Weight optimization of a flying capacitor multilevel converter

Many power electronics converter applications demand for an increase in gravimetric (kW/kg) power density, such as in photovoltaic and transportation. The flying capacitor multilevel topology has a high potential for weight reduction. In this paper, both an analytical and a designed-based optimization of the overall converter weight with respect to the number of voltage levels and the switching frequency is presented. Furthermore, a highly efficient (99.2%), 15kW, 3-phase 5-level flying capacitor converter prototype with LCL output filter stage for grid connected applications is presented to experimentally validate the optimization results. The built converter achieved an outstanding gravimetric power density of 5 kW/ kg.