Improved Fault Resilience of GFM-GFL Converters in Ultra-Weak Grids Using Active Disturbance Rejection Control and Virtual Inertia Control

Monigaa Nagaboopathy (), Kumudini Devi Raguru Pandu, Ashmitha Selvaraj and Anbuselvi Shanmugam Velu
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Monigaa Nagaboopathy: Department of Electrical and Electronics Engineering, CEG Campus, Anna University, Chennai 600025, India
Kumudini Devi Raguru Pandu: Department of Electrical and Electronics Engineering, CEG Campus, Anna University, Chennai 600025, India
Ashmitha Selvaraj: Department of Electrical and Electronics Engineering, CEG Campus, Anna University, Chennai 600025, India
Anbuselvi Shanmugam Velu: Department of Electrical and Electronics Engineering, CEG Campus, Anna University, Chennai 600025, India

Sustainability, 2025, vol. 17, issue 14, 1-32

Abstract: Enhancing the resilience of renewable energy systems in ultra-weak grids is crucial for promoting sustainable energy adoption and ensuring a reliable power supply during disturbances. Ultra-weak grids characterized by a very low Short-Circuit Ratio, less than 2, and high grid impedance significantly impair voltage and frequency stability, imposing challenging conditions for Inverter-Based Resources. To address these challenges, this paper considers a 110 KVA, three-phase, two-level Voltage Source Converter, interfacing a 700 V DC link to a 415 V AC ultra-weak grid. X/R = 1 is controlled using Sinusoidal Pulse Width Modulation, where the Grid-Connected Converter operates in Grid-Forming Mode to maintain voltage and frequency stability under a steady state. During symmetrical and asymmetrical faults, the converter transitions to Grid-Following mode with current control to safely limit fault currents and protect the system integrity. After fault clearance, the system seamlessly reverts to Grid-Forming Mode to resume voltage regulation. This paper proposes an improved control strategy that integrates voltage feedforward reactive power support and virtual capacitor-based virtual inertia using Active Disturbance Rejection Control, a robust, model-independent controller, which rapidly rejects disturbances by regulating d and q-axes currents. To test the practicality of the proposed system, real-time implementation is carried out using the OPAL-RT OP4610 platform, and the results are experimentally validated. The results demonstrate improved fault current limitation and enhanced DC link voltage stability compared to a conventional PI controller, validating the system’s robust Fault Ride-Through performance under ultra-weak grid conditions.

Keywords: grid-following converter (GFL); grid-forming converter (GFM); fault ride-through (FRT); grid-connected converter (GCC); short-circuit ratio (SCR); virtual capacitor-based virtual inertia control (VCVI); active disturbance rejection control (ADRC) (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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