Torque Control Of Induction Motor Research Articles

Weighting Factor Selection Techniques for Predictive Torque Control of Induction Motor Drives: A Comparison Study

For the last few years, predictive torque control (PTC) has attracted the attention of the researchers due to its simplicity and effectiveness. In PTC, flux-weighting factor needs to be wisely adjusted since it affects greatly the performance of the drive system. Many research trials were devoted to select this weighting factor or even eliminate it. Each of these trials illustrates a method to overcome this problem and presents a solution to the conventional weighting factor calculation method. This paper presents a critical evaluation of the performance of recently proposed methods for weighting factor selection for finite control set PTC. Based on the way the weighting factor is calculated, the methods are classified to offline and online methods. In this study, more focus will be directed to the evaluation of the online methods since they can update the weighting factor automatically if the operating point changes. Specifically, four recently developed methods along with the conventional method are considered in this study. Flux ripple, torque ripple, current total harmonic distortion, and average switching frequency are adopted as the judging criteria for this comparison. Simulations at different operating points are used to assess the performance of each method, and the characteristics of each method are compared according to the performance indices suggested. The strengths and weaknesses of each method are highlighted. Therefore, the suitable method can be identified according to different application requirements.

High Performance Direct Torque Control of Induction Motor Drives: Problems and Improvements

This paper presents some of the main problems, as well as their root causes, of Direct Torque Control (DTC) 3-phase induction motor drive. The high torque ripple in DTC drive due to the hysteresis controller inevitably becomes worst with the discrete implementation of the drive system. The hysteresis controller also causes variable switching frequency that depends on operating conditions, especially the speed. The simplification used in stator flux expression for voltage vectors selection in flux control results in a poor flux regulation at low speed. To overcome these problems, techniques that have been implemented at UTM-PROTON Future Drive Laboratory (UPFDL) are presented and described. Some experimental results obtained from the previous works are also presented and discussed.

Improved Weighting Factor Selection for Predictive Torque Control of Induction Motor Drive Based on a Simple Additive Weighting Method

A predictive torque control (PTC) technique is emerging as an effective alternative for induction motor drives because of its simple structure, ability to include control parameters directly into the cost function, and fast dynamic response. To implement PTC for induction motor drive, both stator flux and torque errors are predicted for each switching state of the converter and the combined error is determined with the help of cost function using a suitable stator flux weighting factor. However, the selection of suitable weighting factor is a tedious and complex task. In this paper, a simple additive weighting method is introduced in the cost function optimization to simplify the weighting factor selection process. To observe the effectiveness of the proposed control algorithm, both simulation and experimental results are presented for a two-level voltage-source-inverter-fed induction motor drive and compared with conventional PTC under various operating conditions. The proposed control technique achieves low-torque ripple along with reduced switching frequency.

A Review on Constant Switching Frequency Techniques for Direct Torque Control of Induction Motor

The Direct Torque Control (DTC) of induction machine has received wide acceptance in many Variable Speed Drive (VSD) applications due to its simple control structure and excellent torque dynamic control performances. However, the conventional DTC which employs a two-level inverter and hysteresis controllers produces two major drawbacks, namely, larger torque ripple and variable switching frequency, which might produce a very high switching frequency (or power loss), particularly at a very low speed operation. This paper highlight the common methods used to provide the constant switching frequency for DTC drives for Induction Motor that able to minimize the power losses and reduced the torque ripple.

Indirect field‐oriented torque control of induction motor considering magnetic saturation effect: error analysis

This study investigates the causes and calculation formulas of steady-state torque and rotor flux errors, when an induction motor considering magnetic saturation effect is controlled by standard indirect field-oriented control algorithm. First, two reasons that causing the errors are analysed. One is mutual inductance mismatch between controller and motor. Another is rotor flux orientation deviation, resulting in the failure of decoupling of the magnetising and torque-producing currents. Then, the equations for calculating steady-state errors (orientation error, rotor flux error and torque error) are derived. The errors are related to reference torque, reference rotor flux and mutual inductance deviation. In addition, the characteristic maps of errors with respect to reference values are drawn. The accuracy and correctness of derived equations are validated by simulation and experimental results.

Multilevel inverter with space vector modulation: intelligence direct torque control of induction motor

An Intelligence direct torque control (DTC) of induction motor using multilevel inverter with space vector modulation (SVM) is proposed in this study. The novelty of the proposed intelligence technique is an artificial neural network (ANN), which is utilised for the DTC of the induction motor. Here, ANN has been trained by using the target parameters such as reference quadrature and direct axis voltage with the corresponding input parameters change in motor torque and flux. The change in motor torque and flux parameters are identified by using the multilevel inverter output voltage and current. The back propagation process is used for the training process of the ANN. By using the ANN outputs, the SVM technique develops the control pulses for the multilevel inverter. Then the proposed intelligence technique is implemented in the MATLAB/simulink platform and the effectiveness is analysed by comparing with the different case studies and different methods. The comparison results demonstrate the superiority of the proposed approach and confirm its potential to solve the problem.

