Optimal Power Flow for Converter-Dominated AC/DC Hybrid Microgrids

This paper presents a new optimal power flow (OPF) formulation based on loadability maximization for islanded converter-dominated AC/DC hybrid microgrids. Hybridizing AC and DC at the distribution level brings the merits of AC and DC together as a valuable future layout for AC and DC technologies. Nevertheless, most recent AC/DC distributed resources and loads are converter-based resulting in low inertia. Further, the future distribution systems will allow investors and customers to plug their energy resources in and out. Such systems with a high penetration of converters and plug-and-play capability will have their own operational philosophy. During islanding in particular, loadability maximization is more pronounced due to the limited resources and being susceptible to any sudden and slow load/supply variations. Thus, the target of the system operator might be to increase the system steady-state stability margin by running OPF. In this work, the AC/DC OPF problem is formulated as a nonlinear constrained optimization problem, and solved by Interior Point method. The newly formulated OPF algorithm is tested on a modified 38-bus AC/DC hybrid microgrid. The developed AC/DC OPF can be a powerful tool for system planners and operators to explore the technical and economic challenges related to hybridizing the AC distribution systems.