Three-phase flying-capacitor MMC with six coupled inductors

In this paper, the design and integration of coupled inductors have been proposed for a flying-capacitor (FC) modular multilevel converter (MMC) for induction motor drive applications. In the conventional three-phase FC-MMC, twelve discrete inductors are needed for three legs. However, by integrating one coupled inductor with two windings in two half-arms, the number of inductors required is reduced from 12 to 6. Accordingly, the overall volumes and weights of cores and windings can be reduced by 41.7% and 41.4% when compared with discrete inductors. To confirm the validity of the proposed coupled inductor, a 4160-V/1-MW simulation model of a FC-MMC and a 220-V/3-kW scaled-down prototype have been built, of which performance for induction motor drives has been tested from standstill to the rated speed.