New-type Wound-rotor asynchronous motors Started by harmonics

Ⅰ. Preface Starting is one of the important topics of asynchronous mo-tors. Varied methods over a long period of time for improving thestarting characteristics of the asynchronous motors had beenadopted by domestic and foreign electrical engineers. The methodswhich innovate on the internal structure of the electrical motors soas to improve the starting characteristics fall into two kinds. The firstone is to change the structure of the stator winding of the motors, forinstance, the "star-delta" starting, the "prolonged side triangle"

Rotor Strength Analysis of High-speed Permanent Magnet Synchronous Motors

为了对转子进行有效的冷却，在满足电机电磁性能的前提下，可通过减小保护套的厚度来尽可能增大定转子之间的气隙，因而必须对保护套和永磁体进行强度校核。将转子受力状况简化为平面应变问题，在此基础上推导出了两层过盈配合、三层过盈配合转子的应力场、应变场、位移场的解析公式，并利用有限元方法验证了解析公式的正确性。归纳了高速情况下热套式永磁转子强度设计准则，为转子的优化设计提供了理论依据。以一台额定转速120kr／min、10kW的高速永磁同步电机为例，给出了两种常用过盈配合高速电机转子的强度设计方法。

Multi-objective Hierarchical Optimization of Interior Permanent Magnet Synchronous Machines Based on Rotor Surface Modification

To solve the problem of large torque ripple of interior permanent magnet synchronous motor(IPMSM),the rotor surface notch design method was used for V-type IPMSM.In order to accurately obtain the optimal parameter values to improve the torque performance of the motor,this paper takes the output torque capacity and torque ripple as the optimization objectives,and proposes a multi-objective layered optimization method based on the parameter hierarchical design combined with Taguchi method and response surface method(RSM).The conclusion can be drawn by comparing the electromagnetic performance of the motor before and after optimization,the proposed IPMSM based on the rotor surface notch design can not only improve the output torque,but also play an obvious inhibition effect on the torque ripple.

Investigation of Nonlinear PI Multi-loop Control Strategy for Aircraft HVDC Generator System with Wound Rotor Synchronous Machine

In order to enhance the transient performance of aircraft high voltage DC(HVDC)generation system with wound rotor synchronous machine(WRSM)under a wide speed range,the nonlinear PI multi-loop control strategy is proposed in this paper.Traditional voltage control method is hard to achieve the dynamic performance requirements of the HVDC generation system under a wide speed range,so the nonlinear PI parameter adjustment,load current feedback and speed feedback are added to the voltage and excitation current double loop control.The transfer function of the HVDC generation system is derived,and the relationship between speed,load current and PI parameters is obtained.The PI parameters corresponding to the load at certain speed are used to shorten the adjusting time when the load suddenly changes.The dynamic responses in transient processes are analyzed by experiment.The results illustrate that the WRSM HVDC generator system with this method has better dynamic performance.

Temperature Field Analysis of Mine Flameproof Outer Rotor Permanent Magnet Synchronous Motor with Different Cooling Schemes

Aiming at the problem of temperature rise of mine flameproof outer rotor permanent magnet synchronous motor,based on the fluid structure coupling method,the temperature distribution of motor under three cooling schemes of air cooling and water cooling are calculated respectively.For the structure I air cooling system,the influence of different number of heat sink on the maximum temperature rise and pressure drop of fluid channel is analyzed,and the parameters of heat sink are optimized.For the structure II air cooling system,the influence of setting fillet at the turn back of the fluid channel on the head loss in the fluid domain of the motor is analyzed,and the influence of different fillet radius on the head loss and the maximum temperature rise in the fluid domain is obtained.For the structure II water cooling system,the influence of different water flow speed on the maximum temperature rise of the motor is analyzed,and the influence of different assembly clearance of modular stator teeth and yoke on the maximum temperature rise of the motor is analyzed.The cooling effect and temperature rise distribution characteristics of the three cooling schemes are compared and analyzed.Finally,a water-cooled prototype is manufactured,and the temperature rise experiment is carried out,and the influence of the thermal deformation of fluid channel,stator yoke and stator teeth on the maximum temperature of the motor is analyzed.The results show that the calculated temperature field after considering the thermal deformation is closer to the experimental value,which verifies the accuracy of the calculation results,It also provides a reference for the selection and design of the cooling structure of the same type of PMSM electric roller.

Rotor Optimization for Synchronous Reluctance Motors

Rotor of Synchronous reluctance motor(SynRM)usually has multiple flux barrier structure for the purpose of higher electromagnetic torque and lower torque ripple.Two different strategies are used in this paper for rotor structure optimization and a compromised strategy for fully squeeze the potential of each related parameters is developed.Performance of resulted rotor structure is evaluated to verify the optimization procedure.

