Inclusion of combined cycle plants into optimal resource scheduling

Combined cycle plants are widely used in municipal power utilities all over the world. The most common installation of a combined cycle plant consists of several pairs of combustion turbine-heat recovery generators, and one set of steam turbine-electrical generator. The heat recovery steam generators provide steam for steam turbine and steam supply systems. In addition, an auxiliary boiler is usually added to provide steam for steam supply systems in cases where there is no need for electrical energy. Inclusion of combined cycle plants into the optimal resource scheduling causes difficulties. The main reason for this is that steam generators always have to be considered along with one or more pairs of combustion turbine-heat recovery generators. The developed algorithm is based on the assumption that thermal subsystem of a combined cycle plant is modeled through input-output curves that are defined for all configurations and all steam load ranges. The thermal unit commitment subproblem is divided into the commitment of classic thermal units and the commitment of combined cycle plants. The optimal commitment of combined cycle plants is obtained by applying a dynamic programming algorithm for defined combined cycle plant state space. A combined cycle plant's state space is obtained by aggregation of state space of all distinct configurations taking into account allowed transitions. The distinct configurations are defined as a set of distinct combinations or arrangements of combustion turbine-heat recovery generator pairs and a steam turbine-generator set.