Assessment and enhancement of grid fault-induced torsional oscillations for induction generator-based wind turbines

This paper investigates the torsional levels of the doubly-fed induction generator (DFIG) and the fixed speed induction generator (FSIG) initiated by network faults. The inclusion of the turbine-generator mutual damping is investigated for the DFIG, and FSIG. For the DFIG the significance of a detailed representation of the grid-side input filter and the DC-link capacitor are studied. A method is proposed to mitigate the torsional oscillations of the turbine-generator shaft system using a minor control loop (MCL) strategy. PSCAD-EMTDC studies demonstrate that the proposed controller can alleviate the risk of torsional oscillations. A conventional power system stabilizer (PSS) requires identification of four parameters, however the proposed controller requires only two parameters (MCL gain and washout time constant).