A single phase doubly grounded, PV inverter using coupled inductor with integrated magnetics and active power decoupling technique

Transformer-less PV inverters are gaining widespread applications with lower cost, reduced footprint, and improved efficiency. This paper builds on a recently proposed topology with doubly grounded structure that can eliminate the common mode leakage current which is a major challenge in transformer-less PV inverters. An active power decoupling strategy is implemented in the above topology for double line frequency power decoupling, thus achieving high power density and improved reliability by use of film capacitors. A constant input voltage with negligible double line frequency ripple component ensuring high MPPT efficiency is achieved in this topology. Compared to the previously proposed topology, the dc-dc stage and dc-ac stage inductors are coupled with an integrated magnetics design to take advantage of the currents in the two stages to reduce the flux, core loss and the current ripple. A 500 W, 100 kHz single-phase prototype with 200 V DC input and 120 V/60 Hz AC output using SiC MOSFETs has been built to validate the theoretical analysis. The total inductor volume can be reduced by 31%, and the inductor current ripple in the dc-dc stage and dc-ac stage can be reduced by 35% and 50% respectively. The efficiency improves by 0.3% due to savings in the core loss and copper loss compared with topology using discrete inductors.