Switching Loss Analysis of Three-Phase Three-Level Neutral Point Clamped Converter Pole Enabled by Series-Connected 10 kV SiC MOSFETs

The recent advancement in the technology of SiC MOSFETs has spurred interest in designing compact and high switching frequency (10-20 kHz) power converters. However, grid-integration of these power converters at medium voltage (MV) scale would require a conventional transformer. With the development of new high voltage (HV) 10 kV and 15 kV SiC MOSFETs, these converters can directly interface with medium voltage (MV) grids without the need for line-frequency transformers, using simple two-level and three-level topologies. The application of these devices is currently being explored in all MV Applications (8 kV to 30 kV) like Solid State Transformer, MV Drives, Power Conditioning Systems, and MVDC isolators. This paper discusses application of 10 kV SiC MOSFETs and JBS Diodes for enabling Asynchronous Microgrid Power Conditioning System (AMPCS). This medium voltage power converter is enabled by series-connection of devices, in a Three-Level Neutral Point Clamped (3L-NPC) configuration. The voltage balancing of these series-connected devices is achieved by using RC-snubbers. This paper addresses the different conduction modes and switching sequences of a 3L-NPC pole, which is used as building block for the three-phase converter. The switching loss analysis, for various snubber values, is presented for the MOSFETs and the clamping diodes along with experimental results. This research helps in providing an overview of switching losses that are disspated through the device (and heatsink) and through the snubber resistor in a 3L-NPC convertor pole.