Stationary frame sequence decomposed Grid-forming (GFM) control, with power regulation loops and virtual admittance based reference generation for vector current controller, enables flexible and explicit control over fault transient behavior while retaining GFM nature under both balanced and unbalanced grid fault events. For such systems, one of the positive- and negative-sequence symmetrical components appear as time-varying in a synchronous reference frame aligned with the other and hence conventional modelling methods fail due to time-varying quasi-static steady-state. In this work, a dynamic phasor model is developed which facilitates linear time-invariant representation enabling small-signal analysis using frequency domain techniques. This work particularly considers the effect of the synchronizing control, sequence component extraction (SCE) and dual sequence virtual admittance. The modeling and analysis results are supported by simulations and preliminary laboratory experiments.
