Rapid Admittance Measurement of Power Converters Using Double-PLL Grid-following Inverters

As power systems undergo a transformation with increasing inverter-based resources (IBRs), understanding the stability and dynamics of IBR-dominated systems becomes imperative. Though analytical models offer insights into these changes, intellectual property constraints introduce a challenge due to the black-box nature of IBRs, highlighting the importance of frequency-domain-based methods using IBRs’ measured admittance. While simulation environments provide ease in impedance measurement, real-world implementation faces challenges due to the absence of ideal voltage or current sources. This has prompted the use of varied devices, such as power amplifiers and frequency response analyzers, for perturbation generation and injection. Notably, utilizing another measurement inverter as the perturbation source offers a promising approach, despite its limitations such as degrading system stability and prolonging the measurement time. This article introduces an innovative control strategy for the measurement inverter, detailing the effects of abc/dq and dq/abc transformations on the measured admittance. The groundbreaking contributions are the revelations about the admittance contributions of these transformations and the introduction of double phase-locked loops, optimizing both system stability and measurement time.