Tuning of Nacelle Feedback Gains for Floating Wind Turbine Controllers Using a Two-DOF Model

Abstract

Designing a collective blade pitch controller for floating offshore wind turbines (FOWTs) poses unique challenges due to the interaction of the controller with the dynamics of the platform. The controller must also handle the competing objectives of power production performance and fatigue load management. Existing solutions either detune the controller with the result of slowed response, make use of complicated tuning methods, or incorporate a nacelle velocity feedback gain. With the goal of developing a simple control tuning method for the general FOWT researcher that is easily extensible to a wide array of turbine and hull configurations, this last idea is built upon by proposing a simple tuning strategy for the feedback gain. This strategy uses a two degree-of-freedom (DoF) turbine model that considers tower-top fore-aft and rotor angular displacements. For evaluation, the nacelle velocity term is added to an existing gain scheduled proportional-integral controller as a proportional gain. The modified controller is then compared to baseline land-based and detuned controllers on an example system for several load cases. First-pass results are favorable, demonstrating how researchers can use the proposed tuning method to efficiently schedule gains for adequate controller performance as they investigate new FOWT configurations.

A control-oriented model for floating wind turbine stability and performance analysis

“…A 2008 patent [8] introduced an additional loop by adding the feedback of the nacelle velocity to the blade pitch. The capabilities of the method was further demonstrated by [2,9,10]. In contrast, a study by [11] took a different approach by feeding the nacelle velocity to the generator torque, which allows the blade pitch control bandwidth to increase further but at the expense of the generator torque.…”

Wind Turbine Tower Thickness and Blade Pitch Control Co-Design Optimization

“…Therefore, a first-order model like the one in Eq. ( 1) considering the rotational inertia of the turbine and both aerodynamic and electrical applied torques is sufficient [7].…”

Damping analysis of Floating Offshore Wind Turbine (FOWT): a new control strategy reducing the platform vibrations

“…Alternative methods use additional sensing, such as nacelle fore-aft acceleration measurements or platform gyroscopes, to improve the performance of the pitch controller. In (Lackner et al, 2009) and (Lenfest et al, 2020), the platform pitch velocity is used to adjust the rated speed set-point to reduce platform motions. However, the platform pitch damping analysis is not investigated and the link with the compensation parameter is not given.…”

“…The control strategy proposed in this work shares some similarities to the one introduced in (Lackner et al, 2009) and (Lenfest et al, 2020). As introduced in this paper, in fact, the rated generator speed is no longer a constant value but a function of the platform pitch velocity and the blade pitch is used to damp the floating platform pitch.…”

“…This choice, in fact, can be not optimal for some cases. Differently from (Lenfest et al, 2020), a mathematical frame is given to define the compensation to the platform pitch and the explicit analytical form of it is given. Moreover, a second compensation is considered in the control strategy proposed in this work.…”