Wind energy is a relatively young but rapidly expanding industry. In order for wind generation to be cost effective, it must produce energy at a minimum cost per dollar of investment. Performance characteristics such as power output versus wind speed must be optimized in order to compete with other energy sources. Also, if the utility uses wind power for a part of its generation, the output power of these turbines must have the same high quality and reliability when it enters the utility grid. The ability to vary operating speed is important in wind generation because it allows for an optimization of the transfer of power from the wind to the turbine shaft. Doubly-fed induction generators (DFIG) are an interesting solution for variable-speed systems with limited variable speed range, and are typically used in wind energy conversion systems. / The objectives of this thesis are to implement a decoupled P-Q control of a DFIG that does not rely on mechanical sensors and to design a speed and position sensorless algorithm that is robust to variations of the values of the machine parameters. The sensorless DFIG control algorithm presented in this thesis is based on a modified phasedlock loop with an improved positioning algorithm. With the measured stator voltages, stator and rotor currents, the speed and position of the DFIG are estimated. The speed is estimated independent of machine parameters, which results in a significant improvement in speed control robustness to parameter variations. In addition, the algorithm avoids using differentiation, which significantly improves its immunity to noise and does not require the measurement of the rotor voltages. Also, it is shown that the positioning algorithm has an improved operation in generator mode. Although the accuracy of the positioning algorithm is depended on machine parameters; it is shown with the designed controller that the P-Q decoupled control is robust to changes of machine parameters. Theoretical and simulation results are validated on an experimental setup.

Background: Wind turbines (WTs) are an emerging source of renewable energy in Ontario. One concern is that aerodynamic and mechanical noise produced by the WTs results in sleep disturbance in residents living near such facilities. However, evidence to date is primarily self-reported, with no objective measures of the impact on sleep quality currently in the literature. Objective: The objective of this study was to determine if the presence of a grid connected WT is a risk factor for poor sleep quality and if wind turbine noise is associated with sleep parameters. The hypothesis was that individuals residing within fifteen hundred meters of a WT experience poorer sleep, compared to those who do not reside near a WT. Methods: A daily sleep diary and actigraphy-derived measures of sleep quality were obtained from twelve participants from a WT community in rural Ontario and ten participants from a comparison community with no wind power installations. Sound level meters were used to assess the equivalent (LAeq) and maximum (LAmax) sound pressure levels within the bedroom. A variety of statistical analysis were performed to determine co-variation between variables, noise thresholds for sleep disturbance, and risk for poor sleep quality. Results: A total of 110 person-nights and 12,971 sleep epochs were observed. Participants in the exposed group lived at a mean distance of 795 m from the closest WT (range 474 m–1085 m). Although numerous actigraphy-derived sleep parameters were poorer in the exposed group, including lower average sleep efficiency (89% vs. 92%), longer sleep onset latency (6 min vs. 4 min), and longer wake after sleep onset (42 min vs. 29 min), the differences were not statistically significant. When the data was dichotomized by quality of sleep, the prevalence of poor sleep in the exposed group was greater than in the unexposed group (22 vs. 11 per 100 person-nights), although the results of logistic regression modeling indicated that the differences were not statistically significant (after adjustment for age and sex). Findings from the analysis of sleep epochs showed an association between awakenings and LAmax (during the sleep epoch) only for noise events above 55 dBA. No significant differences in sleep parameters derived from the sleep diaries were found between the groups. Conclusion: Both actigraphy and sleep diaries can provide valuable information to understand the impact of industrial WTs on the quality of sleep for residents living in the vicinity. This pilot study had a small sample size which reduced the likelihood of identifying differences in sleep quality between the exposed and unexposed groups. Additionally, measurements were obtained during periods of relatively low wind speeds (nightly power outputs ranged from 1 to 34 MW or 0.5 to 17% capacity) thus, limiting the generalizability of the findings. Findings of poorer mean values of numerous sleep parameters in the exposed group support the need for more extensive research in the area. Low response to noise events up to 45 dBA was an interesting finding that also merits further investigation. Assessment of WT noise is complex and noise exposure measurement requires unique methods than those used for other sources of community noise.

Environmental, aesthetic and political pressures continue to push for siting off-shore wind turbines beyond sight of land, where waters tend to be deeper, and use of floating structures is likely to be considered. Savings could potentially be realized by reducing hull size, which would allow more compliance with the wind thrust force in the pitch direction. On the other hand, these structures with large-amplitude motions will make dynamic analysis both more challenging and more critical. Prior to the present work, there were no existing dynamic simulation tools specifically intended for compliant wind turbine design. Development and application of a new computational method underlying a new time-domain simulation tool is presented in this dissertation. The compliant floating wind turbine system is considered as a multibody system including tower, nacelle, rotor and other moving parts. Euler's equations of motion are first applied to the compliant design to investigate the large-amplitude motions. Then, a new formulation of multibody dynamics is developed through application of the conservation of both linear momentum and angular momentum to the entire system directly. A base body is prescribed within the compliant wind turbine system, and the equations of motion (EOMs) of the system are projected into the coordinate system associated with this body. Only six basic EOMs of the system are required to capture 6 unknown degrees of freedom (DOFs) of the base body when mechanical DOFs between contiguous bodies are prescribed. The 6 x 6 mass matrix is actually composed of two decoupled 3 x 3 mass matrices for translation and rotation, respectively. Each element within the matrix includes the inertial effects of all bodies. This condensation decreases the coupling between elements in the mass matrix, and so minimizes the computational demand. The simulation results are verified by critical comparison with those of the popular wind turbine dynamics software FAST. The new formulation is generalized to form the momentum cloud method (M- CM), which is particularly well suited to the serial mechanical N-body systems connected by revolute joints with prescribed relative rotation. The MCM is then expanded to multibody systems with more complicated joints and connection types.

