Addressing grid integration issues for DFIG-based WECS via multiobjective H∞ paradigm

Recent advancement in size and technology of wind energy conversion systems (WECSs) require sophisticated control systems to effectively optimize energy conversion and enhance grid integration. Doubly-fed induction generators (DFIG)-based WECS are the most promising and widely utilized technology. This study focuses on advanced controls development to identify and assess the critical loads and instabilities, and improve the WECS´s dynamic response and quality of power output by designing an H_∞ control scheme. Building on the theory of linear parameter varying (LPV) convex decomposition, the WECS is transformed into a LPV model with a convex polyhedron structure. The proposed controller is designed to meet H_∞ performance and dynamic characteristics by solving a set of linear matrix inequalities (LMIs) to synthesize the feedback gain for each vertex of the convex polyhedron. This realizes local, linear controllers that yield a global, parameter-dependent or nonlinear time-varying controller by interpolation. Simulations validate the effectiveness of the LPV-based H_∞ controller to harness power from the wind with minimal fluctuations in the output electrical power and drive train torsional moments.