A Comprehensive Suppression Strategy for Common Ground Circulating Current Caused by Grounding Fault in PV Modules

The widely distributed large-scale photovoltaic (PV) modules suffer from a large probability of grounding fault due to the reasons, such as large area, short distance to the ground, complex series-parallel connection, and exposure in natural weather, and the produced large common ground circulating current will damage the stability of the system. This problem has been well explored in this paper. First, the generation mechanism of the common ground circulating current is analyzed, and the effect of the different dc-link voltage reference values on the stability of the system is revealed. Then, a comprehensive suppression strategy is proposed to address the abovementioned problems. From the view of ac side, the common ground circulating current can be embodied through the zero-sequence component of the three-phase inductive current, and thus, a 0-axis-based control strategy is proposed to suppress the common ground circulating current. From the view of dc side, the common ground circulating current will result in the difference between the output and input currents of PV modules, and thus, the common-mode control strategy is proposed to solve the problem. The comprehensive method needs no status switching and no communication information of other modules, which can improve the stability of the system. Finally, the experimental results based on the RT-LAB platform are presented to verify the effectiveness of the proposed control strategies.