Three-Level NPC Converter Switch-Open-Circuit Fault Localization for PMSG-Based WTS Using Estimated Phase Angle Deviation Scheme

This research proposes a new method to localize multiple switch-open-circuit (SOC) faults in a high-power wind turbine system (WTS) with a permanent magnet synchronous generator (PMSG) and a three-level (3L) back-to-back (BTB) neutral point clamped (NPC) converter. SOC faults can cause significant issues like generator torque fluctuations and distorted grid currents. Early detection and isolation of these faults are crucial for maintaining system reliability and availability. The proposed method addresses this challenge by using the estimated phase-angle deviation (EPAD) between the measured phase angle (from rotor position in case of generator and from phase-locked-loop in case of grid) and the estimated phase angle from phase currents. The EPAD possesses unique behavior for fault in each switch of the converter and is insensitive to factors like torque ripple, speed fluctuations, and parameter variations. The SOC fault detection and localization algorithms have been developed for the machine side and the grid side converters (GSCs) by analyzing the EPAD. The effectiveness of this method is evaluated through comparative studies, simulations, and hardware experimentation. Additionally, tests are conducted to confirm its robustness against false fault indications.