The switching table works on the basis of the position of the rotor also. The voltage vector plane/space is divided into six sectors with an angle difference of 60 degrees. Each vector is spanned between two active vectors. The actual voltage space vector which rotates around the space may be present in any of the sectors. To control that actual voltage the closest voltage vectors are operated. The position of actual voltage vector can be sensed or can be estimated. There are some problems with this conventional DTC scheme like high torque ripple, current harmonics, drift in flux estimator, not working properly at very low speeds. To get rid of these problems and to achieve better performance different modification from the conventional DTC is applied, discrete space vector modulation is one of them. In space vector modulation technique, the switching period or the sampling time is divided into different sub-periods according to the expected voltage. The voltage vectors operate for a desired time period to obtain the voltage of inverter. The switching frequency is kept constant only the time for voltage vector operation is changed to get the desired voltage. In this case the torque response improved and also we get a high dynamic control.
As an example, we can assume that V 1 is the VSI output voltage vector in a conventional DTC. From Figure 7 and table 2, it appears that voltage vectors (3, 5, 13, 15, 23 and 25) must be chosen. As it is illustrated in Figure.9, in each sector there are six voltage vectors. The two small vectors cannot be used for DTC method because of their change of sign in the middle of sector. If the input line-to-neutral lies in sector 1, the switching configurations which can be utilized are 3 and 5. The reason of not choosing the four other vector is that, vectors 15 and 23, are related to the small line to line voltage vectors in sector 1 ( V bc or V cb ) and cannot be used. Vectors 13 and 25 are in the opposite direction of V 1 and therefore cannot be used. Vector 3 and 5 impose two input current vectors with different directions, as shown in Figure 8. Thus, this degree of freedom can be used for controlling the input power factor. If the average value of sin( ) ψ needs to be decreased, voltage vector 5 should be chosen. On the contrary, if the average value of sin( ) ψ has to be increased, voltage vector 3 has to be applied.
The PMSM drive system utilizing Field Oriented Control (FOC) has yielded satisfactory performance in both simulation and practical implementation, with minor variation in Speed and Torque as evident in the results. The DSP’s Instruction Set Architecture (ISA) and its integrated peripherals have simplified the development of software and hardware. The real time processing capability of the DSP allows for a highly reliable drive which is able to operate efficiently under a wide range of speeds, and also offers the potentiality of implementing more advanced or complex control schemes high-performance variable speed drives. Further improvements can be realized by incorporating Space Vector PWM (SVPWM) instead of the conventional Sinusoidal PWM (SPWM) . It is also possible to implement soft computing techniques for the control algorithm although this would require sufficient knowledge to develop the hardware. It is up to the designer to choose the most optimal and viable control strategy to meet all his requirements.
In this paper, the super-spiral sliding mode variable structure control is used to design the flux linkage and torque controller. The velocity controller is designed by using the sliding film control method based on the approach law. The system designed in this paper is compared with the traditional directtorquecontrol system. It shows that the method adopted in this paper can effectively reduce the ripple of flux linkage and torque, and accelerate the speed response and an- ti-disturbance capability.
Abstract: The main theme of this paper is to present novel controller, which is a genetic based fuzzy Logic controller, for interior permanentmagnetsynchronousmotordrives with directtorquecontrol. A radial basis function network has been used for online tuning of the genetic based fuzzy logic controller. Initially different operating conditions are obtained based on motor dynamics incorporating uncertainties. At each operating condition, a genetic algorithm is used to optimize fuzzy logic parameters in closed-loop directtorquecontrol scheme. In other words, the genetic algorithm finds optimum input and output scaling factors and optimum number of membership functions. This optimization procedure is utilized to obtain the minimum speed deviation, minimum settling time, zero steady-state error. The control scheme has been verified by simulation tests with a prototype interior permanentmagnetsynchronousmotor.
