Study On Nonlinear Dynamic Analysis And Control For Drive System Of Wind Turbine Generators

Wind turbine generators as typical rotating machinery is a technology intensivesystem, which integrates machinery, electric and control technology. The drive system isan important part of wind turbine generators. Recently, along with unit capacity and thescale of wind turbine generators increased, the phenomenon in torsional vibration of drivesystem is increasingly outstanding. So, it is important to establish an appropriate systemmodel and accurately describe dynamic characteristics for design, status monitoring, faultdiagnosis and control for wind turbine generators. This paper conducts systematicresearches on nonlinear torsional vibration system of wind turbine generators from threeaspects, namely system modeling, stability analysis and control method of torsionalvibration system. By using analytical method, the unstable oscillation law and controlstrategy of torsional vibration system are given, which promotes the theoretical basis foroperation and design of wind turbine generators in further study.Firstly, considering the influence of nonlinear factors such as system structureparameters and outside disturbance incentive, three typical dynamics equation of the drivetorsional vibration system of wind turbine generators are established based on thegeneralized dissipative system Lagrange principle, which are two-mass drive systemmodel with nonlinear damping and outside disturbance, torsional vibration system modelwith nonlinear stiffness and outside disturbance, and another torsional vibration systemmodel considering time varying stiffness, sliding friction and outside disturbance.Secondly, considering the influence of nonlinear stiffness, the bifurcation responseequation of drive system is deduced with the method of multiple scales, and singularityanalysis is studied. Under the condition of main resonance, the influence of time delays onHopf bifurcation and limit cycle is studied based on Hopf bifurcation theory. A nonlineartime-delayed feedback controller is proposed, and drive system of wind turbine generatorsis controlled with Hopf bifurcation characteristics and vibratory amplitude. Finally,numerical simulations are performed to control vibratory amplitude in the ideal range. Thirdly, considering the influence of combination harmonic incentive, The stabilityand bifurcation characteristics of autonomous system are analyzed by constructingLyapunov function. Bifurcation response equation of non-autonomous system undercombination harmonic incentive is obtained by the method of multiple scales. Numericalmethod is employed to analyzed the effects of external excitation, the system damping andnonlinear stiffness on the process that the system enter into chaos motion viaperiod-doubling bifurcation by bifurcation diagram, time domain waveform, phasetrajectory and Poincare map. Finally, chaotic motion of drive system can be controlled asstable period motion by direct variable feedback method.