Fault Ride-through Hybrid Controller for MMC-HVDC Transmission System via Switching Control Units Based on Bang-bang Funnel Controller

This paper proposes a fault ride-through hybrid controller (FRTHC) for modular multi-level converter based high-voltage direct current (MMC-HVDC) transmission systems. The FRTHC comprises four loops of cascading switching control units (SCUs). Each SCU switches between a bang-bang funnel controller (BBFC) and proportional-integral (PI) control loop according to a state-dependent switching law. The BBFC can utilize the full control capability of each control loop using three-value control signals with the maximum available magnitude. A state-dependent switching law is designed for each SCU to guarantee its structural stability. Simulation studies are conducted to verify the superior fault ride-through capability of the MMC-HVDC transmission system controlled by FRTHC, in comparison to that controlled by a vector controller (VC) and a VC with DC voltage droop control (VDRC).