In recent years PMSM have become a leading machine in the industrial applications because it has simple and rugged structure, high maintainability and economy, it is also robust and immune to heavy overloading, etc. Directtorquecontrol method is one of the newest control systems for PMSM based on vector control of electric motors . This method was invented originally for induction motor (IM) by Takahashi and Depenbrock  in 1986 and 1988 respectively, and then a lot of improvements over the proposed method have been made by other researchers for PMSM. The DTC of a PMSM motor involves the direct and independent control of the flux linkage and electromagnetic torque, by applying appropriate voltage switching vectors to the converter. DirectTorqueControl describes the way to controltorque, directly based on the electromagnetic state of the machine. DTC can be pertinent to asynchronous machines, permanentmagnet machines etc. DTC is the first technology to control the motor variables of torque and flux . Because torque and flux are motor parameters that are being directly controlled, there is no need for a modulator, as used in PWM drives, to control the frequency and voltage. A modified DTC scheme that utilizes space vector modulation (SVM)was reported in .
ABSTRACT: The principle of vector control of electrical drives is based on the control of both the magnitude and the phase of each phase current and voltage. For as long as this type of control considers the three phase system as three independent systems, the control will remain analog and thus present several drawbacks. With high computational power silicon devices, it has been possible to realize precise digital vector control algorithms. The most common is the Field Orientated Control, which demonstrates the capability of performing directtorquecontrol of handling system limitations and of achieving higher power conversion efficiency. The new families of DSPs enable cost-effective design of intelligent controllers for brushless motors which can fulfill enhanced operations, consisting of fewer system components, lower system cost and increased performances. This algorithm maintains efficiency over a wide range of speeds for a 24V, 4000 rpm PermanentMagnetSynchronousMotor and takes into consideration torque changes with transient phases by controlling the flux directly from the rotor coordinates.
In DTC, the optimum voltage space vector for the entire switching period controls the torque and flux independently and the hysteresis band maintains the errors. Only one vector is applied for the entire sampling period, in the conventional method. So, for small errors, the upper or lower torque limit may be exceeded by the motortorque. Instead, the torque ripple can be reduced by using more than one vector within the sampling period. The insertion of zero vector precisely controls the slip frequency . For a smaller hysteresis band, the frequency of operation of the PWM inverter could be very high. The width of the hysteresis band causes variation in the switching frequency. Directtorquecontrol based on space vector modulation preserve DTC transient merits, furthermore, produce better quality steady state performance in a wide speed range. At each cycle period, SVM technique is used to obtain the reference voltage space vector to exactly compensate the flux and torque errors. The torque ripple of DTC-SVM in low speed can be significantly improved.
This paper presents a feedback linearization DirectTorqueControl (DTC) based on space vector modulation (SVM) which can be noticeably reduce electromagnetic torque and stator flux ripples that affect Induction Motor (IM) drive. In this paper IM drive that utilizes feedback linearization, Sliding-Mode Control (SMC) and a Fuzzy logic speed controller is discussed. A modern feedback linearization approach is proposed, which gives a decoupled direct IM model with two state variables: torque and stator flux magnitude. This obtained linear model is utilized to implement a DTC type controller that maintains all DTC advantages and suppresses its main drawback, the flux and torque ripple. Robust, quick, and ripple free control is accomplished by utilizing SMC with proportional component in the region surrounded by the sliding surface. SMC ensures robustness as in DTC, while the proportional component wipes out the torque and flux ripple. The torque time response is similar to traditional DTC and the proposed solution is able to adjust, profoundly tunable because of the P component. The sliding controller is compared with linear DTC scheme with and without feedback linearization. The conventional scheme uses proportional integral controller to achieve speed control. The fuzzy logic controller replaces the PI speed controller in the proposed scheme to ensure fast speed response in the drive. The extensive simulation results are presented and compared with the conventional scheme.
