An Enhanced Modular Multilevel Converter with Flexible Interruption Capability of DC-side Fault

The modular multilevel converter (MMC) has a promising prospect in high voltage direct current (HVDC) transmission, while the application of MMC is limited by lacking of dc fault interruption capability. Hence, an enhanced MMC topology with the flexible interruption capability of dc fault is proposed to handle this problem on the basis of the exiting dc fault blocking technology. The enhanced flexible interruption MMC (EFI-MMC) makes two improvements in topology compared with the traditional MMC, which adapts quasi-half bridge sub-module (QHBSM) and adds the bridge arm power consumption circuit. The QHBSM can interdict the infeed current from the ac system when dc-side fault occurs by combined with reverse voltage control strategy. Meanwhile, the residual energy of arm reactor and dc smoothing reactor can be absorbed by the arm power consumption circuit to suppress the voltage stress of reactors, which can reduce the technical requirements of arrester. Finally, a 200kv EFI-MMC simulation system is built to verify the validity of the proposed topology.