Lidar-assisted wind turbine feedforward torque controller design below rated

Two below-rated feedforward torque control strategies are investigated for a megawatt-scale commercial turbine to regulate rotor speed and reduce turbine structural loads. The investigated regime for this research is the transition region when the turbine is operating just below rated wind speed. In this transition region, the rotor speed has reached its rated value but the generator torque has not. The first of the two controllers designed is a nonlinear feedforward controller that is based on aerodynamic torque balance computed from a light detection and ranging (lidar) measurement and a feedback power measurement from the turbine. A linear disturbance accommodating control (DAC) based torque controller has also been adapted and compared with the nonlinear control strategy. This DAC depends only on the lidar feedforward measurement without using feedback measurement from the turbine. The controllers are verified with a nonlinear FAST turbine model and turbulent wind fields.