New 3-level submodules for a modular multilevel converter based HVDC system with advanced features

Modular multilevel converters have emerged as a viable solution over conventional voltage source converters (VSC) for applications in high voltage direct current (HVDC) transmission. Due to modular structure, the converter can reach high number of voltage levels resulting in low switching frequency and near sinusoidal voltage waveforms. This paper proposes new submodule topologies which can result in even higher voltage levels with reduced voltage stress across some switches and lower semiconductor losses. A modified modulation scheme and voltage balancing algorithm is proposed for the new topology and is validated by MATLAB/Simulink simulations. A comprehensive comparative analysis with other available submodule topologies is presented to show the added benefits.