Supercapacitor-Based Coordinated Grid-Forming Control Strategy for the HVDC System Integrating Offshore Wind Farms

Existing grid-forming high-voltage direct current (HVDC) system integrating offshore wind farms (OWFs) often provide very limited inertia support effect on the receiving-end grid due to the lack of stable energy sources. To address this issue, this paper proposes a scheme integrating a DC direct-mounted supercapacitor energy storage device (DCDM-SESD) into the HVDC system. A coordinated grid-forming control strategy is developed for the receiving-end modular multilevel converter (REMMC), which simultaneously achieves grid synchronization and active inertia support. Cooperative parameter design principles for the internal energy synchronization (ICES) loop and the supercapacitor energy control (SCEC) loop are established to ensure stable interaction between synchronization dynamics and energy regulation. Simulation results verify the effectiveness and superiority of the proposed control strategy in enhancing inertia support capability.