Analysis On Dynamic Characteristics Of Large Turbo-Generator Unit Shafting Under Electro-mechanical Coupling

With the rapid development of China’s economy,society’s demand for the power industry is growing.China is still dominated by thermal power generation at present.On the one hand,the turbo-generator shafting becomes longer and the stiffness decreases as the unit capacity becomes larger.On the other hand,the diversity of electricity load,long-distance and large capacity transmission network,and application of new transmission technologies have an impact on the dynamic characteristics of the unit.These reasons will easily lead to the coupling of between the electrical system and the mechanical system,result in the vibration of the large turbo-generator shafting and subsynchronous resonance to endanger the safe and economic operation of the unit seriously.This paper takes a 600MW supercritical steam turbine unit as the research object.The main research contents are as follows:Firstly,establishing the continuous quality model of 600MW supercritical turbo-generator shafting.The blade is applied to the model by means of additional moment of inertia.Carring out the modal analysis under the ANSYS software with the finite element method,calculating the natural frequency and vibration modes of bending vibration and torsional vibration.And compare the inherent characteristics between the single rotor and the shafting.Secondly,carring out the unbalanced response analysis of the shafting to obtain the amplitude-frequency characteristic curve and the phase-frequency characteristic curve.Analyzing the influence of the unbalanced mass moment on the vibration characteristics.The amplitude-frequency characteristic curve at the bearing is drawn,which can be used in the unit vibration monitoring.Discussing the influence of the damping of bearing on the unbalanced response of the shafting.Finally,taking the electro-mechanical coupling system of the steam turbo-generator unit and the power grid as the object,using the time domain simulation method to establish the power system model with series capacitance compensator and the torque distribution between different shaft segments is obtained.Simulating the torsional vibration transient response of the shafting under different short circuit fault conditions.Discussing the influence of the series compensation on the subsynchronous resonance problem.Calculating the theoretical stress concentration factor of dangerous shaft segments.