14 September 2024 | Nathan Baeckeland, Member, IEEE, Debjyoti Chatterjee, Graduate Student Member, IEEE, Minghui Lu, Member, IEEE, Brian Johnson, Senior Member, IEEE, and Gab-Su Seo, Senior Member, IEEE
This article provides a comprehensive review of current-limiting techniques for grid-forming (GFM) inverters, which are increasingly used to facilitate the integration of inverter-based resources into power grids. The authors highlight the significant differences between GFM inverters and conventional synchronous machines in terms of overcurrent characteristics, emphasizing the need for an in-depth characterization of current-limiting strategies. The article discusses the impact of current-limiting controls on inverter behavior during and after off-nominal system disturbances, including device-level stability, transient system stability, power system protection, and fault recovery.
The review covers various current-limiting methods, including direct and indirect approaches, and hybrid methods that combine elements of both. Direct methods, such as current-reference saturation limiting and switch-level current limiting, are designed to quickly and accurately curtail the output current. Indirect methods, such as power set point modulation, virtual impedance (VI) current limiting, and voltage-based current limiting, modulate the control signals to achieve current limitation. Hybrid methods, which combine direct and indirect techniques, aim to leverage the strengths of both to enhance the dynamic behavior of GFM inverters during faults.
The article also addresses the challenges and trade-offs associated with each current-limiting method, such as the impact on transient stability, small-signal stability, voltage-source behavior, post-fault recovery, and the response to asymmetrical faults. It discusses the importance of considering these aspects in the design of current limiters to ensure optimal performance and reliability.
Finally, the article outlines the latest standards and trends in GFM current-limiting, emphasizing the need for tailored standards and future research directions. The authors conclude by highlighting the potential of current-limiting techniques to enhance the reliability and stability of power systems, particularly in the context of transitioning to sustainable power grids.This article provides a comprehensive review of current-limiting techniques for grid-forming (GFM) inverters, which are increasingly used to facilitate the integration of inverter-based resources into power grids. The authors highlight the significant differences between GFM inverters and conventional synchronous machines in terms of overcurrent characteristics, emphasizing the need for an in-depth characterization of current-limiting strategies. The article discusses the impact of current-limiting controls on inverter behavior during and after off-nominal system disturbances, including device-level stability, transient system stability, power system protection, and fault recovery.
The review covers various current-limiting methods, including direct and indirect approaches, and hybrid methods that combine elements of both. Direct methods, such as current-reference saturation limiting and switch-level current limiting, are designed to quickly and accurately curtail the output current. Indirect methods, such as power set point modulation, virtual impedance (VI) current limiting, and voltage-based current limiting, modulate the control signals to achieve current limitation. Hybrid methods, which combine direct and indirect techniques, aim to leverage the strengths of both to enhance the dynamic behavior of GFM inverters during faults.
The article also addresses the challenges and trade-offs associated with each current-limiting method, such as the impact on transient stability, small-signal stability, voltage-source behavior, post-fault recovery, and the response to asymmetrical faults. It discusses the importance of considering these aspects in the design of current limiters to ensure optimal performance and reliability.
Finally, the article outlines the latest standards and trends in GFM current-limiting, emphasizing the need for tailored standards and future research directions. The authors conclude by highlighting the potential of current-limiting techniques to enhance the reliability and stability of power systems, particularly in the context of transitioning to sustainable power grids.