Abstract
An advanced pitch controller is proposed for the load mitigation of wind turbines. This study focuses on the nacelle acceleration feedback control and lidar-based feedforward control, and discusses how these controllers contribute to reduce the load on wind turbines. The nacelle acceleration feedback control increases the damping ratio of the first mode of wind turbines, but it also increases the fluctuation in the rotor speed and thrust force, which results in the optimum gain value. The lidar-based feedforward control reduces the fluctuation in the rotor speed and the thrust force by decreasing the fluctuating wind load on the rotor, which reduces the fluctuating load on the tower. The combination of the nacelle acceleration feedback control and the lidar-based feedforward control successfully reduces both the response of the tower first mode and the fluctuation in the rotor speed at the same time.
Highlights
Modern wind turbines with variable pitch and variable speed configuration need control systems of blade pitch angle and generator torques [1]
It is noted that for any wind speed above rated, the combined lidar-based feedforward control and nacelle acceleration feedback control reduces the fluctuation in the rotor speed and loads at the tower tower base
These results show the effectiveness of the gain values of the nacelle acceleration feedback and lidar-based feedforward controller, they are based on the linearized system around the design point
Summary
Modern wind turbines with variable pitch and variable speed configuration need control systems of blade pitch angle and generator torques [1]. As mentioned by Jonkman [17], this strategy can increase the tower first modal damping ratio, but due to the pitch-to-feather nature of wind turbines, this control causes an increase in the exacerbated excursions in generator speed and electrical output This method can theoretically give any desired damping, but the limitation of the added damping by using this method has not been investigated. Feedforward gain was obtained by linearizing the wind turbine system They successfully reduced the rotor speed fluctuation as well as the fluctuating fore–aft tower base moment. The literature lacks discussions regarding the load characteristic of the wind turbine when both the nacelle acceleration feedback control and the lidar-based feedforward control of the blade pitch angle are used simultaneously. The load characteristics of the wind turbine for the case with both the nacelle acceleration feedback control and the lidar-based feedforward control are discussed
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