【作者】 向玲；

【导师】 朱永利； 唐贵基；

【作者基本信息】 华北电力大学（河北） ， 电力系统及其自动化， 2009， 博士

【摘要】 随着电力系统的发展,汽轮发电机组振动问题越来越突出。电力系统故障和一些运行方式都会使电网产生较大冲击,引起电网振荡,导致机组轴系产生扭振,甚至造成轴系破坏事故。在轴系振动特性方面,弯振和扭振之间也相互影响、相互作用。由于现场试验具有一定的局限性和危险性,人们开展了汽轮发电机组模拟系统的研究,并积极寻找合理有效的试验手段。为此,论文针对该领域中几个关键性问题进行了研究,主要工作如下:采用有限元分析方法对次同步谐振模拟机轴系进行了固有特性的分析计算,有限元的计算结果与电网冲击下轴系扭振的试验结果基本一致。电网冲击下次同步谐振模拟机轴系的扭振响应试验发现三相短路故障冲击对轴系的扭振响应最大,能激励出轴系扭振的前三阶固有频率。以Jeffcott单质量不平衡转子和齿式联轴器不对中转子为研究对象,分析了转子弯扭耦合振动的频率特性,理论分析与模拟机轴系弯扭振动试验分析结果一致。结果表明轴系弯扭振动是相互影响的、相互作用的。电网冲击下的次同步谐振模拟机轴系弯扭振动试验获得了目前尚缺乏的重要的机组轴系弯扭振动试验数据。试验数据分析发现弯振对扭振的影响表现在扭振幅值谱中包含工频、倍频和N /3X频率成分,扭振对弯振的影响表现在弯振幅值谱中工频和二倍频幅值的变化。次同步谐振下轴系弯扭振动试验信号分析发现扭振具有抑制轴系复杂频率成分振动的能力。当系统发生机电耦合的次同步谐振时,故障前出现在扭振谱图上的工频、倍频和N /3X频率成分都消失了,只有与次同步谐振频率互补的扭振固有频率存在。在次同步谐振发生的时间内,弯振谱图上二倍频成分消失,工频成分的幅值变小。由轴系弯扭振动的试验分析结果提出了把扭振信息作为故障征兆的新思路,扭振包含丰富的频率信息,在进行汽轮发电机组轴系故障诊断时,扭振和弯振都应考虑并作为故障特征指标。首次将HHT应用于电网冲击下机电耦合次同步谐振的扭振和弯振信号分析,直观准确地表现了弯扭信号的本质特征。Hilbert谱图中清楚显示了次同步谐振发生时轴系扭振和弯振频率、幅值随时间变化的情况,揭示了轴系弯扭振动相互影响、相互作用的规律。更多还原

【Abstract】 With the development of electric power, the problem of vibration on turbo generator shafts stands out. The electric faults and operation can bring the impact which makes network oscillate and shaft torsional vibration. Shaft torsional vibration can produce serious mechanical damages to the unit, even a mechanical failure in the shaft. On the other hand, flexural vibration and torsional vibration have relation, and they are interactional and influencing. Because of on-line limit and danger, turbine generator simulated test is studied. Therefore, the dissertation has focused on several crucial problems in this field, the main outcome of our research includes:This paper based on Finite Element Method (FEM) analyses the characteristic of torsion vibration for turbine generator simulator shafts. The result of computeration is close to that of torsional vibration responsed test. The test results show that network faults or operations can stimulate torsional vibration of the shafts in different degree, and three-phase short-circuit fault makes the strongest torsional vibration.Based on a Jeffcott rotor system in imbalance and misalignment with rigid support, the differential equations of coupled vibrations are established. Mass unbalance is necessary condition of coupling. The analysis of bending and torsion characteristics of the test shows that the shaft flexural vibration and torsional vibration are interaction with each other, and torsional vibration can inhibit the complex rotor exercise.The test of flexural vibration and torsional vibration on simulator shafts during network impacts is finished. The important datas have been acquired. The result of test analysis is in the followling: Because of interaction of flexural vibration and torsion vibration, it is discovered that 1X, 2X and N/3X frequencie components exist in spectral diagram of torsion vibration and the amplitudes of 1X and 2X frequency in spectral diagram of flexural vibration have changed.Subsynchronous Resonance is tested on the line which has series compensating capacitance. The test discovered that torsion vibration can restrain the complex motion of flexural vibration. When mechatronics coupling Subsynchronous Resonance (SSR) happens, the 1X, 2X and N/3X frequencie components are disappeared. The first natural frequency of tosion vibration which is complementary with the resonance frequency is found. From frequency diagram of flexural vibration, it is revealed that the vibration amplitude of 1X frequency decreases and that of 2X frequency disappears. The relation between flexural vibration and torsional vibration is revealed in this paper. And it is diacovered that the motion characteristic of torsion is similar with that of flexural vibration. Useful information for fault diagnosis is provided by the coupled characteristics.The characteristics of flexural vibration and torsional vibration are significant to diagnosis of the rotor system.The Hilbert-Huang Transform (HHT) method is studied, and the HHT is used to analyse flexural vibration and torsional vibration signals in high compensation degree. The Hilbert-Huang time-frequency analysis has more true and distinct time-frequency distribution. From HHT analysis of the experimental data, it is concluded that the HHT time-frequency analysis is more accurately showing the essential characteristics of signals which provides a basis for flexural vibration and torsional vibration fault diagnosis.更多还原