A new-type modular DC-DC converter is proposed for the demand for high-voltage high-power DC conversion. With a lower switching frequency and smaller power loss

a simple structure without any internal transformer coil

the new converter has a simpler control mode and is easy to extend. It is suitable for the DC power transmission with a higher voltage level and larger transmission capacity. For both unidirectional and bidirectional DC-DC converters designed

a detailed description is made of the converter topology

working principles as well as control strategy. It is shown by simulation results in the PSCAD/EMTDC environment that the new type of DC-DC converter can better realize the function of the DC transformer with ideal DC voltage and current than do its counterparts.