Analysis of Motoring and Generating Operation Through Vector Control Induction Machine Drive

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International Journal of Electronics Communication and Computer Technology (IJECCT) Volume 2 Issue 1 (January 2012)

ISSN:2249-7838 IJ ECCT | www.ijecct.org 47

Analysis of Motoring and Generating Operation

Through Vector Control Induction Machine Drive

Hemant Chouhan Dinesh Chandra Jai

Dept. of Electrical & Electronics Engineering Dept. of Computer Sc. & Engineering SVITS, Indore, India SVITS, Indore, India

chouhan31@gmail.com dineshwebsys@gmail.com

Abstract— This paper presents a wide Range of

acceptability of model for different values of load and for various types and ratings of induction motor. The uniqueness of the model lies on deviation. Due to changes in reference step on sudden application the values of torque and speed varied for machine drive. When any sudden changes in the speed reference is desired, the speed and torque waveforms reveal that the time taken in coming back to their final steady state values is very less and the motor overcomes the perturbation with negligible transients. This concept gives the solution for motoring and generating modes.

Keywords: Induction motor, mathematical model, torque controller.

I. INTRODUCTION

The Analysis of Motoring and Generating Operation Through Vector Control Induction Machine Drive is the most important concept that are being used in the real world applications. Speed closed loop control is widely used in induction motor drive system. In vector control, the AC motor is equivalent to the DC motor by coordinate transformation. The decoupling control of the electromagnetic torque can be completely realized by using vector control [1]. The strategy of the vector control is also discussed in detail. For the voltage source inverter, the method of rotor flux orientation and waveform generation of current-traced SPWM are adopted. The simulation model of the system is established under MATLAB according to the vector control model. The vector control of ac drives [1] has been widely used in high performance control system. Indirect field oriented control (IFOC) is one of the most effective vector control of induction motor due to the simplicity of designing and construction. In order to obtain the high performance of torque and speed of an IM drive, the rotor flux and torque [2].

II. MODELINGOFINDUCTIONMACHINE

Vector control drives seek to dynamically regulate motor torque as directly and accurately as possible. Speed is regulated indirectly by providing exactly the torque required to operate the driven equipment at the desired speed [3]. Vector control drives use a mathematical model of the motor to dynamically determine the values of the essential operating and control parameters. They are called "vector control" drives because this

analysis is based on a vector representation of current, voltage and magnetic flux.

The mathematical model of a three-phase, Y-connected, squirrel-cage induction motor and load is described by equations in the synchronously rotating reference frame.

TABLE I. NOMENCLATURE

Ls, Lm, Lr Stator, mutual, rotor inductance

Rs, Rr Stator, rotor Resistance

P no. of Pole

VdS, VqS d-axis and q-axis component of stator voltage vector

Vs

Vdr, Vqr d-axis and q-axis component of rotor voltage vector Vr

idS, iqS & idr,

iqr

d-axis and q-axis component of stator/rotor current vector Is

Te, J , Exciting torque, moment of inertia

e, r sl Synchronous, rotor, slip speed

ds, dr Stator and rotor leakage flux

is Stator current

Vqs= Rsiqs+ Fqs+ ( e/ b )Fds (1)

Vds= Rsids+1/ b Fds - ( e/ b )Fqs (2)

0= Rriqr+1/ b Fqr+ ( e- r)/ bFdr (3)

0= Rridr+1/ b Fdr -( e- r)/ b Fqr (4)

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Figure 1. Block Diagram of Vector Control

= (5)

= b (6)

= b (7)

= b (8)

Torque equation is

Te = (9)

The speed rcan’t be normally treated as a constant. It can be related to the torques as [1-2]:

Te = TL + J =TL + J (10)

Figure 2. Dynamic or d-q equivalent circuit diagram of induction motor

In the vector control, the AC motor can be equivalent to the DC motor under the principle of generating the same magneto motive force. Firstly, the model of the three-phase asynchronous motor is converted into an equivalent model based on ds-qs static coordinate. Secondly, by using rotating coordinate transformation, the ds-qs model is converted into an equivalent mode under dr- qr, coordinate, which is in synchronously with the rotating magnetic field [1, 4].

III.TORQUEANDFLUXCONTROLLER

Figure 3. Vector controlled drive

The physical principle of vector control can be understood more clearly with the help of de- qe circuit. Since currents ids and iqs are being controlled, ideally stator side Thevenin’s impedance is infinity, that is, the stator side

parameter and EMFs are of no consequence. With qr=0 under all condition, EMF sl qr=0 in the de circuit. This indicates that at steady state, current ids flow through magnetizing branch only to establish the rotor flux r but transiently, the current will be shared by rotor circuit also an time constant can be easily seen as Lr/Rr. in the qe circuit, when torque controlled by iqs, EMF sl dr in the rotor circuitis modified instantly because sl dr=LmRr iqs/Lr [5, 6, 7].

is= (11)

Figure 4. Torque controller

Figure 5. Flux controller

IV.MOTORINGANDGENERATINGOPERATION

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ISSN:2249-7838 IJ ECCT | www.ijecct.org 49 The system will use Field Orientated Control principles to

adjust the motors speed and torque [10-12]. A block Diagram of the proposed control system is shown in fig. (1).

Figure 6. Vector Control Model

V.SIMULINKRESULT

A. Vector control in motoring mode:

1) When load torque is changed, speed is constant (10 Hz).

Figure 7. Torque-Speed response at 5 n-m

a) At supply frequency 10 Hz speed is 300RPM.

b) Motor torque is varies from 15 n-m to 5nm

c) Step is change from 0.3sec (15 n-m), at this moment some transient comes into Picture, after that transient torque is steady state at 5 n-m.

d) Motor torque is varies but speed is constant at 300 R.P.M.

B. Vector control in generating mode:

1) System response at above the synchronous speed (60 Hz)

Figure 8. Torque-Speed response at 10 n-m and -10 n-m

a) At 10 Hz supply frequency, speed is 300 RPM, but at 60 Hz supply frequency, speed is 1800RPM.

b) Motor torque is varies from (10) n-m to (-10) n-m c) Step is change from 0.3sec (10 n-m), at this moment some transient comes into picture, after that transient torque is steady state at (-10 n-m.)

d) At above the synchronous speed (1500 RPM) induction motor will operated as an induction generator, For this operating mode, slip is negative[13,14].

VI.CONCLUSION

The proposed technique is simple but provides a high performance torque control solution. The proposed scheme can be used in applications where there is no need for speed control or simply to insure the in- dependency of rotor resistance. Finally, with the help of model to simulate both induction motors and generator has been shown so that no requirement for different models for different application.

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