A High Voltage Gain Modular Multilevel DC-DC Converter

This Paper presents a new modular multilevel converter (MMC) concept to achieve high ratio DC-DC power conversion purpose. This converter can be deployed in High voltage direct current (HVDC) system, or it can be used as a Solid-state Transformer (SST). The proposed converter is flexible, reliable and it possesses scalability and simplicity. The conversion ratio can be regulated by the phase-shifted control, without any hardware modification. Using the MMC concept, this converter can be implemented with lower voltage rating switching devices instead of much higher voltage rating switches, which is usually unavailable. Two kinds of submodules are outlined for building the MMC. By utilizing inductance distributed on wire/trace and equivalent series inductance (ESL) of the capacitors, no inductors are needed to build the converter. Resonant operation between wire/trace inductance, ESL of capacitors and submodule capacitors assists the converter work under ZCS mode for higher efficiency. The operation principle as well as simulation results of a 20kW converter are presented in this paper.