Permanentmagnetsynchronousmotor (PMSM) is widely used in servo-actuation system for aerospace application, due to the advantages of high power density and high efﬁciency. 5,6 However, the conventional three-phase PMSM has low armature magnetic ﬁeld reconﬁguration capacity and low fault isolation capacity, which cannot operate continuously under the fault condition. In order to meet the fault tolerant require- ment of the PMSM in aerospace application, extensive research work has been reported on the fault tolerant PMSM (FTPMSM) design, which can be divided into two categories: the multiple sets of three-phase windings approach and the multiple single-phase windings approach. 4 For the multiple sets of three-phase windings approach, Bianchi et al. 7 proposed a dual three-phase PMSM, which is composed of two motors on the same shaft. Each motor is a three-phase PMSM. This FTPMSM can operate continuously with the ﬁrst open-circuit fault. In Ref. 8 , a FTPMSM with two sets of three- phase windings in the same stator is proposed. This FTPMSM cannot achieve the physical isolation between two sets of three- phase windings, and it is capable of continuous operation under the ﬁrst open-circuit fault and short-circuit fault. In Ref. 9 , a FTPMSM with four sets of three-phase windings is proposed, which consists of two motors on the same shaft. Each motor is a dual three-phase FTPMSM. This FTPMSM is able to operate continuously under the second open-circuit fault without system performance degradation. But this FTPMSM cannot operate continuously under the short-circuit fault, and it costs too much volume and weight, which is intolerable for the aerospace application. For the multiple sin- gle-phase windings approach, extensive research work has been reported on the four-phase, ﬁve-phase and six-phase FTPMSM with the fractional slot and concentrated wind- ings 10–12 (for a survey, see, for example). This structure can improve the fault isolation capacity of the windings
Motorcontrol systems play an important role in the development of modern industry and society. The applications range widely from general purpose variable-speed drives, such as water pumps, wind fans and conveyors, to high-performance drives, e.g., robotics, CNC machines and electric vehicles. In the last century, for a long time, direct-current (DC) motordrives dominated the adjustable-speed drive market because of their excellent control performance, e.g., fast torque and speed dynamic response, and precise torquecontrol in four-quadrant operations. There are two key control variables for the DC machine the excitation flux and electromagnetic torque which are naturally orthogonally decoupled so that they can be easily controlled by regulating the field and armature currents, respectively . During DC motordrives dominated the market, the advanced control theory of alternating-current (AC) machines has not been developed and there are limitations in using the semiconductor devices for variable speed drives. As the result, the market for AC motorcontrol systems was limited to undemanding applications, although AC machines have the advantages of simple structure, reliable operation, and easy maintenance. However, in recent years, the development of power electronics technology, microelectronics, and modern control theory has created favorable conditions for the development of AC motordrives. This makes AC motordrives more competitive in terms of performance and economy when compared with DC motordrives . Due to their wide range of uses, there are many different types of AC motordrives.
The conventional DTC of PMSM has received considerable investigation for its advantage of quick change of torque, robustness and simplicity . However, only six valid voltage vectors are available in conventional DTC which induce such problems as large torque ripple and variable switching frequency . Hence the space vector modulation -directtorquecontrol (SVM-DTC) was presented in which the along with hysteresis control of torque and stator flux hysteresis controller in conventional DTC, reference voltage calculator and space vector modulation unit are used. The SVM-DTC can provide constant switching frequency and more accurate Stator flux and torquecontrol.
full-order model, and the sliding mode flux observer with stator current observation error as feedback correction is constructed, which improves the robustness of the drive system. By introducing “active flux”, the structure of the observer is simplified, and the dependence on motor parameters is reduced. In addition, the drive system adopts a DTC strategy based on space vector modulation (SVM), which can effectively reduce the torque ripple while maintaining the characteristics of rapid dynamic response of directtorquecontrol. Simulation results are presented to validate that the proposed observer can obtain accurate stator flux and torque observations at full speed range, and the motor drive system has excellent control performance.
The directtorquecontrol theory has achieved great success in the control of permanentmagnetsynchronousmotor. A DirectTorqueControl (DTC) scheme of PermanentMagnetSynchronousMotor (PMSM) is presented. Based on in-depth analysis of PMSM mathematical model in abc frame and αβ frame are established and the operation principle of DTC-SVPWM system, the relationships between the torque and fundamental components. A novel space vector pulse width modulation (SVPWM) method which has a feature of low harmonic is proposed. The proposed method is adopted to implement the directtorquecontrol (DTC) of a three-phase PMSM. A large number of simulation results show that the DTC System of PMSM has fast response and good dynamic performance. To aim at the directtorquecontrol in PMSM Drives, this paper explained the theoretical basis of the directtorquecontrol (DTC) for PMSM firstly, and then explained the difference between the applications of DTC-SVPWM and PMSM. Finally, the MATLAB/Simulink models were developed to examine the DTC- SVPWM for PMSM. The simulation results are presented in this paper.
