Improving the LVRT capability of the DFIG-based wind turbines during fault

Doubly fed induction generators (DFIG) are widely used in wind energy conversion. Due to low voltage during fault, these generators may have sudden disconnection, which damages the grid stability. Therefore, many technologies for improving low voltage ride through LVRT capability of this generator have been proposed, in recent years. LVRT capability ensures no loss of production during and after a normal fault. Such a capability cause wind turbines to withstand certain duration and percentage of voltage dips.

This paper proposes a method that sustain DFIG synchronization after clearing a fault, with minimal additional equipment and changes in control strategy. Therefore, the turbine can be reconnected to grid very quickly after faults. Another advantage of this method is the possibility of feeding local load during fault. Using this method also keeps the generator in safe operation area (SOA) during fault and voltage recovery periods, and thus improves the turbine behavior and the LVRT capability.

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