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.     

Emerging Electric Machines with Axially Laminated Anisotropic Rotors: A Review

ABSTRACT

This paper presents a class of multiphase electric machines with axially laminated anisotropic (ALA( passive rotors. Unipolar, two-level bipolar, and sinusoidal current modes are identified. The reluctance variation in ALA rotor is computed for a wide range of airgaps and pole pitches. High ratios of inductances along d and q axes yield high torque densities. Special attention is paid to the sinusoidal current mode through a quantitative comparison with the induction and PM synchronous counterparts with the same stator. It is demonstrated that the ALA rotor sinusoidal current synchronous motor is superior in all respects to the induction motor and almost equals the performance (torque density, efficiency, power factor( the PM synchronous motor.     

Optimal current control methods of a non‐salient pole hybrid field‐synchronous motor for energy‐efficient and wide speed‐range operation

This paper proposes new practical optimal current control methods for a newly emerging class of non‐salient pole synchronous motors with hybrid rotor fields by both permanent magnet and winding. In practical situations with limited voltage, the extensively used permanent magnet synchronous motor hardly achieves an ideal performance that allows simultaneously both low‐speed high‐torque and wide speed‐range operations, due to its constant magnet field. Hybrid field synchronous motors (HFSM) have recently emerged to achieve ideal performance as practical motors with controllable hybrid rotor field. For HFSM, the same torque can be produced by a variety of currents due to nonlinearity between torque and currents. Consequently, appropriate determination of a set of stator and rotor current commands plays a key role in achieving possible energy‐efficient and wide speed‐range operation. Proposed methods determine the current commands corresponding to a given torque command such that total winding copper loss due to stator and rotor currents can be minimized if the exact solution exists; the best approximate torque can be produced if no exact solution exists. The determined current commands are optimal in the sense of energy efficiency or degree of approximation in wide speed‐range operation under voltage limit. New real‐time recursive algorithms searching the optimal current solution are also given. The proposed methods are analytical but practical, and their usefulness is verified through experiments. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(1): 70–83, 2006; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20156     

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.     

基于扩展卡尔曼滤波的永磁同步电机无传感器矢量控制

为实现永磁同步电机(PMSM)的无传感器控利,引入扩展卡尔曼滤波对转子位置和转速进行估计,该算法通过测量电机端电压和定子电流在线估计转子位置和速度.为提高PMSM转速估计精度,以两相静止坐标系下考虑转动惯量的PMSM实际模型为递推估计对象,搭建转速、电流双闭环的无传感器矢量控制系统.仿真结果表明,系统状态估计精度较高、运行稳定、超调小、动静态性能良好.     

A FULLY DIGITAL SENSORLESS DIRECT TORQUE CONTROL SYSTEM FOR SYNCHRONOUS MACHINE

ABSTRACT

A new sensorless controller based on direct torque control, for a synchronous machine is proposed. Using direct torque control, stator resistance is the only parameter of the machine which should be known. The use of reactive torque control simplifies the field current control loop. Initial stator induced currents are used to estimate the initial stator flux. The outputs of the control system are switching commands of stator inverter and rotor chopper.     

PERFORMANCE ANALYSIS OF THE REPULSION MOTOR CONTROLLED VIA ROTOR TRIAC

ABSTRACT

This paper investigates the solid state speed control of a repulsion motor using a triac in the rotor circuit. The speed control is accomplished by varying the triac firing angle. In addition, this paper investigates the harmonic contents of the rotor current, stator current and rotor voltage The waveforms of these variables were generated and then analyzed numerically for their harmonic content using a Fouries Series Subroutine. The results were validated by comparison with obtained experimental results. More over, the harmonics generated using this type of speed control are compared with those generated when the motor is controlled via a triac in the stator cicuit.     

