Hybrid Transmission Expansion Planning for Renewable Power Systems Considering AC/DC Line Operation Characteristics

With advancements of power grid technologies and the growing demand for long-distance power transmission, large-scale regional power grids have evolved into hybrid alternating-current/direct-current (AC/DC) configurations, which are also expected to play a critical role in future renewable energy power systems. Effectively planning these hybrid AC/DC grids-especially through mathematical optimization models-requires detailed representations that capture the operational differences between AC and DC lines, thereby providing a more accurate reflection of real-world performance. To this end, this paper proposes a hybrid transmission expansion planning model that incorporates operational features such as short-term capacity increases for AC lines, the non-reversibility of DC line flows within a day, and the utilization rates of DC lines. A case study on a 27-bus system demonstrates the effectiveness of the proposed model.