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This manuscript presents a novel control approach for Permanent Magnet Synchronous Motors (PMSMs) by integrating the widely used Direct Torque Control (DTC) method with Deep Reinforcement Learning (DRL), specifically the Twin Delayed Deep Deterministic Policy Gradient (TD3) algorithm. The TD3 algorithm is well-suited to address the challenges posed by high-dimensional state and action spaces in PMSM drives. The conventional Proportional–Integral (PI) controller in the outer loop of DTC is replaced with the DRL based TD3 agent to overcome the limitations of traditional PI controllers, such as model dependency and complex parameter tuning. The DRL technique allows the agent to learn optimal control policies from experience, making it suitable for complex and nonlinear control problems. Extensive simulation studies demonstrate the effectiveness of the TD3-based control in achieving accurate speed tracking under varying operating conditions. Real-time experimental validation using a TMS320F28379D digital signal processor confirms the feasibility of the proposed DRL based approach. The research offers new insights into improving the performance of PMSM drives and paves the way for future advancements in electric drive control. [ABSTRACT FROM AUTHOR]

In this paper, robust predictive control (RPC) based on direct torque control space vector modulation (DTC-SVM) of the doubly fed induction generator wind turbine system (DFIG-WTS) is investigated to improve energy capture effectiveness. A novel cost function is introduced for the predictive speed regulator where the aerodynamic torque is considered as an unknown perturbation. This technique is designed to improve dynamic performance such as reference tracking, disturbance rejection, and robustness to parameter variations. The use of the DTC-SVM technique enhances performance in terms of constant switching frequency and reduced torque-flux ripples. The simulation results using real-time MATLAB/Simulink demonstrate the feasibility and validity of the proposed strategy, where very satisfactory performance has been achieved. [ABSTRACT FROM AUTHOR]

The variable DC link direct torque control (DTC) for induction motors was proposed in this paper utilizing an artificial neural network (ANN). Variable DC-link voltage is utilized as the inverter's controlling input to improve the induction motor's performance. By injecting the dynamically variable dc-link voltage, inverter switching losses are decreased and inverter efficiency is increased. Two significant limitations are the torque ripple in DTC and the speed regulation of induction motors at low speeds. The driveline of an electric vehicle is modeled, and the suggested control is put into practice to enhance low-speed speed regulation, high dynamic performance, and minimal torque ripple. With variable DC-link voltage based on ANN, an improvement in torque and speed is made possible. Additionally, the suggested strategy minimizes the current ripples. To verify the improved efficacy of the electric driveline under various operating scenarios, a proposed control of the electric driveline is implemented using MATLAB SIMULINK, and the results are compared with the conventional scheme. The recommended speeds for the three speed ranges are as follows: 300 rpm for low speed, 900 rpm for medium speed, and 1275 rpm for high speed. The torque ripples decreased from 0.39 to 0.24 in the low-speed region, 0.38 to 0.24 in the medium-speed region, and 0.36 to 0.24 in the high-speed region while the motor was operated at a constant load torque of 2 N-m. The torque ripples decreased from 0.4 to 0.274 in the low speed region, 0.4 to 0.274 in the medium speed zone, and 0.2 to 0.274 in the medium speed region when the motor operated at various speed regions with a constant load. The main effect of running the motor at different load torques, such as 1.5 N-m, 2.5 N-m, and 2.0 N-m, is shown in Table 9 and numerical data of torque ripples is presented in Table 9. [ABSTRACT FROM AUTHOR]

Control fulfilment of asynchronous motors requires accurate feedback of speed information. Previously, this function was attributed to mechanical sensors, however, due to the limited use restrictions, scientists have developed variety of speed observation algorithms. These latter are distinguished by their simplicity and sensitivity to machine parameter variations as well as their robustness even in a wide speed range. This paper proposes three new structures of observers in order to achieve an efficient behaviour at low and high speed. The first is a combined scheme of sliding mode observer and model reference adaptive system, the second consists in switching between the two aforementioned observers according to the operating speed, while the third consists in switching from sliding mode observer to the combined estimator. Moreover, the overall control scheme performance is enhanced by using sliding mode principle in a direct torque structure to control the motor fed by NPC multilevel inverter. Besides, a sliding mode controller is inserted in the external loop to regulate speed and provide a stable torque. To shed light on the efficiency of the proposed contributions, a critical and comparative study of simulation results has been conducted. [ABSTRACT FROM AUTHOR]

