The efficiency of direct torque control for electric. I truly appreciate and value his esteemed guidance and encouragement from the beginning to the end of this report. In this case, the torque control is extended to transient states and allows better dynamic performances 5. Reduction of torque ripples cause to deliver smoother power to the wheel. Design of direct torque controller of induction motor dtc. Direct torque control describes the way in which the control of torqueand speedare directly based on the electromagnetic state of the motor,similar to a dc motor,but contrary to the way in which traditional pwm drives use input frequency and voltage. The proposed control scheme is validated trough simulation results where is shown that the predictive approach can be implemented simply with a good tracking of the torque and flux to their respective references and. In recent years vectorcontrolled ac drives have taken over from more conventional dc drives. All software and hardware is designed, manufactured and serviced in our new orleans offices, giving us.
Applications are found everywhere including machine tools, robotics, electric traction, and computer peripherals. To understand the answer to this question we have to understand that the basic function of a variable speed drive vsd is to control the flow of energy from the mains to the process. The main issue of foc drive is how to obtain the decoupled control of machine flux and torque 4. In this proposed work a modified dtc for pmsm to reduce torque ripples and flux. A new concept of control, quite different from that of the. A new technique for the torque control of induction motors was developed and presented by i. This paper presents the direct torque control using pi and fuzzy bldccontroller for minimizing torque ripples of bldc motor. Torque control is one of important factors in drive train of electric vehicle. Pdf vector control vs direct torque control comparative. Pdf direct torque control strategy of induction motors. Direct torque control an overview sciencedirect topics.
The direct torque control is one of the excellent control strategies available for torque control of induction machine. Direct torque control dtc uses a simple switching table to determine the most opportune inverter state to attain a desired output torque 1. Since there is no frictional contact between the magnets, the units have an extremely wide controllable torque range and are ideally suited for fine wire tension control. Recently the direct torque control dtc scheme is increasingly used in pmsm drive systems because of its fast torque response and possibility of eliminating the mechanical sensors if the initial rotor position is known. Direct torque control electrical engineering portal.
In this model, the on state of upper limb switches are represented by 1 and the lower limb switches are represented by 0 and the same has been defined by. A bioinspired approach to torque control in an insectsized flappingwing robot zhi ern teoh and robert j. The direct torque control technique based on space vector modulation. Torque control system explorer ii certified connection technology is the recognized leader in the manufacture, sales and service of computer operated torque control systems used in the nondestructive testing of oilfield tubular connections. Torque is independent of slip speed and can be controlled by varying the current. Toliyat this work presents the direct torque control dtc techniques, implemented in. The reference values for the flux stator modulus and the torque are. Delivering as minimum as possible ripple free torque with desired value to the wheels in various conditions, essentially increase safety and. By this method it is preserved the principle of the conventional dtc regarding the decoupled torque and flux control, while providing more flexibility for the inverter voltage utilization, in order. For me, torque control is about performing a move with an explicitly defined torque, rather considering torque just the means to the end of position or velocity control. Dtc which is a lso known as conventional dtc has features such as fast torque response, simple and robust design. While dtc and vc have different concept of operation, they both provide an effective control of the flux and torque. The dtc induction motor drive ac4 block represents an improved scalar control drive for induction motors with direct torque and flux control.
Direct torque controlled drive train for electric vehicle. Optimised direct torque control of induction motor for. Pure torque control dials in the current to feed the motor. Direct torque control, permanent magnet synchronous motor, space vector modulation 1 introduction direct torque control was introduced by i. It allows the precise and quick control of the im flux and torque without calling. By this method it is preserved the principle of the conventional dtc regarding the decoupled torque and flux control, while providing more flexibility for the inverter voltage utilization, in order to compensate the torque and flux errors. But dc motor has larger current commutation torque ripple, greatly reduce their reliability and stability. Voltage switching tables for direct torque control of pmsm drive 27 for a surface magnet motor, equation 10 becomes. The electromagnetic torque of a threephase induction motor can be written as 2, 4. Direct torque control of induction motor copy magnetic. The voltage is defined from the dcbus voltage and inverter switch positions.
