An improved transformerless grid connected photovoltaic inverter with common mode leakage current elimination

Transformerless PV inverters are most preferred for grid connected photovoltaic (PV) generation system due to higher efficiency and lower cost. However, to meet the safety regulations, the leakage current, which deteriorates the power quality and generates EMI of transformerless PV inverter, have to be addressed carefully. In order to eliminate the leakage current, an improved topology based on H5 topology is proposed in this paper. The operation principle, common mode (CM) characteristics, and the impact of junction capacitance of the switches are analyzed in detail. Three-level output voltage has been achieved in the proposed improved inverter by implementing unipolar SPWM with wide input voltage range. Furthermore, the European Union (EU) efficiency is improved by replacing the IGBTs with MOSFETs. The proposed improved inverter topology has been simulated by MATLAB/Simulink software to validate the accuracy of the theoretical explanations. Finally, a 1kw prototype has been built and tested. Experimental results show 98.2% maximum efficiency and 97.76% EU efficiency on the 1kw prototype circuit with 16 kHz switching frequency.