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Adaptive Current Limiting and Common-Mode Voltage Injection for Maximizing Fault Current in Grid-Forming MMCs Under Asymmetrical Faults
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DOI：10.1109/jestpe.2026.3688512.png)
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Abstract
En 中文
Grid-forming (GFM) modular multilevel converters (MMCs) face challenges in maximizing fault current contribution under unbalanced grid faults due to internal DC circulating currents. This article proposes an adaptive current-limiting control based on virtual impedance (VI) to maximize the fault current while ensuring the MMC’s arm currents remain within limits. The method initially inserts a computed VI to limit the surge current, then dynamically adjusts this impedance so that the peak arm current exactly reaches its allowable limit, thereby fully utilizing the MMC’s current capability. Furthermore, a fundamental-frequency common-mode voltage (CMV) injection is introduced to actively drive the DC circulating current in opposition to the DC-link current component, which further boosts the achievable fault current. Simulation and experimental results demonstrate that the proposed strategy significantly increases fault current supply compared to conventional fixed-threshold limiting, without exceeding device current ratings. The results also show improved positive-sequence voltage support and reduced negative-sequence voltage at the point of common coupling, validating the effectiveness of the proposed control in enhancing fault-ride-through performance.
Keywords:
Asymmetrical grid faults
current limiting
grid-forming (GFM) control
modular multilevel converters (MMCs)
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I
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4.9
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249
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0
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