Modal Analysis for Subsynchronous Resonance Studies in DFIG-Based Wind Power Plants Connected to Compensated Transmission Lines and Weak Systems

In recent years, there has been a significant increase in wind power generation. One of the most used technologies in wind power plants is the double-fed induction generator (DFIG). Subsynchronous resonance (SSR) events have been reported when this technology is used, particularly when the DFIG wind farm is connected through weak grids or the transmission system has series compensation. The SSR phenomenon has been related to interactions of the DFIG control system implemented on the rotor side converter (RSC) and the grid side converter (GSC). This work aims to investigate the impact of operating conditions and tuning of critical control parameters of DFIG on SSR. The study is based on modal sensitivity analysis. Three case studies are performed, including variations in transmission line lengths, Phase-locked loop (PLL) bandwidths, transmission system compensation level, and changes in the RSC control parameters. The results show that DFIG power plants make the system more unstable when the line is long or has a high compensation level. However, the previous results are highly dependent on the tunning of control of RSC. It is possible to increase the level of compensation and the injection of active power from the DFIG by appropriately adjusting the RSC current controller.