Since installing speed sensors on the grinding head for high-speed precision roll grinders is not feasible, it is necessary to use direct torque control (DTC) without speed sensors, and its control system requires high estimation accuracy. In this paper, speed estimation methods using extended Kalman filter (EKF) and model reference adaptive system (MRAS) have been used to realise speed estimation in the DTC system of the spindle motor of the grinding head for a high-speed precision roll grinder. The simulation results showed that the EKF method has relatively high accuracy and a fast convergence speed for the estimation speed of the spindle motor of the grinding head for a high-speed precision roll grinder by comparison with the MRAS method. Moreover, the EKF method was also able to overcome the nonlinear and parameter uncertainty of the operating system of the motor and strongly immune to the noise interference of the system. Finally, the speed estimation accuracy of the motor using the EKF method had better than the MRAS method. Therefore, this work provides a general approach to applying the DTC without speed sensors for the motor and further lays a solid foundation for developing high-speed precision roll grinders. [ABSTRACT FROM AUTHOR]

The direct torque control (DTC) of permanent magnet synchronous motor (PMSM), which includes flux and torque double closed-loops, requires constant flux and high calculation accuracy. Besides, uncertain flux estimation will cause torque ripples. To solve these problems, in this paper, twelve-sector direct torque control (DTC) without flux closed-loop for PMSM is proposed. To reduce the requirement on constant flux and high calculation accuracy and to simplify the structure of the system, the flux closed-loop is removed from the control system. To suppress the torque ripple, a twelve-sector space voltage vector control scheme is adopted which increases the switch states of the inverter. The number of nonzero voltage vectors is increased from 6 to 12 without increasing the hardware equipment of the system. The sections of the voltage vectors are redefined and the torque ripples are reduced. The hardware-in-the-loop simulation results show the effectiveness and feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

In this study, the fuzzy-based reference flux estimator (RFE), reference torque estimator (RTE) and sector rotation strategy called fuzzy logic estimator are proposed to direct torque control of induction motor (DTC-IM) drive for performance improvement. The basic DTC-IM drive with conventional RFE, RTE and sector division causes large torque ripple, variable switching frequency and uneven voltage vector contribution in stator flux. The torque and speed responses of the proposed system are investigated with load variations. The simulation results of the proposed DTC-IM drive are compared with the basic DTC-IM drive. The assessment of the proposed system shows improved performance. A hardware is developed using Xilinx Spartan-6XC6SLX45-Field Programmable Gate Array (FPGA) Kit for experimental verification of the results. Moreover, sinusoidal pulse width modulation and space vector pulse width modulation techniques are applied to reduce the torque ripples. The performance of the drive is investigated for various speed ranges. The comparison of the simulated and experimental results proves that the proposed fuzzy-based DTC-IM drive provides better performance than the basic DTC-IM drive. [ABSTRACT FROM AUTHOR]

In this paper, an improved hysteresis-switching table-based current regulation for the field-oriented control (FOC) drive is designed. The control structure of the proposed scheme is similar to the direct torque control (DTC) scheme; therefore, it is named as the hybrid torque and flux control (HTFC) scheme. Conventional HTFC strategy suffers from high current ripple, due to its inefficiency in the selection of optimised switching voltage vectors from the switching table, while limiting d- and q-axes current errors within the hysteresis bands. This is because of the restricted availability of voltage vectors for two-level inverter drive control. To overcome the above problems, the switching table of the HTFC scheme is modified to incorporate intermediate voltage vectors, based on (a) rate of change in q-axis current error, (b) the four-level hysteresis controller state of the q-axis current error, and (c) the two-level hysteresis controller state of the d-axis current error. This proposed Mutated Switching Table – HTFC (MST-HTFC) scheme intends to increase the controllability over stator current component errors, and thus limiting the current ripple. The effectiveness of the MST-HTFC scheme over the HTFC scheme is verified using a 1 kW induction motor drive in simulation through MATLAB and validated experimentally. [ABSTRACT FROM AUTHOR]

