Methods for operating wind turbines and feeding auxiliary systems

A method for operating a wind turbine in an autonomous mode of operation, the wind turbine having a wind turbine rotor including a plurality of blades and a wind turbine generator, the method comprising:

• operating the wind turbine in the autonomous mode of operation, wherein the autonomous mode refers to a mode wherein the wind turbine is isolated from an electrical grid and is configured to operate independently from the electrical grid;
• while operating the wind turbine in the autonomous mode of operation, detecting a safe condition for operating the wind turbine when a predetermined parameter is below a threshold, wherein the predetermined parameter is one or more of:
• wind speed, an angle of attack, wind turbine loading, wind turbine vibration, or wind turbine acceleration;
• during the safe condition, generating electric power by rotating the wind turbine rotor at a first rotational speed between four (4) and eight (8) revolutions per minute by actively controlling a pitch angle of the plurality of blades while supplying at least part of the generated electric power to at least one wind turbine auxiliary system;
• while still operating the wind turbine in the autonomous mode of operation, detecting a specified condition that endangers the wind turbine, wherein the specified condition that endangers the wind turbine is detected when the predetermined parameter has reached or exceeded the threshold;
• and
• upon detection of the specified condition that endangers the wind turbine, generating the electric power supplied to the auxiliary system by rotating the wind turbine rotor at a second rotational speed equal to or less than two (2) revolutions per minute.