Modeling and analysis of a three-phase ZVS full bridge DC-DC converter

The main goal of this thesis is to derive mathematical models which describe the static and dynamic behavior of three-phase zero-voltage-switching (ZVS) full bridge (FB) converters, which are commonly used in high power applications. The analyzed circuit uses star-connected transformers and a hybdrige rectifier, which enhances efficiency by reducing the number of conducting diodes with respect to traditional full bridge rectifiers. Switching flow graph (SFG) nonlinear modeling technique combines average and linearization operations with signal flow graphs theory; such technique is basically graphical, which makes the analysis intuitive and relatively easy. The operating modes of the circuit and the steps to derive any switching flow graph are presented. The switching flow graph of the circuit under study in then built and the static and dynamic models are derived from it. Lastly, time-domain current and voltage waveforms are analyzed to get design equations of components; the design of a prototype for future measurements is done and simulations are provided to verify the validity of the mathematical models.