Short-term optimal scheduling of cascade hydropower plants with reverse-regulating effects

The joint operation mode of large hydropower plants and their reverse-regulating plants has been widely used in China's major river basins. Hence this paper establishes an optimization model for the short-term optimal scheduling of cascade hydropower plants with reverse-regulating effects. Two conflicting objectives that need to be considered for optimal operation are minimizing the peak-valley difference of the power grid and minimizing the outflow variation of the reverse-regulating plant. The complex hydraulic coupling between the main-regulating plant and reverse-regulating plant is of particular concern. A novel two-layer nested approach, coupling constraint method and a mixed-integer linear programming (MILP) approach, is therefore proposed to solve the model. The results for three case studies demonstrate that: 1) The proposed approach is computationally efficient, and the average time for a single calculation is about 12 min; 2) The peak-valley difference of power grid G in dry season and flood season is reduced by 26.0% and 15.7%, respectively, after optimization. The outflow variation of the reverse-regulating plant has been controlled at 300 and 350 m³/s, respectively. 3) The developed model produces a more realistic and executable scheduling scheme than the benchmark model which does not consider the complex hydraulic coupling between cascade plants.