Permanent Magnet Assisted Synchronous Reluctance Motor with Asymmetric Rotor for High Torque Performance

Permanent magnet assisted synchronous reluctance motor(PMA-SynRM)is a kind of high torque density energy conversion device widely used in modern industry.In this paper,based on the basic topology of PMA-SynRM,a novel PMA-SynRM of asymmetric rotor with position-biased magnet is proposed.The asymmetric rotor design with position-biased magnet realizes the concentration of magnetic field lines in the motor air gap to obtain higher electromagnetic torque,and makes both of magnetic and reluctance torque obtain the peak value at the same current phase angle.The asymmetric rotor configuration is theoretically illustrated by space vector diagram,and the feasibility of high torque performance of the motor is verified.Through the finite element simulation,the effect of the side barrier on output torque and the Mises stress under the rotor asymmetrical design are analyzed.Then the motor characteristics including airgap flux density,back EMF,magnetic torque,reluctance torque,torque ripple,losses,and efficiency are calculated for both the basic and proposed PMA-SynRMs.The results show that the proposed PMA-SynRM has higher torque and efficiency than the basic topology.Moreover,the torque ripple of the proposed PMA-SynRM is reduced by the method with harmonic current injection,and the torque characteristics in the whole current cycle are analyzed.Finally,the endurance to avoid PM demagnetization is confirmed based on the PM remanence calculation.

Design of an Asymmetric Rotor Pole for Wound Field Synchronous Machines

This study proposes a novel asymmetric rotor pole design for wound field synchronous machines(WFSMs),which can achieve high saliency ratio and also low torque ripple.The key point is the optimal design of the asymmetric rotor pole with the inverse-cosine-shaped(ICS)plus reverse 3rd harmonic shaping.The asymmetric rotor pole can help to improve the average output torque by enhancing the saliency ratio.The reverse 3rd harmonic shaping on the rotor pole surface is mainly used to reduce the torque ripple.To certify the effectivity of the proposed design,three-phase 54-slot/6-pole 4.7kW WFSMs with uniform air gap and with non-uniform air gap shaped by the ICS plus optimum reverse 3rd harmonic are utilized as the basic model and referenced model for comparison.For the referenced model,the optimum amplitude of reverse 3rd harmonic is preferred as 1/6.Finally,all electromagnetic characteristics of the investigated machines are predicted by the finite-element method(FEM).The highest saliency ratio and comparatively low torque ripple have been verified.

Improved estimation of rotor position for sensorless control of a PMSM based on a sliding mode observer

This work proposes a new strategy to improve the rotor position estimation of a permanent magnet synchronous motor(PMSM) over wide speed range. Rotor position estimation of a PMSM is performed by using sliding mode observer(SMO). An adaptive observer gain was designed based on Lyapunov function and applied to solve the chattering problem caused by the discontinuous function of the SMO in the wide speed range. The cascade low-pass filter(LPF) with variable cut-off frequency was proposed to reduce the chattering problem and to attenuate the filtering capability of the SMO. In addition, the phase shift caused by the filter was counterbalanced by applying the variable phase delay compensation for the whole speed area. High accuracy estimation result of the rotor position was obtained in the experiment by applying the proposed estimation strategy.

Performance Description of Brushless Doubly-Fed Induction Machine in Its Asynchronous and Variable Speed Synchronous Modes

Brushless Doubly-Fed Machine has attracted considerable attention in recent years due to its advantages. It has the robustness of the squirrel cage induction machine, and the speed and power factor controllability of the synchronous machine as well as the absence of brushes and slip rings, and using a fractionally rated frequency converter. Hence, there are considerable benefits over the conventional machines, when the machine is applied to applications such as a wind turbine generator or high power adjustable speed drive. However, these benefits are obtained in slightly more complex structure, higher cost and larger dimensions in comparison to the conventional induction machine. This paper presents fundamental aspects of the three modes of operation of brushless doubly fed machine, i.e. simple induction mode, cascade induction mode, and synchronous mode. The investigation is performed by analyzing the spatial harmonic contents of the rotor magnetic flux density. The direct cross couplings between stator and rotor fields as well as, indirect cross coupling between stator fields by the special rotor of this machine is described. Furthermore, loss analysis of the machine in various modes is presented and the torque-speed curves for asynchronous modes are obtained. A 2-D magnetodynamic finite element model based on the D-180 4/8 pole prototype machine is extracted and simulated to verify the results.

Combined resonance of low pressure cylinder-generator rotor system with bending-torsion coupling

A nonlinear model of a low pressure cylinder-generator rotor system is presented to study sub-synchronous resonance and combined resonance. Analytical results are obtained by an averaging method. Transition sets and bifurcation diagrams are obtained based on the singularity theory for the two-state variable system. The bifurcation characteristics are analyzed to provide a basis for the optimal design and fault diagnosis of the rotor system. Finally, the theoretical results are verified with the numerical results.

