Validation of Individual Pitch Control by Field Tests on Two- and Three-Bladed Wind Turbines

Abstract

Further improvements in the cost-effectiveness of wind turbines drive designers toward larger, lighter, and more flexible structures, in which more intelligent control systems play an important part in actively reducing the applied structural loads. These improvements also help to eliminate the need for wind turbines to simply withstand the full force of the applied loads through the use of stronger, heavier, and therefore more expensive structures. One way to reduce the loads is to use individual pitch control (IPC), whereby each blade receives a different pitch command to compensate for asymmetrical loads caused by nonuniform flow across the rotor. Originating in helicopters, the use of IPC for wind turbines was suggested for many years. Although many simulation studies have shown that significant load reductions are possible, confirmation of this using field tests on a real turbine in natural turbulence is important to give wind turbine designers the confidence to design to the reduced loads that IPC can deliver. This paper presents the results of field tests on two different 600-kW wind turbines, one two-bladed and one three-bladed. The results demonstrate convincingly that the predicted load reductions can be achieved in practice.