Integrated control algorithm for fast and accurate detection of the voltage sag with low voltage ride-through (LVRT) enhancement for doubly-fed induction (DFIG) based wind turbines

Low voltage ride-through (LVRT) is one of the essential aspects of grid codes for integrating doubly-fed induction generators (DFIG) to achieve reliable and uninterrupted electrical power generation. The detection time of the voltage sag is one of the crucial aspects for the LVRT improvement of the DFIG. This paper introduces a second-order generalized integrator (SOGI), quadrature signal generator (QSG) with a frequency locked loop (FLL) based algorithm to detect the symmetrical voltage sag fast and accurately. The proposed SOGI-QSG-FLL-based voltage sag detection algorithm (VSDA) works under a second-order band-pass filter with an alfa-beta stationary reference frame. The proposed VSDA is integrated with the novel feed-forward transient current compensation (FFTCC) scheme with an advanced interval type-2 fuzzy logic-proportional integral (IT2-FLC-PI) controller to enhance the LVRT capability of the DFIG. This FFTCC scheme is activated after the detection of voltage sag by using the proposed VSDA. The proposed FFTCC feeds the uninterrupted active and reactive power to the grid and reduces the torque ripple of the DFIG. The detection time of voltage sag by using the proposed VSDA is compared with existing algorithms. The experimental results are also presented to validate the proposed algorithm.