Design and Experimental Validation of an Independent DC Bus Structure Multiport Power Electronic Transformer

The Independent DC Bus Structure Multiport Power Electronic Transformer (IDBS-MPET) employs a parallel connection of dual active bridge (DAB) converter output ports to directly establish multiple DC ports. This configuration provides convenient conditions for the integration of DC loads such as electric vehicles and distributed generation systems like photovoltaics. However, coordinated control among the multiple ports of the IDBS-MPET is necessary to ensure its safe and stable operation. This paper presents a three-level hardware control architecture for the IDBS-MPET, which includes a central controller to implement closed-loop control algorithms for the front-end cascaded H-bridge (CHB) and the rear-end DAB, a cluster controller to manage the PWM pulses of the CHB and the distribution of phase-shift angles for both the internal and external DABs, and a local controller to drive the power circuit IGBTs and protect the DC voltage. A low-voltage 4-port IDBS-MPET prototype was built in the laboratory, and the effectiveness of the proposed hardware control structure was validated through experiments conducted under three different operating conditions.