Analysis of the 5-cell single phase MMC natural balancing mechanism

This paper pertains to the analysis of natural balancing properties of a 5-Cell Modular Multi-Level Converter (5C-MMC) under Phase Shifted Pulse Width Modulation (PS-PWM) 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 utilize 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.