Protection Strategies for Rotor Side Converter of DFIG-based Wind Turbine during Voltage Dips

Modern wind turbines operate with variable speed and most of them are based on doubly fed induction generators (DFIG), with a back-to-back power converter. During voltage dips, the stator terminals can cause overcurrents in the rotor windings, which could threaten the converter integrity. The use of crowbar systems is the most common technique to avoid this situation. The crowbar activation disables the control of the rotor side converter during a short period of time. Once the rotor side converter is blocked, the DFIG operates like a typical induction generator and thus consumes reactive power. In this paper, the performance of the well-known crowbar protection is compared with a current compensation strategy. Results show that the current compensation strategy can have positive effects on the terminal voltages during the fault without disconnection of the rotor side converter.