异步电动机起动过程中转轴上的扭矩振荡现象研究

异步电动机带大惯性负载直接起动时,转轴上会产生很大的扭矩振荡.详细分析了产生扭矩振荡的原因,探讨了软起动对扭矩振荡的影响.仿真结果表明,采用晶闸管软起动装置可以在不影响电动机起动性能的前提下,有效抑制转轴上的扭矩振荡.     

异步电动机起动过程中转轴上的扭矩振荡现象研究

异步电动机带大惯性负载直接起动时，转轴上会产生很大的扭矩振荡。详细分析了产生扭矩振荡的原因，探讨了软起动对扭矩振荡的影响。仿真结果表明，采用晶闸管软起动装置可以在不影响电动机起动性能的前提下，有效抑制转轴上的扭矩振荡。     

风力发电机组轴系扭振模式稳定性分析

针对带串联补偿装置的并网双馈风力发电机组轴系扭振模式的稳定性,搭建了风力发电机轴系的三质量块等效模型,用小扰动法分析了轴系不同质块间的扭振模式。基于矩阵束算法辨识串联补偿度对风电场发电机组轴系扭转模式稳定性的影响,分析表明在故障情况机组轴系可能发生暂态扭矩放大。在PSCAD/EMTDC中搭建了某实际风电场中风力机轴系和发电机电磁暂态模型以及电网其它部分模型。仿真结果表明:电网故障会引发轴时系扭振模式不稳定现象,同时验证了串联补偿影响轴系扭振模式的稳定性。     

A Microprocessor-Based Motor Speed Regulator Using Fast-Response State Observer for Reduction of Torsional Vibration

A new state observer, which is suitable for microprocessor-based motor drives, and its application to suppression control of shaft torsional vibration are described. A distinct feature of the state observer is that a fast-response load torque estimation is obtained by processing the detected motor current and the encoder output pulses by a hardware circuit for each encoder pulse generation. Suppression control of the shaft torsional vibration is achieved by calculating a compensation signal from the estimated load torque with the microprocessor software. A microprocessor-based speed regulator for dc motor drives, which utilizes the state observer and suppression control of the shaft torsional vibration, was developed for evaluation purposes and tested with a 15-kW dc motor. The load torque of the motor can be estimated accurately, even with a 15-Hz vibration frequency, and the torsional vibration can be eliminated with the proposed suppression control.     

Start-Up Torques in Synchronous Motor Drives

During run-up as an induction motor, the torque produced by a synchronous machine has oscillating components in addition to the natural frequencies of torsional oscillation of the complete drive system so that the shaft torque may differ substantially from the motor electromagnetic torque. The latter can be divided into four components: 1) a unidirectional or accelerating component, 2) an oscillating component due to magnetic saliency and nonuniform rotor windings, 3) oscillating components due to higher harmonics of air gap permeance and winding magnetomotive force, and 4) components caused by switching the supply. In addition, slot effects and magnetic saturation may also lead to oscillating torque components. The factors affecting the magnitude and frequency of these components are discussed and related to recordings of actual shaft torque.     

控制系统延迟对轴扭振的影响

控制系统中的轴扭振会引起系统控制量的振荡,加大机械传动装置磨损,甚至会导致传动轴断裂。在工业应用中,多采用陷波滤波器抑制轴扭振,而陷波频率的选取通常未考虑控制系统延迟因素。基于电机角速度增量、轴转矩增量和电机电磁转矩增量的相位图,分析了控制系统延迟对轴扭振频率的影响。仿真结果对分析结论给予了验证。     

电网短路故障下双馈风电机组传动链扭振响应

电网故障引起的电磁转矩波动易造成风电机组轴系扭振疲劳损耗,严重时会造成轴系故障,有必要研究不同类型电网故障下风电机组传动链扭振响应及其对关键部件的影响。首先,采用集中质量法,考虑叶片柔性建立了风电机组传动链四质量块模型,基于小信号模型,采用模态分析法对风电机组传动链扭振特性进行分析。其次,为了表征不同故障类型对风电机组传动链轴系扭振的影响,在双馈发电机电磁暂态模型的基础上,推导了电网对称与不对称故障下电磁转矩表达式。最后,基于四质量块传动链模型,仿真分析了单相、两相和三相接地电网故障对机组传动链扭振响应的影响。结果表明,不同类型电网故障会影响不同传动链扭振频率及其不同关键部件;三相接地电网故障引起的传动链扭振幅值大,齿轮箱和发电机转子间轴上传递转矩可以较全面反映扭振响应频率;与传动链其他部件相比,发电机转子受到电网故障影响更大。     

A method for reducing transient torsional stresses ofturbine-generator shaft segments

