This paper studies the operation

analysis and experiments of multilevel high frequency link transformers (MHFLT) based on modular multilevel converters (MMC) for high voltage DC applications. The multilevel dual active phase shift is proposed to operate the MHFLT using a high switching frequency

which brings about many advantages and makes the operation quite different from that of the traditional DC transformer (DCT) based on a dual active bridge and the fundamental frequency MMC widely used in flexible HVDC transmission. Specifically

MHFLT is suitable for high voltage levels

which is due to its good switching characterization

ability to cut itself off from an external fault

and it can also achieve redundancy operations when a sub-module fault occurs. In this paper

the operation

modulation method

multilevel high frequency link voltage

current

and power characterization

high frequency commutation

and switching characterization are analyzed comprehensively; the pulse rotation and distributed delay control

and fault handling strategies of MHFLT are then proposed. Finally

a prototype is built

and the experimental results verify the correctness and effectiveness of the proposed solution.