Auto-Identification Method of the “Trouble Maker(s)” for Internal Instability in Multi-paralleled Inverters System

The instability of power systems comprising multiple LCL-filtered grid-connected DC/AC inverters connected in parallel, can be caused by any individual inverter due to mutual coupling through the grid impedance. For the stability analysis of a multi-paralleled DC/AC inverters system, an effective technique capable to diagnose which particular inverter (i.e. “trouble maker”) causes instability to the overall system has not yet been developed. In this paper, a novel auto-identification method is proposed to detect the “trouble maker(s)” of instability in a multi-paralleled inverters system, based on the comparison between the Root Mean Square (RMS) value of harmonic voltage at the point of common coupling (PCC) and the harmonic voltages across the filters capacitors. The theoretical analysis of the proposed identification method is presented in details in this paper. Also, simulation and experimental results are provided for verification of the effectiveness of the proposed technique.