This work investigates the **performances** of **Direct** **Torque** **Control** (DTC) of **Dual** **Stator** **Induction** **Motor** (DSIM) powered by two types of **Matrix** **Converter** (MC), namely the **direct** and **indirect** MC. To this end, the design of DTC with conventional **Direct** **Matrix** **Converter** (DMC) is firstly presented. Then, in order to illustrate the main feature of **Indirect** **Matrix** **Converter** (IMC) in terms of the output voltages and input currents waveforms, the full steps of IMC are well explained. To discuss the performance of each scheme, both techniques are simulated in the Matlab / Simulink environment for a 4.5 kW DSIM at different operating conditions. The obtained results show that the IMC provides high performance in **torque** and **flux** at different conditions and while minimization the Total Harmonic Distortion (THD) in the input current compared by the conventional DMC.

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Abstract: This paper presents a comparative study on the Predictive **Direct** **Torque** **Control** method and the **Indirect** Space Vector Modulation **Direct** **Torque** **Control** method for a Doubly-Fed **Induction** Machine (DFIM) which its rotor is fed by an **Indirect** **Matrix** **Converter** (IMC). In Conventional DTC technique, good transient and steady-state **performances** are achieved but it presents a non constant switching frequency behavior and non desirable **torque** ripples. However, in this paper by using the proposed methods, a fixed switching frequency is obtained. In this model Doubly-Fed **Induction** Machine is connected to the grid by the **stator** and the rotor is fed by an **Indirect** **Matrix** **Converter**. Functionally this **converter** is very similar to the **Direct** **Matrix** **Converter**, but it has separate line and load bridges. In the inverter stage, the Predictive method and ISVM method are employed. In the rectifier stage, in order to reduce losses caused by snubber circuits, the rectifier four- step commutation method is employed. A comparative study between the Predictive DTC and ISVM-DTC is performed by simulating these **control** systems in MATLAB/SIMULINK software environments and the obtained results are presented and verified.

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The results show the graph of rotor speed, electromagnetic **torque** and **stator** currents. Initially the speed is set at 500 rpm at time t=0 sec. We can observe that the speed is increasing in ramp fashion from initial position. After some time the speed sets at 500 rpm. After the application of load **torque** the speed of **motor** still ramps to its final value for short time. The speed is set zero at t= 1 sec. Though the value of **torque** varies the speed remain constant.

Space phasor of rotor current expressed in general reference frame Space phasor of stator current expressed in general reference frame Moment of inertia Integral gain of PI controller Pr[r]

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The basic principles of **flux** and **torque** **control** and the switching table are firstly presented in order to accomplish the DTC concept. The switching strategies as well as the influence of the **torque** and **flux** hysteresis band amplitude on the drive behaviour are then shown. A particular attention has been made on the analytical

In early 1970s, the appearance of the Field oriented **control** (FOC) allowed a considerable increase of dynamic performance of the **induction** motors [44]. Theoretically, FOC that based on Fleming's law [45] makes the **control** performance of **induction** **motor** as good as the DC motor’s where **torque** and **flux** are decoupled and hence could be controlled independently. However, during the practical practice of engineering application, the actual performance of vector **control** will be worse than predicted due to the effect of factors such as inaccurate **control** model and variable **motor** parameters [46]. Several methods are investigated to inquire into this problem and some improved techniques such as **flux** observer, rotor resistance identification are adopted in order to reduce the effect of this variation so that the **control** performance of FOC can be satisfied in most of applications [44], [45]. The **Direct** **Torque** **Control** was first introduced by Takahashi around the mid-1980s has found great success with the notion to reduce the dependence on parameters of **induction** **motor** and increase the precision and the dynamic of **flux** and **torque** response [47].

