Fault Ride-Through Improvement of DFIG Using GTO-thyristor Controlled Series Resistor

Dynamic performance of a doubly-fed induction generator (DFIG) connected to a power system is investigated in this thesis. The overcurrent in the rotor side and the generator voltage dip in the stator side are studied. In order for the generator to be operated stably during the faulted period, an effective approach must be developed. In this thesis, GTO-thyristor Controlled Series Resistor (GCSR) is proposed to reduce the transient rotor current in the rotor side and increase the stator voltage and reduce the steady-state rotor current during the faulted period. Moreover, in order for the DFIG to be operated under different wind speeds and under different fault voltages, feasible regions for the generator to be operated stably without overcurrent are determined. The MATLAB/Simulink/SimPowerSystems simulation software is used to simulate the dynamic performance of the grid-connected DFIG. Simulation results indicate that the stator voltage can be enhanced by the proposed GCSR at the stator. Moreover, steady-state rotor current can be reduced to be less than 1 p.u. and transient rotor current can be reduced to be less than 1.5 p.u. . Thus, the rotor side converter can be protected and the DFIG can be operated stably during faulted period.