Abstract
Current solutions to mitigate bird collisions in wind farms include temporarily shutting down wind turbines, informed by sensor systems or human observers. An alternative to stop the power production for avoiding bird-blade collisions is to design a closed-loop control system that dynamically adjusts the rotor speed without requiring shutdown. For that, sufficient time and torque are required for an action by the active control. This paper derives a relationship between the time available to avoid a potential bird-blade collision and the required perturbation in rotor torque, and speed, by the wind turbine. Thereafter, this analytical formulation of fundamental characteristics is extended by numerical analysis to indicate the feasible control actions, given the specific operating conditions of the wind turbine. Additionally, in view of accelerating the adoption of Bird Collision Avoidance (BCA) controllers by industry, a discussion on the potential interfaces between BCA control and wind turbine controllers with typical industry features is presented. Case studies with wind turbines of different sizes illustrate the requirements and feasible actions by an active bird collision avoidance mechanism based on closed-loop control.