Hardware-based hybrid scheme to improve the fault ride through capability of doubly fed induction generator under symmetrical and asymmetrical fault

A hybrid scheme for enhancing fault ride through (FRT) capability of doubly fed induction generator under symmetrical and asymmetrical grid faults is presented. The hybrid strategy is composed of switch type fault current limiter (STFCL), braking chopper and energy storage system (ESS). The hybrid scheme guarantees the safety and controllability of rotor side converter and DC-link capacitor. The proposed FRT scheme has ability to overcome the transients and oscillation produced during the voltage dip. The hybrid strategy is capable of keeping the fault current, DC-link voltage, rotor current and voltage and electromagnetic torque within the limits and damps the oscillations during the voltage dip. The results of hybrid scheme are compared with STFCL only and are found better for the former case. MATLAB/Simulink is used for simulation of 9 MW wind turbine interfaced with grid.