Direct Torque Control Algorithm Research Articles

Modified direct torque control algorithm for regeneration capability of IM driven electric vehicle by using hybrid energy storage system

The direct torque control (DTC) algorithm of a 3-phase voltage source inverter (VSI) has been implemented to drive induction motor (IM) for EV applications. However, the conventional DTC for IM is distressed due to large torque ripple, high current total harmonic distortion, and variable switching frequency. So, in this manuscript, a modified direct torque control (MDTC) algorithm is proposed to tackle the said challenges. A three-level hysteresis controller is proposed in modified DTC to optimize the duty ratio of the fundamental voltage vector to minimize the error between the reference and final voltage vector imposed on IM terminals. To improve the efficiency of the EVs by developing a system that uses the energy produced during regenerative braking. The proposed method recovers electric energy produced by the EV without using any additional power converter. The switching patterns allow power flow in both directions. Later, a hybrid energy storage system (HESS) is integrated to supply and store the energy in an optimal way. Extensive studies have been performed to show the efficacy of the proposed MDTC technique in IM based EV application with HESS. The key findings indicate that the proposed MDTC provides better dynamic and steady-state performance.

Simulation of a direct torque control system in the presence of winding asymmetry in induction motor

The operation of a direct torque control (DTC) system for induction motors with the possible presence of unbalanced modes in the motor windings is studied. It is shown that in the presence of asymmetric modes in the motor windings, the classical DTC algorithm becomes unstable. It is proposed to improve the DTC by taking into account the unbalance of the active resistances of the motor stator windings when determining the DTC parameters. This will make it possible to study electrodynamic processes in DTC with the possible presence of asymmetric modes in the windings of induction motor.

An Improved Direct Predictive Torque Control for Torque Ripple and Copper Loss Reduction in SRM Drive

This paper introduces a direct predictive torque control (DPTC) method to minimize the torque ripple and copper loss of the switched reluctance motor (SRM). Generally, there is a problem with torque ripple during the SRM’s commutation. In this method, the commutation optimization is provided by a direct predictive torque control algorithm. Firstly, the reachable range of phase torques is predicted and the boundary of two continuous phases is modified. By dividing the torque range directly to determine the torque allocation set, the suppression of torque ripple becomes simple. Secondly, considering the optimization problem of copper loss during commutation, a cost function only related to the phase current is constructed. Further, the minimization of copper loss can be achieved by solving the cost function, and the work of setting weight parameters is not required. Finally, the proposed DPTC method is tested by simulation and experiment in a three-phase 12/8-pole SRM drive system and the results are compared with the existing predictive torque control methods. The results show that the proposed method has less torque ripple and copper loss, which effectively improves the torque control performance.

Field programmable gate array hardware in the loop validation of fuzzy direct torque control for induction machine drive

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.

Performance Improvement of DTC-SVM of PMSM with Compensation for the Dead Time Effect and Power Switch Loss Based on Extended Kalman Filter

Two algorithms have been extensively studied for motor control: Field Oriented Control (FOC) and Direct Torque Control (DTC). Both control algorithms use a Voltage Source Inverter (VSI) to drive a Permanent Magnet Synchronous Motor (PMSM). To prevent short-arm short-circuit accidents when driving PMSM using VSI, a dead time is used to turn off the TOP and BOTTOM switches of each arm at the same time. However, this dead-time technique causes an unexpected pole voltage to be applied to the PMSM on the VSI output voltage, causing distortion and resulting in control nonlinearity. The disturbance voltage that causes nonlinearity is difficult to measure directly with the sensor. Therefore, this paper analyzes the nonlinearity of the controller due to the distorted voltage caused by the dead time during PMSM operation using the DTC algorithm and predicts the distorted output voltage using the extended Kalman Filter (EKF) to improve control stability. As a result, The algorithm proposed in this paper has verified the improvement of torque ripple and stator flux ripple through experiments and simulations.

A Combined Control Scheme of Direct Torque Control and Field-Oriented Control Algorithms for Three-Phase Induction Motor: Experimental Validation

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.

