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Center for Power Electronics Systems
Future Electronic Power Distribution
Systems
– A contemplative view –
Dushan Boroyevich
Virginia Tech, Blacksburg, Virginia, USA
presentation to
IEEE Rock River Valley Section and
IEEE Power Electronics Society Chapter
Woodward Technology Center
Center, Rock Valley College
Rockford, IL
January 28, 2010
IEEE Guide for Technical Writing
Use terminology that is:
1. Common in the engineering and scientific disciplines involved,
2. Standard and widely used in research publications,
3. Generally accepted practice and well understood in IEEE.
Some Examples:
Phrase:
“It is well known …”
Meaning:
I did not spend the time to find references …
Phrase:
“It can be easily shown …”
Meaning:
It is too complex to explain in less than 10 pages …
January 28, 2010
db-1
More Examples
Phrase:
“Correct within an order of magnitude …”
Meaning:
W
Wrong.
Phrase:
“P li i
“Preliminary
tests
t t were inconclusive.”
i
l i ”
Meaning:
It did not work.
Phrase:
“Typical
Typical results are shown …
…”
Meaning:
The best results are shown …
or:
The only results are shown …
January 28, 2010
db-2
Power Electronics:
Expanding and Emerging Applications
Powering IT
Vehicular
Power
Systems
January 28, 2010
Industry Automation
Alternative
and
Distributed
Energy
Systems
db-3
Power Electronics:
Expanding and Emerging Applications
Most of the Emerging Electric Power Technologies
presume
Powering Control
IT
Industry
Automation
Active Dynamic
of the Electric
Energy
Flow
(i e Require the Use of Power Electronics)!
(i.e.
Electronics)!
Vehicular
Power
Systems
January 28, 2010
Alternative
and
Distributed
Energy
Systems
db-4
Advanced (?) Electrical Power System
of a Large Datacom Center
• Inefficient
• Expensive
• Unreliable
Generator
Very colorful patchwork
inherited from last century!
Generator
Renewable
Energy Source
DC-AC
SWGR
SWGR
SWGR
VSCF
Converter
MicroTurbine
480 V
V, 3Φ AC
SWGR
480 V, 3Φ AC
SWGR
SWGR
AC-DC
AC
DC
AC-DC
AC
DC
480 V, 3Φ AC
SWGR
ASD
SWGR
ASD
SW G R
Battery
SWGR
Battery
DC-AC
24 V, 1Φ AC
Emergency Lighting
Fire Alarm System
Electronic
Ballast
SWBD
LED
Digital
ICs
Mem
Central
Fan
Compressor
HVAC System
120 V
1Φ AC
PFC
Rectifier
Isolated POL
Converter
SWGR
Non-Isolated
POL Conv.
January 28, 2010
..
.
Battery
120 V
1Φ AC
ASD
ASD
Motor
Motor
…
Analog
ICs
LED
DC-DC
Converter
208 V
3Φ AC
ASD
AC-DC
DC-AC
Batteryy
Fan
Digital
ICs
Mem
AC-DC
Front-End
ASICs
UPS
..
.
Server
Non-Isolated
POL Conv.
db-5
Motor
Pumps and Fans
48 V
DC
..
.
ASICs
μP
Motor
Computer Power System
120 V
1Φ AC
PFC
Rectifier
Fan
…
Electronic
Ballast
SWGR
– 48 V
DC
DC-DC
C
Converter
t
Electronic
Ballast
Motor
Lighting
Telecom Power System
Analog
Analog
ICs
120 V, 1Φ AC
DC-AC
120 V, 1Φ AC
SW G R
μP
Barriers / Challenge
• Complexity of traditional power systems:
– Fully coupled dynamics of generation, distribution, and delivery.
– System stability is enabled by imposing an overwhelming, slow,
electromechanical or electrochemical d
dynamics
namics of the so
sources.
rces
• Inadequate controllability of traditional power systems:
– Only
y ON/OFF control ((difficult energy
gy management)
g
)
– Good at load agglomeration but not at distributed generation
• No adequate energy storage
• Safety
S f t and
d protection,
t ti
reliability,
li bilit cost,
t tradition,
t diti
...
Challenge:
Reduce system cost,
cost
increase efficiency and availability
by decoupling the dynamics of
energy sources
sources, distribution system
system, and loads
through the use of electronic power conversion.
