An Extended Optimal Transmission Switching Algorithm Adapted for Large Networks and Hydro-Electric Context

Previous works have shown that the best topology of an electrical network depends on the total demand and its distribution. Optimal Transmission Switching (OTS) identifies lines to be opened to minimize operating costs. However, this cost-based criterion is not suitable for hydropower generation-based companies, where hydrology largely dictates the power generation. Moreover, no study about impact of OTS on voltage stability margins have been conducted in literature as it never been explicitly integrated in the problem formulation. Thus, OTS does not guarantee that proposed topologies are secure even if voltage bounds are respected. It also does not take full advantage of the real networks flexibility by including only line states and production distribution in the control vector. This leads to algorithms that are not suitable for weakly meshed (or mostly radial) networks. In this paper, we propose an extended OTS (E-OTS) that includes several improvements over current algorithms and overcomes the above-mentioned problems. We also propose two heuristics to reduce resolution time. Results on the PEGASE (1354 bus) and Polish (2236 bus) networks show that E-OTS identifies a topology improvement in less than 40 minutes, which is low enough to be implemented in a real energy management system. Tests have been made for three different criteria.