Hardware implementation of grid connected transformer-less semi-Z-source inverter topology to mitigate common mode leakage current and THD

Transformer-less inverters are necessary parts for grid-connected renewable energy resources (RERs). Due to its cost effectiveness, downsize and less weight, great attention has been paid to these inverters development. However, these inverters have limitations like the flow of leakage current through PV arrays, high total harmonic distortion (THD) at inverter´s output and DC current injection to the grid. This paper presents coupled inductor based single-phase transformerless semi-Z-source inverter topology to lessen those limitations. For the purpose of handling the nonlinearity of the voltage gain of semi Z-source inverter, a nonlinear sinusoidal pulse width modulation (SPWM) technique has been employed. A laboratory prototype of the proposed inverter has been constructed. The feasibility of the configuration is ensured based on the mitigated common mode leakage current as well as the substantially lower THD at inverter´s output voltage.