Rotor Flux Amplitude Research Articles

COMBINED FIRST AND SECOND-ORDER SLIDING MODE CONTROL OF INDUCTION MOTOR

This paper uses hybrid sliding mode control to solve an output feedback tracking problem for the induction motor (IM). The main idea of this approach lies in the design of a law that ensures a smooth transition between two sliding regimes based on the choice of two sliding surfaces, one being linked to the other. The control is a combination of first and second-order sliding modes. The proposed approach controls the speed and rotor flux amplitude of the induction motor and guarantees the stability of the decoupled speed and rotor flux by using a Lyapunov method. The hybrid sliding mode algorithm provides robustness despite external disturbances and parameter variations. The controller has been implemented on an experimental setup, and results are presented to confirm the proposed method's effectiveness, robustness, and good performance.

Research and Analysis of the Characteristics of the Brushless Doubly-Fed Machine with High-Performance Decoupling Control

The paper presents the state-space (SS) model of the brushless double-fed machine (BDFM) by taking the negative conjugate (NC) transformation of the power machine’s correlation variable when the current source of the control machine is supplied in the m-t reference frame. Based on this, the testing method of machine parameters is given, and the SS model described by five parameters is obtained. The derivation process and realization method of the slip-frequency vector feedback linearization control (SFV-FLC) strategy are given. Then, researching the SS equation in the m-t reference frame by the control machine rotor field-oriented, the relationship between the maximum and minimum output torque and the control machine rotor flux amplitude and slip velocity, the machine parameters are given considering power supply constraints. Finally, the validity of the theoretical analysis is verified by simulation and experiment, and the feasibility of the decoupling control method are also demonstrated.

Offline method for experimental identification of load‐dependentsaturation of induction motor taking into account variation of inverse rotortime constant

Accurate knowledge of induction machine parameters has a direct impact on the overall performance of field-oriented control strategies. In the case of rotor flux oriented control, parameter mismatch causes a discrepancy in the estimated rotor flux position and amplitude. Magnetising inductance is one of the parameters whose detuning has a direct impact on the setpoints of the control loops and estimation of hardly or non-measurable quantities. Conventional iron saturation, which can be obtained by a standard no-load test, is not the only type of saturation occurring in the machine. Depending on the rotor design, the magnetising inductance and the rotor leakage inductance may also strongly saturate as a function of load and, thus, rotor current. Based on the authors’ previous work, a new, improved experimental method for identifying the load-dependent saturation of induction motor, which takes into account variation of the inverse rotor time constant, is proposed. Experimental results conducted on 12 kW motor show improved static and dynamic behaviour of the drive compared to the constant parameter model.

The Novel Rotor Flux Estimation Scheme Based on the Induction Motor Mathematical Model Including Rotor Deep-Bar Effect

During torque transients, rotor electromagnetic parameters of an induction motor (IM) vary due to the rotor deep-bar effect. The accurate representation of rotor electromagnetic parameter variability by an adopted IM mathematical model is crucial for a precise estimation of the rotor flux space vector. An imprecise estimation of the rotor flux phase angle leads to incorrect decoupling of electromagnetic torque control and rotor flux amplitude regulation which in turn, causes deterioration in field-oriented control of IM drives. Variability of rotor electromagnetic parameters resulting from the rotor deep-bar effect can be modeled by the IM mathematical model with rotor multi-loop representation. This paper presents a study leading to define the unique rotor flux space vector on the basis of the IM mathematical model with rotor two-terminal network representation. The novel rotor flux estimation scheme was validated with the laboratory test bench employing the IM of type Sg 132S-4 with two variants of rotor construction: a squirrel-cage rotor and a solid rotor manufactured from magnetic material S235JR. The accuracy verification of the rotor flux estimation was performed in a slip frequency range corresponding to the IM load adjustment range up to 1.30 of the stator rated current. This study proved the correct operation of the developed rotor flux estimation scheme and its robustness against electromagnetic parameter variability resulting from the rotor deep-bar effect in the considered slip frequency range.

