Abstract: Power electronic transformer(PET) is widely used in power transmission and distribution system due to the advantages of small volume, harmonic control, power control, and electrical isolation. The combination of modular multilevel converter(MMC) and PET can solve the problem of power quality effectively in medium- and high-voltage distribution network. However, there are many unexpected interference factors in the transmission and distribution process, which lead to system instability and affect the power quality of transmission and distribution. In order to improve the reliability and dynamic response of the system under non-ideal conditions, the passivity-based control-sliding-mode control(PBC-SMC) based on MMC-PET is proposed. Firstly, the PBC controller based on Euler-Lagrange (EL) model of MMC is applied to the inner loop current control, and then the sliding mode control is introduced, which can effectively solve the problem that PBC control is excessively dependent on system parameters, so that the control system has stronger anti-interference ability and faster response speed. The output DC voltage of intermediate isolation stage is stabilized by phase shift voltage regulation control, and the PBC controller of output stage inverter is designed. Finally, the MMC-PET simulation system is built for experimental verification. The results show that the PBC-SMC control method of MMC-PET is effective and superior under non-ideal conditions.