Impact of Series Compensated High Voltage Transmission Lines in the Operation of DFIM Based Hydro Unit

The extra high voltage transmission line 765k V, connected to a doubly-fed induction machine (DFIM) for variable speed pumped storage plant prone to sub-synchronous oscillation (SSO). Hence, the cost-effective and most popular approach to increase the power transfer ability in long transmission lines is to use series capacitive compensation. However, SSO is a significant problem that can cause electrical instability and generator shaft failure. The main motive of this paper is to investigate sub-synchronous oscillations caused by series compensation in a transmission line connected to a DFIM. The simulation is carried out and results are validated in MATLAB/Simulink to analyze SSO in case of different series compensation levels of 30%, 50%, and 90%. The experimental validation is obtained in the laboratory on scale down model of Tehri (PSPP to be commissioned) to Meerut EHV transmission line.