Suppression of Unstable Torsional Modes in a Hybrid Steam-Turbine Generator/Offshore Wind Farm System Using an Interline Power-Flow Controller

This paper presents the stability-analysis results of a doubly-fed induction generator (DFIG)-based offshore wind farm (OWF) connected to the bus of the synchronous generator of the IEEE Second Benchmark Model (SBM), system-1. The interline power-flow controller (IPFC) is proposed to suppress the studied system's subsynchronous resonance (SSR) and other unstable modes. The d-q axis equivalent-circuit model under three-phase balanced loading conditions establishes the studied complete system model. A damping controller of the proposed IPFC is designed using a pole-assignment approach based on modal control theory to suppress unstable SSR and other unstable modes of the studied system. To demonstrate the effectiveness of the proposed control scheme, a frequency-domain approach based on eigenvalue analysis and a time-domain scheme based on transient simulations are both performed. The simulation results show that the proposed IPFC, joined with the designed damping controller, can effectively suppress the studied system's unstable SSR phenomena and other unstable modes. © 2025 IEEE.