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.     

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.     

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.     

ROLE OF TORQUE ANGLE IN INVERTER-FED INDUCTION MOTOR DRIVES

ABSTRACT

It is shown from the induction motor differential equations that changes in load torque, speed reference and torque angle are accompanied by a transient change in the speed of the air-gap mmf. The time constant associated with the torque angle change is different for a voltage source and a current source inverter-fed induction motor. This aspect throws light on the instability of current source inverter-fed induction motor on open loop operation. Evidently, the solution to overcome this instability is to use the torque angle for feedback control. It is proved that torque angle feedback alone is not sufficient for stabilization of the current source inverter-fed induction motor.     

Modified direct torque control method for induction motor drives based on amplitude and angle control of stator flux

This paper proposes design and implementation of a direct torque controlled induction motor drive system. The method is based on control of separation between amplitude and angle of reference stator flux for determining reference stator voltage vector in generating PWM output voltage for induction motors. The objective is to reduce electromagnetic torque ripple and stator flux droop which result in a decrease in current distortion in steady-state condition. In addition, the proposed technique provides simplicity of a control system. The direct torque control is based on the relationship between instantaneous slip angular frequency and rotor angular frequency in adjustment of the reference stator flux angle. The amplitude of the reference stator flux is always kept constant at rated value. The system has been implemented to verify its capability such as torque and stator flux responses, stator phase current distortion both during dynamic and steady state with load variation, and low speed operation.     

TORQUE PRODUCTION IN ac MOTORS WITH CONSTANT CURRENT SUPPLY

ABSTRACT

Basic theory is presented concerning the production of torque in synchronous motors and induction motors under conditions of constant current supply. Simple methods are described for treating the effects of magnetic saturation, which are important at high currents. It is shown that, for a given stator current, a synchronous motor produces more torque than an induction motor, albeit with higher air-gap flux. Examples illustrate the variation, due to saturation, of the optimum torque angle of synchronous motors with cylindrical and salient rotors.     

AN ELECTROMECHANICAL NETWORK MODEL FOR FREQUENCY CONTROLLED INDUCTION MOTORS

ABSTRACT

An electromechanical network model valid for small values of slip under steady state and dynamic conditions is given for frequency controlled induction motors. The model has been developed using the perturbation equations in the synchronously rotating reference frame and neglecting stator resistance and stator transients. Bode plots of incremental transfer functions relating speed and load torque as well as speed and stator frequency under constant volts/Hz control mode obtained from the exact and approximate models are compared with those of the electromechanical network model. The usefulness of the model in steady state and dynamic studies is discussed     

反电势算法的永磁同步电机无位置传感器自启动过程

提出一种基于反电势积分法的永磁同步电机无位置传感器自启动控制策略,其启动阶段采用速度开环、电流闭环控制,正常运行阶段以速度－电流双闭环控制,采用id=0,iq=常数的控制方式.状态转换过程中,以估测器估测的转子位置与给定坐标系的相位差值为参考变量,对定子轴电流进行控制,以使相位差值收敛于0,从而实现速度、转矩的平顺切换...     

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.     

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.     

Development of torque and flux ripple minimization algorithm for direct torque control of induction motor drive

Direct torque control (DTC) is known to produce quick and robust response in AC drives. However, during steady state, notable torque and flux ripple occur. They are reflected in speed estimation, speed response and also in increased noise. This paper proposes a new control algorithm, which provides decoupled control of the torque, and flux with constant inverter switching frequency and a minimum torque and flux ripple. Compared to the other DTC methods, this algorithm is much simpler and has less mathematical operations, and can be implemented on most existing digital drive controllers. Algorithm is based on imposing the flux vector spatial orientation and rotation speed, which defines the unique solution for reference stator voltage. This paper contributes (a) Calculation of stator flux vector, torque and flux increments (b) The position of new stator flux vector determination (c) Calculation of the stator reference voltage (d) comparison of errors of different control strategies. In this paper, computer simulations and experimental results have been discussed for the proposed algorithm.     

混合励磁双凸极电机提前角控制策略研究

为提高混合励磁双凸极电机在半桥功率变换器供电方式下高速运行时的输出转矩,以定、转子极弧为15°/20°的12/8极混合励磁双凸极电机为研究对象,在对标准角控制策略研究基础上,提出了提前角控制策略,并对不同提前角对电机相绕组电流和输出转矩的影响进行了理论分析和仿真研究,达到了预期目的。     

异步电动机直接转矩控制中高性能磁链观测器研究

磁链观测是实现高性能电机传动系统的关键环节,为解决传统直接转矩控制系统中定子磁链观测方法的局限性,设计了高性能全阶磁链观测器实现了定子磁链在全速度范围,尤其在极低速时的准确观测。仿真和实验结果表明:此方案对定子磁链的观测效果明显优于传统的观测方法,降低了稳态时转矩、磁链和速度的波动,并对电机参数的变化具有良好的鲁棒性。     

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.     

