DTC Strategy Research Articles

An enhanced direct torque control strategy with composite controller for permanent magnet synchronous motor

AbstractDirect torque control (DTC) based on sliding mode control (SMC) has been widely applied to permanent magnet synchronous motor (PMSM) drives for torque ripple reduction and flux tracking. However, the control performance may be degraded due to disturbances such as variations in motor parameters or uncertainties. In this paper, a DTC strategy with an improved composite SMC controller is proposed for the PMSM drive system to enhance its performance under various disturbances. The speed controller is first designed based on a proposed adaptive reaching law (ARL) to eliminate chattering that appears in the conventional SMC, accelerate convergence, improve tracking performance, and reduce torque ripples. Then, an enhanced extended sliding mode disturbance observer (E2SMDO) is developed to estimate the lumped disturbances of the PMSM drive system in real time and compensate for a feedforward to the speed controller. By combining the ARL and E2SMDO, a composite controller (denoted ARL + E2SMDO) is established, whose stability is proven through the Lyapunov theory. The effectiveness of the proposed method is validated by simulations and experiments. The results of both simulations and experiments demonstrate that the composite ARL + E2SMDO controller has a fast dynamic response, reduced torque ripples, strong robustness, and good anti‐disturbance compared to other conventional methods.

Experimental verification for cost function optimization using TOPSIS approach for predictive control of surface mounted PMSM

AbstractIn this article, the selection of weight factor (WF) is improved using Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) based cost function (CF) optimization for predictive control in surface mounted permanent magnet synchronous motor (PMSM) drive under different conditions. Basically, the empirical approach used for WF is instinctive and consumes excess time. TOPSIS approach chooses a control action that is closest to the ideal control action's positive solution and farthest from its ideal control action's negative solution. Prioritizing control variables in the CF assures the choice of the best control action throughout each sampling duration. Additionally, predefined switching instants are employed for the CF optimization depending on past optimal control action, reducing the computing duration of the suggested technique. dSPACE controller is used for real‐time execution of traditional and proposed methods under steady and dynamic states. In order to verify the worth of predictive control based on TOPSIS, the hardware responses were compared with traditional DTC and predictive control strategies.

Using Feedback Control to Control Rotor Flux and Torque of the DFIG-Based Wind Power System

Direct torque control (DТС) is a method of controlling electrical machines that are widely used, and this is due to its simplicity and ease of use. However, this method has several issues, such as torque, rotor flux, and current fluctuations. To overcome these shortcomings and improve the characteristics and robustness of the DTC strategy of the doubly-fed induction generator (DFIG), a new DTC scheme based on the feedback control method (FCM) and space vector modulation (SVM) is proposed. In the proposed DTC technique, a proportional-integral controller based on feedback control theory is used to control and regulate the torque and rotor flux of the DFIG. On the other hand, the SVM technique is used to control the rotor side converter (RSC) to obtain a high-quality current. The simulation result shows that the proposed DTC technique has the advantages of faster dynamics and reduced harmonic distortion of current compared to the ‎conventional technique.‎

IM Fed by Three-Level Inverter under DTC Strategy Combined with Sliding Mode Theory

The classical direct torque control (CDTC) of the induction motor (IM) drive is characterized by high ripples in the stator flux and the electromagnetic torque waveforms due to the use of hysteresis comparators. Furthermore, the motor speed in this control strategy is ensured through a proportional integral (PI) regulator, due to its simple structure. Nonetheless, this controller is sensitive to load disturbances. Hence, it is not robust against parameter variance, which can degrade the motor performance. To overcome this deficiency, many endeavors have been conducted in the literature to ensure a high dynamic response of the motor in all speed ranges, with minimum flux and torque undulations. Thus, the DTC of an IM associated with a three-level inverter based on sliding mode (SM) flux, torque and speed controllers was adopted to substitute the hysteresis comparators and the traditional PI regulator, since the SM speed controller is able to prevail against external disturbances. The second contribution of this manuscript is to develop the proposed DTC_SM approach using the Xilinx System Generator (XSG) in order to implement it on a field programmable gate array (FPGA) Virtex 5 on account of its ability to adopt parallel processing. The hardware co-simulation results verify clearly the merits of the suggested modified DTC strategy.

