Enhanced Q-axis Voltage Integral Damping Control for Fast
PLL-Synchronized Inverters in Weak Grids
Abstract
The phase-locked loop (PLL) is a commonly used synchronization control
method for grid-tied inverters. The PLL-synchronized inverters tend to
have poor stability robustness with weak grid interconnections,
especially when the PLL is designed with a high control bandwidth. To
tackle this challenge, this paper proposes an enhanced q-axis voltage
integral damping (Q-VID) control, which not only stabilizes
PLL-synchronized inverters in weak grids but also lifts the restriction
on PLL bandwidth. This superior feature enables inverters to operate
stably in ultraweak grids and with a superior transient response.
Experimental tests confirm the performance of the method with 400-Hz PLL
bandwidth under a short circuit ratio of 1.28 of the grids.