Capacitor Voltage Balancing of New Hybrid Modular Multilevel Converter Topology

This paper presents the new Hybrid Modular Multilevel Converter (H-MMC) topology, which is the combination of Half-bridge sub-module (HB-SM) and Asymmetrical mixed submodule (AM-SM). The comparative analysis of the presented H-MMC with conventional MMC and other hybrid MMCs is performed on the basis of device count and de fault-blocking capability. The selection criteria of the number of HB-SMs & AM-SMs and the corresponding maximum possible arm voltage level generation are formulated for n-level H-MMC. The generalized formulation for n-level H-MMC has been carried out considering the device count, modulation, and de fault-blocking capability. Single carrier PWM with some improvements is used here as a modulation technique. The preliminary control objective of MMC, which ensures its proper operation is balancing the SM capacitor voltages effectively. In this paper, the Voltage Balancing (VB) technique for this new hybrid topology is proposed. The effectiveness of the proposed VB technique is validated by providing the simulation results.