Single-stage high reliability doubly grounded nonisolated PV grid-connected inverter

摘要

Nonisolated PV grid-connected inverters are extensively used in renewable generation systems. However, there is a shoot-through issue in traditional voltage-source inverters and common mode leakage current (CMLC) in nonisolated PV inverters. In order to address the aforementioned problems, a single-stage high reliability doubly grounded nonisolated PV grid-connected inverter is presented. The inverter is composed of a buck converter and a buck-boost converter, which operates in the positive and negative half grid periods, respectively. Grounds of the grid and PV array are shorted to eliminate the CMLC. The sinusoidal pulse width modulation (SPWM) is adopted in the proposed inverter. The proposed inverter is a single-stage system in each half grid cycle. There is no CMLC in the proposed inverter. Voltage across all semiconductors is not affected by the intrinsic capacitors of them. In addition, the inverter does not have the shoot-through issue, which increases reliability of the inverter. Only one switch is high frequency operated in each half grid period, so efficiency of the inverter can be improved, which is 98.6%. Experimental results of a 250 W single-stage high reliability doubly grounded nonisolated PV grid-connected inverter confirm the theoretical analysis. The inverter can be used in the PV application with high reliability and no CMLC.