A Novel Dual-mode Micro-inverter for Photovoltaic AC Module Applications

Based on the combination of boost-flyback and flyback converter, a dual-mode mirco-inverter with pseudo-dc-link was proposed in this paper. This new topology operates at boost-flyback (BF) or flyback (F) mode alternatively dependent on a pair of double-line frequency complementary switches. During the BF mode, high voltage gain with low voltage stress on the power devices is obtained owing to the serial output of the boost and flyback sub-converter. Furthermore, this mode also provides a passive snubber to recycle the energy stored in the leakage inductor of transformer and clamp the turn-off voltage spike of main switch. The F mode enables the dual-mode converter to regulate the output voltage lower than the input voltage, making it possible to generate a rectified sinusoidal waveform at the dc link. The operation of the dual-mode mirco-inverter with peak current control in boundary conduction mode (BCM) is described in detail, and the mathematical expression of reference current aiming to lower total harmonic distortion (THD) is derived theoretically. Finally, a 240W prototype was implemented to validate the theoretical analysis and the benefits of the proposed topology.