Direct torque control for induction machine based on AC-AC matrix converter

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 FPGA 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.

Direct torque control (DTC) of induction machines is known to have a simple control structure with comparable performance to that of the field-oriented control technique. Two major problems that are usually associated with DTC drives are: switching frequency that varies with operating conditions and high torque ripple. To solve these problems, and at the same time retain the simple control structure of DTC, a constant switching frequency torque controller is proposed to replace the conventional hysteresis-based controller. In this paper, the modeling, averaging, and linearization of the torque loop containing the proposed controller followed by simulation and experimental results are presented. The proposed controller is shown to be capable of reducing the torque ripple and maintaining a constant switching frequency.

The effects on torque performance when using small voltage vectors of Matrix Converters is investigated in this paper. These vectors are used in order to reduce the electromagnetic torque ripple which appears when Direct Torque Control technique is used in Induction Motors. Direct Torque Control for Induction Motors using Matrix Converters is reviewed and it is pointed out the problem of the electromagnetic torque ripple which is one of the most important drawbacks of the Direct Torque Control. A new look-up table for Direct Torque Control using small vectors of Matrix Converters is developed. With the new look-up table, the system will differentiate between small and large torque errors and consequently reduce the electromagnetic torque ripple. A comparison between the classical Direct Torque Control using Matrix Converters and the proposed method is carried out. Results which demonstrate the improvement of the novel Direct Torque Control are shown.

Matrix Converter rather than voltage source inverter can be used as high-performance technique supplying electric motor in Direct Torque Control (DTC). DTC's most significant deficiency in induction motor, magnetic torque ripple, can be markedly reduced by appropriate space voltage-vectors whose influence on stator flux and electromagnetic torque in DTC of induction machine that uses Matrix Converter the subject of this work. DTC degrees of freedom were shown seriously limited by 60° flux sectors, thus division to twelve 30° sectors of flux-space vector hexagon is proposed. The increased Matrix Converter degrees of freedom were then extracted for DTC implementation.

The direct torque control (DTC) system, which is based on induction machine drive is a developed and simple control method. It allows high dynamic performance with very simple hysteresis control scheme; However, its disadvantages are high current, torque, and flux ripple. In this paper, DTC of induction machine drive has been improved by using the applications of artificial intelligence (AI) approaches to reduce the current, torque, and flux ripples and also get better performance of the machines. At the conclusion of this study, the outcomes of traditional DTC and artificial intelligent methods are compared. By the program MATLAB/SIMULINK, the modeling and simulation results of the DTC system for induction machine (IM) have been proposed.

In this paper, a predictive direct torque control (DTC) of induction motor (IM) drive is presented. The control uses stator flux and current vectors as state variables. Predicted torque variation, with reference to its unforced response during each sampling time interval, is imposed with the aim of determining the pulse widths of the chain voltages of the supply inverter. The existence domain of the state variables in each sampling time interval is determined and depicted graphically. Inverter voltage saturation and current limitation constraints are also taken into account and shown graphically. The proposed control technique is employed in simulating a DTC IM drive by the Matlab Simulink tool. The simulation results, which are compared with those obtained by the traditional constant switching frequency DTC, highlight the good performance of the drive, especially referring to torque ripple and low-speed operation.

A system with fast torque response is very beneficial in applications where direct torque control (DTC) is highly desirable. The principle of DTC is to control machine torque and flux directly by selecting the switching states of inverter according to the errors of torque and flux; however, the response of direct torque control is slower during start-up and during change in load. Fuzzy control with grey prediction strategy is proposed for the implementation of DTC to improve its slow response. Moreover, it uses less sensors than the conventional method. Experimental implementation of the fuzzy logic controller and the grey predictor is carried out to verify the behavior of the controller. The controller is implemented with a single board computer that uses a TMS320C30 DSP.

Introduction. Currently, the direct torque control is very popular in industry and is of great interest to scientists in the variable speed drive of asynchronous machines. This technique provides decoupling between torque control and flux without the need to use pulse width modulation or coordinate transformation. Nevertheless, this command presents two major importunities: the switching frequency is highly variable on the one hand, and on the other hand, the amplitude of the torque and stator flux ripples remain poorly controlled throughout the considered operating speed range. The novelty of this article proposes improvements in performance of direct torque control of asynchronous machines by development of a fuzzy direct torque control algorithm. This latter makes it possible to provide solutions to the major problems of this control technique, namely: torque ripples, flux ripples, and failure to control switching frequency. Purpose. The emergence of this method has given rise to various works whose objective is to show its performance, or to provide solutions to its limitations. Indeed, this work consists in validation of a fuzzy direct torque control architecture implemented on the ML402 development kit (based on the Xilinx Virtex-4 type field programmable gate array circuit), through hardware description language (VHDL) and Xilinx generator system. The obtained results showed the robustness of the control and sensorless in front of load and parameters variation of induction motor control. The research directions of the model were determined for the subsequent implementation of results with simulation samples.

