This dissertation presents a high-precision positioner with a novel superimposed concentrated-field permanent-magnet matrix. This extended-range multi-axis positioner can generate all 6-DOF (degree-of-freedom) motions with only a single moving part. It is actuated by three planar levitation motors, which are attached on the bottom of the moving part. Three aerostatic bearings are used to provide the suspension force against the gravity for the system. The dynamic model of the system is developed and analyzed. And several control techniques including SISO (single input and single output) and MIMO (multi inputs and multi outputs) controls are discussed in the dissertation. The positioner demonstrates a position resolution of 20 nm and position noise of 10 nm rms in x and y and 15 nm rms in z. The angular resolution around the x-, y-, and z-axes is in sub-microradian order. The planar travel range is 160 mm ?? 160 mm, and the maximum velocity achieved is 0.5 m/s at a 5-m/s2 acceleration, which can enhance the throughput in precision manufacturing. Various experimental results are presented in this dissertation to demonstrate the positioner??s capability of accurately tracking any planar trajectories. Those experimental results verified the potential utility of this 6-DOF high-precision positioner in precision manufacturing and factory automation.

The static synchronous series compensator (SSSC) is a series controller of Flexible AC Transmission Systems (FACTS). It can be controlled by Thyristors, it also has the ability of fast control adjustments and high frequency operation. Through impedance compensation, it is able to control the magnitude and directions of the real power flow in the transmission system. In order to achieve a fast and steady response for real power control in power systems, this thesis proposed a unified intelligent controller, which consists of RBFNN and GA for the SSSC to provide better control features for real power control in the dynamic operations of power systems. Finally, the simulation results of the proposed controllers is compared with the conventional proportional plus integral (PI) controllers to demonstrate the superiority and effectiveness of the unified intelligent controller.

Thesis (Ph.D.)--Memorial University of Newfoundland, 2000. / Bibliography: leaves 179-191.

Thesis (M. Phil.)--University of Hong Kong, 1989.

This report is a study of the effects of a commercial 0.13[mu] process and automotive temperature corners on a synchronous DC-DC buck converter design. The basics of switching converters will be explored with an emphasis on voltage-mode controlled feedback. A Type-III compensation network is designed using transfer function analysis to compensate for the inherent double pole introduced by an LC network. The output of the compensation network will drive a pulse width modulation comparator to vary the duty cycle of the high-side PMOS and low-side NMOS transistor switches. After the synchronous buck converter design was complete, the effect of process and temperature on efficiency, output voltage ripple, inductor peak to peak current, and output voltage load response was examined. / text

ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NV / High speed real-time data transportation is most important for telemetry systems, especially for large-scale distributed systems. This paper introduces a STDM (Sync Time Division Multiplexing) network structure for data transportation between devices in telemetry systems. The data in these systems is transported through virtual channels between devices. In addition, a proper frame format is designed based on PCM format to meet the needs of synchronization and real-time transportation in large-scale distributed telemetry systems.

Modeling of electrical machines play a very important role in a variety of applications such as performance analysis, characterization, fault diagnosis, condition monitoring and stress analysis of the machines. One of the important parameter while modeling the electrical machine is the magnetic characteristics of the core material. This plays a huge role in the performance characteristics and analysis of the electrical machines. Existing techniques available to determine the magnetic characteristics of a material are mainly Epstein and single sheet tester. These two tests are invasive and destructive method of testing the magnetic characteristics of the material. This research work takes up this problem and comes with a simple yet effective solution to determine the average magnetic characteristics of the material in the salient pole synchronous machine (SPSM). An FE model of the SPSM was developed to closely emulate the characteristics of the experimental machine. This FE model was first subjected to magnetostatic simulation under different field currents using a known magnetic material. Ampere turn distribution technique was used to determine the magnetic characteristics of the material. Following the determination of the new material, this material was used in the FE simulation of the SPSM running as a motor and a generator under varying load condition and field currents. Then these results were compared with the real machine to determine the effectiveness of the developed scheme. / Graduate

published_or_final_version / Electrical Engineering / Master / Master of Philosophy

