A Compatible Current Limiter for Duffing-Hopf-Oscillator-Based Grid-Forming Inverters With Enhanced Transient Stability

Oscillator-based grid-forming (GFM) control offers better global synchronization in island mode but is still susceptible to loss of synchronization under severe grid faults due to additional current limitation schemes that constrain power transfer capability. In this paper, a compatible current limiter for Duffing-Hopf oscillator control is proposed, which limits fault current and maintains grid synchronization with the power grid under symmetrical and asymmetrical faults. The proposed current limiter is seamlessly integrated into the power reference loop of the Duffing-Hopf oscillator, preserving power synchronization control under normal and fault conditions while functioning as an automatic power reference regulator during severe faults. The analytical solution for the existence of stable equilibrium points of the Duffing-Hopf oscillator control with the proposed current limiter under grid sags is derived. It is demonstrated that the proposed current limiting strategy can ensure synchronization with the power grid under deeper voltage sags compared with traditional current limiting measures. Furthermore, the effects of current limiting amplitude, inertia coefficient, and short-circuit ratio on transient stability are thoroughly analyzed. The experimental results demonstrate that compared with traditional current limiting methods, the proposed current limiter for Duffing-Hopf oscillator control provides better transient stability.