Investigation and design of modular multilevel converter in AFE mode with minimized passive elements

This paper investigates design procedure of modular multilevel converter (MMC) in active front-end (AFE) mode of operation. The design in performed trying to minimize the amount of passive elements including arm inductances and submodule capacitances. This has been done using basic controllers needed for operation of MMC in AFE mode, without employing any additional controller in the circuit. In other words, the design is taking advantage of properly locating arm inductance and submodule capacitance magnitudes with respect to intrinsic resonance phenomenon in MMC converter. A model is developed in MATLAB/Simulink environment in order to show feasibility of the proposed design and also to have a comparison between the proposed MMC AFEs and the formal designs. The comparison in case of the shown case study reveals 90% reduction in arm inductance magnitude and 40% reduction in submodule capacitance values at the expense of adding filter inductaces with much smaller size.