Grid-forming Operation of Zhoushan Multi-terminal VSC-HVDC System

As China’s first five-terminal voltage source converter-base high voltage direct current (VSC-HVDC) transmission demonstration project, the Zhoushan VSC-HVDC system faces stability challenges in weak grid connection and efficient integration of island renewable energy. This paper proposes a multi-terminal cooperative grid-forming control strategy based on DC voltage dynamic response, with key breakthroughs in communication-independent frequency state perception and autonomous power regulation technologies. First, a self-synchronization method is proposed based on the emulation of the submodule capacitor energy to the synchronous generator. Then a dynamic coupling mechanism is established between the DC voltage of converter stations and the AC system frequency, achieving real-time mirroring of grid frequency. Furthermore, an active power cooperative regulation framework is constructed based on DC voltage dynamic trajectory tracking, realizing rapid response and rational allocation of multi-converter station power. Finally, a simulation model based on actual parameters of the Zhoushan VSC-HVDC project verifies the effectiveness of the control strategy. Results show that the proposed method significantly improves system dynamic response characteristics under grid frequency disturbance scenarios, demonstrating the active support capability of multi-terminal VSC-HVDC systems for power grids.