Investigation on the Mechanism and Influencing Factors of Subsynchronous Torsional Oscillations Induced by PMSG Wind Farms

The PMSG wind farms connected to the weak grid may induce the subsynchronous torsional oscillations (SSTOs), which threatens the system security. First, based on the power system that PMSG wind farms and synchronous generator are connected to the grid without series compensated lines, a state space model of the system is established, and the mechanism of SSTOs induced by the interaction between PLL-dominated mode and torsional mode (TM) is analyzed. Second, the influence of DC voltage control (DVC) on the torsional mode stability is studied. Third, when the interaction between multiple PMSGs is considered, the Monte Carlo method is used to investigate the relation between the bandwidths of different PLLs and the torsional mode stability. Finally, the time-domain simulation models based on the IEEE first benchmark model are established in PSCAD/EMTDC to verify the validity and correctness of the research conclusions.