Partial Unfolding Scheme for Grid Feeding Transformerless PV Inverter

Transformerless photovoltaic (PV) inverters are popularly used for grid feeding systems owing to their high efficiency, low weight and compact size. These inverters are expected to have high conversion efficiency and low earth leakage current over wide input voltage range. This paper proposes a method to improve the conversion efficiency, when the PV array maximum power point voltage becomes less than the grid peak voltage. This scheme reduces effective switching frequency of inverter, which results in less switching and recovery losses. The detailed operation of the proposed modulation and control scheme is explained. Estimated efficiency is also compared with the state of the art. In order to validate the operation, simulation studies are carried out using Matlab/Simulink environment and results are included.