Date of Award


Degree Type


Degree Name

Master of Engineering Science


Electrical and Computer Engineering


Prof. Rajiv K. Varma

Second Advisor

Prof. Amirnaser Yazdani


Large wind farms are interfaced to the power system via weak or series-compensated transmission lines. This may lead to undesirable electrical and electromechanical interactions with the network. This thesis investigates the potential of Sub-Synchronous Resonance (SSR) in the large DFIG-based wind farms connected to series-compensated transmission lines and its alleviation at higher levels of power flow using the DFIG converter controls. The study is performed using a nonlinear mathematical model of a grid- connected Doubly-Fed Induction Generator (DFIG)-based wind-power system. This model provides an analytical platform for evaluating the stability and robustness of the wind-power system and impacts of the controller parameters. First, the nonlinear model is linearized around an equilibrium point. Then, the corresponding linearized model, implemented in MATLAB/Simulink software, is validated by comparing its results with those of the nonlinear model of the DFIG-based wind-power system in the PSCAD/EMTDC software. The linearized model will be used for eigenvalue and sensitivity analyses of the DFIG-based wind-power system with respect to controller and network parameters. By using the eigenvalue analysis and time-domain simulation results, it will be shown that SSR can be a potential problem and, with an appropriate control of the DFIG converters, the potential of SSR can be alleviated. iii



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