Different STs are proposed in References [17–21] which vary according to the number of levels of the torque hysteresis controller, the inclusion of the zero voltage vectors (ZVVs), and sector boundaries. In 1997, the application of DTC in PMSM was firstly reported in Reference  using a two-level (2L) hysteresis torque controller and an ST that employs only the six active voltage vectors (AVVs) of the two-level voltage source inverter (2L-VSI). In Reference , the role of ZVVs in DTC systems of PMSM was investigated, and a DTC strategy was proposed using a three-level hysteresis torque comparator and an ST similar to the basic one which was proposed in Reference  for the induction motors (IMs). It was revealed in Reference  that the torque ripple of the DTC system can be reduced using ZVVs, because they cause torque reduction with a lower rate than that of the AVVs. A modified version of the basic ST is presented in Reference  by redefining the boundaries of the sectors where the stator flux vector is located. The main control objective of this modification was the torque ripple reduction; however, it caused a higher stator flux ripple. The effect of using ZVVs at only one state of the ST was studied in Reference , and the simulation results show that it can be beneficial for the steady-state performance and the average switching frequency. However, the dynamic response of the torque was not considered. In addition, according to the analysis of the ZVVs’ effect on the DTC of the PMSM presented in Reference , it is supposed to deteriorate when a torque reduction is commanded. Moreover, from a practical point of view, the control algorithm has to be insensitive to the direction of rotation, but the proposed ST in Reference  will not allow the motor speed reversal, as it employs ZVVs to reduce the torque and the stator flux.
In chapters III and IV, the mathematical modelling of classical DTC and SVM-DTC schemes are described. The above schemes are implemented by developing a 2.5kW PMSM. The system parameters for the surface PMSM is given in Table 5.1. In the MATLAB/Simulink model designed for directtorque and flux control, two loops are integrated: one is the stator flux loop and other is the electromagnetic or the speed loop. Here the speed loop can be called as the outer loop to the electromagnetic torque loop. The main aim of this project work is to analyse and compare the performance of the classical-DTC and the SVM-DTC for the control of the stator flux and the electromagnetic torque and to select the control-scheme which gives ripple free torque response with lower harmonics in the stator currents. For classical DTC hysteresis controllers of bandwidth1Nm and 0.02Wb for electromagnetic torque and stator flux respectively
controller , variable-structure controller , etc. However, the difficulties of obtaining the exact d-q axes reactance parameters of the Interior PermanentMagnetSynchronousMotor (IPMSM) leads to cumbersome design approach for these controllers. Furthermore, the conventional fixed-gain PI and PID controllers are very sensitive to step change of command speed, parameter variations, and load disturbance . Again, precise speed control of an IPMSM drive becomes a complex issue due to nonlinear coupling among its winding currents and the rotor speed as well as the nonlinearity present in the electromagnetic developed torque due to magnetic saturation of the rotor core . Because of these nonlinear natures of the IPMSM, an intelligent controller demands special attention for precise speed control of high-performance drive systems.
while preserving its advantages, such as simple structure and good robustness. This paper is based on , much more clear description of the two*step process is proposed, and detailed experimental results have been shown to verify the proposed method. The remainder of this paper consists of the following sections. In section 2, machine modeling and analysis based on the vector space decomposition technique is described. In section 3, basic principle of switching*table*based DTC strategy for dual* three phase drives is exposed. Then a two*step process to select the most appropriate voltage vector is presented in section 4: firstly, according to the classical switchingtable and outputs of the hysteresis regulators, selecting the voltage vector group to meet the requirement of torque and flux control, secondly, choosing the most suitable voltage vector from that group, basing on the position of the harmonic stator flux, to reduce the harmonic currents. Experimental results are provided in section 5 to demonstrate the validity of the proposed solutions.
Compared with the FOC, the major drawback of the DTC method is the large ripples of torque and flux linkage. The switching state of the inverter is updated only once in every sampling interval. The inverter keeps the same state, resulting in relatively large torque and flux ripple -. Space vector modulated directtorque control preserve transient and steady state merits, furthermore, it produce good quality steady state operating performance in a wide range, SVM technique is used to achieve the voltage space vector reference at each cycle period, to exactly compensate the errors due to flux and torque angle. The DTC – SVM torque ripple in low speed can be improved significantly -.
