Topics in large-signal behavior of power electronic converters and systems

Abstract

A variety of topics in large-signal and system-level power electronics are explored. First, the load-sharing problem for converters with parallel- and series-connected outputs is defined and explained. Requirements for load-sharing behavior are illustrated graphically. Many classes of switching converters are capable of load-sharing aside from current-programmed-mode (CPM) converters, including but not limited to discontinuous-mode (DCM) pulse-width-modulated (PWM) converters and resonant converters. The input filter problem is studied for high-power-factor rectifiers (HPFRs) based on the DCM flyback converter. Such HPFRs require an input filter to reduce switching noise conducted to the AC line, but the filter can degrade the power factor and interfere with converter operation. The analysis allows filter design that minimizes and balances these effects. Intuitive and analytical approaches are given and compared. The analytical approach uses phase plane methods usually used for resonant converter analysis. Although the filter design is for a specific converter, the approach is applicable to any HPFR. A single-quadrant negative resistor is synthesized from a DCM flyback converter. This circuit is simple, efficient, and can handle power levels over 100W. A design procedure and small-signal analysis are given. Additionally, a set of large-signal dynamic circuit models are presented for DCM PWM converters. A general impedance synthesizer is developed based on a four-quadrant switching converter. This circuit is used to create the negative resistance pseudoinverter, which puts power onto the AC line for sale to a utility. To develop the pseudoinverter, the concept of load reduction is employed. Potential stability problems are studied and a solution implemented. The synthesis of self-contained reactive components is also studied. Extensive experimental verification substantiates the majority of the concepts in this dissertation. Simulation is also used to support some of the analysis.