Inter Phase Transformer (IPT) With Delta Connected Secondary Windings for Reduction of the Common Mode Inductance in Parallelization of Multiple Power Converters

This paper presents a novel Inter-Phase Transformer (IPT) topology aimed at improving the parallelization of multiple three-phase power converters by minimizing the common-mode impedance without affecting the differential-mode impedance. The proposed IPT incorporates delta-connected secondary windings that are magnetically coupled but electrically isolated from the converter legs. This configuration enables significant reduction of the zero-sequence inductance and the associated leakage magnetic field and flux, which are major concerns in compact high-power converter cabinets. In addition, the proposed IPT topology can be easily designed and manufactured, since it presents the same morphology as standard transformers with equal number of columns and phases and with concentric primary and secondary windings. Then, theoretical modeling, based on magnetic equivalent circuits and Rogowski’s method, is used to derive the leakage inductance. Experimental validation is carried out using a commercial three-phase transformer, and several sinusoidal voltage-based tests confirm the effectiveness of the proposed approach. Furthermore, computer-based simulations and experiments in downscaled platforms with GaN-based converters, demonstrate the benefits of the delta-connected secondary windings in enabling efficient interleaved modulation, improving current sharing, reducing harmonic distortion, and minimizing circulating currents. The simplicity of the proposed IPT design makes it compatible with standard manufacturing processes and cost-effective for real applications.