In this study, DTC process of the permanentmagnetsynchronousmotor is explained and a simulation is constituted. It is concluded that DTC can be applied for the permanentmagnetsynchronousmotor and is reliable in a wide speed range. Especially in applications where high dynamic performance is demanded DTC has a great advantage over other control methods due to its property of fast torque response. In order to increase the performance, control period should be selected as short as possible. When the sampling interval is selected smaller, it is possible to keep the bandwidth smaller and to control the stator magnetic flux more accurately. Also it is important for the sensitivity to keep the DC voltage in certain limits. As a improvement approach, a LP filter can be added to the simulation in order to eliminate the harmonics.
The DirectTorqueControl (DTC) strategy is a kind of high performance driving technology for AC motors, due to its simple structure and ability to achieve fast response of flux and torque has attracted growing interest in recent years. DTC-SVM with PI controller Directtorquecontrol without hysteresis band can effectively reduce torque and flux ripple, DTC-SVM method can improve the system robustness and effectively improve the system dynamical performance. The DC-DC converter is used with wide range in electric vehicles to ensure the energy required for the propulsion system. The objective of this paper is to understand the lithium-ion battery compartment controlled by DC-DC converter, each of the wheels is controlled independently by using directtorquecontrol based space vector modulation under several topology and Speed variations.
now, there are many control methods have been studied to control the speed of PMSM such as adaptive control, PID control, intelligent control etc. Many conventional controls use Digital Signal Processor (DSP) in most studies. Unfortunately, DSP suffers from long time of development and exhaust resources of CPU . The novel technology of FPGA with great advantages of programmable hard-wired feature, fast computation ability, shorter design cycle, embedded processor and low power consumption and higher density on the other hand can provide an alternative solution for these issues and is more suitable for the implementation of Digital System than conventional DSPs. Vector control techniques have made possible the application of PMSM motors for high performance applications where traditionally only dc drives were applied. The vector control scheme enables the control of the PMSM in the same way as a separately excited DC motor operated with a current-regulated armature supply where then the torque is proportional to the product of armature current and the excitation flux. Similarly, torquecontrol of the PMSM is achieved by controlling the torque current component and flux current component independently.
B. Constant Frequency Torque Controller-Based of DTC A constant frequency torque controller for DTC of an induction motor drive has been proposed as in reference -  to overcome the same problem described previously. The controller is capable of producing constant switching frequency in the drive operating condition and at the same time reduced for high torque ripples. In advance, the implementation of the controller is simple and the basic drive control structure is retained as in hysteresis DTC drive. A simple structure of torque controller has been introduced to replace the conventional three-level torque hysteresis comparator that used in conventional DTC scheme. A constant switching frequency is obtained by comparing a fixed frequency of triangular carrier signals with the compensated torque error signals from the PI controller. ‘Figure 6’ shows the structure of the constant frequency torque controller used in this strategy.
In this paper, directtorquecontrol (DTC) algorithms for double star permanentmagnetsynchronous machine alimented by two inverters is described. The double star permanentmagnetsynchronous machine has two sets of three-phase stator windings spatially shifted up by an angle 0 . The double star permanentmagnetsynchronous is used in areas of high power industrial applications such as traction and naval propulsion. Because constitute an advantageous choice compared to classical synchronous machine, because of the relatively low torque produced. This machine is controlled by tree level directtorque with speed regulator PI, replaced by the sliding mode regulator to improve the results obtained. The implementation of the DTC multi-level applied to a double star permanentmagnetsynchronous machine is validated with simulated results. In this paper a method for modeling and simulation of double star permanentmagnetsynchronousmotor drive MATLAB/Simulink.
The hysteresis band has to be set large enough to limit the inverter switching frequency below a certain level that is usually determined by thermal restriction of power devices. Since the hysteresis bands are set to cope with the worst case, the system performance is inevitably degraded in a certain operating range, especially in a low speed region. In torque hysteresis controller, an elapsing time to move from lower to upper limit, and vice versa can be changed according to operating condition.