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Cross-Forming Control and Fault Current Limiting for Grid-Forming Inverters | IEEE Journals & Magazine | IEEE Xplore

Cross-Forming Control and Fault Current Limiting for Grid-Forming Inverters


Abstract:

This article proposes a “cross-forming” control concept for grid-forming inverters operating against grid faults. Cross-forming refers to voltage angle forming and curren...Show More

Abstract:

This article proposes a “cross-forming” control concept for grid-forming inverters operating against grid faults. Cross-forming refers to voltage angle forming and current magnitude forming. It differs from classical grid-forming and grid-following paradigms that feature voltage magnitude-and-angle forming and voltage magnitude-and-angle following (or current magnitude-and-angle forming), respectively. The cross-forming concept addresses the need for inverters to remain grid-forming (particularly voltage angle forming, as required by grid codes) while managing fault current limitation. Simple and feasible cross-forming control implementations are proposed, enabling inverters to quickly limit fault currents to a prescribed level while preserving voltage angle forming for grid-forming synchronization and providing dynamic ancillary services, during symmetrical or asymmetrical fault ride-through. Moreover, the cross-forming control yields an equivalent system featuring a constant virtual impedance and a “normal form” representation, allowing for the extension of previously established transient stability results to include scenarios involving current saturation. Simulations and experiments validate the efficacy of the proposed cross-forming control implementations.
Published in: IEEE Transactions on Power Electronics ( Volume: 40, Issue: 3, March 2025)
Page(s): 3980 - 4007
Date of Publication: 18 November 2024

ISSN Information:


I. Introduction

Grid-forming inverters play a crucial role in future power systems in autonomously regulating grid frequency and voltage. While a grid-forming inverter operates like a voltage source, limiting its current during grid disturbances is critical to prevent potential overcurrent damage. Moreover, grid-forming inverters should sustain transient stability during grid faults, ensuring synchronization while transitioning from one operating state to another. Transient stability is crucial for successful fault ride-through (FRT) and ancillary services during FRT, such as fault current injection and phase jump power provision. These are requirements outlined in recent grid-forming specifications, e.g., the Great Britain, Australian, and European grid codes [1], [2], [3]; see a survey in [4] and [5]. To satisfy these requirements, grid-forming inverters should maintain grid-forming synchronization and provide FRT ancillary services as continuously as possible, even when the current reaches the limit [1], [2], [3], [4], [5]. These requirements involve technical challenges in limiting fault current, maintaining transient stability (synchronization), and providing FRT ancillary services simultaneously [6], [7].

References

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