TSA based optimization to dc voltage and dc modulation for high-voltage ride-through (HVRT) of DFIG: School of Electrical Engineering and Automation, Hefei University of Technology, Hefei 230009, China

During the recovery process after the short fault at the grid side, the doubly-fed induction generator (DFIG) may suffer from overvoltage of the dc-link and over-modulation of the grid-side converter (GSC). Increasing the dc voltage reference improves the modulation of the GSC, but increases the dc overvoltage. A larger dc capacitor suppresses the dc voltage, but deteriorates the dc modulation. The PI parameters of the DFIG may also be adjusted to suppress the dc overvoltage and improve the modulation. Coordinating the dc voltage reference, the dc capacitance, and/or the PI parameters may improve the high-voltage ride-through (HVRT) capability of the DFIG, which has not been studied yet. In this paper, the analytical expression of the trajectory sensitivities of the dc voltage with respect to above parameters is newly proposed, based on which an index of the dc voltage is newly defined to select the critical parameters. Change of dc voltage reference after the grid voltage recovery is included to damp the 2nd dc overvoltage, which adds the difficulty of solving the trajectory sensitivity. The objective function combining the areas about the dc overvoltage and over-modulation is newly proposed to optimize these parameters for the HVRT of the DFIG. The proposed model is solved with the interior point method. Numerical simulation validates the accuracy of the trajectory sensitivity. The proposed index selects the critical PI parameters which reduces the optimization time, and keeping desirable control effect. Coordination of dc capacitance and dc voltage reference is effective to suppress the dc overvoltage and improve dc modulation. Further including the PI parameters helps to damp the oscillation and reduce the recovery time of the dc voltage.