1. Internal nacelle yaw control 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 \(e_\psi \cdot |e_\psi|\) is reached, where \(e_\psi\) is the yaw error. 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). Figure 1. Definition of (positive) yaw misalignment between wind direction and shaft orientation 1.2. References Mulders, S. P., and J. W. van Wingerden (2018): Delft Research Controller: an open-source and community-driven wind turbine baseline controller. Journal of Physics, Conference Series. Vol. 1037. No. 3. 2. Model adaption Yaw control is added to a wind turbine through appending an extra line as an extension to the tower top. The yaw correction will be given as a prescribed rotation of the yaw line, relative to the tower top. The tower top (tower line end 2) and end 1 of the yaw line must be located in two different supernodes at the same location. Figure 2. Outline of yaw controller model External Bladed Style Controller HAWC2 Import