Value based transmission expansion planning of hydrothermal systems with multiple scenarios

The network loading of a hydrothermal system is highly variable due to several factors. Hydro plants are usually located in different river basins, usually far from load centers. Diversity of streamflows along these basins lead to distinct generation dispatches, sometimes inverting energy interchanges between hydro based exporting regions, and also redistributing the power supplied to load centers. Transmission expansion planning criteria must reflect the trade-off between investments in transmission, inducing more competition in generation, at the expense of increasing customer costs and a higher reliability level due to these investments. Measuring these trade-offs for hydrothermal systems requires taking into account multiple dispatch scenarios, and assessing network reliability for each scenario by a contingency analysis for each circuit outage. The network design problem that aims at choosing the best reinforcements among many candidate routes and voltage levels must therefore represent the transmission constraints for relevant dispatch scenarios and circuit contingencies. In this work a mixed integer disjunctive model is extended so as to deal with this problem minimizing the sum of investment costs and network reliability worth, measured by average interruption costs due to contingencies. Real world case system applications show that by means of a judicious choice of scenarios and contingencies, despite the increase of problem size the model is applicable, achieving a balanced choice between network re liability and investment requirements.