An Improved Stator Flux Observation Method of Permanent Magnet Synchronous Motor

The stator flux and electromagnetic torque observation is the basis of direct torque controlled permanent magnet synchronous motor( PMSM) drive system. However,the traditional stator flux observer based on voltage model is affected by integral initial values and integral drift,that based on current model is affected by the parameters of PMSM,so a new stator flux observation method is proposed based on an improved secondorder generalized integrator( SOGI). Compared to the stator flux observation method based on the conventional SOGI,the proposed method can not only overcome the influence of integral initial values and integral drift,but also completely eliminate the DC offset's influence. Therefore,the observation accuracy of stator flux is further improved. The simulation and experimental results both show that the proposed method has a higher stator flux and electromagnetic torque observation precision.

Study of Steady-state Performances for a Novel Line-start Single-phase Permanent Magnet Synchronous Motor With Three Parallel-connected Windings

对于三相感应电动机的单相运行,学者们已经提出了多种实用的接线方式,比如Smith接法、SEMIHEX接法。然而,对于三相异步起动永磁同步电动机的单相运行,很少有合适的接法提出。将并联式接法应用于三相异步起动永磁同步电动机的单相运行,提出了一种新型三绕组并联式异步起动单相永磁同步电动机。分析了三相异步起动永磁同步电动机同步运行时以及起动瞬间的正序、负序阻抗,基于对称分量法,对该接法电机的对称运行条件进行分析,得出了电容的确定方法,并利用遗传算法对电容值进行优化。提出了该新型电机稳态性能的计算方法;设计了一台高功率因数和一台低功率因数三相异步起动永磁同步电动机作为样机,并分别将其改接为三绕组高效单相永磁同步电动机,进行实验研究。实验结果表明,低功率因数的异步起动永磁同步电动机更适合改接成新型三绕组并联式单相永磁同步电动机。由低功率因数三相永磁同步电动机改接成的单相异步起动永磁同步电动机在额定负载下运行时,具有与同容量三相永磁同步电动机相近的效率和更高的功率因数。

Zero-Sequence Current Suppression Strategy for Open-End Winding Permanent Magnet Synchronous Motor Based on Model Predictive Control

Compared with the traditional three-phase star connection winding,the open-end winding permanent magnet synchronous motor(OW-PMSM)system with a common direct current(DC)bus has a zero-sequence circuit,which makes the common-mode voltage and the back electromotive force(EMF)harmonic generated by the inverters produce the zero-sequence current in the zero-sequence circuit,and the zero-sequence current has great influence on the operation efficiency and stability of the motor control system.A zero-sequence current suppression strategy is presented based on model predictive current control for OW-PMSM.Through the mathematical model of OW-PMSM to establish the predictive model and the zero-sequence circuit model,the common-mode voltage under different voltage vector combinations is fully considered during vector selection and action time calculation.Then zero-sequence loop constraints are established,so as to suppress the zero-sequence current.In the end,the control strategy proposed in this paper is verified by simulation experiments.

Torque analysis for double-stator permanent-magnet motor

In addition to the characteristics of a conventional motor, a novel direct-drive double-stator permanent-magnet brushless motor proposed can operate in the state of either a generator or a motor as appropriate. Through numerical calculation and analysis, the output torque of double-stator permanent-magnet brushless motor of the same volume as the traditional machine is discussed, and the reduction of torque ripple by using the structure features of this motor is investigated. The results indicate that lower torque ripple under the condition of ideal effective torque can be obtained by the rational design of motor. The prototype motors tested show that this kind of motor structure has a higher power density.

A New-style Permanent-magnet Motor with Double-stator Structure

A new-style direct drive motor with double-stator structure is proposed. The structure and principle of the permanent-magnet (PM) brushless motor are discussed. On the basis of numerical calculation, the cogging torque waveforms of the prototype motor when staggering two stators are analyzed. The method that can reduce torque ripple making use of the structure features of this motor is investigated. The results of numerical calculation and experiment indicate that designing motor with this kind of structure is a good scheme for increasing the power density.