This paper presents a new adaptive hysteresis band control approach used in direct torque control (DTC) of the induction motor (IM) drives with the switching tables for the generation of PWM signals. Constant Hysteresis Direct torque control (CHB-DTC) method used the torque and stator flux errors to generate the stator voltage reference and frequency vectors for controlling the three-phase induction motor. The CHB-DTC gives better torque transient performance but it has large steady state ripples. To reduce torque and stator current ripples in CHB-DTC controlled induction motor drives a new adaptive hysteresis band control (AHB) approach is proposed, where the hysteresis band is adapted in real time with the stator flux and torque errors variation, instead of fixed bandwidth. Both classical CHB-DTC method and the proposed adaptive hysteresis band DTC (AHB-DTC) fed three induction motor have been simulated using Matlab/Simulink. The simulation results at different operating conditions over a wide speed range demonstrate the validity, effectiveness, and feasibility of the proposed scheme. The measurements showed that torque ripples were significantly decrease with the new AHB-DTC technique and better speed response in step up or down compared to the CHB-DTC.

A fast dynamic torque and high speed operations are so important especially in electric vehicle applications. In principle, there are two approaches to obtain these conditions. One is the use of mechanical gears and the other one is the use of overmodulation strategy. Through overmodulation strategy, the inverter voltage can be increased beyond its linear modulation range, thus full utilization of DC-linked voltage is achieved. This paper presents a simple overmodulation strategy that is well- suited in a constant frequency torque controller-based of direct Torque control (DTC) of induction motor drives. The simple overmodulation strategy is constructed based on torque and flux errors and flux position which are readily available; as required in conventional DTC scheme. The simulation results showed that the drive system is capable of operating in overmodulation and field weakening regions without resolving to the common approach of space vector modulation (SVM) based approach.

The traditional direct torque control (DTC) of asynchronous motor has the disadvantages of the flux linkage, large torque ripple and instable switching frequency. To solve the above problems, a new scheme of modulating direct torque control system by adaptive fuzzy PI was put forward. According to the principle of fuzzy control, the regulator can perform the real-time optimization of PI parameters, realizing the good dynamic and static performance of system. In order to verify the feasibility and effectiveness of this scheme, this paper builds a simulation model of direct torque control system based on adaptive fuzzy PI control regulator by using MATLAB and Simulink. The simulation results show that compared with the traditional direct torque control system, the direct torque control system modulated by adaptive fuzzy PI has the merits of obvious reducing in flux and torque ripple, significant improvement on control performance.

In this paper, the conventional direct torque control (DTC) scheme for induction motor drives is extended to directly control the active power (DPC) delivered to the grid by a wind turbine driven squirrel cage induction generator (SCIG). The SCIG is interfaced to the grid through an AC-AC matrix converter. A constant switching frequency based direct power control scheme with flux and power controllers is proposed. A closed loop Luenberger observer and an adaptive speed estimator are used to estimate the torque, stator flux magnitude and phase, and rotor speed of the induction generator. The simplified carrier based modulation method is used to synthesize the pulse width modulated output voltages from the matrix converter and to control the power factor of the currents on the grid side. Simulation results are presented to support the theoretical discussion.

In direct torque control of induction machines, none of the switching states is able to generate the exact voltage vector to produce the desired changes in torque and flux in most of the switching instances. This causes a high ripple in torque. This ripple can be reduced by applying a selected inverter switching state for a portion of switching period (defined as duty ratio /spl delta/) and the zero switching state for the rest of the period. The duty ratio during each switching state is a nonlinear function of torque error, flux error and flux position therefore fuzzy logic control is used to determine the duty ratio during each switching state. The simulation results indicate the ripple is reduced to less than 1/3 of the conventional DTC using the duty ratio control. Under duty ratio control the torque depends upon the changes in torque and flux during the zero switching state. These changes are minimized by using the stator flux optimization.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This paper presents a new configuration for direct torque control (DTC) of six-phase induction motor (SPIM). In the proposed method, direct torque and flux control are applied to the SPIM using matrix converter with the conventional three-phase source as its input. The new DTC scheme for SPIM benefits the advantages of both DTC and matrix converter. The simulation results show the effectiveness of the proposed method in both dynamic and steady state response.

This paper investigates the use of short voltage vectors of matrix converters to reduce the electromagnetic torque ripple which appears when direct torque control technique is used in induction motors. Direct torque control for induction motors using matrix converters is reviewed and it is pointed out the problem of the electromagnetic torque ripple which is one of the most important drawbacks of the direct torque control. The standard look up table for direct torque control, when using matrix converters, is improved in order to include the uncommonly used short voltage vectors. This novel direct torque control approach can differentiate between small and large torque errors and consequently the electromagnetic torque ripple is reduced. Finally, some results, which prove the improvement of the novel direct torque control when using small matrix converter voltage vectors, are shown.