1.Anhui Province Key Laboratory of Renewable Energy Utilization and Energy Saving (Hefei University of Technology), Hefei 230009, China;2.State Grid Anhui Electric Power Research Institute, Hefei 230601, China

With the continuous increase in the penetration rate of distributed generators (DGs), the uncertainty of the distribution network is increasing, and there is an urgent need to introduce flexible resources for regulation. The joint introduction of energy storage systems (ESSs) and soft open points (SOPs) can not only provide power flow distribution capabilities on the spatial scale, but also further solve the imbalance between energy supply and demand on the time scale. To this end, considering the flexible characteristics of ESS and SOP comprehensively, the flexibility evaluation indices are established from two aspects of flexibility supply-demand matching and transmission channels. A tri-level coordinated planning model of SOP and ESS for the flexibility enhancement of new distribution system is proposed. Among them, the upper-level conducts ESS planning with the objective of minimizing the equivalent annual value of investment cost for ESS, the middle-level conducts SOP planning with the objective of minimizing the comprehensive annual operation cost of the distribution network, and the lower-level conducts operation optimization with the objective of maximizing the daily average flexibility ability. A bi-directional optimization method is used to generate typical operation scenarios to solve the uncertainty of DGs, and a hybrid optimization algorithm is used to solve the tri-level model. The rationality and effectiveness of the coordinated planning model of the SOP and ESS are verified through case analysis.