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
PI controller

3. Current-Controlled Converters
Current need to be controlled (in drives):
To control the torque
To limit the current – protect the switching devices
Motor
Example of current control in cascade control structure
converter
speed
controller
position  + *
1/s
current T* *   kT Kt

4. Current-Controlled Converters
ON-OFF Controllers
Separated PWM block
Hysteresis
Non-linear
controllers
PI controllers
Linear
controllers

5. Current-Controlled Converters
PI-based (linear controller)
Vdc
Pulse width
modulator vc
iref PI +  q
vtri
Vdc q vc q
Vdc
Pulse width
modulator vc

6. Current-Controlled Converters
PI-based – extending to 3-phase
i*a + PI
PWM
PWM
Converter
i*b + PI
PWM
PWM
i*c + PI
PWM
PWM
Sinusoidal PWM
Motor
Interactions between phases  only require 2 controllers
Tracking error

7. Current-Controlled Converters
PI-based
Perform the 3-phase to 2-phase transformation
- only two controllers (instead of 3) are used
Perform the control in synchronous frame
- the current will appear as DC
Interactions between phases  only require 2 controllers
Tracking error

8. Current-Controlled Converters
PI-based
i*a
PWM + PI
Converter
i*b
i*c
Motor

9. Current-Controlled Converters
PI-based
i*a
3-2
PWM
2-3 PI
Converter
i*b
i*c
3-2
Motor

10. Current-Controlled Converters
PI-based PI
controller
dqabc
(stationary stationary)
abcdq
(stationary  stationary)
SVM
or SPWM
VSI IM
va*
vb*
vc*
ids
iqs + 
Ids*
iqs*

11. Current-Controlled Converters
PI-based PI
controller
dqabc
(rotating stationary)
abcdq
(stationary  rotating)
SVM
or SPWM
VSI IM
va*
vb*
vc*
ide
iqe + 
Ide*
iqe*
Synch speed
estimator s

12. Current-Controlled Converters
PI-based – simulation with control in stationary frame
Simulink and SimPowerSystems
References PI
controllers
Load
32
transformation
VSI
32
transformation

13. Current-Controlled Converters
PI-based – simulation with control in stationary frame
d and q current components viewed in rotating frame
ia as viewed in stationary frame

14. Current-Controlled Converters
PI-based – simulation with control in synchronous frame
Simulink and SimPowerSystems 14

15. Current-Controlled Converters
PI-based - simulation with control in synchronous frame
d and q current components viewed in rotating frame
ia as viewed in stationary frame 15

16. Current-Controlled Converters
Hysteresis-based +
Vdc − ia ia + Va 
iref va
iref
ierr q q
ierr

17. Current-Controlled Converters
Hysteresis-based - extending to 3-phase system
Motor +
i*a
i*b
i*c
Converter

18. Current-Controlled Converters
Hysteresis-based - extending to 3-phase system
High bandwidth, simple implementation, insensitive to parameter variations
Variable switching frequency – depending on operating conditions
Instantaneous error for isolated neutral load can reach double the band
For isolated neutral load, ia + ib + ic = 0
control is not totally independent h id iq is h

19. Current-Controlled Converters
Hysteresis-based – simulink block
VSI
Load
References
Hysteresis
comparators

20. Current-Controlled Converters
Hysteresis-based – simulation results
Current error
Actual and reference currents
Actual current locus

21. Current-Controlled Converters
Hysteresis-based – simulation results 21