Coordinated Operation Strategy of Wind Farms for Frequency Control by Exploring Wake Interaction

This paper proposes a coordinated wind farm (WF) operation strategy that exploits the wake interaction within a WF. In contrast to the conventional WF operation strategy where each wind turbine (WT) is optimized individually, three operation strategies are suggested: 1) maximization of the WF's power while maintaining WF's rotational kinetic energy; 2) maximization of the WF's rotational kinetic energy while maintaining WF's output power; and 3) a de-loaded strategy whereby the WF's rotational kinetic energy is maximized for a fixed de-loading margin. The three operation strategies are formulated as nonlinear optimization problems and solved in a central WF controller. The optimal rotor speeds and pitch angles are used as reference values in the individual WTs. The optimization results for the three respective operation strategies show that: 1) up to 3% increase in the WF's output power; 2) up to 23% increase in the WF's rotational kinetic energy; and 3) up to 28% increase in the WF's rotational kinetic energy and 8% reserve power while operating the WF in a 5% de-loaded mode with respect to the conventional operation strategy. Time-domain simulations show that the proposed operation strategy noticeably improves the WF's performance in frequency control.