January 28, 2010
db-6
Electronic Power Distribution System:
A Notebook PC
Disk
Drive
I /O
12 V
Logic
Processor
0.7-1.7 V
Memory
1.8 V
Backlight
800 V
Voltage
Regulator
Voltage
Regulator
CCFL
Inverter
Boost
Converter
Peripherals
LDO
Regulator
3.3 V
Bus
5 V Bus
Bus
Converter
Bus
Converter
12-16 V
Power
Management
Battery
Charger
LCD Bias
–8V
LCD
Converter
19 V
90 260 V
90-260
AC
Adapter
50-60 Hz
• Load converters: Meet dynamic energy requirements of the loads
• Source converters: Meet ac line standards; improve battery utilization
• Power Distribution Converters:
REDUCE
COST !
– IIncrease peak-power
k
efficiency
ffi i
⇔ Improve
I
power density
d
it
– Increase light-load efficiency ⇔ Improve energy efficiency
January 28, 2010
db-7
Electronic Power Distribution System:
More Electric Transportation
All electrical energy processed
through electronic converters
1. Variable frequency
starter/generator
⇒ Eliminates Gearbox
2. Variable speed drives
for ECS
⇒ Eliminates Pneumatics
3. High-frequency
voltage step-up/down
⇒ Less Copper & Iron
4. Electrical actuation
⇒ Reduces Hydraulics
Similar approaches and advantages are being pursued in:
1. Rail systems and vehicles (for long time)
2. All-electric ships
p
3. Hybrid electric cars, trucks, and buses
January 28, 2010
db-8
Electronic Power Distribution System:
Evolution of Wind Turbine Power Electronics
Variable--speed doublyVariable
doubly-fed wind turbine
1. Eliminates gear box and need for doubly-fed
induction generator
2. Simpler transformer structure
3. Fully decouples wind and grid dynamics
January 28, 2010
db-9
Electronic Power Distribution System:
Evolution of Wind Turbine Power Electronics
Direct geargear-less variablevariable-speed wind turbine
1. Eliminates gear box and need for doubly-fed
induction generator
2. Simpler transformer structure
3. Fully decouples wind and grid dynamics
January 28, 2010
db-10
Electronic Power Distribution System:
Grid-interface for Offshore Wind Farms
January 28, 2010
db-11
Electronic Power Distribution System:
Grid-interface for Offshore Wind Farms
AC Transmission for Offshore Energy Harvesting
January 28, 2010
db-12
Electronic Power Distribution System:
Grid-interface for Offshore Wind Farms
HVDC Transmission for Offshore Energy Harvesting
January 28, 2010
db-13
US and Canada Electric Grid
Four major independent
asynchronous networks,
tied together only by DC
i t
interconnections:
ti
1. Eastern
Interconnected
Network
2. Quebec
3. Texas
4. Western
Interconnected
Network
January 28, 2010
db-14
CPES Sustainable Building Initiative
Solar PV
Plug-in
Plug
in Hybrid with
Bidirectional Converter
January 28, 2010
Entertainment and
Data Systems
Electric Energy
Management Center
Smart Appliances
pp
and Lighting
Grid Connection with
Bidirectional Converter
Wind Turbine
Heating, Ventilation
Heating
Ventilation,
and Air Conditioning
db-15
Patching-up the 20th Century Technology
IIntegration
t
ti
of grid,
renewables,
and storage
g
saves money!
“Smart”
appliances
save
energy!
January 28, 2010
db-16
21st Century Electronic Power Distribution
efficient, programmable, safe, … affordable
Nanogrid
g
with
Islanded
Operation
kWh
Web-based GUI
Time
• Bus architecture
• Two voltages
• Wireless
communication
• Integrated
protection
• Increased:
- availability
- energy
efficiency
- power density
January 28, 2010
db-17
Characteristics of Future
Electronic Power Distribution Systems
• Power electronics converters are used for:
– Source interface
– Load interface (only “coffee makers” are still non-electronic loads?)