This paper deals with an adaptive direct torque control of an induction motor fed by a Z-source three-level NPC (Neutral Point Clamped) inverter. The proposed control ensures simultaneously the buck-boost operation mode and the induction motor control. Indeed, a switching table, taking into account the Z-source structure, is developed for the direct torque control. In this context, shoot-through states of the Z-source three-level NPC inverter is applied in each sampling time of the direct torque control. The proposed system can be used as promising solution in event of sags voltage, improve power factor, and reduce harmonics. Experimental tests, carried out on digital development board, clearly demonstrate the feasibility and effectiveness of the proposed control. [ABSTRACT FROM AUTHOR]

Direct Torque Control (DTC), a superior technique, which controls the stator flux and electromagnetic torque of an electrical machine. In spite of its numerous advantages, it possesses certain shortcomings like torque ripples, flux ripples, variable switching frequency and problems during the startup conditions. Recently, Matrix Converters (MC) have emerged as an efficient alternate for the Voltage Source Inverter employed in the DTC technique, which is capable of providing flexible and dynamic control over the torque and flux ripples associated in a machine. In this paper, a review on different control techniques associated in implementing the Matrix Converters for DTC method are categorized as follows: Subdivision of MC Voltage Vector method, SVM (Space Vector Modulation) based MC-DTC method, MC-DTC Duty Cycle Control, Employing Rotational Vectors of MC and Model Predictive Torque Control method. The pros and cons of each matrix converter fed direct torque control methods are presented by analyzing the experimental results from the literature. [ABSTRACT FROM AUTHOR]

The faults diagnosis of Induction Motor (IM) is a required field of the research area grown in recent years. Industrialists and researchers predominately use this interest as a result of improvement in control circuits for IM. This paper proposes a new approach for the detection of Broken Rotor Bar (BRB) fault in a three-phase Induction Motor Drive (IMD) using one of the signals Discrete Wavelet Transform (DWT), where the machine is controlled by Direct Torque Control (DTC). The amplitude and frequency components are extracted by Fast Fourier Transform (FFT), and the DWT decomposes the signal. Energy eigenvalue of stator current of the signal calculates the severity of the fault and gives a better solution for indicating the failure. DTC is adopted for advisable control techniques in the industrial drives system to preserve the excellent performance in variable torque control applications. The effectiveness of the above method is evaluated by using MATLAB/SIMULINK and experimental tests demonstrate the superior performance of the proposed technique. [ABSTRACT FROM AUTHOR]

In this paper, a five-level diode clamped inverter fed DTFC-SVM of Permanent Magnet Synchronous Motor (PMSM) drive is proposed for high power industrial applications. In Direct Torque and Flux Control with Space Vector Modulation (DTFC-SVM) technique, the speed of PMSM drive is regulated by controlling stator flux and electromagnetic torque directly and independently such that it abandons the use of direct torque control for PMSM Drive. The proposed multilevel inverter fed DTFC-SVM based PMSM drive gives very less ripples in stator flux and electromagnetic torque and also gives very less total harmonic distortion (THD) in the stator winding voltages and currents which consequences excellent dynamic and steady-state performance of drive. The five-level inverter switching pulses are designed using five-level space vector modulation (SVM) based on two-level SVM, so that it reduces the complexity of the SVM and also gives very good performance under all environmental conditions. The proposed model is simulated in MATLAB/SIMULINK software under various conditions, such as, No-load, load, reversal speed, and change in speed. In order to show the feasibility and effectiveness of the proposed model, it is also implemented in the experimental setup under various conditions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A modified fault-tolerant voltage source inverter-fed induction motor drive to maintain normal operation during open-circuit or short-circuit of power devices is proposed. The proposed inverter topology consists of a single capacitor at dc-link to eliminate the voltage-balancing issue in conventional fault-tolerant topology and a boost converter at the front end of inverter to operate the drive in full-rated condition during post-fault operation. Current control technique for boost converter and direct torque control for induction motor drive is implemented. The proposed topology reduces the stator current THD, torque and stator flux ripple when compared with the conventional fault-tolerant topology. Analysis of the proposed converter topology, modelling, simulation and experimental results are presented and also compared with the conventional fault-tolerant topology to highlight the eminence of the proposed scheme. [ABSTRACT FROM AUTHOR]

