Browsing by Author "Ordonez, Fernando"

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    Identifying Optimal Portfolios of Resilient Network Investments Against Natural Hazards, With Applications to Earthquakes
    (IEEE, 2020) Lagos, Tomás; Moreno, Rodrigo; Navarro Espinosa, Alejandro Andrés; Panteli, Mathaios; Sacaan, Rafael; Ordonez, Fernando; Rudnick van de Wyngard, Hugh; Mancarella, Pierluigi
    Although extreme natural disasters have occurred all over the world throughout history, power systems planners do not usually recognize them within network investment methodologies. Moreover, planners had historically focused on reliability approaches based on average (rather than risk) performance indicators, undermining the effects of high impact and low probability events on investment decisions. To move towards a resilience centred approach, we propose a practical framework that can be used to identify network investments that offer the highest level of hedge against risks caused by natural hazards. In a first level, our framework proposes network enhancements and, in a second level, uses a simulation to evaluate the resilience level improvements associated with the network investment propositions. The simulator includes 4 phases: threat characterization, vulnerability of systems components, system response, and system restoration, which are simulated in a sequential Monte Carlo fashion. We use this modeling framework to find optimal portfolio solutions for resilient network enhancements. Through several case studies with applications to earthquakes, we distinguish the fundamental differences between reliability- and resilience-driven enhancements, and demonstrate the advantages of combining transmission investments with installation of backup distributed generation.
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    Product line optimization with multiples sites
    (2022) Davila, Sebastian; Labbe, Martine; Marianov, Vladimir; Ordonez, Fernando; Semet, Frederic
    We consider the problem faced by a retail chain that must select what mutual-substitute items to display each one of its stores to maximize revenues. The number of items cannot exceed the limit space capacity of each store. Customers purchase the one product that maximizes their utility, which depends on the product price, travel cost to the store, and reservation price, known to the retailer. The retailer can set different price markdowns at different stores and products. The retailer considers the decisions of customers, and solves mixed-integer bilevel optimization problem, which can be formulated as a single-level optimization problem by using optimality conditions for the lower level. We propose Branch and Cut and Cut and Branch methods and include a family of valid inequalities to solve the problem. We compare the results with those of a Benders decomposition method. Our computational results show that the proposed Cut and Branch method obtains the best performance and improves the current state of the art.