Design of a Small-Scale SiC-based Modular Multilevel Converter for Experimental Verification of Back-to-back Network Studies

This paper presents the design, control, and experimental validation for a full SiC-based modular multilevel converter (MMC). The prototype, rated at 700 Vdc and power of 21 KVA, can be used to study the operation of MMC as a single converter or in a back-to-back (BTB) configuration. The prototype is assembled as two identical MMCs, each consisting of 12 half-bridge (HB) submodules and a control board that independently operates the MMC as a rectifier or an inverter. An overview of the structure of the sub-modules, signal flow, and protection scheme are included. Moreover, the hierarchical control principles of the MMC-based BTB system are presented to achieve power regulation and submodule (SM) capacitor balancing. Finally, prototype experimental results are given to verify the validity of the prototype and control methods.