Resonant Converters : Topologies , Dynamic Modeling and Control

Recent interest in high frequency resonant converters has prompted this exploration of aspects that have not previously been studied carefully. More specifically, this thesis examines possible methods for deriving resonant converter topologies and show how to develop dynamic models for converter behavior, demonstrates the design and implementation of control schemes based on these models. Systematic methodologies for deriving resonant converter topologies are proposed. These allow the synthesis of existing and new converters. One method proposes a switching cell from which some basic topologies are derived. A second method uses the structural symmetry of resonant converters to derive other topologies. Duality is used to complete the set of resonant converter topologies obtained by the first two methods. Relationships between dual converters are discussed, drawing attention to the sort of implementation differences that arise. Sampled-data models to describe the dynamics large signals and of small perturbations away from a cyclic steady state are developed. Associated transfer functions are obtained. Application of the model is illustrated by correlating the analysis with simulation results obtained for a series resonant dc-dc converter. The modeling technique used has also been generalized to include other power electronic circuits. A discrete microprocessor-based controller designed using the above dynamic model has been built and tested on a simulation of a series resonant dc-dc converter, set up on MIT's Parity Simulator. The control methods implemented are state feedback and periodic output feedback, each designed to achieve a specified set of closed-loop poles. Two implementations of the controller have been tested, one using the the Parity Simulator Generalized Controller and the other using a Compupro microcomputer. Thesis Co-supervisors: Dr. John G. Kassakian Professor of Electrical Engineering Dr. George C. Verghese Associate Professor of Electrical Engineering