Predictive Torque and Rotor Flux Control of a DFIG-DC System for Torque Ripple Compensation and Loss Minimization

The severe torque ripple normally occurring in the doubly fed induction generator dc (DFIG-dc) system can cause premature failure of mechanical components and shorten the life of the drive train. This paper addresses the torque ripple issue by proposing a predictive direct torque control strategy, which delivers at the same time torque ripple suppression and minimization of losses. The existing control algorithms for torque ripple mitigation are mostly based on resonant controllers and repetitive control forcing the compensation signal either through the current chain or directly into the rotor voltage commands. All these techniques lead to structures with multiple controllers whose tuning is not straightforward. Furthermore, they are very sensitive to the operating frequency, making optimized operation with variable frequency highly challenging. Conversely, the proposed algorithm predicts directly the best rotor voltage space vector to minimize torque ripple and track a prescribed rotor flux amplitude to minimize losses, with no current control chain. As confirmed by simulations and experiments, the strategy allows large stator frequency variations as required by the optimal flux command for minimum losses, whilst ensuring effective torque ripple compensation.

Torque and state estimation for real‐time implementation of multivariable control in sensorless induction motor drives

This study presents a strategy for estimating the states and the load torque to implement a feedback linearisation controller for induction motor drives. The multivariable control is carried out using input–output linearisation feedback law in order to track profiles of the rotational speed and the rotor flux amplitude. The unknown load torque is compensated by an estimator based on the speed error. The state estimation requires only the measurements of the stator voltages–currents. The estimation method is not invasive as no mechanical sensors are needed. Experimental platform equipped with sensors at the load side, for measuring the speed and the torque of the motor driven by the Opal-RT real-time system, was implemented to verify the accuracy of the proposed estimation method to implement the multivariable control.

Speed control of sensorless induction generator by artificial neural network in wind energy conversion system

This study presents a new strategy for estimating the states (rotor flux and speed) and the load torque to implement a multivariable controller for a sensorless three-phase squirrel-cage induction machine in wind energy conversion systems. The multivariable control is carried out using input–output feedback law and its objective is to track profiles of the rotational speed and the rotor flux amplitude. The state estimation considerably improves the performance of rotor flux based model reference adaptive system in the variable speed region of operation. The technique uses Kalman filter as a rotor flux observer and an artificial neural network adaption mechanism to estimate the rotor speed. The state estimation requires only the measurements of the stator voltages and currents. The estimation method, for both states and torque, is not invasive as no mechanical sensors are needed. The wind energy conversion system and the proposed control-estimation techniques are simulated in Matlab/Simulink software platform and tested using the OPAL-RT real-time simulator (OP5600) to verify the accuracy of the proposed control-estimation method.

The influence of mistuned motor parameters on vector control performance and on line slip frequency correction strategy for induction machine operated under one‐pulse PWM mode

In high‐power, high‐speed traction drive systems, the traction motor usually operates under one‐pulse PWM (pulse width modulation) mode (square wave) during high‐speed operation. The constant output voltage in this condition makes the traditional vector control inoperative anymore. In this paper, a modified vector control strategy using open‐loop current control instead of closed‐loop current control is proposed. The modified control strategy is specially designed for an induction motor operating under one‐pulse PWM mode. As the field orientation is greatly affected by the deviation in the parameters, the influence of mistuned rotor time constant and mutual inductance (which are regarded as the most important parameters for field orientation) on the performance of modified vector control is studied comprehensively, including the influence on estimated angle and amplitude of rotor flux, d/q‐axis voltage, and output torque. Subsequently, based on the comparison between the different methods, a new slip frequency correction strategy is proposed to maintain proper field orientation for the modified vector control. The new correction strategy is based on the q‐axis current component error. It is independent of the motor parameters and can be easily realized through minor calculations. The simulation and experimental results show that the proposed slip frequency correction strategy can not only eliminate rotor flux angle error in steady state but also effect rapid torque response during the transient process under one‐pulse PWM mode. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Application of Speed, Rotor Flux, Electromagnetic, Load Torque Observers and Diagnostic System in a Vector-Controlled High-Power Traction Motor Drive

For a field-oriented high-power induction motor drive, the observers are used to calculate speed, rotor flux phase and amplitude, electromagnetic and load torque observation and control and for diagnostic purposes. The observers of speed, rotor flux phase and amplitude are designed based on the model reference adaptive system, which has simple structure but extreme precision. A load torque observer is planned by employing the speed and electromagnetic observers, which well estimates the actual load torque. A diagnostic system is proposed to send an alarm to the maintenance center during the fault occurrence by independently comparing the observed and the actual or the previously recorded values of the load torque and speed. In addition, the drive control can be switched automatically to sensorless mode during the system operation, as a speed sensor fault occurs. Generally, the application of the observers and diagnostic system increases the drive reliability and safety. The performances of the drive, observers and diagnostic system are verified through simulations accomplished on a 150-kW induction motor drive.

