Author(s): Ieda Geriberto Hidalgo; Paulo De Barros Correia; Francisco Jose Arnold; Joao Paulo Fernandes Estrocio; Jessica Pillontorralba Fernandes; Regiane Silva De Barros; William W-G Yeh
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Keywords: Hydroelectric plants; Unit commitment; Optimization methods; Evolutionary algorithms; Efficiency curves
Abstract: This paper presents a hybrid methodology for solving the unit commitment problem of hydroelectric plants. It takes into account the individual characteristics of the machines. The objectives are to minimize the daily turbine outflow of the plant and, at the same time, minimize the number of start-ups and shut-downs of the units. The model is formulated as a mixed integer, nonlinear programming optimization problem with multiple objectives. We propose a solution method that combines two types of algorithms: a heuristic global search (for integer variables) and a local optimizer (for continuous variables), in which the local optimizer is embedded in the global search. For the global search we use a multi-objective evolutionary algorithm. The local optimizer employs nonlinear programming. Two case studies are carried-out using data from a Brazilian hydroelectric plant that provides energy for Sao Paulo State. The results show that the proposed methodology brings two main benefits. The first is the efficiency gained, since it seeks to operate the generating units as close as possible to their most efficient operating points. The second is the reduction of the units’ maintenance costs, because it aims to minimize the number of starting up and shutting down of the machines.
Year: 2013