A simple control method for modular multilevel converters

In this paper a simple control method involving new insertion index selection scheme for control of Modular Multilevel Converters (MMC) is proposed. In contrast with classical closed-loop methods, where all available arm voltages are measured and used in the generation process of insertion indices, this method uses available average voltage, i.e. the arithmetic mean of available upper and lower arm voltages per leg. Thus, number of measured signals to be fed back are reduced to half. Moreover, development of available arm voltage ripple expressions along with the thorough evaluation of the proposed insertion method impact on arm voltages driving input- and output-currents are presented and discussed. Finally, analytical findings along with simulation results proved the effectiveness of the proposed method.