A Novel Control Method for MMCs Connected to the AC System

The modular multilevel converter based high voltage direct current (MMC-HVDC) technology has the advantages of independent control of active and reactive power, fast and flexible response, and strong expansibility. It is widely used in wind power transmission, power grid interconnection, passive network power supply and long-distance large-capacity transmission. The control method of MMC is one of the key factors affecting the operation performance of transmission system. Therefore, the control method of converter station in VSC-HVDC system is studied. A new perspective of H-MMC is introduced to reconstruct the traditional MMC topology, and the 'u
dc
+ i
ac
' control method suitable for MMC is proposed to realize the high-precision control of MMC arm current. Therefore, this paper summarizes the topology and working principle of traditional MMC and MMC from a new perspective. Then, a 'u
dc
+ i
ac
' control method suitable for MMCs connected to the AC system is proposed, and the feasibility and applicability of the proposed method are verified by modeling and simulating on PSCAD/EMTDC platform.