Improved Control Method of Grid-connected Converter Based on Voltage Perturbation Compensation Under Weak Grid Conditions

摘要

The three-phase grid-connected converter control system and the grid impedance are coupled with each other under weak grid conditions, which brings in negative influence on the system. In this paper, the impedance model of a three-phase grid-connected converter including current loop, PLL and DC voltage loop is established in d-q frame. The influence of PLL and DC voltage loop proportional coefficient on system stability is analyzed. According to the transfer relationship of each variable in the impedance model, the PCC voltage perturbation paths to the PLL and DC voltage loop are analyzed respectively. On the basis of voltage perturbation paths, a compensation control strategy is proposed. The impedance analysis results show that the proposed method can effectively improve the system stability under weak. The experimental results verify the correctness of the theoretical analysis and the effectiveness of the proposed method.