DAC to mitigate the effect of periodic disturbances on drive train using collective pitch for variable speed wind turbine

DAC is a linear control technique used to mitigate the effect of disturbance on the plant. It is a superposition of full state feedback and disturbance feedback. This paper presents a control technique based on Disturbance Accommodation Control (DAC) to reduce fatigue on drive train generated by wind which is combination of step and periodic disturbances (generated by wind shear and tower shadow) of the turbine for above rated wind speed (Region III). We have presented a wind modeling for wind shear and tower shadow effect for the wind turbine control simulation and also developed a control scheme to mitigate the effect of 3p flicker on drive train. 5MW wind turbine of the National Renewable Laboratories (NREL) is used as research object and results are simulated in MATLAB/Simulink. We designed the controller based on linearized model of the wind turbine generated for above rated wind speed and then tested its performance on the nonlinear model of wind turbine. We have shown a comparison of the results for proportional-integral(PI) and proposed DAC controller tested on nonlinear model of wind turbine. Result shows that our proposed controller shows better mitigation of flicker generated due to 3p effect by using collective pitch control as compared to PI with tower and actuator dynamics.