Finite-set Model-Based Predictive Control of a Novel Alternate Arm Modular Multilevel Converter

Modular multi-level converter has brought numerous advantages to HVDC transmission. This paper proposes a new alternative arm modular multi-level converter(FA-MMC) with full-bridge director switches and cascaded H-bridge cells. The proposed topology offers the current-limiting capability during DC side faults as other multilevel voltage source converters based on cascaded H-bridge cells. Additionally, it offers features such as less number of cells and smaller footprint than other existing modular multilevel converter topologies. The structure and operating principle are analyzed. There are several technical challenges of this proposed topology, such as the voltage balancing of floating capacitor in cascaded basic cells and the director switch control scheme. A suitable finite-set predictive control (FS-MBPC) strategy for this new topology is presented to minimize the output AC current error and balance the capacitor voltage while the director switches are operated in low frequency and soft-switching mode. Simulation and experimental results are provided to demonstrate the validity of the proposed topology and control method.