DIRECT TORQUE CONTROL FOR DOUBLY FED INDUCTION MACHINE-BASED WIND TURBINES UNDER VOLTAGES DIPS AND WITHOUT CROWBAR PROTECTION

This letter proposes a rotor flux amplitude reference generation strategy for doubly fed induction machine based wind turbines. It is specially designed to address perturbations, such as voltage dips, keeping controlled the torque of the wind turbine, and considerably reducing the stator and rotor over currents during faults. In addition, a direct torque control strategy that provides fast dynamic response accompanies the overall control of the wind turbine. Despite the fact that the proposed control does not totally eliminate the necessity of the typical crowbar protection for this kind of turbines, it eliminates the activation of this protection during low voltage dips.

Passivity-Based Parameter Estimation and Position Control of Induction Motors via Composite Adaptation

This paper proposes the parameters estimation and position control of an induction motor drive by using the composite adaptation scheme. First, in the rotor reference frame, the input-output linearization theory was employed to decouple the mechanical rotor position and the rotor flux amplitude at the transient state. An open-loop current model rotor flux observer was utilized for estimating the flux, and then the adaptive laws for estimating the rotor resistance, moment of inertia, viscous friction coefficient, and load torque. The passive properties of the flux observer, rotor resistance estimator, and composite adaptive position controller were analyzed based on the passivity theorem. According to the properties, the overall position control system was proved to be globally stable without using Lyapunov-type arguments. Experimental results are finally provided to show that the proposed method is robust to variations of the motor mechanical parameters, rotor resistance, and load torque disturbances. Moreover, good position tracking response and characteristics on parameter estimation can be achieved.

Direct Torque Control Strategy for Doubly Fed Induction Machine under Low Voltage Dips

This paper proposes a control strategy of generating a rotor flux amplitude reference for Doubly Fed Induction Machine (DFIM) based wind turbines. In addition to that a Direct Torque Control (DTC) strategy that provides fast dynamic response accompanies the overall control of the wind turbine. It is specially designed to address perturbations, such as voltage dips, keeping controlled the torque of the wind turbine, considerably reducing the stator and rotor over currents during faults. Despite the fact that the proposed control does not totally eliminate the necessity of the typical crowbar protection for this kind of turbines, it eliminates the activation of this protection during low depth voltage dips. DOI: http://dx.doi.org/10.11591/ijpeds.v2i4.710

Cascaded Nonlinear Adaptive Predictive Control based Adaptive Flux Observer of Induction Motor

his paper present a new advanced control algorithm based on continuous minimization of predicted tracking errors, to achieve torque, rotor speed and rotor flux amplitude tracking objectives. This algorithm called a new Adaptive Nonlinear Predictive Control to induction motor drive uses a combination of the adaptive observer for rotor flux and Cascaded Nonlinear Predictive Control technique. The variables to be controlled are the rotor speed and the rotor flux norm, required to implement the predictive control algorithm is estimated by flux observer. The parameters identified adaptively are stator and rotor resistance which vary with motor temperature using the adaptive rotor flux observer. A stability of the proposed adaptive flux observer will be proved by the Lyapunov's theorem. Simulations are carried out in order to show the effectiveness of the drive and the robustness to parameters variations.

Controlling of Rotor Flux for Doubly Fed Induction MachineBased Wind Turbines under Voltages Dips and Without Crowbar Protection

This paper proposes a rotor flux amplitude reference generation strategy for doubly fed induction machine based wind turbines. It is designed to address perturbations, such as voltage dips, keeping controlled the torque of the wind turbine, and considerably reducing the stator and rotor over currents during faults. In addition, a direct torque control strategy that provides fast dynamic response accompanies the overall control of the wind turbine. Despite the fact that the proposed control does not totally eliminate the necessity of the typical crowbar protection for this kind of turbines, it eliminates the activation of this protection during low voltage dips.

