AC-link Voltage Harmonic Suppression Control of Cascaded MMC and Cycloconverter Based Machine Drive System

The cascaded modular multilevel converter (MMC) and cycloconverter (CCV) based machine drive system is a potential candidate for the low-speed and high-torque applications. However, the ac-link current of the drive system contains harmonics in variable frequencies, which will induce the distortion of ac-link voltage. This paper proposes an ac-link voltage harmonic suppression control of the drive system. Based on the electrical rotor angle, proposed control applies multiple synchronous rotating frames to counteract the frequency change of subharmonics in the current error. Since the subharmonics in variable frequencies are transformed into the odd and even harmonics in fixed frequencies, proposed control strategy can extract and eliminate the ac-link voltage harmonics at different machine speeds. The simulation validates the performance of control strategy.