Individual Pitch Control Based on Local and Upstream Inflow Measurements

Abstract

As wind turbine sizes are increasing, the issue of load alleviation is becoming increasingly important to accommodate design requirements. Load alleviation can be achieved using either local flow devices, such as trailing edge flaps or using individual pitch, the latter being the topic of the present study. In this study, a controller based entirely on inflow measurements is designed. The performance of the controller is tested through simulations in standard operating conditions using two different measurement types; local measurements of angle of attack and relative velocity at a radial position on each blade, and upwind inflow measurements from a spinner mounted LIDAR. The controller is tested both with and without the ability to preview the incoming wind speed. Results show that using either of the tested control strategies the 1P peak in the load spectrum can be removed. It is shown that fatigue load reductions of around 30 percent can be achieved using the local inflow measurements and around 20 percent using the spinner LIDAR measurements.