά εξετάστηκε το θέμα του εντοπισμού των απωλειών ισχύος σε συστήματα διανομής με κατανεμημένη παραγωγή. Παρουσιάστηκαν μια νέα σχετικά προσέγγιση στον εντοπισμό των απωλειών με βάση τις τροφοδοσίες ρευμάτων καθώς και μία μήτρα εμπεδήσεων. Τα παραπάνω μπορούν να χρησιμοποιηθούν για τη στατιστική ανάλυση των απωλειών βάσει της γραμμικής παλινδρόμησης ή την εκτίμηση της συνδιακύμανσης μεταξύ φορτίου και παραγωγής. Στη συνέχεια περιγράφεται το πρόβλημα της βραχυπρόθεσμης ευστάθειας τάσης σε δίκτυα με υψηλή διείσδυση κατανεμημένης παραγωγής. Εστιάζουμε στην αναπαράσταση του δικτύου κατά τη διάρκεια και μετά από την εμφάνιση σφάλματος ως ισοδύναμο κύκλωμα Thevenin τάσης και εμπέδησης. Επίσης διερευνάται η επίδραση γειτονικών σύγχρονων γεννητριών, ανεμογεννητριών τύπου Δανίας, SVC, και STATCOM στις παραμέτρους Thevenin. Τελικά εξετάζεται το πρόβλημα του ελέγχου τάσης και άεργου ισχύος. Ιδιαίτερη προσοχή δίνεται στους περιορισμούς τροφοδοσίας πραγματικής και άεργου ισχύος οι οποίες επιβάλλονται από τα όρια του πλάτους της τάσης. / Nowadays in power systems a large amount of power produced from wind farms and Heat Power Plants (HPP). High penetration of distributed generation in power systems is a subject to study. Τhe focus of this project is on the operation of an entire distribution system with several wind farms and HPP. Firstly, the subject of allocation of power system losses in a distribution system with distributed generation is treated. A new approach to loss allocation based on current injections and an impedance matrix is presented. The formulation can be used for statistical analysis of the losses based on linear regression or estimates of covariances between production and load. Secondly, the problem of short term voltage stability in networks with high penetration of DG is assessed. The focus is on the representation of the network during and after a fault as a Thevenin equivalent voltage and impedance. The influence of adjacent synchronous generators, Danish concept wind turbines, SVCs and STATCOMs on the Thevenin parameters have been investigated. Finally, the problem of voltage and reactive power control is investigated. Special focus is on the constraints for active and reactive power injection which are imposed by the voltage magnitude limits.

Σκοπός της παρούσας διπλωματικής εργασίας είναι η μελέτη των παραγόντων που επηρεάζουν την αξιοπιστία και τη διαθεσιμότητα των αιολικών συστημάτων. Η επεξεργασία των ανεμολογικών δεδομένων (SCADA) έγινε από διάφορες εταιρείες, για να βοηθήσουν στην πρόβλεψη της ενεργειακής παραγωγής. Εξετάζονται επίσης τα διάφορα είδη βλαβών που συμβαίνουν στα αιολικά πάρκα, ειδικά τα πρώτα χρόνια λειτουργίας τους, και πώς ακριβώς μπορούμε να μειώσουμε το ποσοστό τους αν επέμβουμε σωστά. Τέλος, δίνονται χρήσιμες πληροφορίες για το βαθμό χρησιμοποίησης της αιολικής ενέργειας στην Ελλάδα και παγκόσμια. Πιο αναλυτικά, η δομή της εργασίας οργανώνεται στα εξής εννέα κεφάλαια: Το πρώτο κεφάλαιο ξεκινάει με γενικές πληροφορίες για τις ανανεώσιμες πηγές ενέργειας και γιατί η χρήση τους έγινε επιτακτική. Κατόπιν, γίνεται εξειδίκευση στην αιολική ενέργεια με μια ιστορική αναδρομή για να μπορέσει να δει κανείς την εξέλιξη της στο πέρασμα του χρόνου. Αναφέρονται επίσης τα πλεονεκτήματα της αιολικής ενέργειας, τα προβλήματα που προκύπτουν από την αξιοποίησή της καθώς και διάφορες λύσεις για την αντιμετώπισή τους. Στο