Semi-Z-source inverter topology for grid-connected photovoltaic system

Transformer-less inverters are necessary parts for grid-connected renewable energy resources. Owing to its cost effectiveness, downsize and less weight, great attention has been paid to these inverters development. With these aforementioned advantages, these inverters have limitations like the flow of leakage current through photovoltaic arrays, high total harmonic distortion (THD) at inverter´s output and DC current injection to the grid. This study presents coupled inductor-based single-phase transformer-less semi-Z-source inverter topology to lessen those limitations. Since the DC input and AC output voltage share a common ground, the presented inverter system is categorised under doubly grounded topologies. For the purpose of handling, the non-linearity of the voltage gain of semi-Z-source inverter, a non-linear sinusoidal pulse-width modulation technique has been employed. The prototype of the suggested inverter has been constructed. The performance and compatibility of modulation technique are verified under different loading conditions. The feasibility of the configuration is ensured based on the mitigated common-mode leakage current, the substantially lower THD as well as DC current injected to the grid. Moreover, the presence of coupled inductor significantly contributes in reducing input current ripple, installation area of the inverter and enhancing the efficiency. Finally, this topology exhibits appreciable performance to operate synchronously and transfer power to the grid.