Frequency support strategy for supercapacitor-energy-storage-system-based MMC-HVDC system

The paper discusses a frequency support strategy based on MMC-HVDC system, considering the frequency variation and rate of change in the receiving-end grid during load transients. This strategy integrates virtual inertia control and virtual droop control methods to autonomously switch frequency control modes. It is able to reduce control mode oscillations during frequency restoration and providing transient inertia support and short-term frequency support. A simulation model is built in PSCAD/EMTDC, and the frequency control strategy is analyzed based on simulation results. The results indicate that the proposed strategy can provide transient inertia support and short-term frequency support, while also optimizing the impact of load fluctuations on the AC bus voltage.