Improved Sensorless Direct Torque Control of Induction Motor Using Fuzzy Logic and Neural Network Based Duty Ratio Controller

This paper presents improvements in Direct Torque control of an induction motor using Fuzzy logic with Fuzzy logic and neural network based duty ratio controller. The conventional DTC (CDTC) of induction motor suffers from major drawbacks like high torque and flux ripples and poor transient response. Torque and flux ripples are reduced by replacing hysteresis controller and switching table with Fuzzy logic switching controller (FDTC). In FDTC the selected switching vector is applied for the complete switching time period. The FDTC steady state performance can be improved by using duty ratio controller, the selected switching vector is applied only for the time determined by the duty ratio (δ) and for the remaining time period zero switching vector is applied. The selection of duty ratio using Fuzzy logic and neural networks is projected in this paper. The effectiveness proposed methods are evaluated using simulation by Matlab/Simulink.

Improved Sensorless Direct Torque Control of Induction Motor Using Fuzzy Logic and Neural Network Based Duty Ratio Controller

Improved Sensorless Direct Torque Control of Induction Motor Using Fuzzy Logic and Neural Network Based Duty Ratio Controller

Finite control set predictive torque control for induction motor drive with simplified weighting factor selection using TOPSIS method

Finite control set predictive torque control (FCS-PTC) becomes popular for induction motor drives due to its simple structure and flexibility of including additional control parameters into the control law. However, primary concern of this control technique is the selection of suitable weighting factors in the cost-function. Usually, empirical method is used to select the weighting factors, which is time-consuming and heuristic process. In this study, Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method is introduced in the cost-function optimization to simplify the difficulties involved in the weighting factor selection. This method selects an optimal control action, which is closer to positive ideal control action and far away from negative ideal control action. This ensures the selection of optimal control action in each sampling period based on the priorities given to control parameters in the cost-function. Further, to reduce the computational burden of proposed technique, a predefined set of switching states are used for the cost-function optimization based on previous optimal control action. Both simulation and experimental studies are carried out for a two-level voltage source inverter fed induction motor drive. These results are compared with conventional FCS-PTC technique to highlight the merits of proposed technique.

Delta/Fork-Connected Transformer-Based 72-Pulse AC–DC Converter for Power Quality Improvement

ABSTRACTThis paper presents a delta/fork-connected transformer-based 72-pulse AC–DC converter feeding direct torque-controlled induction motor drives (DTCIMDs) for improving power quality. The proposed converter consists of two paralleled 18-pulse AC–DC converters along with pulse-doubling circuit at DC bus. The pulse-doubling circuit is used in achieving the pulse multiplication in a 36-pulse AC–DC converter. The Thirty-six pulse topology is obtained via two paralleled 18-pulse AC–DC converters each of them consisting of a 9-phase (9-leg) diode-bridge rectifier. The design of proposed magnetics shows the flexibility in varying the voltage ratio of the delta/fork-connected transformer for making it suitable for retrofit applications where a 6-pulse diode-bridge rectifier is being utilized. Independent operation of paralleled diode-bridge rectifiers, i.e. DC-ripple re-injection methodology, requires a Zero Sequence Blocking Transformer (ZSBT). Finally, a tapped interphase reactor is connected at the output of ZSBT to double the pulse numbers of output voltage up to 72 pulses. The proposed 72-pulse AC–DC converter with the DTCIMD has been implemented and simulated using Matlab/Simulink software. Simulation results confirmed the significant improvement of the power quality indices on input AC mains and on DC bus (consistent with the IEEE-519 standard requirements) at the point of common coupling. Also, a laboratory prototype is implemented using the proposed design and the experimental results confirm the simulation results at various loads. Results show that input current total harmonic distortion (THD) is less than 3% for the proposed 72-pulse topology at variable loads. Furthermore, near unity power factor is obtained for a wide operating range of the drive.

Design and Experimental Verification of 20-Pulse AC–DC Converter for Retrofit Applications and Harmonic Mitigation

This paper presents the design and analysis of a polygon-connected autotransformer based 20-pulse AC–DC converter which supplies direct torque-controlled induction motor drives (DTCIMDs) in order to have better power quality conditions at the point of common coupling. The proposed converter output voltage is accomplished via two paralleled 10-pulse AC–DC converters each of them consisting of five-phase diode bridge rectifier. An autotransformer is designed to supply the rectifiers. The design procedure of magnetics is in such a way that makes it suitable for retrofit applications where a six-pulse diode bridge rectifier is being utilized. The proposed structure improves power quality criteria at AC mains and makes them consistent with the IEEE-519 Standard requirements for [Formula: see text]. Furthermore, near-unity power factor is obtained for a wide range of DTCIMD operations. A comparison is made between six-pulse and proposed converters from the viewpoint of power quality indices. Results show that input current total harmonic distortion (THD) is less than 8% for the proposed topology at variable loads. A laboratory prototype of the proposed polygon-connected autotransformer-based 20-pulse AC–DC converter is developed and test results are presented to validate the developed design procedure and the simulation models of this AC–DC converter under varying loads.

