Design of Transformerless Single Stage Double Switch Step Down PLL Derived Inverter using Single Phase Grid Connected PV Module with MPP Tracking

Abstract

Here we propose a single stage double switch (SSDS) converter for single phase grid connected photo voltaic inverter step-down module, the structure is designed and modelled to a highly reliable step-down buck DC-DC converter and robust from the input derived from the PV module. The proposed PV module uses perturb and observe algorithm reference voltage to gain the maximum power in different changing climatic conditions. The grid is designed for 110 V/50 Hz, since it’s a low frequency, the utilization of heavy and expensive transformer is avoided, In a grid connected systems usually transformer is employed in the power conversion stage to provide sudden isolation between the PV system and the grid, and also ensures that no continuous current is injected into the grid by avoiding leakage currents between the PV module and the ground. As a choice to the grid connected module with line transformer, a transformer less inverter topology is discussed, to avoid the leakage currents possibly occurring due to the capacitance between the PV array and ground, an inverter topology with PLL is proposed to avoid common mode voltage and the increase in electromagnetic emissions. This paper provides a highly efficient transformer less photovoltaic grid topology with reduced switches and has been validated by simulation.