Actuator Line Model simulations to study active power control at wind turbine level

Abstract

Wind energy is expanding rapidly worldwide, being horizontal axis wind turbines the technology of larger installed capacity. Modern multi-MW wind turbines have a torque controller and a collective pitch controller to control their power output, particularly when the wind speed is greater than the rated one, or when it is required to down-regulate the turbines production. In this work we show results of a validated numerical method [1], based on a Large Eddy Simulation-Actuator Line Model framework, applied to evaluate active power control on a real 7.7MW [2][3] onshore wind farm of Uruguay. We describe the implementation of these controllers in the caffa3d solver [4] and present the methodology we applied to obtain the controller parameters, such as the gain scheduling of the closed loop Proportional-Integral pitch controller. For validation, the simulation results are compared with 1Hz data obtained from the Supervisory Control and Data Acquisition System of the wind farm, focusing on the temporal evolution of the following variables: wind velocity, rotor angular speed, pitch, aerodynamic and electric torque and power. We analyze the Active Power Control response under different de-rate signals, both constant and time-varying, and subject to two wind profiles and two different wind directions, one of them with significant influence of wakes on one wind turbine. The dependence of the wake on the de-rate value is also evaluated, assessing the streamwise velocity component and the turbulence intensity in the wake.