Stability identification for grid-connected inverters with LCL filters considering grid-voltage feedforward regulator

This paper identifies stable resonance frequency range for grid-connected inverter with Grid-Voltage Feedforward Regulator (GVFR). Beginning with the current loop stability analysis without GVFR, system poles distribution is analytically studied in z-domain, the critical frequency is therefore calculated as well as the control gain limit. Then, this paper reveals the GVFR would change the system stability in the weak power system, two frequency boundaries and three typical resonance frequency ranges are identified and compared. System poles distribution shows that GVFR can offer damping effects when resonance frequency is below ωs/3, in contrast, over which GVFR will destabilize the system. The theoretical analysis is validated by experimental tests based on a laboratory-scale prototype.