A Synergistic Modulation Method for Simultaneous Active Power Decoupling and Tank Current Reduction in Single-Stage Dual Active Bridge Microinverters

Conventional single-stage dual active bridge (DAB) microinverters typically suffer from bulky input capacitors for double-line frequency power decoupling, significant input current pulsation, and excessive circulating current under single-phase-shift (SPS) modulation. This paper proposes a novel synergistic modulation method to comprehensively address these limitations. The proposed method achieves active power decoupling (APD) under arbitrary power factor conditions by repurposing the inherent primary-side DC-blocking capacitor, thus avoiding any hardware modifications. Meanwhile, the modulation parameters are optimized to substantially reduce the tank current. A systematic theoretical analysis is conducted, and a large-signal-based automatic decoupling control loop is developed. Experimental results on a 500VA prototype demonstrate that the proposed modulation method reduces the decoupling capacitor volume by 75%, suppresses the double-line frequency pulsation in the input current by 87%, and decreases the Root Mean Square (RMS) value of the tank current by 27%, thereby improving the circuit's power density, maximum power point tracking (MPPT) accuracy, and overall efficiency.