Design and Implementation of Four-Port Megawatt-Level High-Frequency-Bus Based Power Electronic Transformer

With high penetration of various distributed energy resources and dc loads in modern power system, ac/dc hybrid distributed grid attracts a lot of attention due to its compatibility. Aiming for interface of the ac/dc hybrid distributed grid, a four-port megawatt-level power electronic transformer (PET) is focused on in this article. A novel high-frequency-bus based multiport PET topology is proposed, which is found to have superiorities such as mutual isolation, mutual independence among different ports and fewer power stages, compared with the conventional dc-bus based solution. Design and implementation of the four-port PET prototype is presented in this article. Modular structure is adopted, and similar power cell is used for all the four ports for easy manufacture. The parameter design principle based on the port-equality is proposed to guarantee the suitable operating range of all the ports. The functions of this four-port high-frequency-bus based PET are tested and verified from the cell-level, port-level to the system level with maximum efficiency over 96%, which confirms the practicability of this industrial prototype.