Singular Perturbation and Complex Torque Analyses of Doubly Fed Induction Generator With Additional Inertia Control

ABSTRACT The doubly fed induction generator (DFIG) shows multi‐time‐scale and strong nonlinearity, making its stability analysis difficult. This paper conducts small perturbation stability analysis for the single‐DFIG infinite‐bus system with additional inertia control (AIC). First, the full‐order electromagnetic transient model is constructed based on its topology and control structure. Then, the original model is reduced by using the singular perturbation method, and the validity of the simplified sixth‐order model is verified by simulation. After linearising the sixth‐order model based on the root locus and frequency response diagrams, it is found that increasing the gain coefficient K f of the AIC could improve the inertia response characteristics but weaken the system's small disturbance stability. Furthermore, a complex torque model is constructed, which reveals that the system's negative damping originates from the terminal voltage control loop. Moreover, as K f increases, the inherent damping continuously decreases, leading to further deterioration of the negative damping. As T f increases, the stability of the system initially weakens and then strengthens. This study could help understand the DFIG grid‐tied system dynamics.