Isolated MMC-based ac/ac stage for ultrafast chargers
Ygor Pereira Marca, Maurice Roes, J.L. Duarte, Korneel Wijnands
Abstract
The application of indirect and direct modular multilevel converter-based topologies in an isolated ultrafast charger, operating from a three-phase medium-voltage grid, is compared. The most promising circuit is an isolated direct ac/ac modular multilevel converter, in which four-quadrant operation is possible by employing full-bridge sub-modules. The direct ac/ac conversion reduces the cost and volume of fast charging stations by eliminating line frequency transformers. An analytical model focusing on the decomposition of circuit states is employed to present the control scheme. Subsequently, the approach is validated with simulation results, corroborating the suitability for high-power bidirectional battery chargers.