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

Danilo P C Filho,Antonio F C Aquino,Erlon C Finardi

doi:10.1109/access.2021.3124041

Danilo P C Filho, Antonio F C Aquino + Show 1 more

Open Access

https://doi.org/10.1109/access.2021.3124041

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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 Antonio 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.

Highlights

One of the most crucial tasks for hydroelectric plant operation is real-time dispatch (RTD), which addresses the optimal distribution of the power generation among the available generating units (GUs)
Due to the quality of the approximations, the solution strategy proposed in this work can provide better losses reductions, assuring that power targets are met at delivery buses more accurately and, most importantly, evaluate the feasibility guarantee of the dispatch regarding the profile of reactive power flow, which is crucial in this system
Note that all the deviations are within margins of tolerance that can be applied for classical static AC power flow (ACPF) analysis

Summary

Introduction

One of the most crucial tasks for hydroelectric plant operation is real-time dispatch (RTD), which addresses the optimal distribution of the power generation among the available generating units (GUs). The solution obtained in this optimization problem is used in real-time operation to assist production allocation among GUs. efficient computation of the RTD is of particular importance since, in generation scheduling models, hydro plants are represented by power production and turbined outflow functions, usually built using the optimal values related to RTD. In addition to computational efficiency, adequate RTD modeling is an important issue [1], and studies have shown that significant gains can be rendered by adequately allocating the power between GUs [2]-[3]. We can mention the reservoir water balance, limits of net head and power of the GUs, rates of variation of outflow, and operating power reserve requirements as additional typical constraints

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Conclusion