Three Phase Grid Connected Transformer less Inverter for Photovoltaic with PMSM drive

摘要

Three-phase transformer less inverter is widely used in low-power photovoltaic (PV) grid-connected systems due to its small size, high efficiency and low cost. When no transformer is used in a grid connected photovoltaic (PV) system, a galvanic connection between the grid and PV array exists. In these conditions, dangerous leakage currents (common-mode currents) can appear through the stray capacitance between the PV array and the ground. The former, in order to create a galvanic isolation between the input and the output include a transformer (mandatory in some countries) that limits the whole system performances in terms of efficiency, weight, size and cost. On the contrary, transformerless inverters do not present any isolation and are characterized by little size, lower cost and higher efficiency (more than 2% higher). Nevertheless, the lack of transformers leads to leakage currents that can be harmful to the human body, as well as for the whole conversion system integrity. In order to minimize the ground leakage current and improve the efficiency of the converter system, transformerless PV inverters utilizing unipolar PWM control. In this paper it presents a high-reliability three-phase transformer less grid-connected inverter that operate super junction MOSFETs to accomplish high efficiency for photovoltaic applications. In this paper single phase transformer less inverter with PMSM drive and three phase transformer less inverter.