Improved Modular Multilevel Converter with Output Voltage Boosting Capability for Medium Voltage DC Distribution System

Abstract

Numerous promising features of Medium Voltage DC Distribution System (MVDC-DS) make it highly probable that it would be extensively integrated with the future AC power grid to enhance power availability. However, issues may arise during interconnection such as voltage incompatibility between the two grids i.e. MVDC-DS and AC grid. Keeping this in mind, in this paper an Improved Modular Multilevel Converter topology (I-MMC) is considered and a novel voltage balancing algorithm (VBA) is proposed. I-MMC offers several unique features like wide range of voltage boosting capability, increased number of levels in the output voltage, low switch count and enhanced THD compared to the conventional MMC. Thus, the I-MMC ensures the interconnection of the AC and DC grids and also ensures low foot print size, high power density and low infrastructure cost. I-MMC is equally effective for applications like electrical machine drive systems, High Voltage DC (HVDC) systems, and other high voltage, high power applications. I-MMC and VBA are simulated in MATLAB/Simulink environment. Representative waveforms for a wide range of loading conditions are included to validate the theoretical claims.