Application of SFCLs to Inhibit Commutation Failure in HVdc Systems: Position Comparison and Resistance Recommendation

Commutation failure is one of the most common failures that may lead to serious consequences in high-voltage direct current (HVdc) systems. Superconducting fault current limiters (SFCLs) have been proved effective to inhibit commutation failures. In this paper, different installation positions of SFCLs are compared through three proposed evaluation indexes. The position between ac and dc systems is proved to have the best performance, and the position at the end of dc line performs moderately but costs less. Then, methods for calculating the convergence resistance of the SFCL are recommended. The theoretical method can draw the lower limit of the resistance quickly and reduce simulation time drastically when SFCLs are installed between ac and dc systems. In addition, an improved structure is presented to ensure fast recovery of an SFCL, so that the system can be restored quickly when the fault disappears. Simulations are carried out on PSCAD/EMTDC against the CIGRE HVdc benchmark system to verify the validity of the proposed installation scheme.