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. AC-DC controlled rectifier+ Vo  
50Hz
1-phase
90o
180o
Average voltage over 10ms
50Hz
3-phase + Vo  
90o
180o
Average voltage over 3.33 ms
For steady state continuous current flow

4.  T AC-DC controlled rectifier Dual Converter – 4Q operation
3-phase
supply + Vt 
Non-simultaneous operation
Simultaneous operation Q1 Q2 Q3 Q4  T

5.  T AC-DC controlled rectifier Single Converter – 4Q operation F1 F2
+ Va -
3-phase
supply
F1 and F2  quadrants 1 and 4
R1 and R2  quadrants 2 and 3 Q1 Q2 Q3 Q4  T

6. ? AC-DC controlled rectifier firing circuit controlled rectifier  +Va – vc
vc(s) ?
va(s)
DC motor
The relation between vc and va is determined by the firing circuit
It is desirable to have a linear relation between vc and va

7. AC-DC controlled rectifier
linear firing angle control Vm
Input voltage  2 3 4 vt vc
Sawtooth compared with control signal
Results of comparison to trigger SCRs
Output voltage

8. AC-DC controlled rectifier
linear firing angle control Vm  2 3 4 vt vc vc   
A non-linear relation between Va and vc

9. AC-DC controlled rectifier
Cosine-wave crossing control Vm
Input voltage  2 3 4 vc vs
Cosine wave compared with vc
Results of comparison trigger SCRs
Output voltage

10. AC-DC controlled rectifier
Cosine-wave crossing control
Vscos() = vc
Vscos(t) Vm  2 3 4 vc vs  
A linear relation between vc and Va

11. AC-DC controlled rectifier
e.g. cosine wave crossing control

12. AC-DC controlled rectifier
Control model
Va is the average voltage over one period of the waveform
- sampled data system
Delays depending on when the control signal changes – normally taken as half of sampling period

13. AC-DC controlled rectifier
Control model
Va is the average voltage over one period of the waveform
- sampled data system
Delays depending on when the control signal changes – normally taken as half of sampling period

14. AC-DC controlled rectifier
Control model
Single phase, 50Hz
vc(s)
Va(s)
T=10ms
Three phase, 50Hz
T=3.33ms
Simplified if control bandwidth is reduced to much lower than the sampling frequency

15. AC-DC controlled rectifier
SIMULINK EXAMPLES
MATLAB v7.1, SIMULINK v7.5
SympPowerSystems toolbox
Open-loop control
Closed-loop control

16. AC-DC controlled rectifier
Open loop + Va – vc
controlled rectifier
firing
circuit 
DC motor modeled with R-L and Vdc

17. Load Controlled rectifier ‘Firing circuit’ Three-phase AC source
scr_openloop_3phase.mdl

18. AC-DC controlled rectifier
Closed loop + Va –
iref
current
controller vc
firing
circuit 
controlled rectifier
To control the current – current-controlled converter
Torque can be controlled
Only operates in Q1 and Q4 (single converter topology)

19. Open-loop system from previous simulation
Closed-loop elements
scr_closedloop_3phase.mdl