Torque/Speed Control of 3PH Synchronous Reluctance Motor Using Direct Torque Control

This paper presents an investigation of the dynamic performance of the synchronous reluctance motor (SynRM) controlled by the Direct Torque Control (DTC) technique to attain either torque or speed control. The system under study comprises synchronous reluctance motor driving a mechanical load. The inner control loop of the DTC algorithm is employed to achieve torque control through the torque hysteresis comparator in which the command torque is set externally as desired. The speed control is accomplished by adding an outer control loop comprising a speed comparator and PID controller. The controller parameters are accurately tuned to provide high transient and improved dynamic performance of the motor. The SynRM model, in the d-q synchronously rotating reference frame, and the overall components of the DTC algorithm are formulated in MATLAB/Simulink. The transient and dynamic response of the SynRM controlled by DTC is investigated when the overall system is subjected to various patterns of torque and speed commands. The results confirmed that the proposed DTC technique attained a stable, fast, and robust response for both torque and speed control loops of the controlled SynRM. Furthermore, the impact of varying the controller sampling time was explored, the outcomes revealed that as the sampling time reduces, the motor dynamic performance is significantly improved.

Simulation Research on Deadbeat Direct Torque and Flux Control of Permanent Magnet Synchronous Motor

Direct torque control (DTC) is widely used in a permanent-magnet synchronous motor (PMSM), but it has its own shortcomings caused by high torque ripple. Deadbeat-direct torque and flux control (DB-DTFC) is a new torque and flux method compared with DTC. However, the traditional DB-DTFC is often based on rotor-flux-oriented control. The reference voltage of the stator is computed in a rotor-flux-oriented coordinate system, and the solution involves solving quadratic equations, which will increase the burden of computational processing. To improve the computation of the reference voltages and the control performance, this paper proposes a new DB-DTFC algorithm and introduces its basic principles. First, the proposed DB-DTFC algorithm uses the forward Euler equation to solve the reference voltage in a stator-flux-oriented coordinate system. Second, the discrete mathematical model is used to predict the next control current to achieve deadbeat control. Third, the structural model of the proposed DB-DTFC is constructed. Finally, the simulation model of the proposed DB-DTFC algorithm is built with a MATLAB/Simulink platform. The simulation results prove that the proposed DB-DTFC algorithm can achieve better control performance in torque and flux control compared with the DTC algorithm and SVM-based direct torque and flux control (SVM-DTFC) algorithm. In particular, the torque index of DB-DTFC is reduced about 6% in a limited speed range in comparison with the DTC algorithm.

Performance Enhancement of Induction Motor Based on Three-Level T-Type Inverter Using DTC-SVM

Induction motors (IM) that are driven using the conventional direct torque control algorithm (DTC) suffer from vital drawbacks which are high ripples in the torque and flux. These ripples result due to the use of a look-up table and hysteresis comparators which causes variable switching frequency. Moreover, the use of a traditional two-level inverter leads to the production of low-quality voltage and current. The work presented in this paper proposed a modified control system to overcome these drawbacks. The proposed control system is based on the use of the space vector modulation-based DTC algorithm (DTC-SVM) for driving three-phase IM via a three-level T-Type inverter. The conventional DTC-SVM algorithm has been modified to match the work of the proposed inverter. The modification process was based on the mapping of the standard DTC-SVM algorithm in the space vector of the three-level inverter. The conventional and the modified control systems are implemented using MATLAB/Simulink package. The comparison of the standard and the modified DTC-SVM has been performed by simulation. Simulation results showed the superiority of the proposed algorithm in terms of reducing ripple in torque and flux and improving the quality of current and voltage supplied to the motor.

A 12-sector space vector switching table for parallel-connecting to dual induction motors fed by matrix convertor based on direct torque control

The present study proposes an improved switching table of direct torque control (DTC) for two parallel connection induction motors fed by matrix convertor. This method is based on the mean control strategy and allows the use of all switching states of matrix convertor. These functions represent the relationship between the change rates of the torque, flux, and input power factor of motors and the output voltage vector and input current vector of the matrix convertor. The effect of matrix convertor switching states on the change rate of the torque, flux, and input power factor is established by averaging approach and is done in the four improved switching tables. Finally, the optimal switching state is chosen from the switching tables. The results show that overshoot of motors speed to following reference input is 1% of reference speed less than conventional methods and also, oscillation of motors torque is less than conventional methods. Numerical results show the effectiveness of the proposed approach and prove its reliability for industrial uses.Article HighlightsIn summary, the highlight of this research is the simultaneous control of torque and speed of two electric motors by an inverter. In such a way that even in different conditions of motors load, speed and torque follow the reference values well. Also, using the advantages of DTC algorithm and applying it to use matrix convertor are the highlights of this research.

