With the continuous expansion of AC/DC hybrid distribution networks and the significant increase in nonlinear loads

conventional arc suppression devices exhibit limitations in single-phase ground fault scenarios involving harmonic distortion. To address this challenge

this paper proposes an active ground fault control strategy based on arm current regulation by modular multilevel converters (MMCs). Firstly

a controllable DC-side grounding branch topology is constructed to provide a zero-sequence current path during fault conditions

while establishing a closed-loop compensation model for fault-phase voltage that accounts for harmonic interference. Secondly

an arm current control method in the stationary frame is developed

enabling simultaneous regulation of fundamental/harmonic components

circulating components

and DC components within a unified control architecture without coordinate transformation. Furthermore

an instantaneous power transfer model of MMC during fault arc suppression is established

and a capacitor voltage balancing control method incorporating fault suppression dynamics is proposed. Quantitative design criteria for arm submodule configuration are derived. Finally

simulations based on the MATLAB/Simulink platform verify the effectiveness of the proposed ground fault current suppression control method under different fault resistances.