Calculating the Risk of Power Shortage in the Nordic Power System

Abstract: In the near future, the decommissioning of large power plants is planned in the Nordicelectric power system, due to environmental and market reasons. This will be counteredby an increase in the wind power installed capacity, as well as by signicant investmentsin the transmission system. In such a context, characterized by several changes, theNordic power system might face reliability challenges.This thesis aims to calculate the risk of power shortage in the dierent price areas whichconstitute the Nordic power system, for three dierent scenarios: a base scenario 2015,scenario 2020, and scenario 2025. Dierent case studies, focusing on the Nordic powersystem and on some of its subsystems, are investigated. The reliability evaluation whichis carried out follows a probabilistic approach, by means of Monte Carlo simulations.Crude Monte Carlo, as well as an advanced variance reduction technique { namely Cross-Entropy based Importance Sampling (CEIS) { are applied and compared. An alternativesampling method based on stratied sampling is presented too.The starting point of this thesis is Viktor Terrier's 2017 Master thesis, \North EuropeanPower Systems Reliability" [1]. Model-wise, among the other improvements, load andwind power are sampled in a dierent way to account for the correlation between them.Data-wise, more realistic assumptions are made and more accurate data are used, thanksalso to the collaboration with Sweco Energuide AB, Department of Energy Markets.From the model perspective, it is concluded that CEIS outperforms crude Monte Carlowhen simulating small to medium size systems, but it cannot be successfully appliedwhen simulating large and very reliable systems like the Nordic system as a whole. Thepresented alternative sampling method can however be used for such cases. From thenumerical-results perspective, the drawn conclusion is that the Nordic power system isestimated to become more reliable by years 2020 and 2025. Even if partly intermittent,more generation capacity is expected to be available, and thanks to the signicant investmentswhich are planned in the transmission system, it will be possible to eectivelytransmit more power where needed, regardless of the area where it has been generated.The thesis is carried out at KTH Royal Institute of Technology, Department of ElectricPower and Energy Systems, in collaboration with Sweco Energuide AB, Department ofEnergy Markets, within the frame of the North European Energy Perspectives Project(NEPP).