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