A novel technique is introduced to reduce the capacitor size in modular multilevel converter – high voltage direct current (MMC-HVDC) systems. In conventional MMC-HVDC, large capacitors are deployed to reduce voltage ripple leading to an increase in cost and footprints. In this research, relatively low voltage modules are integrated with MMC legs to compensate for the resulting increase in voltage ripples due to capacitor size reduction. A model predictive controller (MPC) is then used to make the combined system of MMCs with reduced capacitor size and the ripple compensation modules behave like a system with large capacitors. By integrating 4% extra full-bridge cells for ripple compensation, 50% reduction in cell capacitors is attained
