**5. Conclusions**

A high-efficiency transformerless QZS inverter was proposed for single-phase grid-tied applications. The proposed inverter effectively reduced the leakage current, providing high power efficiency. A bidirectional switch operating with the grid frequency was used, which provided a current path to remove high-frequency components for the common-mode voltage. Switching power losses were also alleviated by reducing the number of switching times for power switches. The operation principle of the proposed inverter was described. A control scheme was suggested for regulating the DC-link voltage and the grid current. A 1.0 kW prototype inverter was designed and tested to evaluate the performance of the proposed inverter. SiC MOSFETs were applied to the proposed inverter to increase the power efficiency. The experimental results showed that the proposed inverter achieved high performance in terms of leakage current reduction and power efficiency improvement.

**Author Contributions:** W.-Y.C. managed the project, and wrote the manuscript. M.-K.Y. performed the experiments, analyzed the data, and edited the manuscript.

**Funding:** This research was supported by the National Research Foundation of Korea (NRF-2016R1D1A3B03932350). It was also supported by research funds from Chonbuk National University in 2018.

**Conflicts of Interest:** The authors declare no potential conflict of interest.
