A hybrid Fuzzy-PI cascade controller for transient stability improvement in DFIG wind generators
Doubly-Fed Induction Generator (DFIG) Wind Turbine (WT) can be affected by power system faults and requires crowbar protection. When the crowbar is triggered, the rotor is short circuited over the crowbar impedance, the DFIG operates as a Squirrel-cage Induction Generator (SCIG) that tends to drain large amount of reactive power from the grid during fault, potentially causing a voltage drop. In this research, therefore, we propose the use of DFIG based Low-voltage-Ride-Through (LVRT) scheme including crowbar, PSS (Power System Stabilizer), RSC (Rotor-side converter) and GSC (Grid-side converter) in order to enhance the transient stability of a grid-connected DFIG. A hybrid cascade Fuzzy-PI based controlling technique is introduced to control the Insulated gate Bipolar Transistor (IGBT) based frequency converter to enhance the transient stability. In the simulations here presented, the proposed control scheme is investigated by comparing the performance of the DFIG system with and without LVRT and damping control scheme.