SPEED CONTROL OF INDUCTION MOTOR USING VECTOR CONTROL

Under the Guidance of…N. Dharani Kumar Sir.

M.Tech

Presented by….R. Bala Murali (Y11EE887)P. Dwaraka (Y11EE883)V. Venkateswararao (Y11EE914)Khushboo Sharma (Y11EE849)

AC induction motors, which contain a cage, are very popular in variable speed drives.In many industries, we need to speed control of AC induction motor allows vector control ofthe AC induction motor running in a closed loop with the speed/position sensor coupled to theshaft PWM modules are the hybrid controller’s key features enabling motor control. The ACinduction motor is a rotating electric machine designed to operate from a 3-phase source ofalternating voltage. For variable speed drives, the source is normally an inverter that use powerswitches to produce approximately sinusoidal voltages and currents of controllable magnitudeand frequency.

The fast torque response obtained using vector control is achieved by estimating,measuring, calculating the magnitude and position of the motor flux in the machine. If this fluxis known, the stator current phasor can be aligned to maintain the field at the desired leveland to produce torque as desired. A reference a frame conversion is used to transform thethree- phase stator currents into two orthogonal components, one to control the fluxmagnitude and the other current to control the developed torque.

ABSTRACT:

INDUCTION MACHINES :Widely used machine in fixed-speed applications due to reasons of cost, size,weight, reliability, ruggedness, simplicity, efficiency and ease of manufacture. Complexity arises because of variable frequency power supply ; ac signalsprocessing and complex dynamics of ac machine.Requires more expensive higher inverters.

VECTROL CONTROL :Fast torque response obtained using this method is achieved by estimating ,calculating , magnitude and position of motor flux in machine.There are two methods to detect rotor flux position

Direct vector control methodIndirect vector method

INTRODUCTION

Ac induction motor specifications:

P=100 Hp

Vline=420V

Frequency=50 Hz

Poles 4

Ns=1500rpm

Lm=0.01664H Lr=0.017HRs= 0.03957ohm Rr=0.02215 ohm

To perform vector control, follow these steps:

• Measure the motor quantities (phase voltages and currents)

•Transform them to the 2-phase system X,Y using a Clarke transformation

• Calculate the rotor flux space vector magnitude and position angle

•Transform stator currents to the d-q coordinate system using a Park

transformation

• The stator current torque- (isq) and flux- (isd) producing components are

separately controlled.• The output stator voltage space vector is calculated using the decoupling block

DESIGN CONCEPT OF ACIM VECTOR CONTROL:

System outline:

The system is designed to drive a 3-phase ac induction motor (ACIM). The application has the

following specifications:

•Vector control technique used for ACIM control

•Speed control loop of the ACIM

•Runs on 3-phase ac induction motor control development platform at a variable line voltage of

400/420v

•The control technique incorporates:

speed control loop with an in q axis stator current loop

rotor flux control loop with an inner d axis stator current loop

field weakening technique

stator phase current measurement method

ac induction flux model calculation in an x, y –stationary reference frame

D-q establishment allows transformation from the stationary reference frame to the

rotating reference frame

space vector modulation(SVM)

•motor mode

•maximum speed of 1500 rpm at input power line 420v ac

The inverter converts DC power to AC power at the requiredfrequency and amplitude.

consists of three half-bridge units where the upper andlower switch are controlled complimentarily, meaning whenthe upper one is turned on, the lower one must be turned off,and vice versa.

As the power device’s turn-off time is longer than its turn-on time, some dead time must be inserted between the timeone transistor of the half-bridge is turned off and itscomplementary device is turned on.

The output voltage is created by PWM technique.

•An inverse Park transformation transforms the stator voltage space

vector back from the d-q Coordinate system to the 2-phase system

fixed with the stator.

• Using the space vector modulation, the output 3-phase voltage is

generated.

•The flux reference is calculated.

•Speed reference is calculated by using torque, Id and Iq.

•The rotor position (teta) is calculated for ABC to dq conversion.

•The constant speed is assumed 80 rad/sec.

•The reference torque is assumed to 120 Nm

•Apply the inverter in put voltage is Vdc=420V.

•Id* is calculate by using reference flux.

•Iq* is calculate by using the Te* and flux.

Digital Control of an AC Induction Motor:

VECTOR CONTROL OF INDUCTION MACHINE:

CLARKE TRANSFORMATION:

3-phase to 2-phase conversion.

X, PHASE A

PHASE B

PHASE C

BLOCK DIAGRAM

Id*calculation: Lm is constant. Assume flux reference is 0.96 wb. we know that Id* is ratio between flux reference and Lm. we use one gain block Kf for multiplying flux reference with constant Kf (1/Lm).

BLOCK PARAMETERS:

Calculation of Te*:

we use reference speed (is 80 rad/sec).we use one discrete time integrator.The out put is taken saturation value. Kp is proportional constant and Ki is integral constant.These values are 10 and 18 respectively.

Calculation of Iq*

Calculation of theta:

Calculation of Id and Iq:

Calculation of Iabc*:

These Iabc* and Iabc are club with using vector method. First is relay operation. Here switch/ wave time periods is h.

Fig.1 represents the voltages obtained from scope3

Fig.2 represents the voltage, rotor speed, torque and current

obtained from scope .

Fig.3 represents quadrature and direct axis currents and flux from scope 1.

ACHIVEMENTS :• The fast torque response obtained using vector control is achieved by

estimating, measuring, calculating the magnitude and position of the motor

flux in the machine.

• The stator currents are transformed from the stationary to synchronous

reference frame.

• Direct vector control scheme for induction motor was simulated using

Mat lab Simulink software package.

• The basic building block of the 3-phase A. C. Induction motor vector

control is implemented using MATLAB / simulink software.

• It is possible to control the speed of the machine by comparing the

actual motor speed Wr with a reference speed command Wref. The error is

used to calculate the command torque current component iqse using a

continuous time PID controller which is given as the command input to the

controlled the above simulation has been tested for different cases.

The present paper leads to conclusions such as:

Speed control of induction motor using parks formulation technique wassimulated using Mat lab Simulink software package.The rating of the machine simulated is 100HP, 420V, 4 Pole, 50Hz, three

phase induction motor.

Results obtained using the simulation done are presented.Fig.1 shows the calculations of three phase voltages.Fig 2 shows the calculation of voltage, rotor speed, electromagnetic torqueand rotor current.Fig 3 shows direct axis current,quadrature current and flux.

Conclusion:

REFERENCES :•AN1930 3-phase AC induction motor vector control using a 56F8ox, 56F8100 or56F8300 Device by Jaroslav Lepka, Petr Stekl•AN955 VF control of 3-phase induction motor using space vector modulation byrakesh parek.•ADSP based discrete space vector modulation direct torque control of sensor lessinduction machines. Authors F.khoucha, K. maouani, A. khelaui, K.aliouane•Induction motor theory from electrical machinery by Dr.p S.BIMBHRA, Electricaltechnology by B.L.THERAJA A.K.THERAJA.•P.C Kruse, “Analysis of electric machinery” M.C GrawHill Book company, 1987.•Peter vas “V C of AC machines”, claraedon press, Oxford publications 1991•W.Leouard,”control of electric drives”, Springer- verlog, Berlin 1984.•Edward Y-Y.HO and paresh c.sen, “Decoupling control of induction motor ”, IEEETrans.IND . Electronics, vol.35, No.2, pp.253-262, May 1988.•Scott wade, Mathew w.Dunningan, and Barry williams, “Modelling and of IMVCwith rotor resistance identification”, IEEE trans.power electronics, Vol.12,No.3,pp.495-505,may 1997