Direct torque control of sensorless induction motor drives: a sliding-mode approach

Direct torque control (DTC) is known to produce fast response and robust control in ac adjustable-speed drives. However, in the steady-state operation, notable torque, flux, and current pulsations occur. A new, direct torque and flux control strategy based on variable-structure control and space-vector pulsewidth modulation is proposed for induction motor sensorless drives. The DTC transient merits and robustness are preserved and the steady-state behavior is improved by reducing the torque and flux pulsations. A sliding-mode observer using a dual reference frame motor model is introduced and tested. Simulations and comparative experimental results with the proposed control scheme, versus classic DTC, are presented. Very-low-speed sensorless operation (3 r/min) is demonstrated.     

A novel position sensorless control scheme for doubly fedreluctance motor drives

A novel position sensorless control algorithm for the newly developed doubly fed reluctance motor (DFRM) drives is presented. The control makes use of the 60 Hz terminal variables, which are easy to acquire and process, for estimation and control of the torque angle of the machine, while the speed of the system is given in an open-loop mode. The control is robust and suitable for variable-speed pump-type application. With this control, the required VA ratings of the PWM converter are only 50% of that of the DFRM motor, and the motor can be started with full load torque. This control scheme has been successfully implemented on a 2-HP DFRM drive     

MRAS-based speed sensorless control scheme with stator resistance identification function for vector-controlled induction motor drives

This paper describes a new scheme for the speed sensorless control of the vector-controlled induction motor drive. Based on the model reference adaptive system (MRAS) theory, the rotor speed of the induction machine is estimated with a full-order adaptive observer. The estimated speed then is used as the signal for the vector control and the speed control. To accurately estimate the speed at the lower speed range, the value of the stator resistance also is identified at the same time and then is used to modify the resistance value set in the observer. The resulting system is verified to be hyperstable with Popov's criterion. As a result, this drive can operate stably in a wide range of speed even at zero speed. Also, it is shown theoretically that neither speed nor resistance of the rotor can be identified at the same time because these two parameters are dependent on each other. Simulation results and experiments also show that the scheme is effective.     

Very low speed and zero speed estimations of sensorless induction motor drives

Recently, speed sensorless control of induction motor drives received great attention to avoid the different problems associated with direct speed sensors. However, low speed operation with robustness against parameter variations remains an area of research for sensorless systems. Stator resistance is of utmost importance for good operation of speed sensorless systems in low speed region. In this paper, a sliding mode current observer for an induction motor is presented. An estimation algorithm based on this observer in conjunction with Popov's hyper-stability theory is proposed to calculate the speed and stator resistance independently. The proposed speed observer with parallel stator resistance identification is first verified by simulation. Experimental results are included as well as to demonstrate the good performance of the proposed observer and estimation algorithms at very low and zero speeds.     

异步电动机无速度传感器的矢量控制

对交流异步电动机无速度传感器的矢量控制进行了综述 ,分析了几种控制方案的原理 ,指出了它们各自的优点与不足 ,并就今后的研究发展方向提出了一些设想     

一种异步电机无速度传感器间接磁场定向控制策略

针对无速度传感器异步电机,提出了一种新的滑模磁通和速度观测方法。实际电流和观测电流之间的误差收敛到零,保证磁通观测器的精确性。根据估计的定子电流和转子磁链来估计转子的转速和转子时间常数。估计的转子时间常数用于滑模计算和观测器结构中,估计的转速用来作为转速调节的反馈。仿真结果证明所提出的速度估算方法有效以及所提出的观测器结构具有鲁棒性。     

Sensorless control of inverter-fed induction motor drives

Sensorless control is considered to be a lower cost alternative than the position or speed encoder-based control of induction motors. Two popular sensorless control methods, namely, the model reference adaptive system (MRAS) and the Luenberger observer (LO) methods are compared for speed and torque control characteristics. They are also compared against the well-known vector control principle. For the drive system simulated, the torque and speed obtained from sensorless control are almost identical to those obtained from the vector control method. However, the torque ripple for the sensorless methods is observed to be higher than vector control-based method. The MRAS method introduces higher torque ripple when compared to the Luenberger observer. In addition, speed estimation methods employed in sensorless control are more sensitive to motor parameter variations.     

