A Low-cost Solar Micro-inverter with Soft-switching Capability Utilizing Circulating Current

This paper presents a low-cost high-efficiency photovoltaic (PV) micro-inverter with soft-switching capability. The system is based on a partial power processing resonant front end dc-dc stage, followed by an interleaved inverter stage. The proposed new soft-switching modulation scheme enables significant cost and volume reduction of the magnetics in the inverter stage. In order to shrink the magnetics, the interleaved inverter modulation scheme adopts a real-time varying phase-shift delay control in a way such that a smaller inter-phase transformer (IPT) can be utilized due to reduced voltage-second and the additional conduction loss caused by the circulating current can be minimized. In addition, the zero-voltage-switching (ZVS) operation in the full operation range can be maintained. As a result, the power MOSFETs body-diode reverse-recovery loss can be eliminated and the power stage switching frequency can be further increased. The operation principle of new modulation scheme and ZVS operation are analyzed. Key simulation result and baseline experimental results are presented to validate the analysis.