Diss. (sammanfattning) Stockholm : Tekn. högsk., 2001. / Härtill 7 uppsatser.

Thesis (Ph. D.)--University of Toronto, 2007. / Source: Dissertation Abstracts International, Volume: 68-06, Section: A, page: 2278. Includes bibliographical references (leaves 173-185).

Thesis (MS)--Montana State University--Bozeman, 2009. / Typescript. Chairperson, Graduate Committee: Douglas S. Cairns. Includes bibliographical references (leaves 138-143).

Thesis (M. Eng.), Memorial University of Newfoundland, 1998. / Bibliography: leaves 169-176.

Στην παρούσα διπλωματική εργασία παρουσιάζεται μια νέα προσέγγιση της επαγωγικής μηχανής δακτυλιοφόρου δρομέα που χρησιμοποιείται σε συστήματα ανεμογεννητριών. Αρχικά γίνεται μια σύντομη παρουσίαση των ανανεώσιμων πηγών ενέργειας και ειδικότερα της αιολικής ενέργειας. Παρουσιάζονται τα είδη των ανεμογεννητριών και τα συστήματα κινητήρων που χρησιμοποιούνται σε αυτές και ακολουθεί η ταξινόμηση, η ανάλυση και ο διανυσματικός έλεγχος του μετατροπέα προς την πλευρά του δικτύου και προς την πλευρά του δρομέα της επαγωγικής γεννήτριας διπλής τροφοδοσίας (DFIG). Τέλος μελετάται μια εναλλακτική προσέγγιση της επαγωγικής μηχανής ελεγχόμενου δρομέα και στάτη από τριφασικό μετατροπέα και ακολουθεί η προσομοίωση των εξισώσεων του συστήματος με τη βοήθεια του Matlab. / This thesis presents a new approach of the wound rotor induction machine used in wind turbine systems. First we make a brief presentation of renewable energies and especially of the wind energy. We present the kinds of wind turbines and engine systems used in them, followed by classification, analysis and vector control of the inverter on the side of the grid and to the side of the rotor of double fed induction generator (DFIG). Finally, we study an alternative approach of the induction machine controlled by rotor and stator of a three-phase converter, followed by the simulation of the equations of the system with the help of Matlab.

Η παρούσα διπλωματική εργασία πραγματεύεται τη μελέτη μιας διάταξης ανεμογεννήτριας με επαγωγική μηχανή βραχυκυκλωμένου κλωβού η οποία συνδέεται μέσω dc διασύνδεσης με το δίκτυο. Τη dc διασύνδεση τη δημιουργεί ένας dc πυκνωτής και από την πλευρά της μηχανής υπάρχει ένας ac/dc πλήρως ελεγχόμενος ανορθωτής ισχύος ενώ από την πλευρά του δικτύου βρίσκεται ένας dc/ac πλήρως ελεγχόμενος αντιστροφέας ισχύος. Σκοπός της εργασίας είναι αρχικά να μελετήσουμε θεωρητικά το συνολικό σύστημα της ανεμογεννήτριας χρησιμοποιώντας το μετασχηματισμό Park για τη μοντελοποίηση του στο d-q πλαίσιο αναφοράς. Στη συνέχεια προχωρούμε στον υπολογισμό των εξισώσεων στο χώρο κατάστασης και τέλικά προτείνουμε ένα σύστημα ελέγχου το οποίο βασίζεται στους PI ελεγκτές. Τέλος, προσομοιώνουμε το παραπάνω σύστημα με τη βοήθεια της εφαρμογής Simulink του λογισμικού Matlab και μελετώντας τα αποτελέσματα, εξάγουμε τα ανάλογα συμπεράσματα. / The present thesis deals with the study of provision of wind generator with inductive machine of which is connected via dc interconnection with the network. A dc capacitor creates the dc interconnection with the network.The aim of this work is initially to study theoretically the total system of wind generator using the transformation Park for its modelling in the d-q frame of report. Afterwards we advance in the calculation of equations in the space of situation and finally we propose a system of control which is based on PI controllers. Finally, we simulate the system with the help of the Simulink application of Matlab and studying the results, we export the proportional conclusions.

