This work presents the design of a planar three-phase (TP) transformer in a wye–wye (Y–Y) configuration for a dual active bridge (DAB) converter. The transformer is designed with optimized zero-sequence inductance (ZSI) to support an active power decoupling (APD) circuit connected to the primary-side neutral port. The proposed winding structure and layout minimize parasitic capacitance, thereby reducing high-frequency current distortion in the DAB stage. Finite element analysis (FEA) simulations are used to estimate the ZSI and to examine the magnetic flux distribution. Experimental validation is performed using a 3 kW TP-DAB converter with 650 V gallium nitride (GaN) devices operating at 300 kHz, confirming its ability to operate at high frequency and effective ZSI integration.
