Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 1990. / Thesis Advisor(s): Ewing, Gerald D. Second Reader: Michael, Sherif. "June 1990." DTIC Indentifier(s): Dc to dc converters, waveform generators, program listings, theses. Author(s) subject terms: dc-dc converter, quasi-resonant, Buck converter. Includes bibliographical references (p. 142-145). Also available in print.

Thesis (Ph. D., Electrical Engineering)--University of Idaho, September 2007. / Major professor: Herbert L. Hess. Includes bibliographical references. Also available online (PDF file) by subscription or by purchasing the individual file.

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

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 188-199). Also available via the Internet.

The need to incorporate significant improvements in power supplies is driven by customer demands, industry requirements and regulatory standards. For reduction in size and weight, it is imperative to process the power at a higher switching frequency. High frequency processing of power requires soft switching techniques to reduce the switching losses. Many soft switching techniques are reported in the literature to enhance the high frequency operation of power supplies. This thesis proposes novel high frequency, auxiliary circuit assisted, (a) soft-switched boost converters and their application to DC-to- DC converters and AC-to-DC front-end power factor corrected converters; and (b) zero-voltage switching (ZVS) dc link DC-to-AC inverters. In auxiliary circuit assisted soft transition converters, the auxiliary circuit processes the power during switching transitions, creating a soft transition path. In most of the proposed converters in the literature, the auxiliary circuit suffers from severe switching losses and switching stress. Discontinuous current operation of the auxiliary circuit results in parasitic oscillations between the switch capacitance and the resonant inductors increasing the stress on the devices. A zero-current switching (ZCS) auxiliary circuit and ZVS auxiliary circuit are proposed in this thesis to achieve soft transitions for the main circuit. A ZCS auxiliary circuit assisted soft transition boost converter is proposed. Operating intervals of the proposed technique in various intervals of operation are analyzed. Design constraints and considerations are discussed. A 300 W dc-to-dc boost converter and a 600 W, ac-to-dc power factor correction front-end boost converter prototype models are built in the laboratory. The experimental results confirm the theory. The resonant inductor used in the auxiliary circuit is coupled weakly to the boost inductor. Although parasitic oscillations are reduced due to the coupling, they are not completely eliminated. Hence, RC snubbers are required to suppress the oscillations. A ZVS auxiliary circuit assisted soft transition boost converter is also presented. Operating intervals of the proposed converter in various intervals of operation are analyzed. As all the parasitic elements in the circuit are accounted, parasitic oscillations are eliminated. A 300 W dc-to-dc converter operating at 250 kHz is built in the laboratory to verify the theory. A modified gating scheme to utilize the soft switching auxiliary circuit in the main power processing is also proposed. A 600 W, 100 kHz, 380 V dc, operating with universal input line voltage, ac-to-dc power factor corrected (PFC) boost converter is built using the proposed technique with modified gating algorithm. Large signal analysis to analyze the soft switching characteristics of the proposed technique during load and input voltage transients is also presented. PSPICE simulation results are presented to verify the theory. The proposed converter maintains soft switching during load and input voltage transients. The proposed auxiliary network is also extended to a family of pulse width modulated (PWM) converters. A two-switch soft switching boost converter is derived from the proposed converter. By integrating the proposed auxiliary network with a full bridge inverter, a ZVS dc link voltage source inverter (VSI) is obtained. Operating intervals of the proposed inverter in various intervals of operation for the forward power flow and reverse power flow are presented. A modified unipolar switching scheme to achieve ZVS during reverse power flow is also presented. The voltage stress on the VSI is clamped to the dc bus voltage in the proposed converter. The conduction losses are reduced as compared to other soft switching converters in the literature. As the proposed technique requires synchronized PWM operation, sine-ramp modulated PWM signals are used. Experimental results from a 120 V, 60 Hz, 300 VA, single phase VSI switching at 50 kHz are presented to verify the theory. / Graduate

M.Ing. / A non-linear load that draws distorted currents from the supply cannot be compensated with classic compensation methods, but has to be compensated by a fast power electronic source of reactive power. Power electronic switches are subjected to electrical extremes when switched from a stiff DC supply. The input voltage to a voltage fed converter can be cyclically reduced to zero by the placing of a relatively small inductor and capacitor in the input of the converter. The switching elements in the converter may change state during these zero voltage instants without incurring switching losses. A voltage fed converter with high frequency resonant link snubber and reactive loading as power filter will be discussed in this thesis. A charged capacitor forms the fast source of reactive power. The resonant link is optimized for the application. Gate turn-off thyristors are used as the switching elements and are characterized according to their turn-off losses under resonant link operation. The gate drive, control and protection circuitry for the system are discussed. A single and three phase resonant link power filter with split supplies are discussed.

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