**7. Conclusions**

A novel bi-directional converter, especially for multi-MW wind generator for o ffshore wind energy conversion applications, was designed. This converter has the ability to handle a wide range of power in MW with thousands of ampere current by adding parallel circuitry of 'n' number of Vienna rectifiers with a single module of three-phase 3L-NPC converter. Moreover, the designed converter has a lower number of power devices, which leads towards cost-e ffectivness, a reduction in switching losses, as well as high power density system as compared to the conventional parallel-connected 3L-NPC converters. A simple hybrid control scheme consists of a VOC for 3L-NPC and current average control technique with the addition of duty ratio feed-forward for Vienna rectifier control to improve the current distortion was also investigated. Equally distributed power in Vienna rectifier and 3L-NPC converter verified the control performance. The proposed converter with a control scheme also verified that the Vienna rectifier has unity power factor (PF) and low THD factor as compared to 3L-NPC. The simulation and experimental results of a deliberated 2-KW system verified the fast dynamic response, good power factor (PF), and current THD less than 5%.

**Author Contributions:** M.L. and G.Y. conceived and designed the study; M.L. preformed experiments and edited the draft with guidance from G.Y and L.Z. L.Z. checked the language and style of the manuscript. T.Z. and A.L. made a contribution to the revisions of manuscript.

**Funding:** This research was supported by the Shanghai Natural Science Foundation (SNSF) under gran<sup>t</sup> 18ZR1418400.

**Acknowledgments:** We thank all the journal editors and the reviewers for their valuable feedback and constructive comments that have contributed to improving this manuscript.

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