Improving participation of doubly fed induction generator in frequency regulation in an isolated power system

An increasing penetration of renewable power resources (particularly wind farms) is observed in power systems during the last years. There is a frequency control concern with these kinds of power resources because they do not provide the so-called inertial response. Since the doubly fed induction generator (DFIG) equipped with Variable Speed Wind Turbine (VSWT) is the mostly used type of generator in wind farms, this paper proposes a new control approach allowing the DFIG to participate more efficiently in the power system frequency control. The approach consists of three steps: (1) Estimating the active power mismatch ΔP0 between the active electrical power and the mechanical power which appears at the first moment after the perturbance at the DFIG, (2) based on ΔP0 determine the electrical power reference Pref of the active power controller, and (3) appropriate removal of ΔP0 if the power frequency deviation is above a prescribed value and the automatic generation control (AGC) is activated. The obtained simulation results on a simple 2-bus system and on IEEE 14-bus test system show that the proposed approach has several advantages over existing approaches.