A New Control Strategy of Decoupling the AC/DC Voltage-offset for Modular Multilevel Converter

For its notable advantages, the modular multilevel converter (MMC) has become a hot topic in high-voltage direct current (HVDC) research and construction. Based on the existing MMC configuration and double-loop control strategy, there's a coupling between AC/DC voltage-offset, which brings a series of problems in different engineering background. This paper proposes solutions to decouple this coupling with two steps: 1) a principle of the arm sub-module configuration is proposed to change the topology of MMC arms; 2) a new control strategy is designed for the new topology. Two 2-terminal active MMC-HVDC simulation models with different configuration is established in PSCAD/EMTDC and the efficiency of the proposed topology and control strategy is validated.