DFIG based wind farm with autonomous frequency control on island operation

This paper presents an innovative DFIG which has autonomous frequency control for stand-alone operation. When the wind farm is islanded, such DFIGs synchronize to form a reliable wind farm frequency source which does not collapse when member DFIGs fail. The frequency enables frequency droop control to be implemented for load sharing. The wind farm can provide fast reserve, ready to support a weakened utility grid during system restoration. The paper identifies the instant of islanding when excess wind power can accelerate the wind turbine-generators beyond their safe speed limit to be a critical problem. This problem can be solved when the designed turbine-pitch angles control applied.