– Power flow control and energy management
• Advantages:
–
–
–
–
High
Hi
h system
t
controllability,
t ll bilit fl
flexibility,
ibilit and
d responsiveness
i
Increased availability
Reduced size and weight
Increased energy efficiency
• Issues:
–
–
–
–
Subsystem interactions (power flow, power quality, EMI, thermal)
Complexity (not an issue if dynamics is understood & decoupled)
Reliability and lifetime (not protection)
Cost (not an issue if system and/or energy costs are reduced)
January 28, 2010
db-18
Simplified Power Model
of a Regulated DC-DC Converter
vi ii
Ji
Eo
Voref
Po
Ji =
η(vi , io ) ⋅ vi
[A]
Ji
Po = vo ⋅ io ≈ Voref ⋅ io
50
[V]
Vimax
40
io vo
30
50
40
30
20
Eo 20
10
10
0
Vimin
40
vi
60
80
[V]
100
Static Input Characteristic
January 28, 2010
0
voltage
regulation
mode
Voref
Iomax
current
li it
limit
mode
5
10
io
15
20
[A]
25
Static Output Characteristic
db-19
Small-signal Static Model
at an Operating Point
vi ii
Yi
Voref
Z o io vo
slope
[A]
Ji
slope
50
[V]
Vimax
40
30
50
40
30
20
Eo 20
10
10
0
Vimin
40
vi
60
80
[V]
100
Static Input Characteristic
January 28, 2010
L
O
A
D
0
voltage
regulation
mode
Voref
Iomax
current
li it
limit
mode
5
10
io
15
20
[A]
25
Static Output Characteristic
db-20
Well-known Stability Problem
with “Constant Power Loads”
vsi isi
Ysi
Vsoref
Z so
vli ili
Source Converter
Yli
Vloref
Z lo ilo vlo
Load Converter
• Interface voltage is:
Vsoref
1 / Yli
vli =
⋅ Vsoref =
1 / Yli + Z so
1 + Z so ⋅ Yli
• To
T avoid
id instability,
i t bilit th
the return
t
ratio:
ti
L ≡ Z so ⋅ Yli
must stay away from
January 28, 2010
–11
!
db-21
L
O
A
D
Synthesis of DC
Electronic Power Distribution Systems
System Integration is significantly hampered by:
• Large number of different components
• Many different manufacturers
• Lack of knowledge of internal converter structures
• Lack of information about internal converter parameters
Telecom Power System
Analog
Analog
ICs
SWBD
LED
DC-DC
Converter
PFC
Rectifier
Isolated POL
Converter
SWGR
Non-Isolated
POL Conv.
ASICs
Battery
..
.
SWBD
LED
DC-DC
Converter
Non-Isolated
Non
Isolated
POL Conv.
Server
Fan
PFC
Rectifier
Isolated POL
January 28, 2010
μP
..
.
48 V
DC
Analog
a og
ICs
LED
..
.
PFC
Rectifier
Fan
Digital
ICs
Mem
AC-DC
Front-End
– 48 V
DC
Analog
Analog
ICs
Digital
ICs
PFC
Rectifier
Analog
ICs
LED
DC-DC
Converter
..
.
ASICs
μP
48 V
DC
– 48 V
DC
Fan
Digital
ICs
Mem
Computer Power System
DC-DC
Converter
db-22
Fan
Current Back-gain Hi ( jω )
“Black Box”
Modeling Example
0.1
0.01
0
103
104
105
Frequency [rad/s]
48 V
Phase
e [°] Magnitu
ude
A commercial
60 W bus converter
-200
100
106
ii
vi
Input Admittance Yi ( jω )
1
0.01
100
0
103
104
105
Frequency [rad/s]
January 28, 2010
106
Yi
H i ⋅ io
Phase [°°] Magnitude
e
1
Output Impedance Zo ( jω )
1
0.1
0.01
100
0
-100
Zo
io
vo
Go ⋅ vi
Measured frequency
q
y
response functions
Phase
e [°] Magnitu
ude
Phase [°°] Magnitude
e
Modular Terminal Behavioral (MTB)
Low-frequency Model of DC-DC Converter
104
105
Frequency
q
y [[rad/s]]
106
8V
