Pitch control scheme considering entire dynamics and full-load region in PMSG-based wind turbines

Large-scale wind turbines (WTs) are built with light-strength materials, which would otherwise cost more than the economic benefits of power generation. Hence, these turbines with huge rotors and slender towers are more exposed to external forces such as gust winds and the wake effect during their operational lifetime. This paper strives to establish a bridge between the design principles of the pitch control system (PCS) and the inherent dynamics of the drivetrain, blades, and tower in a grid-tied 5MW PMSG-based WT. Based on this purpose, the dynamic representation of the PCS is described in more detail, then the pitch controller is designed based on the complete dynamic model of the WT using a gain-scheduled PI controller to be capable of providing desirable dynamical performance throughout the pitch actuation region. The parameters of the proposed controller are calculated according to the current operating point of the WT with the aim of ensuring the acceptable stability margin and reducing the WT loading as much as possible. The controller design process is accomplished by analyzing the linearized dynamic model of the PCS under various scenarios using responses resulting from the frequency domain, polar coordinate, and modal analysis. Finally, nonlinear simulations illustrate that the intended pitch controller has a superior response over the traditional PI controllers.