Reduction of edgewise vibrations using blade load signal

A method of actuating pitch of pitch adjustable rotor blades of a wind turbine, the wind turbine comprising a pitch actuator for actuating the pitch of the pitch adjustable rotor blades, the method comprising:

• receiving an edgewise load signal for each of the pitch adjustable rotor blades, the edgewise load signal being measured in a rotating reference frame;
• applying an m-blade coordinate transformation to the edgewise load signal to transform the edgewise load signal to a whirling reference frame along a first and a second reference direction;
• selecting a signal component of either the first or the second reference direction to obtain a selected signal component;
• filtering the selected signal component at either a backward whirling frequency or a forward whirling frequency to obtain a filtered signal component;
• applying an inverse m-blade coordinate transformation to the filtered signal component to obtain a pitch modification signal, wherein only a whirling mode of either backward or forward whirling is targeted in obtaining the pitch modification signal;
• and
• applying the pitch modification signal to the pitch actuator.

A wind turbine, comprising:

• a tower;
• a nacelle disposed on the tower;
• a rotor extending from the nacelle and having a plurality of pitch adjustable rotor blades disposed thereon;
• and
• a pitch actuating unit to determine a pitch modification signal to be applied to a pitch actuator for actuating the pitch of the pitch adjustable rotor blades;
• the pitch actuation unit being arranged to:
• receive an edgewise load signal for each of the pitch adjustable rotor blades, the edgewise load signal being measured in a rotating reference frame;
• apply an m-blade coordinate transformation to the edgewise load signal to transform the edgewise load signal to a whirling reference frame along a first and a second reference direction;
• select a signal component of either the first or the second reference direction to obtain a selected signal component;
• filter the selected signal component at either a backward whirling frequency or a forward whirling frequency to obtain a filtered signal component;
• apply an inverse m-blade coordinate transformation to the filtered signal component to obtain the pitch modification signal, wherein only a whirling mode of either backward or forward whirling is targeted in obtaining the pitch modification signal;
• and
• apply the pitch modification signal to the pitch actuator.

A computer program product comprising a non-transitory computer readable medium storing software code adapted to control a wind turbine when executed on a data processing system, the data processing system being adapted to perform, upon execution of the software code, an operation of actuating pitch of pitch adjustable rotor blades of a wind turbine, the wind turbine comprising a pitch actuator for actuating the pitch of the pitch adjustable rotor blades, the operation comprising:

• receive an edgewise load signal for each of the pitch adjustable rotor blades, the edgewise load signal being measured in a rotating reference frame;
• apply an m-blade coordinate transformation to the edgewise load signal to transform the edgewise load signal to a whirling reference frame along a first and a second reference direction;
• select a signal component of either the first or the second reference direction to obtain a selected signal component;
• filter the selected signal component at either a backward whirling frequency or a forward whirling frequency to obtain a filtered signal component;
• apply an inverse m-blade coordinate transformation to the filtered signal component to obtain a pitch modification signal, wherein only a whirling mode of either backward or forward whirling is targeted in obtaining the pitch modification signal;
• and
• apply the pitch modification signal to the pitch actuator.