A new multilevel converter with granular voltage steps and reduced number of switches

A modular multilevel converter (MMC), which provides output voltages with low harmonic contents, gives a simple structure without needing several isolated DC power supplies. However, an MMC suffers from sheer number of switches and associated electronic circuits because it requires the addition of two half-bridge submodules to one leg of the converter to add only one voltage level to the output voltage waveform. This paper proposes a granular multilevel converter (GMC) that provides required number of voltage levels with a reduced number of power switches and associated electronic circuits. In the proposed GMC, the addition of one submodule doubles the number of output voltage levels. For a specific number of submodules, the charge control algorithm of the capacitors and the switching table of the proposed converter are described. The proposed control algorithm ensures the voltage control of submodule capacitors using hysteresis controllers and the data from the transducers of the line current and capacitor voltages. The proposed converter structure, charge control algorithm, and switching table are validated by simulation case studies.