The objective of this research is to present a comprehensive framework for harnessing the flexibility of power systems in the presence of unforeseen events, such as those associated with component outages or renewable energy variability. Increased penetration of variable resources in the power grid, mainly in the form of wind and solar plants, has resulted in variable power flow patterns, increased thermal unit cycling and higher reserve capacity requirements. Furthermore, the variability of renewable energy output has increased the system’s ramping requirements and threatens the system’s voltage control capabilities. However, new sources of flexibility and network control are emerging to address these problems. Specifically, energy storage systems, demand side management, distributed energy resources and flexible transmission operation can participate by providing ramping services and/or voltage control, as well as by alleviating transmission congestion. This research focuses on contributing to modeling and optimization approaches for scheduling the operation of these sources of flexibility in a certain look-ahead horizon, ensuring a state of the art level of modeling accuracy, with full inclusion of voltage control considerations which do not exist in current DC-OPF modeling approaches. Also, by including reactive power flows, the network congestion model proposed is above par compared to the current state-of-the-art for look-ahead dispatch literature. Nevertheless, the model is further expanded by including a thermal model for transmission lines, which allows for the implementation of dynamic line ratings in look-ahead economic dispatch. The benefits from these augmented modeling capabilities are documented and compared with current operating practices. Once an AC-OPF look-ahead optimization problem has been established, and the corresponding components have been modeled, further contributions are made in the area of remedial action schemes. The developed formulations allow for the identification of appropriate corrective actions that will restore feasibility in infeasible cases. Finally, a combination of contingency filtering and contingency analysis approaches is developed, to allow for fast identification and analysis of critical outages in the transmission system. The filtering approach is based on a basic Taylor expansion of network power flow equations as well as a new formulation of margin indices that directly quantify the proximity to constraint violation in the post-outage system state. The analysis approach is based on low-rank modifications of the Jacobian matrix of network equations, to produce good estimates of post-outage operating states and map the effect on the system’s operating constraints. Compared to current state of the art, advances are made both in the speed and the accuracy of the analysis, since the proposed filtering and analysis methods are fully unbalanced. The need for unbalanced security analysis is discussed and justified. Through the contributions made in this research, a roadmap to increase flexibility in power system operations is developed. Namely, an enhanced modeling capability allows for integration of additional sources of flexibility and voltage control and a highly accurate security analysis and remedial actions formulation allows for improved response to unforeseen critical outages and rapid generation changes.

För att Sverige ska uppnå de energimål som satts upp i enighet med Agenda 2030, är det av stor vikt att implementera mer förnybara resurser. Sektorkopplingsstrategier är en potentiell åtgärd vilket skulle optimera det svenska energisystemet. På sikt skulle det även kunna frigöra kapacitet, och därmed möjliggöra hantering av en större andel förnybara källor i elnätet. Syftet med den här studien är att bistå med en nulägesrapport av sektorkopplingsetablering i Sverige, med särskild fördjupning i region Gotland. Studien grundas i en omfattande litteraturstudie och kvalitativa intervjuer. Genom att studera tidigare litteratur inom området identifierades tekniker och metoder inom sektorkoppling, vars nuvarande utsträckning i Sverige kartlades. Den fördjupade datainsamlingen för studien var ostrukturerade kvalitativa intervjuer med projektledare och aktörer med relevans för Gotland. Resultatet från studien är en sammanställning av sektorkopplingtekniker samt hur dessa kan bidra till att öka flexibiliteten i energisystemet i allmänhet, och elnätet i synnerhet. Vidare kartlades projekt i Sverige som tillämpar dessa tekniker. Slutsatserna visar på att sektorkoppling redan är etablerat i Sverige, men befinner sig i ett tidigt stadium. Resultatet visade vidare att det krävs engagemang från kunder och aktörer, samt en viss standard i energisystemet för att möjliggöra en framgångsrik tillämpning av sektorkoppling i det svenska energisystemet. Resultaten belyser likväl att en fortsatt etablering av sektorkoppling kan komma att kräva ekonomiska incitament i form av bidrag och satsningar. / Including more renewable energy sources in the energy system is of great importance to enable Sweden to achieve its climate goals in unity of Agenda 2030. Sector coupling is a potential strategy for energy optimization, which in time could become a more established method to manage capacity issues, as well as permitting more renewable energy sources in the electricity grid. The purpose of this study is to compile a status report on current sector coupling in Sweden, with additional further investigation of region Gotland. The study is based on a comprehensive literature study as well as data collection through qualitative interviews with relevant stakeholders. Previous research and literature in the field enabled the identification of different technologies and methods relating to sector coupling. Qualitative data was gathered through unstructured interviews with represenatatives from companies and organizations having their focus set on energy planning in the Gotland region. The results consist of an assortment of various sector coupling technologies and their ability to increase the flexibility of the power grid and energy system in Sweden. In addition, several projects with diverse implementation of sector coupling strategies were also being mapped out. In conclusion, it became apparent that sector coupling is only at its earlier stages of implementation in Sweden. Further interest and commitment by customers and businesses is of great importance and needed to enable expansion of sector coupling technologies in Sweden. Moreover, the energy system requires standards, as well as financial incentives to promote further use of sector coupling in society.