Fault Ride-Through Strategy for Hybrid Cascaded HVdc Systems Based on Controllable LCC

This paper proposes a fault ride-through (FRT) strategy for hybrid cascaded high-voltage direct current (HVDC) systems using a controllable line-commutated converter (CLCC). Unlike conventional LCCs prone to commutation failures during AC faults, the CLCC provides forced commutation and ensures stable operation. When combined with series-connected modular multilevel converters (MMCs), it also limits transient overcurrents and overvoltages in vulnerable submodules. Modeling and control principles are outlined, and simulations under various fault conditions confirm that the CLCC both eliminates commutation failures and reduces MMC stress, enabling reliable FRT. These results highlight the CLCC’s potential to improve the resilience and engineering feasibility of future hybrid HVDC systems.