A MATHEMATICAL MODEL OF THREE-PHASE INDUCTION MACHINES

ABSTRACT

A technique for studying the behaviour of three-phase, wound-rotor induction machines under both transient and steady-state conditions is described. It is arranged to cope with both non-sinusoidal winding distributions and non-linear operation of the magnetic paths. Because such conditions prevent simple expressions from being obtained when transformations are made to produce a two-axis equivalent model, the present analysis is based on the actual machine windings. The basic equation. |v| = |z| |i| is solved for each time step after the appropriate values of the elements in the impedance matrix have been determined by examining the magnetic conditions around the air gap periphery.

The results of particular studies are given.     

SIMPLIFIED FREQUENCY-DEPENDENT MODEL FOR INDUCTION MACHINES

ABSTRACT

The purpose of the present paper is the representation of the behaviour of induction motors, in the presence of harmonics in the power supply, by using a simplified frequency-dependent model. The model is the end product of statistical processing, which leads to the definition of “typical“ parameter values as a function of the frequency. This model is intended primarily for the study of harmonic power flow by means of computer programs. It has also been validated on a test network on which experimental results are available

Better rotating load models at harmonic frequencies can improve the studies of power quality in the design of the future electric power systems.     

采用等效负荷简化配电网

提出了一种通过馈线两端电压和流过馈线两端开关的功率反映馈线上的负荷及其分布情况的配电网简化分析方法。这种方法只需对变电站的出线开关、馈线的分段开关和联络开关进行量测，而不必量测馈线上的配电变压器，就能得到满意的分析结果，并论述了简化分析的基本原理，讨论了带有支线的馈线处理方法，采用支路电流法验证了该方法的可行性，并给出了应用实例。     

反映综合负荷动特性机理的感应电动机模型

针对感应电动机（IM）动态负荷模型（IM_DLM）不足以描述综合负荷特性，因而不实用的问题，采用解 耦辨识的方法分析了综合负荷有功功率特性和无功功率特性所对应的IM_DLM的不同；提出了在IM_DLM中引入一个无功功率“静态补偿”（LSVC）项的新模型 （LSVC_IM_DLM），并对引入的LSVC项的物理机理进行了定性分析。通过比较河北于庄和广东郭塘2个变电站的不同类型负荷特性对IM_DLM和LSVC_IM_DLM的辨 识结果，表明LSVC_IM_DLM较符合综合负荷的物理机理，其模型参数分散性小，LSVC项系数能反映不同负荷类型的变化，是一种具有重要实用价值的机理 型动态负荷模型。     

MULTI-LAYER ANALYSIS OF COMPOSITE-ROTOR INDUCTION MACHINES

ABSTRACT

The multi-layer, transfer-matrix method is used for the analysis of composite-rotor induction machines, including rotors with unlaminated steel sections. A method is given for including the variable permeability of each steel layer and an iterative computation technique is used to obtain the solution under specified operating conditions. Examples of a solid-steel rotor and a composite rotor, with steel and cage sections, are presented. The latter example is considered with special reference to its application in a fan drive.     

MAGNETIC EQUIVALENT CIRCUIT PRESENTATION OF ELECTRIC MACHINES

Abstract

The fundamentals of the magnetic equivalent circuit concept are described. This principle is illustrated by several examples. The position of the method in modem theory and design of electric machines is defined and discussed.     

感应电动机电容自励制动的计算机仿真

利用三相感应发动机的稳态等效电路,导出了感应电动机电容自励制动的数学模型,实例仿真结果与实测结果相吻合。利用仿真结果讨论了励磁电容,负载电阻／及转动惯量对制动过程的影响。     

感应电动机负荷模型参数解析灵敏度分析及参数辨识策略研究

通过对感应电动机参数的解析灵敏度分析,较好地解释了感应电动机负荷模型中部分参数易辨识,部分参数难以辨识且辨识结果较离散这一现象.研究结果表明:灵敏度大的参数易辨识,灵敏度小的参数难辨识,且辨识结果较离散;在不同的激励强度下,感应电动机负荷模型各参数灵敏度将随激励的增强而增大.文中提出了一种新的感应电动机负荷模型参数辨识策略.经现场实测数据建模,验证了该辨识策略的有效性及可行性.     

短期负荷预测的支持向量机方法研究

提出了一种基于支持向量机(SVM)理论的电力系统短期负荷预测方法。该方法采用结构风险最小化原则(SRM)，与采用经验风险最小化原则（ERM)的传统神经网络方法相比，具有更好的泛化性能和精度，减少了对经验的依赖。SVM算法以统计学习理论作为其理论基础，它的训练等价于解决一个二次规划问题。为了提高负荷预测精度，文中在训练数据集中采用了负荷数据和温度数据。通过和多层BP神经网络进行比较的试验，结果证明了其在短期负荷预测中的有效性。     

FIELD-ORIENTED CONTROL OF INDUCTION MACHINES IN THE PRESENCE OF MAGNETIC SATURATION

ABSTRACT

This paper presents derivation of the equations which describe field-oriented control of saturated induction machines. Field-oriented control principles are applied on the saturated model of induction machine and new equations are obtained, which differ significantly from the well-known model valid when the main flux saturation is absent or neglected. Rotor flux oriented control of voltage-fed and current-fed saturated induction machines is discussed. New decoupling circuits which are needed under saturated conditions are presented. Simulation results, which show the influence of main flux saturation on transient behaviour of the drive and which verify the theoretical results are included.     

