DC-link-stress-aware DVR–supercapacitor scheme for voltage restoration and transient energy stabilization in PMSG wind turbines

Permanent magnet synchronous generator (PMSG)-based wind energy conversion systems (WECSs) are known for their high efficiency and full-scale converter interface and are widely used in variable-speed wind-power applications. However, grid disturbances such as voltage sag and swell degrade terminal-voltage quality and impose transient stress on the shared DC-link. To improve voltage restoration while maintaining DC-link voltage stability, this paper proposes a grid-connected PMSG-based WECS configuration incorporating a dynamic voltage restorer (DVR) in conjunction with a supercapacitor energy storage system (SCES). The SCES is coupled to the shared DC-link through a bidirectional buck–boost DC–DC converter (BBBC) to provide fast transient-energy support, and the DVR is connected in series at the generator terminals to compensate for grid-voltage disturbances. The DVR is controlled using a DC-link-stress-aware deadbeat control strategy, while the SCES control is based on a PI controller synchronized with the GSC to regulate the common DC-link voltage and manage the supercapacitor charging and discharging process. The proposed DVR–SCES system is simulated in MATLAB/Simulink R2024a and evaluated under 20% and 50% voltage sag conditions, as well as a 20% voltage swell condition. In addition, a comparative assessment is carried out against D-STATCOM–SCES configurations rated at 3 MVAr and 6 MVAr. The proposed DVR–SCES scheme maintains the terminal voltage at approximately 1 p.u. for all considered disturbances. In contrast, the D-STATCOM–SCES configurations restore the terminal voltage only to 0.90–0.96 p.u. during the 20% voltage sag and 0.58–0.66 p.u. during the 50% voltage sag, depending on their ratings. During the 20% voltage swell, the maximum terminal voltage reaches 1.12 p.u. and 1.06 p.u. for the 3 MVAr and 6 MVAr D-STATCOM–SCES cases, respectively. Furthermore, the proposed scheme has a maximum output-current deviation of approximately 0.4% and a maximum peak-to-peak DC-link voltage deviation of 2.17%, while the D-STATCOM–SCES configurations have corresponding maximum deviations of 21.9% and 4.00%. Finally, the simplified, indicative cost–performance analysis suggests that the proposed DVR–SCES configuration provides a more favorable cost–performance tradeoff than the investigated D-STATCOM–SCES configurations.