Analysis of the N -Cell Single Phase MMC Natural Balancing Mechanism

This paper pertains to the analysis of natural balancing properties of an N-cell modular multilevel converter under phase-shifted pulse width modulation control schemes. The key enabling feature for the natural balancing analysis is a set of linear transformations of the input space and state space of the overall system. In the transformed space, we use frequency domain methods to describe the self-balancing properties of the converter. The crux of our proposal is showing that all the cell capacitor voltages converge exponentially fast to a common level; hence achieving natural balancing. The accuracy of the transformed model is verified through comparison with a detailed time-domain simulation of the original system.