Audio Susceptibility Go ( jω )
1
0.1
0.01
0
-200
103
104
105
Frequency [rad/s]
db-23
106
Current Back-gain Hi ( jω )
“Black Box”
Modeling Example
0.1
0.01
0
103
104
105
Frequency [rad/s]
48 V
Phase
e [°] Magnitu
ude
A commercial
60 W bus converter
-200
100
106
ii
vi
Input Admittance Yi ( jω )
1
Yi
H i ⋅ io
103
104
105
Frequency [rad/s]
January 28, 2010
106
Output Impedance Zo ( jω )
1
0.1
0.01
100
0
-100
Zo
io
vo
Go ⋅ vi
Measured frequency
q
y
response functions
0.01
100
0
Phase [°°] Magnitude
e
1
Curve-fitted,
red ced order
reduced
transfer functions
Phase
e [°] Magnitu
ude
Phase [°°] Magnitude
e
Modular Terminal Behavioral (MTB)
Low-frequency Model of DC-DC Converter
104
105
Frequency
q
y [[rad/s]]
106
8V
Audio Susceptibility Go ( jω )
1
0.1
0.01
0
-200
103
104
105
Frequency [rad/s]
db-24
106
MTB Low-frequency Model
Verification: Load Transient
[A]
ii (t)
1.4
Measured transient response
to load step
step-change
change
1
Step
Load
0.6
43
4.3
4.4
4
4
Time [ms]
ii
vi
[V]
vi (t)
Yi
H i ⋅ io
Zo
Go ⋅ vi
io
vo
48.2
47.8
4.4
Time [ms]
January 28, 2010
3.2A
8V
48.6
4.3
7.4A
4.5
db-25
MTB Low-frequency Model
Verification: Load Transient
[A]
ii (t)
1.4
Measured transient response
to load step
step-change
change
1
Step
Load
0.6
43
4.3
4.4
4
4
Time [ms]
ii
vi
[V]
vi (t)
Yi
H i ⋅ io
Zo
Go ⋅ vi
io
vo
3.2A
8V
48.6
Simulated response to load step-change
using curve-fitted reduced order model
48.2
47.8
4.3
7.4A
4.4
Time [ms]
January 28, 2010
4.5
db-26
Current Back-gain Hi ( jω )
0.1
0.2
0.01
0.1
0
0
-200
103
104
105
Frequency [rad/s]
Phase [°] Magnittude
48 V
100
Hi (0)
03
0.3
Phase [°] Magnitude
e
1
constant power Vimax
mode
Vimin
30
50 v 60
i
[V]
106
ii
vi
Yi
Zo
H i ⋅ io
1
[V]
0.01
8
voltage
regulation
mode
4
100
0
103
Go (0)⋅vi [V]
104
105
Frequency [rad/s]
January 28, 2010
106
0
10 i
o
Iomax
Voref
current
limit
mode
20
30 [A]
Output Impedance Zo ( jω )
0.1
0.01
100
0
-100
104
105
Frequency [rad/s]
vo
Go ⋅ vi
Input Admittance Yi ( jω )
1
io
Phase [°] Magnitude
Phase [°] Magnitude
Fundamental & Low Frequency Model:
Nonlinear Behavior of Buck Converter
1
106
8V
Audio Susceptibility Go ( jω )
0.1
0.01
0
-200
103
104
105
Frequency [rad/s]
db-27
106
Subsystem Interaction Example
– modeling and experiments with commercial converters –
48 V
+
vsi
–
Bus
Converter
ili
+
vli
8V
Load
Converter
–
Z S (s ) YL (s )
50
0.01
Source Output
ZS
1/YL
103
105
F
Frequency
[rad/s]
[ d/ ]
January 28, 2010
Imaginarry
Mag. [Ω]
1
50%
L( jω )
L( s ) ≡ Z S ( s ) ⋅ YL ( s )
p
Load Input
3.3 V
100
vli = (1 + Z S ⋅ YL ) -1 ⋅ Gso ⋅ vsi
100
R
Load
60%
0
2
-50
-3
-1 0
0
107
-2
-50
0
50
Real
100
db-28
150
Subsystem Interaction Example
– modeling and experiments with commercial converters –
+
vsi
48 V
–
Bus
Converter
ili
+
vli
8V
Load
Converter
–
Z S (s ) YL (s )
100
50
0.01
3
4
Source Output
ZS
1/YL
103
105
F
Frequency
[rad/s]
[ d/ ]
4.4
Time [ms]
January 28, 2010
Imaginarry
Mag. [Ω]
Input Curre
ent [A]
1
5
50%
L( jω )
L( s ) ≡ Z S ( s ) ⋅ YL ( s )
p
Load Input
3.3 V
8 Unstable
vli = (1 + Z S ⋅ YL ) -1 ⋅ Gso ⋅ vsi
