AC/DC Dynamic Interactions of MMC-HVDC in Grid-Forming for Wind-Farm Integration in AC Systems

This paper studies the dynamic interactions between the AC grids and the DC system. In this work, we focus on MMC-HVDC links interconnecting offshore wind farms and AC systems. The onshore converter is controlled in DC-voltage control mode on the DC side and in grid-forming on the AC side. The authors show the importance of DC-voltage loop design when controlling the MMC in grid-forming mode and its consequences on the MMC internal energy. In the conclusion, some recommendations are made regarding different potential solutions for supporting the DC voltage.