DESIGN PROCEDURE FOR A SMALL SELF-CONTROLLED INVERTER-FED SYNCHRONOUS MACHINE WITH A PERMANENT MAGNET ROTOR

ABSTRACT

The object of the paper is the analytical study of a small permanent magnet inverter fed synchronous machine in order to find an optimal design. The inside flux density created by both the stator windings and the rotor magnet is calculated. This allows the design of the stator of the machine. Then, the variation of the torque as a function of the inner diameter is derived for a given outer diameter of the rotor (6.5 mm) leading to the rotor dimensions. Our final choice has been 2.75 mm corresponding to a torque of 68 10^?4 mN (experiment: 69). Nominal speed is around 6000 rpm for a 12 V direct current supply voltage. A simple model of the machine is developed and results are shown.     

A DYNAMIC INDUCTION MOTOR MODEL INCLUDING SPACE HARMONICS

ABSTRACT

An induction motor model is presented which can be used to compute dynamic characteristics and which includes both asynchronous and synchronous parasitic torque effects owing to space harmonics. A new transformation is given which eases computation and enables the stability of the synchronous parasitic torque to be determined. The model is applied to the computation of the direct on line starting characteristic for a four pole, three phase cage machine with 36 stator slots and 28 rotor slots.     

TORQUE VECTOR CONTROL (TVC) OF AXIALLY-LAMINATED ANISOTROPIC (ALA) ROTOR RELUCTANCE SYNCHRONOUS MOTORS

Abstract

Axially-laminated anisotropic (ALA) rotor reluctance synchronous motors (RSMs) have been proved recently capable of higher torque density, higher power factor and efficiency compared to their induction motor counterpart with the same stator. Vector current control systems have been proposed for such drives, based on maximum available torque constant current angle or minimum current for a given torque constant current angle or combined current-voltage control. In an effort to do away with the current controller limitations, especially in the high speed region, the paper proposes a torque vector control (TVC) system which is a direct stator flux and torque control through a table of optimum switchings in the voltage-source PWM inverter. A sliding mode speed controller is added. Extensive digital simulations are presented. They demonstrate the TVC fast response, wide speed range and load rejection performance.     

TORQUE VECTOR CONTROL (TVC) OF AXIALLY-LAMINATED ANISOTROPIC (ALA) ROTOR RELUCTANCE SYNCHRONOUS MOTORS

Abstract

Axially-laminated anisotropic (ALA) rotor reluctance synchronous motors (RSMs) have been proved recently capable of higher torque density, higher power factor and efficiency compared to their induction motor counterpart with the same stator. Vector current control systems have been proposed for such drives, based on maximum available torque constant current angle or minimum current for a given torque constant current angle or combined current-voltage control. In an effort to do away with the current controller limitations, especially in the high speed region, the paper proposes a torque vector control (TVC) system which is a direct stator flux and torque control through a table of optimum switchings in the voltage-source PWM inverter. A sliding mode speed controller is added. Extensive digital simulations are presented. They demonstrate the TVC fast response, wide speed range and load rejection performance.     

HARMONIC ANALYSIS OF INDUCTION MOTORS WITH STATOR FAULTS

ABSTRACT

In the paper stator faults are analyzed by means of a procedure based on the space-vector theory. The used approach, due to Stepina, allows to consider separately each conductor of every single slot and therefore to take easily into account the winding dissymmetry.

The interactions among the different harmonic fields are studied by starting from the topological structure of windings and the harmonic analysis of the currents and of torque Is carried out.

The method is tested to numerical computations of steady-state currents for an induction machine with different positions of stator short-circuits.

Finally the procedure is validated by using an experimental squirrel cage machine, having stator windings constructed so as to realize different short-circuits.     

Improved Performance of a Schrage Motor by Tertiary Tuning

ABSTRACT

Tertiary capacitor tuning in the stator of the schrage machine is developed to increase the air gap mmf, improve the generating and motoring efficiency and power factor, increase the full-load torque of the machine, and keep the machine as a wide range speed transducer.

The system analysis based on a developed equivalent circuit is given with experimental verification.

The analysis and characteristic curves show the effect of the brush axis variation. The advantages of tertiary capacitor tuning over brush axis shifting are shown.     

基于转矩预测控制的无刷双馈电机直接转矩控制系统

在研究无刷双馈电机直接转矩控制调速系统的基础上,针对无刷双馈电机直接转矩控制转矩脉动大的问题,提出了适用于该种电机的转矩预测法.仿真结果表明,该方法能有效地减小转矩脉动、改善定子电流波形,具有良好的动、静态性能.     

