Opportunities for Leveraging Low-Voltage GaN Devices in Modular Multi-level Converters for Electric-Vehicle Charging Applications

摘要

Modular multi-level converters (MMCs), already well-established in high-voltage, high-power AC-DC conversion, can potentially bring advantages in lower-power applications, such as on-board chargers in electric vehicles (EVs). The availability of mature, high-quality GaN devices with low voltage ratings have made it worthwhile to consider the MMCs for these applications, due to its limited voltage gradients and higher AC-side power quality. To investigate these possibilities, a simulated 6-level MMC is compared against an experimentally-validated two-level EV charger. Both converters are designed for a maximum power level of 6.6 kW and compatible with 240 V and 400 V AC-side and DC-link voltages, respectively. The study reveals that the MMC offers great promise in terms of power-quality improvement and AC-side filtering requirements, and the need for large sub-module capacitances to maintain the module voltages is counterbalanced by the reduced requirements for EMI filtering and DC-link decoupling.