Current-limiting characteristics of a modified flux-coupling type superconducting fault current limiter and its effects on the transient stability of a multi-machine power system

A modified flux-coupling type superconducting fault current limiter (SFCL) is proposed here for suppressing fault currents. The modified SFCL consists of a coupling transformer, an yttrium barium copper oxide (YBCO) pancake coil, and a controlled switch. By flexibly adjusting the controlled switch's contact states based on the system operational conditions, the coupling transformer's primary inductance as well as the YBCO coil's normal-state resistance are incorporated into the main system for current limitation. Because the modified SFCL has the advantages of resistive and inductive SFCLs, it may improve the power system's transient behavior. Hence, the SFCL's effect on the transient stability of a multi-machine power system was also theoretically investigated. Further, simulations were conducted for accessing the SFCL's performance characteristics under different fault conditions. The results show that using the proposed SFCL can effectively restrain the increased fault current and improve the bus voltage sag; meanwhile, the imitated multi-machine system's power-angle oscillation can be obviously reduced.