Control Strategy for Arc-Suppression-Coil-Grounded Star-Connected Power Electronic Transformers

The grounding of low-frequency distribution transformers is a critical concern that ensures the proper operation and protection of the distribution system. The power electronic transformer (PET), as a future alternative low-frequency distribution transformer, also needs grounding. This paper studies PET operation with arc-suppression-coil (ASC) grounding in the Y-connected medium-voltage (MV) stage, focusing on the following two aspects. 1) The MV stage current stress brought by the ASC is analyzed, and a negative-sequence current compensation method is proposed to reduce the MV stage current stress. 2) The ASC impedance adjustment range that the MV stage can provide by zero-sequence voltage injection is analyzed, and a virtual impedance method is proposed to achieve this adjustment. The effectiveness of the proposed ASC-PET as well as its control strategy is verified by both simulation and experiment results.