Visualization and Quantitative Evaluation of Eddy Current Loss in Bar-Wound Type Permanent Magnet Synchronous Motor for Mild-Hybrid Vehicles

This paper describes the conductor eddy current loss that occurs in a permanent magnet type synchronous motor with a distributed winding stator using a rectangular copper wire designed for mild hybrid system applications for small vehicles.Compared with the conventional round wire inserter method,the space factor can be improved and the coil-end length can be shortened by applying a so-called hairpin windings using a pre-formed into hairpin shape of bar conductor,and as a result,DC current resistance of the armature winding can be reduced.However,since the conductor cross-sectional area tends to increases,the conductor eddy current loss generated by the space harmonics linkage becomes too large to ignore.In order to study the reduction of the conductor eddy current loss,it is important to visualize the spatial leakage flux distribution which causes loss and finely analyze how the magnetic path is formed.Therefore,analysis of the conductor eddy current loss distribution generated in the bar-wound conductor is performed using the CAE model that faithfully reproduces the coil-end shape of the actual machine.Furthermore,it was qualitatively clarified what ratio of conductor eddy current loss at various driving points.Finally,the results of preliminary study on reduction of conductor eddy current loss are reported.

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.

基于滑模变结构的风电机组一次调频算法研究

针对并网风电场中,经典一次调频控制方法存在抗干扰能力弱、机组易脱网的问题,提出一种基于滑模变结构的风电机组一次调频控制算法。首先,在永磁同步风电机组工作原理的基础上,建立含有大电网的风电机组模型。其次,为了解决传统比例积分微分(proportional integral differential,PID)控制下抗干扰能力弱的问题、引入经典滑模变结构控制器。然后,针对经典滑模变结构控制器导致执行机构存在抖振较多的缺点,提出一种基于sigmoid函数趋近率的滑模变结构一次调频控制算法。最后,通过MATLAB/Simulink对风电机组一次调频进行建模仿真,并与经典控制算法相比,验证了所提算法的可行性,在风速波动和电网故障的环境下,滑模变结构一次调频控制算法更具有效性。

基于径向气隙磁密和定子电流的永磁同步电机均匀退磁故障诊断研究

该文提出一种基于径向气隙磁密和定子电流的永磁同步电机均匀退磁故障诊断方法。首先,建立电机的d轴等效磁路模型,分析均匀退磁故障后径向气隙磁密的变化规律;然后,获取电机的径向气隙磁密和定子电流信号,对各极下径向气隙磁密幅值进行归一化处理,并绘制雷达图,根据雷达图和比较相同定子电流幅值下健康电机和故障电机的各极下径向气隙磁密幅值的平均值,来诊断均匀退磁故障;利用空载各极下径向气隙磁密幅值的平均值计算故障程度。最后,仿真和实验结果均验证所提均匀退磁故障诊断方法的有效性。

齿调制作用下转子开槽对永磁电机电磁振动影响

为了研究齿调制作用下转子表面开槽对永磁同步电机电磁振动的影响,以小功率分数槽集中绕组(FSCW)内置永磁同步电机(IPMSM)为研究对象,通过麦克斯韦应力张量法推导径向电磁力波的频率及空间阶数特征。分析齿调制作用在FSCW-IPMSM中将空间高阶电磁力波调制为低阶电磁力波的过程,并给出转子表面开槽在齿调制作用影响下与电磁振动间的联系。研究表明,转子表面开槽结构的改变会使各次谐波磁场发生变化,进而改变以极数阶电磁力波为代表的高阶电磁力波的幅值。在齿调制作用下,这些高阶电磁力波会被调制为幅值较高的低阶电磁力波,并引起不同幅度的低阶振动。然后建立C型、V型两种不同转子表面开槽结构的10极12槽FSCW-IPMSM电磁及结构有限元分析模型并进行仿真分析。结果表明,极数阶即10阶电磁力波会被调制为2阶并引起2阶振动,且两种不同开槽结构间的电磁振动存在着高达22.1%的差异。最后,在一台10极12槽样机上进行振动实验,验证理论与仿真分析结果。

