Reducing power gradients in large-scale wind farms by optimal active power control

Recently, new requirements have been imposed by grid regulators on power gradients or ramping rates of wind farms. These requirements are an important concern for wind farm operators, as they introduce additional losses in farm efficiency. In the current study, we investigate the use of optimal coordinated control of rotating kinetic energy reserves to smooth power gradients in a wind farm, while maximizing power extraction. To that end, we use turbulent velocity fields obtained from large eddy simulations of a large wind farm, and set up an elementary case in which we consider the coordinated control of two turbines only. We find that optimal control of kinetic energy reserves allows to significantly reduce power variations, keeping them within requirements on power gradients. Moreover, in comparison to a per-turbine limitation of gradients with a greedy power control, we extract on average 3% more power.