A hierarchical model in short-term hydro scheduling with unit commitment and head-dependency

The short-term hydro scheduling (STHS) problem has long been studied for decades, with great efforts having been made on improving their solution methods or algorithms. This work instead aims to solve a real-world problem with a hierarchical modeling strategy presented to decouple the STHS problem into two sub-problems: a load distribution (LD) and a unit commitment (UC), which are both solved with the Mixed Integer Linear Programming (MILP) and then coordinated through their coupling variables. The linearity errors in the model can be eliminated with an efficient successive water head updating pro-cedure that adjusts the searching range based on the improvement of the objective. Taking into account the hydraulic connection, unit operating zones, head-dependency, generation and water level targets, the optimal quarter-hourly schedule for Lancang Cascade that consists of 11 hydropower reservoirs and 56 units can be obtained in 1 min for not only all the hydro-plants in the cascade but also every unit within hydro plant. The application results demonstrate that the convergence of the water head updating procedure is intermittent yet guaranteed after about 20 iterations.(c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

In this study, a hierarchical modeling strategy is used to solve the short-term hydro scheduling problem by decoupling it into load distribution and unit commitment sub-problems. Mixed Integer Linear Programming is employed to solve both sub-problems, and the coordination is achieved through coupling variables. The linearity errors in the model are eliminated with a successive water head updating procedure. The optimal quarter-hourly schedule for the Lancang Cascade is obtained in a short time, considering hydraulic connection, unit operating zones, head-dependency, generation, and water level targets.