Sub-synchronous oscillations (SSOs) in doubly-fed induction generator (DFIG)-based series compensated power systems are mainly caused by sub-synchronous control interaction (SSCI). SSCI is the most recently found type of sub-synchronous resonances. In this article, SSCI is elaborated and investigated by performing eigenvalue analysis on a mathematically modeled DFIG system. The occurrence of SSCI is observed and the results of eigenvalue analysis are validated through a down-scaled 7.5-kW experimental setup of a grid-connected DFIG. Based on the analysis, the proportional control parameters of the rotor-side converter (RSC) are found to be very sensitive towards the sub-synchronous modes of the system. The results obtained from both the simulation and the experimental analysis show that if the sensitive proportional parameters of the RSC are tuned properly, then the DFIG system can become immune to the SSCI for any level of series compensation.
- Doubly-fed induction generator (DFIG)
- eigenvalue analysis
- rotor-side converter (RSC)
- sub-synchronous control interaction (SSCI)