模糊调节电压矢量角度和幅值的SPMSMDTC系统

针对永磁同步电机直接转矩控制转矩和磁链脉动较大的问题,提出了模糊调节电压矢量角度与幅值表面式永磁同步电机模糊直接转矩控制系统,采用模糊控制器和空间矢量调制技术取代传统直接转矩控制系统的滞环比较器和开关表输出电压矢量。模糊控制器输入量为磁链和转矩误差,输出量为输出电压矢量的角度和幅值。基于电压矢量幅值和角度对磁链和转矩的变化影响规律设计了模糊控制规则表。为了进一步抑制转速为负时的转矩脉动,设计自适应模糊直接转矩控制系统。仿真结果表明:模糊调节电压矢量角度与幅值的直接转矩控制系统可实现四象限运行,电机系统运行良好,仅在转速为负时,转矩脉动略有增大。自适应模糊直接转矩控制系统运行效果良好,在四象限内均可较好抑制转矩和磁链脉动。     

感应电动机系统的变结构反推控制研究

感应电动机系统的矢量控制为了进行电流(或电压)的3/2(或2/3)坐标变换需要进行转子转差或磁链角的计算，转子转差的计算容易受转子电阻变化的影响，而磁链角的直接计算容易受定子电阻变化的影响，因此避免转子转差或磁链角的计算对于感应电动机系统的控制是非常有意义的。文中把变结构反推控制运用于感应电动机系统的转矩和磁链控制，设计方法避开了转子转差或转子磁链角的计算，通过一定的坐标变换，基于定子侧的静止坐标系实现转矩和磁链的解耦控制。变结构反推控制设计能够实现快速的速度、转矩和磁链的渐近跟踪，同时系统控制器能够保证系统性能在电动机参数和外部负载变化时具有强的鲁棒性，通过Matlab仿真验证了系统设计的有效性和可行性。     

一种新型感应电动机直接转矩控制系统的研究

近几年来随着鲁棒控制的发展,线性时变参数(LPV)控制方法也得到了一定的发展,并在处理非线性系统上取得了一些成果。将LPV控制引入感应电机直接转矩控制,采用多胞技术设计了一LPV转子电流估计器,从而利用定子电流的测量值和转子电流的估计值计算定子磁链和电磁转矩,实现全速范围内定子磁链的有效测量。最后通过一仿真实例验证该方法的正确性和有效性。     

直接转矩控制永磁同步发电机相位自校正型定子磁链观测器

直接转矩控制永磁同步发电具有电磁转矩和直流电压输出动态响应快等优点,但这些优点的实现需要准确的定子磁链。实际发电机参数在一定范围内随工作点变化而变化,这就要求定子磁链观测器对这些参数变化具有很强的鲁棒抑制特性。该文提出一种新型定子磁链观测器,该观测器借助有效磁链概念计算出转子磁极位置角观测值,基于此将定子磁链电压模型和电流模型联系起来,无需转子速度信息;为了进一步降低观测的定子磁链相位误差,将观测的定子电流矢量与实际定子电流矢量乘积结果送给PI调节器,利用PI输出值对转子位置角观测值进行校正。实验结果表明,采用该文提出的定子磁链观测器在无需转子速度及参数辨识情况下,对电机参数变化及模拟量采样误差具有很强的鲁棒抑制特性,可以获得准确的磁链观测值,实现电磁转矩和直流发电电压的快速而平稳控制。     

A MICROPROCESSOR BASED CONTROL OF DC MOTOR DRIVES USING PROPORTIONAL-INTEGRAL (P-I) AND INTEGRAL-PROPORTIONAL (I-P) CONTROLLERS

ABSTRACT

This paper presents a Microprocessor based Digital control system for a DC Motor Drive using the commonly used P-I (Proportional-Integral) controller and a relatively new I-P (Integral-Proportional) controller. The relative merits and demerits of both P-I and I-P controllers are evaluated and compared. Important aspects, such as, the starting speed and current response; responses to step changes in the speed reference and the load torque; error signal processing; gain sensitivity, etc. are analyzed. It is shown that the I-P control scheme offers some distinctive advantages over the P-I control scheme. Some experimental and simulation results are also presented.