Improved DFIG Control Strategy Under Three-Phase Asymmetrical Grid Faults

In the Doubly-Fed Induction Generator (DFIG) based wind power application, the asymmetrical grid fault, e.g. the single-phase fault, phase-to-phase fault and two-phase fault, are possible to occur. As a consequence, the positive, negative and natural component of the DFIG stator flux appears during the fault period, which further endangers the safety operation of the Rotor Side Converter (RSC). In order to ensure the reliable operation of the DFIG system as well as to provide support to the grid recovery, an improved DFIG control strategy is proposed to ride through the fault at the first stage, then provide reactive power support to the grid and suppress the electromagnetic torque pulsation at the second stage. The proposed strategy does not require the complicated stator flux observer, which helps to avoid the control delay and relief the control complexity. The simulation validation of a 2 MW DFIG is conducted in MATLAB/Simulink to validate the proposed control strategy under the asymmetrical grid fault.