Grid Capacity : Challenges and Opportunities
Nätkapacitet : Utmaningar och Möjligheter
Author
Summary, in English
Electric power grids have a limited capacity for safe and reliable transfer of power. Due to the ongoing large-scale expansion of variable renewable energy sources, such as wind and solar, there is a growing need for rapid grid
capacity increase.
This thesis explores methods for improving and expanding grid capacity through control of converter-interfaced energy resources, including wind and solar plants, and battery energy storage systems. The objective is to safely operate existing networks at their capacity limits, which improves grid utilisation and reduces reliance on slow infrastructure upgrades. Specifically, voltage and power flow constraints in distribution networks, and power flow limits in transmission networks are considered in the presented research.
The thesis contains two main research contributions. The first concerns development of new control methods for converter-interfaced resources. Three types of PI control based methods are proposed. First, voltage limitation strategies for distribution networks based are presented (Papers I and II). Through adjustments of both active and reactive power, mitigation of overvoltage is ensured in networks with low X/R ratios. Second, a method for
congestion management in distribution networks is developed, for which control actions are organised through a flexibility dispatch list (Paper III). Third, a method for coordinated control of energy storage systems to form a virtual power line is investigated (Paper IV). The virtual power line allows for improved utilisation of existing transmission network capacity, as well as temporary increases in power transfer between different areas.
The second main research contribution concerns methods for modelling and analysis of grid capacity in power systems with large shares of renewable generation. The general characteristics of the renewable energy expansion
are first introduced (Paper I). A modelling framework is developed for analysis of nonlinear dynamics of local voltage controllers in a quasi-static grid model (Paper II). Virtual power line control, sizing, and placement is analysed in a system model based on power transfer distribution factors (Paper IV). Finally, a capacity expansion model is developed, with a detailed representation of electricity market dynamics heavily influenced by weather variability (Paper V).
The results indicate that significant improvements to grid utilisation in existing power systems is possible through low-complexity decentralised control strategies for inverter-interfaced resources.
capacity increase.
This thesis explores methods for improving and expanding grid capacity through control of converter-interfaced energy resources, including wind and solar plants, and battery energy storage systems. The objective is to safely operate existing networks at their capacity limits, which improves grid utilisation and reduces reliance on slow infrastructure upgrades. Specifically, voltage and power flow constraints in distribution networks, and power flow limits in transmission networks are considered in the presented research.
The thesis contains two main research contributions. The first concerns development of new control methods for converter-interfaced resources. Three types of PI control based methods are proposed. First, voltage limitation strategies for distribution networks based are presented (Papers I and II). Through adjustments of both active and reactive power, mitigation of overvoltage is ensured in networks with low X/R ratios. Second, a method for
congestion management in distribution networks is developed, for which control actions are organised through a flexibility dispatch list (Paper III). Third, a method for coordinated control of energy storage systems to form a virtual power line is investigated (Paper IV). The virtual power line allows for improved utilisation of existing transmission network capacity, as well as temporary increases in power transfer between different areas.
The second main research contribution concerns methods for modelling and analysis of grid capacity in power systems with large shares of renewable generation. The general characteristics of the renewable energy expansion
are first introduced (Paper I). A modelling framework is developed for analysis of nonlinear dynamics of local voltage controllers in a quasi-static grid model (Paper II). Virtual power line control, sizing, and placement is analysed in a system model based on power transfer distribution factors (Paper IV). Finally, a capacity expansion model is developed, with a detailed representation of electricity market dynamics heavily influenced by weather variability (Paper V).
The results indicate that significant improvements to grid utilisation in existing power systems is possible through low-complexity decentralised control strategies for inverter-interfaced resources.
Department/s
Publishing year
2025
Language
English
Full text
Document type
Dissertation
Publisher
Division of Industrial Electrical Engineering and Automation, Faculty of Engineering, Lund University
Topic
- Power Systems and Components
Status
Published
Project
- Grid Capacity - Challenges and Opportunities
Supervisor
- Olof Samuelsson
- Emil Hillberg
ISBN/ISSN/Other
- ISBN: 978-91-985110-7-9
- ISBN: 978-91-985110-6-2
Defence date
3 October 2025
Defence time
09:00
Defence place
Lecture Hall M:B, building M, Ole Römers väg 1F, Faculty of Engineering LTH, Lund University, Lund.
Opponent
- Sami Repo (Prof.)