A structural & operational comparative study of converter topologies & analysis of MMC for high voltage applications

This paper presents the structural and operational comparison of line commutated converter (LCC), voltage source converter (VSC) and Modular Multi level converter(MMC) for High voltage applications and also presents the simulation model of modular multilevel converter (MMC) which is one of the most promising converter topologies for high voltage applications, especially for high-voltage direct-current (HVDC) transmission systems. The converter is characterized by a modular arm structure, formed by a cascaded connection of a large number of simple chopper cells with floating DC capacitors. These cells are called Sub-Modules (SM) and can be easily assembled into a converter for high-voltage or medium-voltage power conversion systems. A control scheme also presented for voltage balancing control and a leg total voltage control in order to achieve a stable behavior in all operating conditions. The validity and the effectiveness of the voltage control strategy are confirmed by numerical simulations. Simulations are done by using MATLAB/Simulink software.