TORQUE AND FLUX TRACKING OF INDUCTION MOTORS

The problem of torque tracking and rotor flux norm regulation of induction motors perturbed by an unknown constant load torque was recently solved with an observer-based controller in Reference 5. In this paper we extend this result to treat the practically important case when the rotor flux norm is required to follow a time-varying reference. The controller design follows the passivity-based approach and proceeds in two steps: first, we define a target closed-loop dynamics compatible with the physical model of the motor that delivers the desired rotor flux and torque. Second, we propose a nonlinear dynamic output feedback controller that ensures this behaviour is asymptotically achieved. A proof of global tracking is given under the assumption of known motor parameters. Some key features of our physically based design are that the control law does not require measurement of rotor variables, is always well defined and does not rely on (intrinsically nonrobust) nonlinear dynamics cancellation. A corollary of our main result is the proof that a slight modification of the classical indirect field-oriented controller ensures global tracking for current-fed machines. © 1997 by John Wiley & Sons, Ltd.     

A speed-sensorless indirect field-oriented control for induction motors based on high gain speed estimation

The authors design a new speed sensorless output feedback control for the full-order model of induction motors with unknown constant load torque, which guarantees local asymptotic tracking of smooth speed and rotor flux modulus reference signals and local asymptotic field orientation, on the basis of stator current measurements only. The proposed nonlinear controller exploits the concept of indirect field orientation (no flux estimation is required) in combination with a new high-gain speed estimator based on the torque current tracking error. The estimates of unknown load torque and time-varying rotor speed converge to the corresponding true values under a persistency of excitation condition with a physically meaningful interpretation, basically equivalent to non-null synchronous frequency. Stability analysis of the overall dynamics has been performed exploiting the singular perturbation method. The proposed control algorithm is a “true” industrial sensorless solution since no simplifying assumptions (flux and load torque measurements) are required. Simulation and experimental tests show that the proposed controller is suitable for medium and high performance applications.     

A global tracking control for speed-sensorless induction motors

The problem of controlling an induction motor without rotor speed measurements is addressed. Arbitrary smooth reference signals for rotor speed and rotor flux modulus are required to be tracked globally (i.e. from any initial condition). A global second-order tracking control is obtained, which is based on a novel rotor speed observer. Simulation results are provided which illustrate the controller performance.     

A nonlinear tracking control for sensorless induction motors

We propose a novel tracking control for induction motors in which only stator currents are used for feedback. Local exponential rotor speed and flux modulus tracking are achieved for any constant reference value and for restricted time-varying reference signals; any known motor parameters values (including constant load torque) and any initial condition, including rotor speed and fluxes, belonging to an explicitly computed domain of attraction are allowed.     

Adaptive Nonlinear Control of Wind Energy Conversion System Involving Induction Generator

This paper presents a theoretical framework for adaptive control of a wind energy conversion system (WECS), involving a squirrel cage induction generator (SIG) connected with an AC/DC/AC IGBT‐based PWM converter. A multi‐loop nonlinear controller is designed to meet two main control objectives, i.e., (i) speed reference optimization in order to extract a maximum wind energy whatever the wind speed, and (ii) power factor correction (PFC) to avoid net harmonic pollution. These objectives must be achieved despite the mechanical parameters uncertainty. First, a nonlinear model of the whole controlled system is developed within the Park coordinates. Then, a multi‐loop nonlinear controller is synthesized using the adaptive backstepping design. A formal analysis based on Lyapunov stability is carried out to describe the control system performances. In addition to closed‐loop global asymptotic stability, it is proven that all control objectives (induction generator speed tracking, rotor flux regulation, DC link voltage regulation and unitary power factor) are asymptotically achieved.     

异步电机的非线性自适应反步控制器设计

针对描述异步电机的动态特性方程,在一些系统参数未知的情况下,应用分离子系统的方法和反向递推技术,设计了非线性自适应控制器.实现了电机对给定转速信号和磁通量信号的输出渐近跟踪控制,保证了整个系统的全局有界稳定性.仿真结果验证了该自适应控制策略的有效性.     

A GLOBAL EXPONENTIAL OUTPUT‐FEEDBACK CONTROLLER FOR INDUCTION MOTORS

In this paper, we design an output‐feedback, rotor position/rotor flux controller for the full‐order, nonlinear dynamic model of an induction motor. The singularity free controller does not require measurement of rotor flux or rotor velocity and yields global exponential rotor position and rotor flux tracking. The proposed controller is termed output‐feedback due to the inexpensive/simplistic manner in which stator current measurements can be obtained (e.g., the most primitive method of measuring current can be achieved through simple voltage measurements across known resistive elements). Experimental results are included to verify the effectiveness of the proposed controller.     