Modeling of wind farms to determine their short circuit contribution in response to faults is a crucial part of system impact studies performed by power utilities. Short circuit calculations are necessary to determine protective relay settings, equipment ratings and to provide data for protection coordination. The plethora of different factors that influence the response of wind farms to short circuits makes short circuit modeling of wind farms an interesting, complex, and challenging task. Low voltage ride through (LVRT) requirements make it necessary for the latest generation of wind generators to be capable of providing reactive power support without disconnecting from the grid during and after voltage sags. If the wind generator must stay connected to the grid, a facility has to be provided to by-pass the high rotor current that occurs during voltage sags and prevent damage of the rotor side power electronic circuits. This is done through crowbar circuits which are of two types, namely active and passive crowbars, based on the power electronic device used in the crowbar triggering circuit. Power electronics-based converters and controls have become an integral part of wind generator systems like the Type 3 doubly fed induction generator based wind generators. The proprietary nature of the design of these power electronics makes it difficult to obtain the necessary information from the manufacturer to model them accurately. Also, the use of power electronic controllers has led to phenomena such as sub-synchronous control interactions (SSCI) in series compensated Type 3 wind farms which are characterized by non-fundamental frequency oscillations. SSCI affects fault current magnitude significantly and is a crucial factor that cannot be ignored while modeling series compensated Type 3 wind farms. These factors have led to disagreement and inconsistencies about which techniques are appropriate for short circuit modeling of wind farms. Fundamental frequency models like voltage behind transient reactance model are incapable of representing the majority of critical wind generator fault characteristics such as sub-synchronous interactions. The Detailed time domain models, though accurate, demand high levels of computation and modeling expertise. Voltage dependent current source modeling based on look up tables are not stand-alone models and provide only a black-box type of solution. The short circuit modeling methodology developed in this research work for representing a series compensated Type 3 wind farm is based on the generalized averaging theory, where the system variables are represented as time varying Fourier coefficients known as dynamic phasors. The modeling technique is also known as dynamic phasor modeling. The Type 3 wind generator has become the most popular type of wind generator, making it an ideal candidate for such a modeling method to be developed. The dynamic phasor model provides a generic model and achieves a middle ground between the conventional electromechanical models and the cumbersome electromagnetic time domain models. The essence of this scheme to model a periodically driven system, such as power converter circuits, is to retain only particular Fourier coefficients based on the behavior of interest of the system under study making it computationally efficient and inclusive of the required frequency components, even if non-fundamental in nature. The capability to model non-fundamental frequency components is critical for representing sub-synchronous interactions. A 450 MW Type 3 wind farm consisting of 150 generator units was modeled using the proposed approach. The method is shown to be highly accurate for representing faults at the point of interconnection of the wind farm to the grid for balanced and unbalanced faults as well as for non-fundamental frequency components present in fault currents during sub-synchronous interactions. Further, the model is shown to be accurate also for different degrees of transmission line compensation and different transformer configurations used in the test system.

Η παρούσα διπλωματική εργασία πραγματεύεται την μελέτη και κατασκευή ενός κυκλώματος για την οδήγηση ενός κινητήρα μαγνητικής αντίδρασης. Σκοπός είναι η μελέτη και κατασκευή ενός κυκλώματος τριφασικού αντιστροφέα τάσης για τηνλειτουργία και τον έλεγχο των στροφών ενός κινητήρα μαγνητικής αντίδρασης. Αν θέλαμε νακάνουμε μια περιγραφή του κινητήρα μαγνητικής αντίδρασης και να δώσουμε έναν ορισμό,θα μπορούσαμε να πούμε ότι: «Ο κινητήρας μαγνητικής αντίδρασης βασίζει τη λειτουργίατου στη ροπή αντίδρασης (reluctance torque), ροπή αντίδρασης ονομάζεται η ροπή που επάγεται σε ένα σιδερένιο αντικείμενο όταν κάποιο εξωτερικό μαγνητικό πεδίο αναγκάζει το αντικείμενο αυτό να ευθυγραμμιστεί με το πεδίο. Αυτή η ροπή αναπτύσσεται επειδή το εξωτερικό μαγνητικό πεδίο επάγει ένα πεδίο στο σίδηρο του αντικειμένου, το οποίο τείνει ναευθυγραμμιστεί με το μαγνητικό πεδίο που το προκάλεσε.» Αρχικά μελετώνται οι βασικές αρχές λειτουργίας του κινητήρα μαγνητικής αντίδρασης. Αναλύεται τομαθηματικό μοντέλο που διέπει τη λειτουργία του και γίνεται αναφορά στη μορφή και τα βασικά κατασκευαστικά χαρακτηριστικά του. Επίσης γίνεται μια σύντομη αναδρομή στην ιστορία των κινητήρων μαγνητικής αντίδρασης καθώς και μία σύγκριση αυτού του είδους κινητήρα με άλλουςκινητήρες εναλλασσομένου ρεύματος. Και αναλύονται τα πλεονεκτήματά του που τον καθιστούνανταγωνιστικό προς αυτούς. Στη συνέχεια γίνεται μια θεωρητική ανάλυση του κυκλώματος του τριφασικού αντιστροφέα τάσηςπου κατασκευάσαμε, καθώς και όλων των υπολοίπων κυκλωμάτων που είναι αναγκαία για τηλειτουργία του. Επιπροσθέτως αναλύεται η μέθοδος παλμοδότησης των διακοπτικών στοιχείων τουαντιστροφέα τάσης που χρησιμοποιήσαμε , και είναι η «Ημιτονοειδής Διαμόρφωση Εύρους Παλμών» Στο επόμενο βήμα αναλύουμε τον τρόπο κατασκευής του κυκλώματος του τριφασικού αντιστροφέατάσης που ακολουθήσαμε καθώς και του πλήρους κυκλώματος παλμοδότησης του. Ενώ γίνεται καιαναλυτική περιγραφή του βιομηχανικού μικροελεγκτή πουχρησιμοποιήσαμε για την παραγωγή τωνπαλμών , με τη μέθοδο της «Ημιτονοειδούς Διαμόρφωσης Εύρους Παλμών» Τέλος παραθέτουμε παλμογραφήματα και μετρήσεις που προέκυψαν από τα πειράματα πουδιενεργήθηκαν αφότου κατασκευάσαμε το κύκλωμα οδήγησης του κινητήρα μαγνητικής αντίδρασης. / The purpose of this thesis is the analysis and construction of a three phase reluctance motor drive system. At first the special characteristics of the syncronous reluctance motors are analyzed. After that there is a theoretical analysis of the three phase inverter circuit, and finally is described the construction of the drive system