Rapid admittance measurement of power converters using double-PLL grid-following inverters

The increasing use of inverter-based resources (IBRs) in power systems highlights the need for a deep understanding of their stability and dynamics. Traditional analytical models, limited by the black-box nature of IBRs, underscore the importance of frequency-domain methods through measured admittance. Facing challenges in real-world admittance measurement, such as the absence of ideal voltage or current sources, the use of measurement inverters as perturbation sources has emerged as a promising approach, despite drawbacks like reduced system stability and increased measurement time. This article introduces a novel control strategy for measurement inverters, elucidating the impact of abc/dq and dq/abc transformations on admittance measurement. The key advancements are an analysis of the admittance contributions from these transformations and the implementation of double phase-locked loops in the measurement inverters, aimed at improving stability and decreasing measurement duration.