Transcript ELECTRIC DRIVES - Universiti Teknologi Malaysia

ELECTRIC DRIVES
CONVERTERS IN ELECTRIC DRIVE SYSTEMS
MODULE 2
Dr. Nik Rumzi Nik Idris
Dept. of Energy Conversion, UTM
2013
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
hysteresis
fixed frequency
SVM-based
AC-DC controlled rectifier
2 Vm

+
50Hz
1-phase
Vo 
Vo
2Vm
cos 

90o
180o 
90o
180o 
Average voltage
over 10ms


2 Vm

3VL  L ,m
50Hz
3-phase

+
Vo

Vo 
3VL  L,m

cos
Average voltage
over 3.33 ms

3VL  L ,m

For steady state continuous current flow
AC-DC controlled rectifier
Dual Converter – 4Q operation
3phase
supply
+
3-phase
supply
Vt

(i) Non-simultaneous operation
(ii) Simultaneous operation

Q2
Q1
Q3
Q4
T
AC-DC controlled rectifier
Single Converter – 4Q operation
R1
F1
3-phase
supply
+
Va
F2
R2
(i) F1 and F2  quadrants 1 and 4
(ii) R1 and R2  quadrants 2 and 3

Q2
Q1
Q3
Q4
T
AC-DC controlled rectifier
+
vc
firing
circuit

controlled
rectifier
Va
–
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
AC-DC controlled rectifier
linear firing angle control
Vm

0
vc
2
3
Input voltage
4
vt
Sawtooth compared with control signal
Results of comparison to trigger SCRs
Output voltage
AC-DC controlled rectifier
linear firing angle control
vt vc

 
Vm

0
2
3
vc
 
vt
4
vt
vc
vc


Va 

v 
2Vm
cos c  

 vt 
A non-linear relation between Va and vc
AC-DC controlled rectifier
Cosine-wave crossing control
Vm
0
vc

3
2
vs
Input voltage
4
Cosine wave compared with vc
Results of comparison trigger SCRs
Output voltage
AC-DC controlled rectifier
Cosine-wave crossing control
cos(t)= vc
Vscos()
Vm
0

2
vc
3
v 
  cos 1  c 
 vs 
4
vs

2Vm v c  1  v c  
   
coscos
Va 

 vs 
 vs 

A linear relation between vc and Va
AC-DC controlled rectifier
e.g. cosine wave crossing control
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
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
AC-DC controlled rectifier
Control model
G H (s)  Ke
T
 s
2
Single phase, 50Hz
vc(s)
Va(s)
K
2Vm
Vs
T=10ms
Three phase, 50Hz
K
3VL  L ,m
Vs
T=3.33ms
Simplified if control bandwidth is reduced to much lower than the
sampling frequency
AC-DC controlled rectifier
MATLAB v7.1, SIMULINK v7.5
SympPowerSystems toolbox
SIMULINK EXAMPLES
Open-loop control
Closed-loop control
AC-DC controlled rectifier
Open loop
+
vc
controlled
rectifier

firing
circuit
Va
–
DC motor
modeled with
R-L and Vdc
Step
+
-
v
Voltage Measurement1
i
Controlled Voltage Source
-
+
+
Current Measurement1
-
signal
Scope2
Scope
A
+
B
C
pulses
+
-
Series RLC Branch
Universal Bridge
v
Scope1
+
-
v
alpha_deg
AB
BC
+
-
v
i
pulses
CA
Block
Synchronized
6-Pulse Generator
acos
Step1
Trigonometric
Function
-KGain
+
-
Current Measurement
Three-phase AC source
Step
+
-
v
Voltage Measurement1
i
Controlled Voltage Source
-
+
+
Current Measurement1
-
signal
Scope2
Scope
A
+
B
C
pulses
-
Series RLC Branch
Universal Bridge
+
v
Scope1
+
-
v
alpha_deg
AB
BC
+
-
v
i
pulses
CA
+
Current Measurement
Block
Synchronized
6-Pulse Generator
acos
Step1
Trigonometric
Function
-KGain
Controlled rectifier
‘Firing circuit’
scr_openloop_3phase.mdl
-
Load
AC-DC controlled rectifier
Closed loop
+
current
controller
iref
vc
 controlled
rectifier
firing
circuit
Va
–
Step
+
+
-
-
v
v
• To control the current – current-controlled converter
• Torque can be controlled
• Only operates in Q1 and Q4 (single converter topology)
i
-
+
+
A
+
B
C
pulses
-
Series RLC Branch
Universal Bridge
+
v
+
-
v
alpha_deg
AB
BC
+
-
v
i
pulses
CA
Block
Synchronized
6-Pulse Generator
PID
Signal
Generator
5
Constant1
PID Controller1
acos
-K-
+
-
-
signal
Scope2
Scope
Open-loop system from previous simulation
Step
+
+
-
-
v
v
i
-
+
+
A
+
B
C
pulses
+
-
Series RLC Branch
Universal Bridge
v
+
-
v
alpha_deg
AB
BC
+
-
v
i
pulses
CA
Block
Synchronized
6-Pulse Generator
PID
Signal
Generator
acos
-K-
PID Controller1
5
Constant1
Closed-loop elements
scr_closedloop_3phase.mdl
+
-
-
signal
Scope2
Scope