Optimal Operation in Active Distribution Networks Using Soft Open Point Integrated with Energy Storage

The integration of renewable energy sources has transformed traditional passive distribution networks into Active Distribution Networks (ADNs), characterized by dynamic, bidirectional power flows due to distributed energy resources (DERs). This paper proposes a Soft Open Point with integrated Energy Storage (SOP-ES) to address power flow and voltage challenges in ADNs. SOP-ES combines AC-DC-AC voltage converters with energy storage at the DC link, offering flexibility in space and time domains. An optimization model for ADNs with SOP-ES was formulated as a multi-objective nonlinear programming (NLP) problem. To improve computational efficiency, symmetrical semidefinite programming (SDP) relaxation was applied to transform the NLP into an SDP model. Case studies on the IEEE 13-node system demonstrated the model's effectiveness in reducing losses, mitigating voltage imbalance, and minimizing voltage violations.