Enabling Grid-Forming Control with Fault Ride-Through in Unbalanced Distribution Networks

Journal Article · Tue Jan 06 00:00:00 EST 2026 · IEEE Transactions on Smart Grid

DOI:https://doi.org/10.1109/TSG.2026.3651333· OSTI ID:3024583

Ojo, Yemi ^[1]; Nag, Soumyadeep ^[1]; Olowu, Temitayo Olayemi ^[1]

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1. Idaho National Laboratory

Distribution networks are often unbalanced, causing oscillatory responses in inverter control designed for balanced conditions. To address this problem, this paper proposes a novel time-domain transformation appropriate for inverter control and enables the decomposition of three-phase unbalanced signals into constant positive and negative components. Relations useful for calculating unbalanced active and reactive power are derived from first principle, providing insight into vector products of unbalanced three-phase signals. Furthermore, a grid-forming control effective under unbalanced conditions is developed, which delivers superior performance while meeting UNIFI1 specifications for grid-forming control under unbalanced conditions. specifications applicable to category 4 inverter-based resource, like setting and regulating frequency/voltage, providing voltage support, sharing active power, injecting negative sequence current, and riding through faults. A current limiter is proposed for safe fault ride-through and integrates with the grid-forming control featuring frequency/voltage droop controllers and current and voltage control loops. The transformation of interconnected inverters is formulated and stability of the proposed control analyzed to support robust parameter selections. The effectiveness of the proposed transformation and grid-forming control is demonstrated through analytical results and real-time simulation of a IEEE 123 distribution network on the Real-Time Digital Simulator. Comparison with existing methods shows that the proposed strategy satisfies the UNIFI specifications with a much better performance.

• Research Organization: Idaho National Laboratory (INL), Idaho Falls, ID (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE)
• Grant/Contract Number: AC07-05ID14517
• OSTI ID: 3024583
• Report Number(s): INL/JOU-25-85137
• Journal Information: IEEE Transactions on Smart Grid, Journal Name: IEEE Transactions on Smart Grid Journal Issue: 0 Vol. 0
• Country of Publication: United States
• Language: English

Related Subjects

24 - POWER TRANSMISSION AND DISTRIBUTION
Distribution networks
grid-forming control
three-phase inverters
unbalanced three-phase signals