Utilization of Hoe robust and damping controllers with notch filters to reduce SSR in doubly-fed induction generator wind farms

High levels of series compensation are among the most important causes of sub-synchronous resonance (SSR) in wind farms based on doubly-fed induction generators (DFIG). These oscillations can lead to system instability. Previous research has inadequately addressed this issue, particularly in the practical integration of SSR reduction methods concerning varying operational conditions. This study categorizes these gaps by focusing on the limitations of existing strategies and presents a suitable combined method to address the shortcomings in previous research. Through rigorous eigenvalue analysis, we identify an effective combined method from various combined approaches based on their ability to stabilize sub-synchronous modes without adversely affecting other oscillatory modes. Our proposed method employs a synergistic framework that combines an Hoe robust controller, a damping controller, and a sub-synchronous notch filter, applied simultaneously in both the rotor side converter (RSC) and the grid side converter (GSC). The simulation results demonstrate that this approach reduces the average initial fluctuations of key operational parameters in the wind farm by >50 % and provides strong performance under uncertain conditions.