Analysis of Optimal Proportion Configuration of Grid Forming Direct Drive Wind Turbine

The traditional wind turbines (WTs) adopt grid following control (GFL), which suffers from instability issues under weak grid conditions and cannot support the new power system, while grid forming control (GFM) based wind farms can stably integrate with weak grids. Regarding future wind farm utilization prospects, the mixed operation of GFL and GFM WTs is a promising method with economic and technical advantages. However, there is research on determining the proportion configuration of GFM WT in wind farms. In this paper, a wind farm integration system is modeled in detail. Then, the equivalent short-circuit ratio (ESCR) is defined to evaluate the strength of the integrated AC grid. On this basis, the critical ESCR (CESCR) that maintains the system critically stable under different proportions of GFM WT is explored. In addition, three important factors affecting the proportion of GFM WT, such as the Q-V droop control, the impedance angle of the grid, and the location distribution of GFM WT, are analyzed. Finally, the simulations in the electromagnetic transient and small-signal models are carried out to verify the above analysis.