Direct torque control, model predictive control and field oriented control are control methods mostly used in high performance induction machine drives. In the direct torque control method, control variables are estimated from the stator variables, and the only parameter required is the stator resistance. The predictive torque control with horizon one has recently attracted much research attention but it requires the use of the induction machine speed, and both the stator and the rotor parameters, usually requires adjustment of the weighting factors, and has high computational burden. This paper proposes a modified predictive torque control method of induction machines. The estimated and predicted values are calculated from the stator variables, and the method uses the cost function without the weighting factor. When the two-level three-phase voltage source inverter is analyzed, it is shown that the predicted values should be calculated for three voltage vectors. The modified predictive torque control results in a better steady state performance regarding torque ripple in comparison with the conventional direct torque control and the predictive torque control methods. Simulation and experimental results for the main propulsion drive of the low-floor tram are presented in order to validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The axial field flux-switching permanent-magnet machine (AFFSPM) is one of the most efficient machines which is appropriate for high torque and low-speed direct-drive applications. In this paper, the novel axial field flux switching machine with sandwiched permanent magnet (AFFSSPM) is proposed in order to increase torque density and decrease cogging torque. The proposed model equipped with an advanced phase-group concentrated-coil winding to obtain a unity displacement winding factor. Two three-phase 6-stator-slot (S)/10-rotor-pole (P) and 12(S)/19(P) configurations of the proposed model are investigated. Some specific design issues, including the sandwiching pole angle, the stator tooth angle, and the rotor pole angle have been optimized to obtain the maximum torque density and minimum cogging torque by artificial neural network and non-sorting genetic algorithm II. Moreover, the static electromagnetic characteristics are investigated. Compared with the conventional AFFSPM and 6(S)/10(P) AFFSSPM, the 12(S)/19(P) proposed machine shows higher torque density, lower cogging torque, and higher level of fault-tolerant capability. In order to improve the dynamic performance of the AFFSSPM motor, a space vector modulation-direct torque and flux control (SVM-DTFC) scheme is proposed. The AFFSSPM motor exhibits excellent dynamic performance with proposed scheme. [ABSTRACT FROM AUTHOR]

This paper discusses about self-regulating the reference flux in induction motor (IM) direct torque control (DTC) drive by fuzzy logic. Self-regulation is improved by using "Artificial Neural Network (ANN)" and "Adaptive Network Based Fuzzy Inference System (ANFIS)" based reference flux estimators. Furthermore, PI speed controller is investigated to develop the performance of the drive. Two different PI speed controller tuning strategies, manual and Fuzzy Gain Scheduling (FGS), are compared for load torque disturbance. The results clearly show that the modified DTC of IM with "ANFIS-based reference flux estimator and FGS-tuned PI speed controller" is most suitable for torque ripple reduction and speed control. [ABSTRACT FROM AUTHOR]

The conventional direct torque control (DTC) of induction motor drive has two main problems such as higher ripple in torque, flux and variable switching frequency. These problems are mainly due to the hysteresis controllers. Appreciable reduction of torque and flux ripple can be achieved by increasing the inverter switching frequency. Most of the torque ripples reduction methods in literature are centered on this concept. The hysteresis based approach also results in variable switching frequency that depends on operating conditions at particular speed. Hence a method for increasing the switching frequency and at the same time maintaining constant switching frequency is needed. Most researches have chosen the space vector pulse width modulation based DTC (SVM-DTC) scheme. In this paper, first the torque and flux ripple in the conventional DTC method are shown and the improvement achieved by using proposed DTC method based on slip angle is presented. A new method such as slip angle control of induction motor drive based on DTC are proposed, analyzed, simulated, and tested. It is shown that this method progressively reduces torque and flux ripple. [ABSTRACT FROM PUBLISHER]

