Guide curves in stochastic dynamic programming to optimize operation policies in sequential hydropower dams

Abstract

The guide curves are tools that specify rules for dam operation that allow reducing the chances of unwanted spill or deficit events. In this research, we analyzed the importance of using guide curves and penalizing the deviation of such curves by the occurrence of surplus volume, or deficit, using optimization tools on an objective function that apply stochastic dynamic programming (SDP), guide curves and reservoir operation simulation all together, to obtain and evaluate biweekly operation policies for hydropower generation purposes. The main dams of the Grijalva River were taken as a case study. The optimization tool is based on sequential decision stages (time intervals) to operate a dam system that considers the restrictions on storage volumes, defined by high and low guide curves. An objective function was considered which maximizes energy generation, it uses coefficients to penalize unwanted events of spills, deficits, and operation conditions outside the limits of the guide curves. In conjunction with the agencies that manage the system, three tests with different guide curves were defined. To analyze their sensitivity in the results (mainly events of spillage) one more test was defined for an operation rule without considering guide curves. The system behavior was simulated with the historical record, where five variables were analyzed: total spills and deficit, minimum and maximum storage, as well as the average energy generated. By using the guide curves, the occurrence of spills and deficits was avoided.