To address the growing demand for megawatt-scale and low-voltage power supplies in large-scale electrolytic hydrogen production

this paper proposes a scheme based on multilevel current source converter (MCSC). A current balancing strategy is developed to mitigate module current mismatch under parallel operation

combining modulation ratio regulation (MRR) via current feedback and global zero-vector substitution (GZVS). The topology and current characteristics under carrier phase-shifted modulation are analyzed

and the imbalance mechanism is identified. A steady-state control loop adjusts submodule modulation ratios to equalize power

while transient deviation is corrected by substituting zero vectors when necessary. This forms a unified current balancing scheme for all operating conditions. Simulation results show that the proposed method maintains balanced current sharing with minimal switching frequency. Experimental validation on a 6.65 MW/19 kA full-power prototype demonstrates effective current balancing and grid current THD below 3%. This study provides a promising MCSC-based solution for high-power hydrogen production with improved modular scalability and operational reliability.