| The flywheel energy storage system is a new type of green energy storage method,which realizes the storage and release of energy through the rotation of the flywheel.In order to make the flywheel rotor system operate safely and reliably in practical applications,the study of system vibration characteristics has always been of great concern.In this paper,a vertical flywheel energy storage system with a rated speed of 5000～15000rpm and an energy storage of 600Wh is taken as the research object.In order to make the system operate more stably,the method of combining with theory experimentation is used to analyze the critical speed and vibration characteristics of the system.Based on the calculation formula of electromagnetic force and the working principle of electromagnetic bearing,the electromagnetic support force model of radial electromagnetic bearing is deduced,and the equivalent stiffness and equivalent damping coefficient of the electromagnetic bearing are calculated;the bending stiffness enhancement coefficient of the system is calculated,and the influence of the width of the interference fit,the amount of interference and the radius of the flywheel rotor on the bending stiffness coefficient is discussed;the system model is simplified,and the dynamic model of the system is established.According to the transfer matrix method,the flywheel rotor is discretized,the transfer matrix of the flywheel system from the element to the whole is established based on the bending stiffness enhancement coefficient,and the critical speed of interference fit connected flywheel rotor system is calculated.With the help of Workbench software,the interference fit rotor system model is established,and the rationality of the theoretical analysis is verified by comparing the critical speed and mode shape of the rigidly connected rotor system model.Through the combination of theoretical calculation and simulation analysis,the theoretical value of the contact stress of the interference fit is calculated,and the relationship between interference fit connection parameters and critical speed of the system is analyzed,including the amount of interference,the normal contact stiffness and coefficient of friction of the contact surface.The 600Wh flywheel energy storage test prototype was tested for debugging and speed increase,and the data collected by the sensor in the test was processed and analyzed.According to the signal on the oscilloscope,the movement of the flywheel rotor at different speeds during the speed-up process is analyzed.By filtering the vibration signal when the system is running at 3000rpm and 6000rpm,the vibration amplitude of the radial electromagnetic bearing rotor is obtained.According to the drawn frequency domain diagram and time domain diagram,near the critical speed,the rotor’s vibration amplitude is relatively large obviously,but the maximum vibration amplitude much less than air gap value of the electromagnetic bearing 0.3mm,which meets the design requirements of the system,and the unbalanced response of the flywheel rotor is at the same frequency as its own speed. |
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