100
7
R
Load
60%
0
2
-50
-1 0
0
107
4.8
-3
-2
-50
0
50
Real
100
db-29
150
Subsystem Interaction Example
– modeling and experiments with commercial converters –
+
48 V vsi
–
Bus
Converter
ili
+
8 V vli
–
Z S (s ) YL (s )
C
Load
100 μF Converter
L( jω )
Mag. [Ω]
1
0.01
Source Output
ZS
1/YL
103
105
F
Frequency
[rad/s]
[ d/ ]
January 28, 2010
Imaginarry
50
L( s ) ≡ Z S ( s ) ⋅ YL ( s )
p
Load Input
3.3 V
100
vli = (1 + Z S ⋅ YL ) -1 ⋅ Gso ⋅ vsi
100
R
0
-3
-1 0
2
-50
0
107
-2
-50
0
50
Real
100
db-30
150
Subsystem Interaction Example
– modeling and experiments with commercial converters –
+
Bus
48 V vsi
Converter
–
ili
+
8 V vli
–
Z S (s ) YL (s )
C
Load
100 μF Converter
50
0.01
3
4
Source Output
ZS
1/YL
103
105
F
Frequency
[rad/s]
[ d/ ]
4.4
Time [ms]
January 28, 2010
50%
100
Imaginarry
Mag. [Ω]
Input Curre
ent [A]
1
5
3.3 V
L( jω )
L( s ) ≡ Z S ( s ) ⋅ YL ( s )
p
Load Input
R
9Stable
S
vli = (1 + Z S ⋅ YL ) -1 ⋅ Gso ⋅ vsi
100
7
100%
0
-3
2
-50
0
107
4.8
-1 0
-2
-50
0
50
Real
100
db-31
150
Sample Analysis of Stability, Power Quality,
Power Management, and Protection
Minimum relevant EPDS example:
• Two sources
• Two loads
• DC distribution
January 28, 2010
db-32
Power Flow Control & Protection Simulation:
Classical System Transient Example
+
10 A
380 V dc bus
io1 v
o1
with 2% short-circuit
impedance
Battery
Source Cu
urrent [A]
Bus V
Voltage [V]
io2
10 A
Charger
12.3 A
2A
Const
Const.
Load 1
Converter
vo2
Load 2
12A
Converter 1.2
12
8
io2
4
io1
0
440
vo1
vo2
360
280
0
January 28, 2010
5
Load 2 enters current limit
Breaker
shutdown
time 10 [ms]
Ö
Source impedance becomes
greater than load impedance
Ö
Small-signal instability with
constant-power loads
Ö
System shut-down
15
db-33
PV
Power Flow Control & Protection Simulation:
Classical System Transient Example
10 A
380 V dc bus
io1 v
o1
with 2% short-circuit
impedance
Battery
Load 1
Converter
Bus V
Voltage [V]
12
8
io2
4
io1
0
440
vo1
vo2
360
280
0
January 28, 2010
5
Breaker
shutdown
time 10 [ms]
15
io2
Load 2
12A
Converter 1.2
Source Cu
urrent [A]
Source Cu
urrent [A]
1 000 μF
1,000
vo2
10 A
Charger
12.3 A
2A
Const
Const.
12
1 000 μF
1,000
Additional Capacitors
R d
Reduce
Source
S
Impedance
I
d
Load 2 enters current limit
io2
8
Ö Source impedance becomes
greater
than load
4
io1 impedance
Ö Small-signal instability with
0
constant-power
loads
440
Ö
Bus V
Voltage [V]
+
vo1
System shut-down
vo2
360
280
0
5
time 10 [ms]
db-34
15
PV
Power Flow Control & Protection Simulation:
Electronic Power Distribution System
+
Battery
Charger /
Discharger
10 A
io1 v
o1
Vo1ref
1 000 μF
1,000
January 28, 2010
Load 1
Converter
380 V dc bus
with 2% short-circuit
impedance
2A
Const
Const.
vo2
io2
10 A
DC-DC
Converter
Vo2ref
12.3 A
Load 2
12A
Converter 1.2
1 000 μF
1,000
db-35
PV
Power Flow Control & Protection Simulation:
Electronic Power Distribution System
+
Charger /
Discharger
Battery
10 A
io1 v
o1
Vo1ref
Load 1
Converter
1 000 μF
1,000
380 V dc bus
with 2% short-circuit
impedance
2A
Const
Const.
