| CPC F03D 7/048 (2013.01) [F03D 7/028 (2013.01); H02J 3/381 (2013.01); H02J 3/388 (2020.01); F05B 2270/1033 (2013.01); F05B 2270/32 (2013.01); H02J 2300/28 (2020.01)] | 13 Claims |

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1. A method for operating a wind farm having a string of wind turbines electrically connectable with each other and a grid, each wind turbine including a rotor with at least one rotor blade, a power conversion system mechanically connected with the rotor, and an auxiliary subsystem, the method comprising:
operating the wind turbines in the string in an island operating mode wherein the wind turbines are not connected with the grid, and each wind turbine in the string supplies electric power generated by the power conversion system of the wind turbine to the auxiliary subsystem in the wind turbine;
determining that the rotor of one of the wind turbines in the string is exposed to a wind condition that places the wind turbine at risk of stalling at the generated electric output power of the wind turbine;
increasing the electric power generated by the power conversion system of the at-risk wind turbine by an electric power amount that is sufficient for supplying the auxiliary subsystem of at least one of the other wind turbines of the string;
determining that the rotor of the at-risk wind turbine is exposed to a further wind condition at which the risk of stalling is substantially zero if the electric output power of the conversion system of the at-risk wind turbine is reduced to the power demand of the auxiliary subsystem of the at-risk wind turbine; and
changing operation of the at-risk wind turbine to the island operating mode of the other wind turbines in the string.
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