Study of Sub-Synchronous Control Interaction due to the Interconnection of Wind Farms to a Series Compensated Transmission System

An instance of severe damage to wind turbines due to Sub-Synchronous Control Interaction (SSCI) has been observed in the case of an interconnection of a wind farm to a series compensated transmission system. This paper presents the methodology to be followed to perform a SSCI study. The frequency-domain impedance scanning and the time-domain simulation approach are used to identify and verify the SSCI. It is necessary to perform transient simulations utilizing a detailed model of the Wind Turbine Generator (WTG). Typical fault types and disturbances that could trigger an unstable SSCI response of the WTG are simulated. The studies are performed on the IEEE Second Benchmark Model. The study compares the time-domain response of a wind farm comprised of Type 3 Doubly Fed Induction Generator (DFIG) WTGs with that of a wind farm comprised of Type 4 (Full converter) WTGs as far as SSCI is considered.