Abstract：The medium-voltage insulated high-power medium-frequency transformer (MFT) used in photovoltaic grid-connected systems not only requires a large insulation distance between the high and low voltage side windings, but also needs to be poured with thermal-protective insulating materials inside. However, it can lead to problems such as serious electromagnetic interference and difficult heat dissipation in the MFT. Therefore, this paper proposes an MFT optimal design method that fully considers the core size, winding wire diameter and winding arrangement structure. In this method, the core volume is determined by the area product (AP) method, and then the loss of the MFT is minimized by free variable scanning. Based on the finite element simulation software, it is verified that the optimized design method will also reduce the electromagnetic interference area around the transformer. Finally, a 200kW/30kHz MFT was designed through the optimized design method, and a prototype was made. The comparison between theory and experiment verifies the optimized design method.
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