New approach for comparing Modular Multilevel Converter submodule losses considering IGBT and SiC MOSFET devices

Abstract

Submodule losses for Modular Multilevel Converter (MMC) are frequently inferred based only on the number of components. This procedure lacks support because Submodule losses also depend on other conditions. In this work, the simulation of different Submodules with various pulse-wide modulation (PWM) techniques for MMC was performed. A new approach to fairly compare Submodule losses is proposed considering Clamp Single (CS), Clamp Double (CD), Full Bridge (FB), and Cross Connected (CC) submodule topologies. The PWM techniques applied were Phase Shifted (PS), Level Shifted Phase Disposition (LSPD), and Space Vector (SV). In addition, IGBT and SiC MOSFET devices were also considered, and DC sources were used instead of Submodule Capacitors to avoid balancing algorithms. A 9-level Three-phase MMC was developed for simulation purposes. The results show that FB, CS, and CC based MMCs present the same losses when LSPD PWM or SV PWM are applied. CD based MMC shows the overall lowest losses, except when PS PWM and IGBT are used becoming the CC based MMC the lower losses submodule in that case. These simulation results support the importance of taking a holistic approach when comparing Submodules for MMC applications.