Real-Time Dispatch for Multi-Unit Hydroelectric Plants with AC Optimal Power Flow: The Case of the Santo Antonio System

Abstract

The growing demand for green energy has driven the development of large-capacity hydroelectric plants away from load centers. In this setting, one key aspect is constructing electrical networks for efficient power transmission to the primary grid, which is sometimes combined with high-voltage direct-current systems. However, on-site applications based on real-time dispatch problems often do not model AC power flow (ACPF) constraints, partly because of a lack of appealing methods to simultaneously include the dispatch and ACPF operating characteristics. Furthermore, a precise hydropower production function, a priority in this type of problem, can introduce additional complexity, and practical applications commonly sacrifice grid-connection modeling. This paper proposes a technique for incorporating ACPF constraints in real-time hydro dispatch, promoting widespread methods and optimization tools. The proposed strategy is based on mixed-integer quadratic programming that yields convergent electrical variables compatible with the exact ACPF to minimize a compromise between transmission losses and turbined outflow. The testbed is the Santo Antônio system, composed of 50 generating units, 13 power transformers, and 41 buses. Simulations based on real-life data demonstrate the impact of ACPF modeling, achieving consistently reduced losses above 5%, at the cost of a higher processing time.