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The paper presents a direct torque control method with possibilities of automatic algorithm modification in terms of torque ripple reduction. The algorithm is based on the conventional switching table with an arbitrary number of discretized voltage levels allowing higher space-voltage resolution and consequently lower torque ripple. The number of available voltage levels can be easily changed and subsequently torque ripple reduced without the need to modify the conventional switching table. Appropriate algorithm modifications leading to torque ripple reduction are automatized, making this kind of control method simple, effective, and suitable for upcoming smart drives in the rapidly growing industry 4.0. Selective back electromotive force compensation can also be part of automatization with the aim to improve the drive dynamics. Experimental validation presented in the paper confirms improvements in torque ripple reduction retaining the simple and time-effective control structure of the induction machine DTC drive. [ABSTRACT FROM AUTHOR]

The work carried out in this paper proposes an improvement of the direct torque control (DTC) of induction machine by the design of modern, robust and more efficient controllers than the conventional PI controllers commonly used for speed control. A comparative study has been carried out using five controllers, i.e. PI anti-windup, first-order sliding mode control (SMC), second order sliding mode control (SOSMC), fuzzy logic controller (Fuzzy-PI) and hybrid Fuzzy second-order sliding mode controller (FSOSMC). An advanced optimization technique based on the particle swarm optimization (PSO) algorithm has been utilized to optimize all of these controllers, the use of PSO for the determination of the different gains used in all controllers gives on the one hand a high accuracy performance and ensures on the other hand a reliable comparison between the different controllers in their optimal states. The simulation and analysis of each method with respect to robustness to disturbances was performed externally under various operating conditions and variations of the machine parameters. [ABSTRACT FROM AUTHOR]

Summary: This paper proposes a fractional‐order PI controller‐based direct torque control (DTC) scheme for an induction motor (IM). The IM drive is fed with multipoint clamped (MPC) inverter to realize the five‐level operation. The DTC scheme is implemented with the help of stator‐flux coordinates. The DTC scheme estimates the reference stator voltages from the reference speed and torque commands and space vector modulator synthesizes the reference stator voltages to generate the switching states of the inverter. The paper begins by featuring the theoretical concepts related to five‐level MPC inverter and compares it with conventional multilevel inverters in terms of total number of components required, conduction and switching power loss. In this paper, space vector modulation (SVM) algorithm for the generation of switching pulses to the five‐level MPC inverter based on fractal structure has been proposed with optimal switching sequence which further reduces the switching power loss, total inverter system loss, and phase‐current harmonic distortion. The design procedure and tuning of PI controllers (using fractional‐order system) for the proposed DTC‐SVM scheme are also presented. The proposed drive system allows full‐load torque control with fast response and reduced torque ripple for wide range of speed variations. The proposed DTC‐SVM fed IM drive is implemented in the MATLAB/Simulink software. The simulation results are verified with experimentation. [ABSTRACT FROM AUTHOR]

The conventional direct torque control (DTC) has high torque and stator flux fluctuation that causes the stator current distortion. This paper presents an efficient control method based on the feedback-linearization direct torque control (FL-DTC) method for an interior permanent magnet synchronous motor (IPMSM) drive by using an improved firefly algorithm. The proposed approach can greatly restrain the poor performance of torque and stator flux. Thus, it is suitable for IPMSM drives in electric vehicles. First, a decoupled linear model is derived to implement the proposed efficient feedback linearization control for the IPMSM. Two phase voltages in d-q axes and two additional control inputs take shape into an isomorphism mapping with the concept of orthogonal transformation. The torque generation is related to the additional control. Second, the Hamiltonian efficient control theory combined with an improved firefly algorithm is applied to obtain an analytical solution. An efficient linearization controller is designed with a cost function considering the maximum voltage of the inverter. Finally, simulation and experiment are carried out to compare the performance of the proposed efficient FL-DTC with the improved firefly algorithm and the conventional direct torque control. The results show that the proposed control method can reduce the torque and flux ripples at a steady state and maintains a good dynamic response with the variations of speed and torque. • To restrain the poor performance of torque and stator flux, this paper presents an optimal control method based on feedback-linearization direct torque control (FL-DTC) method for an interior permanent magnet synchronous motor (IPMSM) drive by using an advanced firefly algorithm. • A decoupled linear model is derived to implement the proposed optimal feedback linearization control for the IPMSM. Two phase voltages in d-q axes and two additional control inputs take shape into an isomorphism mapping with the concept of orthogonal transformation. • The Hamiltonian of optimal control theory based on an advanced firefly algorithm is applied to obtain an analytical solution. • An optimal linearization controller is designed with a cost function considering the maximum voltage of the inverter. • The proposed control method has faster torque response and smaller torque and stator flux fluctuation. [ABSTRACT FROM AUTHOR]

