Loss comparison between SiC, hybrid Si/SiC, and Si devices in direct AC/AC converters

Direct AC/AC topologies for AC-to-AC power conversion benefit from the absence of DC-link capacitors and therefore high reliability as compared to traditional VSI-based topologies. Moreover, it is shown in this paper that the direct AC/AC converters also promise to provide higher efficiency than their voltage source inverter (VSI) based back-to-back (BTB) counterparts due to a dramatic reduction in switching losses. These factors allow the direct AC/AC converter to switch faster, and maintain much smaller size and lower cost relative to their competition. This paper compares the performance of three different device types (SiC, hybrid Si/SiC and Si) for use in a direct AC/AC converter. It is conjectured that traditional datasheets lack the level of detail needed for designing highly efficient direct AC/AC converters. Therefore, comprehensive loss models for all the devices are formed through a rigorous device characterization under varying (V, I, T) operating conditions. Finally, a loss comparison is performed to identify the most suitable device (among those characterized) for a specific 13 kV / 1 MW highly efficient direct AC/AC power flow controller.