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2 Annals of Computer Science and Information Systems

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Efficient exact A* algorithm for the single plant Hydro Unit Commitment problem

Heintzmann Alexandre, Artigues Christian, Bendotti Pascale, Ngueveu Sandra Ulrich, Rottner Cécile

Annals of Computer Science and Information Systems

2023

Vol. 35

533--543

The Hydro Unit Commitment problem (HUC) specific to hydroelectric plants is part of the electricity production planning problem, called Unit Commitment Problem (UCP). More specifically, the studied case is that of the HUC with a single plant, denoted 1-HUC. The plant is located between two reservoirs. The horizon is discretized in time periods. The plant operates at a finite number of points defined as pairs of the generated power and the corresponding water flow. Several constraints are considered. Each reservoir has an initial volume, as well as window resource constraints, defined by a minimum and maximum volume per time period. At each time period, there is an additional positive, negative or zero intake of water in the reservoirs. The case of a price-taker revenue maximization problem is considered. An efficient exact A* variant, so called HA*, is proposed to solve the 1-HUC accounting for window constraints, with a reduced search space and a dedicated optimistic heuristic. This variant is compared to a classical Resource Constrained Shortest Path Problem (RCSPP) algorithm and a Mixed Integer Linear Programming formulation solved with CPLEX. Results show that the proposed algorithm outperforms both concurrent alternatives in terms of computational time in average on a set of realistic instances, meaning that HA* exhibits a more stable behavior with a larger number of instances solved.

Models and algorithms for natural disaster evacuation problems

Artigues Christian, Quiliot Alain, Toussaint Hélène, Hebrard Emmanuel

Annals of Computer Science and Information Systems

2019

Vol. 18

143--146

We deal here, in the context of a H2020 project, with the design of evacuation plans in face of natural disasters: wildfire, flooding… People and goods have to been transferred from endangered places to safe places. So we schedule evacuee moves along pre-computed paths while respecting arc capacities and deadlines. We model this scheduling problem as a kind of multi-mode Resource Constrained Project Scheduling problem (RCPSP) and handle it through network flow techniques.