This paper introduces an effective four-level voltage switching state algorithm for direct torque controlled open end winding induction motor drive with two-two level inverters in dual mode. In the recent days, direct torque control of open end winding induction motor drive became an interesting area for researchers because it provides high dynamic performance and instantaneous control of stator flux and torque. It is more important especially in applications like propulsion and hybrid electric vehicles they require ripple free torque. The direct torque control provides high flux, torque ripple, and variable switching frequency. This paper introduces an effective voltage switching state algorithm for an open end winding induction motor drive to reduce torque and flux ripple at different frequencies of operation. The experimental results show that the proposed algorithm reduces torque and flux ripples without losing features of conventional direct torque control (DTC) algorithm and in addition it provides multi-level operation. [ABSTRACT FROM AUTHOR]

The conventional Direct Torque Control (DTC) is considered as a powerful approach which is widely used to control induction motors. However, this control approach suffers from several problems like undesirable torque and flux ripples and stator resistance variations, especially at low speed. To overcome these problems, a Variable Structure Control associated with a DTC based on Space Vector Modulation (VSC-DTC-SVM) is proposed in this paper to reduce ripples and enhance the system robustness. Due to the complex scheme of the suggested VSC-DTC-SVM approach, its implementation on software solutions such as microcontrollers and digital signal processors requires a high sampling period. In fact, this period creates delay in applying the inverter switching states which results undesirable ripples and distortions in the torque and the stator current, respectively. This delay is inevitable, and thus the VSC-DTC-SVM performances are affected and the sampling frequency is limited. These limitations in digital control are mainly caused by the calculation speed which depends on the complexity of the algorithm and the serial processing of the software solutions. To cope with this problem, a programmable digital circuit such as the FPGA is chosen to preserve the performances of the VSC-DTC-SVM in spite of its complexity, thanks to its parallel processing. To illustrate this, a hardware implementation of the VSC-DTC-SVM of an induction motor on the FPGA is presented and analyzed. The VSC-DTC-SVM performances in terms of ripples, under stator resistance variation, are presented by a theoretical study, a digital simulation and a hardware co-simulation using an FPGA Virtex 5. [ABSTRACT FROM PUBLISHER]

For the brushless doubly-fed machine (BDFM), traditional direct torque control (DTC) has many problems such as big output torque ripple and uncertain inverter switch frequency. Based on the analysis of traditional DTC, this paper proposed a new torque control which applied duty ratio modulation into direct torque control. This new control method can decrease the torque ripple effectively by adding zero voltage in each control cycle. According to the brushless BDFM state equation and the prediction of torque, flux linkage in the next moment and the theory of electromagnetic torque equals to referenced value at the instant moment in one control cycle, torque ripple can be decreased. Through theoretical analysis and experiments, the proposed control method has all advantages of traditional direct torque control and can decrease torque ripple and flux linkage ripple, which can optimize the performance of direct torque control. [ABSTRACT FROM AUTHOR]

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Direct torque control of asynchronous motors has good dynamic performance of torque and flux. However, the use of hysteresis controllers leads to a variable switching frequency. This lack of control over frequency is the origin of torque and flux ripples. To overcome these problems, this article proposes modified fuzzy direct torque control for an induction motor. In addition, a three-phase pulse width modulation rectifier controlled by the fuzzy direct power control is used. This rectifier draws a sinusoidal current from the grid and operates with a power factor close to unity. The pulse width modulation rectifier feeds the inverter of the direct torque control, ensuring a speed control loop. The proposed direct torque control–direct power control method is investigated based on theoretical analysis, computer simulation, and experimental validation that provide acceptable results. [ABSTRACT FROM AUTHOR]

This article present an application of sliding-mode control strategy to track maximum power of photovoltaic pumping system based on an induction generator with direct torque control. With the maximum power point tracking control system, it is necessary to measure the photovoltaic (PV) panel array output power and to change the duty cycle of the DC/DC converter control signal. To test the robustness of this control, we have compared the results with those obtained using the perturb and observe method. To control the stator flux and electromagnetic torque of of induction machines, the direct torque control is applied. The performance of the proposed system is validated in the MATLAB/Simulink environment (The MathWorks, Natick, Massachusetts, USA) and obtained results confirm the effectiveness of this strategy under the parameter variation environments. [ABSTRACT FROM PUBLISHER]