δεύτερο και τρίτο κεφάλαιο εξετάζεται η βασικότερη παράμετρος που οδήγησε την αιολική ενέργεια στο στάδιο που είναι σήμερα, ο άνεμος. Αναλύεται η συμπεριφορά του, τα κύρια χαρακτηριστικά του και η κατανομή του. Το τέταρτο κεφάλαιο παρουσιάζει τις μονάδες που συμβάλλουν στη δέσμευση και εκμετάλλευση της αιολικής ενέργειας. Παρουσιάζονται με λεπτομέρεια τα δομικά τους στοιχεία και αναφέρονται οι κατηγορίες στις οποίες ανήκουν ανάλογα με τα χαρακτηριστικά τους. Αναφέρονται επίσης, οι βασικοί τρόποι λειτουργίας τους καθώς και οι παράμετροι που επηρεάζουν την επιλογή της τοποθεσίας εγκατάστασής τους. Στο πέμπτο κεφάλαιο εξετάζονται τα ενεργειακά χαρακτηριστικά των ανεμογεννητριών και παρουσιάζονται επίσης τα στοιχεία που επιδρούν στην αναμενόμενη ενεργειακή παραγωγή και στο κόστος της αιολικής ενέργειας. Στο έκτο κεφάλαιο, δίνονται γενικές πληροφορίες για τα αιολικά πάρκα, τη λειτουργία και τη συντήρησή τους καθώς και κάποιοι οικονομικοί παράγοντες όσον αφορά τα υπεράκτια αιολικά πάρκα. Στο έβδομο κεφάλαιο παρουσιάζονται τα αποτελέσματα της επεξεργασίας ανεμολογικών δεδομένων, ώστε να γίνουν κατανοητοί οι παράγοντες που επηρεάζουν και βελτιώνουν την αξιοπιστία των αιολικών συστημάτων. Στο όγδοο κεφάλαιο, εξετάζεται και αξιολογείται η διαθεσιμότητα των αιολικών συστημάτων, δίνονται πληροφορίες για τα διάφορα είδη της καθώς και διάφοροι τρόποι οι οποίοι συμβάλλουν στη βελτίωσή της, που είναι και το ζητούμενο για την οικονομική βιωσιμότητα του αιολικού πάρκου. Τέλος, στο ένατο κεφάλαιο, παρουσιάζεται η τρέχουσα κατάσταση στην Ελλάδα, στις χώρες της Ευρωπαϊκής Ένωσης αλλά και παγκόσμια. / The purpose of this diploma thesis is the study of factors that affect the reliability and availability of wind energy systems. Wind data from several companies were accumulated for a better prediction of the energy production. More specifically, the structure of the essay is organized in the following nine chapters : The first chapter starts with general information on renewable energy sources and the reasons why their use became imperative. Moreover, there is specialization in wind energy with a throwback which enables us to see the evolution of the passing of time. The second and third chapter examines the key parameters leading wind energy in its present form, the wind. The fourth chapter presents the system-units that contribute to the exploitation of wind energy. Their components are presented in detail, and the categories to which they belong are indicated according to their characteristics. The fifth chapter discusses the energy characteristics of the wind turbines and also presents the elements that affect the expected energy production and the cost of wind energy. In the sixth chapter, general information about wind farms are given, as well as information about operation, maintenance and some economic factors in offshore wind farms. The seventh chapter presents the results of wind data processing in order to understand the factors that influence and improve the reliability of wind systems. The eighth chapter examines and evaluates the availability of wind energy systems. Information about the different types of availability are given, and also details about the different ways which contribute to the improvement of availability are presented. Finally, the ninth chapter presents the current situation in Greece, the countries of the European Union and worldwide.