A robust field-weakening method for direct-torque-controlled (DTC) synchronous reluctance motors is presented in this paper. The proposed algorithm achieves smooth transition between the constant torque and field-weakening regions. Maximum torque per ampere is utilized below base speed, while both the current and voltage limits of the drive system are satisfied in the field-weakening region. The proposed method is robust to the variations in the machine dq -axis inductances. This ensures the system stability during field-weakening operation, especially along the maximum torque per flux trajectory. The proposed algorithm is incorporated into the duty ratio regulation-based DTC to achieve high-performance torque and flux control in the field-weakening region. Experimental results included in this paper confirm the veracity of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a combined structure of algorithms based on field-oriented control (FOC) and direct torque control (DTC) is proposed for improving the performance of a three-phase induction motor (IM) over a wide range of torque loads. The objective of this study is to investigate the state-of-the-art research performed on the resilient intersection control management between FOC and DTC algorithms for IM drive. Three algorithms are employed in the proposed scheme: Direct Torque Stator Flux Control (DTSFC), Direct Torque Rotor Flux Control (DTRFC), and the FOC algorithm. The main aim of the control law is to launch the drive system by selecting DTSFC or DTRFC during the transient state while FOC is switched smoothly to the steady-state. The proposed method had several advantages, including the ability to produce torque beyond the pull-out torque range at 340%, high torque dynamics during transient state within 0.5 ms, low chattering up to 0.05 N.m, and fixed frequency at steady-state operation. Furthermore, a comprehensive comparison study has been conducted, including the most recent research, to verify the effectiveness and superiority of the proposed technique. Results were obtained using both MATLAB/Simulink environment and also were experimentally performed by using a dSPACE DS1103 digital signal processing board to verify the concept of the proposed control scheme. [ABSTRACT FROM AUTHOR]

The Synchronous Reluctance Machine (SynRM) is an electrical machine in which the useful electromagnetic torque is produced due to rotor saliency. Its high power- and torque-to-mass ratio and very good efficiency make it a cheap and simple alternative for permanent magnet or induction motors, e.g. in electromobility applications. However, because of magnetic nonlinearities, the rotational speed and torque control of a SynRM is a nontrivial task. In the paper, a control algorithm based on a Hamiltonian mathematical model is presented. The model is formulated using measurement results, obtained by the drive controller. An algorithm is tested in the drive system consisting of a SynRM with the classical rotor and a fast prototyping card. The drive dynamic response in transient states is very good, but the proposed algorithm does not ensure the best efficiency after steady state angular velocity is achieved. [ABSTRACT FROM AUTHOR]

This paper presents a novel and simple hybrid space vector pulsewidth modulation (HSVPWM) method for direct torque controlled induction motor drives to reduce steady state ripples in current, torque and flux. Also, the newly developed HSVPWM technique does not use angle and sector information and hence it simplifies the control algorithm. The proposed PWM technique is designed based on the notion of stator flux ripple, which is a measure of line current ripple. Expressions for RMS ripple, over a sub-cycle are derived for each switching sequence in terms of reference voltage vector, imaginary switching times and sub-cycle duration. This analysis together with the THD performance is used to design new HSVPWM technique, which results in reduction in THD. The proposed PWM method reduces the execution time and memory required. To validate the proposed method, the simulation results are presented and compared. [ABSTRACT FROM AUTHOR]

