High Performance Direct Torque Control Research Articles

An enhanced direct instantaneous torque control of switched reluctance motor drives using ant colony optimization

The highly nonlinear characteristics of switched reluctance motors (SRMs) are the drawback that complicates their control and modeling. Hence, obtaining the best performance becomes a challenging task. Therefore, this paper presents an upgraded methodology of the ant colony optimization (ACO) technique. The proposed multistage ant colony optimization (MSACO) enhances the search capability of the classical ACO. Therefore, it helps to find the best switching angles without violating pre-specified constraints. The optimized angles are used to implement an improved high-performance direct instantaneous torque control (DITC) drive. This work focuses on reducing torque ripple, improving motor efficiency, and preventing generating a considerable amount of negative torque. Moreover, a current detector is used to provide information about negative torque production and thus helps to find optimal angles and avoid the set of solutions that give a considerable amount of negative torque. Furthermore, a new switching strategy is utilized to implement an efficient hysteresis torque controller, where the selection of the switching mode of the power converter is entirely determined based on the inductance profile of the SRM. The utilized switching strategy guarantees accurate torque tracking over the entire phase excitation period; thus, the machine's torque profile is improved further. The simulation results showed the superiority of the proposed control method over the traditional control method. In addition, the experimental measurements have been carried out to verify the simulation findings using a three-phase 750 W, 12/8 SRM prototype.

FPGA Hardware in the Loop Validation of Asynchronous Machine with Full Direct Torque Control Implementation

This article provides a full hardware implementation for direct torque control (DTC) of an asynchronous motor (AM) on the Field Programmable Gate Array (FPGA). Due to its high processing frequency, the FPGA circuit presents an alternative for achieving a high performance DTC implementation. This cannot be achieved by any DSP or microcontroller application. The proposed hardware architecture implements three components of DTC control strategy (the integral proportional speed regulator, the estimation and the switching blocks). This implementation has the advantage of being faster, more efficient and with minimum hardware resources on the target FPGA board. The hardware architecture of the DTC control was designed and simulated in Matlab / Simulink using XSG blocks, then synthesized with the Xilinx ISE 14.2 tool, implemented and validated on the Xilinx Virtex-4 FPGA circuit by Hardware in the Loop process.

Direct Torque Control of Induction Motor Based on Particle Swarm Optimization

Induction Motor (IM) is most commonly used in different industrial applications, that require fast dynamic response and accurate control over wide speed ranges. Therefore, this paper proposes high performance Direct Torque Control (DTC), which is closed loop control system to improve the dynamic performance of IM. The main objective of this work is to improve the speed response of IM during different load and speed conditions. Proportional-Integral (PI) controller based on Particle Swarm Optimization (PSO) technique is used for optimal gains tuning. The results show the improvement in the speed response of DTC using PSO technique when compared with conventional PI and the conventional DTC (without PI), in terms of reducing steady state error, settling time, overshoot and ripple reduction which make this controller more robust to variation in load and speed. The simulation of the overall drive system is performed using MATLAB/Simulink program version 7.10 (R2010a).Keywords: Induction Motor (IM), Direct torque control, PI controller and Particle Swarm Optimization (PSO).

Feedback linearization based sensorless direct torque control using stator flux MRAS-sliding mode observer for induction motor drive

The high-performance Direct Torque Control (DTC) requires accurate knowledge of flux and speed information. Furthermore, the elimination of sensors leads to reduced overall cost and size of the electric drive system and subsequently improving its reliability. This paper proposes an effective sensorless direct torque control scheme for induction motor drive. The proposed scheme consists of enhancing the decoupling structure and variable estimation as well. Therefore, an enhanced direct flux and torque control based on feedback linearization is implemented in one hand. This allows obtaining a linear decoupled control together with minimized flux and torque ripples. In another hand, a combined sliding mode observer and model reference adaptive system is associated with the control scheme as sensorless algorithms for rotor speed and flux estimation. This conjunction is intended to enhance the sliding mode observer performances especially at low speed operations and reduce its sensitivity to noise and system uncertainties as well. The effectiveness of the proposed control algorithm has been verified through simulation and experimental work using MATLAB/Simulink software and dSpace 1104 implementation board respectively.

