Effects of a Comprehensive Fault Current-Limitation Approach with SFCL on DC Pilot Protection

Suppressing DC fault current within the safety margin is critical for a high-voltage direct-current (HVDC) system. Our research group has proposed a comprehensive fault current-limitation (CFCL) approach, which uses the coordination of the converter controller and superconducting fault current limiter (SFCL). This paper studies the influence of the CFCL approach on DC pilot protection. The theoretical presentation of the CFCL method and DC pilot protection in a modular multilevel converter (MMC)-based HVDC is conducted, and the function of coordinating the virtual impedance and resistive SFCL to the DC fault current is analyzed. Using MATLAB, the digital model of a 320 kV MMC-HVDC with the CFCL method and DC pilot protection is constructed, and a metallic DC ground fault is imitated to test the system’s transient behaviors. From the simulation outcome, the CFCL approach can well guarantee DC fault detection speed without affecting the correct operation of the DC pilot protection in the MMC-HVDC system.