Modeling and Comparisons of Aggregated Flyback Microinverters in Aspect of Harmonic Resonances With the Grid

In this paper, performances on two kinds of aggregated flyback microinverters are compared in aspect of harmonic resonances, which are controlled by current feedback control and peak current control. Based on the Norton models of flyback microinverters obtained by a small-signal modeling approach, potential harmonic resonances with the grid are analyzed. Following that, an impedance-based stability criterion is proposed, where the resonance frequency can be calculated and predicted based on the derived Norton models and the system admittance matrix of aggregated microinverters. After comprehensive analysis and comparisons, it is found that the peak-current-control-based flyback microinverters has better performance on damping the harmonic resonances than the current feedback controlled one. Simulations and experiments are carried out for verifying the effectiveness of the presented models and the correctness of the analysis results.