Time-stepping finite element analysis on the influence of skewed rotors and different skew angles on the losses of squirrel cage asynchronous motors

To study the influence of skewed rotors and different skew angles on the losses of squirrel cage asynchronous motors,a 5.5-kW motor was taken as an example and the multi-sliced field-circuit coupled time stepping finite element method(T-S FEM)was used to analyze the axially non-uniform fundamental and harmonic field distribution characteristics at typical locations in the stator and rotor cores.The major conclusions are:firstly the skewed rotor exhibits a decrease in the harmonic copper losses caused by slot harmonic currents in the stator winding and rotor bars.Secondly,the skewed rotor shifts the non-uniform distribution of field in the axial direction,which leads to more severe saturation and an increase in iron losses.The heavier the load,the more pronounced the increase in iron losses.Furthermore,the influences of different skew angles on motor losses are studied systematically,with skew angles from 0.5 to 1.5 stator tooth pitch.It is found that the lowest total loss occurs at 0.8 stator tooth pitch,and the slot harmonics can be decreased effectively.

Artificial Monitoring of Eccentric Synchronous Reluctance Motors Using Neural Networks

This paper proposes an artificial neural network for monitoring and detecting the eccentric error of synchronous reluctance motors.Firstly,a 15 kWsynchronous reluctance motor is introduced and took as a case study to investigate the effects of eccentric rotor.Then,the equivalent magnetic circuits of the studied motor are analyzed and developed,in cases of dynamic eccentric rotor and static eccentric rotor condition,respectively.After that,the analytical equations of the studied motor are derived,in terms of its air-gap flux density,electromagnetic torque,and electromagnetic force,followed by the electromagnetic finite element analyses.Then,the modal analyses of the stator and the whole motor are performed,respectively,to explore the natural frequency and the modal shape of the motor,by which the further vibrational analysis is possible to be conducted.The vibration level of the housing is furtherly studied to investigate its relationship with the rotor eccentricity,which is validated by the prototype test.Furthermore,an artificial neural network,which has 3 layers,is proposed.By taking the air-gap flux density,the electromagnetic force,and the vibrational level as inputs,and taking the eccentric distance as output,the proposed neural network is trained till the error smaller than 5%.Therefore,this neural network is obtaining the input parameters of the tested motor,based on which it is automatically monitoring and reporting the eccentric error to the upper-level control center.

Analysis of Temperature Rise in High-Speed Permanent Magnet Synchronous Traction Motors by Coupling the Equivalent Thermal Circuit Method and Computational Fluid Dynamics

To solve the problem of temperature rise caused by the high power density of high-speed permanent magnet synchronous traction motors,the temperature rise of various components in the motor is analyzed by coupling the equivalent thermal circuit method and computational fluid dynamics.Also,a cooling strategy is proposed to solve the problem of temperature rise,which is expected to prolong the service life of these devices.First,the theoretical bases of the approaches used to study heat transfer and fluid mechanics are discussed,then the fluid flow for the considered motor is analyzed,and the equivalent thermal circuit method is introduced for the calculation of the temperature rise.Finally,the stator,rotor loss,motor temperature rise,and the proposed cooling method are also explored through experiments.According to the results,the stator temperature at 50,000 r/min and 60,000 r/min at no-load operation is 68℃ and 76℃,respectively.By monitoring the temperature of the air outlets inside and outside the motor at different speeds,it is also found that the motor reaches a stable temperature rise after 65 min of operation.Coupling of the thermal circuit method and computational fluid dynamics is a strategy that can provide the average temperature rise of each component and can also comprehensively calculate the temperature of each local point.We conclude that a hybrid cooling strategy based on axial air cooling of the inner air duct of the motor and water cooling of the stator can meet the design requirements for the ventilation and cooling of this type of motors.

一种自适应扩展卡尔曼滤波的永磁同步电机无位置传感器矢量控制

在粗差干扰或噪声统计偏差情况下,扩展卡尔曼滤波(EKF)对永磁同步电机(PMSM)的速度和转子位置估计存在精度下降问题,为此提出一种基于新息序列的自适应扩展卡尔曼滤波算法(AEKF)。首先,将粗差干扰加入系统观测方程中,分析粗差干扰对系统观测精度的影响。其次,为增强算法的抗扰性能,在新息协方差计算中设置加权系数,通过调整临近时刻的新息协方差阵权重,计算出新息协方差值,并更新到卡尔曼增益的计算。最后,建立AEKF数学模型,并对比粗差干扰与噪声统计出现偏差情况下,AEKF与EKF两种策略的观测性能。仿真和实验结果表明,在粗差干扰或噪声统计信息出现偏差情况下,AEKF算法对永磁同步电机转速的观测具备更强的鲁棒性及更高的预测精度。

