Topology Selection and Operation Strategy Design of the Soft Open Point in Looped Distribution Networks

The soft open point (SOP) plays a pivotal role in enhancing the flexibility of the distribution networks. However, there is a lack of clear criteria for selecting various SOPs tailored to specific application scenarios. This paper analyzes three common SOP schemes and conducts an economic evaluation based on the definition of the annualized comprehensive cost. Utilizing actual economic data, the annualized comprehensive cost of each scheme is calculated under different phase differences, serving as a crucial selection criterion in practical engineering. Considering the application scenario presented in this paper, the shunt-series type SOP, based on the multi-winding transformer and the compact unified power flow controller (UPFC), is chosen. The corresponding action logic for the transformer’s taps is designed by calculating the required series voltage. Additionally, control strategies for the shunt and series converters are devised to optimize stability, accuracy, and response speed. The proposed method is validated through simulation results using the established model in PLECS.