Direct Torque Control

This paper presents a novel approach for the design and simulation of variable-speed drives when the control algorithm is to be implemented in an Field Programmable Gate Array (FPGA). The specialized Simulink tools used and the design procedure are presented. An ...

This paper compares two space vector techniques that can be used to regulate the instantaneous active and reactive power flow in a Power System. The first method uses the Direct Torque Control (DTC), employed frequently on speed regulation of the AC machines. The second one proposed by authors, uses the optimization of the space vector voltage in a controller bridge to reduce the least square error by controlling the instantaneous active and reactive power. These control methods have several advantages and disadvantages and are combined to improve the static and dynamic Direct Power Control (DPC) performance. The new proposed control system is no affected by harmonic distortion in the network and the obtained regulation of active and reactive power flow is practically instantaneous (< 10 ìs ) as is shown by performed simulations.

During a long time, permanent magnet synchronous motor (PMSM) were only reserved for some specific applications, however, recently, these machines are becoming more used due to the powerful magnetic characteristic of the rare earth, being used in different areas. Several researchers have proposed implementations combining the use of permanent magnet synchronous motor with the direct torque control (DTC) technique offering

The aim of this thesis is to develop a sensorless control strategy for an oscillating linear
permanent magnet synchronous motor.
The state-of-the-art sensorless methods are examined and their reliability to linear drives
is discussed. Subsequently, an adaptive sliding mode concept is chosen to estimate the
position of the mover. In the next step, the concept is implemented and simulated in
Matlab-Simulink. The results are discussed in detail.
Finally, the concept is implemented in the rapid-prototyping software X2C and evaluated
on the real plant. The results conrm the functionality of the concept for an oscillating
operation of the linear motor. The attainable accuracy of the stroke control is veried
with different levels of load. The limitations of the use of the investigated concept are shown.

— Dans cet article nous présentons la commande directe du couple (DTC) à cinq niveaux d'une machine asynchrone par les techniques de l'intelligence artificielle, la logique floue et les réseaux de neurones. Un contrôleur flou pour remplacer le contrôleur classique de la vitesse, et contrôleur neuronale pour remplacer la table de commutation. Les résultats de simulation ont montré que la commande DTC proposée présente de meilleures performances par rapport au commande DTC cinq niveaux avec et sans réseaux de neurones. Mots Clés—Commande DTC; Machine asynchrone; Onduleur NPC à cinq niveaux; Logique floue; Réseaux de neurones; THD.

This paper aims to improve the performance of conventional direct torque control (DTC) drives proposed by Takahashi by extending the idea for 5-level inverter. Hybrid cascaded H-bridge topology is used to achieve inverter voltage vector composed of 5-level of voltage. Although DTC is very popular for its simplicity but it suffers from some disadvantages like- high torque ripple and uncontrollable switching frequency. To compensate these shortcomings conventional DTC strategy is modified for five levels voltage source inverter (VSI). Multilevel hysteresis controller for both flux and torque is used. Optimal voltage vector selection from precise lookup table utilizing 12 sector, 9 torque level and 4 flux level is proposed to improve DTC performance. These voltage references are produced utilizing a hybrid cascaded H-bridge multilevel inverter, where inverter each phase can be realized using multiple dc source. Fuel cells, car batteries or ultra-capacitor are normally the choice of required dc source. Simulation results shows that the DTC drive performance is considerably improved in terms of lower torque and flux ripple and less THD. These have been experimentally evaluated and compared with the basic DTC developed by Takahashi.

Dear readers,
If you like to have the full paper, please send an email request to pejtdr_fkej@um.edu.my. We will email the paper to you. Thank You.

www.jeet.or.kr/LTKPSWeb/uploadfiles/be/201411/251120141725411097500.pdf

In this paper, a new adaptive reference based approach to direct torque control (DTC) method has been proposed for brushless direct current (BLDC) motor drives. Conventional DTC method uses two main reference parameters as: flux and torque. A main difference from the conventional method of it was that only one reference parameter (speed) was used to control the BLDC motor and the second control parameter (flux) was obtained from speed error through the proposed control algorithm. Thus, the DTC performance has been especially improved on systems which need variable speed and torque during operation, like electric vehicles. The dynamic models of the BLDC and the DTC method have been created on Matlab/Simulink. The proposed method has been confirmed and verified by the dynamic simulations on different working conditions. The simulation studies showed that the proposed method reduced remarkably the speed and the torque ripples when compared the conventional DTC method. Moreover, the proposed method has also very simple structure to apply the conventional DTC and its extra computational load to the controller is almost zero.

