A hybrid arm‐multiplexing MMC for DC fault ride‐through without blocking

Abstract

AbstractConsidering both the DC fault ride‐through (FRT) and lightweight requirements of modular multilevel converter (MMC), this paper proposes a hybrid arm‐multiplexing modular multilevel converter (HAM‐MMC). The phase leg of the proposed MMC topology is divided into upper, middle, and lower arms, configured with full‐bridge submodules (FBSMs), half‐bridge submodules (HBSMs), and FBSMs, respectively. The time‐division multiplexing of middle arms between upper and lower arms is achieved by introducing arm selection switches, which considerably enhances the submodule utilization and thus minimizes the submodule number. The structure and zero voltage switching strategy of arm selection switches are presented, and a modified sorting algorithm is developed for capacitor voltage balance. The negative level output capability of FBSMs in upper and lower arms allows the DC voltage to be reduced in response to DC faults. Compared with the conventional hybrid MMC composed of HBSMs and FBSMs in a 1:1 ratio, the HAM‐MMC has the same power quality and DC FRT capability, but uses 25% fewer capacitors for lightweight. Simulation results demonstrate that the proposed HAM‐MMC can smoothly ride through DC voltage dip without interrupting power transmission, and can also rapidly resume normal operation after a zero‐voltage disturbance.