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-infinity 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-infinity 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-infinity, controller to harness power from the wind with minimal fluctuations in the output electrical power and drive train torsional moments.