Η παρούσα διπλωματική εργασία ασχολείται με την ανάλυση της λειτουργίας της ασύγχρονης τριφασικής μηχανής, την εφαρμογή σε αυτή μη γραμμικού σχήματος ελέγχου που περιλαμβάνει PI ελεγκτές, καθώς και τη μελέτη της ευστάθειάς της. Πιο συγκεκριμένα, στο πρώτο κεφάλαιο γίνεται ανάλυση των σημαντικότερων στοιχείων μιας ασύγχρονης τριφασικής μηχανής όπως τα κατασκευαστικά στοιχεία και ο τρόπος παραγωγής των διαφόρων πεδίων που οδηγούν στην περιστροφή της. Εν συνεχεία, εισάγεται και μελετάται το ισοδύναμο κύκλωμα της ασύγχρονης μηχανής κατά τη μόνιμη κατάσταση λειτουργίας της, ενώ προτείνονται και τέσσερα μαθηματικά μοντέλα που περιγράφουν την λειτουργία της κατά την μεταβατική κατάσταση. Από τα μοντέλα αυτά τα δύο προσιδιάζουν στη λειτουργία της ασύγχρονης μηχανής διπλής τροφοδοσίας (DFIG) και βραχυκυκλωμένου κλωβού (SCIG) αντίστοιχα. Μία από τις σημαντικότερες εφαρμογές των ασύγχρονων τριφασικών μηχανών είναι η χρήση τους για την πλαισίωση συστημάτων εκμετάλλευσης αιολικής ενέργειας. Στα επόμενα λοιπόν κεφάλαια λαμβάνει χώρα η μελέτη των σημαντικότερων παραγόντων που επηρεάζουν το αιολικό δυναμικό μιας περιοχής, καθώς και αναλύεται η μοντελοποίηση του ανέμου με τη χρήση της κατανομής Weibull. Ακόμη γίνεται λόγος για την εξέλιξη των ανεμογεννητριών, τους διαφόρους τύπους ανεμογεννητριών που κυκλοφορούν στις μέρες μας, καθώς και υπολογίζεται ο μέγιστος συντελεστής απόδοσης αυτών. Έχοντας ολοκληρώσει την ανάλυση των στοιχείων του ανέμου που θα μας βοηθήσουν στο σχεδιασμό του ελέγχου , προχωράμε στην απόδειξη μιας πολύ σημαντικής για τα συστήματα ιδιότητας την παθητικότητα , που κάτω από προϋποθέσεις συνεπάγεται ευστάθεια του συστήματος που την έχει. Η ιδιότητα αυτή αποδεικνύεται με δύο τρόπους και για τους δυο τύπους μηχανών που αναφέρθηκαν παραπάνω. Στο πέμπτο και ουσιαστικά τελευταίο κεφάλαιο αυτής της εργασίας αφού γίνει ανάλυση των βασικών αρχών του διανυσματικού ελέγχου προσανατολισμένου πεδίου περιγράφεται η κατασκευή μη γραμμικού σχήματος ελέγχου , για καθένα από τα δύο μοντέλα ,βασισμένο στα παραπάνω και με κύριο στόχο τη μεγιστοποίηση της παραγωγής ενεργού ισχύος. Περιλαμβάνεται επίσης προσομοίωση των παραπάνω σχημάτων ελέγχου και λήψη των αποκρίσεων αυτών. Τέλος , παρατίθενται και οι αποδείξεις παθητικότητας των κλειστών συστημάτων που προκύπτουν από τον έλεγχο , καθώς και απόδειξη για την ευστάθεια των αντίστοιχων συστημάτων ελλείψει διέγερσης. Η εργασία ολοκληρώνεται με την εξαγωγή κάποιων χρήσιμων συμπερασμάτων. / In this diploma thesis the operation of a three phase asynchronous machine is analyzed and a nonlinear control scheme, which includes PI controllers, is applied. Additionally, a study of asynchronous machine’s stability analysis is conducted. The basic components of a three phase asynchronous machine are extensively referred at the first chapter of this thesis, such as construction characteristics and data about the magnetic field which causes machine’s rotation. The equivalent circuit of the asynchronous machine’s steady state is introduced and studied. What is more four mathematical models that best describe asynchronous machine operation during the transition, are also proposed. Two of these models approximate the operation of doubly fed induction machine (DFIG) and squirrel cage induction machine (SCIG) respectively. One of the most important use of induction machines is the exploitation of wind energy. Thus, next chapters are referred to the factors that affect a region’s wind profile and is approximated by Weibull’s distribution. Furthermore, wind turbines are classified and their evolution is analyzed. Their maximum efficiency factor is also calculated. Having completed the analysis of wind data, used in control design, a very important property of systems, called passitivity, is proved. Under appropriate conditions, passitivity guarantees system’s stability. Two different ways are used in order to prove this property for the two types of induction machine mentioned above. The fifth and last chapter of this thesis is an introduction to the basic principles of vector field oriented control. The design of a nonlinear control scheme is implemented as well, based on field oriented control and active power production’s maximization. Simulations of these control schemes and their responses are also included. Last but not least, closed loop systems’ passivity is being proved and the stability of the corresponding systems, in the absence of stimulation, is proved as well. At the end of this thesis some useful conclusions are drawn.