Hydraulic turbine generator sets are crucial for harnessing water energy. However, the nonlinear phenomena resulting from the combination of unbalanced magnetic pull (UMP) and oil film forces remain unclear. A mathematical model of the rotor-bearing system is introduced to investigate the effects of UMP and the nonlinear oil film force on system. The UMP and nonlinear oil film force are derived from the air-gap magnetic energy and short bearing theory, respectively. The proposed model is verified by the stability experiments of hydraulic turbine generator set in the idling, no-load, and load conditions. The results show that, firstly, the system turns unstable for oil whip and oil swirl, and which experiences bifurcation and undergoes dynamical motions such as period-1 to period-5, quasi-periodic, and chaotic motions. Then, at moderate speeds, the rotor eccentricity has the greatest effect on the bifurcation at idle. While the nonlinear characteristics of the system are most sensitive to the rotor eccentricity at loaded condition. Finally, the existence of UMP reduces the instability caused by oil film forces.

The technology of using galloping piezoelectric energy harvester (GPEH) to obtain low velocity hydrokinetic energy has been developed. The surface roughness of the bluff body can affect the performance of GPEH and can be designed to suit requirements. This paper investigates a GPEH with two bluff bodies in elliptical cylinder shape and different surface roughness is considered. The vorticity and pressure with different surface roughness are analyzed by numerical simulation. The quasi-steady-state assumption is applied to obtaining hydrodynamic force. A piecewise distributed parameter model of GPEH is established and the approximate analytical solutions for model is derived. The related experiments are conducted and the results verify the model. The amplitudes of elliptical cylinders with short diameters of 20 mm and 25 mm are reduced by 22.05% and 31.08%, respectively, when surface is changed from its original state to a roughness of 6.3 mu m. When flow velocity increases from 0.49 m/s to 0.55 m/s, the decline ratio in maximum output power falls from 61.35% to 43.6% for short diameter of 20 mm and from 88.15% to 54.55% for short diameter of 25 mm. Additionally, the surface roughness is positively correlated with the onset velocity and has an effect on optimal resistance.

动静碰磨是转子系统最常见的故障之一,通过滑动轴承双转子试验台对转子系统碰磨故障进行研究.采用尼龙和黄铜材料制成碰磨装置进行试验,并对不同进口油压的试验结果进行分析.发现随着转速的升高,振幅增大,碰磨导致系统行为更复杂;当滑动轴承进口油压增大时,转子系统振幅减小,系统从多周期运行状态变为拟周期运行;进口油压不同时,振幅随转速的变化趋势基本相似,在低转速时水平方向和竖直方向的振动幅值基本重合,高转速时水平方向的振幅大于竖直方向;转子系统发生碰磨时,尼龙材料的最小极径值大于黄铜.当转速超过临界值,尼龙材料碰磨时系统的振幅远大于黄铜材料.

Abstract The unbalanced mass of the rotor-bearing system may cause abnormal vibration of the rotor-bearing system, which may affect the safe operation of the system in severe cases. In this paper, the rotor-bearing system fault simulation test bench and MADYN 2000 were used to test and simulate the single-disk shafting rotor mass unbalance fault. The research analyzes the influence of speed, unbalanced mass, support stiffness, and phase of unbalanced mass on the vibration response of the rotor-bearing system. The results show that when the speed is higher than the first-order critical speed, after the rotor starts, the amplitude gradually increases with the speed, reaches the peak at the first-order critical speed, and then gradually decreases to a stable value. Due to the anisotropy of the bearing support, the rotor has different amplitudes in each direction, but the change trend is the same, the support stiffness is small, and the stable value is reached faster. When the rotation speed and the unbalanced mass phase are the same, the rotor amplitude and the rotor unbalanced mass have a linear relationship. When the speed and unbalanced mass are the same, the rotor amplitude fluctuates with the change of the loading phase, and the fluctuation period is π. The research results have certain reference significance for the fault diagnosis and dynamic characteristics analysis of the unbalanced response of the rotor-bearing system.

