Analysis and Enhancement of Active Power Transfer Capability for DFIG-Based WTs in Very Weak Grid

Wind power generation yields significant economic and social benefits, especially for developing countries. However, large wind power plants (WPPs) are usually constructed in remote areas, leading to a weak grid. Also, serious challenges, such as power blocking, threaten the stable operation of the power system and result in a great deal of wind energy wasted. For this issue, this article presents a comprehensive study for doubly fed induction generators (DFIGs) to analyze and enhance its active power transfer capability in weak grid. First, a steady model for DFIGs is established, which emphasizes the influence of reactive power and power angle features. Based on it, the active power transfer capability under common reactive power control (RPC) modes is analyzed in detail. The analysis results indicate that both the rotor current limit and the power angle will affect the active power transfer capability, and the constant voltage RPC mode is preferred in the very weak grid. Furthermore, combined with the dq-axis current priority, a grid-side converter (GSC)-dominated RPC method is proposed to fully utilize the GSC capacity and substantially improve the active power transfer capability. Finally, the analysis and the proposed method are validated by experiments.