A direct torque control (DTC) strategy for dual three-phase induction motor drives is discussed in this paper. The induction machine has two sets of stator three-phase windings spatially shifted by 30 electrical degrees. The DTC strategy is based on a predictive algorithm and is implemented in a synchronous reference frame aligned with the machine stator flux vector. The advantages of the discussed control strategy are constant inverter switching frequency, good transient and steady-state performance, and low distortion of machine currents with respect to direct self-control (DSC) and other DTC schemes with variable switching frequency. Experimental results are presented for a 10-kW DTC dual three-phase induction motor drive prototype. [ABSTRACT FROM AUTHOR]

The major drawbacks of classical direct torque control (DTC) are large torque ripples and variable switching frequency. Torque ripples in DTC drives can be attenuated if a three-level inverter is employed instead of a two-level inverter. Nevertheless, torque ripples can still be large if low switching frequencies are used. To alleviate these problems, a constant-switching-frequency-based three-level DTC (3L-DTC) algorithm is presented in this paper. Operating at low, constant switching frequency, the proposed algorithm is effective in reducing torque ripples under all operating conditions. Detailed analysis and design guidelines for the proposed 3L-DTC algorithm are presented. In addition, typical issues associated with the three-level inverter, such as neutral-point voltage fluctuations and smooth voltage vector switching, are addressed. Experimental results are presented to validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper describes the implementation of the model predictive direct torque control (MPDTC) algorithm for the control of three-phase induction motor drives comprising a three-level dc-link inverter. The MPDTC scheme is designed to keep the motor torque and stator flux and the inverter's neutral point potential within given hysteresis bounds while reducing the average switching frequency of the inverter, in comparison with the standard direct torque control (DTC) method. The algorithm is embedded in the control software environment of ABB's ACS6000 medium-voltage drive, and experimental results are provided which verify the advantageous features of MPDTC in terms of average inverter switching frequency reduction. More specifically, compared to standard DTC, the proposed MPDTC scheme achieves an average (over the whole operating range) reduction of the inverter switching frequency of 16.5%, but for specific operating conditions the reduction is as much as 37.4%. [ABSTRACT FROM AUTHOR]

In this paper, a direct torque control algorithm with novel duty cycle-based modulation is proposed for permanent magnet synchronous motor drives fed by neutral-point clamped three-level inverters. Compared with the standard DTC, the proposed algorithm can suppress steady-state torque ripples as well as ensure neutral-point potential balance and smooth vector switching. A unified torque/flux evaluation table with multiple voltage vectors and precise control levels is established and used in this method. This table can be used to evaluate the effects of duty-cycle vectors on torque and flux directly, and the elements of the table are independent of the motor parameters. Consequently, a high number of appropriate voltage vectors and their corresponding duty cycles can be selected as candidate vectors to reduce torque ripples by looking up the table. Furthermore, small vectors are incorporated into the table to ensure the neutral-point potential balance with the numerous candidate vectors. The feasibility and effectiveness of the proposed algorithm are verified by both simulations and experiments. [ABSTRACT FROM AUTHOR]

This paper presents a robust and speed-sensorless stator flux estimation for induction motor direct torque control. The proposed observer is based on sliding mode approach. Stator electrical equations are used in the rotor orientation reference frame to eliminate the observer dependence on rotor speed. Lyapunov's concept for systems stability is adopted to confine the observer gain. Furthermore, the sensitivity of the observer to parameter mismatch is recovered with an adaptation technique. The nonlinearities of the pulse width modulation voltage source inverter are estimated and compensated to enhance stability at low speeds. Therefore, a new method based on the model reference adaptive system is proposed. Simulation and experimental results are shown to verify the feasibility and effectiveness of the proposed algorithms. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a new control strategy combining the direct torque control of induction motors with the dual bridge matrix converter, and gives the modulation algorithms of dual bridge matrix converter rectifier and the method of inverter direct torque control. This control method can realize the direct torque control of induction motors with a good dynamic performance, but also get good input current waveforms and adjustable power factor. The simulation results show the validity and feasibility of the proposed control strategy. [Copyright &y& Elsevier]

