Enhanced Half-Bridge Sub-module Modular Multilevel Converter and its Capacitor Voltage Balancing Control

The Modular Multilevel Converter (MMC) is widely used in high-voltage applications due to its modularity, scalability, and superior power quality. This paper presents an Enhanced Half-Bridge Submodule (HBSM) MMC with a hybrid submodule structure, where 50% of HBSMs per arm operate at $V_{C}$ and the rest at $2 V_{C}$. This design reduces the number of submodules by 33.33%, leading to fewer switching devices, capacitors, and voltage sensors per arm. A capacitor voltage balancing algorithm is proposed to ensure stable operation. A comparative analysis with traditional HBSM and Full-Bridge Submodule (FBSM) MMCs is conducted. Simulation results in MATLAB/Simulink validate the proposed balancing strategy and demonstrate the Enhanced HBSM MMC’s performance under various conditions.