Turbogenerator sets, the indispensible rotating machinery in thermal power plants, can be simplified into a dual-rotor bearing system. In this case, its nonlinear phenomenon largely results from the unbalanced magnetic pull (UMP) and the nonlinear oil film forces, which, however, are not well understood. In this study, a mathematical model for a dual-rotor bearing system is established, the effects of the UMP and the oil-film forces on its nonlinear phenomenon are investigated creatively. Of which, the UMP force is initially calculated by the integration of the air-magnetic energy, and the short journal bearing assumption is employed to derive the oil-film force. The fitness of the developed model is validated through the stability experiments of a 660 MW turbogenerator set. Results indicate that in the idling condition, nonlinear phenomenon of the system can be described as the period-1 and quasi-periodic motions as the rotational speed rises. At low speeds, the amplitude of oil whirl appears. With the rising rotational speed, the oil whirl turns into oil whip in the second quasi-periodic. Interestingly, the electromagnetic force can greatly alleviate the system amplitude and enhance its stability considering the UMP force. The nonlinear effect of air-gap distance of the system under load conditions is also investigated. The system is still in the quasi-periodic state with the increasing air-gap distance at low/high speed. But the system is still unstable owing to oil whirl/whip and UMP force, causing the system experiences multiple states and becomes more stable at the intermediate speed.

As a highly widespread and practical construction, it is vital to investigate rotor bearing system’s structure, components, and faults in order to enhance functioning performance. The dual-segment single-span rotor bearing system is explored experimentally in this work. Case studies of systems with cylindrical lubricated bearings and elliptical lubricated bearings are investigated under normal operating conditions and angular misalignment faults. Through comparative analysis, the findings demonstrate that a misalignment defect increases the displacement of a dual-segment single-span rotor bearing system by 1.2–1.6 times when compared to the normal operating state. According to the instability factor distribution, the stability of system with elliptical lubricated bearings is 130–190% higher than that of cylindrical lubricated bearings. On the contrary, the system with cylinder lubricated bearings performs worse under normal operating conditions than the two examples under misalignment conditions. Furthermore, for the case of an angular misalignment fault, 2X, 3X, and 4X frequency component excitations produce relatively larger system disturbances in 1500–2500 rpm rotating speed region, 1000–2000 rpm rotating speed region, and 1000–1500 rpm rotating speed region of the system, respectively.

To guarantee the safe and stable operation of wind farms, this article establishes a backstepping sliding mode fault-tolerant controller for the wind turbine system to surmount uncertain problems, including actuator gain–bias faults, system modeling errors, and external stochastic disturbances. The nonlinear disturbance observer is employed for the stochastic disturbances, which can online estimate and compensate the external disturbance term. In addition, the backstepping control strategy is introduced to reduce the complexity of fault-tolerant controller design. Subsequently, combining the backstepping control algorithm and nonlinear disturbance observer, a disturbance observer-based backstepping sliding mode fault-tolerant control approach is applied for the wind turbine system. Thereinto, the terminal attractor is employed, which is mainly utilized to improve the convergence rate of the sliding surface and reduce the chattering phenomenon. The stability of the wind power closed-loop control system is rigorously verified via Lyapunov stability theory, which can obtain satisfactory control performance. Finally, numerical simulation results demonstrate that the proposed control approach can guarantee that the system state quickly reaches stability within 6–8 s, and the steady-state adjustment time is greatly reduced to 50%–62% when compared with the proportional–integral–derivative control and sliding mode control.

调压室是水电站输水系统缓解水击波影响,进而满足机组调节保证要求的关键建筑;调压室的设置条件、临界稳定断面和位置是工程设计阶段需科学合理确定的3个关键指标.建立考虑上游调压室和水头损失的水轮发电机组调节系统非线性模型,引入Hopf分岔理论判断系统的分岔特性;依据系统的稳定域,提出调压室的设置条件和临界稳定断面判别方法;分析调节系统水流惯性时间常数和水头损失系数对系统稳定性的影响,确定调压室的合理位置.实验结果表明,所提方法可依据系统Hopf分岔特性判别调压室设置条件、临界稳定断面位置,为工程中关于调压室设置的设计提供了理论支撑.

