| In recent years,the application of high-capacity flywheel energy storage system in the field of peak shaving and frequency modulation of auxiliary power grid has gradually increased.The flywheel rotor of high-capacity energy storage under a wide speed range must repeatedly cross the critical speed in the process of charge and discharge.The prominent vibration problem increases the possibility of failure of flywheel energy storage system and directly affects the stable operation of flywheel energy storage system.To realize the optimal design of dynamic characteristics and vibration control of flywheel energy storage system and meet the urgent needs of current engineering practice,it is of great significance to carry out the accurate dynamic modeling of flywheel energy storage system and the research on the vibration characteristics of flywheel rotor system under fault.The large capacity flywheel energy storage system is supported by a variety of bearings and has structural coupling characteristics,which makes the dynamic modeling of the large capacity flywheel energy storage system more complex.At present,the existing dynamic model of the flywheel energy storage system is highly simplified,and the coupling characteristics between various components are not considered.In addition,the vibration characteristics of large capacity flywheel rotor system under typical fault conditions such as mass imbalance,basic excitation,and crack fault also need to be further fully discussed.Based on this,this paper systematically studies some key problems of accurate dynamic modeling and dynamic characteristic analysis of large capacity flywheel rotor system.The main research contents of this paper are as follows:(1)In view of the fact that the coupling characteristics between the flywheel rotor and the support system are not considered in the current dynamic modeling of the flywheel rotor system,the permanent magnetic bearing and mechanical bearing support models of the flywheel rotor are established based on the permanent magnet theory and the contact theory,and the bearing coupling stiffness between the flywheel rotor and the outer shell is derived.Taking a real large capacity flywheel energy storage system as the prototype,the dynamic mathematical model of flywheel rotor bearing housing coupling system(flywheel rotor system for short)considering various bearing supports and structural coupling characteristics is established based on the finite element modeling theory.Then the critical speed and mode shape of flywheel rotor bearing housing coupling system are calculated.The critical speed of the actual flywheel energy storage system is obtained by testing the vibration response,and compared with the numerical results,which verifies the accuracy of the dynamic model of the flywheel rotor bearing housing coupling system.(2)Based on the dynamic model of flywheel rotor system,the steady-state and transient vibration response characteristics of flywheel rotor with mass unbalance are studied,and the effects of unbalance and stiffness and damping of support system are analyzed.The results show that the steady-state response amplitude of the flywheel rotor system increases with the increase of the unbalance,and the damping of the support system can effectively suppress this vibration.The stiffness of the support system has an impact on the critical speed and vibration amplitude of the flywheel rotor system.With the increase of the stiffness,the critical speed of the flywheel rotor system increases,and the vibration amplitude of the flywheel rotor system fluctuates.In the process of repeated charge and discharge,the transient response amplitude of the flywheel rotor system has a resonance peak at the critical speed.The accuracy of the calculation is verified by comparing the measured data with the numerical results.In addition,aiming at the problem of parameter uncertainty caused by the structural deterioration of the flywheel rotor system during long-term operation,the Chebyshev interval analysis method based on derivative information is introduced to analyze the mass unbalance vibration response of the flywheel rotor system under parameter uncertainty.The results show that the vibration response of flywheel rotor system has obvious interval characteristics under the condition of parameter uncertainty,and the uncertainty of bearing stiffness has the greatest impact on the vibration response of flywheel rotor system.(3)Considering the effect of foundation excitation,the dynamic model of flywheel rotor system is extended by introducing the rotor modeling theory of maneuvering aircraft,and a dynamic mathematical model of flywheel rotor foundation coupling system with multiple foundation motion excitations is established.The vibration response characteristics of flywheel rotor foundation coupling system under unbalanced force and external excitation such as foundation rotation,impact excitation,acceleration excitation and seismic excitation are discussed.The results show that the rotation of the foundation mainly affects the critical speed of the flywheel rotor foundation coupling system,and the rotation direction and speed have an impact on the critical speed.The translation,impact excitation and seismic excitation of the foundation mainly affect the transient response amplitude of the flywheel rotor foundation coupling system,and the greater the excitation intensity,the longer the excitation time,the greater the impact on the transient response amplitude of the system.(4)Aiming at the dynamic response of flywheel rotor system with crack fault,considering the non-gravity dominant bending characteristics of flywheel rotor when rotating,a time-varying dynamic mathematical model of cracked flywheel rotor system is constructed based on the neutral axis crack model.The effects of speed,crack location and crack depth on the dynamic characteristics of flywheel rotor system are studied.The dynamic characteristics of flywheel rotor system under crack fault are analyzed from the aspects of frequency spectrum and speed rise response curve.The results show that the sunken ring of the axis track and the 3x,5x components in the frequency spectrum are the important characteristics of the crack,and the shape of the axis track and the frequency spectrum components are also different under different rotating speeds.In addition,the crack location affects the shape of the axis trajectory and the amplitude of each frequency component in the frequency spectrum but does not affect the critical speed.The depth of the crack does not change the shape and spectrum components of the axis track but affects the size and spectrum amplitude of the axis track.(5)Aiming at the stability analysis of flywheel rotor system with crack fault in the full speed range,a stability solution method based on Floquet stability theory is proposed.The stability of flywheel rotor system with crack fault is analyzed.The effects of crack type,crack number,crack location,crack depth,bearing stiffness and damping on the stability of flywheel rotor system are discussed.The results show that the speed,crack depth,crack location and the number of cracks have significant effects on the unstable region of the flywheel rotor,and the speed,crack depth and location are the main influencing factors.The stability of flywheel rotor system with open cracks and breathing cracks is compared.The results show that breathing cracks have a greater impact on the stability of flywheel rotor.In addition,the bearing stiffness and damping also have an impact on the stability of the flywheel rotor system.The bearing stiffness causes the instability region to shift,and the bearing damping increases the stability of the flywheel rotor system. |
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