A start-up method for a speed sensorless stator-flux-orientedvector-controlled induction motor drive

This paper describes a zero-speed start-up method of a speed sensorless stator-flux-oriented direct vector-controlled induction motor drive with the help of a machine current model that does not use any speed signal. The machine starts smoothly with vector control at finite developed torque and then transitions to the standard direct vector-control mode with the voltage model signals as the speed begins to develop. The direct vector-control mode with voltage model uses programmable cascaded low-pass filters for flux-vector synthesis and enables the drive to operate from zero speed to field-weakening mode. As the drive speed falls to zero, the drive again transitions to start-up mode, so that it can be smoothly started again. The performance of the start-up scheme has been verified on a 100 kW electric vehicle drive     

vector-controlled PWM current-source-inverter-fed induction motor drive with a new stator current control method

In this paper, the control of the pulsewidth-modulated current-source-inverter-fed induction motor drive is discussed. The vector control system of the induction motor is realized in a rotor-flux-oriented reference frame, where only the measured angular rotor speed and the dc-link current are needed for motor control. A new damping method for stator current oscillations is introduced. The method operates in an open-loop manner and is very suitable for microcontroller implementation, since the calculation power demand is low. Also, the stator current phase error caused by the load filter is compensated without measurement of any electrical variable. With the proposed control methods the motor current sensors can be totally eliminated since the stator current measurements are not needed either for protection in the current-source-inverter-fed drives. The proposed control methods are realized using a single-chip Motorola MC68HC916Y1 microcontroller. The experimental tests show excellent performance in both steady-state and transient conditions.     

A high-performance sensorless indirect stator flux orientation control of induction motor drive

A new method for the implementation of a sensorless indirect stator-flux-oriented control (ISFOC) of induction motor drives with stator resistance tuning is proposed in this paper. The proposed method for the estimation of speed and stator resistance is based only on measurement of stator currents. The error of the measured q-axis current from its reference value feeds the proportional plus integral (PI) controller, the output of which is the estimated slip frequency. It is subtracted from the synchronous angular frequency, which is obtained from the output integral plus proportional (IP) rotor speed controller, to have the estimated rotor speed. For current regulation, this paper proposes a conventional PI controller with feedforward compensation terms in the synchronous frame. Owing to its advantages, an IP controller is used for rotor speed regulation. Stator resistance updating is based on the measured and reference d-axis stator current of an induction motor on d-q frame synchronously rotating with the stator flux vector. Experimental results for a 3-kW induction motor are presented and analyzed by using a dSpace system with DS1102 controller board based on the digital signal processor (DSP) TMS320C31. Digital simulation and experimental results are presented to show the improvement in performance of the proposed method.     

Quasi-fuzzy estimation of stator resistance of induction motor

This paper describes a quasi-fuzzy method of online stator-resistance estimation of an induction motor, where the resistance value is derived from stator-winding temperature estimation as a function of stator current and frequency through an approximate dynamic thermal model of the machine. The estimator has been designed and iterated by simulation study and then implemented by a digital signal processor on a 5 hp stator-flux-oriented direct vector-controlled drive. The experimental performance of the estimator has been calibrated extensively both at static and dynamic conditions by a stator-mounted thermistor network-based estimation and gives excellent performance. The stator-winding temperature information can also be used for monitoring, protection, and fault-tolerant control of the machine     

A microcontroller-based sensorless stator flux-orientedasynchronous motor drive for traction applications

A sensorless stator flux-oriented asynchronous motor drive has been realized by using a low-cost single-chip microcontroller. A motor state observer has been implemented, which showed excellent performances, particularly at low-speed operation. Two different experimental realizations have been developed, with rated powers equal to about 1.5 and 30 kW, respectively, and good results have been obtained in both cases. The theoretical approach, main design choices, and most significant experimental results are presented     

PI and fuzzy estimators for tuning the stator resistance in directtorque control of induction machines

Direct torque control (DTC) of induction machines uses the stator resistance of the machine for estimation of the stator flux. Variations of stator resistance due to changes in temperature or frequency make the operation of DTC difficult at low speeds. A method for the estimation of changes in stator resistance during the operation of the machine is presented. The estimation method is implemented using proportional-integral (PI) control and fuzzy logic control schemes. The estimators observe the machine stator current vector to detect the changes in stator resistance. The performance of the two methods are compared using simulation and experimental results. Results obtained have shown improvement in DTC at low speeds     

