Decoupling Capacitor Selection in DCM Flyback PV Microinverters Considering Harmonic Distortion

Electrolytic capacitors as a decoupling reservoir restrict the lifetime of photovoltaic (PV) microinverters. This has led to the development of several improved decoupling circuits that can reduce the capacitor value to allow the use of nonelectrolytic types. In this paper, the minimum decoupling capacitor value for the proper operation of discontinuous conduction mode flyback PV microinverters is analyzed by taking into account the total harmonic distortion (THD) and PV power utilization ratio. The results presented show that the decoupling capacitor value influences the THD more than PV power utilization. A decoupling capacitor selection method for single-stage and two-stage flyback inverters is proposed. Experimental results obtained on an 80-W test bench are presented.