The author presents a method for reducing transient torsional stresses of steam turbine-generators in series-capacitor-compensated power systems, which are equipped with ZnO varistor schemes. The fundamental concept is to reduce the coupling between the electrical network and the shaft system with respect to the troublesome torsional frequency. The electrical network and the rotating shaft system are coupled through the generator air-gap torque. This coupling can be attenuated by unbalancing the network with respect to the phenomenon of torsional oscillations. This is achieved by setting the protective voltage levels of the three phases of a three-phase series capacitor at unequal values. The technical feasibility of the proposed method is demonstrated on a test system, using the BPA Electromagnetic Transients Program (EMTP) as the study tool. The impact of the proposed countermeasure on the transient torques of the system, as a result of different disturbances, is demonstrated. The limitations of the proposed method are discussed     

Torque Oscillations of Synchronous Motors Under Starting Conditions

Salient-pole synchronous motors develop an average torque and a twice-slip frequency oscillating torque during starting. If coupled to a complex mechanical system, with resonance in the oscillatory frequency range, severe stresses may result in shafts, gears, and couplings. The objective of the paper is to develop motor and mechanical system models, which can lead to the analysis of the torsional response of the motor load, and to avoid the use of specific motors that yield excessive values of stress or take steps to mitigate the oscillation magnitudes. The effect of the field discharge resistance was investigated.     

Starting Characteristics of Electric Submergible Oil Well Pumps

The electric submergible pump (ESP) consists of a centrifugal pump powered by a medium-voltage three-phase induction motor. Being constrained to operate within common well casings, the ESP is rather unique; for example, a 500-hp motor may be less than 6 in in diameter and more than 100 ft long. As such, its mechanical rotational behavior under starting conditions can be severe, and some actions normally thought to attenuate the severity can actually amplify it. Both analytic and experimental approaches to understanding the starting incident and its effects are presented. A model was developed to predict the electrical and mechanical conditions prevalent when starting with various types of reduced-voltage fixed-frequency starters. These include the solid-state soft starter, reduced-voltage starters using variable or switched series impedances and stepped-voltage starters. Direct on-line full-voltage starting was used as a base case. Model predictions for the various starting methods were compared against tests measuring transient speed, voltage, current, and torque. Test results indicate that some starting techniques can produce unstable operation, i. e., torsional vibration. In large horsepower ESP's shaft strength safety factor is reduced due to space limitations and torsional vibrations must be minimized to avoid breakage due to fatigue. Depending on the application, configuration of the ESP and adequacy of available power, good motor starter design can be crucial to reliability. Finally, it is believed that this work has direct applicability to the starting of many more common large induction motors.     

Speed control system and design of resonant system with disturbance observer

In industrial motor drive systems such as industrial plants and industrial robots, a torsional vibration often is generated because of the elastic elements in torque transmission. This vibration makes it difficult to achieve quick responses of speed and may result in damage to the plant. Such systems simply are modeled as a two mass system. The shaft torque feedback system with the disturbance observer, which is called “resonance ratio control,” is proposed to suppress the vibration for the two-mass system. In this paper, the design of controller gains in the shaft torque feedback system is examined considering not only the control performance such as the vibration suppression and dynamic responses, but also the robust stability against the noise and the model uncertainties. This paper shows the validity of the control system and the examinations by several experiments.     

无轴承绕线型异步电机瞬态响应的有限元分析及实验研究

无轴承电机集磁性悬浮与转矩驱动于一体,具有无摩擦、无磨损、无损耗、免维修、寿命长等独特优点,从根本上改变了传统的支承与传动形式.该文介绍一种无轴承绕线型异步电机,通过瞬态有限元分析法(TFEM)计算其径向力和转矩的瞬态响应,结果表明该无轴承电机可以同时产生支承转子重量的稳定径向力与恒定转矩,且其控制电流相互独立,与鼠笼型转子无轴承异步电机相比,前者能够产生更有效的径向力,且转矩不受径向力绕组电流干扰;并在基于SVM-DTC的磁悬浮异步电机悬浮子系统独立控制实验平台上加以测试,结果表明该系统能够实现了无轴承绕线型异步电动稳定悬浮.     

