Optimised de-rated wind turbine response and loading through extended controller gain scheduling

Wind turbines are expected to be able to participate in the ancillary services normally provided by the conventional power plants, as the penetration of the wind energy in the electricity grid is increasing. As a result, the turbines are needed to be able to control their active power. Constraining the possible output power, i.e. decreasing the power to less than the maximum or rated power, is therefore important for the wind turbine control system. When a turbine is operating under a de-rating strategy, the operating points of the turbine, i.e. the steady state blade pitch and the tip speed ratio, change compared to the normal case and this needs to be considered within the control design. This paper is to study the influence of de-rating on the turbine controller gain scheduling and its effect to power output and component fatigue damage. The results show that the WT response is refined through tuning under the different down-regulation operation points which results in less fatigue damage of the key turbine components.