Dual-Period-Decoupled Space Vector Phase-Shifted Modulation for DAB-Based Three-Phase Single-Stage AC-DC Converter

When the conventional space vector phase-shifted modulation is applied to the dual active bridge (DAB)-based three-phase single-stage (DAB-3P1S) ac-dc converter, the ac-side current error is caused due to the coupling of transformer currents in the adjacent switching periods and the imprecise dwell times of the active current vectors. By analogizing the DAB-3P1S ac-dc converter into the DAB-based dc-dc converter, a dual-period-decoupled space vector phase-shifted modulation based on three phase shifts is proposed to decouple the transformer currents, thus eliminating the ac-side current distortion. Moreover, taking the minimization of the rms value of the transformer current per switching period as the constant, the exact relationship between the desired ac-side current and the three phase shifts is derived to realize the efficiency improvement. Detailed experimental results validate the correctness of the theoretical analysis and the feasibility of the proposed modulation strategy.