On the variation with flux and frequency of the core loss coefficients in electrical machines

A model of core losses, in which the hysteresis coefficients are variable with the frequency and induction (flux density) and the eddy-current and excess loss coefficients are variable only with the induction, is proposed. A procedure for identifying the model coefficients from multifrequency Epstein tests is described, and examples are provided for three typical grades of non-grain-oriented laminated steel suitable for electric motor manufacturing. Over a wide range of frequencies between 20-400 Hz and inductions from 0.05 to 2 T, the new model yielded much lower errors for the specific core losses than conventional models. The applicability of the model for electric machine analysis is also discussed, and examples from an interior permanent-magnet and an induction motor are included.     

考虑硅钢片二维矢量磁特性的复数E&S模型

电工材料电磁特性的精细模拟是决定电工装备电磁场分析与损耗计算正确与否的关键因素之一。提出了一种能够描述硅钢片二维矢量磁特性的复数E&S模型,该模型既能够考虑交变磁化,又能够考虑旋转磁化的影响。基于硅钢片二维磁特性测量实验,提出了利用1个周期内磁能密度平均值计算模型中有效磁阻系数,利用磁滞损耗密度计算有效磁滞系数的方法。推导了结合复数E&S模型的磁场有限元分析公式,并以环形铁心模型为例,将复数E&S模型与传统E&S模型的计算结果进行了对比研究,指出复数E&S模型与有限元结合时既能够节省计算时间又能够保证材料特性模拟的准确性,是一种更适用于工程应用的矢量磁特性模型。     

计及高次谐波影响的高密度永磁同步电机铁耗计算

在经典Bertotti三项式常系数铁耗计算模型的基础上,基于谐波分析原理,引入涡流损耗、磁滞损耗和附加损耗补偿系数,提出了一种计及高次谐波影响的高密度永磁同步电机(PMSM)铁耗计算模型。该模型中的补偿系数均随磁密幅值、频率和畸变率变化,能较好地反映基波及谐波磁场对铁耗的影响。为了验证该模型的有效性及准确性,以48槽/8极内转子和36槽/48极外转子两台PMSM为研究对象,将模型的计算值、有限元仿真结果和试验数据进行对比分析。结果表明,铁耗计算模型有较高的精度,特别适用于磁密幅值与频率变化范围大的场合。     

考虑负荷频率刚性特征的一种新型低频减载实现方案

电力负荷的多样性及组合的复杂性决定了难以用微观的具体模型去描述其特征,但是事物的特征一般却可宏观定性描述.提出了一种基于负荷宏观频率刚性的新型低频减载实现方案.该策略在负荷频率调节效应检测的基础上辨识出负荷的频率刚性大小,并基于此实现低频减载的策略优化.在系统出现功率缺额、频率持续降低时,应优先切除频率调节效应系数小、频率刚性强的负荷,而保留频率调节效应系数大的负荷.如此,在频率继续下降时,通过负荷自身的频率调节效应,可减少从系统吸收的功率;而在频率恢复阶段,频率在不断上升恢复时,优先减载频率调节效应系数大、频率刚性弱的负荷,而保留频率调节效应系数小的负荷.通过此减载方案可尽可能减少负荷的损失,同时充分利用负荷的频率凋节效应实现系统频率的恢复,尽可能防止系统频率崩溃的发生.     

An example of dB/dt characteristics of the dynamic magnetic loss parameter

Ferrite cores are used for power electronics circuits operating under excitation conditions of frequency ranging from hundreds of kilohertz to several tens of megahertz. Development of a mathematical model enabling the estimation of the power loss of ferrites in high‐frequency regions, contributes to the designing of power circuits. The power loss in high‐frequency regions consists of hysteresis and dynamic magnetic losses. Although hysteresis loss does not depend on the excitation frequency, the dynamic magnetic loss increases with increasing excitation frequency. The dynamic magnetic loss parameter, λ_f, has been introduced for identifying the power loss in high‐frequency regions. In this study, λ_f − dB/dt characteristics are experimentally obtained by a newly introduced hysteresis model that uses a normal distribution function. It is found that the λ_f − dB/dt characteristics do not depend on the size of B − H loops. The instantaneous power loss of a ferrite core in the high‐frequency region can be calculated using the λ_f − dB/dt characteristics. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

