New phase‐changing soft open point and impacts on optimising unbalanced power distribution networks.

Three‐phase unbalanced conditions in distribution networks are conventionally caused by load imbalance, asymmetrical fault conditions of transformers and impedances of three phases. The uneven integration of single‐phase distributed generation (DG) worsens the imbalance situation. These unbalanced conditions result in financial losses, inefficient utilisation of assets and security risks to the network infrastructure. In this study, a phase‐changing soft open point (PC‐SOP) is proposed as a new way of connecting soft open points (SOPs) to balance the power flows among three phases by controlling active power and reactive power. Then an operational strategy based on PC‐SOPs is presented for three‐phase four‐wire unbalanced systems. By optimising the regulation of SOPs, optimal energy storage systems dispatch and DG curtailment, the proposed strategy can reduce power losses and three‐phase imbalance. Second‐order cone programming (SOCP) relaxation is utilised to convert the original non‐convex and non‐linear model into an SOCP model which can be solved efficiently by commercial solvers. Case studies are conducted on a modified IEEE 34‐node three‐phase four‐wire system and the IEEE 123‐node test feeder to verify the effectiveness, efficiency and scalability of the proposed PC‐SOP concept and its operational strategy. [ABSTRACT FROM AUTHOR]