Topologies and analysis techniques in switched-mode dc conversion (dc-to-dc), inversion (dc-to-ac), rectification (ac-to-dc), and cycloconversion (ac-to-ac) are unified in this thesis. The buck, boost, buck-boost, and flyback topologies are used to demonstrate that familiar dc converters can be extended into equivalent ac converters. Although some of these are presented as fast-switching circuits, they have also been found in slow-switching applications. Thus, topology is the unifying factor not only over four fields of power electronics, but also within each field itself.
Describing equations are used to characterize low frequency components of the inputs and outputs in fast-switching networks containing filters, excited by dc or balanced sinusoidal sources, and pulse-width-modulated by dc or balanced sinusoidal duty ratios. They are first written in the stationary (abc) reference frame and then transformed to the rotating (ofb) coordinates. In the ofb coordinates, all balanced ac converters with any number of phases are reduced to a set of continuous, time-invariant differential equations describing a two-phase equivalent.
Steady-state, dynamic, and canonical models are then solved in the rotating frame of reference. Emphasis is stressed on circuit ideality - sinusoidal outputs for sinusoidal inputs even though a switched network is nonlinear - and effects of filters on steady-state and small-signal frequency responses. These results are similar for a dc converter, inverter, rectifier, and cycloconverter of the same topology; this similarity again confirms that the four converters are closely related. The cycloconverter is thus established as the generalized converter that degenerates to the other three under special input and output frequencies.
Practical issues discussed include the realization of the switches, modification of drive and topology for bidirectionality of power flow, isolation, switched-mode impedance conversion, and measurement techniques.