电工软磁材料旋转磁滞损耗测量及建模

电力变压器和电机中存在旋转铁心损耗是其损耗预测不准的主要原因之一。针对该问题,提出电工软磁材料旋转磁滞损耗测量及建模方法。首先,矢量磁滞损耗分解为切向损耗和法向损耗两部分,分别根据圆形旋转损耗和交变损耗建模。其次,对软磁复合材料和无取向电工钢片进行模型参数辨识,并比较两种材料的损耗特性和模型参数。最后,利用三维磁特性测量装置进行多种励磁模式下的损耗测量,并对比实验结果与模型预测值。结果表明,在旋转复杂激励下,所提出的模型比传统的Steinmetz模型有更高的精度。     

钢中涡流和磁滞损耗问题

基于面向工程的基准模型,详细地研究了导磁、非导磁钢的不同的损耗行为,指出导磁钢中的磁滞损耗是其总损耗的不可忽视的部分。并根据导磁钢中的磁通密度最大值与单位磁滞损耗的关系,计算了钢中的磁滞损耗,得到了一些具有典型意义的损耗结果。     

An experimental study of the operating characteristics of an asynchronous motor with pulse supply

The fundamentals of design procedure of performance data of controlled asynchronous motors (AMs) supplied with pulse voltage are stated in this article. The proposed model is based on a L-shaped equivalent circuit for each of harmonics, on which the curve of applied to a phase voltage is displayed. It is proposed to find the increase of magnetic iron loss caused by hysteresis in proportion to the peak value of the pulse voltage. The influence of PWM voltage on magnetic hysteresis loss is determined by using a coefficient depending on the effective values of fundamental and higher harmonics of the EMF and voltages, as well as the coefficient taking into account the increase of electrical resistance of iron due to the skin effect. In a similar way, it is proposed to take into account magnetic losses in the rotor that are occasioned only by the influence of higher harmonics. It is proposed to determine the increase of resistance and decrease of the inductance of short-circuited rotor of the influence of currents of higher harmonics by the well-known Interelectro methodology. The resulting values of consumption current, power factor, effective power, and consumption power of an asynchronous motor with pulse voltage are calculated taking into account the total effect of currents and voltages of fundamental and higher harmonics. Based on the methodology that we have laid out, a program was written and modeling was carried out of the operational characteristics of an asynchronous motor with a power of 180 W supplied by a PWM inverter with a fundamental frequency of 50 Hz. In addition, the harmonic composition of pulse voltage was obtained by processing the oscillograms taken from phase windings of the motor supplied by the frequency converter. To experimentally check of the proposed model, an experimental plant for loading the asynchronous motor was assembled and the operational characteristics of asynchronous motor with the fundamental harmonic of 50 Hz were determined. The experimental results showed satisfactory convergence with the calculated results that makes it possible to recommend the proposed methodology to evaluate the energy indices of frequencycontrolled asynchronous motors.     

基于二维磁特性测量的电工钢片矢量磁滞模型

提出一种模拟电工钢片复杂磁特性的矢量磁滞模型。该模型考虑频率、磁化历史等因素对磁滞特性的影响,模型中磁滞系数与磁阻系数的确定是基于双激励二维磁特性测量实验获得的,在实验中通过对磁通密度变化轨迹的控制实现对磁场强度波形的测量。所提出的模型既避免了传统磁滞模型数学表达的复杂性,又提高了模拟的准确度,更适用于工程应用。通过与传统模型及实验测量结果的比较,证明了所提出的模型能更有效、更准确地模拟电工钢片的复杂磁特性。     

500 kV电力变压器直流偏磁耐受性能的仿真研究

为了深入研究500 kV电力变压器的直流偏磁耐受性能,根据J-A磁滞回线理论,基于电路磁路模型建立了500 kV自耦变压器的直流偏磁仿真模型,通过改变J-A模型中的关键参数,仿真研究了矫顽力、剩磁和磁滞损耗等硅钢片磁化特性对500 kV变压器直流偏磁耐受性能的影响。仿真结果表明,变压器直流偏磁时,励磁电流出现畸变,有偶次谐波出现,励磁电流随直流分量的增大呈现不同的增幅。当磁滞回线的矫顽力增大时,励磁电流及其总谐波畸变率随外加直流分量的增幅变小。当剩磁和磁滞损耗增大时,励磁电流及其总谐波畸变率随外加直流分量的增幅加剧。研究结果可为大型变压器直流偏磁耐受能力评估及直流偏磁抑制措施提供理论依据和新思路,具有一定的实用价值。     

