Closed-loop fast primary frequency-response of type-3 wind power plants in low inertia grids

Abstract

This paper proposes a frequency-control scheme for Doubly Fed Induction Generator (DFIG)-based (Type-3) wind turbines to improve the primary-frequency-control when the grid power balance is disturbed. The increasing penetration level of renewable energy sources, like wind power plants, reduces the total available inertia of modern grids, which deteriorate the frequency response in case of sudden power-mismatches. The proposed closed-loop participation of wind power plant interacts with the thermal units to reduce the frequency nadir and frequency settling-time, during the inertial and primary stages. The designed disturbance observer decreases the uncertainties in the estimation of grid parameters, which results in robust PI performance in adjusting the ancillary power provided by wind turbines. Certain measures considered within the control loop to limit the rate-of-change-of-frequency within the permissive range to avoid the protective relays tripping. Comparative simulations studies on modified IEEE 9-bus and 68-bus test systems verify the effectiveness and advantages of the proposed method.