A grid-connected asymmetrical cascaded H-bridge 81 level inverter with single PV unit and voltage splitting multi winding isolation transformer in marine applications

Abstract

In this paper, an asymmetrical cascaded H-bridge 81 level inverter powered by a single photo voltaic (PV) unit is presented. The PV unit drives an interleaved soft switched boost converter that drives a simple three level inverter, which in turn drives a multiple secondary winding transformer. The AC output of the four isolated secondary windings of the transformer is rectified and filtered to deliver four isolated DC voltages in the ratio 1:3:9:27. The system incorporates maximum power point tracking at the front end boost DC-DC converter level. Overall reduced THD is achieved by strategically spacing on the time axis, for each AC cycle, the discrete voltage levels of the 81 level inverter. The mathematical formulation, the results of simulation in the MATLAB/SIMULINK environment and the results of experimental verifications are provided.