1. Specification of internal control system for nacelle yaw 1.1. Description of internal control system Only internal yaw control is currently available. See Wind turbine specification for a description of how to set up the model to use yaw control. The yaw error is found as the relative angle between the instantaneous wind at the hub and the orientation of the shaft. The controller starts aligning the rotor- nacelle assembly when a user defined threshold of the integral of the squared yaw error is reached. This gives more active response to fast changes in the yaw misalignment. The controller uses a constant, user defined yaw rate to get back to zero misalignment, or to a user defined yaw error. The input yaw error and the output yaw angle are low pass filtered with a fast and a slow corner frequency, respectively. The yaw controller logics follow the yaw rate controller described by Mulders and van Wingerden (2018). Yaw controller configuration input version number yawconfinput_ver yawconfinput_ver: integer > 0: Yaw controller configuration input version number. Current version is 1. Yaw controller time step DT_yawcontrol DT_yawcontrol: real > 0: Yaw controller sample interval \(\mathrm {[T]}\) Yaw set point YawErrSetPoint YawErrSetPoint: real [-180, 180]: Specified nacelle yaw misalignment \(\mathrm {[deg]}\) Yaw rate YawRate YawRate: real > 0: Rotational velocity for yaw engine \(\mathrm {[deg/T]}\) Yaw misalignment threshold YawErrThresh YawErrThresh: real > 0: Integral threshold for activation of yaw engine \(\mathrm {[deg^2T]}\) Fast filter corner period for low pass filtering T_LPfiltFast T_LPfiltFast: real > 0: Fast filter corner period for input signal \(\mathrm {[T]}\) Slow filter corner period for low pass filtering T_LPfiltSlow T_LPfiltSlow: real > 0: Slow filter corner period for output signal \(\mathrm {[T]}\) Figure 1. Definition of (positive) yaw misalignment between wind direction and shaft orientation Example input for internal yawcontrol system 'yawconfinput_ver 1 'DT_yawcontrol Yaw controller time step (s) 0.005 'YawErrSetPoint Yaw set point (deg) 0. 'YawRate Controller yaw rate, (deg) 0.5 'YawErrThresh Yaw misalignment threshold, (deg^2 s) 1.0 'T_LPfiltFast Fast filter corner period for low pass filtering (s) 1.0 'T_LPfiltSlow Slow filter corner period for low pass filtering (s) 60.0 Wind turbine external blade and power control input file References