A Dual-Active-Bridge-Based Fully ZVS HF-Isolated Inverter With Low Decoupling Capacitance

This paper proposes a novel dual active bridge (DAB)-based high-frequency-isolated dc-ac converter topology suitable for photovoltaic microinverter applications. The circuit configuration on the secondary sides of the employed three-winding transformer results in high-frequency current injection into each of the switch nodes, thereby making zero-voltage-switching (ZVS) operation of the devices possible. The topology achieves this functionality while using the same number of devices as conventional two-stage and single-stage high-frequency-link or DAB-based solutions. Furthermore, following a control-oriented power pulsation decoupling strategy involving dynamic variation of phase shift, twice line-frequency energy buffering can be handled on the high-voltage secondary side, thereby resulting in reduction in decoupling capacitance requirement. The working principle of the circuit and the associated control scheme is described followed by a detailed ZVS analysis. Simulation studies and experimental tests on a 310 W prototype verify circuit operation and exhibit efficiency improvements compared to a similar two-stage solution.