Finite-Control Set Model Predictive Control Method for Torque Control of Induction Motors Using a State Tracking Cost Index

This paper presents a novel torque control method for two-level-inverter-fed induction motor drives. The control principle is based on a finite-control set model predictive control (FCS-MPC) using a state tracking cost index. In the online procedure of the proposed FCS-MPC, the optimal voltage vector and its corresponding optimal modulation factor are determined based on the principle of torque and rotor flux error minimization. In this method, a reference state is determined in a systematic way so that the reference torque tracking with maximum torque per ampere and flux-limited operation could be achieved. In addition, a weighting matrix for the state tracking error is optimized in offline using the linear matrix inequality based optimization problem. The efficacy of the proposed FCS-MPC method is proved by the simulation and experimental results at different working circumstances. The comparison of the presented control system with the conventional FCS-MPC and with other reported FCS-MPC with modulation control is made. The proposed algorithm yields fast dynamic performance and minimum torque and current ripples at different speed and torque levels.

Improvements in direct torque control of induction motor for wide range of speed operation using fuzzy logic

The main objective of this paper is to ameliorate the performance of direct torque control of induction motor for a wide range of speed control using fuzzy logic. The major drawbacks of conventional direct torque control are high torque, flux ripples and poor dynamic response at low speed. In this paper the CDTC is improved by fuzzy logic switching controller and fuzzy logic duty cycle controller. In FDTC with FDCC the selected voltage vector is applied only for the duty cycle time period (δ) determined. Simulation results validate that the proposed scheme shows improved dynamic performance of the drive for a wide range of speed (0–100rad/s) and the torque and flux ripples are reduced by 90% compared to CDTC.

Robust SVM-direct torque control of induction motor based on sliding mode controller and sliding mode observer

This paper proposes a design of control and estimation strategy for induction motor based on the variable structure approach. It describes a coupling of sliding mode direct torque control (DTC) with sliding mode flux and speed observer. This algorithm uses direct torque control basics and the sliding mode approach. A robust electromagnetic torque and flux controllers are designed to overcome the conventional SVM-DTC drawbacks and to ensure fast response and full reference tracking with desired dynamic behavior and low ripple level. The sliding mode controller is used to generate reference voltages in stationary frame and give them to the controlled motor after modulation by a space vector modulation (SVM) inverter. The second aim of this paper is to design a sliding mode speed/flux observer which can improve the control performances by using a sensorless algorithm to get an accurate estimation, and consequently, increase the reliability of the system and decrease the cost of using sensors. The effectiveness of the whole composed control algorithm is investigated in different robustness tests with simulation using Matlab/Simulink and verified by real time experimental implementation based on dS pace 1104 board.

Finite-State Predictive Torque Control of Induction Motor Supplied From a Three-Level NPC Voltage Source Inverter

Finite-state predictive torque control (FS-PTC) of an induction motor (IM) drive has been widely investigated for two-level voltage source inverter recently. This control method suffers from high and variable switching frequencies in a wide range, due to the limited number of available voltage vectors of the power converter. In order to take advantage of multilevel inverter drives which offer the benefits of low harmonic distortion of the stator currents, torque ripple, and low switching frequency, this paper proposes the integration of the FS-PTC with a three-level neutral-point clamped (3L-NPC) inverter driven IM drive. The drawback inherited from the topology of 3L-NPC voltage source inverter (VSI), such as neutral-point voltage, is easily handled by treating it as a variable to the cost function. Similarly, apart from the inverter topology itself, the average switching frequency is reduced further, and is maintained almost constant over a wide speed range. The effectiveness of the proposed FS-PTC in terms of torque and flux responses, capacitor voltage balancing, and low average switching frequency is validated through experimental results.

