Network partition based on critical branches for large-scale transmission expansion planning

The size and complexity of large power systems, such as the European one, often make them unmanageable for the purposes of Transmission Expansion Planning (TEP). Therefore, network reduction methods are necessary to condense their key features into a workable model, which should approximate the behavior of the nodal system as accurately as possible. We define critical branches as the transmission lines that are particularly relevant for TEP purposes because of, for instance, frequent congestions or a special nature such as the cases of HVDC (High-Voltage Direct Current) transmission lines or PSTs (Phase-Shifting Transformers). It would be desirable to preserve these critical branches while simplifying the remaining grid. We propose a heuristic algorithm that creates an initial partition that is later refined by clustering nodes based on a composite distance measure. The proposed technique has been applied to a real case study based on the French and Spanish systems.