Large-disturbance instability modes of power system with synchronous generator and VSC interfaced generation

It is essential to study the large-disturbance stability of power systems with high proportion of power electronic devices to discover new instability modes of renewable energy generation connected to the grid. In this paper, a model of power system with synchronous generator (SG) and voltage source converter (VSC) interfaced wind power generation is built, and time-domain simulations of the system under large disturbances are carried out for the two cases in which the proportion of wind power is small and large respectively. When the wind power takes up a small proportion, the instability mode of the system is the rotor angle instability dominated by the SG. When the wind power takes up a large proportion, the instability is the caused by outer control loop. The mechanism of the new instability mode introduced in the wind power control link is analyzed from the angle of voltage limit and power limit. In addition, this paper studies the effect of low-voltage ride through (LVRT) switching strategy. Through comparison of simulation, it is verified that different switching control strategies may correspond to different fault critical clearing time, that is, different large-disturbance stability.