Ground plane booster antenna technology for wireless handheld devices

This thesis is framed in the field of mobile communications and more particularly in handset antennas. The wireless industry is constantly growing, which entails challenging handset antenna specifications. Handset antennas not only have to be multi-band for satisfying the great number of communication services, but also sufficiently small as for fitting in the reduced space imposed by the handset platforms. The appearance of the MIMO (Multiple Input Multiple Output) technology, further exacerbates these challenges. In order to satisfy these requirements, this thesis proposes the use of the ground plane, inherently present in any handset platform, as the main radiator. Electrically small nonresonant elements, called along this thesis as ground plane boosters, are used to transfer energy to this ground plane. The solution removes the need of including a dedicated antenna featured by considerable dimensions, thus releasing space to integrate other antennas, as well as, other handset components, services and functionalities.Postprint (published version

Wide-area monitoring and control of future smart grids

Application of wide-area monitoring and control for future smart grids with substantial wind penetration and advanced network control options through FACTS and HVDC (both point-to-point and multi-terminal) is the subject matter of this thesis. For wide-area monitoring, a novel technique is proposed to characterize the system dynamic response in near real-time in terms of not only damping and frequency but also mode-shape, the latter being critical for corrective control action. Real-time simulation in Opal-RT is carried out to illustrate the effectiveness and practical feasibility of the proposed approach. Potential problem with wide-area closed-loop continuous control using FACTS devices due to continuously time-varying latency is addressed through the proposed modification of the traditional phasor POD concept introduced by ABB. Adverse impact of limited bandwidth availability due to networked communication is established and a solution using an observer at the PMU location has been demonstrated. Impact of wind penetration on the system dynamic performance has been analyzed along with effectiveness of damping control through proper coordination of wind farms and HVDC links. For multi-terminal HVDC (MTDC) grids the critical issue of autonomous power sharing among the converter stations following a contingency (e.g. converter outage) is addressed. Use of a power-voltage droop in the DC link voltage control loops using remote voltage feedback is shown to yield proper distribution of power mismatch according to the converter ratings while use of local voltages turns out to be unsatisfactory. A novel scheme for adapting the droop coefficients to share the burden according to the available headroom of each converter station is also studied. The effectiveness of the proposed approaches is illustrated through detailed frequency domain analysis and extensive time-domain simulation results on different test systems

Analysis and synthesis of concepts for hybrid power electronic earth fault compensators for medium voltage grids

