Evaluation of two-stage soft-switched flyback micro-inverter for photovoltaic applications

The research on the micro inverters for photovoltaic (PV) applications has been increased in recent years due to its advantages of minimization of module mismatch losses, the elimination of serial diode losses, and suitability for mass production etc. However, the micro-inverters suffer from the low voltage at the input PV terminals that causes high conduction loss and requires large electrolytic capacitors for decoupling purposes. The electrolytic capacitors have relatively low lifetime in comparison with the PV modules, and restricts the micro-inverter service life significantly. Moreover, the high conduction loss decreases the micro-inverters conversion efficiency considerably. In order to mitigate these drawbacks, two stage micro-inverters are generally proposed. In this study, a 200 W two stage soft switched flyback micro-inverter is designed for highest efficiency, and compared with the conventional single stage flyback micro-inverter. By using two-stage soft-switched flyback micro-inverter, the decoupling capacitor value is decreased by 10 times, and maximum efficiency is increased by 13.7%. The experimental results are also presented.