An AC-AC Modular Multilevel Converter-based Partially-Rated Solid-State Transformer for Power Flow Control

Increasing penetration rate of the renewable energy resources in conjunction with emergence of new dynamic loads such as electric vehicles, necessitate more flexible, efficient, and economical operation of the power grid. To maximize utilization of the power system infrastructure in an efficient and economical way, partially-rated solid-state transformer (PSST) has been proposed to control the power flow. In this paper, new PSSTs based on the AC-AC modular multilevel converter (MMC) are proposed. The proposed PSSTs borrow the salient features of the MMC and are capable of controlling power flow of the grid. Simulation studies in the PSCAD/EMTDC software environment are carried out to validate the performance and effectiveness of the proposed MMC-based PSSTs and the supporting control methods.