Stability Enhancement of Grid-Connected Wind Power Generation Systems Using a Braking Chopper and STATCOM

Voltage instability and reactive power fluctuations represent major challenges for DFIG-based wind turbines under load variations and grid disturbances. This paper proposes an integrated fault ride-through enhancement scheme based on a STATCOM supported by a Battery Energy Storage System (BESS) and a braking chopper (BC). The STATCOM regulates the DFIG terminal voltage through dynamic reactive power compensation using a coordinated outer voltage loop and inner synchronous dq-axis current control. The BESS supports the STATCOM DC side and enables fast bidirectional power exchange, while the BC suppresses overvoltage in the DFIG back-to-back converter DC-link during fault conditions. The proposed DFIG protection scheme is modeled and evaluated in MATLAB/Simulink under step load changes and severe voltage sag and swell conditions. The results demonstrate that the proposed scheme maintains the DFIG terminal voltage at its rated value during load variations, restores it from 0.05 to 0.97 p.u. under severe voltage sag, and regulates it to 1.0 p.u. under severe voltage swell. In addition, DC-link voltage excursions are significantly reduced under severe disturbances. These findings confirm the effectiveness of the proposed strategy in enhancing fault ride-through capability and improving the dynamic stability of DFIG-based wind turbines.