Fault Current Limiting Method for MMC-HVDC Based on Virtual Inductance

The large high-voltage direct current (HVDC) transmission system, which relies on modular multilevel converters (MMC) as key equipment, is encountering challenging issues such as rapid evolution of DC faults, excessive current rise, and difficulties in fault isolation and network self-healing. To address these concerns, this paper focuses on the half-bridge MMC and proposes an analog DC-based virtual inductance control (VIC) strategy based on the mathematical expression of the reactor. This strategy responds to the change of the DC line current, thereby reducing the voltage at the outlet side of the converter and suppressing the rise of the fault current. Finally, the proposed control strategy is simulated and analyzed in a three-terminal HVDC transmission system, demonstrating its ability to effectively limit the rise of short-circuit current.