ABSTRACT: Industrial automation have been developed mostly the around of motion control systems in which the controlled electric motor have vital role as heart of system. So, motor control systems with a very good performance to a large extent result in optimum performance of the automation of production that this work is associated with increased production and quality of products. In fact, the performance of modern automation systems, which in terms of speed, accuracy, flexibility and performance are defined, mainly related to control strategies. Recent developments in the power electronics industry has led to a significant increase of power that can exchanged by semiconductor equipment. Despite this, most voltage supported by this equipment is a major obstacle in the applications of medium & high Voltage. Multilevel converters have been introduced for such applications. These inverters have less harmonic distortion compared with standard two-level inverters when they are working a switching frequency. Permanentmagnetsynchronous motors (PMSM) newly developed with high energy permanentmagnet materials if properly controlled can provide fast dynamic and performance with high efficiency and compatibility are very good in various applications. In spite of all these, motor control including PMSM control is a challenge due to dynamic of very fast motor and very linear models of machines. So, much of motor control development includes extraction of appropriate mathematical models. Modelling & simulation is performed on MATLAB\SIMULINK software.
Motor control 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) motor drives dominated the adjustable-speed drive market because of their excellent control performance, e.g., fast torque and speed dynamic response, and precise torque control 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 motor drives 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 motor control 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 motor drives. This makes AC motor drives more competitive in terms of performance and economy when compared with DC motor drives . Due to their wide range of uses, there are many different types of AC motor drives.
Simulation has been done using Matlab/Simulink to verify the effectiveness of proposed method. The parameters of motor are given in table.4. Simulation has been done in different situations without and with speed loops. Figure. 11 shows a case of open speed loop simulation that actual torque follows the command torque very well (Figure.11 (b)). Figure.11 (c) shows the electromagnetic torque waveform of classical DTC. As can be compared between figure 11(b) and 11(c), in the proposed DTC, electromagnetic torque follows its reference target as well as classical DTC. The average value of displacement angle of sinϕ is shown in Figure.12. It can be observed that sin ϕ is controlled such a way that to be closed to zero. Therefore unity input power factor is achieved. Triangular speed command is implemented to proposed drive in no load situation which is illustrated in Figure.13. As can be seen in this figure, motor speed tracks its reference very well. Figure.14 and Figure.15 show the characteristics of electromagnetic torque, stator flux and stator current for classic DTC and proposed DTC respectively and both in rotor speed of 600 rpm. As it is shown in these figure, in proposed method electromagnetic torque and stator flux follow their references as well as that of classical method. Electromagnetic torque reference is produced using PI controller in speed loop and stator flux reference is set to be equal to rotor permanentmagnet flux magnitude which is 0.5 Wb. As it was described in previous sections, stator current is distorted because of large magnitude of third harmonic currents. This distortion would be more if small and medium vectors of output voltage space vectors are implemented to motor. Filtered input line current and its corresponding line-to-neutral voltage are shown in Figure.16. As it can be shown, input voltage and input current are in phase as it is expected and therefore unity input power factor is achieved.
The DirectTorque Control (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 Directtorque control 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 directtorque control based space vector modulation under several topology and Speed variations.
energy recovered by the dc-bus capacitor is compared to the motor’s mechanical energy to evaluate the efficiency of the regenerative braking process. Figure 4 shows the topology of the PMSM experimental setup. The system consists of a PMSM, which is controlled using a MYWAY MWINV-9R144 inverter. The inverter switches are controlled using the dSPACE 1103 board. The PMSM is coupled with a Bühler DC Motor through flexible couplings and additional disc inertia mounted on the same shaft. The DC motor acts as a mechanical load and is controlled using a DC-DC converter, which in turn is controlled using a dSPACE 1104 board. Two encoders are used: the first is an incremental encoder directly connected to the DC motor side, and the second is a sine/cosine encoder connected to the PMSM side. The system parameters are listed in Table 1.
A lot of research has been conducted by domestic and foreign scholars on the problems existing in traditional directtorque control. Literature  introduces zero voltage vector and vector subdivision to improve the voltage vector switch table, which reduces the flux linkage and torque ripple to a certain extent. The literature  uses space vector pulse width modulation technologies to reduce the inverter. On the basis of switching frequency, many scholars combine intel- ligent control with traditional directtorque control. The literature  utilizes fuzzy control to optimize the selection of voltage space vector, but the fuzzy rules are complex and rely on experience, sliding mode variable structure. Con- trol is applicable to the directtorque control of permanentmagnetsynchronousmotor due to its robustness, rapid response, and insensitivity to external distur- bances .
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.
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. Directtorque control 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. DirectTorque Control describes the way to control torque, 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 .
