Admittance Identification of Grid-Forming Inverters Using Time and Frequency-Domain Techniques

Intriago, Andres, Paspatis, Alexandros, Liberati, Francesco and Konstantinou, Charalambos (2025) Admittance Identification of Grid-Forming Inverters Using Time and Frequency-Domain Techniques. In: 2025 IEEE Kiel PowerTech. Presented at 2025 IEEE Kiel PowerTech, 29 June 2025 - 03 July 2025, Kiel, Germany.

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Abstract

The increasing integration of inverter-based resources (IBRs) into the power grid introduces new challenges, requiring detailed electromagnetic transient (EMT) studies to analyze system interactions. Despite these needs, access to the internal firmware of power electronic devices remains restricted due to stringent nondisclosure agreements enforced by manufacturers. To address this, we explore three system identification techniques: sweep frequency response analysis (SFRA), step excitation method (SEM), and eigensystem realization algorithm (ERA). SFRA employs sinusoidal signals of varying frequencies to measure the system’s frequency response, while SEM and ERA utilize step functions to derive time-domain responses and transform them into Laplace-domain transfer functions. All three approaches are shown to provide consistent results in identifying the dq admittance of grid-forming inverters (GFM) over a frequency range of 1 Hz to 100 Hz.