Suppression of Subsynchronous Resonance in a Hybrid Steam-Turbine Generator/Offshore Wind Farm System Using a Static Synchronous Compensator with a Vanadium Redox Flow Battery

A static synchronous compensator (STATCOM) joined with a vanadium redox flow battery (VRFB)-based energy storage system (ESS) is proposed to suppress subsynchronous resonance (SSR) occurring in a hybrid steam-turbine generator (STG)/offshore wind farm (OWF) system fed to an infinite bus through a series-capacitor compensated line. The OWF is based on a doubly-fed induction generator (DFIG) and the d-q axis equivalent-circuit model of the studied system under three-phase balanced loading conditions is derived to establish the complete system. A supplementary damping controller (SDC) of the STATCOM is designed by using modal control theory to improve the damping of the dominant modes of the studied system. Small-signal stability and transient simulation results of the studied system are systematically performed to demonstrate that the proposed STATCOM with the designed SDC combined with the VRFB-ESS is effective in suppressing SSR of the studied system.