This paper presents direct torque control (DTC) methodology for a four-switch three-phase (FSTP) inverter-fed permanent magnet brushless ac (PM BLAC) machine, with reference to a conventional six-switch three-phase (SSTP) inverter. It has been found that when derived from conventional voltage model flux estimation scheme, the predicted stator flux imbalance may be caused by unbalanced inverter voltage drop in the FSTP inverter, in which one phase winding is directly connected to dc-link midpoint. While this imbalanced problem does not adversely affect the performance of current-model-based DTC, it causes significantly nonsinusoidal current waveforms and considerably unbalanced current magnitudes in voltage-model-based DTC. A new compensation scheme taking into account the different forward voltage-drop values in the switching device and the freewheeling diode is proposed for the voltage-model-based DTC to correct for stator flux imbalance via the addition of corrective voltages to flux equations. The proposed scheme has significantly improved the shape of current waveforms with satisfactory balanced magnitudes, total harmonic distortion, and torque ripple factor, as verified by both simulation and experimental results. It has been shown that it is possible for an FSTP inverter to provide similar performance to an SSTP inverter when driving a PM BLAC machine.

This paper proposes a sliding mode control scheme for effective speed tracking by obtaining ripple free torque through the inner loop current control for a BLDC motor. Sliding mode observer is a parameter for estimating the phase to phase trapezoidal back-EMF in sensor less mode. BLDC motor drive uses one or more sensors giving positional information to keep synchronization. Such implementation results in a higher drive cost due to sensor wiring and implementation in the motor. This project shows that the torque and speed control of three phase BLDC motors. Using sliding mode observer it is used to estimate the back EMF for sensorless operation. This project proposes, a space vector pulse width modulation(SVPWM) technique is employed to obtain the required output voltage in the line side of the inverter to control the BLDC motor speed and the same was simulated using MATLAB software.

The combination of indirect matrix converter with direct torque control is a way towards energy-saving of the world. This paper investigates the use of four-step switching in rectifier bridge of indirect matrix converters to reduce the electromagnetic torque ripple which appears when direct torque control technique is used in induction motors. By suitably selecting switching pattern, the electromagnetic torque ripple

This paper proposes a new approach to direct torque control (DTC) method for brushless direct current (BLDC) motor drives. In conventional DTC method, two main reference parameters are used as: flux and torque. In this paper, the new approach has been proposed to improve the BLDC motor dynamic performance. A main difference from the conventional method of it was that only one reference parameter (speed) was used to control the BLDC motor and the second control parameter (flux) was obtained from speed error through the proposed control algorithm. Thus, the DTC performance has been especially improved on systems which need variable speed and torque during operation, like electric vehicles. The dynamic models of the BLDC and the DTC method have been created on Matlab/Simulink. The proposed method has been confirmed and verified by the dynamic simulations on different working conditions.

Three phase induction motor is the most versatile motor used in industries. In recent years many researchers are working on making intelligent machines. This paper proposes an intelligent way of controlling a three phase induction motor by using fuzzy logic approach and it is being compared by conventional PI controller. Overall system is being simulated in MATLAB simulink environment in the proposed model direct torque control is being done by applying fuzzy technique. The result obtained after simulation shows that the response time of the system with variable speed drive is very less. Behavior of the system with variable load condition is also simulated. Result show that the system attains adaptability with variable load condition and intelligence that it response quickly to attain the desired speed. The algorithm of the system is also simple and thus it can easily be implemented in industries.

A simple hardware realization of direct torque control (DTC) scheme for fast control of induction motor torque has been presented. The proposed hardware scheme mimics the conventional switching table based DTC scheme and does not require use of any online fast computing device like microprocessor, PC or DSP. The controller uses only commonly used discrete hardware components. The experimental results of the proposed hardware implementation have been presented and supported with simulation results. Another alternate hardware scheme without using the switching table has also been proposed and the experimental results of both the schemes have been compared and found to be in agreement with each other.

Z – source inverters have been recently proposed as an alternative power conversion concept as they have both voltage buck and boost capabilities. These inverters use a unique impedance network, coupled between the power source and converter circuit, to provide both voltage buck and boost properties, which cannot be achieved with conventional voltage source and current source inverters. This paper deals with sensorless control of Z-source inverter under direct torque control to get an instantaneous torque control. Sliding mode observer is a parameter for estimating the phase to phase trapezoidal back-EMF in sensorless mode. Z-source inverter is used to boost up the voltage. The hardware results of Z-source inverter is shown.

In direct torque controlled drive system, the stator resistance of induction motor varies with operating conditions such as winding temperature. This stator resistance variation affects the stability and accurate operation at near zero speeds of the induction motor drive system. In this paper a Model Reference Adaptive System (MRAS) is proposed to estimate the stator resistance for direct torque controlled induction motor. In this estimation scheme, the error between the reference model and the adjustable model is used to drive an adaptation mechanism that estimates the stator resistance. The simulation results show the effectiveness of the stator resistance estimation.