Fault Current Limiting Control for AC Side of MMC-HVDC Based on Switched Bang-Bang Control Scheme

Limiting the fault current level of modular multilevel converter (MMC) high-voltage direct current (HVDC) systems is beneficial to reduce the cost of current limiting devices and alleviate the stringent protection time constraints. In this paper, a fault current-limiting strategy based on switched bang-bang control for the AC side of MMC-HVDC system is proposed. The proposed method in this paper is capable of limiting the fault current to an acceptable range within short time. And it not depend on exact system model with a simple control law and small computation. In MMC-HVDC system, the designed switched bang-bang control scheme limits output current of system when it is detected to be overcurrent, and the vector controller is used during normal operation. The performance of the switched bang-bang control strategy is verified by time domain simulation using PSCAD.