Energy Requirements of Modular Multilevel Converter Submodules and High-level Control Design for Synthetic Inertia Function

This work introduces a method to define the energy requirements for Modular Multilevel Converter (MMC) internal energy reserves for the sake of AC frequency support. The corresponding control is also proposed, which is compatible with the state-of-the-art MMC grid-forming control structure. Its effectiveness is shown by simulations.