Sensorless Speed Control and High-Performance Fault Diagnosis in VSI-Fed PMSM Motor Drive Under Open-Phase Fault: Analysis and Experiments

This paper aims to provide a high-performance sensorless fault-tolerant direct torque control of permanent magnet synchronous motor based on nonlinear position and speed observer. The nonlinear observer is based on a trigonometric function to estimate the rotor position, and a proportional–integral controller is used to estimate the speed from estimated position. A faulty leg (open phase) in the PWM VSI changes the corresponding terminal voltage and introduces the voltage distortions to each phase voltage. The ordinary two-level inverter is composed of three legs. In the proposed fault-tolerant inverter, a redundant leg is added that replaces the faulted leg. The detection of the open-phase fault is based only on the current signals and the maximum threshold they exceed that in case of fault.

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.

High Performance Direct Torque Control for Induction Motor Drive Fed from Photovoltaic System

High Performance Direct Torque Control for Induction Motor Drive Fed from Photovoltaic System

High performance DTC of induction motor drives over a wide speed range

This paper presents an effective scheme to minimize the torque ripples for direct torque control (DTC) of induction motor drives. The switching strategy compares the torque error from a PI torque controller with two triangular waveforms, and then produces a constant switching frequency, which is determined by the frequency of the triangular waveforms and is almost independent of the speed. The gains of PI torque controller are designed based on root-locus plot to guarantee a good convergence of the torque error. In order to examine the performance of the proposed DTC scheme for an induction motor drive, a complete simulation model is developed using MATLAB/Simulink and validated under a wide speed range. The proposed DTC drive is also implemented and tested in real-time using a DSP-DS1102 control board for a prototype 1 KW induction motor. Simulation and experimental results show that the proposed DTC drive exhibits a good dynamic and steady state performances with low torque ripples over a wide speed control range.

High performance direct torque control of electrical aerodynamics load simulator using adaptive fuzzy backstepping control

Electrical load simulator is hardware in the loop simulator used to exert real-time aerodynamics loads on the servo actuation system of a flight vehicle under test according to flight conditions. This article investigates direct torque control of electrical load simulator system using adaptive fuzzy backstepping method. To analyze the effect of extra torque disturbance on electrical load simulator system, detailed mathematical formulations are derived. Considering practical aspects of the proposed method, state vector is estimated using a state predictor, and parameters of the system are estimated using algebraic method. Fuzzy logic system is used to estimate extra torque disturbance acting on electrical load simulator system, but the approximation error may not converge to zero, which may affect control performance. Similarly, the parameters of the system may vary with time; thus the lumped disturbance due to time variation of parameters and fuzzy approximation error is compensated using adaptive control law derived based on estimated error dynamics between actual plant and state predictor. Moreover, to improve transient response, a novel saturation function-based transient performance controller is introduced. The performance of the proposed control is verified using extensive numerical simulations.

High-performance direct torque and flux control of an induction motor drive using sliding-mode and fuzzy logic speed controllers

In this research study, direct torque and flux control of an Induction Motor Drive (IMD) using Sliding-Mode Speed Controllers (SMSC) and Fuzzy-Logic Speed Controller (FLSC) are presented to achieve high performance of stator current, electromagnetic torque and motor speed in both transient as well as in steady-state conditions. The PI Speed Controller (PISC) gives good steady-state performance, but poor dynamic response. Therefore, the SMSC is considered to achieve continuous control of motor speed and also electromagnetic torque. Furthermore, FLSC is considered to get high performance, dynamic tracking and speed accuracy at various load torque conditions. The performances of each speed controller techniques are tested under various load toque and speed condition for its robustness. A detailed comparison of different control approaches are carried out in a MATALB/Simulink environment at different operating conditions, such as forward and reversal motoring with no-load, load, sudden change in speed and sudden zero speed.

