Engineering

1. Vector Control of Induction
Machines
dq
3
2 IM 3
2 dq
s
u s
i
q
q
ab
ab

2. Introduction
• The traditional way to control the speed of
induction motors is the V/Hz-control
• Low dynamic performance
• In applications like servo drives and rolling
mills quick torque response is required.
• Desire to replace dc drives led to vector
control

3. What is vector control?
• Vector control implies that an ac motor is
forced to behave dynamically as a dc
motor by the use of feedback control.
• Always consider the stator frequency to
be a variable quantity.
• Think in synchronous coordinates.

4. Basic blocks of a vector controlled drive
dq
3
2 IM 3
2 dq
s
u s
i
q
q
ab
ab

5. Addition of a block for calculation of
the transformation angle
dq
3
2 IM 3
2 dq
s
u s
i
q
q
ab
ab
Transformation
angle
calculation
r
q

6. The current is controlled in the d- and
q-directions
j
ref ref ref
s sd sq
i i
 
i
magnetization
torque production

7. Vector controller
dq
3
2 IM 3
2 dq
s
u s
i
q
q
ab
ab
Transformation
angle
calculation
r
q
Current
controller
ref
s
i
+
-

8. Rotor flux orientation
• Difficult to find the transformation angle since
the direction of the flux must be known
• Flux measurement is required
• Flux sensors (and fitting) are expensive and
unreliable
• Rotor position measurement does not tell the
flux position
• The solution is flux estimation

9. Rotor flux orientation using measured
flux
Original method suggested by
Blaschke
•Requires flux sensors
•Flux coordinates: aligned with the
rotor flux linkage
arctan r
r
b
a



 
  
 

10. Rotor flux orientation using estimated
flux
• The rotor flux vector cannot be measured,
only the airgap flux.
• Flux sensors reduce the reliability
• Flux sensors increase the cost
• Therefore, it is better to estimate the rotor
flux.

11. The current model
Current
control
Current
model
IM
drive
f
f
s
s
ref
rd

ref
T
f
s
i s
s
i
s
s
u
f
s
u
r
w
̂
̂

12. Speed control
• Applications: pumps and fans in the process
industry, paper and steel mills, robotics and
packaging, electric vehicles
• Very different dynamic requirements
• Most drives have low to medium high
requirements on dynamics. These drives are
considered here.
• Cascade control is sufficient

13. Block diagram of a speed-controlled
drive system
Current
controller ref
u
I

i
ref
i


Speed
controller
Inverter


w

ref
m
w
m
w
Electric
motor

14. Complete system

15. Clarke Transformation

16. Park transformation

17. Space Vector Modulation

18. MATLAB IMPLEMENTATION

19. CURRENT AND SPEED WAVEFORM

20. CURRENT AND SVPWM

21. References
• Zambada, Jorge (Nov 8, 2007). "Field-oriented control for motors". MachineDesign.com.
• Jump up^ Lewin, Chuck (April 10, 2006). "New Developments in Commutation and Motor
Control Techniques". DesignNews.com.
• DSP Manual (2007). "3-Phase AC Induction Vector Control Drive with Single Shunt Current
Sensing" (PDF). Freescale. p. 25, incl. esp. eq. 2–37. Retrieved May 16, 2012.
• Jump up Godbole, Kedar (Sep 23, 2006). "Field oriented control reduces motor size, cost and
power consumption in industrial applications". Texas Instruments.
• Jump up^ Bose, Bimal K. (June 2009). "The Past, Present, and Future of Power
Electronics". Industrial Electronics Magazine, IEEE 3 (2): 11.doi:10.1109/MIE.2009.932709.
• Murray, Aengus (Sep 27, 2007). "Transforming motion: Field-oriented control of ac motors".
EDN. Retrieved 11 May 2012.