应用等效谐波绕组模型理论和电压变量法分析同步电机两相突然短路

本文应用等效谐波绕组模型理论（ＥＨＷＭ）和电压变量法（ＭＶＶ）在ｄ－１坐标系中对同步电机两相对中点突然短路进行了解析分析，计入了零序电流三次谐波磁势磁通对转顺路的耦合作用，结果表明所用理论方法简单、便捷精确。通过实例计算发现，空间三次谐波合成磁势磁 转子阻尼绕组产生很强的电流，其瞬态最大值可达空间基波合成磁势磁通所产生电流的６０－８０％，稳了大值甚至明显超过之。因此，零离电流对转子的作用应予以重视     

Δ—Y混合联接低谐波绕组研究

文章推导了Δ－Ｙ混合联接三相交流绕组谐波磁势绕组系数的一般公式，并分析了每极相槽数ｑ为不同值时，Δ接绕组与Ｙ接绕组的槽数分配，匝数关系及其对谐波磁势的削弱作用。     

基于模型预测控制的开绕组永磁同步电机高性能驱动系统控制策略

为了解决传统开电机驱动系统中存在的成本和响应特性问题,本文提出一种基于开绕组结构永磁同步电机的四桥臂变换器驱动系统的新型拓扑结构,采用模型预测控制算法来提高电流环的响应速度。为了抑制系统中的零序电流,改善驱动系统的特性。本文通过测得的绕组反电势三次谐波作为共模电压的补偿量,并采用比例环节等效增加零序电流阻抗来抑制其他次电流谐波,并将共模电压分配到预测控制输出的载波中,以此将零序电流抑制策略纳入模型预测控制,在此基础上构建了综合考虑电机绕组反电势三次谐波和逆变器死区的开绕组永磁电机驱动系统的仿真模型,通过仿真验证了本文提出的系统控制策略的有效性。     

相带磁势谐波为极小值的等槽满率三相双层同心绕组

证明了三相电机相带谐波绕组系数所构成的数列为ｑ－１个数的循环数。因此，不等匝各槽槽满率互异的双层同心绕组能完全消除相带磁势谐波的匝比只有一组。用数学分析法解出相带磁势谐波为极小值等槽满率双层同心绕组的匝比。     

无轴承交替极永磁电机悬浮绕组及其特性研究

为研究悬浮绕组结构及其磁势空间谐波对无轴承交替极永磁电机悬浮特性的影响,在计及悬浮磁势空间谐波条件下,推导了电机悬浮力表达式。同时,定义径向力/电流刚度、径向力脉动率和径向自由度最大耦合率等3个参数量化分析径向力特性。在此基础上,在相同定转子结构下,研究了集中式、分布式、环形式以及带辅助线圈的集中式等4种悬浮绕组结构,并对各悬浮绕组磁势空间谐波及其影响进行分析。从降低悬浮磁势空间谐波和提高悬浮性能角度出发,提出一种带辅助线圈的集中式绕组以及悬浮磁势总谐波畸变最小的辅助线圈绕组系数优化方法。通过有限元分析,定量研究4种悬浮绕组结构下的悬浮特性,从而量化悬浮磁势空间谐波含量与悬浮特性的关系,为无轴承交替极永磁电机悬浮系统设计提供指导。     

双Y移30°PMSM两电机串联系统的谐波效应

针对广义零序谐波驱动的双Y移30°PMSM两电机串联系统解耦运行的问题,利用绕组函数的概念,建立了双Y移30°PMSM集中绕组函数的傅里叶变换函数式,得到了第一台电机高次谐波与相串联的第二台电机基波电流耦合关系的磁动势表达式,分析了高次谐波对该串联系统解耦运行的影响规律。建立了第一台电机含5、7次空间谐波的串联系统多维空间下的数学模型,进行了变速、变负载的仿真研究,得出了5、7次空间谐波的耦合效应,揭示了该串联系统解耦控制对电机定子绕组设计的基本要求。     

△—Y混合联接绕组的谐波磁势分析

通过理论分析计算，得出△－Ｙ混合联接绕组的五次、七次谐波磁势为零、从而证明这种绕组产生的合成磁势的波形趋近正弦波。     

单双层低谐波绕组感应电机振动噪声分析

分析了单双层低谐波绕组感应电机振动与噪声并探讨不同定子绕组形式对其产生的影响,对于额定功率为22kW,极数为2的小型感应电机Y180M-2中的电磁激振力情况进行了详细分析。先通过解析法分析单双层低谐波绕组的谐波磁势,研究由于线圈的分布不同带来电角度差对于谐波磁势产生的影响,包括线圈与每相绕组轴线的空间电角度差,以及线圈电流与电流轴线的时间电角度差;并探讨电磁激振力与谐波磁势的关系。最后利用2维有限元分析法仿真两台参数相同、但配置不同类型绕组的电机模型,对比验证得出在空载情况下,单双层低谐波绕组与普通双层短距绕组相比,降低了振动噪声,与解析法结果一致。     

