To address sub-synchronous oscillation (SSO) issues caused by grid-connected direct-drive permanent magnet synchronous generators (D-PMSGs), this study proposes a suppression strategy that replaces the current inner loop of the grid-side converter with an improved linear active disturbance rejection control (LADRC). First, a mathematical model of the D-PMSG is established, and the principles and limitations of LADRC in SSO suppression are analyzed. Building on this, a phase-lead compensation link is introduced into the linear extended state observer (LESO) to enhance its disturbance observation capability. Simultaneously, fuzzy control is integrated with the linear state error feedback (LSEF) to improve the controller adaptability. The performance of the improved LADRC is then analyzed, demonstrating its enhanced disturbance suppression capability in the mid-low frequency bands. Finally, simulations and hardware-in-the-loop (HIL) simulation verify that the improved LADRC outperforms traditional LADRC in robustness and steady-state performance. The total harmonic distortion (THD) of the grid-connected current is reduced from 2.83% to 1.34%, and SSO is effectively suppressed.
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