Dual-Port Grid-Forming Control of MMC with Embedded Energy Storage

The grid-forming (GFM) inverters control has attracted extensive attention because of its ability to form both grid frequency and voltage, improve the power supply quality of renewable energy generation, and enhance the system stability under weak grid condition. However, the use of GFM control in modular multilevel converters (MMCs) for HVDC applications is still under research, especially when the embedded energy storage exists. To fill this gap, this paper proposes a dual-port grid forming inverters control method, so that the MMC can stably form the ac-side frequency and dc-side voltage even with the unbalanced energy storages embedded in sub-modules. The simulation waveforms are given to verify the error-free features and unbalanced operation of the proposed method.