双并列转子永磁同步电机转矩脉动产生机理及抑制

双并列转子永磁同步电机由于部分定子铁心和绕组的缺失,存在较大的转矩脉动,限制了其在并行对驱类机械装备中的应用。该文对双并列转子永磁电机转矩脉动产生机理进行分析,并提出了相应的抑制方法。对比了N-N型、N-S型两种转子结构,阐明了N-S型转子结构的优越性。在此基础上,开展了转矩脉动产生机理研究,按照影响因素不同,逐次分析了齿槽效应、端部效应、永磁齿轮效应以及绕组参数不对称对电机转矩脉动的作用机理,构建了各个转矩分量的解析表达式。通过有限元模型,验证了理论分析的正确性。针对产生转矩脉动的不同分量,提出了相应的抑制方法,其中抑制空载转矩可以通过优化电机的结构参数来实现,抑制纹波转矩可以通过优化绕组位置分布来实现。搭建样机实验平台,验证了分析模型的准确性。

采用改进遗传算法优化LS-SVM逆系统的外转子无铁心无轴承永磁同步发电机解耦控制

为了实现外转子无铁心无轴承永磁同步发电机(outer rotor coreless bearingless permanent magnet synchronous generator,ORC-BPMSG)的精确控制,提出一种基于改进遗传算法(improved genetic algorithm,IGA)优化最小二乘支持向量机(least square support vector machine,LS-SVM)逆系统的解耦控制策略。首先,基于ORC-BPMSG的结构及工作原理,推导其数学模型,并分析其可逆性。其次,建立LS-SVM回归方程,并采用IGA优化LS-SVM的性能参数,从而训练得到逆系统。然后,将逆系统与原系统串接,形成伪线性系统,实现了ORC-BPMSG的线性化和解耦。最后,将提出的控制方法与传统LS-SVM逆系统控制方法进行对比仿真和实验。仿真和实验结果表明:所提出的控制策略可以较好地实现ORC-BPMSG输出电压和悬浮力、以及悬浮力之间的解耦控制。

倾斜偏心对同步发电机转子力学特性的影响

气隙偏心是一种常见的发电机机械故障。已有研究主要关注正常和轴向气隙均匀偏心对转子受载和振动特性的影响,较少关注轴向气隙非均匀偏心,即转子倾斜偏心。作为补充,全面分析转子倾斜偏心状态下故障程度差异对同步发电机转子力学特性的影响。其中,转子力学特性包括转子不平衡磁拉力激励特性和振动特性。以一台5kVA的两极故障模拟发电机为研究对象,分别进行理论分析、有限元仿真计算和实验验证。结果表明:正常情况下转子不平衡磁拉力为零,转子振动频率以常规基频和定子传递的各偶次谐波为主。在转子发生倾斜偏心故障后,转子不平衡磁拉力/振动以二次谐波为主。随着偏心程度增加,转子不平衡磁拉力/振动的二次谐波幅值将增大。此外,转子不平衡磁拉力沿轴向非均匀分布,在气隙越小的位置不平衡磁拉力越大。

基于代理模型的双气隙混合转子低速大转矩同步电机优化设计

为解决常规低速大转矩电机普遍存在体转矩密度低、永磁体用量多等问题,提出了一种双气隙混合转子低速大转矩同步电机拓扑结构。然而,该种电机结构相对复杂、设计参数多、优化难度大,对此提出了一种基于代理模型的双气隙混合转子低速大转矩同步电机高效优化设计方法。首先,以提高输出转矩与降低转矩脉动为优化目标,对电机的参数进行敏感性分析,实现了在保证代理模型精确度的基础上精简优化变量。然后,为提高该种电机多目标优化设计的精确度和效率,同时缩短优化周期,提出了一种序贯子空间与模式搜索算法相结合的优化算法对电机进行优化处理。最后通过有限元仿真与实验方法验证了所构建代理模型的精确性、合理性和优化方法的有效性、先进性。

基于桨距角控制的永磁风电机组高电压穿越控制策略

为解决传统永磁风电机组高电压穿越控制策略存在超速脱网风险问题,提出一种基于桨距角控制的高电压穿越控制策略。高电压穿越期间,首先,按照并网要求向电网提供无功支撑;其次,考虑转子转速限制,当转子转速达到参考值时启动桨距角控制,抑制转子转速上升;最后,通过仿真试验,验证了所提控制策略的有效性。基于桨距角控制的永磁风电机组高电压穿越控制策略,既能向电网提供无功支撑,又能避免超速脱网。