Chapter 10
Application of Power Electronics
Power
Application of Power Electronics
10.1
10.2
10.3
10.4
10.5
10.6
10.7
DC motor drivers ( thyristor-DC motor system )
Frequency converters and AC drivers
Uninterruptible Power Supply ( UPS )
Switching Power Supply
Power factor correction (PFC)
Application in utility power system
Other applications
2
10.1 DC motor drivers
( Thyristor-DC motor system )
10.1.1 Rectifier mode of operation
10.1.2 Inverter mode of operation
10.1.3 Reversible DC motor drive system
Power
(four-quadrant operation)
a
iTv1
b
iTv2
c
iTv3
LB VT
1
LB VT2
L
LB VT
3
id
ud
M EM
+
o
3
10.1.1 Rectifier mode of operation
Waveforms and equations
ua
ud
ub
Ud  EM  R  Id  U
Power
(10-1)
where
3 XB
R   RB  RM 
2
(for 3-phase half-wave)
uc
ud
Ud
E
idR
wt
O
a
id
ic
ia
ib
ic
wt
O
Waveforms of 3-phase half-wave
rectifier with DC motor load
4
Speed-torque (mechanic) characteristic
when load current is continuous
EM  Cen
(10-2)
For 3-phase half-wave
Ud  1.17U 2 cos a
3X I
(RB+RM+ 2B ) Cd
e
n
EM  1.17U 2 cos a  R  Id  U
a1
Power
(10-3)
a2
1.17U 2 cos a R  Id  U
n

Ce
Ce
(10-4)
For 3-phase bridge
a3
a1<a2<a3
O
Id
For 3-phase half-wave
2.34U 2 cos a R 
n

Id (10-5)
Ce
Ce
5
Speed-torque (mechanic) characteristic
when load current is discontinuous
EMF at no load (taking 3-phase
half-wave as example)
For a  60º
Power
E 0  2U 2
For a > 60º
E
E0
( 2U2)
E0'
(0.585U2)
E0  2U 2 cos(a  60 )
Idmin
O
discontinuouts
mode
continuous mode
Id
For 3-phase half-wave
6
Speed-torque (mechanic) characteristic
when load current is discontinuous
For different a
Power
The point of EMF at no
load is raised up.
E
E0
boundary
a1
a2
a3
a4
The droop rate becomes
steer. (softer than the
continuous mode)
a5
discontinuous
mode
continuous mode
O
Id
For 3-phase half-wave
(a1< a2 < a3  60º, a5 > a4 > 60º)
7
10.1.2 Inverter mode of operation
– are just the same as in the
rectifier mode of operation
except that Ud, EM and n
become negative. E.g., in
3-phase half-wave
Power
EM  1.17U 2 cos a  R  Id  U
rectifier
mode
a1
a2
a3
a4
a =b = 
2
(10-3)
n
1.17U 2 cos a R  Id  U

