The Study On Subsynchronous Oscillations Of Doubly Fed Wind Turbine

The sub-synchronous oscillations(SSO) of doubly-fed wind turbine isstudied in this paper by the methods combined of related facts and eigenvalueanalysis in order to avoid shaft damages caused by SSO, and try to make surethat the wind turbine system can work smoothly. The contents and results areas following(1)The flexible shaft model doubly-fed wind turbine is established basedon shaft features. The traditional wind turbine shaft rigid model is establishedin accordance with the idea creating thermal power units shaft model whichcannot reflect real character of wind turbine shaft, and cannot be used to studySSO. The flexible model is superiority to the rigid one by comparing twosimulation models in MATLAB.(2) An integral wind turbine model used to study SSO is established,which include generator model, inverter model, grid model and shaft model.The complete wind turbine model iseventually built up through theinput-output relationship of each model. At last the model is initialized at thesteady-state operating point.(3) Eigenvalues, damping ratios and frequencies are resolved byeigenvalue analysis method, relationship factors method is used to study SSO,the bigger the number is, the easierthe factor lead to SSO. The study shows thatrotor inverter parameter and rotor speed are the main factors that may lead toSSO through these methods.(4)Additional power control of SSO damping controller is used to preventSSO happening through studying of SSO, the repressive measure is correct andefficient through simulation.