This dissertation presents novel application of spintronic sensors in power system monitoring. Spintronic sensors including giant magnetoresistance (GMR) sensors and tunnel magnetoresistance (TMR) sensors are advanced in magnetic field sensing. In power industry, power-frequency magnetic fields are produced by electric power sources, equipment and power lines. Thus it is impossible for monitoring the power system by sensing the emanated magnetic field. In Chapter 2, a novel concept based on magnetoresistive (MR) sensors is proposed for transmission line monitoring. A proof-of-concept laboratory setup was constructed and a series of experiments were carried out for demonstration. The result shows the feasibility of using this power system monitoring method in reality. In order to handle complicated transmission line configuration with the proposed method, an improved current monitoring technology is proposed in Chapter 3. It is realized by developing a current source reconstruction method based on stochastic optimization strategy. This concept of current monitoring by magnetic field sensing and current source reconstruction was experimentally implemented and verified in our laboratory setup. A typical model of 500 kV three-phase transmission lines was simulated to further corroborate this technology. The reconstruction results for the 500 kV transmission lines verify the feasibility and practicality of this novel current monitoring technology based on magnetic field sensing at the top of a transmission tower for monitoring overhead transmission lines. Chapter 4 offers further improvement of the transmission-line monitoring technology. Improved technology can measure simultaneously both electrical and spatial parameters of multiple lines in real-time in a non-contact way. Two typical models of high-voltage three-phase transmission lines were simulated and the resulting magnetic fields were calculated. A source reconstruction method was developed to reconstruct the spatial and electrical parameters from the magnetic field emanated by the overhead transmission lines. The reconstruction results for the 500 kV and 220 kV transmission lines verify the feasibility and practicality of this non-contact transmission-line monitoring technology based on magnetic field sensing. As well as the high-voltage transmission-line, the technology is applied in underground power cable operation-state monitoring and energization-status identification in Chapter 5. The magnetic field distribution of the cable was studied by using finite element method (FEM) for the power cable operating in different states, i.e. current-energized state (the cable is energized and carries load current) and voltage-energized state (the cable is energized but carries no load current). Application of this method was demonstrated on an 11 kV cable with metallic outer sheath. The results highly matched with the actual source parameters of the cable. An experimental setup was constructed and the test results were used for demonstration this method. In order to enhance the applicability of the proposed power system monitoring technology in practice, magnetic flux concentrators (MFC) and magnetic shielding are studied and designed for MR sensors in Chapter 6. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

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This thesis investigates the broad theme of guaranteeing the stability of nonlinear control systems. In the first section, we describe the application of discrete controller for the stabilization of certain nonlinear stochastic control systems subject to unavailability of state measurements. In the second section, we consider input constrained nonlinear systems and characterize the region from which stabilization to the origin is possible. We then use this information to design a controller which stabilizes everywhere in this set. / Thesis / Master of Applied Science (MASc)

Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 161-170).

The current generation of Airbus long-range civil transport aircraft actively control the centre of gravity of the aircraft by adjusting the fuel distribution between the horizontal tail surface and the forward tanks in order to minimise cruise drag. Here, it is proposed that the current on-off control method could be replaced by a variable flow rate, provided by a variable speed centrifugal pump. The impacts of this at the aircraftlevelintermsof cruisefuelburnreduction,valveoperationcycle reductionand power consumption are investigated here using an extension to an existing fuel system simulationpackage and ageneric aircraftfuel systemdefinition. Itis shownthat using such a control system reduces fuel burn and the number of valve cycles, which could translate into a reduction in operating costs. The benefit of changing the controller to use tailplane trim angle directly rather than inferred centre of gravity position is assessed, and is shown to further reduce the fuel burn. It is suggested that such centre of gravity could provide significant benefits over the existing method. Steady-state anddynamic models ofcentrifugalpumps,ACinductiondrives andtypical aircraft fuel system pipework components are developed. These are validated against experimentaldatafrom a test rig of a representative system. Test rig simulation results areshowntoagreewell with thosefromexperimentation. Anewsecondary noisesource is developed for the dynamic analysis of the centrifugal pump, and a new acoustic experimental method is developed for the prediction of fluid inductance in pipework components. The results are compared against an existing CFD based method and showgood agreement. Thenewmethod representsamuch simplerexperimental means of determining the effects of fluid inertia than the existing secondary source method. Itisdemonstrated thatthedynamicbehaviourof thecentrifugalpumpis, asexpected, insignificant when considering systems containing long pipes, and that steady-state pump models are sufficient for analysing their behaviour. Thepumpmodels aregeneralisedby non-dimensionalisation,in order to maximise their applicability to analysis of aircraftfuel systems. They are applied to ageneric aircraft fuel system simulation, in order to model the behaviour of the system during a trim transfer. Thisisused todemonstratethe application of theproposed variable flowrate trim control system. The results of these simulations agree well with those used to demonstratethebenefitsof thecontrol systemattheaircraftlevel. Conceptsof system health monitoring tools are discussed with reference to the system simulations.

Thesis--Virginia Polytechnic Institute and State University, 1978. / Also available via the Internet.

In recent years, considerable attention has been focused on the application of orthogonal expansions to system analysis, parameter identification, model reduction and control system design. However, little research has been done in applying their useful properties to Power System analysis and control. This research attempts to make some inroads in applying the so called " orthogonal expansion approach " to analysis and control of Power systems, especially the latter. A set of orthogonal functions commonly called Walsh functions in system science after it's discoverer J.L. Walsh [1923] have been successfully used for parameter identification in the presence of severe nonlinearities. The classical optimal control problem is applied to a synchronous machine infinite bus system via the orthogonal expansion approach and a convenient method outlined for designing PID controllers which can achieve prespecified closed loop response characteristics. The latter is then applied for designing a dynamic series capacitor controller for a single machine infinite bus system. / Graduation date: 1993

Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2004. / Includes bibliographical references (p. 51-54).

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Dr. Ronald G. Harley; Committee Member: Dr. Bonnie Heck; Committee Member: Dr. Deepak Divan; Committee Member: Dr. Ganesh K. Venayagamoorthy; Committee Member: Dr. Miroslav Begovic. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (leaves 71-73). Also available in electronic version.