Applied research of a modular multilevel converter with DC fault ride-through capability

In view of sub-modules (SMs) in larger quantities and the incapability of blocking DC fault current of the modular multilevel converter (MMC) for high voltage direct current (HVDC) transmission projects in current operation, a new modular multilevel topology based on traditional MMC topology was presented with its bridge arm consisting of two serial SMs groups constituted by half bridge sub-module (HBSM) and clamp double sub-module(CDSM) in series, incorporating features of low conduction loss and reduce additional components. Its basic parameters design and the coordination switching processes of SMs in two groups were elaborated. The corresponding model predictive control (MPC) strategy was adopted for the new MMC topology. The results show that the new MMC topology not only has the ability to block DC fault current, but also increases output level number at the same number of SMs requirements. The AC voltage output waveform is closer to a sine wave. © 2017, Central South University Press. All right reserved.