Dual-Mode Grid Forming-Following Control Strategy for Multilevel Current Source Converters

This work presents an innovative control strategy for modular multilevel current source converters (MMCSCs) that enables simultaneous operation in both grid-forming mode (GFM) and grid-following mode (GFL). Using the modular architecture of the MMCSC, each submodule can be independently controlled, allowing some to operate in GFM, while others function in GFL. This simultaneous operation also supports dispatchability and real-time transitions between modes, such as in case of sudden islanding events. As a result, the MMCSC can operate in both grid-connected and stand-alone islanding conditions, with the GFM submodules forming the grid, while the GFL submodules maintain their functionality. The proposed strategy improves the flexibility of the power conversion system, especially for the integration and management of energy sources of different types.