Squirrel cage induction motor predictive direct torque control based on multi-step delay compensation

The squirrel cage induction motor direct torque control main problems due to torque and large stator flux pulsation. In this an improved model predictive direct torque control algorithm considering multi-step delay compensation is proposed. At each sampling moment, predict the stator flux linkage and torque at the next moment under each voltage vector. The optimal voltage vector deviation from the stator flux linkage reference value and torque reference value are selected as the minimum objective function. Aiming at the problem of one-shot delay in digital control systems, a multi-step predictive delay compensation measure is studied. Simulation shows that the algorithm can effectively reduce torque and stator flux pulsation, reduce current harmonic distortion, and solve the delay problem in digital systems.

Enhanced Direct Torque Control for a Three-Level T-Type Inverter

Direct torque control (DTC) is a widely used approach for motor drives due to its distinctive advantages, e.g., fast dynamic response and highly robust against motor parameters uncertainties and external disturbances. To achieve a lower torque ripple, a higher switching frequency is usually required, which, however, can reduce the drive efficiency. Using the emerging silicon carbide (SiC) devices, which can operate efficiently at a much higher switching frequency than their silicon counterparts, thus, it could be feasible to achieve high efficiency and low torque ripple simultaneously. In this work, a novel multilevel DTC for a SiC T-type inverter is proposed to significantly reduce the torque and flux ripples while retaining the fast-dynamic response. The unbalanced dc-link is a common issue of the T-type inverter, which may also lead to a higher torque ripple. To address this issue, the proposed DTC algorithm only uses the real voltage space vectors and virtual space vectors (VSVs) that do not contribute to the neutral point current such that an inherent dc-link capacitor voltage balancing can be achieved without using any active dc-link voltage controls or additional dc-link voltage and/or current sensors. The feasibility and effectiveness of proposed methods are verified by using both simulation and experimental studies.

Induction Motor Direct Torque Control with Synchronous PWM

A novel induction motor direct torque control (DTC) algorithm with synchronous modulation is presented. Compared to the traditional DTC method, whose main drawback is the presence of low-frequency torque harmonics (sub-harmonics), in the proposed method, the PWM switching frequency is imposed to be an integer multiple of the main supply frequency. This is achieved by continuously adjusting the PWM switching period to significantly reduce low-frequency harmonics. The devised algorithm has been tested on an inverter-fed induction motor drive system, and the obtained results show an important reduction of the sub-harmonic spectral content of the developed torque with respect to a conventional direct torque control while maintaining at the same time a high dynamic response.

The Operation of UAV Propulsion Motors in the Presence of High External Magnetic Fields

The operation and maintenance of converter stations (also known as valve halls) in high voltage DC (HVDC) grids is a key element in long-term, reliable and stable operation, especially in inherently adverse offshore environments. However, the nature of the electromagnetic field environment inside HVDC valve halls presents a challenge for the operation of traditional off-shelf inspection robots. In this paper, the impact of the external magnetic field on the operation of an inspection UAV’s propulsion motors is assessed. An experimental method is proposed to simulate the maximum magnetic field interference to off-shelf UAV motors, which can be used to identify their suitability for use in HVDC valve halls inspection robots. The paper’s experimental results compare the performance of direct torque control and field-oriented control algorithms for propulsion motors under the influence of external magnetic flux. Under the influence of a 177 mT external magnetic field, it was found that using direct torque control, the motor rotational velocity steady-state error was up to 55%. With field-oriented control, the steady-state error was 0%, however the peak-to-peak current draw increased by up to 567%.

A Novel Method of Electric Scooter Torque Estimation Using the Space Vector Modulation Control

In recent years, there are many studies have been conducted in the field of light electric vehicles, especially electric scooters. These are preferred in large urban areas that are crowded with cars and cause traffic congestion in the European and Asian continents. In this study, the three-wheel electric scooter contained two BLDC motors that drove the rear wheels and, each of these motors were controlled independently via an electronic differential. This paper aims to implement a Space Vector Modulation for the Direct Torque Control unit (SVM-DTC) of the BLDC wheel-motor of each driving wheel. The proposed system had been designed and simulated by using the MATLAB/SIMULINK environment. The performance of the overall system (scooter stability control system - energy storage system -power quality, etc.) with using SVM-DTC control was compared with the classical Direct Torque Control (DTC) algorithm by using the same electric scooter model. The obtained results showed clearly the improvement made by the proposed control loop system at different stages, where it could reduce the THD of the stator current from 30.99% to 6.16%,as well as it was able to achieve more than 0.2% of the charging state of the battery in 18 seconds only.

