AC/DC hybrid electrical power distribution network planning approach with network topology-variables considering harmonic interaction influence in port

Renewable distribution generators (RDGs) and battery energy storage systems (BESSs) are promising solutions for AC/DC hybrid electrical power distribution network (EPDN) in the modern ports. The objective function of existing planning approaches focuses on the impact of primary harmonics generated by the remote RDGs. However, the harmonic interaction (HI) influence generated by the centrally arranged RDGs and BESSs of the port has not been evaluated. This study proposes a novel port AC/DC hybrid EPDN topology variables-based planning approach, including multiple RDGs and BESSs, to minimise the sum of the system investment cost (SIC) and financial losses associated with the HI influence coefficient (HIIC). The network topology variables were first defined as the AC/DC bus and its connected AC/DC transmission lines. Next, related to these variables, explicit formulas for the SIC and financial losses caused by the HIIC of harmonic currents were established. Moreover, the battery operating and the bus power balance constraints were determined. Additionally, by linearising the fractional items and employing a branch-and-cut algorithm, an optimal planning scheme was attained for the mixed integer nonlinear programming (MINLP) problem, which comprised the abovementioned explicit formulas and constraints. Finally, the port's EPDN planning scheme was simulated, which contained the six selectable AC/DC buses and ten AC/DC transmission lines. The simulation results demonstrated that the proposed approach could legitimately plan the EPDN topology of a port. Additionally, a scalability analysis was performed with planning for 14-bus and 21-bus nodes, demonstrating the ability of the model to handle larger EPDN. Besides, sensitivity analyses of various DC load ratios and RDG expansion plans were conducted. The simulation results revealed that when the ratio of the DC load exceeded 50 %, the financial losses caused by the HIIC of the harmonic current significantly affected the sum of the costs. Furthermore, an optimal RDG expansion plan with minimum SIC and financial losses was obtained. This study provides EPDN planners with a relative balance of variable port operating scenarios, HI influences, and risky investment costs.