MPSOC Design Approach of FPGA Based Controller For Induction Motor Drive

MPSOC Design Approach of FPGA Based Controller For Induction Motor Drive

Gayathri.V

PG Student, Department of ECE

East Point College of Engineering and Technology Bangalore, India

Arun Kumar. M

Associate Prof, Department of ECE

East Point College of Engineering and Technology Bangalore, India

Abstract Modern embedded control systems require high performance digital devices to answer their growing complexities. The high of FPGA has made it an appropriate solution for motor drive application. This paper presents a speed control strategy for a three phase induction motor. Firstly the induction machine is mathematically modeled and the transformation is with respect to rotor flux. Secondly a matlab/simulink model is designed and developed based on the principle of vector control. Thirdly the induction motor is fed from a three hose inverter bridge. The triggering pulses required for the inverter are generated using state vector pulse width modulation technique. The svpwm is realized on the same chip. Finally the developed model is simulated using matlab.

Keywords IVOC- Indirect Vector oriented control, FPGA- Field Programmable Gate Array, State Vector PWM,MPSOC-Multi Process Systen On Chip.

1. INTRODUCTION

   In the last years, several research studies proved that FPGA is an appropriate alternative to implement digital controllers in several application areas, such as motion control, power electronics, and motor control over pure software solutions and analog solutions Control of AC induction machines using the vector control techniques is becoming more popular nowadays. The objective of vector control of induction machine is to allow an induction machine to be controlled just like a separately excited dc machine. When the dynamic equations for an induction machine is transformed by means of rotating transformation methods into a reference frame that coincides with rotor flux, the results become similar to that of a DC machine. This allows AC machine to be controlled just like a DC machine. This method of decoupling the variables and controlling them independently is termed as vector control. The Pulse Width Modulation (PWM) Technique called Vector Modulation, which is based on space vector theory, is the most important development in the last few years. Although, several of PWM methods have been created in the past, the vector modulation technique appears to be the best alternative for a three phase switching power converter. Since the concept of multilevel PWM converter was introduced, various modulation strategies have been developed and studied in detail, such as multilevel sinusoidal PWM, multilevel selective harmonic elimination and space vector modulation. Among these strategies, the space vector PWM (SVPWM) [14][15] stands out because it offers significant flexibility to optimize switching waveforms and is well suited for digital implementation. The IVOC with space vector pwm

   controller is modeled in matlab/simulink and the simulation result is presented in this paper.

2. MATHEMATICAL MODEL OF THREE PHASE INDUCTION MOTOR

Induction machine modeling has continuously attracted the attentions of researchers not only because such machines are made and used in larger numbers i.e. (80% of all the loads), but also due to their varied modes of operation both under steady state and dynamic state. The basic purpose of using d-q model[13][6] approach to control the motor parameters independently i.e. torque and flux of the induction motor. By this modeling approach, all of the machine parameters are assessable for control and verification purposes. As long as equations are known, any drive or control algorithm can be modeled in Simulink.

A. D-Q Modelling of Three Phase Induction Motor

The induction machine d-q or dynamic equivalent circuit is shown in Fig. 1 & 2 .The modeling equations are as given below.

Fig. 1 Quadrature Axis Equivalent Circuit

Fig. 1 Direct Axis Equivalent Circuit

Stator voltage equations[6][8][13]

Vqs=Rs iqs + + ds (1)

Vds=Rs ids + dqs (2)

Rotor voltage equations[6][8][13]

Stator flux equations[6][8][13]

qs=Ls iqs+Lm iqr (5)

ds=Ls ids+Lm idr (6)

Rotor flux equation[6][8][13]s

qr=Lr iqr+Lm iqs (7)

dr=Lr ids+Lm ids (8)

Stator current equations [6][8][13]

Ids = (ds- md) (9)

Iqs = (qs- mq) (10)

Rotor current eqution[6][8][13]

Idr = (dr- md) (11)

Iqr = (qr- mq) (12)

Torque eqution [6][8][13]

Te=1.5P (ds iqs – qs ids) (13)

Te TL = J (14)

= P/2J (Te-TL) (15)

Where

Fig. 3 Block Diagram of IVOC

1. DEVELOPMENT OF IVOC SIMULINK MODEL

   The simulink model developed as shown in the fig below. In this system, rotor reference frame is chosen as the reference frame for transforming the dynamic equations of the induction motor. The induction motor is fed by a current-controlled three phase inverter bridge. The stator currents are regulated by by svpwm which generate drive signals for the inveter switches which is converted to Sa, Sb, and Sc.The torque is controlled by the quadrature-axis

   Ls = Lls

   +Lm

   (16)

   component of the stator current iqs*. The rotor flux is controlled by the direct-axis component ids*.The motor

   Lr = Llr +Lm (17)

   d: direct axis q:quadrature axis s: stataor variable r:rotor variable

   e =stator angular electrical frequency, r= rotor angular electrical speed.

   ij = is the flux linkage (i=q or d and j=s or r), P: number of poles,

   J: moment of inertia,

   Te: electrical output torque,

   TL (or Tl) : load torque,

   III. BLOCK DIAGRAM OF IVOC

   Fig.3 shows the block diagram of an indirect vector control system for an induction motor. The dq frame is fixed to the rotor flux position which is defined by the angle. The rotor position is sensed by a position detector and used in conversion from dq to abc.The induction motor is fed by a current-controlled three phase inverter bridge. The stator currents are regulated by state vector pulse width modulation technique which generates inverter drive signals for the inverter switches.

   speed is regulated by a control loop which produces the torque control signal iqs*. The iqs* and ids* current references are converted into phase current references ia*, ib*, and ic* for the current regulators.

