Short-Circuit Capacity from Inverter-Based Resources
(2025) In CODEN:LUTEDX/TEIE EIEM01 20251Industrial Electrical Engineering and Automation
- Abstract
- Inverter-based resources are playing an increasingly important role in power systems. However, the ability of inverter-based resources to deliver short-circuit currents is very limited, and often lies in the range of 1.2 to 2 p.u. for current power modules. This range is considerably lower when compared to that of synchronous generators, yielding short-circuit currents between 6 to 8 p.u. The difference in fault current contribution has a direct effect on the short-circuit capacity, determining the grid strength, stability, and ability to handle voltage sags. The difference in fault current magnitude also makes for difficulties regarding relay protection systems such as overcurrent protection.
Challenges in fault detection can lead to... (More) - Inverter-based resources are playing an increasingly important role in power systems. However, the ability of inverter-based resources to deliver short-circuit currents is very limited, and often lies in the range of 1.2 to 2 p.u. for current power modules. This range is considerably lower when compared to that of synchronous generators, yielding short-circuit currents between 6 to 8 p.u. The difference in fault current contribution has a direct effect on the short-circuit capacity, determining the grid strength, stability, and ability to handle voltage sags. The difference in fault current magnitude also makes for difficulties regarding relay protection systems such as overcurrent protection.
Challenges in fault detection can lead to severe problems such as large voltage sags and frequency variation if not handled in time. Due to the difference in short-circuit current contribution between synchronous generators and inverters, new ways of handling and detecting faults in the power system might be needed. This report aims to investigate enabling factors to increase overcurrents, which refers to current magnitudes exceeding the rated value, from inverter-based resources. It also examines how these overcurrents affect voltage quality and fault detection. The difference in terms of ancillary services and overcurrent capabilities between grid-forming converters and synchronous generators are also discussed.
A literature study was conducted as a first approach to answer the research questions. A power grid model mimicking the conditions found in the south of Sweden (SE4) was then constructed in DIgSILENT PowerFactory in order to validate the findings from the literature. These findings were then compared and analyzed in accordance with regulations in EIFS 2023:3 regarding voltage quality, issued by Energimarknadsinspektionen.
It is deemed possible to increase fault currents by overrating, considering the control structure, and improving the hardware of the power module and converter. Promising factors regarding power module control includes enabling direct tuning of the output current for the voltage controller, decrease of switching frequency and rapid control from grid-forming converters. In terms of hardware enablers, an effective cooling system such as micro channel cooling and using phase change materials show promising results. Improving the robustness of the power module using better suited materials with matching heat expansion coefficients, more efficient heat transfer, and higher melting point, can also improve overcurrent performance.
Increasing the current from grid-forming converters enable significantly better detection for overcurrent relays as well as a better voltage quality. Grid-forming converters are also shown to possess equal abilities to provide ancillary services as those of synchronous generators with the exception of their fault current limitation, as well as the need for an external energy storage system. On the contrary, grid-forming converters show a faster rate of response and parameter tuning flexibility when compared to a synchronous generator.
It is presented that increased fault currents from inverter-based resources are possible up to three per unit with current measures. It might however be worth considering protection systems that are not dependent on high overcurrents such as distance and differential relays for system with low short-circuit power. A high short-circuit capacity may not always be a necessity either if regulations regarding voltage quality are met. A lower short-circuit power would also imply that circuit breakers and relays do not have to be dimensioned for as large fault currents. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9206715
- author
- Haväng, August LU and Klangeryd, Simon LU
- supervisor
- organization
- alternative title
- Kortslutningskapacitet från omriktaranslutna energikällor
- course
- EIEM01 20251
- year
- 2025
- type
- H3 - Professional qualifications (4 Years - )
- subject
- publication/series
- CODEN:LUTEDX/TEIE
- report number
- 5540
- language
- English
- id
- 9206715
- date added to LUP
- 2025-06-30 13:14:40
- date last changed
- 2025-06-30 13:14:40
@misc{9206715,
abstract = {{Inverter-based resources are playing an increasingly important role in power systems. However, the ability of inverter-based resources to deliver short-circuit currents is very limited, and often lies in the range of 1.2 to 2 p.u. for current power modules. This range is considerably lower when compared to that of synchronous generators, yielding short-circuit currents between 6 to 8 p.u. The difference in fault current contribution has a direct effect on the short-circuit capacity, determining the grid strength, stability, and ability to handle voltage sags. The difference in fault current magnitude also makes for difficulties regarding relay protection systems such as overcurrent protection.
Challenges in fault detection can lead to severe problems such as large voltage sags and frequency variation if not handled in time. Due to the difference in short-circuit current contribution between synchronous generators and inverters, new ways of handling and detecting faults in the power system might be needed. This report aims to investigate enabling factors to increase overcurrents, which refers to current magnitudes exceeding the rated value, from inverter-based resources. It also examines how these overcurrents affect voltage quality and fault detection. The difference in terms of ancillary services and overcurrent capabilities between grid-forming converters and synchronous generators are also discussed.
A literature study was conducted as a first approach to answer the research questions. A power grid model mimicking the conditions found in the south of Sweden (SE4) was then constructed in DIgSILENT PowerFactory in order to validate the findings from the literature. These findings were then compared and analyzed in accordance with regulations in EIFS 2023:3 regarding voltage quality, issued by Energimarknadsinspektionen.
It is deemed possible to increase fault currents by overrating, considering the control structure, and improving the hardware of the power module and converter. Promising factors regarding power module control includes enabling direct tuning of the output current for the voltage controller, decrease of switching frequency and rapid control from grid-forming converters. In terms of hardware enablers, an effective cooling system such as micro channel cooling and using phase change materials show promising results. Improving the robustness of the power module using better suited materials with matching heat expansion coefficients, more efficient heat transfer, and higher melting point, can also improve overcurrent performance.
Increasing the current from grid-forming converters enable significantly better detection for overcurrent relays as well as a better voltage quality. Grid-forming converters are also shown to possess equal abilities to provide ancillary services as those of synchronous generators with the exception of their fault current limitation, as well as the need for an external energy storage system. On the contrary, grid-forming converters show a faster rate of response and parameter tuning flexibility when compared to a synchronous generator.
It is presented that increased fault currents from inverter-based resources are possible up to three per unit with current measures. It might however be worth considering protection systems that are not dependent on high overcurrents such as distance and differential relays for system with low short-circuit power. A high short-circuit capacity may not always be a necessity either if regulations regarding voltage quality are met. A lower short-circuit power would also imply that circuit breakers and relays do not have to be dimensioned for as large fault currents.}},
author = {{Haväng, August and Klangeryd, Simon}},
language = {{eng}},
note = {{Student Paper}},
series = {{CODEN:LUTEDX/TEIE}},
title = {{Short-Circuit Capacity from Inverter-Based Resources}},
year = {{2025}},
}