Thesis (Ph.D.) - University of Queensland, 2006. / Includes graphs in back pocket. Includes bibliography.

Approved for public release; distribution is unlimited / The main focus in the design of the next generation combatant, DD(X), is the US Navy's proposed Integrated Power System (IPS) which includes an all-electric propulsion drive system. The reduction of current waveform harmonics is critical in combatant propulsion systems such as the IPS. One method of reducing the current harmonics is to utilize a multilevel converter topology. The multi-level converter, as compared to a standard converter, features low dv/dt losses and low switching losses. This thesis examines the design, construction and testing of two multi-level converters operated in tandem, called a Cascaded Multi-Level Converter (CMLC). A digital logic switching circuit is designed and constructed to control the CMLC during the operational testing phase. The CMLC is demonstrated in a three-phase high-voltage configuration with 178.5 V zero-to-peak voltage, 2.10 A zero-to-peak current achieved using an R-L load. / Lieutenant Commander, United States Navy

M.Phil. (Electrical and Electronic Engineering) / There are two methods that can be used when power is converted from one frequency to another. One way uses a DC link as an intermediate stage and the other uses no intermediate stage. When no DC link exists, the conversion process is referred to as AC-AC conversion, (Cha, Enjeti & Ratanapanachote, 2004:2237). This method essentially chops the AC signal in a specific manner which yields an AC signal with a different frequency directly. Depending on how the AC signal is chopped, it would result in a varied number of wave shapes are constructed. The construction of these various wave shapes results in devices that can accomplish different tasks. One such device is called a unity displacement factor frequency converter (UDFFC). This research attempts to develop a model, to simulate and design a unity displacement factor frequency converter. The primary idea about this device is that the power factor or displacement factor is unity regardless of the load. There are three parts in the development of the UDFFC. The power circuit is an array or matrix of switches that link the three phase supply to the three phase load. The power circuit is interfaced to the control circuit which generates pulses that control the matrix of switches. The control circuit utilizes embedded control software that performs the control logic in a microcontroller. The development of the UDFFC has a potential to solve real power engineering problems, such as eliminating the DC link in a converter. This achieves the conversion of AC directly to AC in the absence of a DC link. The other major advantage is the variation of the output frequency to a desired value. The most important is that the displacement factor can be controlled as well.

Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Robert W. Ashton, John G. Ciezki, Douglas J. Fouts. Includes bibliographical references (p. 125-126). Also available online.

M. Tech. Electrical Engineering. / A matrix converter is a direct AC-AC forced commutated converter which uses bidirectional switches to connect two voltage systems of different voltage and frequency. It does not contain any large energy storage elements as it has no DC link between the two systems. The output frequency is theoretically dependant on the switching algorithm and not the input frequency. A combination of bi-directional switches, controlled to obtain any desired output frequencies from a fixed or variable input frequency, will serve as a versatile platform, from which more specific applications could be researched. Most literature uses simulations with ideal switches, or deal with theoretical studies of specific aspects or problems to be solved. A comprehensive study of matrix converters will include the construction of a real converter. The bi-directional switch is the cornerstone of any direct matrix converter. To be able to research matrix converters successfully, it is important to evaluate the bi-directional switch in operation, i.e. in real circuits. This study models, compares and evaluates a basic 3 to 1 matrix converter with various input and output frequencies. This is done for different input and output conditions such as different system frequencies and loads. Practical results with comments and conclusions are included.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

No description available.

No description available.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1988. / Vita. Abstract. Includes bibliographical references (leaves 68-70). Also available via the Internet.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 60-61). Also available via the Internet.