This paper has discussed the modeling, control, and tests of the VSG inverter to fully mimic the SG in both normal operation and grid faults. The 6th-order VSG model is adopted, and the transformer voltage items dψd/dt and dψq/dt are considered in the model for fault transients and unbalanced fault conditions. Simulation and experimental tests are conducted under three-phase fault, phase-to-phase fault, and single-phase fault with different fault resistances. The results show that the VSG inverter with the 6th-order can mimic the SG well during grid faults. This work will facilitate the penetration of IBR in the grid without introducing many grid issues.
