Bi-level planning of rotary power flow controllers and energy storage systems for economy and carrying capacity improvement in the distribution network

In a traditional distribution network, the weak grid structure and high penetration of renewable energy sources restrict the carrying capacity. Flexible interconnection devices (FIDs) and energy storage systems (ESSs) offer a valuable solution to these challenges by coordinating and optimizing them regarding time and space. This paper proposes a coordinated bi-level planning method for the rotary power flow controller (RPFC) and ESS. The goal is to improve both economic efficiency and the comprehensive carrying capacity of the distribution network. First, the economic advantages of RPFC over traditional FIDs are analyzed. Then, mathematical models for the RPFC and ESS are developed. A bi-level planning framework is established. The upper level minimizes total costs by optimizing the siting and sizing of RPFC and ESS. The lower level is the coordinated operation optimization level, where a comprehensive carrying capacity index system for flexible interconnection is constructed, considering system stability, economy, and flexibility. A hybrid algorithm is introduced to solve the model efficiently. It combines the improved gravitation field algorithm (IGFA) with second-order cone programming (SOCP). The algorithm uses a tent chaos map for initialization and adopts an elite retention strategy to enhance convergence. The simulation is based on a three-feeder distribution network using MATLAB and the GUROBI solver. Compared to Scheme 1, the total cost is reduced by 22.6 %, and the carrying capacity index is improved by 22.3 %, demonstrating enhanced economic performance and carrying capacity through coordinated planning of RPFC and ESS.