一种新的异步电动机调速系统的混合控制方法

矢量控制(FOC)和直接转矩控制(DTC)是目前高性能异步电动机调速系统中的两种主要控制方法.研究和工程实践表明,这两种方法各有优缺点,国内外很多学者也提出了很多方案,试图改进和完善这两种控制方法.本文从全新的思路出发,尝试把这两种方法结合到一个控制系统中,取长补短,形成一种新的混合控制方法.该方法使用户可以根据实际运行的不同需要,在线灵活地切换到合适的控制方法(FOC或DTC),以提高控制性能.为了实现两种控制方法之间的平滑切换,本文把传统的PI控制器改造成可重置PI控制器.仿真和实验结果表明,这种可重置PI控制器可以有效减少FOC和DTC切换时造成的系统波动,同时能保持原有控制系统的性能,提高了本文提出的混合控制方法的实用价值.     

Very-low-speed variable-structure control of sensorless induction machine drives without signal injection

A sensorless induction machine drive is presented, in which the principles of variable-structure control and direct torque control (DTC) are combined to ensure high-performance operation in the steady state and under transient conditions. The drive employs a new torque and flux controller, the "linear and variable-structure control", which realizes accurate and robust control in a wide speed range. Conventional DTC transient merits are preserved, while the steady-state behavior is significantly improved. The full-order state observer is a sliding-mode one, which does not require the rotor speed adaptation and provides accurate state estimation in the entire speed range. The proposed scheme is a complete variable-structure solution that allows persistent sensorless operation of the drive at very low speeds, including zero and 3 r/min, with full load. Simulations and extensive experimental results confirm the robustness, accuracy, quickness, and low-chattering operation of the drive.     

感应电机混合滑模变结构控制方法

针对传统直接转矩控制所固有的稳态运行时转矩、磁链、电流脉动大的问题,提出了一种利用转矩误差与磁链误差、通过滑模变结构控制方法实现对转矩与磁链进行控制的直接转矩控制方案.分别以转矩误差与磁链误差作为状态变量设计了时变积分型滑模平面,保证了趋近过程的系统状态保持在滑模面附近,减小了趋近距离.而对于滑模变结构控制本身的抖振问题,采用了一种通过滞环比较器自适应地实现了滑模变结构控制与传统PI控制的平滑过渡的混合滑模变结构控制方法.实验结果验证了该控制方法的有效性和可行性.     

A robust sliding mode flux and speed observer for speed sensorless control of an indirect field oriented induction motor drives

In this paper a new sliding mode flux and speed observer is proposed for indirect field oriented induction motor drive system. The error between the actual and observed currents converges to zero, which guarantees the accuracy of the flux observer. The rotor speed and the rotor time constant are estimated based on the estimated stator currents and rotor flux. The estimated rotor time constant is used in slip calculation and observer structures and the estimated speed is used as feedback to the speed regulation. Computer simulation and experimental results of the speed control verify the validity of the proposed speed estimation algorithm. The experimental results show the robustness and performance of the proposed observer structure. Experimental results have been realized without load, with load and with external disturbances.     

Speed sensorless field-oriented control of induction motor withrotor resistance adaptation

Several field-oriented induction motor drive methods without rotational transducers have been proposed. These methods have a disadvantage that the rotor resistance variation causes an estimation error of the motor speed. Therefore, simultaneous estimation of the motor speed and the rotor resistance is required. This paper presents a method of estimating simultaneously the motor speed and the rotor resistance of an induction motor by superimposing AC components on the field current command. The validity of the proposed method is verified by simulation and experimentation     

无速度传感器异步电机矢量控制系统的改进研究与仿真

以异步电机矢量控制的基本方程式为基础,构建了一个无速度传感器矢量控制系统。系统采用了改进积分型转子磁链估算模型。根据模型参考自适应方法的原理,提出一种改进的速度估算法。并利用MATLAB/SIMULINK进行了仿真,仿真结果验证了采用的速度估算方法是正确的。     

Speed sensorless vector control of induction motor using extendedKalman filter

A vector control of an induction motor by an estimated speed using an extended Kalman filter is proposed. With this method, the states are composed of stator current and rotor flux. The rotor speed is regarded as a parameter, and the composite states consist of the original states and the rotor speed. The extended Kalman filter is employed to identify the speed of an induction motor and rotor flux based on the measured quantities such as stator currents and DC link voltage. The estimated speed is used for vector control and overall speed control. Since the current control is performed at a synchronous rotating reference frame, the estimated speed information is also used for the reference frame transformation of the current controller. Computer simulations and experiments of the speed control have been carried out to test the usefulness of the speed estimation algorithm. The experimental results show that the performance of the speed estimation is very good     

Analysis of rotor slotting saliency in induction motor sensorless control

This paper deals with induction machines study by Finite Element Analysis (FEA) for position sensorless control drives based on rotating voltage carrier injection. It focuses the analysis of the rotor slotting saliency, under the variations of: (1) supply of the machine (both the high frequency rotating voltage carrier and the fundamental frequency supply), (2) reference flux of the drive, (3) load torque, and (4) rotor geometry design. The relative spatial harmonic of the stator inductance space-vector responsible for the rotor slotting effect has been chosen as an index for evaluating the response to the high frequency carrier. A methodology for retrieving the stator inductance space-vector from a FEA is proposed as well. Results of the variation of the rotor slotting spatial harmonic of the stator inductance with the carrier frequency, the rotor flux linkage, the load torque and the rotor geometry are presented.     

