Publication

Abstract : The interconnection between the grid and nonconventional energy sources has become more essential due to the huge rise in energy demand. In the case of wind energy, the grid integration undergoes lots of stability issues. The long-distance transmission lines are preferred since the wind farms are positioned far from the grid. However, this lowers the bulk power transfer ability of the line. The simple solution to enhance the power transfer capacity is the insertion of series capacitor in the line. However, the frightening factor in inserting the series capacitor is subsynchronous resonance (SSR) oscillations which can lead to shaft fatigue between turbine and generator set. This paper focuses on the analysis of SSR in series-compensated doubly fed induction generator (DFIG)–based wind energy conversion systems (WECSs). The detailed mathematical modelling of DFIG-based wind turbine generator (WTG) in state space form which is essential for SSR analysis is explained. The proposed model is found to be more accurate as it includes the dynamics of the rotor-side converter (RSC) and grid-side converter (GSC). The influence of series capacitive compensation in a WECs is dealt by employing eigenvalue approach. The developed model is embedded with RSC and GSC controllers for analyzing SSR effect for different operating conditions such as wind speed variations and varying compensation levels using MATLAB/SIMULINK. Also, the scaled-down model of a 2-MW wind turbine is deployed in laboratory using a grid-integrated, series-compensated 1.1-kW DFIG machine to realize the influence of series capacitive compensation. It is found that the stability of SSR is affected by different wind velocities and capacitive compensation levels.