Improved DTC strategy with fuzzy logic controller for induction motor driven electric vehicle

<abstract><p>In the near future, zero-emission transportation is anticipated to be implemented in an effort to reduce the major pollutants caused by road transportation. This enormous endeavor will be impossible until all modes of transport are electrified. The induction motor-fed direct torque controller is widely used for EV applications due to its fast torque response and simplicity. However, ripples in torque and flux and current harmonics are the major issues related to DTC. The fuzzy-based DTC replaces the hysteresis comparators and the switching table with fuzzy logic blocks to realize fuzzy DTC control, which improves the system's performance. This paper presents an enhanced fuzzy logic control strategy of induction motor for electric vehicle applications. The main objective is to enhance the system's performance by reducing torque and flux ripples. Both the conventional and fuzzy-based DTC are simulated with MATLAB/SIMULINK, followed by a comparative assessment to validate the effectiveness of the proposed approach for both steady-state and transient operations. The results indicate improvements in torque ripple, flux ripple, and speed ripples by 69%, 10%, and 85%, respectively. Due to the reduction in ripples, there is also an improvement in the THD of the stator current by 17%. During transient, an average improvement of integral square error for torque and speed is 8% and 12%, respectively. Further, the proposed method is validated using EUDC and HWFET drive cycles, demonstrating a reduction in battery energy demand.</p></abstract>

Amelioration Effectiveness of Torque and Rotor Flux Control Applied to the Asynchronous Generator for Dual-rotor Wind Turbine using Neural Third-order Sliding Mode Approaches

In this paper, a neural third-order sliding mode-direct torque control (NTOSM-DTC) for an asynchronous generator (AG) based dual-rotor wind turbine (DRWT) is proposed. The classical DTC strategy with traditional proportional-integral (PI) controllers has been widely applied to induction machines in recent years due to the high characteristics that it provides in comparison with the classical DTC switching technique. Meanwhile, it has a major drawback that are the significant current, rotor flux and torque ripples generated by the traditional PI controllers. To overcome these drawbacks, the improvement of this control technique by removing these controllers is designed in this paper. The proposed intelligenet nonlinear control technique is based on replacing the classical PI controllers with neural TOSM controllers which will have the same inputs as these controllers. The simulation was performed in Matlab software, and the results obtained make it possible to evaluate the characteristics of the proposed intelligenet nonlinear control technique over the traditional one.

Twelve sectors DTC strategy of IM for PV water pumping system

With the growing use of solar photovoltaic (SPV) based pumping water system in remote areas, the operating using an optimal control strategy is required. Therefore, this paper proposes an improved conventional direct torque control. The proposed control consists of controlling the system using twelve sectors switching table. Consequently, a developed look up switching table with twelve sectors is introduced. Furthermore, in order to increase the efficiency of PV system, an approach based loss minimization technique is developed. The twelve sectors DTC strategy and loss minimization technique are combined to ensure a highly-efficient and better performance of a SPV based water pumping system employing an induction motor (IM). The PV system is modeled using Matlab/Simulink software and evaluated under different operating conditions.

Comparison between PI-DTC-SPWM and fuzzy logic for a sensorless asynchronous motor drive

Currently, asynchronous cage motors are among the most commonly requested machines accentuated by their extension to the field of electric vehicles. Therefore, the development of robust and sophisticated controls for this machine is of significant interest. Artificial intelligence control techniques, such as fuzzy logic, are at the forefront of recent research. However, their design becomes much more complicated for a motor via a multilevel inverter. The main purpose of this paper is to show that it is possible to achieve fuzzy logic control of a squirrel cage asynchronous motor supplied via the usual two-level inverter. This is achieved, by adopting a DTC strategy based on a sinusoidal PWM with multilevel inverter. It employs a feedback information estimator with dual structure between the sliding mode observer at low speed and the model reference adaptive system in sliding mode at high speed. For both installations, speed is regulated using a sliding mode controller.

