A Novel Method to Identify the "Trouble Maker" of Internal Instability in Multi-paralleled Inverters System

Instability in multi-paralleled LCL-filtered grid-connected inverters system always presents that each inverter is unstable due to the coupling of grid impedance. During stability analysis of multi-paralleled inverters system, which inverter or inverters ("trouble maker or makers") contributes or contribute instability to whole system is rarely studied. In this paper, a novel identification method is proposed to exactly judge the "trouble maker or makers" of instability in a multi-paralleled inverters system, based on the comparison result between the root mean square (RMS) value of harmonic voltage in the common coupling point (PCC) and the one across the filter capacitor. The simulation and experimental results are provided for verification.