1. Final year project
Analysis and simulation of a converter fed dc motor drive by using MATLAB

2. Introduction
Converter-fed dc motor drives are extensively used in special heavy duty application
The ac-dc converters also known as controlled rectifiers are generally used for the speed control of dc motors
The speed of dc motors changes due to the changes of load torque
When the torque is increased, the speed of the motor is decreases due to the voltage drop in the armature resistance
To maintain the constant speed of the motor, the armature voltage should be varied continuously by varying the alpha angle of a ac-dc converters.
Thus, the controller must be added to control the alpha angle

3. Objectives
To develop the transfer function of the dc motor with and without feedback
To design controller with a speed feedback (closed loop feedback) using PI controller and simulate the drive under different loading and reference speed.
To conduct experiments to verify results with the simulated responses.

4. Methodology
Literature Survey – References from library and IEEE website
- Through guidance from lecturers
Simulation – Using MATLAB M-file and SimPowerSystems

5. ,where
(1)
(2)
(3)
Substituting all equations above;
(4)

6. Transfer Function Using Laplace transform;
Then, the transfer function becomes;

7. Transfer functions of:
Proportional Integral Controller (PI)

8. Block Diagram of dc motor
Block diagram of converter

9. Block Diagram of a converter-fed dc motor

10. Torque – speed characteristic
The graph shown below is the effect of armature voltage speed control on a separately excited dc motor’s torque-speed characteristic.
Speed ω
Va1
Va2
Va3
Torque Τ

11. Effect of change the load torque due to the speed of the motor
Dc motor with speed-feedback controller
Change the load torque ω
Time

12. Project Research Using Matlab M-File Using Simulink (Simpowersystem)
Design requirement with 1 rad/sec step reference, settling time less than 3 sec and steady-state error less than 2 %.
Using Simulink (Simpowersystem)
Block diagram of dc motor drive with and without feedback with 100 rad/sec speed reference.
Simulation of converter fed dc motor under different loading and speed references.

13. Control input voltage = ±10V
MOTOR RATINGS FOR SIMULATION USING M-FILE AND BLOCK DIAGRAM TRANSFER FUNCTION
240 V, 8.3 A, 60 Hz, 5hp
Control input voltage = ±10V
Maximum current permitted in the motor is 20A.
Moment of Inertia (J) = (kg-m2)
Machine frictional torque coefficient (Bt) = (N.m/rad/sec)
Armature resistance (Ra) = 4 Ω
Armature Inductance (La) = H
Kb = 1.26 V/rad/sec

14. Simulation Using M-File Open loop transfer function of dc motor
Settling time>3 sec
Speed<1rad/sec

15. Proportional Integral (PI) Controller with Kp=100 and Ki=150
Settling time<3sec
Speed=1 rad/sec

16. Simulation using Simulink
Block diagram without feedback
Block diagram of speed controller dc motor drive

17. Simulation results Without feedback Settling time>3sec
Speed>100 rad/sec

18. With feedback (speed and current controller)
Settling time<3 sec
Speed= 100rad/sec

19. DC Motor ratings

20. Simulation using SimPowerSystems
Without feedback

21. Result

22. With feedback

23. Results
Constant speed and torque with Kp=2 and Ki=20

24. Constant speed with changing load torque (Kp=2 and Ki=20)

25. Step speed reference with constant torque (Kp=2and ki-20)

26. Step speed reference with changing load torque (kp=2 and ki=20)

27. Kp=2 Ki=20 6% 0.385sec 10% Kp=30 Ki=50 5% 0.175sec 2% Kp=100 Ki=150
Comparison results of using different value of Kp and ki.
Overshoot
Settling time
Steady state error
Kp=2
Ki=20 6%
0.385sec
10%
Kp=30
Ki=50 5%
0.175sec 2%
Kp=100
Ki=150
oscillates
1.9%
Good
controller

28. Experimental results
The speed with and without load when using PI controller
PI-controller parameters
Speed (ω) without load (rpm)
Speed (ω) with load (rpm)
Kp=100,Ki=200
1506
1501
Kp=100, Ki=20
1517
1520
Kp=5,Ki=10
1509
1511
Kp=1, Ki=5
1498
1502

29. Conclusion
A Proportional plus Integral (PI) controller is design to reduce the system errors and improve the dynamics responses.
The constant KP and KI in PI controller can be changed to meet the acceptable performance.
This project compares a various study in designing the converter-fed dc motor drive with and without system feedback and simulates drive under different loading and speed references.
By increasing the constant KP and KI tends to reduce the systems errors and improve the overshoot and settling time. However, large KP and KI will worsen the transients’ stability.
A good controller will change back the motor speed to the normal value due to the change of load torque. The proposed converter is designed and tested in the lab using the separately excited dc motor.
The experimental results are shown to be in good agreement with the simulated results.

30. Future Research
More extensive follow-up studies can be done so that the proposed approach is always up-to-date.
Further fine tuning of the speed controller. Example, design the Proportional Integral and Derivative (PID) controller in order to enhance and improved the transients stability. The automatic tuning is also can be done by using the Non-linear Control Design (NCD) in Simulink Blockset.
Further research in designing the four quadrant three phase rectifier in SimPowerSystems simulation.

31. References
Arthur G.O. Mutambara Design and analysis of control system.CRC Press.
A.T. Alexandridis and D.P. Iracleous, “Optimal Nonlinear Firing Angle Control Of A Converter-fed Dc Drive Systems,” IEE Proc-Electr, Power Appl., Vol 145, No.3, May 1998.
B.H.Khan, Seshagiri R.Doradla and Gopal K.Dubey, “A Three-Phase Ac-dc GTO Thyristor Converter Employing Equal Pulse - Width Modulation (EPWM),”IEEE Transactions on Industry Application, Vol 27, No.2, March/April 1991.
Charles L. Phillips and Royce D. Harbor Control Systems. 4th Edition. Prentice Hall.
“Dc Machine”
“Digital Dc Motor Speed Control with PID control”

32. Gene F. Franklin, J. David Powell, and Abbas Emami-Naeini. 1994
Gene F. Franklin, J. David Powell, and Abbas Emami-Naeini Feedback Control of Dynamic Systems. 3rd Edition. Addison-Wesley.
Katsuhiko Ogata Modern Control engineering. 4th Edition. Prentice Hall.
M Gopal Control Systems-principles and design. 3rd Edition. McGraw Hill.
M Ramamoorty An Introduction to Thyristors and their applications. 2nd Edition. East-West Press.
Muhammad H. Rashid Power Electronics-circuits, devices, and applications. 3rd Edition. Prentice Hall.
Paul C.Krause, Okg Wasynczuk and Scott D. Sudhoff Analysis of electric Machinery & Drives Systems. 2nd Edition. IEEE Press and Wiley Interscience.
Stephen J. Chapman Electric Machinery Fundamentals. 4th Edition. McGraw Hill.

33. Theodore Wildi. 2006. Electrical Machines, Drives, and Power Systems
Theodore Wildi Electrical Machines, Drives, and Power Systems. 6th Edition. Prentice Hall.
W. Shepherd, L.N. Hulley, and D.T.W. liang Power Electronics and motor control. 2nd Edition. Cambridge University Press.

34. -END-
THANK YOU!