复杂工况下的永磁同步电机典型绕组故障在线诊断

绕组故障作为永磁同步电机常见的故障之一,严重影响电机正常运行。但由于电机运行工况复杂,故障特征波动严重,基于故障特征的诊断精度较低。为提高复杂工况下绕组故障的诊断精度,该文提出一种复杂工况下基于控制器信号的在线诊断方法。首先,对典型绕组故障进行故障机理分析,并通过基于自适应随机窗的快速傅里叶变换(FFT),提取控制器信号的相应故障特征;其次,通过研究单一工况和复杂工况下的各故障特征分布,揭示部分故障特征会在低转速工况下失效;再次,定义了复杂工况下故障特征性能指标,用于筛选故障特征;最后,在人工神经网络的基础上,提出了深度优化人工神经网络,引入批量归一化(BN)算法,并对深度网络结构残差化,提高网络泛化能力和诊断准确性。实验结果表明,通过计算故障特征性能指标,能够在诊断前对故障特征进行有效筛选,且深度优化人工神经网络的诊断准确性高、泛化能力强,在复杂工况下能够实现电机典型绕组故障的精确在线诊断。

集中绕组模块组合式定子结构对低速大功率永磁电机性能影响

针对集中绕组模块组合式定子结构对低速大功率直驱永磁同步电机性能的影响进行研究。首先介绍了模块化定子的分块规则和分块数。基于绕组函数法推导了单个定子单元模块在不同拆分方式下的绕组函数和电感表达式。基于有限元仿真先分析了仅绕组分块对电机性能影响;然后分析了冲片和绕组都分块对电机性能影响。通过对比空载和负载性能,总结出各种定子模块化拆分方案的优缺点,为大功率低速直驱永磁同步电机的模块化设计与制造建立了基础。

具备内部故障仿真能力的永磁同步发电机电磁暂态建模与仿真方法

对永磁同步发电机(PMSG)内部定子绕组故障的精确建模与仿真有助于设计有效的状态检测系统和控制保护策略。首先对PMSG内部故障特征进行分析和详细的数学推导,给出了适合电磁暂态(EMT)建模的状态空间形式的动态方程。进而提出了一种PMSG内部故障EMT建模与仿真方法,并推导出其等效电路。利用MATLAB对推导出的方程进行了数值计算迭代求解,并在PSCAD/EMTDC中搭建了PMSG测试模型,与数值计算结果进行分析和对比验证。分析结果表明,PMSG内部故障会在短路路径中产生较大的循环故障电流,但是从发电机外部特性很难判断是否发生内部故障。对比验证结果表明,所建立PMSG内部故障EMT模型可准确反映内部故障特征,验证了所提建模方法的正确性。

定子槽偏移的内置式永磁同步电机的优化与分析

为降低永磁同步电机齿槽转矩和提高电机输出性能,以三相8极36槽内置组合式永磁同步电机为例,提出了一种电机定子槽偏移的方法。首先,通过理论推导定子齿气隙磁导函数,建立电机定子槽偏移数学模型;其次,对不同定子偏移槽数下不同偏移角度的齿槽转矩峰值、输出转矩以及转矩脉动的影响做出分析,利用自适应遗传算法确定电机定子偏移槽数偏移角度下的目标值;最后,通过试制样机进行实验。结果表明,优化后的电机齿槽转矩峰值降低了49.56%,转矩脉动降低了39.2%,平均输出转矩得到适当提升,气隙磁密谐波得到适当降低,同时,平均输出转矩增大,电机输出性能得到提升。所提定子槽偏移结构及多目标联合仿真方法具有一定的合理性和有效性,可为同类型电机的齿槽转矩优化和输出性能提高提供参考。

转子温度空间分布差异诱发永磁电机局部失磁特性研究

永磁材料磁特性受工作温度影响较大,高工作温度下存在的不可逆失磁现象是永磁电机高可靠性设计的主要瓶颈。针对内置式磁路结构的高功率密度永磁电机用钕铁硼永磁材料的不可逆失磁问题,基于电机全域空间损耗、温度分布的差异,该文提出一种永磁体局部失磁分析模型与特性计算方法。通过磁体虚拟分块法建立基于温度、退磁率等变量的永磁材料磁特性分析模型,利用电磁场和温度场双向耦合的三维多物理场计算方法,得到电机转子永磁体损耗、温度和局部失磁的空间分布特性。最后,通过对一台115 kW、8极永磁电机样机转子永磁体温度和转子表面磁场的实验测试,验证了分析模型与计算方法的准确性,为永磁电机局部失磁问题研究及精细化防失磁设计提供依据。

