Low-frequency Stability Analysis of Grid-Forming DFIG

The grid-forming DFIG has the function of self-synchronization and active support of the power grid. In recent years, it has been favored by scholars at home and abroad. However, with the gradual deepening of research, the problem of grid-forming DFIG participating in inter-system oscillation has gradually become prominent. In this paper, firstly, a grid-forming DFIG under virtual synchronous control strategy is built. Secondly, a mathematical model is established. From the perspective of electrical damping, the transfer function is used to analyze the low-frequency oscillation characteristics and instability mechanism, and the correctness of the oscillation mechanism is verified by simulation. According to the analysis and simulation results, the low frequency oscillation stability of the model is poor and prone to instability under strong power grid. In this paper, an improvement measure for a virtual synchronous control link is proposed. The control branch is added to the link to increase the system damping, so that the system has good low-frequency stability under strong and weak power grids.