Transmission system reconfiguration for congestion management: DC-AC algorithm and Croatian transmission system case study

Transmission system operators monitor and manage the power network with a goal of achieving secure operation. Contingency analysis lists outage scenarios that can cause line overloading. Operators can activate flexible devices and recon-figure network topology to move the system operating point to achieve N-1 security. This paper analyses the effectiveness of the DC model for solving security constrained optimal power flow (SCOPF) in comparison to the AC model in terms of accuracy and computation time. Then it uses DC-AC algorithm to solve SCOPF problem considering both activation of flexible devices and topology reconfiguration. DC-AC algorithm uses DC model to determine topology and then it resolves with the AC for fixed topology. The results show that the DC model is of fair accuracy, but much faster to solve if model has discrete variables. DC-AC algorithm results in 20% better objective function than in case of computing just the DC model.