Impact of DFIG-Based WTs on Subsynchronous Oscillation Damping of SG Based on the Net Electrical Damping Method

Subsynchronous oscillations (SSOs) induced during the generation of wind power constitute an important problem that affects the safety and the stability of power systems. It is useful to study the impact of wind turbines on the damping of the SSOs of a synchronous generator (SG). On the one hand, the relevant studies have been based mainly on eigenvalue analysis, which is insufficient, and on the other, an examination of the general mechanism of the SSO is still lacking. Based on the net electrical damping analysis method, this paper examines the dynamic interaction between the SG and doubly fed induction generator-based wind turbines (DFIGs). The self-stabilizing damping coefficient and the mutually stabilizing damping coefficient are proposed from the perspective of the SG, and the effects of different numbers and current loop control parameters of the DFIGs on torsional modes of the SG are analyzed using different grid structures. A time-domain simulation model of DFIGs connected to a power grid is built in EMTDC/PSCAD to verify the correctness of the theoretical analysis.