An Operation Strategy for the Hybrid Distribution Transformer to Suppress the Magnetizing Inrush Current

Distribution transformers play a pivotal role as an isolation stage between varying voltage levels. However, with the increasing demands of distribution generations, the conventional low-frequency transformer (LFT) faces challenges in maintaining qualified voltage levels. In response, a hybrid distribution transformer (HDT), integrating an LFT and a power converter, emerges as an optimal solution. One crucial concern when employing a converter is the magnetizing inrush current of LFT. In this paper, an HDT topology without auxiliary transformer winding is proposed in a single phase, featuring a converter connected in series on the primary side and a converter connected in parallel on the secondary side. This configuration provides adjustment capability to address voltage irregularities. This paper delves into the working principle for the HDT, with a specific focus on the magnetizing inrush current considering line voltage variation. Further, the control strategies for line voltage regulation and magnetizing inrush current suppression are proposed. Simulation results are presented to validate the effectiveness of the proposed scheme, emphasizing its potential to enhance voltage control in distribution transformers.