Direct adaptive torque control for maximizing the power captured by wind turbine in partial loading condition

In this paper, a direct adaptive control approach is used to track the tip speed ratio (TSR) of wind turbine to maximize the power captured during the below rated wind speed operation. Assuming a known optimum value of TSR, the deviation of actual TSR from the optimum one is mathematically expressed as TSR tracking error. Since the actual TSR is not a measurable quantity, this expression for TSR tracking error is linearized and simplified to express it in terms of wind speed and rotor speed, where rotor speed can easily be measured. Although it is possible to measure the wind speed with high accuracy using LiDAR, using it raises the overall cost of wind turbine installation; hence, a method to estimate the wind speed is also proposed. The adaptive controller operates on this simplified TSR tracking error to drive it to zero and to keep the TSR constant at desired optimum value. The performance of the proposed control scheme is illustrated by implementing and simulating it in the National Renewable Energy Laboratory 5MW wind turbine model and comparing the results with the existing baseline fixed gain controller. Copyright © 2015 John Wiley & Sons, Ltd.