High Performance Direct Torque and Flux Control of Induction Motor Drive Using Fuzzy Logic Based Speed Controller

In this research study, direct torque and flux control of induction motor drive (IMD) using fuzzy logic based speed controller (FLSC) is implemented to minimize the ripple contents of stator current, flux and torque and also improve the speed responses under transient and steady state operating conditions. It is quite difficult to optimize the high performance of an IMD using conventional PI- speed controller (PISC), because of the nonlinear model of induction motor drive. The conventional PI-controller requires accurate and continuous tuning of gain values. Therefore, the FLC technique is implemented to improve the system performance. The detailed simulation results are presented in forward and reversal motoring under 1200 rpm and 900 rpm with no-load, load, sudden change in speed and sudden zero speed operating conditions using MATLAB/Simulink software to support the feasibility of the control strategy. To validate the FLSC control approach, the system is also implemented on real-time system and adequate results are reported for its validation

High performance direct torque control schemes for an IPMSM drive

Classical direct torque control (DTC) has several advantages, however, the high torque and flux ripples and variable switching frequency are considered its main drawbacks. In this paper, two techniques are proposed to improve the classical DTC performance of the interior permanent magnet synchronous motor (IPMSM) drive. Firstly, a torque/flux sliding mode controller (SMC) is used to replace the hysteresis comparators and lookup table of the classical DTC. The proposed torque/flux SMC has two integral switching functions for torque and flux control. The idea of total SMC is selected to avoid the reaching phase problem; however, the chattering problem is considered its main drawback. Secondly, to overcome the chattering problem, a torque/flux diagonal recurrent neural network (DRNN) controller is designed to replace the SMC. DRNN has several advantages such as recurrence and simple construction. In addition, a full motor dynamic model and the band of parameters variation are not required. Dynamic off line back-propagation algorithm is used to train the torque/flux DRNN controller. In addition, a space vector modulation (SVM) is combined with the two proposed techniques to provide constant switching frequency and high voltage resolution.The feasibility and effectiveness of the proposed systems have been demonstrated through computer simulations. A comparison between the classical DTC, torque/flux SMC and torque/flux DRNN controller have been made in order to confirm the validity of the proposed schemes. The superiority of the torque/flux DRNN controller has been proved through comparative simulation results.

Performance Evaluation of an Integrated Starter-Alternator with an IPM Synchronous Machine under Sensor-less Operation

This paper presents performance evaluation of an Integrated Starter-Alternator (ISA) prototype with an Interior Permanent Magnet (IPM) synchronous machine under sensor-less operation. To attain a high starting torque at zero speed and in subsequent extremely low speed range, a hybrid signal injection method is proposed. At higher speed, an improved stator flux observer is used for the stator flux estimation. This observer is able to produce accurately-estimated stator flux linkage for high performance Direct Torque and Flux Control (DTFC) implementation. The sensor-less DTFC IPM synchronous machine drive takes full advantage of the capacity of the power converter and fulfills the control specifications for the ISA. The trajectory control algorithm responds rapidly and in a well behaved manner over a wide range of operating conditions. The experimental results verify the feasibility and advantages of the system.

High-Performance Speed Sensorless Direct Torque Control of PMSM

A high-performance speed sensorless direct torque control (DTC) system of permanent magnet synchronous motor (PMSM) is presented in this paper. The stator flux linkage, speed, rotor position and load torque of PMSM are observed using a fourth-order Extended Kalman Filter (EKF) and a second-order Kalman Filter (KF) and the observed load torque is used for feed-forward compensation of reference torque. Simulation results clearly demonstrate the performance of speed can be improved when load torque is changed and the validity of the proposed control strategy.

Adaptive supervisory Gaussian-cerebellar model articulation controller for direct torque control induction motor drive

This study develops an adaptive supervisory Gaussian-cerebellar model articulation controller (ASGCMAC) and implements it in a sensor-less direct torque control (DTC) system for controlling induction motor speed. The inherent uncertainties of a DTC system, including parametric uncertainties and the uncertainties in external load torque, make control tasks difficult. A model-free approach, ASGCMAC, is adopted to build a high-performance DTC induction motor drive. The proposed method comprises two parts - a supervisory controller and a Gaussian-CMAC (GCMAC) subsystem. The supervisory controller monitors the control process to maintain the tracking error within a pre-defined range; the GCMAC sub-system learns and approximates system dynamics. The parameters of ASGCMAC are adjusted online according to adaptive rules, which are derived from Lyapunov stability theory, guarantee system stability. Four control schemes, ASGCMAC, supervisory controller, proportional-integral (PI) control and conventional CMAC, are experimentally investigated and the performance index, root-mean-square error (RMSE), is evaluated in each scheme. The results reveal that ASGCMAC outperforms the other comparison schemes. In addition, the robustness of the proposed scheme to the parameter variation and external load torque disturbance has been verified via simulation and experiments.

