I. Introduction
Power Electronic Transformer (PET) is the core infrastructure of new power systems and plays the function of an energy router [1–4]. As a key device in the electromagnetic coupling link of power electronic transformer, the isolation transformer has the function of variable voltage isolation, which affects the overall performance of power electronic transformer. To meet the demand for high density and high reliability of power electronic transformers in application scenarios such as offshore wind power, photovoltaic convergence and railroad traction, magnetic transformers are being developed in the direction of higher frequency and increased capacity [5–7].