  In this work, we investigate grid-forming (GFM) control for dc/ac voltage
source converters (VSC) under unbalanced system conditions and unbalanced
faults. To fully leverage the degrees of freedom of VSCs, we introduce the
concept of generalized three-phase GFM control that combines individual GFM
controls for every phase with a phase balancing feedback. The proposed control
allows trading off voltage and power unbalance under unbalanced conditions,
enables current limiting for each phase during unbalanced faults, and reduces
to positive sequence GFM droop control in balanced systems. High-fidelity
simulations are used to illustrate the properties of the control.