汽轮发电机组轴系扭振的独立模态空间鲁棒控制

提出在汽轮发电机组轴系扭振的独立模态空间控制回路中，采用H∞扭振模态观测器估计模态反馈信号。证明了独立模态空间控制器町以独立设计，而引入H∞扭振模态观测器对闭环系统极点分布的影响可以忽略不计。基于H∞控制理论导出了针对受控扭振模态设计的独立模态空间控制器的鲁棒稳定条件。另外，出于实际考虑，建议扭振控制转矩以发电机电磁转矩分量的形式实现，而将慢变的机械转矩看作干扰，提出了抑制其影响的H∞性能指标。在此基础上提出轴系扭振的独立模态空间鲁棒控制，并归结为带有闭环极点配置约束的多目标H∞综合问题。算例仿真表明，轴系扭振独立模态空间鲁棒控制策略是可行的、有效的。     

Torsional Coordination of High Speed Synchronous Motors?Part II

The increasingly frequent use of larger four-pole and six-pole synchronous motors to drive high speed equipment, such as compressors, has focused much attention on coordination of the motor and driven equipment system. A relatively straight forward analytical method of calculating the motor-developed air-gap torque from the d and q axis equivalent circuits is presented. The problem of relating air-gap torque to shaft torque is discussed briefly, and methods of experimentally determining both quantities are presented. A method of assessing the capability of a shaft section to withstand a given torsional duty is also presented.     

大型核电机组冷却剂屏蔽主泵动态模型及响应特性研究

为了提高核安全性,新型压水堆核电机组冷却剂主泵采用无轴密封式屏蔽电动机泵,但其转动惯量明显小于常规轴密封泵,因此具有不同的动态响应特性。针对屏蔽主泵转动惯量较小、对电压、频率波动敏感等特性,考虑运行过程中的摩擦转矩,建立了屏蔽主泵动态模型,并将其接入核电机组系统仿真模型。比较验证了主泵动态模型的有效性,并仿真分析了主泵惰转特性和频率、电压扰动响应特性及其对堆芯功率的影响。结果表明,摩擦转矩对屏蔽主泵半流量惰转时间有较明显影响,建模时应予以考虑;频率扰动对主泵转速、流量的影响比电压扰动更明显,在运行中应提高厂用电供电质量。     

转子开辅助槽削弱双层内置式永磁同步电机转矩脉动

针对双层永磁结构电机的气隙磁密在两层永磁体的交界处变化较快,其产生的谐波会增加转矩脉动,提出在转子表面开两组对称辅助槽的方法来改善电机的气隙磁密波形,削弱转矩脉动。以一台双层V型永磁结构电机为研究对象,在转子表面分别开两组椭圆形的辅助槽,通过优化辅助槽的位置、大小和形状,将电机的转矩脉动从15%降低至4.3%,验证了所提方法的有效性。     

无刷直流电动机特性有限元分析

本文在介绍汽车转向泵用无刷直流电动机结构的基础上,用有限元法分析计算了该永磁无刷电动机的磁场分布和静态特性,并利用静态计算所得参数分析计算了电动机起动和负载突变时的动态特性,得到的磁密分布波形和静态转矩特性为该种电动机设计使用提供了理论依据。     

考虑整机转矩控制的双馈风机轴系扭振机理分析及抑制策略

双馈风电机组轴系模型可等效为风力机质块经柔性轴与发电机质块连接,其轴系柔性较大,阻尼较低,现场存在轴系扭振现象.提出将整机转矩控制嵌入双馈风机两质量块数学模型中,并进行小信号线性化,得到适用于轴系动态特性分析的双馈风电机组机电小信号模型,基于该模型开展扭振机理分析和抑制策略设计.双馈风机轴系扭振本质原因是电磁转矩与发电...     

永磁转子偏转式三自由度电机磁场和转矩特性的计算与分析

永磁转子多自由度电机可实现输出轴的多自由度运动,简化电机机械系统的结构,提高传动系统的响应速度和定位精度,是国内外电机领域的一个研究热点。该文提出了一种蝶形永磁转子偏转式三自由度电机,基于有限元法建立了该电机的三维有限元模型,对电机转子磁场的分布进行了计算和分析,并与解析模型的计算结果进行了对比验证。在此基础上,计算并分析了该电机的自转转矩和偏转转矩,并与鼓形永磁转子偏转式三自由度电机的磁场和转矩进行对比分析,结果表明蝶形永磁转子偏转式三自由度电机可增大气隙磁通密度和自转转矩的幅值,有效改善和提高偏转转矩的幅值,并增加偏转运动的范围。最后,对样机进行了测试,并将实验结果与有限元及解析模型的计算结果进行了对比验证。     

基于电压空间矢量的电动汽车电驱动系统高效快转矩响应控制

针对电动汽车异步电动机电驱动系统效率优化控制引起动态响应速度下降的问题,提出一种用于动态过程的快速转矩响应控制策略.该方法充分利用目前电动汽车电驱动系统中应用广泛的矢量控制方案中已有的转子磁链和电磁转矩信号,结合直接转矩控制思想,在动态过程中通过选择适当的电压空间矢量,提高转子磁链和转矩响应速度.该方案突破了转子磁场响应慢的制约,使动态过程中电动机的电磁转矩迅速增大.实验结果表明,系统动态响应性能得到明显改善,该高效快转矩响应控制策略具有调节时间短、动态响应快的优点.