Thesis (M.S.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references (ℓ. 49)

Thesis (M.S.)--University of Wisconsin--Madison, 1968. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M. Eng.), Memorial University of Newfoundland, 1998. / Bibliography: leaves 105-109.

Thesis (Ph.D.)--Washington State University, May 2006. / Includes bibliographical references (p. 102-106).

Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains xi, 94 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 90-94).

Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008. / Ayazi, Farrokh, Committee Member ; Rincon-Mora, Gabriel, Committee Chair ; Bhatti, Pamela, Committee Member ; Leach, W. Marshall, Committee Member ; Morley, Thomas, Committee Member.

M.Ing. / In this thesis, a new isolated DC-DC converter topology is designed which implements a high frequency primary tap changing transformer. This converter is designed to be implemented into renewable energy applications. Renewable or alternative energy resources are becoming more popular by necessity. The voltage generated by renewable energy resources is dependent on the weather conditions, thus the voltage may vary. This novel topology can maintain a regulated DC output voltage for a wide input voltage range by implementing a high frequency primary tap changing transformer. This converter is thus designed to accommodate the voltage changing conditions of renewable energy resources. This converter only requires output bus capacitance for DC bus stiffening. The overall required bus capacitance is therefore effectively reduced compared to other converter topologies. This isolated topology also improves the fundamental power quality. Other power quality components of this new converter are also analysed.

Reactive power compensation, as generated by capacitors, has been used to mitigate the constraints of power transmission and improve the power transfer of the transmission system of the South African power utility, Eskom‟s 66/22kV Albany-Wesley transmission system. An investigation was carried out on a number of current compensation schemes, and their operations, by means of load flow analysis. Different capacitor qualities and technologies were applied to alter the transmission line characteristics that resulted in acceptable voltage regulation. This resulted in easing the load on the lines and transformers and hence reducing line losses. For long transmission lines, utilities need voltage support, as provided for by different voltage compensators, to keep the terminal voltage within standard voltage regulation, and meet the designed power demand. The approach to large and small scale compensation was tested and the outcomes revealed distinct patterns that were used to confirm the hypothesis and improve the transfer of power. The templating temperature and thermal perspective as used by Eskom on line design was discussed and used to design a new transmission line. Load flow solutions were also used to plan and design the optimised transmission system as well as to determine the specification and location of the compensating capacitor banks. Capacitor banks, as a source of reactive power, were used to model the compensation in this research. Electrical protection and faults associated with the capacitors banks were discussed, as prevention to total blackout or load shedding on the transmission line in case of established contingency. Long term investment plans, to meet future electricity demands, require substantial investment hence a financial survey was carried out. Finally this dissertation selects a viable solution to meet the electrical power demands and then recommends a way forward for the Eskom‟s 66/22kV Albany-Wesley line.

In this thesis catastrophe theory is applied to the voltage stability problem in power systems. A general model for predicting voltage stability from the system conditions is presented and then applied to both a simple 2-bus explanatory power system and to a larger more realistic power system. The model is based on the swallowtail catastrophe which with its three control variables is able to determine the voltage stability of the system. The model is derived directly from the systems equations. The voltage stability of the system at each specified system bus is determined by comparing the values of the swallowtail catastrophe control variables with those of the unique region of voltage stability. The control variables are calculated from the system operating conditions. If the control variables specify a point inside the stability region, the system is voltage stable; otherwise it is voltage unstable. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Evolution in microprocessor technology poses new challenges for supplying power to these devices. To meet demands for faster and more efficient data processing, modem microprocessors are being designed with lower voltage implementations. More devices will be packed on a single processor chip and the processors will operate at higher frequencies, exceeding 1GHz. New high-performance microprocessors may require from 40 to 80 watts of power for the CPU alone. Load current must be supplied with up to 30A/µs slew rate while keeping the output voltage within tight regulation and response time tolerances. Therefore, special power supplies and Voltage Regulator Modules (VRMs) are needed to provide lower voltage with higher current and fast response. In the part one (chapter 2,3,4) of this dissertation, several low-voltage high-current VRM technologies are proposed for future generation microprocessors and ICs. The developed VRMs with these new technologies have advantages over conventional ones in terms of efficiency, transient response and cost. In most cases, the VRMs draw currents from DC bus for which front-end converters are used as a DC source. As the use of AC/DC frond-end converters continues to increase, more distorted mains current is drawn from the line, resulting in lower power factor and high total harmonic distortion. As a branch of active Power factor correction (PFC) techniques, the single-stage technique receives particular attention because of its low cost implementation. Moreover, with continuously demands for even higher power density, switching mode power supply operating at high-frequency is required because at high switching frequency, the size and weight of circuit components can be remarkably reduced. To boost the switching frequency, the soft-switching technique was introduced to alleviate the switching losses. The part two (chapter 5,6) of the dissertation presents several topologies for this front-end application. The design considerations, simulation results and experimental verification are discussed.