Analysis of Key Influencing Parameters of Small Disturbance Stability for Doubly-Fed Induction Generator Connected to the Series-Compensated AC Grid Based on Fuzzy Rough Set Theory

With the increasing grid-connected scale of wind power, represented by doubly-fed induction generators (DFIG), some characteristics of DFIG, such as nonlinearity, switching, multiple time scales, and the interaction between the wind turbines and the series-compensated capacitance, can contribute to the sub- synchronous oscillations (SSO). Meanwhile, the difficulty in analyzing the multi-parameter coupling effect also exists when the SSO occurs. Therefore, based on fuzzy rough set theory, this paper proposes a selection algorithm to find the key influencing parameters of the small disturbance stability for the DFIG connected to the series-compensated AC grid when SSO occurs. First, the mathematical equations of the doubly-fed induction motor and the rotor side converter are modeled in the DIgSILENT simulation platform. Then, this paper gives the selection and fuzzification process of the parameters related to SSO and proposes a feature-importance-based selection algorithm for key influencing parameters according to the dependence degree. Finally, the modal analysis data from the modified 3-machine 9- bus system with DFIG and the series-compensated capacitance is employed to calculate the influence of coupling parameters on the SSO of the system and select the key influencing parameters, which demonstrates the validity and feasibility of the proposed method.