混流式水轮机的尾水管压力脉动作用力对机组动态特性有直接影响,该作用力的最主要特征指标为频率及幅值.传统公式法不能反映出主频与负荷效应的关系,因此文中着眼于对全负荷段尾水管压力脉动频率计算方法的研究,并且结合其对机组稳定性运行的影响效果进行了深入探讨.从尾水管涡带产生的机理出发,推导全负荷段尾水管压力脉动频率的计算公式,并结合在2种不同补气条件下的实测数据,对涡带特性进行深入研究,阐述了涡带对机组运行品质的影响效果.对比在2种补气工况时的实测结果,发现在压力脉动作用较为明显的负荷区间内,全负荷段压力脉动计算方法的计算结果与试验结果贴合程度较高,说明该方法可以较为准确地反映实际运行特性.补气能减少涡带的主要原理在于其能削弱脉动的相对幅值,而对脉动频率无大的改变,这对提升机组稳定性运行的效果有着直接的影响.研究结果对于分析水电机组动态特性有着积极的意义.

针对发电机端部振动问题,研究了机组端部的模态特性,分别探讨了3种弹性模量的变化对机组振动特性的影响程度.先对发电机端部线棒进行参数化建模,然后利用FEM模态分析方法进行计算,对比分析计算结果,得到20阶临界频率及振型,划归振型的危险变形区域.通过对比不同工况下振型、临界频率,得出发电机定子端部线棒的典型振型,分析了对应的临界频率与弹性模量同向变化的规律,计算结果与现场检测数据相符,验证了计算方法的有效性.

水轮机调速系统厂家众多,逻辑、型式及模式命名规则多样,不利于技术交流、运行控制及管理.研究了当前主流水轮机调速系统的控制逻辑及模式命名规则,并提出了标准化建议;分析了一次调频与自动发电控制系统主流协调策略的优缺点,提出了"同向叠加,反向闭锁"优化控制逻辑,并结合实例进行了验证测试;分析了一次调频关键参数对水轮机调速系统性能的影响,并针对实际案例给出了参数优化方法;研究了水轮机调速系统建模方法,基于分环节辨识,对调节器控制系统、随动系统、水轮机三大环节建立了精确数学模型,并对整体模型进行了校核验证.水轮机调速系统控制逻辑制定、一次调频参数优化、调速系统仿真建模三者须有机结合,共同保证其性能满足相关标准及源网协调各项技术要求.

针对低转速工况下转子-轴承系统小裂纹识别难的问题,提出Hilbert-Huang变换谱和边际谱分析的方法.分别建立刚性支承及轴承支承的裂纹转子模型,比较二者频谱差异,并采用四阶Runge-Kutta法求解重力占优背景下裂纹转子-轴承系统动力学方程;对时域信号进行经验模态分解,提取其IMF分量,计算各IMF分量的HHT谱及边际谱,并对无裂纹和小裂纹情况进行分析.结果表明,对于受非线性油膜力影响的裂纹转子-轴承系统,HHT方法能够很好体现裂纹刚度随时间变化的过程;通过EMD方法分解出的IMF分量,在小裂纹、低转速下对裂纹的变化有很好的敏感性,能有效识别转子-轴承系统的小裂纹故障.

鉴于不同类型的电磁力会对转子的稳定运行产生影响,从实际水轮发电机组运行特性出发,利用变阶数微分方程对发电机转子系统进行参数化建模,选定变步长求解器进行计算,结合轴心轨迹图及频谱图分析了不同电磁力对轴系摆度的影响,分别探讨了两种气隙对机组轴系摆度的影响程度.对比两工况的计算结果,发现均匀圆周电磁力有助于提高转子运行的稳定性;而在发电机几何不对中而引起的非均匀电磁力作用时,转子的运行状况有较为复杂的变化,不利于机组安全稳定运行,计算结果与现场检测数据互相印证.

