Published in Formosa Journal of Science and Technology, the study evaluated renewable-energy penetration from 20% to 80% and GFM participation from 0% to 100% of renewable capacity. The researchers tested 60 scenarios involving generation loss, increased electricity demand, and three-phase faults. The results indicate that GFM technology can help compensate for some of the stability challenges associated with low-inertia electricity systems.
Renewable Energy Growth Changes How Power Grids Respond
Modern electricity systems are undergoing a major structural transition. Solar power, wind power, and battery energy storage are increasingly connected to the grid through power-electronic converters rather than conventional rotating generators.
Traditional synchronous generators naturally provide rotational inertia. This stored mechanical energy helps slow the rate at which system frequency changes when a sudden imbalance occurs. As these generators are displaced by inverter-based renewable resources, the overall system can become more sensitive to disturbances.
Conventional grid-following inverters generally synchronize with an existing voltage and frequency reference. In a grid with high renewable penetration and lower inertia, however, this dependence can create challenges, including faster frequency changes, deeper frequency drops, and synchronization problems.
Grid-forming inverters offer a different approach. Rather than simply following an existing grid reference, they can establish a controlled voltage waveform and actively contribute to frequency and voltage formation.
In the study by Endang Sukarna, Farrah Fauzia, Dwi Feriyanto, and Manovri Yeni, the GFM system was represented using a virtual synchronous machine (VSM) approach. This control method is designed to reproduce some characteristics of conventional synchronous generators, including virtual inertia and damping.
Researchers Tested 60 Power-System Scenarios
The researchers used an IEEE 9-bus benchmark system with a 100 MVA base and a nominal frequency of 50 Hz. Renewable penetration was set at four levels: 20%, 40%, 60%, and 80%.
At each renewable-energy level, the share of renewable capacity operating with GFM control was varied from 0%, 25%, 50%, 75%, to 100%. The researchers then exposed each configuration to three types of disturbances: a 10% loss of generation, a 10% increase in load, and a three-phase fault. This produced a total of 60 scenarios.
The analysis examined several indicators of grid performance, including the lowest frequency reached after a disturbance, the maximum rate of frequency change, recovery time, minimum voltage, and the amount of active power supplied by the GFM system. A separate analysis tested virtual-inertia settings ranging from 1 to 6 seconds.
Importantly, the authors describe the underlying dataset as a synthetic simulation benchmark. The numerical results therefore provide a controlled basis for comparing scenarios but require further validation through detailed dynamic models and hardware testing before being used as operational limits for real power grids.
Higher Renewable Penetration Without GFM Reduces Stability
The results showed a clear deterioration in frequency performance when renewable penetration increased while the renewable fleet remained entirely grid-following.
Under a 10% generation-loss event, increasing renewable penetration from 20% to 80% reduced the frequency nadir from 49.550 Hz to 48.806 Hz. At the same time, the maximum rate of change of frequency increased from 0.552 Hz/s to 1.447 Hz/s, an increase of about 162.1%.
Recovery also became slower. Settling time increased from 4.18 seconds to 7.66 seconds, while minimum voltage declined from 0.967 p.u. to 0.911 p.u.
The same general pattern appeared during load increases and three-phase fault scenarios, indicating that the stability challenge was not limited to one particular type of disturbance.
GFM Produces Stronger Frequency Recovery
Increasing GFM participation substantially improved system performance, particularly at high renewable penetration.
At 80% renewable penetration, increasing the GFM share from 0% to 100% improved the frequency nadir during generation loss from 48.806 Hz to 49.477 Hz.
The maximum rate of frequency change fell from 1.447 Hz/s to 0.720 Hz/s, representing a reduction of approximately 50.2%. Settling time decreased from 7.66 seconds to 4.87 seconds, a reduction of 36.4%.
The researchers also found that the value of GFM became greater as renewable penetration increased. At 20% renewable penetration, moving from 0% to 100% GFM improved the generation-loss frequency nadir by 0.177 Hz. At 80% renewable penetration, the improvement reached 0.671 Hz.
GFM benefits were also observed during load increases and three-phase faults. At 80% renewable penetration, GFM improved the frequency nadir during a load increase from 49.069 Hz to 49.592 Hz. During the three-phase fault scenario, it increased the nadir from 49.307 Hz to 49.697 Hz.
Virtual Inertia Requires Careful Tuning
The study also found that increasing virtual inertia does not automatically improve every aspect of grid performance.
When virtual inertia was increased from 1 to 6 seconds, the frequency nadir improved from 49.200 Hz to 49.361 Hz, while maximum RoCoF decreased from 1.020 Hz/s to 0.790 Hz/s.
However, settling time increased from 4.86 seconds to 5.80 seconds, or 19.3%. This means higher virtual inertia can slow the initial frequency decline but may also delay the final recovery of the system.
As the authors explain through their system-level analysis, GFM deployment should therefore be coordinated with virtual inertia, damping, frequency droop, current limits, and available power reserves rather than treating higher virtual inertia as universally better.
Implications for Renewable Energy Development
The findings have practical implications for countries and electricity providers seeking to increase renewable-energy capacity without compromising grid reliability.
The results suggest that expanding solar, wind, and other inverter-based generation should be accompanied by appropriate grid-forming capabilities. GFM technology could help maintain frequency and voltage stability as conventional synchronous generation declines.
However, GFM cannot provide unlimited power support. At 80% renewable penetration and 100% GFM participation, peak GFM support reached 10.2% of the system base during generation loss. Delivering such support in a real system requires sufficient energy headroom, which could come from battery energy storage, controlled renewable-power curtailment, or other energy resources.
The authors also emphasize that the results should not yet be interpreted as operational limits. The benchmark does not include several details required for full real-world validation, such as exact renewable-unit locations, fault-clearing times, detailed converter controls, and DC-side energy models.
For policymakers and grid planners, the message is straightforward: renewable-energy expansion and grid-stability planning need to advance together. For the power industry, the findings point toward greater attention to GFM-capable converters, energy storage, and coordinated control strategies.
Author Profiles
Endang Sukarna — Politeknik Negeri Bandung; corresponding author. The article focuses on his work with power-system stability, renewable-energy integration, and grid-forming inverter performance.
Farrah Fauzia — Politeknik Negeri Bandung. Her contribution is associated with the study of GFM performance and renewable-energy integration.
Dwi Feriyanto — Department of Software Engineering, Faculty of Technology and Informatics, Aisyah University. His contribution is associated with the scenario-based analysis presented in the study.
Manovri Yeni — Faculty of Engineering, Universitas Muhammadiyah Aceh. His contribution is associated with the analysis of power-system performance and inverter-based renewable integration.
The source article does not provide the authors' academic degrees or detailed individual fields of expertise. Those details have therefore not been added to avoid introducing information that cannot be verified from the source.
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