Harmonic suppressing control strategy for MMC–HVDC

Modular multi‐level converter based high‐voltage direct current transmission (MMC–HVDC), which combines the high‐power capacity of conventional HVDC and the excellent dynamic performance of flexible HVDC, is the hotspot of research and application. Recent research finds MMC may produce harmonic current on its DC side and as the same as a line‐commutated‐converter, there is also harmonic coupling phenomenon between an MMC's AC side and DC side. In order to suppress the harmonics in MMC–HVDC and prevent the occurrence of AC–DC harmonic instability, this study analyses the current path of harmonics in an MMC. On this basis, a harmonic suppressing control strategy (HSCS) for MMC–HVDC is proposed, which includes an AC harmonic suppressing strategy and a DC harmonic suppressing strategy. PSCAD/EMTDC show that the proposed control strategy can effectively suppress the harmonics in MMC–HVDC and block the transmission of harmonics through the converter between AC and DC side, which is beneficial to the stable and reliable operation of MMC–HVDC.