MMDTC-based power electronic transformer and modulation method thereof

The invention discloses an MMDTC-based power electronic transformer and a modulation method thereof, and the power electronic transformer comprises a T-shaped structure, a modular multi-level DC chain module and a dual-active bridge module, and forms a low-voltage DC port and a medium-voltage DC port. Wherein the T-shaped structure is formed by an A-phase input end, a B-phase input end, a C-phase input end and a controllable switch module; the modularized multi-level direct current chain module is formed by connecting an upper bridge arm and a lower bridge arm in series, and each bridge arm is formed by cascading a plurality of sub-modules; the output sides of all the DAB units in the dual-active bridge module are gathered to a low-voltage direct-current port in a parallel connection mode, and a medium-voltage direct-current port is connected with a plurality of DAB units in a series input and parallel output mode in the dual-active bridge module. According to the power electronic transformer and the modulati