High efficiency transformerless photovoltaic inverter with wide-range power factor capability

Photovoltaic (PV) inverter is the most important part for energy conversion, and the current research focus for PV inverter is high efficiency, high reliability, and low-output ac-current distortion. With considerable grid-connected PV installation in last few years, high penetration PV system is desired, which requires integrating PV inverter into grid regulation. New code in Germany already requires PV inverter providing system regulation and service for low voltage distribution system. One of obvious impact on PV inverter is reactive power generation requirement. Most state-of-the-art high-efficiency PV inverters that adopt single-stage topology only allow unity power generation but none of them are able to generate reactive power. This paper proposes a high-efficiency dual-buck full-bridge PV inverter for a wide range power factor operation. Additionally, a novel hybrid bipolar PWM method is proposed to achieve low ground leakage current and low output current distortion in the PV system. At last, simulation and experiment demonstrate that the proposed PV inverter system can provide a wide-range power factor operation with high efficiency, low ground leakage current, and low output current distortion.