A synthesis of a blade pitch control for large wind turbines, taking into account the functional dependence of the torque generated in the blades from the azimuth angle

Julian Genov,B Gigov,M Todorov,N Nikolov,I Kralov,S Stoilova,V Stoilov

doi:10.1051/matecconf/201823404007

Abstract

In multi-MW (1MW and up) wind generation systems a variable speed - variable pitch (VS-VP) control technology is usually adopted to improve speed and torque characteristics and to obtain the optimal energy, which means to obtain the maximum power at low wind speed and the rated power at high wind speed. The power generated by an individual blade of the wind turbine changes considerably during rotation due for the change of wind speed in vertical direction, which decreases the angles of attack in the low blade positions and which leads to a reducing the generated energy. In the paper basing on BEM theory modification for none-homogenously fluid field and an optimization procedure is obtained an individual variable pitch control law as function of wind speed values and blades positions.

Highlights

IntroductionThe vertical speed gradient leads to significant changes of the torque generated from one blade during rotation
The vertical speed gradient leads to significant changes of the torque generated from one blade during rotation. This is due to the fact that in the lower blade positions the wind speed decreases considerable, this leads to reducing the angles of attack and as a result of this, the torque diminishes
Due to the continuity of the fluid flow, the induction coefficients are in dependence with aerodynamic state of all blades, which is a prerequisite for additional complexity in determination of the optimum angle of attack in the given position of the blade

Summary

Introduction

The vertical speed gradient leads to significant changes of the torque generated from one blade during rotation This is due to the fact that in the lower blade positions the wind speed decreases considerable, this leads to reducing the angles of attack and as a result of this, the torque diminishes. If an individual blade pitch control is applied, it is possible to increase power to a certain extent, especially for wind speeds below the nominal. The determination of this control is complicated because the blades are building from sections with different profile and respectively different lift and drag coefficients. The obtained results for a known prototype of wind turbine show simultaneously the validity of the BEM theory modification and of the propose approach for synthesis of an individual blade pitch control

Pitch control synthesis

Wind speed distribution

BEM theory adaptation with taking in account the vertical wind speed gradient

Obtaining of pitch control law

Conclusion