This document proposes an energetic output improvement of electric drives for induction motors. This modification pointing toward a better energetic output (improving the efficiency) according to the application, and can be made in the most common control algorithms as the Flux Oriented Control (FOC) and the Direct Torque Control (DTC). An on-line flux variation method is proposed depending of the load requirements, based on the measured of the consumed power and the computation of the optimal flux by an algorithm of seeking of the minimum losses; so that the output of optimal flux computed by the algorithm is the reference input for one well known control scheme (FOC, DTC). The experimental results show that the proposed controller ensures both, a good speed control and smooth torque response with current shapes with low THD, when these are compared with the conventional DTC scheme. Experimental results for a 1.1 kW induction motor are presented and analyzed using a dSpace system with DS1103 controller board based on the digital processor Texas Instruments TMS320F240. The obtained results showed that the proposed control scheme is able to obtain a high performance in some mechatronic applications (robotics, e.g.) because is able of a perfect tracking for a reference position with bounded current and torque. [ABSTRACT FROM AUTHOR]

Harmonic mitigation is a key issue in industrial as well as commercial drive applications. The wide use of non-linear loads causes significant power quality degradation in power distribution networks. The main objective of this work is to design an active front end rectifier for harmonic compensation. Active filter is used as drive front end so that it can act as a harmonic compensator and also AC to DC converter. This work proposes a dual purpose drive that can be used as a conventional drive and also to cancel out harmonics in line. Inverter in the drive is controlled by using conventional switching table based direct torque controller for induction motor control. Induction motor based on direct torque control (DTC) was implemented by connecting the inverter to the DC link of the active rectifier in order to transfer the power to induction motor through active rectifier DC link. DTC with five-level torque controller was used to minimize torque ripples. A complete simulation model is developed using MATLAB/Simulink in order to test the performance of the proposed harmonic compensator. Results shows effective harmonic compensation at front end and the current THD is 3.2% which is well below IEEE-519 Standard. The active rectifier based harmonic compensator for a DTC drive with the five-level torque controller was simulated and it was found that the torque ripples are comparably reduced with a switching table based DTC of induction motor drive. [ABSTRACT FROM PUBLISHER]

Direct torque control (DTC) technology as a high-performance control method uses stator flux to determine the direction of magnetic field and controls converter switch state through discrete two-point regulator to obtain high torque dynamic performance. But none of switch states can generate exact voltage vector to produce desired torque and flux changes in most of switch instances. This causes a high torque ripple. To solve this problem, a novel DTC strategy using fuzzy neural network (FNN) instead of hysteresis controller is proposed. Flux error, torque error and flux angle are taken as FNN variables. In order to solve nonlinear problem of parameter variation in DTC, a fuzzy adaptive speed PI regulator of analysing optimizing PI control speed response and combining experts experience is proposed. The simulation results show that control system obtains rapid speed response, stronger robustness, higher precision of speed control and small torque ripple. [ABSTRACT FROM AUTHOR]

Optimization design and direct torque control (DTC) of a flux concentrating axial flux permanent magnet motor (AFPMM) are presented in this paper, which leads the AFPMM to exhibit high torque capability at low-speed and wide speed operation range for direct driving system. Firstly design parameters and manufacturing materials which affect the output performances of the motor are discussed, and then based on finite element analysis (FEA) and response surface methodology (RSM), slot and pole number combinations, and structure dimensions are optimized. Furthermore, a novel DTC based on stator flux linkage tracking is introduced, which combines maximum torque per ampere (MTPA) control and field weakening (FW) control. Independent H-bridge inverter is used to enhance the voltage limit and enlarge the speed operation range. A prototype AFPMM is fabricated on the basis of the optimum model, and experimental measurements are conducted to verify the usefulness of the proposed optimization design and control methods. [ABSTRACT FROM AUTHOR]

Multi-machine single-inverter induction motor drives are attractive in situations in which all machines are of similar ratings and operate at approximately the same load torques. The advantages include their small size compared to multi-machine multi-inverter systems, lower weight, and overall cost. This article presents a consolidated study and comparison of vector control methods applied to multi-machine drives along with relevant simulation and experimental results. The mean control method and its modifications prove to be superior to the other control approaches. [ABSTRACT FROM AUTHOR]