FPGA in-the-loop implementation of direct torque control for induction motor

In this study, the hysteresis based direct torque control (DTC) of a three-phase induction motor was carried out experimentally. The DTC algorithm was also modelled in the hardware environment by using FPGA’s in-the-loop feature. The dSPACE DS1103 controller board was used in the experimental study and Altera DE2-115 model development board was used in the hardware modelling. Both applications had the same sample time and all of the DTC algorithm was tested within the FPGA. The hardware simulation study conducted in FPGA environment was carried out in MATLAB/Simulink environment. The experimental results were compared with the hardware simulation results obtained from FPGA. As a result of the comparison, it was shown that DTC algorithm could be realized easily in FPGA environment without experimental installation, and the obtained current, voltage and velocity graphs were similar.

Improvements of torque ripple reduction in DTC IM drive with arbitrary number of voltage intensities and automatic algorithm modification

Techniques of direct torque control (DTC) are very common in high-performance electric motor drives.Retaining the good features of the conventional DTC and reducing torque ripple have been the subject of many years ofresearch work on improving these algorithms. This paper presents the DTC algorithm with discretized voltage vectorsbased on the use of conventional switching table (ST-DTC). This algorithm enables a significant torque ripple reductionby defining the corresponding number of the given voltage intensity while retaining calculation simplicity and fast torqueresponse typical of the ST-DTC algorithms. The proposed algorithm has the ability for its automatic modificationdepending on the defined number of voltage intensities by the user. In a simple way, the proposed algorithm enables theinfluence compensation of the induced electromotive force for a torque error at high speed. Experimental results obtainedby using MSK2812 digital control platform confirm the significant reduction of the torque ripple with an increase of thenumber of defined voltage intensities.

Robust nonlinear model predictive control for automatic train operation based on constraint tightening strategy

AbstractThis paper studies the problem of automatic train operation (ATO) robust nonlinear model predictive control under considering multiple objectives and constraints. After establishing a nonlinear multipoint model with uncertain bounded disturbance, a robust nonlinear model predictive control algorithm to meet the punctuality of train operation and energy consumption for ATO is proposed based on constraint tightening strategy. Moreover, theoretical analysis of the feasibility and stability for the speed loop system are presented. Then, with the objective of reference electromagnetic torque tracking and low switching frequency, a model predictive direct torque control algorithm with one‐step delay compensation is proposed. Feasibility of the proposed algorithm is ensured by using deadlock prediction method, and convergence analysis of the torque loop is given simultaneously. Lastly, the effectiveness of these two algorithms are verified by numerical simulation.

Study on Direct Torque Control Methods of a Doubly Fed Induction Machine Working as a Stand-Alone DC Voltage Generator

The article presents a comparison of different Direct Torque Control methods of a Stand-Alone Doubly Fed Induction DC-Voltage Generator, with classic field oriented control used as a benchmark. The system consists of a doubly fed induction generator the stator circuit of which is connected to the DC-bus with a diode rectifier, and the rotor circuit converter is connected to the same DC bus. The main problem of this power generation system are large torque oscillations caused by a nonlinear diode rectifier connected to the stator. Three direct torque control algorithms are described as a means of reduction of this drawback with simultaneous control of DC bus voltage and stator voltage frequency. The methods differ by the second variable used for control in parallel to the torque control path. The selected second variable is the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> component of the rotor current vector, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> component of the stator flux or the stator flux module.

Interrupt-Free Operation of Dual-Motor Four-Wheel Drive Electric Vehicle Under Inverter Failure

This article presents a new open-end winding induction motor (OEWIM)-based dual-motor differential four-wheel drive (D4WD) for the electric vehicle (EV). Constant speed operation through cruise control is achieved using direct torque control (DTC) algorithm. The redundant vectors are used in the switching vector selection of the DTC algorithm to achieve balanced battery currents. Fault-tolerant operation (FTO) of the drive is demonstrated, where the EV will work with full torque even if one of the inverters in rear motor drive or front motor drive or both fail. The dynamic model of the proposed drive is presented. The proposed drive and FTO are verified through simulation as per the FTP-75 driving cycle. An experimental prototype of the proposed drive is developed, and the abovementioned algorithms are verified experimentally as per the FTP-75 and HFET driving cycles. Both the simulation and experimental results are presented, and these results agree with the theoretical observations. Stable operation of EV for the entire test cycle under normal operation, as well as inverter fault conditions, is demonstrated.