ESTIMATION OF ROTOR VOLTAGE VECTOR ON THE DOUBLE EXCITED INDUCTION MACHINE USED IN WECS

ABSTRACT

The aim of this work is to estimate and control the rotor voltage of a double excited induction machine DEIM that is necessary to operate it as a generator in wind energy conversion systems (WECS), with speed range extending from the sub synchronous range to double the synchronous speeds. For efficient power generation, the DEIM is to be operated at its rated electric torque which is realised by having both rotor and stator currents magnitudes constant throughout the whole operating range. Also the angle between the rotor current and stator current is kept constant irrespective of the rotor speed.     

MODIFIED ASYNCHRONOUS CASCADE MACHINE SYSTEM

ABSTRACT

The modelling of the modified asynchronous cascade machine system is done in order to study the features of such system under field-oriented frame of reference. The modified machine system has two stator windings and two sections of rotor winding on the same shaft One of the stator windings is connected to the ac network while the other winding is connected to an inverter capable of controlling power flow in both directions. This system can be operated in a wide speed range and both sections of the rotor winding can produce useful torque.     

基于空间矢量调制的电励磁磁通切换电机转矩角增量控制策略

电励磁磁通切换电机具有转子结构简单坚固,磁链双极性、反电势正弦度高的优点,是一种新型的无刷交流电机。交流电机的2种经典控制策略中,相对于矢量控制(vectorcontrol,VC),直接转矩控制(direct torque control,DTC)具有算法结构简单、动态性能好的优点,但是其电流谐波含量高、转矩和磁链脉动大。为同时提高调速系统的动、静态性能,该文研究了一种基于空间矢量调制(space vectormodulation,SVM)的电励磁磁通切换电机转矩角增量控制策略,定义转矩PI环的输出为转矩角变化量,通过合成空间矢量对定子磁链矢量角增量的直接平滑调节,实现了对电磁转矩的直接线性调节。比较了最大合成空间矢量和基本前进矢量改变定子磁链矢量角的能力。在一台电励磁磁通切换电机上,利用TMS320F2812控制系统进行了传统DTC和该文提出算法的比较实验,验证了所提算法的正确性和有效性,新算法具有优良的动、静态性能。     

Fuzzy controller for inverter fed induction machines

An induction machine operated with a direct self controller (DSC) shows a sluggish response during startup and under changes of torque command. Fuzzy logic is used in conjunction with direct self control to minimize these problems. A fuzzy logic controller chooses the switching states based on a set of fuzzy variables. Flux position, error in flux magnitude and error in torque are used as fuzzy state variables. Fuzzy rules are determined by observing the vector diagram of flux and currents. The operation of the direct self controller becomes difficult at low speeds due to the effect of change in stator resistance on the flux measurements. To improve the system performance at low speeds a fuzzy resistance estimator is proposed to eliminate the error due to the change in stator resistance. At constant flux and torque commands any change in stator resistance of the induction machines causes an error in stator current. This error is utilized by the fuzzy resistance estimator to correct the stator resistance used by the controller to match the machine resistance. Both a fuzzy controller and fuzzy resistance estimator are simulated for a 3 HP induction motor. The simulation results demonstrate a good performance     

基于Matlab/Simulink的异步电机直接转矩控制系统仿真

对Simulink自带的电机模块存在的问题进行了阐述.在异步电机数学模型的基础上,利用Matlab/Simulink软件建立了电机模型和直接转矩控制系统模型.详细介绍了系统的主要模块.通过仿真实验,得到了定子磁链、定子电流、转速、转矩的仿真波形,验证了控制策略的正确性.     

Torque Vector Control (TVC)-A Class of Fast and Robust Torque-Speed and Position Digital Controllers for Electric Drives

ABSTRACT

This paper presents the fundamentals of a new class of torque speed and position controllers for electric drives, characterized by the association of a modified sliding mode position (speed) controller and stator flux control through a unique table of optimal conduction sequence to fire directly the static power converter SCR switches. Robustness is provided by the sliding mode controller and stator (instead of rotor) flux vector estimation while control precision is secured by the torque pulsation controller. Fast response is obtained through the table of optimal conduction sequence which leads to the fastest response available through a stator flux vector (or stator accelerating field) control obtained without the transformation of coordinates or special techniques. The control computation time (costs) is drastically reduced in comparison with PWM transvector (or field accelerating) methods while the performance in terms of precision, response and robustness are better.     