The performance of sensorless induction motor drives is generally poor at extremely low speeds. The main recognized reasons are the limited accuracy of pulse-width modulation stator voltage acquisition, unwanted offset and drift components superimposed on the acquired measured signals, voltage distortions of induction motor caused by non-linear behavior of switching inverter, and finally, increased sensitivity against motor parameters mismatch. A sensorless induction drive capable of very low speed operation is presented in this article in which the principles of direct torque control and integrator backstepping non-linear control are combined to ensure high performance operation both in transient and steady state conditions. Stator flux vector is determined using a pure integrator in the stationary reference frame and is employed for rotor flux vector identification. An improved method is introduced for unavoidable offset and drift components identification and compensation. The average of stator phase voltages in each switching interval is estimated and employed in order to eliminate the AC voltage sensors. Feasible solutions are also proposed for on line stator and rotor resistances identification to ensure further improvement of drive performance at very low speeds. Effectiveness of the proposed control scheme is studied through simulation and experimental results. [ABSTRACT FROM PUBLISHER]

The combination of space-vector modulation and direct torque control is presented in this article to reduce the torque ripple contents in a medium-power adjustable speed drive system of induction motor. The drive is supplied by a five level diode-clamped inverter. The results show improvement in the torque ripple contents compared with a conventional direct torque control scheme. The experimental results of output voltage of the system for a diode-clamped multi-level inverter are also presented. [ABSTRACT FROM PUBLISHER]

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]

This article proposes a new approach for direct torque control of induction motors. This method is based on direct torque control with pulse width modulation of a current source inverter using SIMULINK/MATLAB simulators for its performance assessment. The proposed control system is realized based on stator-flux-oriented reference. It uses the same method as direct torque control drive systems with a voltage source inverter to estimate the stator flux and electromagnetic torque and, therefore, only needs the stator resistance to control the motor. In this method, stator current components are calculated to directly control the stator flux and electromagnetic torque. Simulation results show the excellent performance of this system. Using simulations, the proposed method is also compared with the direct torque control voltage source inverter system, and it is shown that the proposed method improves induction motor performance and decreases the inverter switching losses. Another main advantage of the proposed control method is that it seriously limits the starting current and feeds the motor with high power quality. A novel switching method in space vector modulation of current source inverter is also proposed, which effectively decreases motor torque ripple and harmonic losses. [ABSTRACT FROM AUTHOR]

In this paper, a sliding mode speed observer for direct torque controlled (DTC) induction motor drives is developed. The speed observer accuracy is guaranteed through the current observer. The rotor speed is estimated by the observer based on the measured and estimated stator currents. The system is firstly simulated by MATLAB and then tested by hardware in the loop. Then, the application is implemented on a TMS320C6711, 32-bit fixed point digital signal processor (DSP). The experimental results show the robustness, feasibility, and performance of the proposed observer structure. [ABSTRACT FROM AUTHOR]

This paper describes the performance of simultaneous control of torque and contactless power extraction in Salient Pole Synchronous Machine (SPSM) using Direct Torque Control (DTC). When the field windings are left unexcited, the saliency produces reluctance torque and the stator current is modulated with higher frequency component would establish induced voltages in the rotor, which could be used for supplying torque and power to rotor-mounted load. This technique eliminates slip rings in the rotating assembly. Normally, DTC technique is used to maintain constant torque only. Here, an empirical equation is derived to obtain the reference flux to produce constant torque as well as rotating secondary transformer action. The simulation results well demonstrate the effectiveness of the proposed stator flux control scheme in stationary reference frame is much faster than rotor reference frame. [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]

