Conceptual Design and Evaluation of a Resistive-Type SFCL for Efficient Fault Ride Through in a DFIG
To satisfy the fault ride through (FRT) requirements from both the grid side and the in-grid doubly fed induction generator (DFIG) itself simultaneously, we propose a novel FRT scheme by adopting a resistive-type superconducting fault current limiter (SFCL) connected in series with the DFIG rotor. In this paper, the conceptual design and performance evaluation of the SFCL for potential FRT applications are presented. To wind the three-phase noninductive bifilar pancake coils, 324-m SuperPower SF12100-type ReBCO tapes are adopted, whereas one Cryomech AL600-type Gifford-McMahon refrigerator is used to form a liquid nitrogen $(\text{LN}_{2})$ circulated cooling system. Two main ac loss contributions of the hysteresis loss and the flux flow loss are calculated and discussed to achieve accurate SFCL resistance modeling. Finally, case studies with regard to a 1.5-MW DFIG-based wind turbine system are carried out to verify the feasibility of the proposed SFCL-based FRT scheme. With the designed SFCL, the fault rotor current is significantly reduced from about 4396 (4.94 p.u.) to 1406 A (1.58 p.u.) during the most severe condition. The fault grid voltage is also improved from about 89.7 (0.13 p.u.) to 103.5 V (0.15 p.u.) to comply with the international grid codes. In addition, the equivalent SFCL resistance and its corresponding ac loss contributions are discussed to evaluate the integrated performance of the designed SFCL during a grid fault.