Ce
Ce
– Or in another form (10-4)
E M   (U d 0 cos b  I d R ) (10-11)
n
1
Ce
U d 0 cos b  IdR  (10-12)
a increasing
n
Id
b4
b3
b2
inverter
mode
b increasing
Equations
b1
Speed-torque characteristic of
a DC motor fed by a thyristor
rectifier circuit
8
10.1.3 Reversible DC motor drive system
(4-quadrant operation)
+n
converter 2 inverting
converter 1 rectifying
Id
Id
+
L
a
b
c
converter 1
Power
M EM
converter 1
+
EM M
-
Energy
Udb
-
AC
AC
source source
converter2 converter1
+
Energy
Uda
forward braking(regenerating)
converter 2
-T
Back-to-back
connection of two 3phase bridge circuits
Id
converter 1
EM M
+
-
Energy
Uda
converter2
forward motoring
O
converter 2 rectifying
+
M E
M
-
converter 1 inverting
AC
AC
source source
+ converter2
converter1
-
Id
Energy
+
+T
Udb
M EM
+
converter2
reverse braking(regenerating)
reverse motoring
-n
9
4-quadrant speed-torque characteristic
of Reversible DC motor drive system
converter 2
n
converter 1
a1
b'2
a3
a '=b '= 
2
a'4
a'3
a'2
a'1
a increasing
a2
b'3
b'4
a4
a =b = 
2
Id
b4
b3
b2
a1=b '1; a '1=b1
a2=b '2; a '2=b2
b1
b increasing
a 'increasing
Power
b 'increasing
b'1
10
10.2
Frequency converters and
AC drivers
Composite converter:
Combination of two or more converters in cascaded
connection
Power
Indirect AC to AC converters
(AC-DC-AC converters)
Composite converters
Indirect DC to DC converters
(Isolated DC to DC converters)
11
Indirect AC to AC converters
(AC-DC-AC converters)
Classifications
According to type of the DC links:
AC-DC-AC converters
Voltage-source type
Current-source type
Power
According to whether output voltage and frequency is
variable:
AC-DC-AC converters
Variable voltage variable frequency
(VVVF)
(AC-DC-AC frequency converters)
Constant voltage constant frequency
(CVCF)
In narrow sense, frequency converter only refers to
VVVF AC-DC-AC converter.
12
10.2.1 Configurations of AC-DC-AC converters
Configurations with one-direction power flow
Power
AC
Source
Voltage-source type
AC
Load
AC
Source
AC
Load
Current-source type
13
Configuration with regenerative energy
dissipating circuit
Power
AC
Source
V0
AC
Load
R0
Braking transistor and braking resistor
14
Configurations with regenerative power feedback
through inversion-mode thyristor rectifier circuit
Id
Power
AC
Source
AC
Load
Voltage-source type
AC
Source
Ud
UL
AC
Load
Current-source type
15
Configurations realizing bi-directional power
flow through double-sided PWM converters
Source
Power
AC
Source
AC
Load
Voltage-source type
Load
a
b
c
U
V
W
Current-source type
16
10.2.2 Major Applications of AC-DC-AC
frequency converters (VVVF converters)
Power
Adjustable speed AC motor drives
Advantages of AC motors over DC motors
Energy saving on AC motors
High-performance AC motor drives
Control of AC motors driven by AC-DC-AC frequency
converters (VVVF converters)
Constant voltage frequency ratio control
Slip frequency control
Vector control
Direct torque control
17
10.3 Uninterruptible power supplies (UPS)
Basic configuration of UPS
Rectifier
Inverter
Power
Electricity
utility
Load
Source
Major Applications of CVCF converters
18
UPS with back-up energy source
Electricity
utility
Rectifier
Power
S
Diesel
Engine
Inverter
1
Load
2
Source
19
UPS with back-up energy source
and bypass lines
Bypass lines
Power
Electricity
utility
Rectifier
S1
Diesel
Engine
Inverter
1
Load
3
4 S2
2
Source
20
10.4 Switching Power Supply
Linear power supply
Line
Line frequency
frequency
AC input
DC
Transformer
Rectifier
Filter
Series Pass
Regulator
Regulated
DC output
Power
Isolation
• Switching power supply
High
frequency
AC
Line
frequency
AC input
Rectifier
DC
Filter
Inverter
High
frequency
AC
Transformer
Rectifier
Filter
Regulated
DC output
Isolation
Indirect DC to DC converter
21
Point of load regulation (POL)
Power
Specifically means a particular switching
power supply for a large size IC chip, such
as a CUP or a memory chip.
Synchronous Buck
Synchronous Boost
22
Power
A typical application of switching power supply
Power system for telecommunication equipment
23
Control of switching power supply
Voltage mode control
Current mode control
Power
– Peak current mode control
– Average current mode control
24
Power
Voltage mode control
25
Power
Current mode control
26
Power
Peak current mode control
27
Power
Average current mode control
28
10.5 Power Factor Correction (PFC)
Operation principle of typical PFC circuit
– Single-phase boost PFC
– 3-phases single-switch boost PFC
Power
Single stage PFC
29
Power
Single-phase boost PFC
30
Power
3-phases single-switch boost PFC
31
Power
Single stage PFC ( S 2 PFC )
A typical
S 2 PFC
converter
32
Power
10.6 Application in utility power system
High voltage DC transmission (HVDC)
Reactive power compensation
Harmonics suppression
Power quality control, FACTS and custom
power
33
Power
High voltage DC transmission (HVDC)
34
Reactive power compensation
Power
Thyristor switched capacitor (TSC)
Thyristor controlled reactor (TCR)
Static var generator (SVG)
35
Thyristor switched capacitor (TSC)
I
Power
U
36
TSC waveforms when the capacitor is
switched in/out
us
uVT
1
iC
Power
us
uC
uC
C
uVT1
t
t
VT1
VT2
iC
t
VT1
VT2
t
t1
t2
The voltage across the thyristor must be nearly zero
when switching in the capacitor, and the current of
the thyristor must be zero when switching out the
capacitor.
37
Power
TSC with the electronic switch realized
by a thyristor and an anti-parallel diode
The capacitor voltage will be always charged up to
the peak of source voltage.
The response to switching-out command could be a
little slower (maximum delay is one line-cycle).
38
Thyristor-controlled reactor (TCR)
To control the effective current flowing through the
reactor by controlling delay angle, therefore control
the reactive power absorbed by the reactor.
Power
ua
n
ia
a
b
ub
c
uc
a)
b)
c)
图4-12
39
Static var generator (SVG)
Power
Also called static compensator (STATCOM)
VSC based SVG
CSC based SVG
40
Power
Operation principle of SVG
41
Harmonic suppression
Harmonic compensation
Power
Two solutions
Power factor correction
Circuit configuration of an Active power factor (APF)
42
Power
Operation principle of APF
43
Power
Power quality control
Power quality problems
Power quality controllers
Current harmonics
APF
Reactive power
SVC or SVG
Voltage sag
Dynamic voltage restorer
(DVR)
Voltage flicker
Universal power quality
controller (UPQC)
44
Power
Flexible AC Transmission System (FACTS)
FACTS is actually a general term of application if
power electronic to the utility electric power
transmission system - for higher controllability and
larger transmission capacity.
Typical FACTA devices
– SVC
– SVG
– Thyristor Switched Series Capacitor (TSSC)
– Thyristor Controlled Series Compensator (TCSC)
– Static Synchronous Series Compensator (SSSC)
– Unified Power Flow Controller (UPFC)
45
Power
Custom Power
Custom power is a general term of application of
power electronics to the utility electric power
distribution system for better quality and higher
reliability of the power supplying to different
customers.
Typical Custom Power devices
– SVC or SVG (D-STATCOM)
– DVR
– APF
– Solid State Transfer Switch (SSTS)
46
10.7 Other applications
Power
Lighting
– Power supply for different lamps
– Power supply for gas discharge lamps is
specifically called ballast.
Typical configuration of an electronic ballast
Welding
Typical configuration of a welding power supply
47