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detrimentally affects the switching operations in the comparators. It is much cleared that by decreasing the hysteresis band of **torque** and **flux** comparators, the switching frequency of the inverter can be increased and hence the **torque** and the **flux** ripple can be reduced. But even decreasing in hysteresis band for both the comparators does not increase the switching frequency of the inverter and hence does not reduce the **flux** and the **torque** ripple if the delay exists in obtaining the feedback signal. The relation between the hysteresis band of both the **torque** and the **flux** comparators and the switching frequency of the inverter is presented for DTC of three-phase **induction** **motor**. The percentage of the hysteresis band for both the comparators is compared with their rated values. For example 1% of the **torque** comparator hysteresis band reflects the magnitude of the band which is 0.13, if the rated **torque** of the three-phase **induction** machine is 13 Nm. These relations are obtained by considering the delay of 10µs and 20 µs. It is cleared from these figs that the maximum switching frequency of 20 kHz can be obtained with no delay with both the hysteresis band reduced to sufficiently low levels. In case of 10 µs delay, the maximum switching frequency of 16 kHz can be obtained whereas in case of 20 µs delay, the maximum switching frequency of 9 kHz can be obtained. In order to get the maximum possible switching frequency there should not be any delay in obtaining the feedback signal but practically it is not possible because the isolation amplifiers, Hall-effect transducer, and other related components easily bring these levels of the delay to the system in estimating the **stator** **flux** and the **torque** which makes the situation worse. Even by using broad frequency bands components, the delay cannot be avoided. These delay effect can be compensated by introducing the triangular dither signal of very high frequency may be double or triple (according to DSP limitation) the sampling frequency of the **control** scheme. This dither signal after adding to **torque** and **flux** error, increases the average switching frequency of the inverter and hence effectively reduces the **torque** and the **flux** ripple. In order to find out the first instant of switching after adding dither signal, the slope time instant relation is used. The slope time instant relation can be written as, when the dither of doubled the frequency of sampling frequency of the **control** scheme is added to the **torque** error.

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In this paper a modification of the switching table is presented and it is compared to the classic DTC. The present paper is organized as follows: Section 2 is reserved to describe the model of **dual** three phase multi-phase drive systems. A presentation of the DTC of **dual** three phase **induction** machines is given

Pabitra kumar behra, et.al, proposed a scalar **control** strategy to **control** the speed of **induction** **motor** by varying supply frequency and applied voltage by keeping (v/f) ratio as [5] constant and also presented open loop and closed loop v/f **control** of an **induction** **motor**. Madhavi L.mhaisgawali, et.al, proposed speed **control** of an **induction** **motor** by means of PID controller by using vector **control** technique and analyzed performance curves without controller and with PID controller[6]. G.Kohlrusz, et.al, distinguished scalar **control** strategy from vector **control** strategy [7] of an **induction** **motor**. And also stated that vector **control** is a complex technique, but it is commonly used in industries since scalar **control** cannot be applied to systems with dynamic behavior. Srujana dabbeti, et.al, proposed speed **control** strategy of an **induction** **motor** with predictive **torque** [8] and current controllers and without using sensors. Sandeep Goyat, et.al, suggested field orient **control** (FOC) strategy to **control** the speed [9] of an **induction** **motor** and developed FOC algorithm. D.H Choi, et.al, implemented vector **control** scheme of **induction** **motor** to **control** speed in field waning region by tuning mutual inductance [10] and rotor time constant.

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The **indirect** **matrix** **converter** (IMC) has received considerable attention as it provides a good alternative to double-sided PWM voltage source rectifier-inverter having advantage of being a two stage **converter** with six bidirectional switches and six unidirectional switches for three phase to three phase conversion and inherent bidirectional power flow, sinusoidal input/output waveforms with modulate switching frequency, the possibility of compact design due to the absence of dc-link reactive components and controllable input power factor independent of output load current. The main disadvantages of **matrix** **converter** are the inherent restriction of the voltage transfer ratio (0.866), more complex **control** and protection strategy.

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This paper presents an improved **Direct** **Torque** **Control** (DTC) of **induction** **motor**. DTC drive gives the high **torque** ripple. In DTC **induction** **motor** drive there are **torque** and **flux** ripples because none of the VSI states is able to generate the exact voltage value required to make zero both the **torque** electromagnetic error and the **stator** **flux** error. To overcome this problem a **torque** hysteresis band with variable amplitude is proposed based on fuzzy logic. The fuzzy logic controller is used to reducing the **torque** and **flux** ripples and it improve performance DTC especially at low speed.

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estimator differs from the actual value. The effect of **stator** resistance variation on the instantaneous fluxes, **flux** angle, **torque** is studied. For the study, 50% step change in the **stator** resistance is applied at 1sec. The investigation is carried out at a low frequency under the load **torque** of 1Nm as the **stator** resistance variation is more significant at low frequency. The d and q-axis fluxes, **flux** angle, **torque** obtained are presented in Fig. 2, Fig. 3, Fig.4 and Fig.5 respectively. From the results obtained, it is observed that as soon as the step change in **stator** resistance is applied at 1 sec, the d-axis **flux**, q-axis **flux**, **flux** angle and electromagnetic **torque** deviates from the actual. This in turn leads the drive system become unstable. This necessitates the need for **stator** resistance estimator.

