Sub-module photovoltaic microinverter with cascaded push-pull and unfolding H-bridge inverter

In photovoltaic (PV) systems, the most distributed maximum power point tracking systems leads to better energy yield since they are less subject to partial shading. For this, sub­modular PV microinverters have been developed. Those systems consider the PV panel without by-pass diodes, and realize MPPT at a sub-module level. Those sub-module microinverters have shown their interest, especially under long term non-uniform conditions as can results because of dust or snow on the panel. For the classical microinverter, one interesting power conversion structure is the pseudo DC-link inverter consisting in a DC-DC converter realizing the MPPT and controlling a rectified sinusoidal current, followed by an unfolding inverter. Such solution has in particular the advantage of not requiring the weak DC link capacitor that, generally, limits the life expectancy of the microinverter. In this paper, a sub-module PV microinverter consisting in three sub-module push-pull converters connected in series and followed by a H-bridge unfolding inverter is proposed. A dedicated control scheme is also provided with special attention on unbalanced operations. Simulation results and comparison with the classical interleaved flyback pseudo DC-link inverter are provided to evaluate the performances of the proposed sub-module PV microinverter.