大型转子临界转速下现场动平衡试验

汽轮机转子在通过临界转速时会出现强烈振动,当不平衡量超过标准时导致停机。为了使机组能顺利启动,应对转子临界转速下的动平衡给予足够重视。介绍了转子的临界转速、振动特点及测量方法,分析了影响临界转速下振动响应的主要因素,给出了汽轮机转子临界转速下的动平衡试验方法,并得出相应结论,对今后的临界转速下转子的动平衡试验具有重要意义。     

论影响汽轮发电机组临界转速的因素

较为详细地介绍了汽轮发电机组临界转速产生的机理、影响临界转速的各种因素、临界转速的测量及减小通过临界转速时轴承振幅的措施。     

发电机转子的临界转速

本文的目的是说明不同设计参数对发电机临界转速的影响,并阐明所谓"临界转速"的意义。根据作者的经验,"临界转速"有许多不同的意义或定义。因此,同一物体的临界转速值也不尽相同。为此作者提出了"临界转速"的定义。     

多自由度永磁同步电机转子动力学特性分析

多自由度永磁同步电机含有球壳型转子,电机额定转速接近临界转速时,电机会产生多重共振,影响电机正常运行;电机转子转速需穿越1阶模态的临界转速,工作在1阶模态临界转速和2阶模态临界转速之间的安全范围。根据转子系统动力学特性,建立自由状态下的转子数学模型,对有限元法与解析法进行对比分析;分析了转子陀螺效应对临界转速的影响,并进行了转子轴承刚度对临界转速是否有影响的有限元验证;测试了不同转子轴承刚度情况下,弯曲模态与形变位移之间的关系;通过实验验证球形转子的转速与振幅之间的关系,总结出相应的规律,为该类电机的优化设计和控制提供了理论依据和数据。     

大功率高速永磁电机柔性转子系统模态分析

高速电机的转速高、转子细长,与常速电机相比接近临界转速的可能性大大增加,当电机额定转速接近临界转速时,电机会发生剧烈的振动,甚至使转子损坏。大功率高速电机的转子长度远远大于转子直径,很难设计为刚性转子,需要穿越1阶临界转速,工作在1阶临界转速和2阶临界转速中间的安全区域,而这个安全区域的范围却很小,这对大功率高速电机转子系统的动力学设计带来了极大的困难。基于一台1.12MW、18 000r/min的高速永磁电机,对转子系统的动力学特性进行理论分析,对有叶轮和无叶轮状态下的转子模态和临界转速进行计算,分析轴承支承刚度、陀螺效应以及转子主要尺寸对临界转速的影响,并通过样机进行了实验验证,总结了相应的规律,为大功率高速电机挠性转子的设计提供了参考。     

基于多柔体动力学分析的滚筒洗衣机临界转速研究

本文从多柔体动力学分析入手,计算了滚筒洗衣机的临界转速,并与不考虑陀螺效应影响的模态分析固有频率进行比较分析,得出结论:考虑陀螺效应后,滚筒洗衣机临界转速降低,基于安全设计,临界转速分析应考虑陀螺效应影响,并由此提供了一种求解洗衣机临界转速的方法。     

防爆电动机转子系统临界转速分析

采用传递矩阵法对YB2电动机转子系统进行了分析,详细地阐述了复杂转子结构的模型等效方法和数值处理过程,该转子的临界转速计算结果表明设计的转子一阶临界转速接近工作转速而可能引起共振,建议将该轴转子长度改短和增加轴颈,提高其一阶临界转速。     

支承参数对转子临界转速的影响研究

以某转子为研究对象,基于有限元分析软件ANSYS建立该转子的临界转速,计算有限元模型。通过固定其他支承参数逐渐改变支承主刚度与主阻尼的方式,对该转子进行临界转速计算,获得采用不同支承参数的转子临界转速。分析了转子临界转速随支承主刚度与主阻尼的变化规律,结果表明:支承主刚度小于200 GN/m时,该转子的各阶临界转速随主刚度的变大而升高的趋势明显,支承主刚度大于200 GN/m时,继续增大主刚度对该转子临界转速的影响较小;支承主阻尼在一10~10 MN·s/m内取值,对转子临界转速无明显影响。分析结果可为该转子的设计提供参考。     

