Decision support models for short term hydro-thermal resource scheduling of a price-taking power producer

In this paper we develop a decision support procedure for the short-term hydro-thermal resource scheduling problem of a power producer who operates in the liberalized electric energy market and aims at maximizing his own profit. The resources owned by the producer are hydroelectric plants and/or thermoelectric plants. It is assumed that weekly discharge of seasonal basins and maintenance plans of hydro and thermal plants have been determined so as to maximize medium-term (one year) profit. In the short-term horizon (one week or ten days), the power producer has to solve the unit commitment problem for the thermal units and the dispatchment problem for the available hydro plants and the committed thermal units, aiming at maximizing short-term profit. His decisions must be compatible with both technical constraints, i.e. inherent the production technologies, and market constraints. The procedure proposed in this paper is based on a mixed integer linear programming model, where the objective function represents the total profit and the constraints describe the hydro system, the thermal system and the market. The thermal system is modelled in great detail as it allows start-up and shut-down manouvres in every hour of the planning horizon, taking into account minimum up-time and downtime constraints as well as ramp-up and ramp-down constraints. The power producer is assumed to be unable to influence the market price, therefore energy prices are parameters exogenous to the decision model and the optimal schedule is determined on the basis of price forecasts.