Subsynchronous interactions in power networks with multiple DFIG-based wind farms

This paper exposes relevant characteristics of the stability boundary associated to subsynchronous control interactions when multiple DFIG-based wind farms are radially connected to a series compensated transmission line. It is shown that the stability boundary is a convex hypersurface in the parameter space defined by the compensation level and the number of wind turbines in service at each wind farm (WF). A comprehensive multi-parameter analysis is carried out, revealing the effect of key parameters such as the location of the WFs and the transmission infrastructure, the gains of the WF controllers, the internal collector impedances and the wind speed on the stability boundary. These results also show that the convexity is a robust property of the boundary. The methodology is applied on a generic power system with two wind farms and on a case study based on a practical scenario, reproducing and explaining behaviors reported previously in practical systems.