Alternative protection system for Wind turbines with Doubly Fed Induction Generator

Nowadays, wind turbines implementing doubly fed induction generators (DFIG) occupy the largest share of the wind power market. These machines incorporate the benefits of variable speed generators in a cost-effective way but are very sensitive to grid disturbances and especially to voltage dips. To prevent the damages that grid disturbances can cause to the converter, the machines are equipped with a crowbar protection system that short-circuits the rotor. However, during the crowbar activation the rotor converter must be disconnected, so the power generation of the turbine is no longer controlled. In doing so, the crowbar impedes the turbine voltage stabilization required by most new grid regulations. This paper proposes a protection system alternative to the crowbar that allows the turbine to quickly resume normal operation, almost immediately generating reactive power, and hence contributing to the voltage stabilization.