Dynamic Stability Analysis of a DFIG-Based Offshore Wind Farm Connected to a Power Grid Through an HVDC Link

This paper presents the dynamic-stability analyzed results of an 80-MW offshore wind farm (OWF) connected to a power grid through a line-commutated high-voltage direct-current (HVDC) link. The studied OWF is simulated by an equivalent 80-MW doubly-fed induction generator (DFIG) driven by an equivalent wind turbine through an equivalent gearbox using an aggregation method. The damping controller of the rectifier current regulator (RCR) of the proposed HVDC link is designed by using modal control theory to contribute adequate damping to the studied OWF under various wind speeds and different disturbance conditions. A systematic analysis using a frequency-domain approach based on eigenvalue calculations and a time-domain scheme based on nonlinear model simulations is performed. The eigenvalue analysis is performed to validate the effectiveness of the designed damping controller under different wind speeds. The nonlinear model simulations are carried out to demonstrate the effectiveness of the designed damping controller under various disturbance conditions. It can be concluded from the simulation results that the proposed line-commutated HVDC link joined with the designed damping controller not only can render adequate damping characteristics to the studied DFIG-based OWF under various wind speeds but also effectively mitigate the fluctuations of the OWF under disturbance conditions.