Coordinated Inertia Support Strategy for Offshore Wind Power-Integrated MMC-HVDC System

To mitigate the inertia deficiency and weak damping in receiving-end grids caused by the large-scale integration of the offshore wind power-integrated MMC-HVDC system, this paper proposes a coordinated inertia support strategy. First, the transient support capability of submodule capacitors within the HVDC system is quantitatively analyzed. Subsequently, a capacitor energy-based grid-forming control is developed. A decoupled control mechanism is implemented to eliminate the coupling between submodule capacitor voltage and DC voltage, enabling maximum utilization of the converter’s internal transient energy while maintaining DC voltage stability. Furthermore, by introducing a frequency deadband mechanism, a coordinated inertia support strategy mediated by DC voltage is established. This facilitates a hierarchical support sequence wherein capacitors prioritize responses to minor disturbances, while the offshore wind farm (OWF) participates cooperatively during severe frequency deviations. PSCAD/EMTDC 4.6.2 simulations demonstrate that the proposed strategy achieves optimal capacitor energy utilization and effective multi-entity coordination. It reduces the maximum deviation in the grid by 33.3%, significantly enhancing system frequency stability.