A New Torque and Flux Controller for Direct Torque Control of Induction Machines

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper presents the implementation of a high-performance direct torque control (DTC) of induction machines drive. DTC has two major problems, namely, high torque ripple and variable switching frequency. In order to solve these problems, this paper proposed a pair of torque and flux controllers to replace the hysteresis-based controllers. The design of these controllers is fully discussed and a set of numerical values of the parameters for the proposed controllers is given. The simulation of the proposed controllers applied to the DTC drive is presented. The simulation results are then verified by experimental results. The hardware implementation is mainly constructed by using DSP TMS320C31 and Altera field-programmable gate array devices. The results prove that a significant torque and stator flux ripples reduction is achieved. Likewise, the switching frequency is fixed at 10.4 kHz and a more sinusoidal phase current is obtained. </para>

Sensorless direct torque control of an induction motor by a TLS-based MRAS observer with adaptive integration

This article presents a new speed and flux estimation algorithm for high-performance direct torque control (DTC) induction motor drives based on model reference adaptive systems (MRAS) observers using linear artificial neural networks (ANNs). Two completely new improvements of MRAS speed and flux observers are presented here: the first is a solution to the open-loop integration problem in the reference model, based on the voltage model of the induction machine, by means of a new adaptive neural integrator, the second is the employment of a new adaptation law in the ANN adaptive model, based on the total least-squares (TLS) technique. In particular, the adaptive neural integrator is based on two adaptive noise filters which completely cancel any DC drift present in the voltage or current signals to be integrated. This neural integrator does not need any a priori training of its two only neurons, adapting itself on-line. With regard to the ANN-based adaptive model, since the most suitable least-square technique to be used for training is the TLS technique, here the neuron is trained on-line by means of a TLS EXIN algorithm which is the only neural network able to solve a TLS problem recursively. Also the TLS EXIN algorithm does not require any a priori training, since it adapts itself recursively on-line. Moreover, to improve the dynamical performances of the speed loop of the drive, the adaptive model has been used as predictor, i.e. without any feed-back between its outputs and its inputs. The sensorless algorithm has been verified experimentally both on the classic DTC technique and on the DTC-SVM (space vector modulation), by adopting a proper test set-up. The speed observer has been tested in the most challenging operating conditions. The experimental results show that the dynamical performances of the sensorless drive are comparable or even better than those obtained with the corresponding DTC drives with encoders as for the medium to high-speed ranges. As for low-speed ranges, the presented sensorless DTC algorithm outcomes the performance presented in the literature for MRAS systems, thus permitting to have an accurate estimation equal or better than that obtainable with more complex observers. Finally, experimental results show that the MRAS speed observer is robust to load torque perturbations and permits zero-speed operation at no-load conditions.

High Performance Direct Torque Control of Switched Reluctance Motor Drives

This article presents a novel method for the production of smooth torque as well as high performance speed controller for 6/4 switched reluctance motor (SRM) drives. The proposed method is based on direct torque control (DTC) technique. According to the sign of the error between the command and actual motor torque in addition to the rotor angle, the inverter output voltages are determined. Instead of current controllers, the DTC directly turns the power electronic switches on and off and, hence, fast response is achieved. The nonlinear SRM model is considered and simulation results are obtained to validate the proposed controller.

High-performance direct torque control of an induction motor

A novel direct torque control method for an induction motor is presented which is quite different from field-oriented control. Improving the torque response of a large-capacity induction motor using two sets of three-phase inverters and an open-data induction motor is of special concern. Instantaneous voltage vectors applied by an inverter have redundancy characteristics which provide some flexibility for selecting the inverter switching modes. By using this switching freedom, control is achieved according to the following priorities: (1) high-speed torque control; (2) regulation of the primary flux; (3) decreasing the zero phase sequence current; and (4) minimization of the inverter switching frequency. Simulations and experiments have been carried out to verify the feasibility of this priority control, accompanied by comparisons with another control scheme. Torque frequency-response corner frequencies above 2000 Hz have been experimentally measured, and time constants of 4 ms have been achieved for rotor-speed step responses from -500 to 500 r/min. The peak transient torque during the step change is about 20 times the rate torque. >