The island distribution networks

which are located at the terminals of the traditional AC distribution networks

have the problems of single power supply

weak grid structure

and low distributed energy utilization. At the same time

there are also difficulties in switching of the operating status of the distribution networks and the coordination of internal multi-devices control modes and control objectives. In order to improve the system operating capability

an AC/DC hybrid distribution network for island was constructed by applying cascaded power electronic transformer（PET）. By analyzing the application requirements of the actual projects

the PET control architecture and strategy are comprehensively considered and designed to meet the requirements such as bidirectional power transmission

bidirectional startup

multioperating modes

and their switching;meanwhile

the DC voltage feedforward loop is added on the basis of the gyrator mode to improve the response characteristics of PET. The system test results show that PET can realize the controllable interconnection of the island AC/DC hybrid distribution networks

effectively improve the flexibility and adaptability of the power transmission and provide strong support for the safe and reliable operation of the distribution networks.