Improved DTC strategy of an electric vehicle with four in-wheels induction motor drive 4WDEV using fuzzy logic control

In this paper, we will study a four-wheel drive electric vehicle (4WDEV)with two control strategies: conventional direct torque control CDTC and DTC based on fuzzy logic (DTFC). Our overall idea in this work is to show that the 4WDEV equipped with four induction motors providing the drive of the driving wheels controlled by the direct fuzzy torque control ensures good stability of the 4WDEV in the different topologies of the road, bends and slopes. and increases the range of the electric vehicle. Numerical simulations were performed on an electric vehicle powered by four 15 kW induction motors integrated into the wheels using the MATLAB / Simulink environment, where the reference speeds of each wheel (front and rear) are obtained using an electronic speed differential (ESD). This can eventually cause it to synchronize the wheel speeds in any curve. The speed of each wheel is controlled by two types of PI and FLC controllers to improve stability and speed response (in terms of setpoint tracking, disturbance rejection and climb time). Simulation results show that the proposed FLC control strategy reduces torque, flux and stator current ripple. While the4WDEV range was improved throughout the driving cycle and battery power consumption was reduced.

Virtual Subspace-Based DTC Strategy for Torque Ripple Minimization in Six-Phase Induction Motors

Classical switching-table-based direct torque control (ST-DTC) of six-phase induction machine (6PIM) drives is seriously penalized by current harmonics as well as torque ripples because of uncontrolled voltage vectors in the low-impedance non-energy subspace and hysteresis torque regulator, respectively. Hence, a virtual subspace-based DTC strategy is proposed to alleviate the impact of low-order current harmonics and torque ripples. The proposed virtual subspace includes 48 virtual voltage vectors (VVs) in the $\alpha -\beta $ subspace with average volt-seconds of zero in the $z_{1}-z_{2}$ subspace, which offers full extent of freedom degrees for 6PIM fed by a two-level voltage source inverter (VSI). The increased number of VVs allows the possibility to design up to nine-level hysteresis torque regulator to minimize the torque ripples. Nevertheless, in this paper, it is found that torque ripple, current harmonics, average switching frequency, and computational burden come to a compromise with a seven-level hysteresis torque regulator. The impact of these VVs on the performance of ST-DTC is experimentally studied and some details of hardware implementation are presented. The performance of the proposed scheme is verified by simulations as well as laboratory experiments, where a complete comparison with recent schemes is made to reveal the superiority of the proposed scheme.

Comparison of Conventional and Modified Direct Torque Control of Three-Phase Induction Motor Using Three-Level Flying Capacitor Inverter

The work presented in this paper aims to compare the effectiveness of different control strategies to improve the performance of the three-phase Induction Motor (IM). The Conventional Direct Torque Control (CDTC) was employed as the first strategy for driving the IM. This control strategy causes high ripples in the IM's torque and speed due to the hysteresis comparators and a variable switching frequency due to the look-up table. A modified DTC strategy based on Space Vector Modulation (DTC-SVM) was chosen as a second strategy to enhance the performance of the IM using the two-level inverter. This method, which leads to the reduction of the torque and speed ripples and achieves constant switching frequency. As the multi-level inverter becomes most popular than the two-level inverter, the third strategy is devoted to adopting the three-level flying capacitor inverter (TLFCMLI) -based DTC-SVM. The third strategy uses the method of mapping the multi-level space vector based on basic two-level SVM. Matlab/Simulink software package is utilized to implement the suggested controllers. Simulation results show that the DTC-SVM based on TLFCMLI significantly enhances the IM's performance compared with the other two strategies from the voltage and current profiles, torque, and speed points of view.

New DTC strategy of multi-machines single-inverter systems for electric vehicle traction applications

In high power traction system applications two or more machines are fed by one converter. This topology results in a light, more compact and less costly system. These systems are called multi-machines single-converter systems. The problems posed by different electrical and mechanical couplings in these systems (MMS) affect various stages of the systems and require control strategy to reduce adverse effects. Control of multi-machines single-converter systems is the subject of this paper. The studied MMS is an electric vehicle with four in-wheel PMS motors. A three-leg inverter supplies two permanent magnet synchronous machines which are connected to the front right and rear right wheels, and another inverter supplies the left side. Several methods have been proposed for the control of multi-machines single-inverter systems, the master-slave control structure seems best adapted for our traction system. In this paper, a new control structure based on DTC method is used for the control of bi-machine traction system of an EV. This new control has been implanted in simulation to analyze its robustness in the presence of the various load cases involved in our electric vehicle traction chain. Simulation results indicated that this structure control allowed the stability of the traction system.

