Modeling and Analysis of Sub-Synchronous Oscillation in Large Rated DFIM Based Hydro Unit Fed to Extra High Voltage Transmission Lines

The extra high voltage transmission line 765kV, the most cost-effective and widely used method for increasing the power transfer capability of long transmission lines is to employ series capacitive compensation. A doubly fed induction machine (DFIM) connected to series compensation for variable speed pumped storage plant prone to sub-synchronous oscillation (SSO). However, SSO is a significant problem that can cause electrical instability and generator shaft failure. This research discusses the use of RSC and GSC to increase power system stability. The proposed strategy of rotor side damping controller (RSDC) to improving power system stability is being developed and evaluated in preparation for the variable speed pumped storage hydropower plant. The main motive of this paper is modeling and to investigate sub-synchronous oscillations caused by series compensation in a transmission line connected to a DFIM hydro unit. The simulation is carried out and results are validated in MATLAB/Simulink environment to analyze SSO in case of different series compensation levels. The experimental validation is obtained in the laboratory on a scale down model.