Arm Inductor Selection Principle In Modular Multilevel Converter

Arm inductor and sub-module capacitor are two key components in the modular multilevel converter. Optimizing the selections of arm inductance and sub-module capacitance is thus critical for the converters design. Arm inductors in MMC are used to limit the circulating current which flows within the converter. The switching frequency harmonic is found to be the dominant component in the circulating current when an active circulating current suppressing controller is implemented. The analytical relationship between the arm inductance and switching frequency circulating current is derived, based on which the arm inductance requirement is obtained by limiting the circulating current to meet the defined specifications. A simulation has been carried out in the MATLAB, and the simulation results verify the theoretical analysis. A scaled-down MMC prototype has been built, and the experimental results validate part of the analysis.
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