Operation of a modular multilevel converter with selective harmonic elimination PWM

The modular multilevel converter (MMC) is based on the cascaded interconnection of half-bridge switching sub-modules and features modular characteristics that allow its expandability while providing high quality voltage and current output waveforms and removing the need for filtering. The switching frequency of each of the individual converter sub modules being maintained low and the balancing of the capacitor voltages are important requirements for the operation of the converter. Two different modulation approaches of the converter are discussed. Selected simulation and experimental results taken from a low-power laboratory prototype are presented.