Frequency content based monitoring of wind turbine blade pitch system

A system for monitoring operation of a wind turbine including a rotor having a blade and that rotates in a rotor plane having a plurality of sectors, the system comprising:

• one or more processors;
• and
• a memory coupled to the one or more processors and including program code that, when executed by the one or more processors, causes the system to:
• receive a time-domain signal indicative of a pitch force being applied to the blade;
• determine a first spectral density of the time-domain signal by sampling the time-domain signal to generate a discrete time-domain signal, selecting a plurality of samples from the discrete time-domain signal that are within a sampling window, and transforming the plurality of samples from a time-domain to a frequency-domain;
• determine a condition of the wind turbine based on a frequency content of the first spectral density;
• and
• in response to the condition being indicative of a problem with the wind turbine, generate an alarm signal,
• wherein the sampling window is selected from:
• a first sampling window corresponding to a wind speed that is within a predetermined wind speed range or a rate of change in the wind speed that is within a predetermined rate of change in wind speed range;
• a second sampling window corresponding to a pitch position that is within a predetermined pitch position range or a rate of change in the pitch position that is within a predetermined rate of change in pitch position range;
• and
• a third sampling window corresponding to a power output of the wind turbine that is within a predetermined power output range or a rate of change in the power output of the wind turbine that is within a predetermined rate of change in power output range.

A method for monitoring operation of a wind turbine including a rotor having a blade and that rotates in a rotor plane having a plurality of sectors, the method comprising:

• receiving a time-domain signal indicative of a pitch force being applied to the blade;
• determining a first spectral density of the time-domain signal by sampling the time-domain signal to generate a discrete time-domain signal, selecting a plurality of samples from the discrete time-domain signal that are within a sampling window corresponding to a first period of time when the blade is in a selected sector of the plurality of sectors, and transforming the plurality of samples from a time-domain to a frequency-domain;
• determining a condition of the wind turbine based on a frequency content of the first spectral density;
• and
• in response to the condition being indicative of a problem with the wind turbine, generating an alarm signal.