A Novel Multiple-Medium-AC-Port Power Electronic Transformer
Authors: Jianwen Zhang; Hongming Li; Xinyi Kong; Jianqiao Zhou; Gang Shi; Jiajie Zang, Jiacheng Wang
Abstract:
The power electronic transformer (PET) has emerged as a key enabler for ac/dc hybrid distribution grids, providing flexible power flow regulation while reducing overall size and weight. However, existing PET solutions—such as cascaded H-bridge PETs (CHB-PETs) and modular multilevel converter PETs (MMC-PETs)—are constrained by their single-MVac-port architecture. With the increasing penetration of distributed renewable generation and variable loads such as superchargers, single-port PETs are exposed to feeder power flow congestion and overvoltage risks. To address these issues, this paper proposes a novel multi-ac-port PET (MACP-PET) topology based on the CHB structure, which integrates small-capacity half-bridge submodules (HBSMs) to extend additional MVac ports. The proposed design offers the advantage of flexible power flow regulation among multiple ports and reduces overall capacity requirements compared with approaches that rely on multiple full-capacity PET units.
We further develop control and design methods to ensure stable operation. A decoupled control strategy is introduced to independently regulate each feeder’s active and reactive power, while an energy balance mechanism is established to maintain system stability. In addition, optimized design guidelines for the voltage rating and capacitance of the power flow control module (PFCM) are proposed to enhance performance. Comparative analysis demonstrates that, under a three-feeder scenario, the MACP-PET achieves significant reductions in device utilization: ac-side semiconductors are reduced by 50%, dc-side devices by 58.3%, and submodule capacitors by 49.3% compared with conventional multi-CHB-PET schemes, with the advantages further amplified as the number of feeders increases. Finally, the feasibility of the proposed topology and control strategy is verified through a 10 kV/750 V/3 MVA 3-port simulation and a 240 V/60 V/2.5 kVA 3-port experiment, confirming its capability to achieve reliable multi-port power regulation.
In summary, this paper aims to address the limitations of conventional single-port PETs by proposing a novel MACP-PET topology with enhanced control and design methods. The proposed MACP-PET provides an optimized multi-port solution for future ac/dc hybrid distribution grids, enabling flexible multi-port power regulation with significantly reduced component usage.
