Current distortion correction in dual buck photovoltaic inverter with a novel PWM modulation and control method

The trend for photovoltaic (PV) inverter is toward low cost, high efficiency, high reliability, low ground leakage current, and low-output ac-current distortion. This paper would introduce high efficiency and low cost dual buck PV inverter, which has no reverse recovery problem for MOSFET and is very suitable for Super-junction power MOSFETs application. However, due to the duty cycle would be 50% at zero-crossing, current would have a significant distortion when it adopts bipolar PWM for PV application. This paper would propose a novel modulation method for bipolar PWM, which provides 0% duty cycle at zero-crossing. With this modulation method, the current zero-crossing distortion would be eliminated, but the total current would have distortion due to nonlinear modulation. In the last part, combined with proposed PWM modulation method, a repetitive current controller is introduced to eliminate the distortion from nonlinear modulation. All the experiment results in standalone (380Vdc, 208Vac) verified the analysis and proposed method for current distortion correction in dual buck PV inverter.