A Fuzzy Direct Torque Control of Induction Motor for FPGA Implementation

A Fuzzy Direct Torque Control of Induction Motor for FPGA Implementation

Improved Stator Flux Estimation for Direct Torque Control of Induction Motor Drives

<p>Stator flux estimation using voltage model is basically the integration of the induced stator back electromotive force (emf) signal. In practical implementation the pure integration is replaced by a low pass filter to avoid the DC drift and saturation problems at the integrator output because of the initial condition error and the inevitable DC components in the back emf signal. However, the low pass filter introduces errors in the estimated stator flux which are significant at frequencies near or lower than the cutoff frequency. Also the DC components in the back emf signal are amplified at the low pass filter output by a factor equals to . Therefore, different integration algorithms have been proposed to improve the stator flux estimation at steady state and transient conditions. In this paper a new algorithm for stator flux estimation is proposed for direct torque control (DTC) of induction motor drives. The proposed algorithm is composed of a second order high pass filter and an integrator which can effectively eliminates the effect of the error initial condition and the DC components. The amplitude and phase errors compensation algorithm is selected such that the steady state frequency response amplitude and phase angle are equivalent to that of the pure integrator and the multiplication and division by stator frequency are avoided. Also the cutoff frequency selection is improved; even small value can filter out the DC components in the back emf signal. The simulation results show the improved performance of the induction motor direct torque control drive with the proposed stator flux estimation algorithm. The simulation results are verified by the experimental results.</p>

Direct Torque Control of Induction Motor with Common-Mode Voltage Elimination

If the common-mode voltage in the induction motor drive is not eliminated, it may cause failure of motor bearings and malfunctioning of the electrical equipment associated with the drive. This article proposes the modified direct torque control technique to control the induction motor fed by three-level inverter, commonly called a neutral-point-clamped inverter. The selective voltage vectors in three-level inverter determine elimination of the common-mode voltage. The classic three-level direct torque control based on selection of 6-full, 6-half, and 2-zero voltage vectors out of available 27 is modified so that the 6-intermediate voltage vectors and a zero voltage vector are employed. A comparative investigation with another three-level direct torque control method which reduces both common-mode voltage and torque ripple is also carried out. These methods are compared with classic two-level direct torque control method in context of common-mode voltage, torque ripple, current total harmonic distortion (THD) and DC-link utilization. The simulation and experimental results validate the proposed common-mode voltage elimination and common-mode voltage reduction direct torque control techniques.

Switching losses minimization by using direct torque control of induction motor

Direct torque control is becoming the industrial standards for induction motor torque control. This paper presents switching loss minimization technique of improved direct torque control (DTC) of induction motor. Direct torque control (DTC) of an induction motor supplied by a voltage source inverter is a simple scheme that does not need long computation time, can be implanted without speed sensors and is insensitive to parameter variations. In principle, the motor terminal voltages and currents are used to estimate the motor flux and torque. Based on the instantaneous errors in torque and stator flux magnitude and estimates of the flux position, a voltage vector is selected to limit the flux and torque errors within their flux and torque hysteresis bands. In the conventional DTC, the selected voltage vector applies for the whole switching period, irrespective of the magnitude of the torque error. DTC drive gives variable switching frequency and high torque ripple. DTC gives torque and flux ripples because no any VSI states are capable to generate the exact voltage vector from switching table required to make zero both the torque electromagnetic error and the stator flux error. To minimize this problem, a torque hysteresis band with variable amplitude fuzzy logic controller is proposed. The fuzzy logic controller is used to reduce the flux and torque ripples and it improves performance DTC especially at low speed. A duty ratio control scheme for an inverter-fed induction machine using DTC method is presented in this article. The use of the duty ratio control gives improved steady state torque response, with less torque ripple than the conventional DTC. Fuzzy logic control (FLC) used to implement the duty ratio controller. Total harmonic distortion (THD) calculation of electromagnetic torque, rotor speed and stator current of DTC and DTC with fuzzy has done successfully in this article. With the help of FLC with duty ratio, 8% THD in torque, speed and stator current have minimized compared with DTC (Uddin and Hafeez, 2012). In this paper, switching loses minimization technique through THD minimization. Switching losses are minimized because the transistors are only switched when it is needed to keep torque and flux within their hysteresis bounds, improve efficiency & reduced losses. Direct torque control with the fuzzy logic controller has verified by MATLAB SIMULINK and experimentally.

Enhanced weighting factor selection for predictive torque control of induction motor drive based on VIKOR method

Predictive torque control (PTC) is one of the widely used modern control techniques for induction motor drives due to its merits such as; implementation is straightforward and direct inclusion of control parameters into the cost-function is possible. However, the main drawback of this technique is the selection of appropriate weighting factor in the cost-function. In this study an attempt is made to simplify the weighting factor selection by using VlseKriterijuska Optimizacija I Komoromisno Resenje (VIKOR) method and the cost function of PTC is modified accordingly. Usage of VIKOR method in the cost-function optimisation introduces the compromise ranking to select an optimal control action. Both simulation and experimental results are carried out for a two-level voltage source inverter fed induction motor drive with the proposed control technique and the results are compared with conventional PTC technique. These results confirm that proposed method retains the dynamic response achieved by the conventional PTC along with reduced torque ripple and switching frequency.