非隔离型三电平逆变器漏电流抑制与中点电位平衡控制

In view of the leakage current and the imbalance of the neutral point potential of the neutral point clamped (NPC) three-level inverter in the grid-connected photovoltaic system, the mechanism of the leakage current and the factors affecting the neutral point potential are analyzed in this paper. Aiming at the shortcomings of existing modulation strategies, based on the existing modulation strategy, the modulation sector with the traditional modulation strategy is re-divided. On this basis, suitable switching sequences are selected, and a new type of large medium and small vector modulation strategy is obtained. The modulation strategy proposed in the paper has low variation amplitude of common-mode voltage, high variation amplitude of DC voltage, low total harmonic distortion ratio of the output voltage, and it can effectively control the neutral point potential. Finally, through simulation and experiments, the proposed strategy is compared with the traditional modulation strategy in terms of leakage current suppression and neutral point potential control, and the effectiveness of the proposed modulation strategy is verified.