Design of a SiC-based modular multilevel converter for medium voltage DC distriution system

The Modular Multilevel Converter (MMC) is a promising converter choice for Medium Voltage DC (MVDC) distribution systems, where SiC devices can be readily adopted taking full advantage of this semiconductor's properties. Specifically, 1.7 kV SiC MOSFETs are used to build 1kV modules operating at 100 kHz, thus eliminating the need to use multiple modules to generate a high equivalent switching frequency. Furthermore, a full-bridge configuration is used to take advantage of the additional control and energy storage capabilities that it offers when compared to conventional half-bridge modules. The full in-depth design, controls, and testing of the MMC prototype for MVDC distribution systems is presented in this paper, including among others: component selection, control algorithms, control hardware implementation, precharge and discharge circuits, and protection scheme. Experimental results are presented to demonstrate the proposed SiC-based converter.