The Overview of Frequency Regulation Coordinated Control for MMC-HVDC Connecting Wind Farms

Modular multilevel converter based high voltage direct current (MMC-HVDC) transmission is the mainstream technology for offshore wind farms with long distances of more than 80km integration. With the development of technology, the frequency stability problem due to the low inertia has become the focus of the current research. This paper systematically discusses the coordinated frequency regulation control strategy of MMC-HVDC with wind farms. The common symmetrical monopole/ bipolar MMC-HVDC system structures in engineering are first introduced. Next, The frequency regulation control for MMC-HVDC and wind farms (WFs) and the frequency sensing method used for coordination are summarized. Finally, this paper looks forward to the future research direction of MMC-HVDC connecting wind farms regarding frequency regulation capability assessment, and grid-forming fault ride-through control.