Modeling and small-signal stability analysis of doubly-fed induction generator integrated system

Owing to their stability, doubly-fed induction generator(DFIG) integrated systems have gained considerable interest and are the most widely implemented type of wind turbines and due to the increasing escalation of the wind generation penetration rate in power systems. In this study, we investigate a DFIG integrated system comprising four modules:(1) a wind turbine that considers the maximum power point tracking and pitch-angle control,(2) induction generator,(3) rotor/grid-side converter with the corresponding control strategy, and(4) AC power grid. The detailed small-signal modeling of the entire system is performed by linearizing the dynamic characteristic equation at the steady-state value. Furthermore,a dichotomy method is proposed based on the maximum eigenvalue real part function to obtain the critical value of the parameters. Root-locus analysis is employed to analyze the impact of changes in the phase-locked loop, short-circuit ratio,and blade inertia on the system stability. Lastly, the accuracy of the small-signal model and the real and imaginary parts of the calculated dominant poles in the theoretical analysis are verified using PSCAD/EMTDC.