应用于交流电机驱动的新型串联绕组拓扑的动态电流控制性能分析

电机绕组的动态电压是影响其电流变化能力的直接因素。为了提升电机的转矩响应速度,从直流电压利用率的角度分析串联绕组拓扑的动态电流控制能力。首先,从拓扑结构出发,相比于三相半桥拓扑,串联绕组拓扑将直流电压利用率提升了73%,这使得其动态电压更加充裕。然后,在不同的转速工况下,分析串联绕组拓扑、三相半桥拓扑以及采用电压修正策略的三相半桥拓扑的动态电流控制性能。最后,经仿真与实验证明,若采用电压修正策略来增大三相半桥拓扑的动态电压裕度,其只在转速接近额定转速时效果才凸显,且提升有限。而采用串联绕组拓扑,其在电压深度饱和下的电流动态响应时间将显著减小。

基于开绕组电机的电动汽车双电池集成充电系统准直接功率控制

针对基于开绕组永磁同步电机和双电池组驱动的电动汽车提出一种集成化充电拓扑,充电运行时将双逆变器和电机绕组复用为双PWM整流器及其输入侧滤波电感。在三相电压源型整流器(VSR)和开绕组永磁电机数学模型的基础上,将电网坐标系和电机坐标系相统一,分析了充电状态下的电磁转矩。实际运行时存在双电池剩余电量不相等的情况,导致充电时双通道功率不平衡,因此设计了一种准直接功率控制策略,以解决功率不平衡带来的转矩脉动问题。最后通过仿真和实验验证了该集成化充电拓扑的可行性。

小尺寸潜油永磁电泵机组的分析与优化

为了满足小尺寸投捞电泵在海上的实施,设计了一种小尺寸的潜油永磁电泵机组。针对定子槽参数变化对电机性能影响较多这一问题,提出了多目标粒子群优化算法对性能指标进行优化。对粒子群进行归一化处理,通过有限元分析得到目标值,再通过Pareto得到多目标排序,由粒子群算法更新粒子的速度和位置,得到适合小尺寸永磁同步电机的定子槽结构。将电泵机组连接后,下入实验井中进行了电泵机组测试,试验结果表明,该电泵机组可以满足外径183 mm、内径150 mm隔热油管的下入性。

基于定子辅助槽永磁电机电磁激振力削弱研究

电磁振动噪声是电机噪声的主要来源,直接影响电机的NVH性能,而径向电磁力是产生电磁振动噪声的主要原因。针对9槽6极电机低阶径向电磁力产生振动噪声大的问题,首先基于Maxwell应力方程推导分析径向电磁力的表达式,指出定子电枢槽开口改变了空载径向电磁力最低非零阶数的现象;提出在定子齿顶开辅助槽的方法,对比研究了不同开槽数和开槽尺寸对气隙磁导的影响;通过定子齿开辅助槽改变气隙磁导分量,研究了不同开槽方式对低阶径向电磁力和齿槽转矩的影响,基于此确定合理的开槽方案并通过多目标算法获取电机最佳开槽参数。结果表明,对于分数槽永磁电机,定子齿开辅助槽能够有效降低电机空载低阶电磁激振力。

高功率密度永磁同步电机多物理场设计与优化

针对额定功率50 kW、额定转速2050 r/min的高效率高功率密度永磁同步电机进行多物理场优化设计,包括电磁场、温度场和应力场的设计与仿真分析。为进一步提高功率密度,选用发卡绕组替代传统的圆线绕组;为改善反电动势的正弦度,相较于传统的径向充磁,选用了多段式Halbach阵列充磁方式。本文给出了高功率密度电机的设计流程和电磁参数优化过程,通过多物理场仿真表明,本文所设计电机能够同时满足电磁指标和各项温升和应力指标。