东北电网频率与联络线潮流的关系

介绍了东北电网的频率与联络线潮流控制方式,结合东北电网2002年几起大机组跳闸后频率及区域联络线潮流实时记录数据,分析了各区域联络线潮流的变化情况,计算了辽宁、黑龙江电网的自然频率特性系数,结果表明电网运行中自然频率特性系数随运行方式变化而不断变化.还分析了频率波动及区域电网频率特性系数对东北电网内各区域间联络线潮流的影响,证明了区域频率特性系数的设定应稍大于自然频率特性系数以利于调整频率及联络线功率偏差.     

基于谐振逆变电路的纳米晶材料高频测量系统研究

针对纳米晶材料高频磁滞回线和损耗测量受到仪器带宽和额定功率限制的问题,设计了一种新型高频测量系统。该系统采用直流电源搭配推挽谐振逆变电路代替传统的函数信号发生器加功率放大器,通过调节电路元件以调整谐振频率从而实现1 kHz-10 kHz频段的频率调节,具有传输功率高、效率高、谐振频率连续可调等特点。利用PSCAD仿真软件研究了逆变电路的各项功能。研制了测量系统并实测了10 kHz时纳米晶磁环的磁滞回线和损耗曲线。通过将该测量系统与传统的测量平台进行小容量的模型实测对比,测量系统误差为3.3%,证明了所研制的测量系统具有较高精确度。     

Research on Iron Loss of Switched Reluctance Starter/Generator for Energy Storage

In order to better realize the energy recovery and storage of hybrid EVs (HEVs), a switched reluctance starter/generator (SRS/G) with both starting and power generation functions is investigated in this paper. First, the iron loss of SRS/G is mainly studied to reduce the motor loss and improve the power generation efficiency. Then, the energy storage of hybrid EVs can be effectively improved. Secondly, a magnetic flux density (MFD) wave-forms solution method is proposed to solve the difficulty in calculating the iron loss of the SRS/G. Compared with the commonly used finite element method, the proposed solution method has the advantages of simple, fast and small computational amount. Meanwhile, considering the different operating conditions of SRS/G, the iron loss models for both the time-domain and frequency-domain are established. In addition, the calculation formula of the variable coefficient Bertotti three-term loss separation is improved. As the hysteresis loss coefficient, the Steinmetz coefficient and the stray loss coefficient are respectively fitted by the Fourier fitting method. This method is also applied to solve the iron loss of SRS/G. Finally, through an experimental verification, it is indicated that the development of proposed method has high accuracy.     

改进的有源电力滤波器滞环电流控制策略

针对滞环电流控制开关频率不固定、频率范围大从而产生较大损耗的问题,以提高控制精度、减少开关损耗为目标,提出一种有源电力滤波器随机变环宽滞环电流跟踪控制方法。该方法针对电力系统负荷的特点,产生预置变环宽函数,能够较合理地给出滞环宽度,并引入随机函数,将开关频率范围拉宽,使电流频谱分布范围更宽,从而降低谐波畸变率,减少开关损耗。仿真及实验结果均证明了其可行性,可在保持总控制精度的同时有效降低总开关损耗,同时具有良好的补偿性能。     

直流偏磁状态下电力变压器铁心动态磁滞损耗模型及验证

直流偏磁状态下,电力变压器的附加损耗显著增加,试验测量得到的变压器空载损耗不能充分表征铁心实际损耗。为正确评估变压器铁心可能出现的过热问题,有必要建立其准确的数学模型。该文在Jiles-Atherton基本磁滞模型的基础上,从能量平衡原理出发,考虑铁心在交流状态下的涡流损耗和异常损耗,建立了合理可逆磁化系数条件下,以磁通密度作为输入量的铁心动态磁滞损耗模型。利用遗传算法提取试验变压器铁心在正常工作条件下的动态模型参数,并用于对不同幅值直流偏磁电流作用下的铁心损耗进行仿真计算。将计算结果与试验结果进行对比,发现二者吻合较好,说明该动态模型能较好的描述直流偏磁状态下电力变压器铁心动态磁滞损耗,验证了模型的正确性和实用性。     

