Functional modeling for intelligent controller design for MW-class variable speed wecs with independent blade pitch regulation

Recent advancements in size and technology of wind turbines require sophisticated control systems to effectively optimize energy conversion and enhance grid integration. This article investigates output power stability of a WECS in a highly fluctuating wind environment. The aim is advanced controls development to identify and assess the critical loads and instabilities, and improve the dynamic response and quality of power output of the wind energy conversion system (WECS). Based on a performability model, a control strategy is devised for maximizing energy conversion in low to medium winds, and maintaining rated output in above rated winds while keeping torsional torque fluctuations to a minimum. Control is exercised via individual blade pitch control as well as a self-tuning regulator (STR) for generator torque control. The fundamental philosophy behind the proposed control strategy for the wind turbine coupled to an asynchronous doubly-fed induction generator (DFIG) is general and can be easily extended to other WECS configurations.