DTC

Induction motor drives using field oriented control (FOC) for torque and flux control have been used in high performance industrial applications instead of dc motors for many years. In FOC, torque and flux of an induction motor can be controlled independently by decoupling the stator current into its orthogonal components. The FOC method has achieved a quick torque response. But in order to achieve expected performance from FOC, exact identification of parameters is required. A new torque and flux control scheme called the direct torque control (DTC) has been introduced for induction motors. In DTC the torque and flux of an induction motor can be controlled directly by applying a suitable voltage vector to the stator of an induction motor. However, convectional DTC result in large torque and flux ripples. In this paper, a controller based on fuzzy logic is designed to improve the performance of DTC and reduce the torque and flux ripple.

In this paper, the author proposes a sensorless direct torque control (DTC) of an induction motor (IM) fed by seven-level NPC inverter using artificial neural networks (ANN) and fuzzy logic controller. Fuzzy PI controller is used for controlling the rotor speed and ANN applied in switching select stator voltage. The control method proposed in this paper can reduce the torque, stator flux and total harmonic distortion (THD) value of stator current, and especially improve system good dynamic performance and robustness in high and low speeds.

Meta-heuristic optimization techniques are important tools to define the optimal solutions for many problems. In this paper, a new advanced artificial intelligence (AI) based direct torque control (DTC) speed drives are optimally designed and implemented in real time to achieve a high performance permanent-magnet synchronous-motor (PMSM) drive. Grey wolf (GW) algorithms are used with the standard PID-based DTC (PIDDTC) and with the DTC with fuzzy logic (FDTC) based speed controllers. DSPACE DS1202 is utilized in the real-time implementation. MATLAB SIMULINK is used to simulate the steady-state (S.S.) and dynamic responses. The overall system is tested at different operating conditions for both simulation and practical work and all results are presented. A comparison between experimental and simulation results is performed and also a comparison between different applied intelligent techniques is introduced.

This paper presents a VHDL design and an FPGA implementation of a direct torque controller (DTC) used to order induction machines (IM). The use of FPGA at high sampling frequency reduces the torque ripple while maintaining the classical DTC control structure. We have adopted a modular approach, by dividing the global entity into a set of elementary blocks designed and implemented separately. The performances of this command are to reduce the torque ripple to 0.01 Nm and the flux ripple to 0.01 wb with a circuit implementing DTC control of 3,256 LEs of complexity and 64 latency clock cycles. To evaluate the performance of our FPGA circuit implementing DTC controller, we have performed a co-simulation platform based on MATLAB/Simulink and Modelsim programs. MATLAB/Simulink was used to simulate the dynamics of the induction machine associated with its inverter and the proposed DTC control strategy was executed under the modelsim software using the VHDL fixed point. We have operated our...

High-performance Current Source Inverter (CSI)- fed, variable speed alternating current drives are prepared for various industrial applications. CSI-fed Induction Motor (IM) drives are managed by using different control methods. Noteworthy methods include scalar Control (V/f), Input– Output Linearization (IOL) control, Field- Oriented Control (FOC), and Direct Torque Control (DTC). The objective of this work is to compare the dynamic performance of the aforementioned drive control methods for CSI-fed IM drives. The dynamic performance results of the proposed drives are individually analyzed through sensitivity tests. The tests selected for the comparison are step changes in the reference speed and torque of the motor drive. The operation and performance of different vector control methods are verified through simulations with MATLAB/Simulink and experimental results.

In this work, Fuzzy logic control (FLC) and Genetic Algorithms (GA) techniques are used for speed control of permanent magnet synchronous motor drives to obtain high operating performance. Due to the great torque ripples on less speed conditions of PMSM when using the PI-type speed controller on conventional DTC, it is relocated using fuzzy logic controller. To overcome the entire torque ripple problems arising in the fuzzy method, Genetic Algorithm is introduced. By using this search algorithm, the error due to harmonics is reduced in a substantial amount. Simulation results show that the introduction of GA leads to an improvement in speed regulation of PMSM.

Low speed estimation in DTC IMD is not accurate due to the presence of transient offset, drift and domination of ohmic voltage drop in the measured stator voltages and currents used for estimating the stator flux required for accurate estimation of speed. EKF is a nonlinear, recursive adaptive algorithm capable of estimating speed ranging from very low speed to rated speed using equation of motion from noisy measured currents and voltages based on state space technique. In the previous work a new state space model of IM was developed for estimation in EKF by feeding load torque profile as an input variable instead of estimating it by considering load torque as constant, validated using MATLAB-Simulink software. In this paper real time validation of the EKF controller with load profile fed as input for speed estimation in DTC IMD is carried out using OPAL-RT simulator and real time results validates the simulation results and proves the effectives of the new EKF for low speed estimation in DTC IMD.

