Comprehensive DQ impedance modeling of AC power-electronics-based power systems with frequency-dependent transmission lines

This paper introduces a time-frequency analytic method for the exact identification of wideband DQ impedance models oriented to harmonic stability of converter-driven systems with transmission line models with distributed and frequency-dependent parameters. Wideband models are of great importance in the analysis of harmonic stability over a broad range of frequencies. The transmission line is a crucial component in this regard, but it is not straightforward to incorporate it into the impedance model of AC power-electronicsbased power systems. This has led to the use of lumped parameter models or models based on rational approximations. This article proposes a method to include this important element to the impedance model directly from its frequency domain model. Salient features of the proposed modeling approach include the frequency telegrapher's equations with distributed and frequency-dependent parameters, exact delay models of PWM, control implementations of power electronics, and an exact steady-state computation using a balance method based on a hybrid time-frequency approach. The proposal avoids time-domain simulations, rational approximations, or the fast Fourier transform. A converter-driven system with transmission lines is used to validate the proposal and the results of the frequency scanning method conducted in OPAL-RT (ARTEMiS/EMTP-RV) and PSCAD/EMTDC support the effectiveness, speed, and accuracy.