A Three-port PSFB/DAB-MMC PET with Reliability Under LVDC Disturbance

DC distribution system has received more and more attention with the rapid development in the past few decades. As the core devices of the DC distribution system, power electronic transformers (PETs) occupy a large proportion of construction cost. For the cost reduction for construction and protection, two types of three-port modular multilevel convertor (MMC) have been proposed in recent years, which are respectively based on dual active bridge converters (DABs) and phase shift full bridge converters (PSFBs). The PETs based on DABs provide high reliability but high cost as well. The PETs based on PSFBs bring a large reduction on construction cost but shows low reliability under the disturbance in the low voltage DC (LVDC) systems. In this paper, a novel PSFB/DAB-MMC topology is proposed with the combination of the above two PETs. The proposed PSFB/DAB-MMC decreases the construction cost with enough reliability under severe disturbance in the LVDC system. A double-modulation-freedom control strategy is proposed for the compatibility of two different types of submodules. The simulation results in MATLAB/Simulink verify the feasibility and the reliability of the proposed topology.