Analytical determination of stable droop loop gain for a DFIG participating in frequency regulation

Abstract

One prominent concern over the high level wind power penetration is the consequent frequency stability issue in the power systems. To address this problem, additional droop loop control is widely adopted as an effective inertial control scheme to improve the system frequency nadir during a contingency event by temporarily releasing the stored rotational kinetic energy. The droop loop gain presents significant effect on both the performance of the frequency regulation and the operation stability of the doubly fed induction generator (DFIG). In order to ensure the stable operation of the DFIG during the frequency regulation process, this study proposes an analytical determination method of the stable droop loop gain based on system frequency analysis and bifurcation theory. The stability criterion of the rotor speed of the DFIG with droop loop control is theoretically formulated, taking into account extensive factors such as wind speed, active power deficit, and configuration parameters of the power system and DFIG. The critical droop loop gain can be calculated from the critical stability criterion equation. Simulations are carried out to validate the benefits and accuracy of the proposed determination method of stable droop loop gain.