System specifications and testing model for increasing the rated power output, rotor diameter, hub height, and maximum tip speed of horizontal axis wind turbines is designed and implemented on the system advisor model simulator. Its performance is tested on offshore wind turbine’s direct-drive and single stage-low speed generators. Although this simulator produces impressive results, it has some limitations in the operation of wind turbines. The terrain and topography of wind turbines are not considered in the simulation process. It also does not assess the electrical transients and physical stress of wind turbine components. Despite its limitations, four large offshore wind turbines and wind farms have been successfully simulated. It is found that the 9 MW, 10 MW, 11 MW and their respective wind farms generate more energy and better capacity factor on the direct-drive than single stage-low speed generator. Furthermore, a rectangular layout of 20 wind turbines considerably impacted the excellent performance of this generator on the wind farms. Another notable outcome of the study is that higher system specifications do not always generate feasible results for wind turbines despite favourable weather conditions. For the Vestas 8 MW wind turbine, the viable percentages for increasing the size of its rated power output, rotor diameter, hub height and maximum tip speed is only 12.5%, 25% and 37.5%. The viability of these three upgrades has been confirmed by suitable graphs of power curves and feasible energy production results. Thus, these percentages confirm an 8 MW wind turbine’s attainable design limits for generating realistic energy production and capacity factor. On the contrary, a 50% increase in the above four system specifications yielded unviable capacity factor and energy production results. This is because this upgrade is too high to work successfully on the current wind turbine technology. Furthermore, the shape of the power curve from the 50% specifications is not the typical curve for wind turbines. It has been observed that increasing the value of maximum tip speed beyond 143 m/s and the rotor diameter beyond 246 m give rise to an unusual power curve. Concerning wind speed for high energy production, an average daily minimum and maximum wind speed of 4.58 m/s and 15.08 m/s yielded good results. Given the prevailing trend of designing large wind turbines, findings in this study are particularly helpful in understanding how capacity factor, energy production and energy losses are affected by the size of system specifications. Not only that, but these findings also have fundamental concepts that can be used to optimize the design of large offshore wind turbines. The study is equally valuable for determining suitable weather conditions and wind power potential for large offshore wind farm sites. / Dissertation (MEng (Electrical Engineering))--University of Pretoria, 2020. / Electrical, Electronic and Computer Engineering / MEng (Electrical Engineering) / Unrestricted

Le gouvernement français a fixé pour objectif que 23% de la consommation énergétique proviendraitdes énergies renouvelables, y compris les énergies renouvelables marines pour 2020. Huit parcs éoliensen mer sont prévus le long des côtes françaises Atlantique-Manche, parmi lesquels le site de Dieppe-LeTréport dans la partie orientale de la Manche. Afin de mieux connaître la structure et le fonctionnementde cet écosystème avant l'installation du parc éolien, ma thèse est axée sur la construction de modèlesde réseau trophique à l’aide du logiciel Ecopath sur ce site d’implantation en comparaison avec deshabitats benthiques similaires en Manche. La collecte de nouvelles données sur les compartimentsbiologiques (zooplancton, suprabenthos, méiofaune, benthos et poissons démersaux) est essentielle.Ainsi, quatre campagnes (étés 2014/2015, hivers 2015/2016) ont permis d'estimer la contribution dechaque groupe zoologique dans deux habitats benthiques principaux : les graviers ensablés/sablesgraveleux et les sables moyens sur le site (environ 30 km²) correspondant à deux communautésbenthiques largement répandues en Manche. La macrofaune a été échantillonnée avec une benne VanVeen, le suprabenthos avec un traîneau Macer-Giroq modifié avec une station dans chaque habitatbenthique (échantillonnage jour et nuit) et les poissons avec un chalut à perche. Au total, 1 584 poissonsdémersaux ont été recueillis et leurs contenus stomacaux ont été examinés. Les résultats montrent quele site se distingue par la forte contribution des bivalves en termes de biomasses et que les crustacés sontdes proies préférentielles des poissons. Ce lien est discuté à travers l’analyse du réseau trophique avecun focus sur les espèces consommées et non consommées de communautés benthiques, et la notion decul de sac trophique. / The French government has set a target of 23% of energetic consumption derived from renewable energysources including Marine Renewable Energy for 2020. Eight offshore wind farms (OWF) are plannedalong the Atlantic-English Channel French coasts and among them Dieppe-Le Tréport site in the easternpart of the English Channel. In order to gain further knowledge on the ecosystem structure andfunctioning before the OWF installation, my PhD thesis is focused on the construction of an EcopathModel on the wind farm site in comparison with similar benthic habitats from the English Channel. Thecollection of new data on biological compartments (zooplankton, suprabenthos, meiofauna, benthos anddemersal fishes) are essential. Four cruises (summers 2014 /2015 and winters 2015 /2016) allowed toestimate the contribution of each zoological group in two main benthic habitats: i.e. sandy gravels andmedium clean sands, founded on the site (about 30 km²), corresponding to two microbenthiccommunities well represented in the English Channel. Macrofauna was sampled with a Van Veen grab,suprabenthos with a modified Macer-Giroq sledge in one station from each benthic habitat (day andnight sampling) and fish with a beam trawl in ten stations. A total of 1,584 demersal fishes has beencollected and their stomach contents has been examined. The results show the importance of largebivalves in the benthic biomass whereas the crustaceans are preferential preys of fishes. This link isdiscussed within the trophic network between consumed and non-consumed species of benthiccommunities, and the concept trophic ‘cul de sac’.

