Modular Multilevel Converter Control by Using Sorting Algorithm and Smoothing of ARM Inductor Current

The modular multilevel converter (MMC) is a revolutionary design that has shown potential for high-voltage applications. The MMC consists of many identical sub modules(SM's). Each SM may be regarded of as a controlled voltage source that must keep the capacitor's voltage at a specified level in order to work effectively. Furthermore, limiting the circulating current (which does not flow to the load) is critical to the MMC's consistent and effective functioning. This paper proposes a new sorting algorithm to balancing capacitor voltage, and eventually balance the load current with minimal total harmonic distortion (THD). It aims to equalize the capacitor voltages for each SM contained in the MMC one at a time using a new sorting approach. The analysis is based on a low-power case study of single-phase with eight SM's in one arm of MMC, but it may be expanded with a larger number of cells. The low power five-level MMC has been verified by mathematical and theoretical studies, in addition to data from simulations.