Abstract: This paper describes a torque ripple reduction technique with constant switching frequency for direct torque control (DTC) of an induction motor (IM). This method enables a minimum torque ripple control. In order to obtain a constant switching frequency and hence a torque ripple reduction, we propose a control technique for IM. It consists of controlling directly the electromagnetic torque by using a modulated hysteresis controller. The design methodology is based on space vector modulation (SVM) of electrical machines with digital vector control. MATLAB simulations supported with experimental study are used. The simulation and experimental results of this proposed algorithm show an adequate dynamic to IM; however, the research can be extended to include synchronous motors as well. The implementation of the proposed algorithm is described. It doesn’t require any PI controller in the torque control loop. The hardware inverter is controlled digitally using a Texas Instruments TMS320F240 digital signal processor (DSP) with composed C codes for generating the required references. The results obtained from simulation and experiments confirmed the feasibility of the proposed strategy compared to the conventional one. [Copyright &y& Elsevier]

Switched reluctance motors (SRMs) are rugged, simple in construction and economical compared with synchronous motor and induction motor. They are known to have high-peak torque-to-inertia ratio and the rotor mechanical structure is well suited for high-speed applications. Direct torque control (DTC) is known to produce quick and robust response in AC drives. However, during steady state notable torque, flux and current pulsations occur. They are reflected in speed estimation, speed response and also in increased acoustic noise. This paper presents a novel DTC scheme where fast torque response with low ripples in the stator flux and torque of five-phase SRM drive can be achieved. In comparison with DTC of three-phase, the five-phase DT C system has more space vectors providing greater flexibility in selecting the inverter switching states, thus accomplishing a more precise control of the stator flux and torque. Simulation results clearly demonstrate that the combination of DT C with multi-phase SRM realizes higher performance with greater prospects in industries. [ABSTRACT FROM AUTHOR]

To solve the problem of complexly modeling control system in the conventional, a method for direct torque control driving system of industrial robot asynchronous motor is proposed based on MATLAB/Simulink by employing the space vector pulse width modulation (SVPWM). The structure and blocking modeling method are employed. Meanwhile, the stator flux linkage control of the principle of direct torque control (DTC) system is analyzed and improved. Finally, through MATLAB/Simulink simulation, the effectiveness of the algorithm is verified. Simulation results show that the introduction of space vector modulation combined with direct torque control (SVM_DTC) control system model achieve good control effect and make the magnetic linkage more accurate. [ABSTRACT FROM AUTHOR]

This article presents a direct torque control of doubly-fed induction generators with a space vector modulation scheme for wind energy conversion. The scheme is to independently control the torque and reactive power flow of the doubly-fed induction generator and directly compute the voltage acting on the rotor winding from the differences between reference values and feedback quantities. As the proposed algorithm is more robust and has less harmonic distortion than the hysteresis direct torque control method, the algorithm will be of great interest to fellow researchers working on doubly-fed induction generators. Computer simulation and experimental results are reported as a validation of the scheme. [ABSTRACT FROM AUTHOR]

Direct torque control (DTC) is considered one of the simplest and fastest control strategies used in motor drives. However, it produces large torque and flux ripples. Replacing the conventional two-level hysteresis torque controller (HTC) with a four-level HTC for a three-level neutral-point clamped (NPC) inverter can reduce the torque and flux ripples in interior permanent magnet synchronous motor (IPMSM) drives. However, the torque will not be controlled properly within the upper HTC bands when driving the IPMSM in the medium and high-speed regions. This problem causes the stator current to drop, resulting in poor torque control. To resolve this problem, a simple algorithm based on a torque error average calculation is proposed. Firstly, the proposed algorithm reads the information of the calculated torque and the corresponding torque reference to calculate the torque error. Secondly, the average value of torque error is calculated instantaneously as the reference torque changes. Finally, the average value of the torque error is used to indicate the operation of the proposed algorithm without the need for motor speed information. By using the proposed algorithm, the torque can be controlled well in all speed regions, and thus, a better stator current waveform can be obtained. Simulation and experimental results validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Direct torque control (DTC) is employed to minimize the influence of the cogging torque on the vibrational behavior of a PM brushless machine. Simulated and measured results, both with and without cogging torque compensation, show that DTC is effective in compensating for the influence of cogging torque provided it is taken into account in the torque estimation. The method results in a simple and effective control algorithm and significantly reduces torque ripple and vibration. [ABSTRACT FROM AUTHOR]