Symmetrical Semidefinite Programming with Bifurcation Phase-Changing SOPs for Unbalanced Power Distribution Networks

The integration of unstable and/or uneven single-phase renewable distributed generation (DG) exacerbates the network imbalance problem. These unbalanced situations lead to financial losses, wasteful asset utilisation, and security haz-ards to network infrastructure. In this paper, a new phase-changing soft open point (PC-SOP) with bifurcation connection is proposed to allow various single-phase connections in three-wire systems. Then for three-phase unbalanced systems, operational strategies based on various cases are outlined. The optimal strategy for reducing power losses and three-phase imbalance can be identified by optimizing the regulation of SOPs and DG curtailment. The relaxation method of symmetrical semidefinite programming (SDP) is then used to adapt the initial non-convex nonlinear model into an SDP model that can be solved effectively by commercial solvers. Case studies are carried out on an IEEE 13-node three-phase system to validate the efficacy and efficiency of the presented SOP solutions and their operational strategy,