定子电阻对无速度传感器系统的影响及其在线调整

分析了定子电阻对无速度传感器系统的影响,指出定子电阻变化引起的定子磁链稳态误差与电阻误差值、电流幅值、同步角速度和初始误差值有关,最终影响磁场定向和转速估算的准确性.基于定子磁链处于稳态时,转子电流矢量应与转子磁链矢量垂直的原则,提出了一种闭环形式的定子电阻在线调整方法.该方法使用比例(P)调节器以控制目标量为零,调整定子电阻值.仿真结果表明在转速给定10 r/min,定子电阻线性增加和减小50%的情况下,转速波动不超过10%,定子磁链幅值偏差在0.02～0.05 Wb之间,定子磁链的相位偏差不超过0.2 rad.     

NEW 4/6-POLE RELUCTANCE MOTORS

ABSTRACT

A new type of reluctance-rotor having four asymmetrical segments is introduced and fully explored for 4/6-pole operation. This rotor is derived from the novel magnetic circuits recently described [7] and analysed [8] by the present authors. Predicted variations of synchronous performance with certain important machine-parameters are given, and the new rotors are shown to be superior to earlier designs for this speed ratio, one with symmetrical segments [4], and one with salient-poles [5J. Test results of two motors for constant torque and constant horsepower applications employing P.A.M. stator windings are presented, together with some experimental verification of theory. The new motors are believed to have the potential for several industrial applications.     

POWER FLOW ANALYSIS AND EFFICIENCY OPTIMIZATION OF A DOUBLY FED SYNCHRONOUS MACHINE

ABSTRACT

This paper deals with the energy balance of the doubly fed synchronous machine (DFSM). The proposed method is based on the principle which consider that the electro–mechanical conversion takes place between stator circuits and the machine shaft, so that the electrical power applied to rotor circuits is taken as a command. From this point of view, the study stresses are:

• Stability,

• A low ratio of the rotor command referred to the converted energy,

• High efficiency.

Results are presented in the rms value of rotor applied voltage (V_2a) – angle between the stator and the rotor voltages vectors (5) plane. We have found, when we vary the slip (s), that the high efficiency areas move in such way that the ratio of s over V_2a remains constant (which means a constant rotor flux).     

Control Algorithm for the Inverter Fed Induction Motor Drive with DC Current Feedback Loop Based on Principles of the Vector Control

ABSTRACT

This paper brings out a control algorithm for VSI fed induction motor drives based on the converter DC link current feedback. It is shown that the speed and flux can be controlled over the wide speed and load range quite satisfactorily for simpler drives. The base commands of both the inverter voltage and frequency are proportional to the reference speed, but each of them is further modified by the signals derived from the DC current sensor. The algorithm is based on the equations well known from the vector control theory, and is aimed to obtain the constant rotor flux and proportionality between the electrical torque, the slip frequency and the active component of the stator current. In this way, the problems of slip compensation, Ri compensation and correction of U/f characteristics are solved in the same time. Analytical considerations and computer simulations of the proposed control structure are in close agreement with the experimental results measured on a prototype drive.     

POWER CONTROLLER FOR A WIND-TURBINE-DRIVEN TANDEM INDUCTION GENERATOR

ABSTRACT

A controller for delivering either constant power or maximum power from a wind-turbine-driven grid connected induction generator with double stator windings, one fixed and the other able to be physically rotated, and a squirrel-cage rotor common to both stators is described. The load torque of the generator is controlled by varying the angular displacement between the two stators. The generator can feed power to the grid at variable speed and constant frequency and is termed a Tandem Induction Generator.

Dynamic models for the wind energy conversion system are proposed for both controlled and uncontrolled operation to predict changes in shaft speed to shifts in wind speed using data pertaining to a commercial wind turbine. Results based on laboratory tests on a 1hp tandem machine driven by a dc motor demonstrating the feasibility of both controllers are presented. A steady state model of the tandem generator is also proposed and compared to measurements made on the test machine.     

