This paper builds the small-signal model and analyzes the dc impedance of machine-side converter (MSC) for grid-forming permanent synchronous generator (GFM-PMSG) wind turbines. It is revealed that MSC has little impact on the ac impedance model of GFM-PMSG wind turbines. This finding implies that the grid-side converter dynamics, which is equipped with the GFM control, plays a critical role in the dynamic interactions between GFM-PMSG wind turbines and the power grid. The nonlinear time-domain simulations are carried out to corroborate the theoretical analysis. Finally, experimental tests are carried out to corroborate the theoretical findings.
