Maximum power estimation and droop control of DFIG-based wind turbines in multi-mode microgrids

This paper proposes a new control scheme for doubly-fed induction generators based wind turbines (DFIG-WT) in microgrids that operate in multiple modes. The DFIG-WT is controlled as a droop voltage source by the rotor side converter, using the indirect stator flux oriented vector (ISFO) control technique. The proposed control scheme enables the DFIG-WT to track the secondary control command given by microgrid central controller (MGCC) via maximum mechanical power estimation and wind power tracking strategy, thus the DFIG-WT is able to participate in system regulation. The maximum mechanical power of the DFIG-WT is estimated by a cascade observer. Consequently, when the microgrid is in grid-tie mode, the DFIG-WT can participate in the control of tie-line power. When the microgrid is in island mode, the DFIG-WT can participate in the restoration of system frequency and voltage. Numerical simulations verify the effectiveness of the proposed control strategy.