Comparison of Equivalent Circuit Models of Circular Current Limiter According to Anti-Windup Methods in Grid-Forming Converter

This paper compares equivalent circuit models of circular current limiter under different anti-windup strategies in a grid-forming voltage source converter (GFM-VSC). Conventional current limiting methods employing freezing-type anti-windup yield a purely resistive equivalent impedance, which limits the improvement of transient stability. To address this limitation, this paper proposes the use of a back-calculation antiwindup method, which enables shaping the equivalent virtual impedance with a desired X/R ratio. Through analytical derivation, it is shown that adjusting the back-calculation gain allows flexible control of the phase angle of the virtual impedance, thereby significantly enhancing the transient stability of the GFMVSC. The effectiveness and superiority of the proposed method over conventional approaches are validated through simulation results.