Virtual Flux-Based Modulation Schemes for Adaptive Stress Reduction of Degraded Submodules in CHB-Based MMCs

Abstract:
This paper presents an adaptive control scheme for cascaded H-bridge modular multilevel converters that reduces the voltage stress on selected components estimated to have degraded health. The proposed method independently controls the average voltage of each SM according to its estimated state of health. It is shown that the combination of the proposed control system and the virtual flux-based modulation results in minor changes in the quality of the output current while the converter operates with unequal submodule voltages.