Field testing and practical aspects of load reducing pitch control systems for a 5 MW offshore wind turbine

This paper presents the results of a research project, covering the design, implementation and field testing of a load reducing pitch control system on a 5 MW offshore wind turbine prototype [1]. Two controller modules, aiming at fatigue load reduction for rotor blades and tower, have been implemented and tested: Yaw and Tilt moment Compensation using Individual Pitch Active Tower Damping Control Both controller modules have been shown to work reliable in the field. The outcome of the analysis of load changes, however, was not as clear as expected. It was found that considerable reinforcements to the pitch system would be required to allow continuous activation of the load reducing controller modules. Furthermore, for the specific wind turbine, it turned out that continuous operation of Individual Pitch Control will not provide many benefits in terms of material or cost savings. Instead, a selective activation in the case of certain extreme operating conditions will b e applied in the next generation of Areva Wind Turbines.