Nonlinear Control-Based Modified BFCL for LVRT Capacity Enhancement of DFIG-Based Wind Farm

High penetration of wind power into existing grid can be attributed largely to the doubly fed induction generators (DFIG). However, their sensitive nature to the grid faults has created concern for their mass integration into the existing power system. The grid code has been imposed by the regulatory bodies and the transmission system operators to ensure the low-voltage ride through (LVRT) capability of the wind farms for stable operation. DFIGs with their popular topology of partially rated converters are unable to provide the LVRT capability alone. In this work, a nonlinear control-based modified bridge-type fault current limiter (NC-MBFCL) is proposed to enhance the LVRT capability of DFIG-based wind farms. The efficacy of the NC-MBFCL is evaluated through performance comparison with that of the conventionally controlled bridge-type fault current limiter (BFCL) and the modified BFCL (MBFCL). Extensive simulations executed in MATLAB/Simulink environment for both the symmetrical and unsymmetrical faults reveal that the proposed NC-MBFCL is very effective in enhancing the LVRT capability of DFIG-based wind farms and outperforms the conventionally controlled BFCL and MBFCL. Also, it was found that the BFCL demonstrates better performance than the MBFCL.