System and method for detecting bearing insulation and ground brush health in a generator

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 and a stator;
• 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 by estimating power dissipated in a rotor-side common mode network of the wind turbine power system, the controller configured to perform a plurality of operations, the plurality of operations comprising:
• monitoring a rotor phase current and rotor-side voltage of the rotor-side converter;
• calculating a common mode power of the rotor-side common mode network using the rotor phase current and the rotor-side voltage;
• comparing the common mode power of the rotor-side common mode network to a predefined power threshold;
• and
• determining whether the common mode power of the rotor-side common mode network is indicative of degradation in at least one of a bearing insulation or a ground brush of the DFIG when the common mode power of the rotor-side common mode network is greater than the predefined power threshold;
• and
• implementing a control action when the common mode power is indicative of degradation in at least one of the bearing insulation or the ground brush, the control action comprising at least one of changing an operating set point of the wind turbine power system, shutting down the wind turbine power system, repairing at least one of the bearing insulation or the ground brush, or replacing at least one of the bearing insulation or the ground brush.