Structural Decoupling and Current-Angle Steering for Post-Fault Recovery of Current-Limited Grid-Forming Inverters

Jul 16, 2026

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Reliable fault recovery of grid-forming (GFM) inverters under current-limited conditions becomes critical as inverter-based resources replace synchronous generation. Conventional strategies mainly tune current-angle regulation and synchronization trajectories, yet the interaction between the current limiter and the voltage control structure is insufficiently understood. Under conventional PI-based voltage control, this interaction forms a moving recovery boundary that can cause trapping in current-limited control or oscillatory CLC–CVC transitions. A structurally decoupled virtual admittance voltage control with current-angle steering stabilizes that boundary and improves synchronization recovery, validated on a 3-kVA prototype for symmetrical and unsymmetrical voltage sags.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages10

Reading Time25 min

Introduction

Grid-forming inverters and synchronization stability challenges

Current-limiting control methods and their implications

Post-fault recovery issues under current limitation

Structural Decoupling and Current-Angle Steering for Post-Fault Recovery of Current-Limited Grid-Forming Inverters Neethu Sajeev, Graduate Student Member, IEEE, Stephen Arinze Obi, Graduate Student Member, IEEE, and Jae-Jung Jung, Senior Member, IEEE arXiv :2607 .09058v1 [ ee ss . SY] 10 Jul 2026 Abstract—Reliable fault recovery of grid-forming (GFM) converters under current-limited conditions is increasingly important as inverter based resources replace synchronous generation. Existing current-limiting strategies primarily focus on currentangle regulation and synchronization trajectory shaping, while the interaction between the current limiter and the voltage control structure remains insufficiently understood. Consequently, post-fault recovery may exhibit converter trapping in currentlimited control (CLC) or oscillatory transitions between CLC and constant voltage control (CVC). This paper shows that, under conventional PI-based voltage control, the interaction between the voltage controller and the current limiter creates a moving recovery boundary that contributes to these recovery failures. To address this issue, a post-fault recovery framework is proposed that combines structurally decoupled virtual admittance voltage control with current-angle steering. The proposed framework simultaneously improves synchronization trajectory evolution and stabilizes the recovery boundary during fault recovery. Experimental validation on a 3-kVA GFM inverter prototype confirms reliable postfault synchronization recovery under both symmetrical and unsymmetrical voltage sag conditions, with trapping and oscillatory CLC-CVC transitions eliminated. Index Terms—Grid-forming inverter, current limitation, fault recovery, synchronization stability, virtual admittance, currentangle steering. I. INTRODUCTION THE increasing penetration of inverter based resources (IBRs) is fundamentally reshaping modern power systems [1], [2] . As synchronous generators are progressively displaced, maintaining synchronization stability under reduced inertia and weak grid conditions has become increasingly challenging [3] . In addition, the limited fault current capability of power electronic converters introduces new challenges in protection and transient performance during grid disturbances [4] . In this context, grid-forming (GFM) converters have attracted significant attention due to their ability to establish voltage and frequency while actively participating in system dynamics [5], [6] . Unlike grid-following converters, GFM units operate as controlled voltage sources whose fault dynamics directly influence synchronization stability [7], [8] . Consequently, reliable operation of GFM converters under severe disturbances has become a critical requirement for future power systems. A major challenge in GFM converters is their limited over current capability during severe grid disturbances [9] . Since power electronic converters cannot sustain large fault currents for extended durations, current limiting control is required to ensure safe operation and fault ride through capability [10], [11] . Existing current limiting approaches are broadly categorized into virtual impedance methods and current reference saturation techniques [12], [13] . Virtual impedance methods regulate current indirectly through voltage modification but may suffer from transient overcurrent due to limited control bandwidth [14], [15] . In contrast, current reference saturation methods provide fast and direct current limiting but fundamentally modify the converter voltage source characteristics and synchronization dynamics [16] . Moreover, converter network interactions significantly influence stability during currentlimited operation [17], [18] . Therefore, current limitation should be regarded not only as a protection mechanism, but also as a dominant factor governing the large signal dynamics of GFM converters. With the inclusion of current limiting control, post-fa

FAQs

Why is post-fault recovery of current-limited grid-forming inverters important?

As inverter-based resources replace synchronous generators, maintaining synchronization stability under reduced inertia and weak-grid conditions is harder, and limited converter fault-current capability makes reliable recovery after grid faults a key requirement.

What failure modes can occur during post-fault recovery under current limitation?

The inverter may get trapped in current-limited control (CLC) or show oscillatory transitions between CLC and constant voltage control (CVC) after fault clearance.

How does the proposed framework improve post-fault recovery?

It uses structurally decoupled virtual admittance voltage control and current-angle steering to stabilize the moving recovery boundary, improving synchronization trajectory evolution and eliminating trapping and oscillatory transitions.

Jul 16, 2026

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