DirectTorque Control (DTC) is a new control method after vector control. It abandons decoupling thought of vector control, and uses the stator flux linkage directly to control the flux linkage and the torque of motor. Thus, the dynamic response of the system is very fast . The DTC control strategy is applied for PMSM in order to improve the torque characteristics of the motor, which currently has caused the extensive attention of people. The traditional DTC usually adopts bang-bang control strategy to implement. But this control strategy cannot meet the system requirements both of torque and flux linkage at the same time, which leads to large fluctuations of flux linkage and torque generated by system and leads to the problem of pulse current and switches noise caused by higher switching frequency changes. Space Vector Pulse Width Modulation (SVPWM) control strategy has been widely used in the field of motor speed control, due to its potential advantages, such as small current waveform distortion, high utilization of DC voltage, easy-to-digital implementation, constant switching frequency of inverter, effectively to reduce pulsation of the motortorque and flux linkage, etc. The object studied in this paper is the permanentmagnetsynchronous. In application, the DTC strategy, which based on the SVPWM, is adopted to simulate. The result shows that the system has the advantage of fast response, good dynamic performance and so on  . The simulation results shows the proposed DTC-SVPWM system having less flux linkage and torque ripples while it maintains as good torque response as the DTC-SVPWM. At the same time the complexity of the power circuit does not increase.
Abstract:- Permanentmagnetsynchronous motors are mostly used in low and high power and variable speed applications. Major disadvantage of PMSM is that the motor exhibits torque pulsations due to many factors from motor and drive. This paper proposes a modified iterative learning controller to reduce the pulsations in torque of permanentmagnetsynchronous motors (PMSM). Modified ILC has memory to store previous control actions and previous error. Proposed ILC scheme consists of previous and current loop gain in order to minimize the torque oscillations. Previous control actions are stored and used to reduce the steady state periodic torque pulsations. Space vector pulse width modulation is used to reduce the harmonic noise in motor current which in turn improves performance of drive. Torque error is calculated and the i qs ref current gets altered
disadvantage, the more electric/all electric aircraft has been the development trend in the last decade. 1–3 The electrically powered actuation technology, as the key technology of the more electric/all electric aircraft, is widely applied to the ﬂight control surface actuation system and fuel pump system, which plays an important role in ﬂight safety. And extensive research work has been reported for the electrically powered actuator, which can be divided into two categories: electro-hydrostatic actuator (EHA) 4,5 and electro-mechanical actuator (EMA). 6–8 Electrical machine system is the crucial part of the electrically powered actuator and it has a critical inﬂuence on the servo-actuation system performance. As a result, as the aircraft is moving towards the developing direction with safer and
In this paper, combination of lumped parameter model, conformal mapping, and Quasi-Poissonian methods is used for accurate calculation of radial and tangential field components at the no-load condition. In the proposed method, LPM method is used for calculation of the field in the air gap of slotless stator. Then, the rotor of the IPMSM is substituted with a SPM machine rotor so that the field in the air gap remains unchanged. In the new machine (SPM), the remanent flux density, was calculated using LPM. Using the calculated of SPM machine and Poisson’s equations, the radial and tangential air gap flux density in slotless rotor is calculated. Conformal mapping is used to take slots effect into consideration. Finally, we used radial and tangential components of the no-load air gap flux density and Maxwell stress tensor and virtual work methods for predicting cogging torque. Then acquired results are compared with Finite Element Method results which shows excellent accuracy. 2. CALCULATION OF FIELD COMPONENTS
The BLDC motor is energized by three phase inverter through an Inductor – Capacitor filter for reducing the high frequency component. The capacitor voltage value has to be selected in such a way that it can charge and discharge in an effective manner to reduce the high frequency component.Fig.3.shows overall block diagram of voltage controller. The inductor- capacitor filter for the proposed work is connected in the interface of the drive and the motor. The LC filter in this system acts as a low pass filtering circuit which offer high impedance to high frequency component of the voltage and very minimum impedance to the power frequency voltage components and thereby minimizes harmonics in the supply voltage to the motor and the series inductance opposes the sudden changes in the current due to electronic commutation and thereby reduces the torque ripple.
SVPWM technique has become a popular pulse width modulation technique for three phase voltage-source inverter in the control of AC motors. It is a more sophisticated technique for generating sine wave that provides a higher voltage to the motor with lower total harmonic distortion. The main aim this technique is to obtain variable output having a maximum fundamental component with minimum harmonics. It is used for the creation of alternating current (AC) waveforms; most commonly to drive three phase AC powered motors at varying speeds from DC using multiple class-D amplifiers. There are various variations of SVM that result in different quality and computational requirements. One active area of development is in the reduction of total harmonic distortion (THD) created by the rapid switching inherent to these algorithms . Space vector modulation is based on the representation of the three phase quantities as vectors in a two-dimensional (αβ) plane. The main target of introducing SVPWM is to minimize harmonic distortion in the current by selecting the appropriate switching vectors and determining their corresponding dwelling widths -. The αβ voltages serve as inputs to SVPWM to produce the control signals to inverter.
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, torque control of the PMSM is achieved by controlling the torque current component and flux current component independently.