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Impact of grounding fault in PV modules on AC side and the suppression strategy based on 0‐axis control

The widely distributed large-scale photovoltaic (PV) modules suffer from a large probability of grounding fault due to their own characteristics and natural weather. This problem has been well explored in this study. Firstly, it is analysed that the grounding fault in PV modules will cause the third-harmonic voltage, DC bias voltage and common ground circulating current in the PV inverter system. Secondly, a 0-axis based control strategy is proposed to solve the above problems, which means that the zero-sequence voltage is controlled through a proportional-resonant controller in the outer loop, and the zero-sequence current is controlled in the inner loop through a proportional controller. Thirdly, the square of DC side voltage is controlled to address the non-linear relationship between capacitor energy and its voltage. Finally, the experimental results based on RTLAB platform are presented to verify the effectiveness of the proposed control strategy. In summary, this study proposes a control thought to suppress the undesirable phenomenon caused by the grounding fault in PV modules, and the method needs no status switching and hardware cost.