A compensation scheme applied on wind turbine blade pitch control for the reduction of non-torque main shaft loads

Abstract

It has been well established that non-torque main shaft loads influence the internal drive train loads. This paper proposes a scheme that compensates for non-torque loads in the blade pitch controller. The compensation scheme is implemented on a dynamic model developed in FAST/Simulink. Three wind conditions of 8, 11.4 and 20 m/s are examined. The dynamic analysis of the bending moment in the low-speed shaft showed a reduction in bending moment by 3 % for the rated wind speed (11.4 m/s) and 1.8 % for the above-rated wind speed (20 m/s), highlighting the effectiveness of the proposed scheme. However, a reduction in bending moment also slightly decreased the shaft's speed by 2.3 % and 0.5 %, respectively. Similarly, the turbine power was decreased by 9 % and 1 %, respectively. In comparison, further gain scheduling within the compensation scheme reduces the power loss to as low as 0.3 %. The 2 to 3 % reduction in the low-speed shaft bending moment can significantly influence the drive train loads and easily outweigh any loss resulting in the shaft rotational speed and turbine power. Thus, this paper shows that using bending moment error as feedback within the compensation scheme positively affects the low-speed shaft's bending moment with the eventual potential of reducing drivetrain loads.