发电机的现场平衡

大多数发电机的振动是由不平衡引起的。动平衡是消除振动的主要手段。本文以柔性转子平衡的原理为指导,依据临界转速的不同,将发电机分为两类:第一类的工作转速在一、二阶临界转速之间;第二类的工作转速在二、三阶临界转速之间。文中结合具体的实例,介绍了这两类转子的平衡方法。     

特别考虑临界转速时的转子动态特性

分析了水轮发电机组郭的不同结构设计参数对其临界转速所产生的影响。指出在转子临界转速计算中,对假设的条件,往往有不同的考虑,因而对同一转子的计算可得出不同的临界转速。阐述了水轮发电机和发电电动机转子的动态特性、说明采用可调式导轴承是保证机组平稳运行的重要措施。最后对大型水电机组转子第一临界转速的方法提出了建议。     

基于扩展卡尔曼滤波算法的异步电机转速辨识性能评估

利用扩展卡尔曼滤波器（EKF）,将转子转速看成一个状态量,通过测量电机定子侧的端电压和电流在线估计电动机转子速度。通过较全面的仿真实验对比分析,研究了采样周期、滤波器参数和电机参数对转速在线估计性能指标的影响。对比结果发现,该方法进一步优化了用扩展卡尔曼滤波器对电动机转速的辨识。     

甩负荷试验转子转动惯量计算方法研究

通过甩负荷试验测取汽轮发电机转子转动惯量的计算方法不一，结果整别较大。针对甩负荷试验转子飞升曲线波动的特点．论述了汽轮发电机转子转动惯量测取原理。以某国产引进型300MW机组甩负荷试验的实测数据为基础．对转速飞升曲线采用3类函数进行了拟合，求取转子的初始飞升速率，但结果差别很大：在对转子飞升过程机理分析的基础上．提出了采用2点邻近点平均或快速傅立叶FFT滤波(平滑)对数据进行处理．再用调节汽门延迟关闭时间范围内转速线性拟合的方式求取转速初始飞升速事。该方法得到的曲线仍然呈现波动．但对甩50％和100％负荷试验计算的转子转动惯量取得根好的一致性。     

变桨距型双馈风电机组并网控制及建模仿真

变桨距型双馈风电机组在并网过程中,转子励磁控制虽然具有良好的定子电压调节效果,但是对转子转速缺乏控制。针对该问题提出了结合变桨距系统调整转子转速,共同完成并网的方案。由于双馈发电机并网前后的控制策略不同,分析了控制系统间无扰切换的方法。采用分开建模、分时仿真的思路建立了风电机组模型,实现了风机并网全过程仿真,研究结果证明了本文所提方案的有效性。     

Rotor resistance adaptation for sensorless vector-controlled induction machines

The vector control method is widely used for induction motor drives. In these applications, a rotational transducer such as a shaft encoder is used. A rotational transducer, however, cannot be mounted in some cases, such as motor drives in a hostile environment or high-speed motor drives. Several sensorless vector-controlled induction machine drive methods have been proposed. These methods have the disadvantage that rotor resistance variation causes errors in the estimation of the motor speed. It is difficult to estimate the motor speed and the rotor resistance simultaneously, because the equivalent rotor resistance is the ratio of the rotor resistance to the slip at steady state. Therefore, we have proposed a method of simultaneously estimating the motor speed and the rotor resistance of an induction motor by superimposing ac components on the field current command. This paper presents a modified method of the rotor resistance adaptation. The validity of the proposed method is verified by experiments. © 1998 Scripta Technica, Electr Eng Jpn, 125(2): 65–72, 1998     

Speed sensorless field-oriented control of induction motor withrotor resistance adaptation