vo2
io2
10 A
Vo2ref
12.3 A
Load 2
12A
Converter 1.2
1 000 μF
1,000
Bus V
Voltage [V]
Source Cu
urrent [A]
Monitoring and Control
12
io2
8
io1
4
0
440
vo1
vo2
360
280
0
January 28, 2010
5
time 10 [ms]
DC-DC
Converter
15
db-36
PV
Power Flow Control & Protection Simulation:
Electronic Power Distribution System
+
Charger /
Discharger
Battery
Iomax
10 A
10 A
io1 v
o1
Vo1ref
Load 1
Converter
1 000 μF
1,000
380 V dc bus
with 2% short-circuit
impedance
2A
Const
Const.
vo2
io2
I
10omax
A
10 A
Vo2ref
12.3 A
Load 2
12A
Converter 1.2
1 000 μF
1,000
Bus V
Voltage [V]
Source Cu
urrent [A]
Monitoring and Control
12
io2
8
io1
4
0
440
vo1
vo2
360
280
0
January 28, 2010
5
time 10 [ms]
DC-DC
Converter
15
db-37
PV
Power Flow Control & Protection Simulation:
Electronic Power Distribution System
+
Charger /
Discharger
Battery
Iomax
10 A
10 A
io1 v
o1
Vo1ref
Load 1
Converter
1 000 μF
1,000
380 V dc bus
with 2% short-circuit
impedance
vo2
io2
I
10omax
A
10 A
DC-DC
Converter
Vo2ref
12.3
20 AA
2A
Const
Const.
Load 2
12A
Converter 1.2
1 000 μF
1,000
io2
8
io1
4
0
440
vo1
vo2
360
280
0
January 28, 2010
Source Cu
urrent [A]
12
5
time 10 [ms]
Bus V
Voltage [V]
Bus V
Voltage [V]
Source Cu
urrent [A]
Monitoring and Control
15
12
8
4
0
400
io2
io1
vo2 vo1
200
0
0
System
overload!
5
Soft
shutdown!
time 10 [ms]
db-38
15
PV
Power Flow Control & Protection Simulation:
Electronic Power Distribution System
+
Charger /
Discharger
Battery
Iomax
10 A
10 A
io1 v
o1
Vo1ref
Load 1
Converter
1 000 μF
1,000
380 V dc bus
with 2% short-circuit
impedance
vo2
io2
I
10omax
A
10 A
DC-DC
Converter
Vo2ref
12.3
20 AA
2A
Const
Const.
Load 2
12A
Converter 1.2
1 000 μF
1,000
io2
8
i
System
• NO AC nor DC circuit breakers
overload!
• NO converter
overrating
by “>100% for
io1
4
8
1-2 sec for breaker clearing”
0
440
0
g of wiring,
g contactors, …
• NO overrating
400
for short-circuit
currents >10x
vo1
vo2
360
January 28, 2010
12 Possible Advantages:
• NO excess o2
energy storage for stability
io1
4
280
0
Source Cu
urrent [A]
12
Bus V
Voltage [V]
Bus V
Voltage [V]
Source Cu
urrent [A]
Monitoring and Control
vo2 vo1
200
Hence:
• Lower cost ?
Soft
shutdown!
• Higher efficiency ?
5
time 10 [ms]
15
0
time
0
5
10 [ms]
• Increased
availability
?
db-39
15
PV
Future Building as DC Nanogrid
Energy
Management
Center with
Bi-directional
Converter
kWh
Web-based GUI
EMC
Time
• Bi-directional power
conversion
• Separation of
dynamics
• Load management
• DG management
• Data acquisition
• Communication,
• Islanded operation
January 28, 2010
db-40
AC Electronic Power Distribution Systems
Generator
Generator
Renewable
Energy Source
“Electronic”
Electronic
only recently
in transportation
and datacom centers.
