Periodic Reporting for period 1 - FRESLING (FREquency Security of Low-INertia electrical Grids)
Periodo di rendicontazione: 2021-07-01 al 2023-06-30
For the European Union (EU), the use of renewable energy resources has become the key to addressing environmental-related issues. Power electronic technology has been recognized as an effective solution to accommodate these increasing renewable resources in power grids. However, unlike the traditional synchronous generators (SGs), the dynamic behaviour of these converter-interfaced generators (CIGs) varies greatly with the actual control methods. The differences between CIGs and SGs can make the modelling, stability criterion, and control methods originally developed for traditional SG-dominated power grids no longer valid, which may prevent the integration of increasing renewable energy resources into the system. Moreover, the CIGs are essentially semiconductor-based switches without physical inertia. Under large disturbances, the CIG dynamics can become much faster than that of the SGs. How the fast dynamics of CIGs can affect power system stability is still unclear, which is investigated during this action.
To support the EU’s path to a sustainable economy, research into methods that assess and enhance the large-signal stability of low-inertia grids can have a great impact on the lives of many people and save society a lot of resources. The obtained academic achievements will become a milestone in addressing the low-inertia system security issues since it is the first time in the literature that the physical relationship between the nonlinear behaviour and the controlled dynamics of CIGs is established. In future research, the project results can be extended to several other relevant security issues of low-inertia grids. Furthermore, the project will also directly lead to the education of young researchers with relevant, unique research profiles within the area.
The main objective of this action is to assess and enhance the frequency security of a low-inertia power grid. Three issues have been studied during this action.
a) Dynamic modelling: Develop the model of a low-inertia power grid, including both the model of the CIGs and the electrical network, which can describe the dynamic behaviour of the system under large disturbances.
b) Stability assessment: Based on the developed model, investigate the transient stability and frequency stability of a power grid with CIGs.
c) Control design: Design control methods that can enhance the stability of the low-inertia power grid to accommodate the increasing renewable resources.
Other objectives including the FRESLING project management, training and career development, and the dissemination and communication of the research results have been also achieved through this action.
To support the EU’s path to a sustainable economy, research into methods that assess and enhance the large-signal stability of low-inertia grids can have a great impact on the lives of many people and save society a lot of resources. The obtained academic achievements will become a milestone in addressing the low-inertia system security issues since it is the first time in the literature that the physical relationship between the nonlinear behaviour and the controlled dynamics of CIGs is established. In future research, the project results can be extended to several other relevant security issues of low-inertia grids. Furthermore, the project will also directly lead to the education of young researchers with relevant, unique research profiles within the area.
The main objective of this action is to assess and enhance the frequency security of a low-inertia power grid. Three issues have been studied during this action.
a) Dynamic modelling: Develop the model of a low-inertia power grid, including both the model of the CIGs and the electrical network, which can describe the dynamic behaviour of the system under large disturbances.
b) Stability assessment: Based on the developed model, investigate the transient stability and frequency stability of a power grid with CIGs.
c) Control design: Design control methods that can enhance the stability of the low-inertia power grid to accommodate the increasing renewable resources.
Other objectives including the FRESLING project management, training and career development, and the dissemination and communication of the research results have been also achieved through this action.
The project contains 6 work packages (WPs). The first WP has been carried out to deal with the project management activities. In WP 2, large-signal CIG models with different control methods have been developed. Moreover, the voltage-dependent network models have been also investigated in this part. In WP 3, the stability of a low-inertia power grid has been investigated. Two main tasks have been considered in this WP. The first one is the transient stability of CIGs, which is the pre-condition for frequency stability analysis. The second one is the frequency stability assessment of a low-inertia power system. In WP 4, security-enhanced control designs have been developed, which can help integrate the increasing CIGs into the power grid. Two tasks have been achieved in this part, i.e. the control design to enhance the transient stability of a single CIG and the control design to enhance the frequency security of a low-inertia power grid. For WP 5, two tasks including personal career development and knowledge transfer have been completed. Finally, WP 6 has been carried out to disseminate and communicate the research results to the public including people in both academia and industry and the public.
The research results have been published in five journal articles and one conference proceeding. Besides, two tutorials will be presented at EPE’23 ECCE Europe and eGRID 2023 in September and October 2023.
The research results have been published in five journal articles and one conference proceeding. Besides, two tutorials will be presented at EPE’23 ECCE Europe and eGRID 2023 in September and October 2023.
Firstly, simplified models of CIGs with typical control methods under large disturbances have been presented, which can assess the dynamic behaviour of the CIGs accurately. The developed model can reveal the physical nature of the control loops, which can help people in both academia and industry to understand the operation principles of the CIGs without looking too many details into the control loops. Moreover, the developed model may be integrated into power system analysis tools for large-signal stability analysis.
Next, with the developed simplified CIG models, the transient stability of the CIG-based power system has been analysed, which is the pre-condition for frequency security. Further, the frequency dynamics of the CIG-based power system has been investigated. The results reveal the relationship between transient stability and frequency security in a low-inertia power system with CIGs and SGs. Several control and system parameters along with their positive and negative impacts on system stability have been taken into account in this analysis, which gives a guideline for power grid evolution.
Finally, stability-enhanced control methods for CIGs have been developed, which are robust to various grid conditions. Compared to existing control methods, the advantages of the proposed method have been verified by experimental tests.
The results can be further utilized in other related-research activities. To date, the published articles have been cited more than 50 times, among which most of the researchers are in the field of power electronics and power systems.
The proposed research results can contribute to addressing climate change or environmental issues. Through the proposed research activities, the operational principles of the CIGs have been physically revealed. The developed simplified CIG models can be utilized not only for the considered stability or security assessment but also for other types of large-signal stability problems. The solution to these problems can help integrate more renewable energy resources into the power system to further reduce the EU’s greenhouse gas emissions.
Next, with the developed simplified CIG models, the transient stability of the CIG-based power system has been analysed, which is the pre-condition for frequency security. Further, the frequency dynamics of the CIG-based power system has been investigated. The results reveal the relationship between transient stability and frequency security in a low-inertia power system with CIGs and SGs. Several control and system parameters along with their positive and negative impacts on system stability have been taken into account in this analysis, which gives a guideline for power grid evolution.
Finally, stability-enhanced control methods for CIGs have been developed, which are robust to various grid conditions. Compared to existing control methods, the advantages of the proposed method have been verified by experimental tests.
The results can be further utilized in other related-research activities. To date, the published articles have been cited more than 50 times, among which most of the researchers are in the field of power electronics and power systems.
The proposed research results can contribute to addressing climate change or environmental issues. Through the proposed research activities, the operational principles of the CIGs have been physically revealed. The developed simplified CIG models can be utilized not only for the considered stability or security assessment but also for other types of large-signal stability problems. The solution to these problems can help integrate more renewable energy resources into the power system to further reduce the EU’s greenhouse gas emissions.