Performance Analysis of an Improved Flux-Coupling-Type SFCL in a Medium-Voltage Wind Turbine Generation System

This paper proposes an improved flux-coupling-type superconducting fault current limiter (FC-SFCL) with multiple working modes, and investigates the efficacy of the improved FC-SFCL in guarding a medium-voltage wind turbine generation system (WTGS). The improved FC-SFCL is mainly consisting of a coupling inductance with superconducting and conventional coils, two high-speed switches, a shunt resistance and an additional limiting resistance. Under normal circumstances, the improved FC-SFCL shows little impedance to not disturb the system. In terms of fault severities, the two high-speed switches are flexibly and separately controlled to change the current paths, and the improved FC-SFCL can appear two-level limiting impedances to affect the system's transient response. The performance validation of the improved FC-SFCL in a 35 kV class WTGS is done. From the theoretical derivation and simulation assessment, the results well testify the effectiveness of the improved FC-SFCL. The fault currents in the WTGS are timely suppressed to reasonable levels, and the fluctuations in the power and torque of the WTGS are visibly reduced. A beneficial voltage quality improvement is to maintain the grid connection of the WTGS and make it ride through the serious short circuit fault successfully.