Stability Impact of Hybrid Synchronization Strategy on Virtual-Admittance-Based Grid-Forming Inverters

This paper analyzes the stability impact of the hybrid synchronization control (HSC) strategy on grid-forming inverters, considering different reference-frame realizations of the virtual-admittance-based current control (VA-CC). It is found that with the VA-CC implemented in the synchronous-reference
$(dq)$
frame, the HSC tends to jeopardize the system stability in weak grids. Yet, such adverse effect is avoided when the VA-CC is implemented in the stationary-reference
$(\alpha\beta)$
frame. Further, the HSC can help to dampen the dynamics of inverters in stiff grids when using either
$\alpha\beta$
- or dq-frame VA-CC. Experimental results confirm the theoretical findings.