Modular Unfolding Multi-Source High-voltage Gain Inverter for Renewable-Powered Nano Grid Systems

Several challenges encountered in the usage of Nano grids which have become a huge interest for 21st-century households with high penetration of renewables. A single PV or fuel cell suffers from low voltage output ranging from 16-50V which constrains the selection of inverter. Thus, a modular multi-input gain unfolding inverter is proposed to address these challenges. The inverter can reach 240V AC 50Hz output with only one active switching device per module operating at high switching frequency mode to reduce the switching loss and reduce passive components design. A high-grade boosted AC output is realized due to the modular structure of buck-boost submodules connected in series followed by a highly efficient line frequency inverter. The buck-boost submodules have a 360°/n phase difference which further reduces the passive components size. Due to the unfolding inverter operation, the bulky DC link is replaced with a compact efficient AC link. A high-power conversion efficiency of 97% and 96% is realized with two and four submodules based modular multi-input gain unfolding inverter compared to classical two stage boost and buck boost-based inverters. The topology is analyzed and simulated to validate the approach. An experimental prototype is developed and tested at 2 kW, resulting in a total harmonic voltage of 2.4%.