Method for controlling an electric generator of a wind turbine

A method for operating a wind turbine, comprising:

• rotating an electric generator of said wind turbine at a known rotational speed and/or known torque at a first operating point for said electric generator based on a first amplitude and/or a first phase angle;
• controlling the electric generator by at least:
• varying the first amplitude and/or the first phase angle of a harmonic current of said electric generator, while said electric generator is rotating;
• measuring a signal indicative of a generator vibration after and/or during varying said first amplitude and/or first phase angle;
• repeating said varying and said measuring until a fixed number of signals indicative of the generator vibration are measured, wherein said repeating of the varying and measuring is performed by varying an offset to said phase angle or said amplitude;
• determining a second operating point that is different from the first operating point for said electric generator using said signals indicative of the generator vibration, wherein a ripple torque of said electric generator is reduced at said second operating point relative to said first operating point;
• and
• controlling a current of said electric generator to meet said second operating point based on a second amplitude that is different from the first amplitude and/or a second phase angle that is different from the first phase angle;
• and
• feeding electrical energy into an electrical supply grid, while said electric generator is in said second operating point,
• wherein said wind turbine further comprises a wind turbine controller and controlling the electric generator further comprises:
• implementing new parameters in said wind turbine controller based on said second operating point, wherein the new parameters include at least the second amplitude and/or the second phase angle.