The Research of Sub-Synchronous Oscillation in DFIG Wind Farm under Weak AC Grid

With the large-sale wind farms connected to the power grid , the problem of sub-synchronous oscillation caused by wind farms has become more and more serious. Previous studies have shown that wind farms are prone to occur sub-synchronous oscillation when DFIG connected to power system by series compensation capacitor and PMSG through weak AC network ,and the theory of SSO in above two cases is relatively clear and has been researched mostly. Since most DFIG wind farms in China are connected to the power system through weak AC grids, there is still a risk of subsynchronous oscillations without series compensation capacitors. This paper established a transfer function model of DFIG wind farm in weak AC power network, analysed the interaction mechanism between DFIG and weak AC system in detail, The influence on its characteristics from many factors was also analyzed. Finally, the correctness of above conclusions was verified by time domain simulation.