Research On Nonlinear Dynamics Of Wind Turbine Multi-stage Planetary Gear System

Gearboxes are an important component of doubly-fed wind turbines.Multi-stage planetary gear transmission system is widely used in megawatt wind power gearbox due to its advantages of compact structure,strong bearing capacity and high transmission efficiency.Compared with the single-stage planetary gear system,multi-stage planetary gear system shows more complex dynamic response under the influence of internal and external excitation and inter-stage coupling.Therefore,this paper takes the multi-stage planetary gear transmission system of the wind turbine as the research objects to study the nonlinear dynamic characteristics of the system.The main research contents include:1.The two stages planetary gear system of the wind power gearbox is used as the physical model.The torsional stiffness of the transmission shaft between the system stages is introduced.Based on the consideration of nonlinear factors such as time-varying meshing stiffness,comprehensive meshing error and backlash,the torsional dynamic model of the system is established by using the method of concentrated parameters.The variable step size Gill integral method and Runge-Kutta method are used to solve the model.The results show that change of excitation frequency will cause the system to exhibit abundant nonlinear dynamic behavior and the relative vibration amplitude of the system will occur obvious changes at different excitation frequencies.In addition,it is found that properly increasing the system’s meshing damping ratio can significantly suppress the chaotic response of the system.Properly reducing the backlash is beneficial to the stable operation of the system.2.Further considering the dynamic coupling influence of the parallel shaft gear,the two planetary gear stages plus a parallel gear stage coupling transmission system of the wind power gearbox is taken as the research object.Considering the nonlinear factors such as meshing error,variable meshing stiffness,backlash and the coupling factors such as interstage coupling stiffness and interstage coupling damping of the the three-stage coupled transmission system,The dynamic model of the wind power gearbox transmission system was derived using the centralized parameter method.The establishment of the model laid the foundation for the further study of the bifurcation characteristics and dynamic response of the system.3.The global bifurcation diagram,phase trajectory diagram,Poincaré map and spectrum diagram are used to discuss the influence of the characteristic parameters including excitation frequency and comprehensive meshing error on the torsional dynamic response of the system.The bifurcation characteristics of the system were verified using the largest Lyapunov exponent.The analysis results show that compared with the two-stage planetary gear transmission system,the two planetary gear stage plus a parallel gear stage coupling transmission system also have complex and abundant dynamic behavior at the varying excitation frequency,such as quasi-periodic motion,chaotic motion and period-doubling bifurcation,and the trends between two systems are similar.However,due to the coupling influence of the parallel shaft gear,the chaotic response range of the system is extended at high excitation frequencies.With the increase of the comprehensive meshing error,the system changes from harmonic periodic state to chaotic state,indicating that the increase of the comprehensive meshing error has a negative impact on the stable operation of the system.