Investigation of Si and SiC-based Three-level Converters for Medium Voltage Applications

The neutral point clamped (NPC) converter and the modular multilevel converter (MMC) are among the most popular multilevel converter topologies for medium and high voltage applications. Conventionally, Silicon (Si) switches are used in these converters, but the usage of evolving Silicon Carbide (SiC) switches can enhance their performance. This paper investigates the impact of SiC switches on the performance of the three-level MMC and NPC converter for the medium voltage (MV) Photovoltaic system. The detailed analysis of loss distribution in the switching devices and the impact of SiC switch on the achievable converter rating is given. The obtained results for conduction and switching losses are compared for both the converters. Finally, from the obtained results, conclusions are made for the selection of devices and the converter for a given rating. The analysis is done by first obtaining the device parameters using the simulation of detailed device models using the circuit simulator and then using them to get the equations for the device losses. These equations are then incorporated into the system level simulations of both of the converters to evaluate losses.