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In the conventional DTC a voltage vector applies for the entire switching period, and this causes the **stator** current and electromagnetic **torque** to increase over the whole switching period. For small errors, the electromagnetic **torque** exceeds its reference value early during the switching period, and continues to increase, causing a high **torque** ripple. This is then followed by switching cycles in which the zero switching vectors are applied in order to reduce the electromagnetic **torque** to its reference value. The ripple in the **torque** and **flux** can be reduced by applying the selected inverter vector not for the entire switching period, as in the conventional DTC **induction** **motor** drive, but only for part of the switching period. The time for which a non-zero voltage vector has to be applied is chosen just to increase the electromagnetic **torque** to its reference value and the zero voltage vector is applied to the rest of the increase in the number of semiconductor switches in the inverter. During the application of the zero voltage vector no power is absorbed by the machine, and thus the electromagnetic **flux** is almost constant; it only decreases slightly. Fig. 4 shows a DTC **induction** **motor** drive with a duty ratio fuzzy logic controller. The average input DC voltage to the **motor** during the application of each switching vector is δV dc . By varying the duty ratio between zero and one, it is possible to apply

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ABSTRACT - Vector **control**, also called field- oriented **control** (FOC), is a Variable frequency Drive (VFD) **control** method in which the **stator** currents of a 3 phase **induction** **motor** are identified as two orthogonal components that can be visualized with a vector. The vector **control** of **induction** motors is one of the most suitable and popular speed **control** technique presently used. The vector **control** technique decouples the two components of **stator** current space vector: one providing the **control** of **flux** and the other providing the **control** of **torque**. The two components are defined in the synchronously rotating reference frame. With the help of this **control** technique the **induction** **motor** can replace a separately excited dc **motor**. The scalar **control** technique is simple to implement but have the coupling effect ultimately responsible for the sluggish response, which leads to instability due to higher order system effect. The DC **motor** needs time to time maintenance of commutator, brushes and brush holders. The main effort is to replace DC **motor** by an **induction** **motor** and merge the advantages of both the motors together into variable speed brushless **motor** drive and eliminate the associated problems. The squirrel cage **induction** **motor** being simple, rugged, and cheap and requiring less maintenance, has been widely used **motor** for fixed speed application. The **induction** **motor** is transformed from a non-linear to linear **control** plant. It is expected that with increasing computational power of the DSP controllers, it will eventually nearly universally displace scalar volts -per-Hertz (V/f) **control**. In this paper we will come to know the concept of vector **control** and different types of vector **control** techniques available. And finally we will be able to compare them.

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This paper describes a mix of **direct** **torque** **control** (DTC) and space vector modulation (SVM) for a customizable speed sensor less **induction** **motor** (IM) drive. The **motor** drive is provided by a two-level SVPWM inverter. The inverter reference voltage is gotten in view of information output criticism linearization **control**, utilizing the IM display in the **stator** – axes reference frame with **stator** current further more **flux** vectors segments as state factors. Additionally, a powerful full-arrange versatile **stator** **flux** observer is intended for a speed sensor less DTC-SVM system and another speed-versatile law is given. By outlining the observer pick up **matrix** in view of state criticism H_∞ **control** hypothesis, the strength and robustness of the observer systems is guaranteed. At last, the viability and validity of the proposed **control** approach is verified by simulation results. Keywords : **Direct** **Torque** **Control** (DTC), Speed Sensor less **Induction** **Motor** (IM) Drive, Space Vector

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The **direct** **torque** controlled **induction** **motor** drive has decoupled **control** of **stator** **flux** and **torque** and has the feature of precise and quick **torque** response and reduction of the complexity of field oriented **control** (FOC) algorithms. In DTC, the generation of inverter switching state is made to restrict the **stator** **flux** and electromagnetic **torque** errors with in the respective **flux** and **torque** hysteresis bands so as to obtain the fastest **torque** response and highest efficiency at every instant. But in conventional DTC, the common mode voltage is very high because of the switching of zero voltage vectors.

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Three no-load **induction** **motor** tests were made. The first one was the response to a **torque** step of 12.2 Nm which is shown in Figure 7. The response of the DTC with complex controller presented a slightly better per- formance in transient and steady state when such re- sponse is compared with the response of DTC with PI controller. It can be observed that the response time is 25 ms and the reference is followed with a small oscilla- tion. This oscillation occurs due to the natural lack of accuracy in the measurements of currents and voltages. In the second test the speed varies in forward and re- versal operation and the result is presented in Figure 8. The speed changes from 13 rad/s to -13 rad/s in 1 s and the complex gain is not changed during the test. This result confirms the satisfactory performance and the ro- bustness of the controller due to the fact that the the speed reaches the reference in several conditions. The responses of the DTC with complex controller and of the DTC with PI controller have the same performance in transient and steady state. The small error occurs due the natural lack of accuracy in the measurement of the speed.

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