Thephasecurrentiscontrolled as a square waveform in average torque control, and therefore, only turnon angle and turnoff angle can be adjusted for the given torque reference. The direct torque control dtc is the main interest of this project and it will be described in the following sections. L c n f s p 11 the angle between the stator and rotor flux linkages, noted. Direct torque control of inverterfed induction machine allows high dynamic performance by means of very simple control schemes. Project report on direct torque control of permanent magnet synchronous motor as without his constant motivation and support during my work, this would not have been possible. Direct torque control of induction motors for electric. Direct torque control technique for voltage source. The central theme of vector control v c is to decouple the stator current of the im into two orthogonal components and is to control these two components individually so as to achieve an independent control of flux and torque of the im. Among the various control techniques available direct torque control dtc appears to be very convenient for ev propulsion.
These control techn iques are in vented respectively in the 70 s and in the 80s for inductio n motor drive which are well. Direct torque control of permanent magnet synchronous motors with nonsinusoidal backemf. This model simulates direct torque control of a three phase induction motor. Sensorless vector and direct torque control peter vas. Implementation of 6 sector methodologies based direct. An indirect form of foc is also used in im drives, used in high performance applications. Assessment of direct torque control for induction motor drives. Variable frequency drive direct torque control dtc.
This paper considers the application of direct torque control, to a. Direct torque control of permanent magnet synchronous. Direct torque control technique for voltage source inverter. Novel flux and torque control of induction motor drive using four switch inverterinverter this strategy is penalized by low dynamic and high ripple of the torque. This paper considers the application of direct torque control, to a threephase bldc drive operating in the 120 conduc. When the vsd operates in torque control mode, the speed is determined by the load. The switching table block contains two lookup tables that select a specific voltage vector in accordance with the output of the flux and torque hysteresis comparators. Direct torque control of permanent magnet synchronous motor. Direct torque control principle direct torque control dtc is an optimised ac drives control principle where inverter switching directly controls the motor variables. Remember now, volts rpm, so its specifying the voltage and letting the current rip until the rpm gets to the target. A quickresponse, highefficiency control scheme is designed in this paper. Torque control dtc of a permanent magnet synchronous motor pmsm drive. Speed estimator is implemented to control of speed of motor along with the torque. Direct torque control dtc is an emerging technique for controlling pwm inverterfed induction motor im drives.
It is function of the frontal area shape protrusion such as side, mirrors, ducts and air passages spoilers and any other factor. Noguchi 1 as a new performant control strategy for induction motor drives fed by voltage source inverters vsi. Due to the good performance of brushless motor, its application is widespread. Pdf direct torque control of induction motor drives. Space vector trajectory is also plotted to observe the performance. Direct torque control system and sensorless technique of.
This book examines sensorless vectorcontrolled drives and direct torque controlled drives. The direct torque control dtc technique for a pmsm motor is receiving increasing attention due to the important advantages as the elimination of the current controllers and the low dependence on motor parameters when compared with other motor control techniques. Direct torque control scheme and indirect field oriented control scheme using space vector modulation submitted by nirupama patra, to the department of electrical engineering, national institute of technology, rourkela, in partial fulfillment of the requirements. The flux sector seeker block finds the sector of the plane in which the flux vector lies. Ndirect torque control of switched reluctance motors srms 1, 2 can be classi. Implementation of 6 sector methodologies based direct torque. Flux control is the highest level and can match dc performance such as full torque at 0 speed. Normally when you move a robot, you specify position and speed, with the robot allowed to use any and all torque up to its maximum, required to achieve those two goals. Pure speed control will feed 100% of your available torque to the motor to get it up to the requested rpm. A bioinspired approach to torque control in an insectsized.
Initially, dc motors were used as vsds because they could easily achieve the required speed and. Direct torque control of permanent magnet synchronous motors. Direct torque control dtc is one of the most excellent strategies of torque control of an induction machine. Direct torque control d tc is an improvised vc method.
Initially, dc motors were used as vsds because they could easily achieve the required speed and torque without the need for. Direct torque control of brushless dc motor using pi and. Induction motor drive control techniques are well documented in literature. The direct torque control scheme is characterized by the absence of pi regulators, coordinate transformations, current regulators and pulse width modulated signal generators.
This drive features closedloop speed control using hysteresisband torque and flux controllers. Direct torque control of a bldc motor based on computing. The torque and flux references are tracked using hysteresis controllers and a switching table implemented with lut is used for selecting the optimum converters output. Under high speed conditions such control results in commutation torque ripple.