An improved sensorless vector-control method for an induction motor drive

In the present paper, a new improved sensorless vector-control method for an induction motor drive is presented. The proposed method is based on an improved closed-loop stator-flux estimator, based on the dynamic model of the asynchronous motor, which achieves precise stator-flux estimation over a wide area of operation. This new stator-flux estimator ensures stability of the overall control scheme in a very-wide-speed operation area, as it will be shown in this paper. The rotor-speed-estimation method is based on an observer based on the model reference adaptive systems (MRAS) theory. The control scheme is based on a stator-flux-oriented direct vector-control method, where both flux and speed controllers are optimal tuned. In addition, implementation of the proposed method is based on a simplified algorithm capable of running in a low-cost microcontroller, which is discussed in detail. Also, the motor-drive system, including the stator-flux estimator, the speed estimator, and the control logic are simulated and some characteristic simulation results are presented. These results reveal that the proposed method is able to obtain precise flux and speed control over a wide operation area, including very low operating frequencies.     

A novel CSI-fed induction motor drive

Current source inverter (CSI) fed drives are employed in high power applications. The conventional CSI drives suffer from drawbacks such as harmonic resonance, unstable operation at low speed ranges, and torque pulsation. This paper presents a novel CSI drive which overcomes all these drawbacks and results in sinusoidal motor voltage and current even with CSI switching at fundamental frequency. The proposed CSI drive uses a three-level inverter as an active filter across motor terminals replacing the bulky ac capacitors used in the conventional drive. A sensorless vector controlled CSI drive based on proposed configuration is developed. The simulation and experimental results are presented. Experimental results show that the proposed drive has stable operation even at low speeds. Comparative results show that the proposed CSI drive has improved torque ripple compared to the conventional configuration.     

A new method for impedance control of induction motor speed

A novel induction machine with continuous speed control is found possible. This motor may be regarded as an inverted version of a Schrage motor in construction in that the tertiary winding is placed along with the secondary (on the stator) rather than with the primary (on the rotor). Hence a static commutator connected to the tertiary winding with the brushes placed over it at the appropriate places helped in injecting an EMF (of slip frequency) at various angles with respect to the secondary EMF induced by brush rotation. This has resulted in speed control of the induction motor. The performance characteristics of the new motor resemble those of a series-regulated induction machine in contrast to the shunt characteristics of a Schrage motor.     

一种用于优化感应电机电流环的新方法

在感应电机转差频率矢量控制系统中,电流环的性能对整个系统响应的快速性和准确性有着重要影响,而电流环在两轴直流旋转(d-q)坐标系下存在交叉耦合,并且随着电源角频率的增大耦合成分增大,导致电流环特性变差。为此提出一种新的优化方法,即在传统PI电流控制器的基础上,设定合理的模糊规则并选取合适的PI参数kI,kP,对电流系统进行优化。在Matlab的Simulink模块下对电流系统建模仿真,仿真结果表明,设计的控制方法有效地降低了两轴之间的相互扰动,提高了电流控制系统的动态特性,且新方法简单易行,有较强的鲁棒性。     

A direct field-oriented controller for induction motor drives usingtapped stator windings

The implementation of a direct method of field orientation that requires little knowledge of machine parameters and uses only readily measurable quantities is discussed. The system uses tapped stator windings to measure the air-gap flux. The signals from the tapped windings are also used in a flux-regulation loop. A speed controller is implemented using the ripples created in the tapped windings by the motion of the rotor slots through the flux for speed information     

A discrete adaptive field-oriented induction motor drive

A discrete model reference adaptive controller (MRAC) is designed and implemented. This MRAC makes the performance of the field-oriented induction motor drives insensitive to parameter changes. Only the information of the reference model and the plant output are required. Hence, the proposed controller is easy to implement practically. For designing the proposed adaptive controller, the dynamic model of the drive system is estimated from the sampled input-output data using the stochastic modeling technique. The theoretical basis of the adaptive control is derived and simulation is made. The hardware of the drive system and the microprocessor-based adaptive controller are discussed. Some experimental results are given to demonstrate the effectiveness of the proposed controller     

Averaging analysis approach for stability analysis of speed-sensorless induction motor drives with stator resistance estimation

In this paper, the stability property of speed-sensorless induction motor drives with stator resistance estimation is analyzed using the averaging analysis technique. Explicit stability conditions are then derived to clarify analytically when the instability may occur and how the regressor vectors used in the estimation and the integral adaptation gains should be designed to assure stability. The derived stability conditions also reveal that the coupling between the speed and the stator resistance estimation loops is the main cause of instability and that stabilization of each individual estimation loop is necessary but insufficient to guarantee stability. Instead of the conventional regressor vectors that are shown to make the estimation unstable in some regenerative regions, two new regressor vectors are introduced to achieve stability for the whole operating conditions. Moreover, investigation of the persistently exciting (PE) conditions points out theoretically the loss of identifiability of the rotor speed and the stator resistance at no loads and at zero frequency operations. Validity of all the analytical results is verified by simulation and experiment.     

