Operation Range Analysis and Capacitor Voltage Regulation of A Dual-AC-Terminal MMC based on Bifurcated-Arm Topology

In many applications, such as dual-motor driving and medium voltage distribution networks, converters with two sets of ac terminals are required. Traditionally, two separated modular multilevel converters (MMC) are connected back to back to meet the requirement, which is relatively expensive and bulky. In this paper, a dual-output MMC based on bifurcated- arm topology is introduced, which offers two sets of ac terminals and saves switching devices compared with the conventional configuration. The operation principle of the converter is introduced. And analysis of the whole operation range as well as the bifurcated-arm energy variation is presented in detail. Subsequently, an energy balancing control scheme is proposed and the modulation method is given. Finally, the feasibility of the theoretical analysis is verified by both simulation and experimental results.