Direct Torque Control for Doubly Fed Induction Machine-Based Wind Turbines Under Voltage Dips and Without Crowbar Protection

This letter proposes a rotor flux amplitude reference generation strategy for doubly fed induction machine based wind turbines. It is specially designed to address perturbations, such as voltage dips, keeping controlled the torque of the wind turbine, and considerably reducing the stator and rotor overcurrents during faults. In addition, a direct torque control strategy that provides fast dynamic response accompanies the overall control of the wind turbine. Despite the fact that the proposed control does not totally eliminate the necessity of the typical crowbar protection for this kind of turbines, it eliminates the activation of this protection during low depth voltage dips.

Adaptive backstepping control of a speed-sensorless induction motor under time-varying load torque and rotor resistance uncertainty

A new global adaptive backstepping controller is designed for induction motor speed control based on measurements of stator current and estimation of rotor speed. The designed partial state feedback controller is singularity free and guarantees asymptotic tracking of smooth reference trajectories for the speed of the motor under time varying load torque and rotor resistance uncertainty. The new control algorithm generates estimates for unknown time varying load torque, rotor resistance and rotor speed, which asymptotically tracks and converges to their true values. The rotor flux modulus asymptotically tracks a desired reference signal which allows the motor to operate within its specifications. As in the field-oriented control scheme; the control algorithm generates references for the magnetising flux component and for the speed component of the stator current. The control strategy yields decoupled rotor speed and rotor flux amplitude tracking control goals which allow the selection of an appropriate flu...

Adaptive Parameter Estimation and Position Control of Induction Motors Based on Passivity Theorem

This paper presents the passivity-based rotor resistance and mechanical paramters estimation, and the position control for induction motors. Firstly, the input-output linearization theory is employed to decouple the rotor flux amplitude and the rotor position at the transient state. An open-loop current model flux observer then estimates the rotor flux. Furthermore, we adopted the gradient algorithm to design adaptive laws to estimate the rotor resistance, moment of inertia, viscous coefficient, and load torque. The passive properties of the feedback connection of the rotor flux observer to the rotor resistance estimator, and the position controller are analyzed by the passivity theorem. According to the properties, the overall control system is proved to be globally stable without using Lyapunov-type arguments. Finally, experimental results are provided to show that the proposed method is robust to variations of the mechanical parameters and load torque disturbances. Moreover, good position tracking response and parameters estimating characteristic can be obtained.

Adaptive backstepping control of an induction motor under time-varying load torque and rotor resistance uncertainty

A new global adaptive controller is designed for induction motor speed control based on measurements of speed and stator current. The designed partial state feedback controller is singularity free, and guarantees asymptotic tracking of smooth reference trajectories for the speed of the motor under time-varying load torque and rotor resistance uncertainty, for any initial condition. The new control algorithm generates estimates for unknown time-varying load torque, rotor resistance and unmeasured state variables (rotor fluxes) which asymptotically tracks and converges to their true values. The rotor flux modulus asymptotically tracks a desired reference signal which allows the motor to operate within its specifications. The control strategy yields decoupled rotor speed and rotor flux amplitude tracking control goals which allows the selection of an appropriate flux modulus for the rotor to maximise efficiency.

A Nonlinear State Feedback Controller for Induction Motors

In this article, a novel approach to nonlinear control of induction motors is presented. The proposed approach is used to design controllers for the rotor flux amplitude and the motor speed. The underlying design objective is to endow the closed loop system with high performance dynamics for high speed ranges while keeping the required stator voltage within the inverter ceiling limits. A comparative study between the performances of the proposed controller and field oriented control is carried out. The methods are compared in terms of their ability to handle loads on the motor shaft, their speed tracking capability and their sensitivity to operating condition variations. To estimate the rotor flux, an open loop observer is developed.

A New Induction Motor Drive Based on the Flux Vector Acceleration Method

A novel control strategy for the induction motor drive, based on the field acceleration method, is presented. The torque is controlled through variations of the stator flux angular velocity. The stator flux is controlled by using a feedforward control scheme, with the stator flux reference vector adjusted so as to obtain the fixed rotor flux amplitude. The applied controller assures a fast torque response, low torque ripple in the steady state, and drive operation with a constant switching frequency. The algorithm includes the improved stator and rotor flux estimation that guarantees the stable drive operation in all operating conditions, even at low speeds. The experimental tests verify the performance of the proposed algorithm, proving that good behavior of the drive is achieved in the transient and steady-state operating conditions.