Abstract: The power electronic transformer（PET） applied to the medium and high voltage distribution network widely adopts a two-stage cascade structure of a cascaded H-bridge rectifier and a dual-active bridge DC/DC converter. Aiming at the problem of extremely slow simulation speed in offline simulation platforms such as PSCAD/EMTDC and MATLAB, based on the Thévenin’s equivalent and nested fast simultaneous solving algorithm, an electromagnetic transient simulation accelerated model of cascaded H-bridge PET was proposed. Specifically, by arranging the decoupling companion network of the primary/secondary side of the high-frequency transformer flexibly, the cascaded sub-modules were divided into two single-port networks, and then the equivalent part of the Thévenin’s（Norton’s） equivalent parameters were forwardly solved. Then, the equivalent part was substituted into the electromagnetic transient program for overall solution and inverse solution to initialize the electrical network for the next simulation step. Since the external equivalent form was a Thevenin’s（Norton’s） equivalent circuit with only 4 external nodes, the computational complexity of the proposed model in the overall system solution process hardly increased with the number of submodules. The cascaded H-bridge PET closed-loop control system was built in the PSCAD/EMTDC. Compared with the detailed model simulation results, the proposed model can accurately simulate the PET transient steady-state process and has a high acceleration ratio.