Design of a three-phase cascaded Power Electronic Transformer based on energy Internet

This paper presents a three-phase cascaded Power Electronic Transformer (PET) based on energy internet. The proposed PET can allow direct connection with the high voltage and provide a stable DC interface for Distribute Generation (DG) and load. It consists of three Cascaded H-Bridge (CHB) converters with star configuration and output-parallel isolated DC/DC converters with intermediate frequency transformer. The two parts are designed separately in closed loop. Specifically, a simple control method is proposed to balance individual inphase and interphase DC voltages of three-phase CHB converter. The control method based on a phase-shifted pulse width modulation scheme can be extended to different voltage levels. The validity and performance of the proposed topology and the control strategy is verified by simulation.