In den vergangenen Jahren ist das Energieübertragungssystem mit der Zunahme der Produktion angewachsen. Jedes Jahr werden daher neue Übertragungsnetze in Betrieb genommen und die bereits bestehenden Übertragungsnetzwerke werden erweitert. In der Vergangenheit wurde der Strom in großen Kraftwerken zentral erzeugt und vom Hochspannungsnetz übertragen. Jetzt werden jedoch zunehmend auch große Mengen der elektrischen Energie vom NS- und MS-Netz übertragen. Die Anlagen zur Nutzung der erneuerbaren Energien sind grundsätzlich auf der Mittelspannungseben angeschlossen. Die modernen Netze müssen somit nicht nur mit einer schwankenden Stromerzeugung sondern auch mit verschiedenen Fehlern umgehen können. Mit wachsender Netzausdehnung steigt auch die Wahrscheinlichkeit für einen Fehlereintritt. Folglich müssen neue Verfahren entwickelt werden, um die Zuverlässigkeit und Stabilität der Netze auch im Fehlermodus zu verbessern. Derzeit werden oft kompensierte MS-Netze zum Schutz vor einphasigen Erdfehlern verwendet, wobei der Neutralleiter entweder über eine Drossel oder einen Widerstand mit der Erde verbunden ist. Damit kann der Fehlerstrom begrenzt und die Netze im Fehlerfall weiter betrieben werden. Gleichwohl haben auch die modernen passiven Kompensationsanlagen Probleme mit der Abstimmgenauigkeit, den Abmessungen sowie aufgrund der Komplexität des Antriebssystems. Moderne leistungselektronische Kompensationsanlagen werden zunehmend in MS-Netzen eingesetzt, um die Blindleistung zu kompensieren und nichtlineare Lastströme zu filtern. Sie können außerdem verwendet werden, um den Fehlerstrom zu kompensieren und eine optimale Ausnutzung der Übertragungskapazitäten der Leitungen zu ermöglichen. Da diese innovativen leistungselektronischen Kompensationsanlagen bei relativ hohen Frequenzen arbeiten, können außerdem wertvolle Materialien wie Kupfer und Stahl, die für die 50-Hz-Drosseln notwendig sind, eingespart werden. Diese Arbeit widmet sich der Entwicklung eines Hochleistungs-MS-Wechselrichters sowie dessen zur Kompensation notwendigen Steuerungssystems. Der Kompensator dient dabei zur Eliminierung des einpoligen Erdfehlerstromes (Grund- und Oberschwingungskomponenten) und kann daher im Übertragungssystem als Äquivalent der Petersonspule oder des Widerstands betrachtet werden. Der auf der Hilbert-Transformation basierende Steueralgorithmus wird ebenfalls erörtert.In the last years, the power generation systems have increased constantly with the increase in production. Every year new distribution networks are put into operation. The already existing networks are expanded. Moreover, in the past the power had been generated centrally in large power plants and transmitted by the high-voltage transmission grid, now vast amounts of the electric energy are handled by the low- and medium-voltage grid. The renewable energy sources are basically united in medium voltage grids. The modern grids has to be able to handle the fluctuating power generation and various sort of faults. With the growing grids the fault chance increases. Consequently, the new methods have to be developed to improve the reliability and stability of the grids in fault modes. Currently, to protect from one-phase ground faults the compensated networks are used with the neutral connected with the ground through the reactor or resistor. It allows to limit the fault current and the networks be able to be operated. Nevertheless, the modern compensation devices have the problems with the tuning accuracy, dimensions and the complexity due to the drive system. The modern power electronic devices are used in MV grids to compensate the reactive power (STATCOMs) and to filter the non-linear loads currents. They could be used to compensate the fault current and to allow the optimal utilization of lines as well. Moreover, since these converters operate at relatively high frequencies, valuable materials like copper and steal, used for 50 Hz reactors, can be saved. This work is dedicated to the development of a high-power medium-voltage power converter and its control system. This converter is used to compensate the one-phase ground fault current (main and high frequency components) and therefore is considered as the equivalent of the reactor or resistor in the classical system. The control algorithm based on the Hilbert transformation is proposed as well

Techniques for noise suppression and robust control in spin-based quantum information processors

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, February 2013."December 2012." Cataloged from PDF version of thesis.Includes bibliographical references (p. 145-160).Processing information quantum mechanically allows the relatively efficient solution of many important problems thought to be intractable on a classical computer. A primary challenge in experimentally implementing a quantum information processor is the control and suppression of environmental noise that decoheres the quantum system and causes it to behave classically. Environmental errors may be dynamically suppressed by applying coherent control pulses to the qubits that decouple the environment. However, the pulses themselves are subject to implementation errors, which hinders the ability to robustly store a complete quantum state. This thesis details results on the use of optimal control theory, noise twirling, and logical qubit encodings to design high-fidelity control pulses and decoupling sequences that are robust to implementation errors. Results are also presented that demonstrate how high-fidelity inductive control of a quantum system may be obtained with limited resonator bandwidth, with a discussion of applications to actuator-based quantum information processors. In a multi-mode design for such a processor, which allows efficient removal of entropy, a new protocol is suggested that permits robust parallel information transfer between nodes. The results detailed in this thesis apply broadly to most implementations of quantum information processing and specifically enable a new design for a spin-based multinode quantum information processor based on single-crystal molecular monolayer electron-nuclear spin systems integrated with superconducting electronics.by Troy William Borneman.Ph.D