共直流母线开绕组永磁同步电机系统零序电流抑制策略

由于变流器调制产生的共模电压和永磁电机反电动势三次谐波的存在,开绕组永磁同步电机两端共直流母线情况下会在电机绕组产生零序电流,影响了电机运行效率和稳定性。由此提出了共直流母线开绕组永磁同步电机系统零序电流抑制策略,通过建立开绕组永磁同步电机数学模型,分析了零序回路的工作特性,并通过对零序电流的闭环调节控制变流器产生共模电压以抵消反电动势三次谐波分量,达到抑制零序电流的目的;同时深入分析和对比了所提零序电流抑制策略和传统共模电压抑制策略的调制能力和最大调制度;最后,通过构建开绕组永磁同步电机实验机组,对所提零序电流抑制策略的可行性和有效性进行了实验验证。     

电枢磁场对零序谐波磁场励磁电流的影响机理分析与抑制

基于零序空间谐波磁场励磁的无刷同步电机,励磁电流的建立与电枢绕组中所注入的零序电流及转子谐波绕组的分布密切相关。同时,高次电枢谐波磁场和齿谐波磁场会对励磁电流产生干扰。为了提高励磁电流的稳定性和调节性能,该文深入分析合成电枢磁场产生的高次谐波和齿谐波电动势,研究干扰型谐波电动势对励磁电流的影响。并以2种具有不同槽极比结构的电机为例进行分析,表明在谐波绕组配合下,具有分数槽拓扑结构的电机转子谐波绕组中的高次谐波和齿谐波电动势得到明显削弱,励磁电流具有良好的调节特性。制作2种结构的样机进行实验,实验结果和2-D有限元结果一起验证了理论分析的正确性。     

零序分量注入型三电平感应电动机矢量控制系统

提出一种基于三电平中点箝位(NPC)逆变器的零序分量注入型感应电动机矢量控制方案。系统中使用快速电流控制的直接转子磁链定向矢量控制模式,由于定子电流是由快速电流环控制,因此系统中不用使用定子电压方程,并且不需要解耦电路。转子磁链位置角由磁通模型计算得到。感应电动机由三电平NPC逆变器供电,三电平NPC逆变器由于开关器件的电压应力是传统两电平逆变器开关器件上电压应力的一半,所以适合用于中压调速系统。逆变器控制采用开关优化PWM算法,通过注入零序分量,不但优化功率器件的开关频率,而且可以稳定中点电位。仿真结果表明,该方法在三电平逆变器供电的感应电动机上有效地实现了矢量控制,并且具有很好的性能。     

Selection of the flux reference for induction machine drives in thefield weakening region

In a conventional rotor flux-oriented (RFO) induction machine drive, the flux reference is usually made proportional to the inverse of the rotor speed for field-weakening operation. It is indicated in this paper, however, that such a variation cannot maintain optimal (maximum) torque capability of the machine over the entire speed range. It is further indicated that a nearly optimal torque capability can be achieved in a stator flux-oriented (SFO) system when the stator flux reference is varied as the inverse of the rotor speed     

Memory motors

A new class of permanent-magnet (PM) machines, named memory motors for their ability to change the intensity of magnetization and memorize the flux density level in rotor magnets is described in the article. A memory motor can be built either as a variable-flux or pole-changing machine. In both machine types, the magnetization of PMs can be simply varied by a short current pulse, with no need for permanent demagnetizing current as in conventional internal PM machines at flux-weakening mode. The demagnetizing current flows through stator winding(s) supplied from the same source as the stator current. Memory motors combine advantages of a wound-rotor machine (variable rotor flux) with those of a wide-speed machine (no excitation losses), resulting in a unique machine concept that has the potential to find numerous applications in electric drives.     

