MMC-CLCC Hybrid Direct Current Transmission System and Its Control Strategy

The full-half bridge hybrid modular multilevel converter (MMC) HVDC exhibits advantages in self-clearing DC faults and flexible access. The CLCC-based HVDC retains low-loss and high-reliability, resolving commutation failures. In this paper, a novel MMC-CLCC hybrid DC transmission system topology is presented, incorporating a full-half bridge hybrid MMC at the sending side and a CLCC at the receiving side. Appropriate control strategies are designed for various operational scenarios, including steady-state operation and AC and DC fault modes. The MMC-CLCC system's simulation model is constructed on the PSCAD platform. Its results show that the new hybrid HVDC system has all the advantages of them. Under the proposed strategy, the system can achieve stable power transmission, and has the ability of AC and DC fast fault ride-through capability.