1. ELECTRIC DRIVES CONVERTERS IN ELECTRIC DRIVE SYSTEMS MODULE 2
Dr. Nik Rumzi Nik Idris
Dept. of Energy Conversion, UTM
2013

2. CONVERTERS - Module 2 AC-DC controlled rectifier approximate model
SIMULINK examples
open-loop
closed-loop
Switch Mode DC-DC converter
2-Q and 4-Q converters
Small signal modeling
unipolar
bipolar
SIMULINK example
Current-controlled for SM converters
Bridge converter
hysteresis
fixed frequency
3-phase VSI
SVM-based

3. Switch mode DC-DC converter
Two-quadrant converter Va T1 +
Vdc  D1 ia Q2 Q1 Ia + Va - D2 T2
T1 conducts  va = Vdc

4. Switch mode DC-DC converter
Two-quadrant converter Va T1 +
Vdc  D1 ia Q2 Q1 Ia + Va - D2 T2
D2 conducts  va = 0
T1 conducts  va = Vdc Va Eb
Quadrant 1 The average voltage is made larger than the back emf

5. Switch mode DC-DC converter
Two-quadrant converter Va T1 +
Vdc  D1 ia Q2 Q1 Ia + Va - D2 T2
D1 conducts  va = Vdc

6. Switch mode DC-DC converter
Two-quadrant converter Va T1 +
Vdc  D1 ia Q2 Q1 Ia + Va - D2 T2
D1 conducts  va = Vdc
T2 conducts  va = 0 Eb Va
Quadrant 2 The average voltage is made smallerr than the back emf, thus forcing the current to flow in the reverse direction

7. ? Switch mode DC-DC converter Va(s) vc(s) DC motor
Two-quadrant converter
Switching signals obtained by comparing control signal with triangular wave
Vdc + Va −
vtri q vc
We want to establish a relation between vc and Va
AVERAGE voltage
Va(s)
vc(s)
DC motor ?

8. Switch mode DC-DC converter
Two-quadrant converter
Ttri
ton 1
Vc > Vtri
Vc < Vtri vc
Vdc

9. Switch mode DC-DC converter
Two-quadrant converter d
0.5 vc
-Vtri
Vtri
-Vtri vc
For vc = -Vtri  d = 0

10. Switch mode DC-DC converter
Two-quadrant converter d
Vtri
0.5 vc
-Vtri
Vtri vc
For vc = -Vtri  d = 0
For vc = 0  d = 0.5
For vc = Vtri  d = 1

11. Switch mode DC-DC converter
Two-quadrant converter d
Vtri
0.5 vc
-Vtri
Vtri vc
For vc = -Vtri  d = 0
For vc = 0  d = 0.5
For vc = Vtri  d = 1

12. Switch mode DC-DC converter
Two-quadrant converter
Thus relation between vc and Va is obtained as:
Introducing perturbation in vc and Va and separating DC and AC components:
DC:
AC:

13. Switch mode DC-DC converter
Two-quadrant converter
Taking Laplace Transform on the AC, the transfer function is obtained as:
va(s)
vc(s)
DC motor

14. Switch mode DC-DC converter
Four-quadrant converter
leg A
leg B +
Vdc  D1 D3 Q1 Q3
+ Va  D4 Q4 D2 Q2
Positive current
va = Vdc when Q1 and Q2 are ON

15. Switch mode DC-DC converter
Four-quadrant converter
leg A
leg B +
Vdc  D1 D3 Q1 Q3
+ Va  D4 Q4 D2 Q2
Positive current
va = Vdc when Q1 and Q2 are ON
va = -Vdc when D3 and D4 are ON
va = when current freewheels through Q and D

16. Switch mode DC-DC converter
Four-quadrant converter
leg A
leg B +
Vdc  D1 D3 Q1 Q3
+ Va  D4 Q4 D2 Q2
Positive current
Negative current
va = Vdc when Q1 and Q2 are ON
va = Vdc when D1 and D2 are ON
va = -Vdc when D3 and D4 are ON
va = when current freewheels through Q and D

17. Switch mode DC-DC converter
Four-quadrant converter
leg A
leg B +
Vdc  D1 D3 Q1 Q3
+ Va  D4 Q4 D2 Q2
Positive current
Negative current
va = Vdc when Q1 and Q2 are ON
va = Vdc when D1 and D2 are ON
va = -Vdc when D3 and D4 are ON
va = -Vdc when Q3 and Q4 are ON
va = when current freewheels through Q and D
va = when current freewheels through Q and D

18. Switch mode DC-DC converter
Four-quadrant converter
Bipolar switching scheme vc
vtri +
Vdc − q
-Vdc
+ VAB 
2vtri vc vA
Vdc vB
Vdc
vAB
Vdc
-Vdc

19. Switch mode DC-DC converter
Four-quadrant converter
Bipolar switching scheme
va(s)
vc(s)
DC motor

20. Switch mode DC-DC converter
Four-quadrant converter +
Vdc − vc
vtri qa
-vc qb
Leg a
Leg b
Unipolar switching scheme
Vtri vc
-vc vA vB
vAB
The same average value we’ve seen for bipolar !

21. Switch mode DC-DC converter
Four-quadrant converter
Unipolar switching scheme
vc(s)
va(s)
DC motor

22. Switch mode DC-DC converter
SIMULINK EXAMPLES
MATLAB v6.5, SIMULINK v5
2-quadrant converter
Open-loop control
Closed-loop control (current control)

23. Switch mode DC-DC converter
SIMULATION EXAMPLES Id
2-quadrant converter +
Vdc 
vtri q vc
rl_2q_average.mdl

24. Switch mode DC-DC converter
SIMULATION EXAMPLES
2-quadrant converter
Average model

25. Switch mode DC-DC converter
SIMULATION EXAMPLES
4-quadrant converter +
Vdc − vc
vtri qa
-vc qb
Leg a
Leg b

26. Switch mode DC-DC converter
SIMULATION EXAMPLES
4-quadrant converter
Average model
unipolar_4q_with_id.mdl

27. Switch mode DC-DC converter
SIMULATION EXAMPLES
Closed-loop current control
H-bridge converter 
iref + + PI 
Small signal model
vc(s)
Va(s)
Ia(s)
Iref(s)

28. Switch mode DC-DC converter
SIMULATION EXAMPLES
Closed-loop current control
closed_loop_unipolar_4q_with_id.mdl

29. Switch mode DC-DC converter
SIMULATION EXAMPLES
Closed-loop current control
ftri = Hz
4-quadrant
Unipolar
3-phase, 50Hz
2-quadrant
DC-DC Switch mode
Controlled rectifier
For both DC-DC and Contr. Rectifier:
Current controlled, Iref = 5 A
Load: 250m , 20
Disturbance in DC source: ±70V, at 5Hz

30. Switch mode DC-DC converter
SIMULATION EXAMPLES
Closed-loop current control
ftri = Hz
4-quadrant
Unipolar
3-phase, 50Hz
2-quadrant
DC-DC Switch mode
Controlled rectifier
For both DC-DC and Contr. Rectifier:
Current controlled, Iref = 5 ± 3 A, freq 5Hz
Load: 250m , 20