Rotor position estimation method of IPMSM using HF signal injection and sliding‐mode controller

This paper presents a simplified algorithm for the estimation of rotor position. A high‐frequency (HF) sinusoidal voltage is injected into the stator of a motor. An interior permanent magnet synchronous motor (IPMSM) has spatial saliency because the d‐ and q‐axis inductances are different from each other. The injected HF voltage is influenced by this saliency. Therefore, the rotor position is included in the stator current of the motor. The proposed method uses different synchronous reference frame transformations (SFTs) to extract the rotor position error between the estimated value and actual value. Also, a sliding‐mode controller is used for robustness against parameter variation and external disturbance. The experimental results confirm the effectiveness of the proposed method by showing waveforms of the rotor speed and position with load conditions. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

ANALYSIS OF THE INTERFERENCE SYNCHRONOUS MACHINE

ABSTRACT

Interference synchronous machines operate at different speeds of the fundamental air gap field and of the rotor, because the fundamental permeance wave is produced by interference of open stator and rotor slots the numbers of which being slightly different. In the literature different names are used for this remarkable electrical machine (“Synchronous inductor motor”, “Vernier reluctance motor”). Interference synchronous machines are used as homopolar frequency generators with an axial field coil, as continuous running reluctance motors and as single- or double, - stack step motors with an axial permanent magnet.

In this paper the field of the interference synchronous machine is analysed by field wave theory. Speed,phase angle and length of the largest field waves reveal how synchronous and cogging torques are produced. Voltage and torque equations are derived by axis theory from the simplest model that is possible with five rotor teeth. The theory is applied on a fifty rotor teeth double-stack step motor. The inductances are determined by a difference method field calculation. The torque of the motor is then calculated and compared with measured values.     

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.     

PMSG风力发电系统转速估计算法的研究

提出了一种无传感器直驱式永磁同步风力发电机控制系统的转子速度估算法。该算法可由简单的定子磁通方程推导,且只需检测定子电压和电流。定子磁通估算通过基于定子电压模型的可编程低通滤波器而设计,建立了基于递归最小二乘法的电机转速辨识模型,并将实时辨识的电机转速用于转子位置观测和转子磁场定向矢量控制。仿真结果表明,实现了最大功率跟踪控制,验证了控制算法的有效性和可行性。     

A NOVEL FORM OF SYNCHRONOUS MACHINE EXCITATION

ABSTRACT

A machine is described which utilises the flux pulsations caused by stator slotting to produce a rotor excitation current which can react with the main flux wave to develop synchronous torque. This attractive possibility could result in a brushless, self-excited, synchronous motor, without the requirement of an exciter, and putting to good use what is usually regarded as a source of parasitic loss. The paper presents the performance characteristics and results of tests on a prototype. Methods of calculation of behaviour are presented which could be used to investigate the commercial viability     

IMPACT OF SLOT HARMONICS ON LOSSES OF HIGH-SPEED PERMANENT MAGNET MACHINES WITH A MAGNET RETAINING RING

ABSTRACT

This paper presents an analytical method for determining the harmonic content in the flux pattern of permanent magnet synchronous machines due to the slotting of the stator. The analysis based on a rotor construction with magnets radially magnetized and a retaining ring to support them against the centrifugal forces. Expressions for the eddy current losses in the magnets and their retaining ring are derived in terms of the machine dimensions and the physical properties of magnets and ring. The accuracy of the method is examined by comparison with numerical flux calculations using finite element method. The impact of some physical quantities like machine speed and magnet conductivity on the slot harmonics losses is examined aiming to exhibit the role of the magnet retaining ring in contributing to these losses     

基于串级绕组的新型永磁同步电机起动性能分析

针对异步起动永磁同步电机在起动过程中电流大,起动转矩小的问题,本文提出一种串级绕组理论。利用定子串级绕组产生的谐波磁场与转子分匝线圈组相互作用,优化电机的起动性能。文章通过阐述串级绕组理论,给出电机模型与定转子设计方案,并基于等效电路分析样机实际工作原理,最后运用有限元法从样机的转速、空载起动性能、带负载起动、气隙磁密和堵转转矩五个方面进行仿真。试验结果表明,应用串级绕组理论可以在提高起动转矩的同时降低起动电流,抑制起动时定子电流对转子永磁体的退磁效应,并且电机的稳态性能保持不变。