Abstract The characteristics of the boundary conduction mode (BCM) hybrid-type photovoltaic (PV) micro-inverter are analyzed in detail in this paper. This new topology is a non-isolated pseudo-dc-link structure, which inherits the advantages of low transformer turns ratio, low leakage inductance and low voltage stress of boost-flyback converter, as well as the step-down function of flyback converter. Exploiting the natural resonance of the hybrid-type converter in BCM, the zero-voltage switching (ZVS) or valley switching (VS) of the main switch, and the zero-current switching (ZCS) of the rectifier diodes are achieved. Furthermore, owing to the inherent passive snubber in boost-flyback converter, the leakage energy of transformer is recycled, and the turn-off voltage spike of the main switch is clamped. Because of these characteristics mentioned above, the hybrid-type inverter has smaller transformer volume and higher converter efficiency compared with the conventional flyback inverter. The operation of this topology is described, and the mathematical expression of reference current is derived to guarantee high quality of injected grid current. Finally, a 240W prototype was built to verify the correctness of theoretical analysis and the performance of the topology.
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2020, Vol. 35 