Wind power is one of the most promising renewable energy sources that has gained enormous attention, especially in the electricity generation sector over the past decade in the United States. In this study Data Envelopment Analysis (DEA) is implemented to quantitatively evaluate the relative efficiencies of the 236 large utility-scale wind farms. Input- and output-oriented CCR (Charnes, Cooper, and Rhodes) and BCC (Banker, Charnes, and Cooper) models are applied to pre-determined three input and three output variables. The sensitivity analysis is conducted for the robustness of DEA by introducing seven new models with the various combinations of input and output variables of the original model. Tobit regression models are developed for the second stage of the analysis to investigate the effects of specifications of the wind turbine technologies. DEA results indicate that two-thirds of the wind farms are operated efficiently. On average, 70% of the wind farms have a considerable potential for further improvement in operational productivity by expanding these wind farm projects, 24% of them should reduce their operational size to increase their productivity level, and 6% of them are operating wind power at the most productive scale size. Nonparametric statistical tests show that the most efficient wind farms are located in Oklahoma because of the relatively high wind speed resources. Tobit regression model indicates the selection of the brand of the wind turbine has a significant contribution to the productive efficiency of the wind farms. The results of this study shed some light on the current efficiency assessments of the 236 large utility-scale wind farms in the United States and the future of wind energy for both energy practitioners and policy makers.

The growing demand for power and increased environmental concerns gave an impetus to the growth of clean and renewable energy sources like wind, solar etc. There is a remarkable increase in the penetration of wind energy systems in the last decade and this trend is bound to increase at a much faster pace in future. This ever increasing penetration of wind power generating systems pose multi-fold challenges related to operational and stability aspects of the grid. Present day wind energy systems mostly comprise of variable speed wind generators. A large fraction of present day variable speed wind turbine generators use doubly fed induction machine (DFIM). This thesis deals with modeling and grid coordination aspects of variable speed wind gener- ators. In particular, the short coming of the existing steady state equivalent circuit of a DFIM is identified and subsequently, an accurate equivalent circuit of a DFIM is proposed. Relevant mathematical basis for the proposed model is presented. The proposed steady state equivalent circuit of a doubly fed induction machine is further validated using dynamic simulations of a standalone machine. Based on the proposed equivalent circuit, two approaches for computing the initial values of state variables of a DFIM is proposed. The first approach is a linear formulation where the losses due to resistance of the stator and rotor windings are neglected. The second approach is a non-linear formulation which takes the losses into consideration. Further, analysis is carried out on grid connected doubly fed induction generators (DFIG). A framework to incorporate DFIG based variable speed wind farms in the steady state power flow analysis is proposed. The proposed framework takes into consideration important aspects such as voltage dependent reactive power limits and mode of reactive power control of associated converters. Some of the challenges in a grid connected DFIG especially during su- persynchronous mode of operation are identified. The advantages of a non-Maximum Power Point Tracking (MPPT) mode of operation under certain operating conditions is highlighted. Finally, aspects pertaining to coordination of grid connected variable speed wind generators are studied. A trust region framework to determine the reference values to the control loops of converters in a variable speed wind generator is proposed. The proposed framework identifies the reference values considering other reactive power controllers in the grid. Moreover, the proposed framework ensures that the steady state voltage stability margin is maximized. On the computational front, trust region algorithms ensure global convergence. The mathematical models and initialization algorithms proposed in this thesis are tested on standalone systems under various control scenarios. The algorithms proposed to incorporate a grid connected DFIG in steady state analysis tools have been tested on a sample 6-bus system and a practical 418-bus equivalent system of Indian southern grid.

