A Comparison between LIDAR-based Feedforward and DAC for Control of Wind Turbines

The rotor-effective wind speed is the main disturbance for wind turbine collective pitch controller. On the one hand, Lidar-Systems provide good estimates of this wind speed and thus lidar-assisted feedforward control (LAC) is very promising to reduce structural loads. On the other hand, several pseudo-feedforward controller such as the Disturbance Accommodating Control (DAC) have been proposed, which are based on an estimate of the rotor-effective wind speed from turbine signals and thus avoid the additional cost of a lidar system. This study compares both concepts for overrated wind speed using low-order linear models to investigate the fundamental differences. Results show that DAC without considering pitch actuator dynamics can obtain comparable results with the LAC due to the measurement uncertainty of the lidar-measurement. When pitch actuator dynamics are included in the simulation, the LAC results are not impacted, since the wind speed estimation is provided with some preview. However, the results of DAC including pitch actuator dynamics are impacted significantly and cannot reach the benefit of LAC.