A new three-level switched-capacitor submodule for modular multilevel converters

Abstract

Conventionally, only one out of the two capacitors in a three-level submodule is involved in the arm current path to generate the first non-zero voltage level (E) in modular multilevel converters (MMCs). While two capacitors are connected in series to obtain the second non-zero voltage level (2E). In this paper and in order to generate the first non-zero voltage level (E); parallel-connection of the two capacitors is proposed which in turn forces the capacitors voltages to be equal, as a result the parallel-connection supports employing a single voltage sensor per the proposed module instead of using two voltage sensors which reduces the hardware and software complexity of the control system. A new switched capacitor submodule (SCSM) is proposed to enable this feature. A detailed illustration of the operational concept of the proposed architecture is presented in this work. The simulation results for an MMC with the proposed SCSM is presented to validate the proposed concept.