This paper is concerned with a type of unidirectional LC DC-DC converter for interconnecting two DC grids with different voltage levels. This unidirectional LC-type DC-DC converter is composed of voltage source converter

uncontrolled rectifiers and LC circuit which is in series connection with them. The topology design of the converter is studied

and the design procedures are presented. A control strategy for the unidirectional LC-type DC-DC converter is also proposed. The designed converter has the ability to retain the fault current near or within the rated values. A 30 MW ±10 kV/±100 kV model is developed on the PSCAD platform to verify the effectiveness of the control strategy during step power orders and favorable DC fault responses. Compared with other DC-DC converters

the unidirectional LC-type DC-DC converter has high stepping ratios

good controllability

low cost and the ability to ride through DC faults. This work is supported by Post-doctoral Science Foundation of China(No. 2016T90690).