Impedance Scanning Method of Grid-tied Converters under Nonzero Grid Impedance Condition

Abstract

The impedance of three-phase converters is widely used in stability analysis of grid-tied converters system. This paper investigates the frequency coupling effect on impedance scanning of converters in stationary reference frame under nonzero grid impedance condition. In addition, a simple and accurate method of impedance scanning of grid-tied converters is proposed in this paper. The proposed methods injects a single phase perturbation into the Point of Common Coupling (PCC) during two scanning cycles, the self-impedance and accompanying-impedance which are employed to characterize the frequency coupling effect of converter can be acquired in the sequence domain. Simulation results prove that the proposed method is effective, and the measured results can be used as the basis for stability analysis.