An output feedback globally stable controller for induction motors

We present a globally stable nonlinear dynamic output feedback controller for torque tracking and flux regulation of induction motors. The control law is globally defined, requires only measurement of stator variables and rotor speed, and does not rely on cancellation of the systems nonlinearities. Our work extends the result of the paper by Ortega et al.(1993), where the torque tracking problem was solved for a model and the variables are expressed in a frame rotating at an arbitrary angular frequency (dq model). First, we obviate the need to transfer the dq control signals of the paper by Ortega et al., to the physical input variables in the stator frame, hence providing a directly implementable control law. Second, besides the torque tracking objective, we include the practically important rotor flux regulation task. Third, by choosing a more suitable representation of the motor model, we simplify the controller structure and provide a better understanding of its derivation and behavior     

Global adaptive output feedback control of induction motors withuncertain rotor resistance

The authors design a global adaptive output feedback control for a fifth-order model of induction motors, which guarantees asymptotic tracking of smooth speed references on the basis of speed and stator current measurements, for any initial condition and for any unknown constant value of torque load and rotor resistance. The proposed seventh-order nonlinear compensator generates estimates both for the unknown parameters (torque load and rotor resistance) and for the unmeasured state variables (rotor flux); they converge to the corresponding true values under persistency of excitation which actually holds in typical operating conditions. The control algorithm generates references for the magnetizing flux component and for the torque component of stator current which lead to significant simplification for current-fed motors. Simulations show that the proposed controller is suitable for high dynamic performance applications     

Bandwidth vs. gains design of H∞ tracking controllers for current-fed induction motors

This paper describes a systematic procedure for designing speed and rotor flux norm tracking H_∞ controllers with unknown load torque disturbances for current-fed induction motors. A new effective design tool is developed to allow selection of the control gains so as to adjust the disturbances’ rejection capability of the controllers in the face of the bandwidth requirements of the closed-loop system. Application of the proposed design procedure is demonstrated in a case study, and the results of numerical simulations illustrate the satisfactory performance achievable even in presence of rotor resistance uncertainty.     

磁链跟踪PWM感应电机矢量控制系统

PWM调制方式及控制器参数对感应电机矢量控制系统性能有较大影响,使电机在低速时电流脉动和转矩脉动较大。以磁链、转矩闭环的电机矢量控制方法为基础,提出了磁链跟踪控制(Space Vector PWM,SVPWM)的感应电机矢量控制系统仿真模型及低速变控制器参数的控制方法,高度模拟实际系统,并考虑逆变器死区时间的影响,在不同的调速范围下,进行了系统性能分析。在转子磁链定向准确,转子磁链构造准确的前提下,仿真结果表明磁链跟踪控制的矢量控制系统跟踪磁链为准圆形,在低速下,电机电流脉动和转矩脉动都比较小,使系统能够稳定运行,对于解决感应电机高性能调速的低速问题给出了可行的途径。     

Robust speed control of induction motors using position and currentmeasurements

A nonlinear robust output feedback control is designed for a sixth-order model of an induction motor. The control uses only measurement of the rotor position and stator currents. It contains two observers, a second-order observer to estimate the rotor flux from the stator current and a third-order high-gain observer to estimate the rotor speed and acceleration from its position. The control is robust to uncertainties in the rotor and stator resistances, and a bounded time-varying load torque. It guarantees that the speed tracking error can be made arbitrarily small by choice of certain design parameters. Moreover, when the speed reference and load torque are constant, it ensures asymptotic regulation. Simulation results agree well with the analysis     

Adaptive output-feedback control of induction motors

In this paper, we design an adaptive controller for the induction motor which ensures global asymptotic rotor velocity tracking performance and global exponential rotor flux tracking. In addition, the controller compensates for parametric uncertainty associated with the mechanical subsystem and only requires rotor velocity measurements. Experimental results are provided to illustrate the performance of the controller.     

基于转子磁链定向d-q坐标的异步电机控制系统仿真

为了解决异步电机在调速过程中强耦合性的问题,实现定子电流转换成在d-q坐标系下的转子磁链,并保证其同步,通过矢量算法建立磁链电流模型,计算出电动机转子磁链Ψ,,并且在磁链闭环控制下保持不变.根据转差率间接求解方法实现了速度闭环控制,保证了系统在复杂环境下稳定运行.     

