Continuous Balancing of Power Systems With High Shares of Wind and Solar Power
Methods for Estimation of Needs and Efficient Use of Balancing Services in Future Electricity Markets
Time: Mon 2025-11-10 10.00
Location: Kollegiesalen, Brinellvägen 8, Stockholm
Video link: https://kth-se.zoom.us/s/61811645829
Language: English
Subject area: Electrical Engineering
Doctoral student: Henrik Nordström , Elkraftteknik
Opponent: Associate Professor Kenneth Bruninx, TU Delft, Delft, The Netherlands
Supervisor: Professor Lennart Söder, Elkraftteknik; Professor Robert Eriksson, System Development, Svenska kraftnät
QC 20251010
Abstract
Transmission System Operators (TSOs) are responsible for maintaining the continuous balance in power systems, ensuring that intended electricity production matches demand in real time. To achieve this, they procure balancing services, i.e., resources that can adjust their production or consumption in response to system needs. The growing shares of Variable Renewable Energy (VRE) sources increase the operational uncertainty and variability, creating new challenges related to continuous balancing. At the same time, emerging flexible technologies and stronger European cooperation offer new opportunities to address these challenges. These developments make the efficient use and design of balancing services in VRE-dominated systems an urgent research topic. This thesis presents a series of research works focusing on the future needs for, and efficient use of, balancing services in power systems with high shares of wind and solar power.
The thesis first presents a comparative analysis of continuous balancing strategies in six power systems with ambitious VRE targets. The findings indicate that there appears to be no single solution to continuous balancing at high VRE shares, and that a broad set of technologies needs to contribute to the future continuous balancing.
Then, the Power Imbalance Model (PIM) is introduced as a new simulation framework for generating 1-minute resolution power imbalance scenarios. By using economic dispatch results as input data, PIM generates imbalance scenarios by detailed modelling of power system technologies, enabling both long-term assessment of balancing needs and generation of realistic input data for operational mechanisms.
Next, the thesis evaluates the benefits of a dynamic dimensioning approach for Frequency Restoration Reserves (FRR) in the Nordic area, using a newly developed FRR dimensioning model that incorporates chance-constrained optimization and PIM data. The results demonstrate that dynamic dimensioning adapts reserve requirements to operating conditions more efficiently, maintaining the operational reliability at the desired level.
Thereafter, a new market clearing mechanism for the Nordic manual FRR (mFRR) capacity market is proposed. By accounting for both capacity and expected activation costs, the mechanism yields considerable cost savings compared to current practices. The resulting optimization problem is efficiently solved with a tailored decomposition algorithm.
Finally, a stochastic optimization model for system cost-minimizing Battery Energy Storage System (BESS) scheduling is developed. This model is applied to analyze the impact of new requirements on Limited Energy Reservoir (LER) technologies providing Frequency Containment Reserves (FCR). Results indicate that such requirements considerably reduce the BESSs' FCR provision.
Overall, the thesis advances both the modeling tools and the design of operational mechanisms needed to ensure a reliable and cost-efficient continuous balancing of future European power systems with high VRE shares.