Hybrid power plant in frequency control: Analysis of load sharing between turbine and energy storage, with a focus on synchronized operation and storage sizing
Thesis event information
Date and time of the thesis defence
Place of the thesis defence
OP auditorium (L10), Linnanmaa campus
Topic of the dissertation
Hybrid power plant in frequency control: Analysis of load sharing between turbine and energy storage, with a focus on synchronized operation and storage sizing
Doctoral candidate
Master of Science (Technology) Joni Vasara
Faculty and unit
University of Oulu Graduate School, Faculty of Technology, Intelligent Machines and Systems
Subject of study
Process Engineering
Opponent
Professor Esa Vakkilainen, LUT University
Second opponent
Professor Urban Lundin, Uppsala University
Custos
Docent István Selek, University of Oulu
Hybrid power plant in power grid frequency control
For the reliable operation of the power grid, the balance between consumption and generation is essential. The balance is maintained using frequency reserves, whose role is to restore the mismatch between the supply and demand of electricity. This dissertation focuses on the operation of a hybrid power plant, comprising a turbine and energy storage system, in the provision of the so-called FCR-N frequency reserve.
FCR-N reserve provision is regulated by technical requirements. Meeting these requirements can be challenging for turbines, such as Kaplan turbines, whereas energy storage systems can qualify smoothly. Partly for this reason, the number of energy storage systems has increased significantly in recent years.
If energy storage systems replace conventional turbines in the provision of frequency reserves, the significant regulation capacity of, e.g., hydropower plants remains unexploited. On the other hand, by combining the turbine and energy storage system, the strengths of both technologies can be utilized. The central research question of this dissertation is: how to share the power of a hybrid power plant between the turbine and energy storage in the provision of the frequency reserve?
The research focuses on answering the above question by taking into account the requirements set for the FCR-N reserve. The main objective of the analysis is to enhance understanding of the factors that impact load sharing between the turbine and energy storage, and the sizing of the energy storage system.
The key findings can be summarized as follows: power plant dynamic behavior has a significant impact on the efficiency of FCR provision and the sizing requirements of the energy storage system. In addition, with a small energy storage system, a significant reduction in the turbine contribution can be achieved, and secondly, simple load-sharing methods are sufficient when a large energy storage system is available and vice versa. Consequently, a well-designed hybrid power plant operation policy can result in a significant reduction in turbine contribution and reduce its wear and tear.
FCR-N reserve provision is regulated by technical requirements. Meeting these requirements can be challenging for turbines, such as Kaplan turbines, whereas energy storage systems can qualify smoothly. Partly for this reason, the number of energy storage systems has increased significantly in recent years.
If energy storage systems replace conventional turbines in the provision of frequency reserves, the significant regulation capacity of, e.g., hydropower plants remains unexploited. On the other hand, by combining the turbine and energy storage system, the strengths of both technologies can be utilized. The central research question of this dissertation is: how to share the power of a hybrid power plant between the turbine and energy storage in the provision of the frequency reserve?
The research focuses on answering the above question by taking into account the requirements set for the FCR-N reserve. The main objective of the analysis is to enhance understanding of the factors that impact load sharing between the turbine and energy storage, and the sizing of the energy storage system.
The key findings can be summarized as follows: power plant dynamic behavior has a significant impact on the efficiency of FCR provision and the sizing requirements of the energy storage system. In addition, with a small energy storage system, a significant reduction in the turbine contribution can be achieved, and secondly, simple load-sharing methods are sufficient when a large energy storage system is available and vice versa. Consequently, a well-designed hybrid power plant operation policy can result in a significant reduction in turbine contribution and reduce its wear and tear.
Created 14.4.2026 | Updated 15.4.2026