Coordinated Control Method of Re‐Constructable Hybrid Distribution Transformers with DC Mutual Connection for Voltage Sag Compensation

ABSTRACT The proliferation of distributed generation promotes active distribution networks (ADNs) while challenging power quality management. The topologically re‐construable hybrid distribution transformer (ReC‐HDT), capable of compensating for voltage sags, suppressing harmonics, and eliminating imbalances, has garnered considerable attention. However, although the voltage sag compensation capability of ReC‐HDT is superior to conventional HDTs, it remains constrained by capacity limitations. This constraint may cause insufficient compensation for downstream sensitive loads in critical scenarios. Since voltage sags are sporadic quality issues, simply increasing converter capacity to address these demands would incur substantial costs. Therefore, to address this without capacity upgrades, interconnecting two ReC‐HDTs via DC links is proposed to expand the compensation range. However, multiple operational modes introduced by interconnection complicate control coordination. This paper analyzes the structure of a dual‐station‐area interconnected system, detailing the topology reconstruction method and the operational mechanisms of the ReC‐HDT. On this basis, four interconnection modes and their compensable voltage sag ranges are derived. Furthermore, a multi‐mode coordinated control strategy for the interconnected system is proposed. Finally, the effectiveness of the proposed strategy is validated through digital simulations on the PLECS platform and hardware‐in‐loop experiments.