Small-Signal Impedance Modeling of DC Wind Turbines Under Grid-Forming and Grid-Following Control

Accurate impedance models of wind turbines are essential for stability analysis of offshore wind power systems. However, existing research primarily focuses on AC wind turbines, with relatively limited studies on DC wind turbines. Moreover, the work on DC wind turbines is primarily restricted to topology analysis or modeling under grid-following (GFL) control, neglecting the impedance characteristics under grid-forming (GFM) control. To bridge this research gap, small-signal impedance models of DC wind turbines under both GFM and GFL control are established and analyzed in this paper. Firstly, the mathematical model of the DC wind turbine is established using the switching cycle averaging method. Based on this, analytical impedance models under both GFM and GFL control are derived using the small-signal modeling method. Finally, the effectiveness of the developed models is validated through sine sweep measurements in MATLAB/Simulink.