A Two-Stage Multi-Scenario Optimization Method for Placement and Sizing of Soft Open Points in Distribution Networks

The Soft Open Point (SOP) is an emerging power electronic device for active power flow control, reactive power compensation and post-fault service restoration in power distribution networks. In this paper, a novel two-stage multi-scenario optimization method for SOP placement and sizing is proposed to minimize power losses and active power curtailment of distributed generation (DG) in distribution systems. In Stage 1, the Loss Sensitivity Index (LSI) and Voltage Deviation Index (VDI) are used to identify candidate locations of SOPs, and a new method to estimate the LSI is proposed. In Stage 2, a mathematical optimization model is developed using AC power flow to optimally size each voltage source converter (VSC) of a SOP; the power factor constraint at the substation/grid interconnection is incorporated in this model to ensure security of the upstream grid. The proposed method is validated by a modified IEEE 33-node test system and a large 404-node unbalanced distribution system operated by Saskatoon Light and Power in Saskatoon, Canada.