In direct torque control (DTC), many induction motor parameters are needed, especially those that affect the values of current and flux required in the control algorithm. DTC of induction machines presents an acceptable tracking scheme for both electromagnetic torque and stator flux. This control scheme depends only on stator measurements. The measurement of the stator flux is very difficult to achieve and can be estimated by an observer. The electromagnetic torque and the stator flux (magnitude and angle) can be determined despite their direct dependence on the knowledge of the stator resistance. This resistance can change up to 180% of its nominal value. The resistance changes with the operational conditions of the motor, such as temperature and frequency. Under these circumstances, a parameter identifier is developed to account for the resistance variations, hence establishing adaptive DTC (ADTC). Moreover, load torque represents the changing tasks required from the motor. In this article, the load torque variations are coupled with stator resistance changes, and the effectiveness of ADTC is investigated. More stable motor operations of polyphase induction motors are obtained under these uncertainties using ADTC. [ABSTRACT FROM AUTHOR]

The paper presents a modified direct torque control (DTC) method of an induction motor, which is applied in the main drive of the low-floor tramcars series TMK2200 manufactured by the Croatian consortium CROTRAM -- Končar d.d., TŽV Gredelj d.d. and ęuro ęaković d.d. The modification consists in the correction of stator flux vector by means of appropriate stator current component. Simplicity of the basic DTC is maintained because the only required machine parameter is stator resistance, yet the method enables stable operation in the whole speed range (including standstill). In comparison with other DTC schemes, the proposed method is more reliable because the rotor parameters are not used and the rotor quantities are not calculated. The method has been fully verified through exploitation of vehicles, and the simulation results are compared with the experiments on the laboratory model of the drive. [ABSTRACT FROM AUTHOR]

This paper proposes a new passive filter topology to reduce torque ripples and harmonic noises in interior permanent magnet synchronous motor (IPMSM) derived by hysteresis direct control. The filter topology consists of compound dissipative filter cascaded by RLC low pass filter. The compound filter has two tuning frequency setting points, one at inverter switching frequency and the other at some average selected frequency. The filter topology is characterized by affecting inverter switching frequency in a way that decreases stress on switching elements including dv/dt. The filter topology uses series dissipative elements to reshape motor voltage waveform to provide semi-sinusoidal voltage to the motor windings. The simulation results show that the proposed topology effectively reduces torque ripples as well as total harmonic distortion (THD) and electro-magnetic interference (EMI) noise level. [ABSTRACT FROM AUTHOR]

Direct torque control (DTC) schemes can produce quick and robust responses, but they usually behave like hysteresis controllers. Consequently, there are similar problems like non-constant switching frequencies and high torque ripple, especially when operation conditions result in low switching frequencies. In this article, the basic concept of DTC will be improved by modifying the conventional method. Problems that arise when using standard DTC methods are explained and improvements are derived to overcome these problems. Two theoretical approaches are verified and compared with standard DTC by measurements and experiments. The proposed methods provide a constant switching frequency and solve the starting problem without dither signal. Further results are a reduction of torque pulsations, as well as a new method for stator flux estimation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A brushless doubly fed reluctance machine (BDFRM) allows the use of a partially rated inverter and as such is an attractive cost-effective candidate for applications with limited speed ranges. While the Direct Torque Control (DTC) method has been successfully applied to almost all conventional AC machines, it has not been considered so far as a potential mean for controlling doubly-excited systems. This paper attempts to fill in this gap, by exploring the principles and implementation aspects of Direct Torque Control (DTC) for the BDFRM. The presented results demonstrate good controller performance over the entire supply frequency range for the maximum torque per inverter ampere control strategy. [ABSTRACT FROM AUTHOR]

Predictive Torque Control (PTC) is an acceptable alternate to Direct Torque Control (DTC) of induction motors. The limitation of classical PTC is selection of weighting factor, improper selection of weighting factors lead to distortions in current, voltage, high torque and flux ripple. In classical PTC, to reduce torque and flux ripples manual tuning of weighting factors is needed and weighting factors are selected empirically. To circumvent tedious tuning process of weighting factor, this article proposes a new self-tuned PTC algorithm to Open End Winding Induction Motor (OEWIM) drive. OEWIM’s are more popular in electric vehicles, ship propulsion but they require ripple free torque. A new self-tuned PTC algorithm is implemented to OEWIM with multi-level inversion to reduce torque and flux ripples. The effectiveness of proposed PTC algorithm was tested by applying it to multi-level inverter fed OEWIM drive through simulation and experimental verification. [ABSTRACT FROM AUTHOR]