Optimal Contracting of Transmission System Usage Combined With Subtransmission Planning via Cross-Entropy Method

Local power distribution companies (DISCOs) are not self-sufficient in electricity to serve their customers and require importing additional energy supply from the interconnected bulk power systems. In Brazil, they annually carry out the contracting process for the amount of transmission system usage (ATSU) for the next four years. This process is a real example of a task that involves decisions under uncertainty with a high impact on the productivity of DISCOs and the electricity sector in general. The task becomes even more complex in face of the increasing variability associated with the generation of renewable energy and the changing profile of the consumer. In this work, the main objective is to develop a methodology based on probabilistic power flow and cross-entropy techniques to assess the optimal contracting under uncertainty of the ATSU, combined with the expansion plan for the subtransmission network. As the robustness of the network influences the power import by the DISCO, there are real measurable benefits to assessing contracts and grid expansion altogether. Results with academic and real systems show that the proposals reduce the total costs with ATSU contracts.