Date of Award
2025
Document Type
Thesis
Publisher
Edith Cowan University
Degree Name
Master of Engineering Science
School
School of Engineering
First Supervisor
Asma Aziz
Second Supervisor
Daryoush Habibi
Third Supervisor
Iftekhar Ahmad
Abstract
Due to the rapid uptake of distributed photovoltaic generation, the visible load to transmission operators in distribution feeders is reducing. Traditional load-shedding schemes are facing challenges due to this low-load situation. The required amount of load reduction cannot be achieved with the same load-shedding scheme as before. In some situations, with reverse power flows, load shedding can further increase the generation reduction. On the other hand, increased Rate of Change of Frequency (RoCoF) due to low inertia can result in false activation of under-frequency load shedding (UFLS) relays. These challenges can cause a serious problem with the power system security. Failure to achieve the objectives of load shedding can result in system-wide blackouts. The effect of these problems is more serious on isolated power systems due to their isolated nature. In the event of large disturbances, power cannot be imported or exported from neighboring systems, making frequency control particularly challenging, especially under high penetration of inverter-based generation.
As an alternative to UFLS, large-scale energy storage systems (ESS) could be used to provide contingency frequency response. This study investigates the impact of inverter control methodology on optimum sizing of the ESS to prevent UFLS. The optimal size is determined for ESS integrated with several Grid Forming (GFM) and Grid Following (GFL) control methods. The control parameters are treated as variables in the optimisation process, allowing the identification of the optimal set of control parameters that minimise the ESS size while preventing under-frequency load shedding. The power system is implemented in DIgSILENT PowerFactory, and the Hill climbing algorithm is used for optimisation. Given that a black box optimisation methodology is used, it is compatible with non-linear governor models and encrypted inverter-based models. Additionally, a detailed analysis of the variations in the minimum active power rating for different control parameters is provided. This analysis provides a deeper understanding of how different control parameters influence the required size of the energy storage system.
Further, this study investigates the performance of different inverter control techniques under different Distributed photovoltaic (DPV) penetration levels. This study evaluates four inverter control configurations: droop-based GFL inverter, droop with derivative control-based GFL inverter, droop-based GFM inverter, and VSG-based GFM inverter. The performances of these inverter types are compared for 27%, 45% and 72% DPV penetration levels. The impact of having a flywheel generator is analysed for 72% DPV penetration scenario. Performances are primarily evaluated by comparing the required minimum energy storage size to maintain frequency operating standards. By conducting this research, valuable insights are provided to power system planners of medium-sized isolated networks, enabling them to design future UFLS schemes effectively.
DOI
10.25958/g0nk-4x10
Access Note
Access to this thesis is embargoed until 4th April 2026
Recommended Citation
Manamperi, D. (2025). Investigation of under-frequency load shedding prevention of isolated medium-sized power systems using energy storage. Edith Cowan University. https://doi.org/10.25958/g0nk-4x10