Highly Efficient, Full ZVS, Hybrid, Multilevel DC/DC Topology for Two-Stage Grid-Connected 1500-V PV System With Employed 900-V SiC Devices

Highly efficient, hybrid DC/DC topology, consisted of a standard interleaved boost followed by a multilevel resonant switched capacitor converter, which employs 900-V silicon carbide devices, for use in emerging, two-stage, grid-connected 1500-V photovoltaic systems is presented in this paper. The operation principle of this topology, controllability of the output voltage, and power distribution among the stages in function of the input voltage is described. Partial processing of the input energy and full zero-voltage switching (ZVS) transitions in all the switches, over the wide range of input voltages and output power, make this topology more efficient in comparison with the solutions presented in the literature. A simplified model of Coss for the prediction of ZVS conditions in high-voltage applications is presented. This model appears sufficiently accurate, yet it is also simple enough to be included in the optimization program without increasing the time consumption of calculations. Results of multivariable optimization (Pareto front) for the presented topology are provided. Previously described theoretical analysis is fully experimentally confirmed by building and measuring a 10-kW prototype of 8.26-kW/kg specific power and 404.6-cm
³
volume occupied only by the power stage components. Euro efficiency of 99.48% in nominal input/output voltage conditions is achieved.