System Inertia Support from a Wind Farm Using Rotor Kinetic Energy-Based Varying Droop Control

Available rotor kinetic energies from doubly-fed induction generators (DFIGs) in the upstream of a wind farm are different from DFIGs in the downstream due to the non-negligible wake effect. Thus, a variable gain of a droop control method is required for system inertia support because the constant-control gain method weakens the inertia support capability during disturbance. This paper presents an improved droop control method from a wind farm to efficiently utilize the rotating masses of DFIGs for system inertia support considering rotor kinetic energy-based variable-droop characteristics from temporal and spatial viewpoint. DFIGs in the upstream of a wind farm with large rotor speeds release more kinetic energy to the grid for system inertia support; DFIGs in the downstream with low rotor speeds release less kinetic energy to prevent rotor speed from stalling. Simulation results clearly indicate that the proposed method provides better performance in terms of improving the frequency nadir, nadir-based frequency response, and preventing DFIGs from stalling. Therefore, the proposed method improves the capability for wind power integration and facilitates to wind energy accommodation.