A Comparative Evaluation between Hybrid Modular Multi-Level Converters and Alternate Arm Converter

Abstract

There has been a notable increase in the demand for medium-voltage high-power converters for applications like electric vehicle charging stations (EVCS), energy storage integration (ESS) and power hungry data centers. Additionally, for EVCS and ESS applications, converters are preferred to be bidirectional to support the grid, while also being modular to assist with redundancy. Modular multilevel converters (MMCs), which have gained significant prominence in high-voltage applications, have also found their way into aforementioned medium-voltage applications due to their excellent modularity and power quality. However, the high costs and large footprint of MMCs present obstacles to the wider adoption. Recently several other families of converters have emerged as potential alternatives for both high and medium-voltage domains. Among these alternatives, two stand out as particularly promising options: alternate-arm-converters, and hybrid-MMCs. Each of these families has unique advantages, limitations, and optimal operation areas, making them suitable for different uses. However, to date, no comprehensive and quantitative research has been conducted to compare these topologies and highlight their optimal operation points. This lack of objective quantification and clear selection criteria has greatly hindered their industrial adoption. This research paper aims to address this gap by comparing the three major converter families in terms of devices utilized, submodule capacitance, semiconductor losses and other practical considerations. The paper concludes by presenting comprehensive selection guidelines that offer a clear delineation among converters and their application scopes.