Power electronics is inevitably concerned with the processing of variable speed power generations such as in wind turbines, aircraft systems and naval on-board ship systems. The nature of these types of energy is distinct in that their frequency and power vary depending on the speed of the prime-mover. To make use of the variable speed energy, a power processing scheme which transforms the variable speed energy into a constant frequency power is required. There are measures such as mechanical and electrical links for such purposes. Electrical link systems are chosen in this study due to their fast responses and high reliabilities. The power conversion stage may be a dc link with a line-commutated converter, a dc link with a self-commutated inverter, or a cycloconverter. The line-commutated converter and cycloconverter power stages require a fixed frequency supply for operation whereas the self-commutated inverter is capable of stand-alone operation, thus making it attractive. Two cases of variable speed power generation using a permanent magnet synchronous machine (hereafter referred to as PMSM) and a switched reluctance machine (hereafter referred to as SRM) were studied in this dissertation. The possible use of PMSMs has been proved by the good correlation between the experimental results and the theoretically predicted results. Three different control strategies have been proposed, implemented in hardware, and experimentally verified. The efficiency of the VSCF power conversion with a self commutated converter were comparable to the one using a line-commutated converter. A novel converter topology with no dc link capacitor has been proposed for the application of SRMs to the VSCF power conversion. The proposed topology directly links the constant frequency ac source to the SRM. This feature enhances the reliability of the power conversion scheme and reduces the weight and volume of the system. The correlation between the theoretical and experimental results of some key issues showed the feasibility of the proposed VSCF power conversion scheme. In the course of the study, one stage ac to dc power conversion with a compact transformer was required for dc loads. However, phase-controlled ac to dc conversion has the disadvantages of low power factor and harmonic pollution on the utility side, particularly in the case where dc voltage regulation is required. Therefore, a novel single phase rectifier for dc load which provides ohmic isolation with a high frequency transformer is extensively investigated. The proposed scheme had a wide output variation on dc output while maintaining unity power factor and sinusoidal current in the ac input side. Three control strategies for the operation of the converter were proposed and verified experimentally. The harmonic spectra on ac and dc sides are analytically derived and experimentally proved under some load conditions. / Ph. D.

University of Macau / Faculty of Science and Technology / Department of Electrical and Electronics Engineering

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xvi, 209 p.; also includes graphics. Includes bibliographical references (p. 202-209). Available online via OhioLINK's ETD Center

Thesis (M.S.) -- Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.

Indiana University-Purdue University Indianapolis (IUPUI) / This thesis proposes a family of non-isolated bidirectional converter in order to interface dc and ac variables. Such power electronics solutions guarantee: (i) bidirectional power flow between dc and ac converter sides, (ii) independent control in both converter sides, (iii) high level of integration with a reduction of one power switch and its drive circuits, (iv) implementation of two functions by using a unique power conversion stage and (v) reduction of the capacitor losses. Despite proposing new power converter solutions, this thesis presents an analysis of the converters in terms of pulse-width-modulation (PWM) strategy, dc-link capacitor variables, and suitable a control approach. Solutions for single-phase, three-phase and three-phase four-wire systems are proposed by employing a converter leg with three switches. A possible application of this converter is in Vehicle-to-Grid (V2G) systems and interfacing dc microgrid with a utility grid. In addition to the new power electronics converters proposed in this thesis, an experimental setup has been developed for validation of the simulated outcomes. The proof-of-concept experimental setup is constituted by: DSP, Drivers & Integrating Board, Power Supply and, Power Converter & Heat-Sink .