Analysis of linear switching systems using circuit transformations

Abstract

Several circuit transformation techniques are proposed to provide the equivalent linear time-invariant (LTI) circuits for most linear switching converters such as PWM converters, resonant converters, rectifiers, inverters, quantum rectifier-inverters, and cyclo-converters. In Chapter 1, brief reviews of the Power Electronics and those of modelings are provided as the introduction of this thesis. Then the outlines of the proposed circuit transformation methods are attached. In Chapter 2. the equivalent circuits or the switches in DC-DC converters are proved to be the time-varying transformers. By this model, conventional six basic PWM DC-DC converters and practical converters and analyaed with great easy without any equational manipulations.. This simple model provides the DC voltage gains and AC small signal transfer functions which are very good means for the understanding of the high order converters. In Chapter 3, the general proofs that the equivalent circuits for switches are transformers, and their applications to the AC converters such as rectifiers, inverters, and rectifier-inverters based on a new circuit D-Q transformation are proveided. Multi-switch or high order switching systems, for example, the 8th order 12 switch rectifier-inverter, can be analyzed now, otherwise it could have not been done by any conventional approaches even though the equational D-Q transformation. This is also used in finding the DC and AC transfer functions of the converters. In Chapter 4, the frequency or controlled series resonant converters are modeled and analyzed by the suggested phasor transformation. the 3rd order converters are modeled as lst order system when the switching frequency deviates from the resonant frequency and 2nd order systems when the switching frequency approaches to the resonant frequency. Various simulations and experiments verify that the proposed models have less than 10 percents errors for almost areas. In Chapter 5, the quantum rectifier invert...