An Improved Transformerless Photovoltaic Grid-Connected Soft-Switching Inverter

This paper proposes an improved transformerless photovoltaic grid-connected soft-switching inverter and its modulation strategy. The improved topology is based on the HERIC topology aimed at the problems that the high leakage current of transformerless photovoltaic grid-connected inverter and the high electrical stress of power switches in it. The improved transformerless photovoltaic grid-connected soft-switching inverter can guarantee the constant common mode voltage in every switching cycle and reduce the leakage current. The main switches are switching under zero-current turn-on and turn-off conditions. It can still realize the soft-switching while the output current is small. Meanwhile, its power stress is low under the novel modulation strategy. The auxiliary switches are also soft-switching. This paper analyzes the operation principle of the improved soft-switching inverter in detail. The common mode voltage is discussed. Finally, the improved topology is simulated by MATLAB/Simulink software to validate the accuracy of the theoretical analysis.