The Effect of Bearing Impedance on Online Condition Monitoring for Rotor Winding Insulation of Doubly-Fed Induction Generator

Doubly-fed induction generators (DFIGs) play a vital role in wind power generation, yet their rotor winding insulation is susceptible to failure due to high
dv/dt
voltage from rotor-side converters and mechanical stress under varying operating conditions. While existing methods primarily focus on fault diagnosis, capable of detecting short-circuit faults but lacking in prognostic capabilities, this article delves into the development of an online condition monitoring method based on common-mode leakage current measurement. The study begins with an introduction to the model and measurement technique for winding insulation, followed by an analysis of capacitive coupling, which gives a path for high-frequency leakage current in DFIG systems. Furthermore, the article examines the impact of bearing impedance on rotor-side monitoring outcomes through theoretical analysis and simulation. Finally, the proposed method is validated through online experimentation, demonstrating its efficacy in providing real-time condition monitoring not only for rotor winding insulation but also for the state of shaft grounding devices in wind power generation systems.