SSR damping in wind farms using observed-state feedback control of DFIG converters

Abstract

This paper studies sub-synchronous resonance (SSR) in doubly-fed induction generator (DFIG)-based wind farms. The paper first briefly reviews the main types of the SSR that may occur in DFIG wind farms, namely: (1) induction generator effect (SSIGE), (2) torsional interactions (SSTI), and (3) control interactions (SSCI). It is shown that the power system is highly unstable due to the SSR mode. Therefore, a supplementary SSR damping controller (SSRDC) is designed for the grid-side converter (GSC) controller of the DFIG. The SSRDC is designed using an observer-based controller tuned through an optimal quadratic technique. Model reduction is applied to the full model of the studied power system in order to obtain a lower order model to make the SSRDC design simpler and more practical. The IEEE first benchmark model, modified to include a 100MW DFIG-based wind farm, is employed as a case study. In this work, MATLAB/SIMULINK is used for eigenvalue analysis and PSCAD/EMTDC for time-domain simulations, respectively.