AN ANALYSIS OF SHADED POLE INDUCTION MOTORS WITH INCREASED STARTING TORQUE

ABSTRACT

A method of analysis of shaded pole induction motors with ununiform airgap is described. For the analysis, a dq model of a generalised machine theory with any number of stator windings arranged in an arbitrary way on the stator and ununiform airgap is chosen. The analysis involves resolution into a harmonic series, together with complex matrix inversion. Results of computational study of the effect of changes of airgap profile on the performance characteristics are presented. It is shown that by increasing the airgap under the part of a pole which la opposite to the shading coils, an increased starting torque can be obtained.     

五相感应电机直接转矩控制研究

在对五相感应电机直接转矩控制中空间电压矢量进行详细分析的基础上,给出了一套系统调速整体控制方案。在该控制系统中,磁链和转矩均是闭环控制,其值在一个微小的滞环内波动,稳态情况下,其指令值与实际值可认为相等。此时,定子电流空间矢量幅值是一定值,该值变化可认为是由定子电阻变化引起的,由此给出了一套简单、易于实施的定子电阻在线辨识算法。仿真结果表明,提出的控制方案在理论上和实际上是可行的。     

INDUCTION MOTOR DRIVE STABILIZATION WITH STATOR CURRENT FEEDBACK

ABSTRACT

The use of state feedback to control Induction motor drive systems is examined. Using the machine currents and speed as the system states, a general linearized formulation of the problem is derived. This formulation has the advantages of previous forms based on complex variable analysis, but is not subject to the limitations of that method.

The proposed model Is used to study machine control with stator current feedback. The results show that stator current feedback can be used to improve the dynamic characteristics of the drive system. Comparisons of stator current control with the uncontrolled machine and with the slip controlled machine are presented over the range of operating speed, load, and inertia. In all cases, advantages of current controlled operation can be seen.     

双三相异步电动机直接转矩控制定子磁链观测的研究

介绍了一种新型双三相异步电机直接转矩控制(DTC)的策略,构建了由2套互差30°(电角度)、中点隔离的对称三相绕组所组成的双三相异步电机模型.运用PI调节器对定子磁场实施同步控制.通过自适应定子磁链观测(ASFO)来提高磁通的估计值,并根据磁链与转子位置关系估计出转子的位置.该方法具有良好的暂态与稳态性能,有效地降低了...     

Steady-state performance of a line-start synchronous reluctance motor with capacitive assistance

This paper sets forth the steady-state performance analysis of a connection scheme that improves the power factor and torque with a lower magnetizing current for a line-start synchronous reluctance motor. The machine stator winding is split into two equal halves, one connected to the mains and the other connected to a balanced capacitor. Performance of the machine is improved if the capacitor value is such that the winding to which it connected operate at or very close to resonance in the d-axis. Current in both windings contributes positively to torque production and external control circuitry is not required. Steady-state equations arising from the d–q model gives a direct insight on the operating limits and how this capacitance aids the machines torque and power factor by boosting its direct axis reactance while the quadrature axis reactance remains fairly constant. An equivalent circuit is also deduced from the steady-state equations from which an explicit expression for input impedance of the new machine can be derived. Conditions for unity-power factor at varying load conditions are also examined. A comparison with conventional single-winding synchronous reluctance motor is given. Such comparison is fair because both machines have the same amount of copper and iron. Experimental results are provided to validate the analytical results.     

EFFECT OF THE COMMUTATION ON THE PULSATING TORQUES IN POLYPHASE MACHINES FED FROM CURRENT-SOURCE INVERTERS

ABSTRACT

A new simple method for the preliminary calculation of pulsating torques in synchronous and asynchronous machines fed from current-impressing inverters is shown. The treatment is based on the analysis of the stator and rotor current-distribution waves represented as space phasors in a rotating coordinate system. The mean values of these complex space phasors depend on the fundamental harmonic of the stator currents and produce the wanted performance of the machine; the variable components, changing periodically, cause the oscillating torques. As the necessary data are obtained from the usual phasor diagram, and the torque calculation is very simple, the formulae can be easily evaluated for many operating states on which the oscillating torques strongly depend. The attention is focused on the effect of the commutation.     

IPM Traction Machine With Single Layer Non-Overlapping Concentrated Windings

In this paper, an interior permanent-magnet traction drive machine with single layer non-overlapping concentrated stator winding is analyzed. In the single layer winding design, the number of stator slots and a winding factor are specifically considered. Moreover, the effect of varying the coil pitch on the winding factor and torque pulsations is investigated. A new calculation method is proposed, whereby the constant torque and field-weakening speed characteristics of the machine drive can be predicted using torque and flux linkage functions. The measured and predicted field-weakening performance of a 150-kW direct traction drive machine is presented.