This paper proposes an improved full-bridge three-level (IFBTL) DC/DC converter for integrating wind turbines into a DC grid. The converter inserts a passive filter to reduce transformer voltage stress. A modulation strategy with two operation modes is proposed to control the converter. A voltage balancing control strategy is also presented. Experimental results from a small-scale prototype verify the theoretical analysis.

1. CONTROL OF IMPROVED FULL-BRIDGE THREE-LEVEL DC/DC
CONVERTER FOR WIND TURBINES IN A DC GRID
ABSTRACT:
This paper presents an improved full-bridge three-level (IFBTL) dc/dc converter for a wind turbine
in a dc grid by inserting a passive filter into the dc/dc converter to improve the performance of the converter.
The passive filter can effectively reduce the voltage stress of the medium frequency transformer in the
IFBTL dc/dc converter. A modulation strategy, including two operation modes, is proposed for the IFBTL
dc/dc converter. Then, a voltage balancing control strategy is proposed for the IFBTL dc/dc converter.
Furthermore, the control of the wind turbine based on the IFBTL dc/dc converter in a dc-grid system is
presented. Finally, a small-scale IFBTL dc/dc converter prototype was built and tested in the laboratory, and
the results verify the theoretical analysis.