Distance relays due to their selectivity and operating speed are used in HV/EHV line protection. The dynamic nature of Mho characteristic, which happens to be most primitive technique in line protection implemented with distance relaying, is built by using the measurement of local voltage and current signals. These signals have been influenced substantially by fault resistance and the source impedance feeding the line. In case of different generation sources, the source impedance and fault characteristic also change accordingly. Environmental benefit of wind turbine technology is making it a potential source of energy. These wind turbine-generating units (WTGU) use rugged induction/synchronous machines along with power electronics converters as controlling equipment. This gives a new challenge to distance relays, as the fault current contribution of these sources depends on the converter operational principle. In this thesis a typical wind farm of Indian systems are modeled in an IN-HOUSE tool developed as part of fault analysis on wind farm system. Directly connected and front-end converter based wind turbines with their interconnections are modeled in this simulation tool. Fault voltage and current waveforms are obtained for all types of wind turbine-generating units with both radial and LILO (Loop in Loop out) connection. PSCAD based modeling has been done for DFIG type of wind turbines. The fault waveforms are generated to evaluate relay performance. Five case studies having both Radial and Loop in Loop out (LILO) connection of wind farms are simulated. These case studies generate approximately 20000 cases, which are analyzed for distance relay performance studies. In addition, the analysis is further verified on relay hardware having three characteristics, namely Self Polarized Mho (SPM), Quadrature Polarized Mho (QPM) and Quadrilateral (QUAD) characteristics. The detailed studies are carried out in this thesis to ensure and suggest the system operators with appropriate relay characteristics to be used for transmission line protection in the case of wind farms interconnected to Grid. Based on the studies carried out in the thesis, LILO connection has no impact on distance relay characteristic. In radially connected wind farms, grid side relay will operate reliably for all types of faults. It has been recommended in the thesis that wind farm side distance relay characteristics should be adjusted based on the types of wind turbines (Type-1, Type-2, Type-3 and Type-4). Based on the investigations carried out in the thesis, voltage based phase selector has been recommended for Type-4 WTGU based wind farms.

In recent years, the electric power industry around the world is changing continuously due to transformation from regulated market structure to deregulated market structure. The main aim of the transformation of electric supply industry under open access environment is to overcome the some of the limitations faced by the vertically integrated system. It is believed that this transformation will bring in new technologies, integration of other sources of energy such as wind, solar, fuel cells, bio-gas, etc., which are self sustainable and competitive, and better choice for the consumers and so on. As a result, several new issues and challenges have emerged. One of the main issues in power systems is to support reactive power for maintaining the system voltage profile with an acceptable margin of security and reliability required for system operation. In this context, the thesis addresses some of the problems related to planning and operation of reactive power in power systems. Studies are mainly focused on steady state operation of grid systems, grid connected wind farms and distribution systems as well. The reactive power support and loss allocation using Y-bus approach is proposed. It computes the reactive power contribution from various reactive sources to meet the reactive load demand and losses. Further, the allocation of reactive power loss to load or sink buses is also computed. Detailed case studies are carried out on 11-bus equivalent system of Indian southern region power grid under different loading conditions and also tested on 259-bus equivalent system of Indian western region power grid. A comparative analysis is also carried out with the proportional sharing principle and one of the circuit based approach in the literature to highlight the features of the proposed approach. A new reactive power loss index is proposed for identification of weak buses in the system. The new index is computed from the proposed Y-bus approach for the system under intact condition as well as some severe contingencies cases. Fuzzy logic approach is used to select the important and severe line contingencies from the contingency list. The validation of weak load buses identification from the proposed reactive power loss index with that from other well known existing methods in the literature such as Q-V sensitivity based modal analysis and continuation power flow method is carried out to demonstrate the effectiveness of the proposed index. Then, a short-term reactive power procurement/optimal reactive power dispatch analysis is also carried out to determine the optimum size of the reactive compensation devices to be placed at the weak buses for reactive compensation performance analysis in the system. The proposed approach is illustrated on a sample 5-bus system, and tested on sample 10-bus equivalent system and 72-bus equivalent system of Indian southern region power grid. A comprehensive power flow analysis of PQ type models for wind turbine generating units is presented. The different PQ type models of fixed/semi-variable speed wind turbine generating units are considered for the studies. In addition, the variable speed wind turbine generating units are considered in fixed power factor mode of operation. Based on these models, a comparative analysis is carried out to assess the impact of wind generation on distribution and transmission systems. 27-bus equivalent distribution test system, 93-bus equivalent test system and SR 297-bus equivalent grid connected wind system are considered for the studies. Lastly, reactive power coordination for voltage stability improvement in grid connected wind farms with different types of wind turbine generating units based on fuzzy logic approach is presented. In the proposed approach, the load bus voltage deviation is minimized by changing the reactive power controllers according to their sensitivity using fuzzy set theory. The fixed/semi-variable speed wind turbine generating units are also considered in the studies because of its impact on overall system voltage performance even though they do not support the system for voltage unlike variable speed wind generators. 297-bus equivalent and 417-bus equivalent grid connected wind systems are considered to present the simulation results. A comparative analysis is also carried out with the conventional linear programming based reactive power optimization technique to highlight the features of the proposed approach.