A Novel Multiple-Medium-AC-Port Power Electronic Transformer

The multiport power electronic transformer (PET) is a critical equipment in ac/dc hybrid distribution grids, which has the functions of multidirectional power flow, flexible power flow regulation and reactive power control, and fault isolation. However, most proposed PETs have only a single-medium-voltage-ac (MVac) port, limiting their application scenarios in distribution grids. To address this problem, in this article, we propose a PET topology with multiple controllable MVac ports based on the cascaded H-bridge PET. The proposed PET topology can connect to multiple-MVac feeders and supply low-voltage-side loads through multiple terminals, achieving the full utilization of the remaining capacity of connected feeders, thus delaying the distribution capacity expansion and grid upgrade due to the rapid development of energy electrification. Besides, the decoupling control of active and reactive power for each feeder can be achieved. In this article, the operating principle, energy balance mechanism, control strategies, and design and comprehensive comparison of the proposed topology are studied. The simulation and experimental results demonstrate the validity of the proposed topology and control strategy.