Research on an Improved Droop Control Strategy for Soft Open Point

Soft Open Point (SOP) is a new flexible primary equipment which can replace the normal tie switches in distribution network (DN). With the ability of controlling active and reactive power, SOP has already become a hot topic in the DN research field. This paper proposed an improved droop control strategy for multi-terminal SOP based on modular multilevel converter (MMC) topology. The control strategy can adjust droop coefficient in real time according to the value of active power variation and the rated active power. With the range of active power fluctuation expands, the capacity of enhancing the rigidity of DC voltage and maintaining the stability of DC voltage are getting better. Finally, a three-terminal SOP system is validated based on PSCAD/EMTDC simulation software and the results prove the validity and correctness of the control strategy.