   1. Simulink model of IVOC:

      Fig.4 Simulink Model of IVOC

   2. Descripition of individual processes

      Fig: 5 Process 1

      abcto transformation (Clarkes transformation):

      The transformation of three phase to two is done using clarks and parks transformation.The transformation equations are implemented in the abc todq convertion block and the eqations are as below

      (18)

      (19)

      Fir: 7 Process 3

      Speed controller block

      In the speed controller block PI controller is implemented and the reference torque is calculated by implementing the torque equation given below

      (Te* calculation):

      (25)

      iq* calculation :

      (26)

      (27)

      to dq axes (Parks transformation)

      (20)

      – + (21)

      Fig: 6 Process 2

      Fr (flux) calculation:

      Fr = (22)

      dt (23)

      (24)

      Fig: 8 Process 4

      Fig. 8 represents the current controller blocks the estimated currents and the referenc currents are compared and the required voltages are computed using the following equations.

      Sub blocks of process 4

      Fig: 8.1 Sublocks of process 5

      Fig: 8.1.1 estimation of Vsq

      Fig. 8.1.2 Estimation of Vsd

      (28)

      (28.1)

      (29)

      (29.1)

      Fig. 10 Process 5

      vdq tovabc transformation block:

      The the two phase to three phase conversion is obtained clark and parks transformation.The equations are as given below.

      Fig. 9 dq to abc transformation

      d-q to transformation:

      v =

      to abc transformation:

      (30)

      (31)

      (32)

      Fig. 10.1 Sub block of process 10

      Three phase inverter :

      Fig. 11 Inverter Bridge

      Fig. 11.1: Sub blocks of Inverter Bridge

      Induction motor d-q block:

      Table.1 Voltage Vectors, Switching Vectors, Phase voltages and the Line to Line Vectors

      [6][8][13]

      Fig:12 Induction motor dq block

      (33)

      [6][8][13] [6][8][13]

      (34)

      (35)

      (36) [6][8][13]

      (37) (36) [6][8][13]

   3. Principle of SVPWM:

In vector coordinates, the combinations of three-phase inverter output voltages form eight space vectors as depicted in figure 5.There are six nonzero space vector forming an origin centered hexagon, and the circle is the maximum trajectory of the regular sinusoidal outputs in linear modulation. This figure also illustrates the PWM output patterns in the six regions (denoted as sector I-VI) separately. In accordance with three phase to two phase transformation , the three phase inputs (Va, Vb, Vc)are transformed into (V , V ) as the reference vectors. [15][16][17]

Fig. 14 The eight inverter voltage sequence.

Fig. 13 Basic Eight Switching Vectors and Vector Representation of Sector I.

1. Results

   Fig. 15SVPWM simulation output pulses.

   Fig.16 Three pase bridge rectifier output

   Fig. 17 The induction motor output

   1. THREE PHASE STATOR CURRENTS

      1. Torque

      2. Speed

      1. CONCLUSION.

         The IVOC simulink model for a three phase induction motor was developed and simulated using matlab/Simulik.

      2. FUTURE SCOPE

The simulink model developed can be coded in hardware description language and implement on FPGA and can be applied to any real time system.

REFERENCES

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3. P.Pillai,Senior member IEEE,V Levin, Mathematical Models For Induction Machines

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6. Ashutosh Mishra1, Prashant Choudhary2 Speed Control Of Acosta, M Vilargat,Travieso,M Dourte, Matlab based simulation toolbox for the study and design of induction motor foc speed drives

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    Pathak

13. Advanced power electronic and AC drives – Bimal .K Bose

14. Implementation of SVPWM in FPGA through Matlab/Simulink Environment. K Vinoth Kumar et. Al. / International Journal of Engineering Science and Technology.

15. Space Vector Pulse Width Modulation Schemes for Two- Level Voltage Source inveter P.Tripura1, Y.S.Kishore Babu2, Y.R.Tagore2 1 Vignans Nirula Institute of Technology & Science for Women, EEE Dept.,Guntur,A.P.,INDIA Matlab/Simulink

16. Implementation of SVPWM in FPGA through Environment. K Vinoth Kumar et. Al. / International Journal of Engineering Science and Technology.

17. SV PWM Pattern Generator using Field Programmable Gate Array Implementation Prawin Ange l ,Michael 1, Dr. N. Devarajan 22009 International Conference on Machine Learning and Computin IPCSIT vol.3 (2011) © (2011) IACSIT Press, Singapore