Towards a new dynamic phasor theory for modeling IBG penetrated power grids

Fast dynamics of Inverter-Based Generators (IBGs) on the study of transient stability of power systems lead to violations of assumptions commonly employed to justify traditional phasorial RMS models. Short-Time-Fourier Transform (STFT) has been applied in the literature to overcome this issue by representing nonstationary signals in terms of its harmonics as dynamic phasors, maintaining the notion of angles and magnitudes similarly to the traditional phasorial models. Nevertheless, the STFT framework used to represent amplitude and frequency varying sinusoids does not accurately model transient phenomena in power systems due to inherent approximations it entails. Further, STFT dynamic phasors do not have a clear counterpart to complex power, hindering stability studies where customary power formulas are used. This paper presents a novel dynamic phasors theoretical framework able to model nonstationary signals without approximations and offers a theory of nonstationary power. An inverter system attached to an infinite bus is modelled using the proposed framework, yielding a phasorial differential system and simulated under fault, and the time signals reconstructed from the results.