Small-Signal Stability of Grid-Forming Control for Doubly-Fed Induction Generators: A Comparative Study of Different Control Algorithms

This paper presents a comprehensive small-signal stability analysis of three widely used grid-forming (GFM) control strategies, namely droop control, virtual synchronous generator (VSG), and generalized VSG (GVSG), implemented on a doubly-fed induction generator (DFIG) based wind turbine. Modal analysis is performed to uncover critical oscillatory dynamics, in terms of frequency and damping characteristics, under various realistic operating conditions, considering the impacts of grid strength, virtual impedance, inner-current control loops, output power levels, and off-grid operation. To validate and complement the modal analysis findings, time-domain simulations under small disturbances are performed. Based on the results from combined frequency and time-domain analysis, the study further compares the respective strengths and limitations of each control approach, providing valuable insights for the integration of renewable energy systems in future power grids.