Enhanced Control Strategies for Improving Low Fault Ride-Through Capability of Grid-Connected Doubly Fed Induction Wind Turbines

The DFIG faces challenges in providing fast and accurate support during grid voltage fluctuations. Severe voltage dips can trigger peak currents, which may damage the converter equipment and even lead to the disconnection of turbines from the grid. This paper deeply analyzes the transient characteristics of stator flux dynamics under voltage dips and identifies the transient component of the rotor-induced EMF as the primary cause of rotor overcurrent. To address this issue, an improved control strategy is proposed that utilizes stator current as a rotor voltage compensation method to effectively suppress rotor overcurrent. Furthermore, an LVRT hardware protection scheme, combining both Crowbar and Chopper circuits, is designed to handle converter capacity limitations during deep voltage dips. The proposed control strategy and protection scheme are validated through simulations conducted on the Matlab/Simulink platform, demonstrating their effectiveness and accuracy.