Decision support models for scheduling hydro and thermal power plants in the liberalized electric energy market

We consider the problem of an electric energy producer operating in the liberalized electric energy market, who has to schedule his own production plants aiming at maximizing profit. The power system owned by the producer is assumed to consist of hydro power plants and thermal power plants. Two decision support procedures are developed for the short-term scheduling problem of a price taker power producer and a price maker power producer respectively. The procedures are based on mixed integer linear programming models, where the constraints describe the hydro system, the thermal system and the market, while the objective function represents profit to be maximized. The thermal system is modelled in great detail as it allows start-up and shutdown manouvres in every hour of the planning period, taking into account minimum up-time and down-time constraints as well as ramping constraints. By these procedures the optimal unit commitment of thermal plants and the optimal dispatch of hydro and thermal plants are determined, given either a forecast of the energy price, in the price taker case, or an estimate of the competitors' supply curves, in the price maker case. Numerical results are reported and discussed.