A Novel SEPIC-Ćuk-Based High Gain Solar PV Microinverter for Grid Integration

A SEPIC-Ćuk-based transformerless micro inverter capable of interfacing a 35 V, 250 W solar PV module to a single-phase 220–230 V ac grid is proposed in this article. The circuit employs only one high-frequency switch and four line-frequency switches thereby reducing the switching losses. This also enhances the overall reliability of the system. The circuit is made to operate in discontinuous conduction mode (DCM) under all possible operating conditions to achieve high gain and at the same time ensure negligible turn
on
loss for the high-frequency switch. The direct connection existing between the PV neutral and the utility ground makes the magnitude of the leakage current to be zero. In order to reduce the size of the capacitor across the PV module, an active power decoupling circuit is employed. Hence, this capacitor can be realized by a thin film capacitor instead of an electrolytic capacitor thereby improving the reliability of the system. Detailed analysis of the proposed microinverter is carried out. The effectiveness of the proposed scheme is verified by performing detailed simulation studies. A 250 W laboratory prototype of the inverter is fabricated, and detailed experimental studies are carried out to confirm the viability of the proposed scheme.