High Efficiency Transformerless MOSFET Inverter for Grid-tied Photovoltaic System

This paper proposes a new high efficiency single phase transformer-less grid-tied photovoltaic (PV) inverter by using super-junction MOSFETs as main power switches. No reverse recovery issues are required for the main power switches and the blocking voltages across the switches are half of the DC input voltage in the proposed topology. Therefore, the super-junction MOSFETs have been used to improve the efficiency. Two additional switches with the conventional full H-bridge topology, make sure the disconnection of PV module from the grid at the freewheeling mode. As a result, the high frequency common mode (CM) voltage which leads leakage current is minimized. PWM dead time is not necessary for the proposed topology which reduces the distortion of the AC output current. The efficiency at light load is increased by using MOSFET as main power switches which increases the European Union (EU) efficiency of the proposed topology. The proposed inverter can also operate with high frequency by retaining high efficiency which enables reduced cooling system. The total semiconductor device losses for the proposed topology and several existing topologies are calculated and compared. Finally, the proposed new topology is simulated by MATLAB/Simulink software to validate the accuracy of the theoretical explanation. It is being manufactured to verify the experimental results.