感应电机无速度传感器控制自适应速度观测器

理论与实践证明自适应速度观测器是实现高性能的感应电动机无速度传感器控制系统的有效方法之一。由于该系统的非线性性质,在观测器设计以及系统应用中还有许多有待解决的问题。针对此类问题,从理论联系实际的角度,分析现有的电机磁链、速度观测器理论的要点及其成果,如建模的条件、自适应速度估计算法及其物理性质、系统稳定性分析、线性化方法、以及观测器参数的辨识等。同时,给出了实验结果、指出了这些内容中尚存的相关问题。     

An adaptive sliding-mode observer for induction motor sensorless speed control

An adaptive sliding-mode flux observer is proposed for sensorless speed control of induction motors in this paper. Two sliding-mode current observers are used in the method to make flux and speed estimation robust to parameter variations. The adaptive speed estimation is derived from the stability theory based on the current and flux observers. The system is first simulated by MATLAB and tested by hardware-in-the-loop. Then, it is implemented based on a TMS320F2812, a 32-bit fixed-point digital signal processor. Simulation and experimental results are presented to verify the principles and demonstrate the practicality of the approach.     

MRAS-based sensorless control of a vector controlled five-phase induction motor drive

Multi-phase ac motor drives are nowadays considered for various applications, due to numerous advantages that they offer when compared to their three-phase counterparts. In principle, control methods for multi-phase machines are the same as for three-phase machines. Variable speed induction motor drives without mechanical speed sensors at the motor shaft have the attractions of low cost and high reliability. To replace the sensor, information of the rotor speed is extracted from measured stator currents and voltages at motor terminals. Vector controlled drives require estimating the magnitude and spatial orientation of the fundamental magnetic flux waves in the stator or in the rotor. Open-loop estimators and closed-loop observers are used for this purpose. They differ with respect to accuracy, robustness, and sensitivity against model parameter variations. This paper analyses operation of an open-loop and model reference adaptive system (MRAS)-based sensorless control of vector controlled five-phase induction machine with current control in the stationary reference frame. The MRAS-based sensorless operation of a three-phase induction machine is well established and the same principle is extended in this paper for an IRFOC five-phase induction machine. Performance, obtainable with hysteresis current control, is illustrated for a number of operating conditions on the basis of simulation results. Full decoupling of rotor flux control and torque control is realised. Dynamics, achievable with a five-phase vector controlled induction machine, are shown to be essentially identical to those obtainable with a three-phase induction machine. Experimental verification is also provided.     

Implementation of a closed loop sliding mode observer for speed sensorless control of an indirect field oriented induction motor drives

A new sliding mode flux and speed observer is proposed for indirect field oriented induction motor drive system. The error between the actual and observed currents converges to zero, which guarantees the accuracy of the flux observer. The rotor speed and the rotor time constant are estimated based on the estimated stator currents and rotor flux. The estimated rotor time constant is used in slip calculation and observer structures. The estimated speed is used as feedback to the speed regulation. Simulation and experimental results of the speed control verify the validity of the proposed speed estimation algorithm.     

一种用于异步电机无速度传感器控制的自适应滑模观测器

针对异步电机无速度传感器中存在的对参数变化鲁棒性差的问题,研究了一种基于自适应滑模观测器的异步电机无速度传感器的矢量控制方案。自适应滑模观测器根据电机静止坐标系下的数学模型构造了转子磁链观测器,定子电流观测值与实际值的误差构成观测器的滑模面,在滑模运动下该观测器的观测值最终趋近于实际值,从而实现转子磁链的估计。电机转速由自适应方法估算得到,滑模观测器的稳定性可由李雅普诺夫稳定性证明。与其他方案相比,该方法的优点在于实现简单,对参数变化具有鲁棒性。仿真和实验对控制方案的正确性和可行性给出了验证,该观测器可以实现对转子磁链和转速的观测,且在负载扰动和给定转速变化的情况下该滑模观测器具有鲁棒性。