Distributing Load Flow Computations Across System Operators Boundaries Using the Newton–Krylov–Schwarz Algorithm Implemented in PETSc

Abstract

The upward trends in renewable energy penetration, cross-border flow volatility and electricity actors’ proliferation pose new challenges in the power system management. Electricity and market operators need to increase collaboration, also in terms of more frequent and detailed system analyses, so as to ensure adequate levels of quality and security of supply. This work proposes a novel distributed load flow solver enabling for better cross border flow analysis and fulfilling possible data ownership and confidentiality arrangements in place among the actors. The model exploits an Inexact Newton Method, the Newton–Krylov–Schwarz method, available in the portable, extensible toolkit for scientific computation (PETSc) libraries. A case-study illustrates a real application of the model for the TSO–TSO (transmission system operator) cross-border operation, analyzing the specific policy context and proposing a test case for a coordinated power flow simulation. The results show the feasibility of performing the distributed calculation remotely, keeping the overall simulation times only a few times slower than locally.

Steady-State Stand-Alone Power Flow Solvers for Integrated Transmission-Distribution Networks: A Comparison Study and Numerical Assessment

“…Here, again, the transformation is based on the assumption that the boundary bus is completely balanced. Balanced three-phase power in pu is related to single-phase power in (10) according to the following relation:…”

“…Therefore, the splitting methods are advantageous as only a minimum amount of data sharing is necessary to perform load flow computations. Furthermore, in the unified methods, improvements have been made by the use of domain-decomposition methods [10], which allow different system operators to have a minimum amount of data sharing as well. Despite these improvements, there is still a clear distinction between these two, because computations in the unified methods need to be made on the same computer, while in the case of the master-slave splitting methods, system operators can be in geographically distinct locations and each can run their own computations.…”

“…Although the splitting methods are a domain decomposition method by design, the unified methods can also be solved using domain decomposition techniques. The authors of [10] introduced the Newton-Krylov-Schwarz method to solve the the unified integrated system in parallel. Next to the advantage of solving this system in parallel, it adds another advantage for the unified methods as only a limited amount of data have to be shared between system operators, just as the splitting methods.…”

“…Although legislation sometimes prohibits the use of stand-alone methods [6], enough potential use cases for these methods exist, to name a few: Some countries run their electricity network by one system authority being responsible for both transmission and distribution network operation, such as in Brazil [9]. Next to that, cooperation at the international level between system operators is increasing, such as in the European Union by ENTSO-E [10], which allows the use of a stand-alone tool for complete operation and planning. On top of that, one may argue that the innovations that arise from stand-alone methods may not only be valuable for the integrated system field, but also for merely balanced systems where imbalance arises on only a few lines [9].…”