ERCOT Experience with Sub-Synchronous Control Interaction and Proposed Remediation

The Electric Reliability Council of Texas (ERCOT) has experienced sub-synchronous control interaction between Type 3 (Doubly Fed Asynchronous Generator) wind turbines and series compensated transmission lines. The event was due to an interaction between the power electronics of the Doubly Fed Asynchronous Generator and a series compensated transmission line. This paper briefly describes the Sub-synchronous Control Interaction (SSCI) event which occurred in the ERCOT region in 2009. The ERCOT region is in the process of building a major transmission expansion to support transporting wind generated energy from remote regions of the state to populated regions referred to as CREZ. Many of these CREZ lines are series compensated. The paper details a plan to protect the grid against additional sub-synchronous control interaction events while accommodating large amounts of wind generation expected to be installed in the Competitive Renewable Energy Zones (CREZ) grid.