Modified Two Switch Flyback topology with an Active Clamp Converter for solar PV micro-inverter application

Micro-inverters are one of the many solutions to inject PV energy into the grid. They are usually composed of two stages: a first DC-DC stage that allows performing the MPPT (Maximum Power Point Tracking) function, adding galvanic isolation and raising the voltage to ease the operation of a second stage, the solar Grid Tie Inverter. An interesting and attractive proposal for this first stage is the Flyback converter due to simplicity, isolation, and few components, among others. Unfortunately, for power ratings of 400 W and higher, the problems arising from the leakage inductance of the transformer make it unfeasible. A modification of this converter is the so-called Two-Switch Flyback (TSF). By means of extra components, energy normally lost in this leakage inductance is recirculated to the input. However, the design region becomes narrower, making it difficult to be used in some applications like in an MPPT. This work proposes a modification of TSF by incorporating an auxiliary DC-DC converter denoted as Active Clamp Converter (ACC). This modification of the original TSF allows recovering the energy from the leakage inductance and sending it to the output of the converter, thus avoiding energy recirculation. The proposed topology, with the modification introduced, is a novel solution which improves the efficiency compared to the classical TSF stage.