The Synthetic Inertia Controller for MMC-HVDC Based Offshore Wind Farm Integration

The use of MMC converters virtually decouples offshore wind farms from the AC grid, which shall modify system inertia to affect its capability to through the disturbances of system frequency. In this paper, the existing inertia controller for MMC-HVDC Based offshore wind farm integration were classified into two categories and their working principles and control strategies are summarized. On this basis, a synthetic Inertia controller was proposed. It can be regarded as a combination of two mainstream strategies and has the advantages of both but avoids their respective shortcomings, which could provide the larger and longer synthetic inertia support. Finally, the dynamic performance of MMC-HVDC system has been successfully demonstrated by PSCAD/EMTDC simulations for the proposed synthetic inertia controller. The simulation figures demonstrate the proposed controller is capable of delivering the desired active power response to a rate of change of frequency (RoCoF) step change in the onshore network.