Direct torque control for induction motor drives main features of dtc decoupled control of torque and flux absence of mechanical transducers current regulator, pwm pulse generation, pi control of flux and torque and coordinate transformation are not required very simple control scheme and low computational time. Implement direct torque and flux control dtc induction. Direct torque control using phase current reconstruction. Direct the motor torque is proportional to the armture current. Pdf improved direct torque control of induction motor. Direct torque control how is direct torque control abbreviated. The efficiency of direct torque control for electric vehicle. The speed control loop outputs the reference electromagnetic torque and stator flux of the machine. A simpler alternative to the vector control is the direct torque control dtc.
Brushless dc motor has following advantages that are low interference, low noise, high efficiency and so on, so it was widely used in industrial and control field. Direct torque control method made the motor more accurate and fast torque control, high dynamic speed response and simple to control. Dtc has been successfully applied to induction machines 10, 11, and, more recently, to blac machines 12. Fieldoriented control uses spatial vector theory to optimally control magnetic field orientation. Dec 05, 2014 heres the basic breakdown, as i understand it. Direct torque control dtc is one method used in variable frequency drives to control the torque and thus finally the speed of threephase ac electric motors. Likewise, when operated in speed control, the torque is determined by the load. Direct torque control scheme and indirect field oriented control scheme using space vector modulation submitted by nirupama patra, to the department of electrical engineering, national institute of. Initially, dc motors were used as vsds because they could easily achieve the required speed and torque without the need for sophisticated electronics.
Direct torque control dtc method proposed in 1, 2 has been utilized to drive the bldc motors. Variable speed drives vsds control information from abb the flow of energy from the mains to the process. Direct torque control of brushless dc drives with reduced. The essential differences between the dtc of bldc and blac drives are in the torque calculation. Direct torque control in ac drive technology what direct torque control dtc is, why and how it has evolved, the basic theory behind its success and the features and benefits of this new technology.
The fuzzy controller is designed to have three fuzzy state variables and one control variable for achieving direct torque control of the induction machine89, there are three variable input fuzzy logic controllers, the stator flux error, electromagnetic torque error, and. The plane is divided into six different sectors spaced by 60 degrees. According to this theory, the variations in operation frequency are obtained by the algebraic calculations from the heylandossanna circular diagram based on the torque demand feedback. Direct torque control allows a good torque control in steady state and transient operating conditions. Direct torque control dtc is used in many of the new drives. Dtc is the first technology to control the realmotor control variables of torque and flux. The main aim of direct torque control strategies is to effectively control the torque and flux of induction motor. The reason for this is due to the application of unbalanced voltage vector to control flux and torque. Direct torque control concept direct torque control has its roots in fieldoriented control and direct self control.
Direct torque control technique for voltage source inverter 631 controller imposes the time duration of the active voltage vectors, which move the stator flux along the reference trajectory, and the torque controller determinates the time duration of the zero voltage vectors which keep the motor torque in the predefined hysteresis tolerance band. The most popular is the socalled vector control technique that is now used for high impact automotive applications ev and hev. Direct torque control or dtc is the most advanced ac drive technology developed by any manufacturer in the world this manuals purpose. An offline torque sharing function for torque ripple. It offers a simple control structure, fast response, and robust operation 35. It has been successfully applied to the design of flux vector controls and is well documented. It builds on the authors popular vector control of ac drives and brings the subject fully up to. Abbs version of flux control is direct torque control dtc. Direct torque control of brushless dc motor scientific.
This involves calculating an estimate of the motors magnetic flux and torque based on the measured voltage and current of the motor. The principal of direct torque control using fuzzy logic fdtc. The measured input values to the dtc control are motor current and voltage. Direct torque control dtc for motor drive applications has been well established in both academia and industry. Oct 26, 2012 the main aim of direct torque control strategies is to effectively control the torque and flux of induction motor. Delivering as minimum as possible ripple free torque with desired value to the wheels in various conditions, essentially increase safety and efficiency of electric vehicle. Direct torque control of permanent magnet synchronous motors 1 depenbrock, 1988 presented the direct self control theory. The efficiency of direct torque control for electric vehicle behavior improvement 1 2. The method requires flux estimation and is prone to errors due to variations of stator resistance 2, 3, 4.
The reference speed which is directly applied by the pedal of the vehicle is the input of the motor controller. As it can be seen, there are two different loops corresponding to the magnitudes of the stator flux and torque. High performance direct torque control of induction motor. Faculty of engineering tobruk, faculty of engineering benha2 1, 2. Many vfd manufacturers have flux capability like gozuk and abb. By means of current and voltage measurements, it is possible to compute approximately the instantaneous stator flux and output motor torque. The control objectives are accomplished by using a prediction horizon of one sample time and a very intuitive control law.