The uneven air gap between the inner cavity of the stator and rotor's outer circle is one of the main vibration sources of large hydro-generator sets. Unbalanced magnetic tension between the stator and rotor forms a frequency-exciting disturbance force on the rotor and stator. In this paper, in order to explore the relationship between the uneven air gap and the magnetic field strength as well as electromagnetic stress, magnetic induction intensity of inner air-gap magnetic field of the generator and the stress on the rotor surface are analyzed for six working conditions of the hydroelectric generator, including centering and eccentricity of the rotor. The influence of the hydroelectric generator's air gap change rotor pole stress is studied with finite element software based on the structure of the generator.

In this paper, the influence degree of eccentricity distance and guide bearing stiffness change on the vibration characteristics of the unit under the condition of rotor mass misalignment is discussed respectively, and the modal characteristics of the unit are studied for the problem of generator mass eccentricity. First of all, the guide bearing is parameterized, the whole axle system modeling is calculated by FEM modal analysis method, the results of the analysis obtain the first 10th order critical frequency and vibration mode analysis results, further determine the danger point of displacement deformation concentration. Comparing the vibration type, critical frequency and center vibration trajectory of the guide bearing under different constraint conditions, the characteristics of the unit vibration caused by the rotor quality is: the axis tile gap is gradually enlarged due to the eccentric rotation of the rotor of the unit, and the vibration characteristics of the main frequency in the unit vibration signal are unchanged. The results are confirmed by field inspection data.

针对南网某700 MW火电机组厂用电率不平衡而导致的进相运行能力不足问题进行了案例分析和计算.围绕厂用电压水平给出了厂用电调整优化策略,在手算和PSCAD仿真中对优化后的厂用电水平进行了进相仿真模拟,验证了厂用电调整措施的正确性,并针对类似问题提出评价策略和防范措施.

针对发电机质量偏心问题,分别探讨了偏心距离及导轴承刚度变化对机组振动特性的影响.首先对导轴承进行参数化处理,整机轴系建模后,通过FEM模态分析方法计算得到前10阶临界频率及振型的模态分析结果,进一步确定位移变形集中的危险点.然后对比不同约束条件下振型、临界频率、导轴承中心点振型轨迹,获得转子质量不对中造成的机组振动特性为因机组的转子偏心旋转造成轴瓦间隙逐步扩大,而机组振动信号中主频不变,计算结果与现场实际测量数据一致.

在较小电网中运行的大容量机组,调速系统在各种模式下的稳定运行能力与电网安全密切相关.文章通过分析果多电站机组在调试期间发生的导叶手/自动切换中的异常动作,提出调速器控制的优化方案,通过仿真对可行性进行分析,并将优化方案投入生产使用.优化后的机组性能良好,能够满足长期安全稳定运行的需要.

针对BP神经网络收敛速度慢和易陷入局部极小值等不足,通过改进遗传算法,显著提升遗传算法的全局寻优能力,进而优化BP神经网络初始权值和阈值.结合工程算例,采用正交法设计参数样本,利用边坡工程的有限元正分析模型计算出反演分析所需的样本,建立基于改进的GA-BP网络算法反分析模型,经过网络训练,得到符合实测效应量值的反演参数值,对比GA-BP网络算法和改进GA-BP网络算法的反分析模型结果可知,改进GA-BP网络算法反分析模型在解的稳定性和求解精度上均得到了较大提高.研究成果可供类似工程参考.

将发电厂的差动保护按光纤差动保护、母差保护、变压器差动保护、发电机差动保护进行分类,分析不同保护极性配置的典型特点,针对不同特点给出校验方法,并对不同校验方法的优劣进行评价.利用此方法,可经济、有效地解决差动保护的极性校验问题,保证主设备和继电保护的可靠稳定运行.