This paper presents a VHDL design and an FPGA implementation of a direct torque controller (DTC) used to order induction machines (IM). The use of FPGA at high sampling frequency reduces the torque ripple while maintaining the classical DTC control structure. We have adopted a modular approach, by dividing the global entity into a set of elementary blocks designed and implemented separately. The performances of this command are to reduce the torque ripple to 0.01 Nm and the flux ripple to 0.01 wb with a circuit implementing DTC control of 3,256 LEs of complexity and 64 latency clock cycles. To evaluate the performance of our FPGA circuit implementing DTC controller, we have performed a co-simulation platform based on MATLAB/Simulink and Modelsim programs. MATLAB/Simulink was used to simulate the dynamics of the induction machine associated with its inverter and the proposed DTC control strategy was executed under the modelsim software using the VHDL fixed point. We have operated our circuit FPGA in the loop in a speed variation platform of induction machine and we have obtained the following performances: A zero overrun, response time at speeds of 300 ms and a zero static error as required in the specifications.

Matrix converter is a good choice for Permanent Magnet Synchronous Motor (PMSM) drives, because it has high power density and does not require dc-link energy storage. the disadvantages of conventional matrix converter is using 18 active switches, so it becomes expensive and the modulation method becomes more complicated than back to back converter. To minimize this problem, this paper proposes variable speed drive of PMSM using Ultra Sparse Matrix Converter (USMC) based on Direct Torque Control (DTC) methods. This converter uses only 9 active switches, making it cheaper than conventional matrix converter. DTC is designed based on Space Vector Modulation (SVM) to reduce torque and flux ripples due to the hysteresis control in conventional DTC. The simulation results show that DTC based SVM using USMC effectively controls the rotor speed with low torque and flux ripples.

A Constant Switching Frequency Direct Torque Control (CSF-DTC) with low switching losses Space Vector modulation (SVM) for Permanent Magnet Synchronous Motor (PMSM) drive is proposed in this work. The CSF-DTC combines Field Oriented Control (FOC) and basic DTC advantages. Indeed, the proposed control strategy improves the basic DTC performances, which features low flux and torque ripples as well as a fixed switching frequency. The improved DTC ensures also a fast and robust flux and torque responses by using Integral and Proportional (IP) controllers which guaranteed a good disturbance rejection.On the other hand, a symmetrical SVM technique with low switching losses in the PWM inverter is used in order to generate the desired stator voltage vector needed to control the stator flux and the motor torque. Simulation and experimental results are presentedin this paper.These results demonstrate well the performance of the basic and proposed DTC and they show the effectiveness of the con...

This paper discusses about direct torque control of Brushless DC motor by injecting the triangular waveform and using PI controller in order to reduce the torque and obtain constant switching frequency. Brushless DC motor are widely used in applications which require wide range of speed and torque control because of robust, longer lifespan, faster torque response and able to operate at high speed. Unlike conventional three phase DTC of induction machine (IM), the proposed DTC approach introduces two phase conduction mode. Besides that, the magnitude flux is considered constant in which the results only gains from constant torque region. Thus, the flux control loop is eliminated while implement this scheme. Using the triangular waveform that will be compare with actual torque, the proper switching pattern can be selected to control the generated torque and reducing commutation torque ripple. The torque response depends on the speed of the stator flux linkage which is directly controlled by selecting appropriate voltage space vectors from a look-up table to make sure the torque error within the band. The validity of the proposed control scheme for constant switching frequency and reduce torque ripple are verified through simulation and experimental results.

Hysteresis controllers (HC) are used to limit the torque and flux in the control band in conventional configuration of direct torque control (DTC) while in the space vector pulse width modulated (SVPWM) DTC, the HC are switched to PI or PID controllers. This paper presents a modern approach for the speed control applied on a DTC of a permanent magnet synchronous motor (PMSM) using the Cuckoo Search Optimization (CSO) algorithm in order to optimize the PI speed controller parameters of the outer loop and PID flux and torque controllers of the inner loop. The system is tested at no load and with a step change in load. The performance of the controllers is presented and the results of simulation indicate a very rapid dynamic response and the system achieves the steady state (SS.) in a very short time. Also it shows that both the SS and dynamic performances are improved by applying of the CSO algorithm. The proposed DTC simulation model of the PMSM is presented using MATLAB/SIMULINK and capable of simulating both the steady-state and dynamic response. The CSO results are compared with another control strategy that incorporates fuzzy logic controller (FLC) with DTC.