基于相量测量单元录波数据的南方电网频率特性分析

准确地掌握电网的频率特性,是采取相关措施确保电网安全稳定和经济运行的基础。利用相量测量单元(PMU)录波数据,通过BPA仿真,分析了南方电网2010年1月份的13次机组跳闸故障。结果显示,南方电网采用以下模型可以基本上反映系统的频率特性:对实测过模型参数的机组,其调速系统采用实测模型;未实测的其余机组的调速系统采用经典模型,但死区设置为±0.05 Hz,调差系数设置为约0.164;负荷的有功功率频率因子取4.0。但2010年1月份的各次跳机事件的功率损失和频率变化量相对较小,由此得出的仿真模型对于大扰动是否适应还有待验证。     

MnZn功率铁氧体高频功耗特性分析

采用氧化物陶瓷工艺制备了2～4MHz频段高频开关电源用MnZn功率铁氧体,通过对铁氧体断面显微结构、密度和磁特性的测试,研究了Fe2O3含量对MnZn功率铁氧体功率损耗特性的影响。结果表明,随着Fe2O3含量的增加,晶粒尺寸逐渐减小,常温下3MHz、10mT高频损耗(Pcv)先增大后减小,Fe2O3含量从58mol%增加到59 mol%时,损耗下降非常明显,而在100℃时,铁氧体的剩余损耗逐渐降低,导致总损耗随着Fe2O3含量的增加而减小。随着频率的升高,剩余损耗(Pr)占总损耗的比重逐渐增加,成为损耗的主要部分,而磁滞损耗(Ph)占总损耗的比重逐渐降低,涡流损耗(Pe)所占比重变化不明显。     

三相有源电力滤波器不定频滞环电流控制研究

为改善传统滞环电流控制方法中开关损耗及开关频率过大的问题,对三相并联型有源电力滤波器的电容中点式主电路及工作原理进行分析,提出一种基于电压空间矢量脉宽调制的不定频滞环电流控制方法,该方法能够有效降低平均开关频率,减小误差电流.利用Simulink进行了系统仿真分析和实验,并对不定频滞环电流控制算法及滞环电流比较算法进行...     

机械应力作用下电工钢片静态磁滞特性模拟方法研究

准确快速模拟磁性材料在不同应力下的磁滞特性对设计承受机械应力的电气设备铁心有重要意义。用BROCKHAUS-MPG200电工钢测试系统,测量了电工钢片样本在不同应力下的磁滞回线,发现其在应力作用下,磁滞回线会产生局部畸变的现象,且磁密越高,这种畸变越严重。为此,首次将2种常用的简化Preisach模型拓展至应力下的电工钢片磁滞特性模拟,发现仅有一种Priesach模型适用。根据该模型的基本特征,仅需利用具有畸变特性的实测极限磁滞回线,即可辨识不同应力值下的Everett函数。提出立方插值法提取以应力为变量的逆Everett函数,建立了应力下电工钢片的静态逆Preisach模型。实验及仿真结果表明,该模型计算精度较高,可用于实际工程中应力下磁性材料的磁滞特性模拟及磁滞损耗计算。     

机械应力作用下电工钢片静态磁滞特性模拟方法研究

准确快速模拟磁性材料在不同应力下的磁滞特性对设计承受机械应力的电气设备铁心有重要意义。用BROCKHAUS-MPG200电工钢测试系统,测量了电工钢片样本在不同应力下的磁滞回线,发现其在应力作用下,磁滞回线会产生局部畸变的现象,且磁密越高,这种畸变越严重。为此,首次将2种常用的简化Preisach模型拓展至应力下的电工钢片磁滞特性模拟,发现仅有一种Priesach模型适用。根据该模型的基本特征,仅需利用具有畸变特性的实测极限磁滞回线,即可辨识不同应力值下的Everett函数。提出立方插值法提取以应力为变量的逆Everett函数,建立了应力下电工钢片的静态逆Preisach模型。实验及仿真结果表明,该模型计算精度较高,可用于实际工程中应力下磁性材料的磁滞特性模拟及磁滞损耗计算。