Quarter-Hourly Operation of Large-Scale Hydropower Reservoir Systems with Prioritized Constraints

Abstract

This paper deals with the optimization of short-term hydropower scheduling when a mathematically feasible solution cannot be achieved. Generally, the numerical search procedure terminates with the detection of infeasibility when an optimization problem is being solved. More often, however, operators of hydropower reservoirs prefer violating the mathematical constraints in order of priority, such that a satisfactory solution to the real-world problem can always be guaranteed. Previous studies rarely addressed this issue in relation to short-term operations of hydropower reservoirs. The present study relaxes the prioritized constraints with extra variables and solves the model by weighted goal programming. The weights are designed such that solving the problem is equivalent to a lexicographical optimization. The solution procedure is also efficient in dealing with large-scale problems using the following techniques: temporal and spatial decomposition of the hydro system, separate solution of plant-based operating zones, and linear programming with nonlinear local searching. The temporal decomposition has a significant advantage in computing time. An iterative procedure that converges fast is proposed to eliminate linearization errors. The model and procedure are applied to deal with the Yunnan provincial hydropower system, which consists of 44 reservoirs, believed to be one of the largest scale problems ever reported.