MRAS-based sensorless control of a vector controlled five-phase induction motor drive

Multi-phase ac motor drives are nowadays considered for various applications, due to numerous advantages that they offer when compared to their three-phase counterparts. In principle, control methods for multi-phase machines are the same as for three-phase machines. Variable speed induction motor drives without mechanical speed sensors at the motor shaft have the attractions of low cost and high reliability. To replace the sensor, information of the rotor speed is extracted from measured stator currents and voltages at motor terminals. Vector controlled drives require estimating the magnitude and spatial orientation of the fundamental magnetic flux waves in the stator or in the rotor. Open-loop estimators and closed-loop observers are used for this purpose. They differ with respect to accuracy, robustness, and sensitivity against model parameter variations. This paper analyses operation of an open-loop and model reference adaptive system (MRAS)-based sensorless control of vector controlled five-phase induction machine with current control in the stationary reference frame. The MRAS-based sensorless operation of a three-phase induction machine is well established and the same principle is extended in this paper for an IRFOC five-phase induction machine. Performance, obtainable with hysteresis current control, is illustrated for a number of operating conditions on the basis of simulation results. Full decoupling of rotor flux control and torque control is realised. Dynamics, achievable with a five-phase vector controlled induction machine, are shown to be essentially identical to those obtainable with a three-phase induction machine. Experimental verification is also provided.     

对称分量法用于异步电动机参数测试

在异步电机高性能驱动中,为了实现定子电流的励磁分量和转矩分量解耦,保证定子电流与转子磁链的准确定向,必须精确知道异步电机的电气参数.为了克服传统测量方法的缺点,基于异步电机在单相运行下的数学模型,推导出了一种电机参数测量的新方法.由于采用了对称分量法的原理,所以无须进行空载和短路实验.同其他方法比较,实验结果说明了所提出的方法有实用价值.     

Modeling of a Dual-Stator-Winding Induction Machine Including the Effect of Main Flux Linkage Magnetic Saturation

The air-gap flux linkage of a dual-stator-winding squirrel-cage induction machine comprises of four fundamental flux components due to the currents flowing in the two stator windings with $P_{1}$ and $P_{2}$ pole numbers and the currents that they induce in the squirrel cage. In view of the dissimilar pole numbers of the stator windings and frequencies of the supply voltages, the air-gap flux linkage waveform is complex, particularly when the stator and rotor teeth are saturated. This paper explores this complexity using analytic computer simulation, finite-element analysis, and some experimental results. Furthermore, a fundamental component circuit model of the machine is set forth, which, with the use of a specially defined reference frame transformation, permits an accurate simulation of the transient and dynamic characteristics. Computer simulation results are validated by some experimental results obtained from a 2-hp machine.      

Design and performance of field regulated reluctance machine

A unique topological configuration for rotating electromagnetic machines that can produce significantly higher force density than an induction machine is investigated. The stator is constructed using full pitch concentrated windings embedded in conventional slots. Rotor saliency is produced using poles constructed of axially oriented laminations. Operation is such that all of the conductors are actively taking part in torque production all of the time. The means for exciting the stator windings allows for independent control of torque and regulation of the rotor flux. A force density comparison is made based on operation with equal surface current density, conduction losses, and peak air-gap flux density. Construction and testing of a prototype 500 RPM, 28 kW laboratory machine, power converter, and controller are described     

An improved model of saturated induction machines

Conventional models of induction machines represent instantaneous saturation of the magnetizing flux either by using saturation factors or by adjusting the tangential and slope reactances. These models are often inaccurate in predicting states of the machine during transient conditions such as online starting. To remedy these inconsistencies, an improved equivalent circuit model is proposed that accounts not only for the saturation effects in the stator and rotor teeth but also, independently, for saturation in both the rotor and stator cores. The model is compared with test results as well as with more conventional models. The model demonstrates an improvement over other known models showing that detailed representations of saturation effects could be important in induction machine analysis, particularly when the machine is subjected to large signal disturbances     

电网对称故障下无刷双馈电机低压穿越分析

通过控制电机转子磁场定向得到同步坐标系下的仿射非线性状态空间模型,针对无刷双馈发电机组机侧控制器应用反馈线性化解耦控制方法。在电网电压三相对称跌落下,分析控制电机定子电流和控制电机定子反电动势的暂态响应。推导得出BDFM稳定运行时,控制电机转子磁链与功率电机定子电压满足线性比例关系,在低压穿越模式下来改善系统控制性能和稳定性,提高机组低压穿越能力。仿真结果证明了理论分析的正确性和有效性。     

FIELD SYSTEM OVERVOLTAGES IN SYNCHRONOUS GENERATOR SYNCHRONISING STUDIES

ABSTRACT

The field-current of a turbo-generator may become negative during certain forms of transient operation when d.c. exciters are used. The use of a.c. exciters operating in conjunction with a rectifier system prevents field current reversal and an overvoltage is induced into the field system owing to the momentary disruption to the m.m.f. balance between the rotor and the stator. The magnitude of this induced voltage determines the peak inverse ratings of the rectifiers and its predetermination is important in the design of the excitation equipment. The paper summarises a simulation model of a synchronous machine capable of predicting this phenomenon and considers, for illustrative purposes, two areas of generator operation that give rise to the rotor over-voltage condition. The results of these investigations are fully discussed.