Full-SiC Flying Capacitor Boost Converter for 1500 V multi-string PV inverter

Flying capacitor converters are not widely used in PV applications, however they could bring interesting performances. The design of a three-level flying capacitor DC/DC converter is then studied in this paper, the objective being the realization of the first stage (20 kW DC/DC booster) of a two stages 1500 VOC multi-string inverter. The efficiency being critical for both stages in order not to penalize the overall efficiency, technical choices leading to the DC/DC converter realization have been conducted to reach a high peak efficiency (>99.5%). The analytical calculations in this paper have shown that the use of SiC devices allows to reach high efficiencies with higher power densities (higher switching frequency) than with Si devices. The realization of a full-SiC 2x 20 kW DC/DC converter is discussed in this paper, the peak efficiency of 99.55% experimentally measured is in accordance with our predictions.