Crowbarless Symmetrical Low-Voltage Ride Through Based on Flux Linkage Tracking For Brushless Doubly Fed Induction Generators

Abstract

The significant benefits of brushless doubly fed induction generators (BDFIGs) are higher reliability and lower maintenance cost due to the lack of a brush gear. Recent studies on BDFIGs have shown promising applications in wind power generation. The low-voltage ride-through (LVRT) capability of wind turbines is one of the most important properties specified in the grid codes of many countries. A crowbarless LVRT control strategy based on flux linkage tracking for a BDFIG under symmetrical voltage dips is proposed in this article. A novel and simple controller in static reference frame is presented to implement flux linkage tracking. To both suppress the control winding (CW) current and increase power winding (PW) reactive current, a time-sharing control and CW current-first control solution is proposed. In the most severe case, where the BDFIG rotor speed is 100% of the maximum rotor speed and under 100% symmetrical voltage dips, the experimental results show that the CW current peak can be limited to 2.01 p.u. of the CW current rating and the torque ripple is small during the fault. The experimental results also show the possibility of the BDFIG to ride through the severest voltage dips without extra hardware, such as a crowbar.