Control Techniques for MMCs in Unbalanced Grids with Various Transformer Configurations

Abstract

The growing application of power electronics devices for integrating renewable energy sources in power systems has become an area of research due to the varied nature of power systems and renewable energies. Imbalances in power systems, resulting from over-voltage and faults, drive the need for performance and stability analysis of modular multilevel converters (MMCs). Depending on the transformer configuration of the MMC, the magnitude of the circulating ground current varies. Therefore, a modification of traditional vector control or an advanced controller is required. This paper implements a sequence controller with a zero sequence controller to suppress the power oscillation and current harmonics depending on transformer configurations. In addition to this, an individual phase controller is also implemented to eliminate the power flow in the faulty lines. Finally, the performance of all presented controllers is compared, and an appropriate controller is suggested according to transformer configuration. © 2024 IEEE.