Damping of Flying Capacitor Dynamics in Multi-Level Boost DC-DC Converters

This paper presents a novel modeling approach for flying capacitor dynamics in boost-type multi-level converters (FCML-boosts) controlled by Phase Shift Pulse Width Modulation (PSPWM). By explicitly taking into account the interaction between the inductor current and the flying capacitor voltage, the model is able to reveal an underlying resonance phenomenon and to predict its frequency at each operating point. Based on such a model, whose derivation is explained in detail, both passive and active damping solutions are proposed, designed, and experimentally verified that significantly reduce the undesirable oscillations. The analytical results and the devised control solutions are tested on a 1kW, four-level, boost DC-DC converter prototype employing 200V, 48A rated EPC2034C GaN devices.