Research on Power Oscillation Suppression Strategy of Grid-connected Composite System Based on Impedance Optimization

In recent years, the problem of power oscillation caused by the interaction between AC power grid and grid-connected converter has attracted wide attention of scholars at home and abroad. In this paper, an impedance optimization control strategy is adopted to enhance the stability of the back-to-back MMC-HVDC grid-connected composite system. Firstly, the impedance model of MMC converter in composite system is established, and the influence of power change on system stability is analyzed combined with impedance stability criterion. On this basis, the impedance optimization control method of correcting the current command value is adopted to effectively suppress the oscillation phenomenon in the process of power transfer. Finally, the correctness of the theoretical analysis and the effectiveness of the control strategy are proved by time domain simulation.