EFFECT OF SKEWING ON THE COGGING TORQUE IN INDUCTION MACHINES

ABSTRACT

This paper presents a simplified method to predict the cogging torque in induction machines including the skewing effect An equivalent circuit including die effect of both slot harmonics and rotor skewing is developed. A special attention is paid to study the skewing effect on the machine behaviour especially at starting instant. Moreover, the leakage reactance due to the skewing is calculated using the suggested method. Useful conclusions are given at the end of this paper which is thought of good use and valuable for both designers and users of squirrel cage induction motors.     

一种新型的感应电动机直接转矩控制

提出了一种新型的感应电动机直接转矩控制方法,采用空间矢量调制方式生成逆变器开关控制信号,从而有效减小转矩、磁链和电流的脉动。与其他基于空间电压矢量调制的直接转矩控制方法不同,定子磁链幅值与转矩控制器的设计基于变结构控制理论,具有实现简单、鲁棒性强的特点。理论分析证明了定子磁链幅值与转矩控制的渐近稳定性。仿真和实验结果表明了所提方法具有良好的动静态性能。     

CIRCUIT MODELS FOR POLYPHASE INDUCTION MACHINES

ABSTRACT

For many years, induction machines operating in the balanced steady state have been represented for analysis by the conventional “T” form of equivalent circuit. Simplification of this circuit to expedite analysis has normally involved approximation This paper presents a number oE simplified equivalent circuits which preserve the accuracy of the “T” circuit and to some extent improve on it by more appropriate representation of saturation and core loss. Experimental confirmation of this improvement is included. The new circuits are denoted as “T” and “inverse-T” because of their inductance configuration.     

双定子感应电动机等效电路分析

首先引入旋转等效的概念,将双定子感应电机两个定子之间的相对旋转,看成定子不动,而转子对应部分扭转了一个角度α,又通过引入“相拉折算”的概念,将两个定子之间旋转角的变化,等效为转子相绕组有效匝数的变化,于是能够进行绕组折算,得到折算后的基本方程式,进而导出与常规感应电机相似的“Ｔ”形和“Г”形等效电路。     

CORRESPONDENCE: SIMPLIFIED ESTIMATION OF END EFFECTS IN LINEAR INDUCTION MACHINES

A pattern recognition application, using artificial neural networks (ANN), may be categorized as the largest category that covers the use of a neural networks for classifications. It is proved that ANNs are excellent for the applications of complex pattern recognition such as visual images of objects, speech recognition, printed or handwritten characters, and many other types of pattern recognition. Such wide applications are developed, based on the major advantage of the neural networks of being inherently error tolerant, i.e., it can solve problems adequately with information (data) that is uncertain, incomplete, or noisy. The reliable results of the power system security and economical analysis depend on the supply of real-time data base, results of power system state estimation, programs whose major problem is the determination of the network topology configuration. The determination of the topology suffers from the uncertainty of the collected data related to the circuit breakers status, due to the possible communication errors and/or failures. This problem solution matches the potential of the neural networks that can generalize, and after training, they can handle imperfect or incomplete data, providing a degree of fault tolerance. This paper describes an efficient ANN power system topology classifier. The function of such a classifier is to determine the system topology configuration under the presence of incorrect and/or incomplete data concerning the lines and the breakers status. A double layered ANN model is developed and explained as well as the specially efficient training algorithm. Comparative training and test results are reported, and they prove the robustness of this ANN.     

SMALL SIGNAL DYNAMIC ANALYSIS OF REGENERATION AND SELF-EXCITATION IN INDUCTION MACHINES

ABSTRACT

Small signal stability and dynamic response is examined and compared for six modes of source-connected and self-excited induction generator operation including both voltage (VSI) and current (CSI) inverter systems. It is shown that conventional small signal machine modelling is incapable of yielding any information whatsoever concerning the stability of self-excitation at constant speed. A recently introduced small signal model which includes main flux saturation overcomes these difficulties and is employed to study the stability properties of all six modes. General stability and dynamic response properties of each mode are summarized and compared, especially with respect to the influence of saturation. The capacitive self-excited case is shown to require special treatment because of the phase freedom inherent in this mode. Experimental confirmation of some of the results is included.     

高温超导永磁体等效电流模型

本文通过比较分析了高温氧化物超导体与稀土永磁体的各向异性,实验表明设计磁体时ａｂ轴方向俘获磁场与ｃ轴方向相比可忽略,提出与描述ＨＴＳ块材俘获磁场的宏观等效电流模型,该模型简洁有效地描述了ＨＴＳ永磁体磁场大小及磁力性能,有助于组合永磁体的设计计算。     

3/3相双绕组发电机系统的等效电路模型

整流桥的存在使3／3相双绕组发电机系统成为非线性系统，发电机始终处于非对称运行状态，为了对此进行解析分析，将3／3相双绕组发电机的d,q轴变量分解为低频分量和高频分量分别加以处理，忽略转子回路电阻对高频电流和阻尼绕组对低频分量的作用，在d,q轴超瞬变电抗近似相等的条件下，分别建立了3／3相双绕组发电机系统从整流绕组侧和交流绕组观察的等效电路模型，给出了模型中等效发电机的Park程，稳态运行矢量图及相应稳态量的计算方法，该模型可用于系统稳态和似稳态过程的分析计算。     

CALCULATION OF THE LOCKED ROTOR CURRENTS AND TORQUE IN INDUCTION MACHINES

ABSTRACT

The analysis of certain end-winding vibration problems requires an accurate knowledge of the transient currents in an induction motor during the early part of the start-up period where the time rates of change of current are the highest. This paper details the derivation of expressions for the winding currents assuming that the machine remains at rest during the period of interest. Under these conditions, the currents are shown to contain three time dependent components, one of which is oscillatory, the remaining two being damped exponentials. The rates of decay of the exponential components are particularly important to some aspects of the vibration problem and they are shown to be dependent on the winding resistances and inductances and also upon the degree of coupling between stator and rotor.