Comparative Evaluation of Silicon and Silicon-Carbide Device-Based MMC and NPC Converter for Medium-Voltage Applications

Abstract

The neutral-point-clamped (NPC) converter and the modular multilevel converter (MMC) are among the most popular converter topologies for medium- and high-voltage applications. This article investigates the impact of silicon-carbide (SiC) switches on the performance of MMC and NPC converters for medium-voltage (MV) applications. Furthermore, two different cases of the circulating current control schemes are considered for the MMC configuration. The experimental prototypes of three-level configurations for both of these topologies are developed to compare and analyze their performances. Furthermore, the double pulse test (DPT) setup is constructed to obtain the device loss characteristics of the switching devices. These characteristics are then used to compute the device losses using the derived loss models. Moreover, in order to generalize the results for wide power range of operation, two sets of devices are considered for the loss analysis of the considered converter configurations. The obtained results for conduction and switching losses are compared for both the converter configurations at various loading conditions. These results provide the operating range for the considered converters to achieve reduced converter losses. Finally, a comparative analysis for the selection of converter configuration based on the obtained results is presented.