Optimality in the Sense of Arm Current Distribution of MMC VSC-HVDC

This letter investigates the optimality of the modular multilevel converter (MMC) voltage source converters high-voltage direct current (VSC-HVDC), which constitutes a linear time-invariant (LTI) system for sufficiently large number of submodules per valve. The contribution of this letter is the mathematical proof that MMC VSC-HVDC is the optimal LTI topology in the sense of arm current distribution. Namely, the findings of this work show that MMC VSC-HVDC attains an optimal limit in the way the ac and dc components of the converter arm currents are distributed in the field of linear converter topologies, and may only be outperformed by nonlinear or time-varying VSC-HVDC topologies.