PhD defence by Helma Maria Tróndheim
24.06.2022 kl. 13.00 - 16.00
Helma Maria Tróndheim, AAU Energy, will defend the thesis "Ensuring Supply Reliability and Grid Stability in a 100% Renewable Electricity Sector in the Faroe Islands"
Ensuring Supply Reliability and Grid Stability in a 100% Renewable Electricity Sector in the Faroe Islands
Helma Maria Tróndheim
Professor Claus Leth Bak
Associate Professor Filipe Faria da Silva
Bárður A. Niclasen (UFI) and Terji Nielsen (SEV)
Hans Pauli Joensen (UFI)
Bogi Bech Jensen, University of the Faroe Islands (UFI) (Chairman)
Göran Anderson, Swiss Federal Institute of Technology
Thomas Ackermann, Energynautics GmbH
The Power Company in the Faroe Islands, SEV, and the Faroese Government have a vision to reach a 100% renewable electricity production by 2030. A tangible plan is needed in order to reach this ambitious goal, whilst ensuring supply reliability and grid stability in this isolated power system. This is the objective of this research project.
Ensuring the security of supply and resource adequacy in a power system predominately based on renewable energy resources is challenging, due to the weather dependency of the production and available storage options, especially in an isolated system. The first part of this thesis focuses on obtaining a tangible RoadMap with investments in generation, storage and transmission capacity needed to reach a 100% renewable electricity production in the Faroe Islands by 2030 and thus, ensures supply reliability. Existing expansion planning tools primarily consist of optimisation algorithms, which optimise capacities annually. Hence, the capacity of e.g. a specific transmission cable can increase year by year, whilst in reality a cable is either installed or not. This study uses the economic optimisation tool Balmorel, which optimises the investments and dispatch. A method to translate these optimal results to a practical RoadMap, has been developed. This method also considers practical constraints like the local resource potential, power plant locations and sizes.
Multiple scenarios, considering different technologies, have been analysed. Additionally, a sensitivity analysis of investment and fuel costs has been conducted. According to the results investing in renewables is the economically best option up to 87% renewable energy. Reaching 100% renewables in 2030 requires increasing the renewable generation capacity by almost 80\% compared to the capacity needed for 87% renewables. The study also shows that if the potential of tidal energy can be unlocked, it has a disruptive influence on the future power system, as 72 MW of tidal power could replace 155 MW of hydro, wind, photovoltaic and battery power and decrease the pumped storage reservoir capacity by 75%.
The second part of the study focuses on investigating the grid stability of the power system through dynamic simulations. This study focuses on the grid on the isolated island of Suðuroy, which has a electricity demand that is around 10\% of the total demand. Starting with Suðuroy will provide valuable lessons learned to the rest of the system. In order to investigate the stability, a model suitable for load flow and dynamic simulations has been developed and validated. The available information about the governors and automatic voltage regulators of the synchronous generators is very limited. Therefore, these have been modelled using standard models. Using some of the existing approaches to parameterise the models, did not result in a model which could be dynamically validated. Therefore, a procedure combining different existing approaches was developed in order to parameterise and validate these models.
Dynamic RMS simulations over a 4.5 hour period without disturbances and shorter simulations, e.g. 30 seconds, with large disturbances have been conducted. The frequency and voltage fluctuations and their dependency on inverter-based generation shares and fluctuations have been investigated through the 4.5 hour simulations. The stability in Suðuroy towards 2030 has been investigated through the shorter simulations with disturbances. The study shows that initiatives are necessary in order to maintain the same frequency and voltage stability at the same level as today. However, according to the RoadMap the grid of Suðuroy should be connected to the main grid in 2026 through a subsea cable. The main grid is significantly larger than the grid of Suðuroy, and therefore contributes with ancillary services to Suðuroy. Two network reduction models and one detailed model have been used to represent the main grid in the simulations post 2026, and the results show that using network reductions causes implications when frequency triggered technologies, in this case batteries, are contributing to the stability. The dynamic stability of Suðuroy should be investigated further, especially scenarios in which the subsea cable to the main grid is out of service. The dynamic stability of the main grid also has to be studied.
The results of this research project are of great significance when in the transition toward a 100% renewable electricity sector in the Faroe Islands. The methods developed and lessons learned can also be applied to other power systems, especially similar power systems.
THE DEFENCE will be IN ENGLISH - all are welcome.
University of the Faroe Islands (UFI) / AAU Energy