Controlling industrial dead-time systems: When to use a PID or an advanced controller

This work presents a comparative analysis of PID, DTC and MPC strategies when used to control SISO processes with dead time considering characteristics commonly found in industry, such as noisy measurements in the process output and modeling error. For unconstrained processes, it is shown that the performance improvement obtained by using a more advanced control strategy instead of a PID is small or nonexistent for cases which require high robustness. However, for cases with well-known process models it is shown that the improvement obtained by using a more complex control structure is justified even for small delays. For constrained processes it was demonstrated that a PID with anti-windup is able to provide similar or even better results than MPC when robust solutions are considered.

Nonlinear Direct Torque Control of Interior Permanent Magnet Synchronous Motor Drive

This paper presents a nonlinear direct torque control (NDTC) strategy of interior permanent magnet synchronous motors (IPMSMs) for electric vehicle (EV) propulsion. The proposed NDTC scheme applies a nonlinear model of IPMSM to dynamically determine the optimal switching states that optimize the EV drivers’ decision to reduce the workload. Moreover, the proposed NDTC method has a simple control structure and can explicitly handle system constraints and nonlinearities. The performance evaluation is conducted via a prototype IPMSM test-bed with a TMS320F28335 DSP. Comparative experimental results provide the evidence of improvements of the proposed NDTC strategy over the conventional DTC strategy by indicating a fast torque response and an accurate speed tracking even under rapid speed change conditions.

A novel DTC scheme for a sensorless five-phase IM drive under open-phase fault

PurposeThis paper aims to deal with direct torque controller when the five-phase induction motor drive in faulty operation. Precisely, open-phase fault condition is contemplated. Also, the DTC is combined with a speed-adaptive variable-structure observer based on sliding mode observer.Design methodology/approachTwo novel features are presented. First, the concept of the virtual voltage vector is presented, which eliminates low-frequency harmonic currents and simplifies analysis. Second, speed information is introduced into the selection of the inverter states.FindingsDirect torque control (DTC) is largely used in traditional three-phase drives as a backup to rotor-stator flux-oriented methods. The classic DTC strategy was primarily designed on the base of hysteresis controllers to control two independent variables (speed, torque and flux). Due to the additional degrees of freedom offered by multiphase machine, extensive works have been extended on the ensemble five-phase drives in healthy operation. In addition, the ability to continue the operation in faulty conditions is considering one of the main advantages of multiphase machines. One can find in the literature different approaches treating this subject. The applicability of DTC after the appearing of a fault has not been enclosed in the literature.Originality/valueTheoretical development is presented in details followed by simulation results using Matlab/Simulink to analyze the performance of the drive, comparing with the behavior during healthy situation.

Stator current and rotor flux ripples reduction of DTC DFIG drive using FSTSMC algorithm

Over the past years, many kinds of control techniques are proposed for DFIG drives. Among them, the DTC control scheme has gained more importance due to simple control schemes and fast dynamic response. However, it has the disadvantage of high ripples in stator current, rotor flux, torque, and slow response because of hysteresis controllers in torque and rotor flux loop. To improve the performance of direct torque control technique and to minimize the rotor flux and stator current ripples, DTC strategy based fuzzy super-twisting sliding mode controllers (FSTSMC) is proposed in this work. The simulation is carried out using Matlab software and compares the DTC strategy with proportional-integral (PI) controllers and the proposed control scheme is implemented and simulated results are shown.

