Mechanism and characteristic analyses of subsynchronous oscillations caused by the interactions between direct‐drive wind turbines and weak AC power systems

Recently, serious subsynchronous oscillation (SSO) events have occurred frequently due to the increasing interactions of direct‐drive wind turbines with power systems. This emerging SSO would cause the action of the torsional vibration protection and trip the turbine generators. To ensure the safe and stable operation of the power system and to avoid unnecessary oscillations, the mechanism and characteristics of such SSOs are investigated. In this study, the Hami power system in Xinjiang Uygur Autonomous region is taken as an example to illustrate the factors of this kind of SSO. Firstly, a study model is established according to the actual situation of this power system. Then, the topological structure and main parameters of the model are investigated in detail. In addition the control approaches, which are included in the model, are also elaborated. Finally, simulation analyses based on power system computer aided design (PSCAD)/electromagnetic transients including DC (EMTDC) are carried out to investigate the impact of the various factors on the characteristics of SSO. The presented model and results offer a reference for future research on this emerging SSO.