Variable splitting applied to modelling of start-up costs in short term hydro generation scheduling

In this paper, a mixed-integer hydroelectric power model for short-term power system planning is discussed. The purpose of the model is to represent the generation characteristics of the hydropower plants accurately. In the modelling part, the paper focuses on two requests stated from power producers in an earlier study. First, it is desirable to operate on points with good efficiency. Second, start-ups and shut-downs of the units should not be carried out too often, since this is related to a cost. The problem is decomposed into a subproblem for each hydropower plant by relaxing the power balance equation and using variable splitting. The advantage of this relaxation is that network programming and dynamic programming methods can be used, which have proved to work well for power system planning issues. The relaxation used in this work has, as far as the authors know, not been applied in the field before. The master problem is solved by a subgradient technique. Finally, a numerical example from a part of the Swedish power system illustrates the technique.