Bus-Clamping-Based Direct Torque Control Strategy Dedicated to B6-Inverter Fed Symmetrical Two-Phase IM Drive

The paper deals with a novel DTC strategy dedicated to B6-inverter fed two-phase induction motor (2PIM) drives. It considers a bus-clamping-based approach in the synthesis of the vector selection table, leading to the “bus-clamping DTC” (BC-DTC). The study is initiated by a presentation of the B6-inverter fed 2PIM drive and a recall of the DTC background. Then, a special attention is paid to the design of the BC-DTC vector selection tables. For the sake of comparison, a conventional DTC strategy, inspired from the Takahashi one, is also considered. A simulation-based comparison of selected steady-state features is carried out. Then, a validation of the simulation results allied to an extension of the investigation is experimentally treated. The comparison is achieved by an investigation of the drive dynamic behavior under step- and ramp-shaped reversals of the reference speed. It is shown that the BC-DTC enables reductions of the switching frequency and of the torque ripple.

FPGA Implementation of a New DTC Strategy Dedicated to Delta Inverter-Fed BLDC Motor Drives

This paper presents the field programmable gate array (FPGA) implementation of an ameliorated direct torque control strategy (DTC-2) for a brushless DC motor (BLDCM) fed by a reduced delta inverter, called also three-switch three-phase inverter (TSTPI). In this work, a DTC-fed BLDCM drive is treated by considering two strategies. The first strategy (DTC-1) emulates the operation of the conventional inverter where the original DTC control is applied. Based on the DTC-1 strategy, high ripples of the electromagnetic torque are registered during the sector-to-sector commutations. These ripples are due to the application of unbalanced voltage vectors. To overcome these drawbacks, an ameliorated strategy (DTC-2) is proposed. This second strategy consists in decreasing the sudden transition between lower and upper voltage vectors by the synthesis of an appropriate vector selection table. The particularity of this table is based on the application of switching voltage vectors during a defined period of each commutation sector operation. In this paper, the two DTC strategies are developed, simulated and checked under the Xilinx system generator environment. Both strategies are translated into a hardware implementation using an FPGA device (Virtex 5). The hardware co-simulation results clearly validate the performances of the association BLDCM-TSTPI under the second ameliorated control strategy DTC-2.

Fuzzy Model Predictive Direct Torque Control of IPMSMs for Electric Vehicle Applications

This paper proposes a fuzzy model predictive direct torque control (FMP-DTC) strategy of interior permanent magnet synchronous motors (IPMSMs) for electric vehicle (EV) applications. The fuzzy logic control technique incorporated into the proposed FMP-DTC scheme dynamically determines the appropriate values of the weighting factors, and then generates the optimal switching states that minimize the electromagnetic torque and stator flux errors. Unlike the conventional model predictive (MP)-DTC strategy, the optimal switching states of the proposed FMP-DTC are selected without retuning the weighting factors. It means that they are updated depending on the specific operating conditions. Therefore, the proposed FMP-DTC is effective in various operating conditions that make it suitable for the EV-traction operating environment. Hence, the proposed FMP-DTC method has a simple control structure and can explicitly handle the system constraints. The performance evaluation is carried out via both MATLAB/Simulink and a prototype IPMSM test-bed with a TMS320F28335 digital signal processor (DSP). Comparative simulation and experimental results present the evidence of the performance improvements based on the proposed FMP-DTC strategy compared with the conventional MP-DTC strategy by indicating a fast transient torque response, low ripples, and an accurate speed tracking even under rapid climbing or emergency braking situations.

Performance Evaluation of Fuzzy DTC based PMSM for Pumping Applications

Background/Objectives: This paper presents fuzzy logic based Direct Torque Control on PMSM coupled with centrifugal pump for pumping applications and the performance evaluation of the proposed method. Methods/Statistical analysis: The proposed method is compared with the other DTC schemes such as, Conventional DTC, DTC with space vector modulation (SVM), MPDTC, DDTC and Field oriented control (FOC) for the performance evaluation. The mentioned strategy is analyzed and reviewed for centrifugal pump load under, various performance features in Mat Lab simulation. To pick the best, among all above mentioned control strategies, comparison has been done at various frequencies and speeds. Findings: It is found that the proposed DTC- FLC is having less torque ripple output among all the control strategies. Various motor control parameters analyzed are electromagnetic torque, stator current, rotor speed, stator flux etc., and pump parameters like flow rate and pressure are evaluated. Application/Improvements: The proposed DTC with FLC is having less torque ripple than existing DTC and MPDTC control strategies.