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This paper addresses the resonance problem in a parallel-inverter-based grid-connected system. Harmonic interactions between inverters and the grid exhibit various number of complicated characteristics that threatens the system stability and power quality. In this paper, a method of harmonic resonance analysis is proposed to investigate the resonance problem in a multi-inverter grid-connected system based on resonance modal analysis (RMA) and participation factor (PF) calculations. Initially, an impedance-based analytical approach is employed and expanded to an electricity distribution network that is dominated by multiple inverters with LCL filters and proportional resonant controllers. Then, the RMA is introduced to investigate the resonant interactions among inverters and the grid. Specifically, harmonic resonance characteristics are addressed through transfer functions and the proposed method considering variation of inverter number, different inverter combinations, and critical system components. Finally, time domain simulations on the PSCAD/EMTDC platform are presented. The case study results validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]