Improved crowbarless LVRT control strategy based on flux linkage tracking for brushless doubly fed induction generator

The basic principle of LVRT control strategy based on flux linkage tracking for Brushless Doubly Fed Induction Generator (BDFIG) is to make the flux linkage vector of control winding (CW) to track power winding (PW) flux linkage vector as soon as possible during grid faults, so as to ensure the safe operation of the converter. This control strategy is used in this paper for BDFIG to track the asymmetrical voltage faults. The behaviors of PW flux linkage, PW active power, reactive power and electromagnetic torque are analyzed. A proportional integral-resonant (PI-R) controller is applied for flux linkage vector amplitude tracking under asymmetrical voltage faults. Simulation results show that the ac components in amplitude of CW flux linkage vector are compensated with the proposed controller, as a result, the maximum CW current, at worst, is less than the 1.7 times rated current with the dc-link voltage allowed and the electromagnetic torque is near zero during grid faults which will reduce the press on the drive train significantly.