Modal Analysis of Series Compensated DFIG Based Windfarm with LQR Controller for Damping of SSR Oscillations

Recently, due to the exhaustion of fossil fuels and its increase in emission of carbon made the world to produce electricity through non-conventional energy sources like solar, wind etc. This paper deals with the problems in connecting the Wind Turbine Generator (WTG) into the grid network using the series compensated long transmission line. Inclusion of series capacitor in the transmission line causes Sub Synchronous Resonance (SSR) which results in electromechanical torque oscillations. The analysis of SSR oscillations by the insertion of different levels of series compensation for the transmission line through Eigen value approach is carried out in this paper. The response of the system is tested and improved using Linear Quadratic Regulator (LQR) controller. For this analysis, the entire wind energy series compensated power system is expressed mathematically using state space equations. The modelled system has 14 state variables. The model with LQR controller is validated using MATLAB/SIMULINK.