Modulated Coupled Inductor-Based IPOP-DAB Converter With Optimized Modulation Trajectory Considering the Phase-Shift Angle Between Submodules for SST Applications

The input-parallel-output-parallel (IPOP) dual-active-bridge (DAB) converter is a popular solution to be used as a solid-state-transformer (SST) to increase current capacity for its advantages, including bidirectional power flow, soft switching, and high efficiency. To reduce circulating and turn-off currents under single-phase-shift (SPS) control, an IPOP DAB converter with a modulated coupled inductor and the optimized modulation trajectory are proposed in this article. Compared with the previous modulated coupled inductor solutions, the phase-shift angle between two modules is controlled by PWM signals from 0° to 180°, instead of just working at two fixed values (0° and 180°). Based on the derived model of the modulated coupled inductor and analysis of converter working modes, the relationship between the two phase-shift angles and the current stress of the converter is analyzed in depth. Consequently, an optimized modulation trajectory is also proposed to achieve low turn-off current and rms current for IPOP DAB converters used for SST applications. The parameters design, including leakage inductance and coupling coefficient, is introduced. A 250-kHz, 400-/400-V, 2000-W IPOP DAB prototype is built to verify the effectiveness of the proposed solution.