*3.1. Topology Selection Consideration*

Based on the specifications, several converter topologies, including multilevel converter topologies that are common in industrial drive applications, were selected as the candidate topologies for both the rectifier and the inverter. They were the two-level voltage-source converter (2L-VSC), the two-level H-bridge voltage-source converter (2L-HB), the three-level neutral-point-clamped converter (3L-NPC), the three-level T-type converter (3L-T2C), and the five-level hybrid active neutral-point-clamped converter (5L-HANPC). Their schematics are given in Figure 1. Industrial drive systems based on these topologies are all mature, and products can be found such as Converteam VDM5000 (2L-VSC), Converteam MV7000 (3L-NPC), and ABB ACS 2000 (5L-HANPC) [20]. All these topologies have the same advantage, which is that only one DC source is required for a three-phase circuit. Therefore, a back-to-back configuration at the AFE stage could be built. On the contrary, widely used medium-voltage drive topologies such as cascaded H-bridge converters require multiple isolated DC sources that use zigzag transformers to create. This will significantly increase the system total weight. Another 3L solution is the three-level flying capacitor converter (3L-FC). However, compared to the 3L-NPC, it requires additional flying capacitors, which shows no benefit in terms of total weight. The reason why we considered the 5L-HANPC is that the 5L-HANPC is the only commercially available 5L converter with a single DC source. In addition, with the 5L operation, the filter size may be smaller, and the power loss may potentially be lower.

**Figure 1.** Demonstration of the candidate topologies: (**a**) two-level voltage-source converter (2L-VSC); (**b**) three-level T-type converter (3L-T2C); (**c**) three-level neutral-point clamped converter (3L-NPC); (**d**) two-level H-bridge voltage-source converter (2L-HB); and (**e**) five-level hybrid active neutral-point-clamped converter (5L-HANPC). **Green**: 1700 V IGBT; **blue**: 1200 V IGBT;**red**: 650 V IGBT.
