A 3-kW Two-Stage Transformerless PV Inverter With Resonant DC Link and ZVS-PWM Operation

Photovoltaic (PV) inverters play important roles in renewable energy integration. Reducing the switching loss is a main challenge in improving the efficiency and power density. This article presents the design, implementation, and field test of a 3-kW two-stage commercial-ready transformerless PV inverter with resonant dc link and zero-voltage-switching pulsewidth modulation (ZVS-PWM) operation. The ZVS-PWM operation periodically resonates the dc-link voltage of the inverter to zero for ZVS of the inverter switches, which enables higher switching frequency and significantly reduced magnetic component size. A 30-kW distributed PV system comprising ten ZVS-PWM PV inverters was built and tested for more than 100 days to evaluate the long-term performance of the PV inverter. The key figure-of-merits for grid-interface operation, such as efficiency, power density, total harmonic distortion, and leakage current, are measured, analyzed, and reported.