| With the aggravation of environmental pollution and energy crisis,wind power generation,which is a clean and efficient renewable energy,has been paid more and more attention in recent years.Gear transmission system is the key component of the wind turbine to realize energy conversion.Due to the randomness of wind speed,it always works under the bad condition as variable speed and random load.At the same time,the wind turbine transmission system is a high-power and complex electromechanical coupling system with blade driving generator through a multistage gearbox.As blade,gearbox,shafting and generator interact with each other,the internal and external excitation and the nonlinear factors are various.The superposition of the above factors makes the wind turbine transmission system very complex,failures occur frequently and cause long downtime,which seriously restricts the generating efficiency and economic benefits of the wind generation set.In view of the characteristics of multi-working conditions and strong electromechanical coupling of the wind turbine transmission system,this thesis establishes an electromechanical coupling dynamic model of the wind turbine transmission system under the actual operating conditions by comprehensively considering the aerodynamic load of the blade,vector control strategy of the generator and operation control strategy of the wind turbine set.The dynamic characteristics of this system under power generating,starting and braking conditions are discussed respectively.The interaction between mechanical parts and electrical parts of this system under different working conditions is revealed.The main research contents of this thesis are as follows:(1)Considering time-varying and nonlinear factors such as mesh stiffness,comprehensive meshing error and backlash etc,according to the characteristics that the wind power transmission system running in unsteady state,a torsional dynamic model of wind turbine drive system for variable speed condition is established through lumped-parameter method.Then a electromechanical coupling dynamic model is formed by combining this model with vector control modle of the generator and pitch angle control model of the blade.(2)The natural frequency and vibration mode of the wind turbine transmission system are calculated and analyzed.The influence of structural parameters of the blade and the generator on the natural frequency of this system is discussed.Based on the modal energy distribution and the Campbell diagram,the resonance position of this system is identified,and the influence of the stiffness of the generator connection shaft on the resonance position is discussed.(3)The dynamic response characteristics of the wind turbine transmission system in the two stages(maximum wind energy tracking stage and constant power stage)of power generating condition are studied separately.The interaction between mechanical system and electrical system of this system under random speed wind is revealed.(4)The dynamic characteristics of the wind turbine transmission system under impact load,which is caused by the loading and unloading of the electromagnetic torque occurs in starting and braking conditions,are studied.The electromagnetic stiffness characteristic of the electromagnetic torque under the starting condition is revealed.The influence of this electromagnetic stiffness on the inherent vibration characteristics of the transmission system is discussed.The research results of this thesis can provide theoretical basis for the integrated design and operation condition monitoring of the wind turbine transmission electromechanical system. |