Recurrent-neural-network-based implementation of a programmablecascaded low-pass filter used in stator flux synthesis ofvector-controlled induction motor drive

The concept of programmable cascaded low-pass filter for stator flux vector synthesis by ideal integration of stator voltages at any frequency was introduced by Bose and Patel. A new form of implementation of this filter is proposed that uses a combination of recurrent neural network trained by Kalman filter and a polynomial neural network. The proposed structure is simple, permits faster implementation by digital signal processor, and gives improved performance     

A novel DC chopper drive for a single-phase induction motor

The paper presents a new drive for single-phase induction motors. This drive employs a DC chopper circuit with a diode bridge rectifier connected with the stator in a nonconventional fashion. The speed of the single-phase induction motor is controlled by controlling the chopping frequency of the chopper switch. The attractive feature of the drive is that it effects both frequency and phase-angle control simultaneously. The drive performance has received both theoretical and experimental investigation     

Online estimation of the stator resistance and leakage inductance of a four-phase induction machine drive

This paper proposes a technique to determine online the stator resistance and the stator leakage inductance of a four-phase induction machine in a four-phase drive system. These parameters are obtained by solving a least squares minimization problem. The technique is conceived to be used online with the drive strategy without disturbing the machine electromagnetic torque. Experimental results are used to demonstrate the feasibility of the proposed technique.     

Spectral analysis of a new six-phase pole-changing induction motor drive for electric vehicles

In this paper, a new six-phase pole-changing induction motor drive is proposed to extend the constant-power operating range for electric vehicle application. The double Fourier series is newly employed to analyze the spectra of the motor phase voltage and current. Consequently, the harmonic expression of the inverter DC-link current can be derived. In order to reduce the DC-link harmonics, a new sinusoidal pulsewidth-modulation strategy is developed for the proposed six-phase inverter. Experimental results, particularly the spectra of the phase current and the DC-link current, are given to verify the theoretical analysis.     

Efficiency enhancement for indirect vector-controlled induction motor drive

In this paper, efficiency enhancement algorithms are developed and implemented on an indirect vector-controlled three-phase induction motor (IM) drive, and its performance under different operating conditions is analysed. The controllable electrical losses in the IM are minimised through the optimal control of direct axis (d-axis) stator current, and improvement in motor efficiency is achieved by weakening the rotor flux. The optimal d-axis stator current is also estimated using particle swarm optimisation (PSO) to validate the results obtained through analytical control method. The developed algorithms are tested under various operating conditions and the dynamic performance of the IM drive is analysed. The effectiveness of analytical and PSO-based efficiency optimisation control over conventional constant flux control, especially during light load at rated speed operation, is summarised. The effectiveness of the developed algorithm is validated experimentally through development of laboratory prototype set-up. The effect of parametric variation on efficiency, stator current, torque and speed of IM drive is studied through sensitivity analysis. The effect of variation in stator and rotor resistance due to change in operating temperature of the IM is also analysed and the robustness of the developed algorithm against parametric variations is demonstrated through simulation and experimental studies.     

Nonlinear control for linear induction motor servo drive

This paper describes a newly designed nonlinear control strategy to control a linear induction motor servo drive for periodic motion. Based on the concept of the nonlinear state feedback theory and optimal technique, a nonlinear control strategy, which is composed of an adaptive optimal control system and a sliding-mode flux observation system, is developed to improve the drawbacks in previous works concerned with complicated intelligent control. The control and estimation methodologies are derived in the sense of Lyapunov theorem so that the stability of the control system can be guaranteed. The sliding-mode flux observation system is implemented using a digital signal processor with a high sampling rate to make it possible to achieve good dynamics. Computer simulations and experimental results have been conducted to validate the effectiveness of the proposed control scheme under the occurrence of possible uncertainties and different reference trajectories. The merits of the proposed control system are indicated in comparison with a traditional optimal control system.     

A novel space-vector current regulation scheme for afield-oriented-controlled induction motor drive

The system performance of an AC variable-speed drive directly depends on the current regulation. In this paper, a novel space-vector current regulation scheme for a field-oriented controller (FOC) is developed. Motor currents are regulated by generating appropriate inverter output voltage vectors via software-implemented comparators and a switching table. A switching table based on the angular coordinate enables the inverter to generate optimal voltage vectors. By introducing an additional triangular carrier signal to the output of original hysteresis comparators, a user-selectable high and fixed switching frequency can be obtained, further improving the driver performance. Experiments are made to verify the effectiveness and correctness of this proposed method. According to the experimental results, both simple hardware design and good current response can be attained