System and method for detecting degradation in wind turbine generator bearings

A method for preventing damage in a bearing of a generator of an electrical power system, the electrical power system having a power conversion assembly with a first converter coupled to a second converter, the power conversion assembly electrically coupled to the generator, the method comprising:

• monitoring, via a controller, one or more electrical signals of the power conversion assembly of the electrical power system;
• calculating, via the controller, a complex rotating vector of the one or more electrical signals;
• calculating, via the controller, a complex fast Fourier transform (FFT) of the complex rotating vector;
• extracting, via the controller, one or more spectral components in frequency bands around one or more known characteristic frequencies of the bearing;
• calculating, via the controller, one or more peak magnitudes in the frequency bands;
• calculating, via the controller, one or more entropies in the frequency bands;
• comparing, via the controller, the one or more entropies to an entropy threshold;
• generating, via the controller, a fault signal for the bearing when the one or more entropies exceeds the entropy threshold;
• if the one or more entropies does not exceed the threshold, comparing, via the controller, the one or more peak magnitudes to a magnitude threshold;
• generating, via the controller, the fault signal for the bearing when the one or more peak magnitudes is less than the magnitude threshold;
• generating, via the controller, a baseline signal for the bearing when the one or more entropies is less than the entropy threshold and the one or more peak magnitudes is greater than the magnitude threshold;
• and
• in response to the fault signal being generated, implementing, via the controller, a control action.

A wind turbine power system connected to a power grid, the wind turbine power system comprising:

• a doubly-fed induction generator (DFIG) comprising a rotor, a stator, and at least one bearing;
• a power conversion assembly electrically coupled to the DFIG, the power conversion assembly comprising a rotor-side converter coupled to a line-side converter;
• a controller configured to control the wind turbine power system, the controller configured to perform a plurality of operations, the plurality of operations comprising:
• monitoring one or more electrical signals of the power conversion assembly;
• converting the one or more electricals signals to a frequency domain;
• extracting one or more spectral components in frequency bands of the frequency domain around one or more known characteristic frequencies of the bearing;
• determining one or more peak magnitudes and one or more entropies of the one or more spectral components in the frequency bands;
• comparing one or more entropies of the one or more spectral components in the frequency bands to an entropy threshold;
• generating a fault signal or a baseline signal for the bearing when the one or more entropies exceeds the entropy threshold;
• if the one or more entropies is less than the entropy threshold, comparing the one or more peak magnitudes to a magnitude threshold;
• generating the fault signal when the one or more peak magnitudes is less than the magnitude threshold;
• generating the baseline signal when the one or more entropies is less than the entropy threshold and the one of more peak magnitudes is greater than the magnitude threshold;
• and
• in response to the fault signal being generated, implementing a control action.