Tracking and regulation control of an underactuated surface vesselwith nonintegrable dynamics

A continuous, time-varying tracking controller is designed that globally exponentially forces the position/orientation tracking error of an underactuated surface vessel to a neighborhood about zero that can be made arbitrarily small i.e. global uniformly ultimately boundedness (GUUB). The result is facilitated by fusing a filtered tracking error transformation with a dynamic oscillator design. We also illustrate that the proposed tracking controller yields a GUUB result for the regulation problem     

感应电机转矩跟踪无源控制及自适应观测器设计

针对感应电机高性能转矩跟踪控制和磁链难以直接测量问题,提出了基于无源性的转矩跟踪和自适应磁链观测器控制方案.首先基于感应电机的无源性特性设计了渐近稳定转矩跟踪控制器,重新配置了系统的平衡点,通过注入阻尼提高系统的收敛速度.然后通过将定子电流和转子磁链作为状态变量构建了自适应磁链观测器,简化了观测器结构,根据Lyapunov稳定性理论设计了自适应控制律,实现转子磁链、转速和定子电阻的在线估计.为减小转速估计误差对观测器的影响,给出了观测器增益矩阵的选择方法.仿真结果表明本文所提出的基于自适应观测器的无源控制方案能够有效提高感应电机的动静态性能.     

Stability and stabilization of nonuniform sampling systems

This paper is concerned with nonuniform sampling systems, where the sampling interval is time-varying within a certain known bound. The system is transformed into a time-varying discrete time system, where time-varying parts due to the sampling interval variation are treated as norm bounded uncertainties using robust control techniques. To reduce conservatism arising from modeling time-varying parts as a single uncertainty, the time-varying parts are modeled as N uncertainties. With larger N, a less conservative stability condition is derived at sacrifice of more computation. It is shown through a numerical example that the proposed stability condition is better than existing stability conditions.     

A new nonlinear multivariable control strategy of induction motors

A new real-time control strategy for induction motors is introduced. This paper shows that rotor speed and rotor flux magnitude reference tracking of an induction machine can be originally obtained. The proposed control law is based on two points: an open-loop reference control which allows to obtain perfect tracking since outputs are planned and on a closed-loop strategy based on PI controllers for the stabilization around the desired trajectories. This innovative structure ensures rotor speed and rotor fluxes tracking despite uncertainties on rotor resistance and load torque variations. Simulation and experimental results, including an estimation of the rotor flux norm, are given to illustrate the originality and effectiveness of this control law.     

A rotor speed estimation algorithm in variable speed permanent magnet synchronous generator wind energy conversion system

A rotor speed estimation algorithm in a direct vector controlled permanent magnet synchronous generator wind energy conversion system is proposed. The proposed method is based on a simple equation obtained from the flux model of the machine and contains only stator flux and current. Constant gain recursive least squares estimator is used for implementing the speed estimation algorithm. Rotor position information used for coordinate transformation is computed using the estimated speed. Stator flux information required by the speed estimator is obtained using the stator voltage equation by implementing a programmable low pass filter. The estimated speed is used as the feedback signal for the speed control loop of the vector controlled machine side converter control system whose command speed is obtained from a wind speed sensorless maximum power point tracking controller, thus, we obtain a complete rotor speed and wind speed sensorless permanent magnet synchronous generator wind energy conversion system. Simulation is carried out to validate the performance of the proposed method. Copyright © 2012 John Wiley & Sons, Ltd.     

Robust output feedback learning control for induction motor servo drives

This paper addresses the output feedback tracking control problem for induction motor servo drives with mechanical uncertainties: rotor angle, rotor speed and stator currents are assumed to be available for feedback. A robust adaptive learning control is designed under the assumption that the reference profile for the rotor angle is periodic with known period: it ‘learns’ the periodic disturbance signal by identifying the Fourier coefficients of any truncated approximation; ??₂ and ??_∞ transient performances are guaranteed in the ‘learning phase’. It is shown that, for any motor initial condition belonging to an arbitrary given compact set, by properly setting the control parameters: (i) the rotor position and flux modulus tracking errors exponentially converge to residual sets, which may be arbitrarily reduced by increasing the number of terms in the truncated Fourier series; (ii) when the unknown periodic disturbance can be represented by a finite Fourier series, the rotor position and flux modulus tracking errors exponentially converge to zero. As in field oriented‐control, the control algorithm generates references for the magnetizing flux component and for the torque component of the stator current leading to significant simplifications for current‐fed motors. Copyright © 2008 John Wiley & Sons, Ltd.