Impedance Modeling and Analysis of Grid-Forming DFIG-Based Wind Turbine Systems

At present, renewable power generation is gradually transitioning from auxiliary power to main power, which is required to have the capability to support grid voltage and frequency. Therefore, the grid-forming control has emerged accordingly. However, the small-signal stability characteristics of different grid-forming doubly-fed induction generator (DFIG)based wind turbine generators (WTGs) are not fully clear, and there is a lack of basis for the selection of grid-forming control strategies. To this end, the accurate impedance models of four types of grid-forming DFIG-based WTGs are established and validated by frequency-scanning. Then, the impacts of different grid-forming control strategies and key control parameters on the impedance characteristics of DFIG-based WTGs are analyzed and compared. The results can provide a valuable reference for the selection and application of grid-forming control strategies tailored for DFIG-based WTGs.