Several field-oriented induction motor drive methods without rotational transducers have been proposed. These methods have a disadvantage that the rotor resistance variation causes an estimation error of the motor speed. Therefore, simultaneous estimation of the motor speed and the rotor resistance is required. This paper presents a method of estimating simultaneously the motor speed and the rotor resistance of an induction motor by superimposing AC components on the field current command. The validity of the proposed method is verified by simulation and experimentation     

基于四因子变极性控制的磁悬浮高速电机刚性转子同频振动抑制

变极性切换控制(polarity switching control,PSC)可有效降低主动电磁轴承(active magnetic bearing,AMB)高速电机刚性转子系统在刚体平动模态前后的同频不平衡振动,而且通过引入干扰观测器可降低极性切换瞬间对系统产生的冲击。然而,当刚体锥动模态也存在时,简单PSC已不能保证AMB刚性转子系统在包括刚体平动模态和刚体锥动模态在内的全转速范围的同频不平衡振动抑制,而且系统的稳定性也会发生变化。为了抑制AMB刚性转子系统在全转速范围内的不平衡同频振动,提出一种基于四因子变极性控制(4-factor polarity switching control,4-FPSC)的同频不平衡振动抑制方法。4-FPSC需要调节4个极性因子,采用2次PSC,分别抑制2个刚体模态各自前后的同频不平衡振动,而且切换瞬间不会对系统产生冲击,避免干扰观测器的设计。仿真和实验结果证明基于4-FPSC的同频振动抑制方法能有效地抑制AMB刚性转子系统在包括2个刚体模态在内的全转速范围的同频不平衡振动。     

计及转速平滑恢复的双馈风电机组自适应频率控制策略

为解决现有双馈风电机组频率控制策略不能充分利用转子动能支撑电网频率及风机转速恢复造成的二次频率冲击问题,提出了一种计及转速平滑恢复的双馈风电机组自适应频率控制策略.首先在电网频率支撑阶段,借助指数函数将风电机组频率控制系数和电网频率偏差建立耦合关系,使频率控制系数随频率偏差增加而变大,从而使风电机组在频率支撑阶段释放更...     

Harmonics and inter harmonics estimation of DFIG based standalone wind power system by parametric techniques

This paper presents application of parametric techniques (Estimation of signal parameter by rotational invariance techniques (ESPRIT), Root multiple signal classification (Root MUSIC)) for the estimation of harmonics/inter harmonics produced by wind generator under constant, variable rotor speed, load imbalance. Accuracy of estimation by parametric techniques is checked on synthetic signal as well as signal extracted from DFIG based standalone system with constant rotor speed and balanced load condition. Further sliding window concept is applied to parametric techniques to estimate the harmonics/inter harmonics under variable rotor speed and load unbalance. Series of simulation results demonstrate the advantages of the sliding window ESPRIT over sliding window Root MUSIC in the estimation of harmonics and inter harmonics under variable rotor speed as well as load unbalance condition.     

Sensorless vector controlled converter for variable speed wind generation system using an induction generator

This paper proposed two types of speed sensorless converters that can control rotational speed and electric power. One is based on a slip frequency control system. The other is based on a vector control system. The rotational speed of the wind turbine is estimated with the phase voltage and phase current of the induction generator by the adaptive rotor flux observer. The estimated wind turbine rotational speed ω_r^est is used as the feedback of the speed control loop in the converter control system. Also, the estimated rotor flux ?_2d^est is used for the vector control. The simulation results confirm that both of them perform satisfactorily under the speed sensorless operation. The method based on the vector control system generates more electrical energy than does the method based on the slip frequency control system. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(4): 62–75, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20323     

Development of interior permanent magnet motors reducing harmonic iron losses under field weakening control

In this paper, we present the development of interior magnet motors reducing iron loss at high rotational speed under the flux weakening control. The rotor core and magnet shapes are determined by the automatic numerical calculation using combination of the optimization method and the adaptive finite element method. The optimized motor is manufactured to prove the effectiveness by the measurement of the iron loss. Both results of the calculation and the measurement indicate that the iron loss of the proposed motor at the high rotational speed under the flux weakening control is reduced by half compared with the initial rotor shape while the torque is nearly constant. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(3): 59–66, 2009; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20827