DC-AC
SWGR
SWGR
SWGR
VSCF
Converter
MicroTurbine
480 V
V, 3Φ AC
SWGR
480 V, 3Φ AC
480 V, 3Φ AC
SWGR
ASD
SWGR
ASD
SW G R
SW G R
Motor
120 V, 1Φ AC
Electronic
Ballast
Electronic
Ballast
…
Lighting
Electronic
Ballast
Central
Fan
120 V
1Φ AC
Motor
Compressor
HVAC System
ASD
ASD
Motor
Motor
ASD
…
Motor
Pumps and Fans
MTB Modeling
M d li
off AC EPDS:
EPDS
• More difficult due to time-varying nature of steady-state
• Large disconnect between system and converter modeling
• Use of average models in system analysis is uncommon
• “Constant-power loads” are being considered only recently
• Small-signal frequency-domain modeling still in development
January 28, 2010
db-41
MTB Modeling of
Hybrid AC/DC EDPS Components
AC to DC Rectifier
DC to AC Inverter
Active
and
Passive
AC to AC Converter
Small-signal
Small
signal frequency-domain
frequency domain modeling exists if AC side is:
• Three-phase, 3-wire or 4-wire,
Pi & Po
• No negativeg
and constant zero-sequence
q
do not vary
in steady-state
• No (low) harmonic distortion
January 28, 2010
db-42
MTB Low-frequency Model of AC-AC Converter
a
ωi
b
c
Nonlinear
AC to AC Converter
Model in stationary
coordinates
r
s
ωo
t
• If ACAC-AC equipment is nonlinear (like power converters),
it cannot be linearized due to timetime-varying steady
steady--state.
January 28, 2010
db-43
MTB Low-frequency Model of AC-AC Converter
di
dc
qi
0
Nonlinear
AC to AC Converter
Model in rotating
coordinates
do
qo
dc
0
• If ACAC-AC equipment is nonlinear (like power converters),
it cannot be linearized due to timetime-varying steady
steady--state.
• Change to rotating coordinates in synchronism
s nchronism with
ith input
inp t
and output frequencies produces equilibrium steadysteady-states.
January 28, 2010
db-44
MTB Low-frequency Model of AC-AC Converter
di
dc
qi
0
Nonlinear
AC to AC Converter
Model in rotating
coordinates
do
qo
dc
0
• If ACAC-AC equipment is nonlinear (like power converters),
it cannot be linearized due to timetime-varying steady
steady--state.
• Change to rotating coordinates in synchronism
s nchronism with
ith input
inp t
and output frequencies produces equilibrium steadysteady-states.
• SmallSmall-signal frequencyfrequency-domain models are obtained by
linearizing at the equilibrium point.
January 28, 2010
db-45
MTB Low-frequency Model of AC-AC Converter
adi
dc
ωi
b
qi
c0
Nonlinear
AC to AC Converter
Model
Modelininstationary
rotating
coordinates
dro
qso
0t
Z dd
iid
dc
ωo
iodd
• If ACpower converters),
vidAC-AC equipment is nonlinear (like G
v
dd vidsteady
it cannot be linearized due to timetime-varying
steady--state.od
Z dqioq
G
v
Ydd Ytodq
viq H dd icoordinates
d iq
dq
i
d rotating
odd H dq
d ioq
• Change
in synchronism
s nchronism
with
ith input
inp t
and output frequencies produces equilibrium steadysteady-states.
Z qq
iiq
ioq
• SmallSmall-signal frequencyfrequency-domain models are obtained by
viq
voq
linearizing
at the equilibrium point. Gqd vid
Yqq
Yqd vid H qd iod H qqioq
Gqq viq
Z qd iod
Balanced converter model in synchronous dd-q frame(s)
January 28, 2010
db-46
MTB Low-frequency Model
– DC System vs. AC System –
ii
vi
io
DC to DC
Converter
Single-Input
Si
l I
Single-Output
iid
vid
vo
iiqq
viq
⎡vo ⎤ ⎡Go ( s) − Z o ( s)⎤ ⎡vi ⎤
⎢ i ⎥ = ⎢ Y ( s ) H ( s ) ⎥ ⋅ ⎢i ⎥
i
⎣ i⎦ ⎣ i
⎦ ⎣ o⎦
iod
AC to AC
vod
Converter i
oqq
M liI
Multi-Input
voq
Multi-Output
⎡ v o ⎤ ⎡G o ( s) − Zo ( s)⎤ ⎡ v i ⎤
⎢ i ⎥ = ⎢ Y ( s) H ( s) ⎥ ⋅ ⎢ i ⎥
i
⎣ i⎦ ⎣ i
⎦ ⎣ o⎦
⎡ Z dd ( s ) Z dq ( s )⎤
⎡Gdd ( s ) Gdq ( s )⎤
Zo = ⎢
Go = ⎢
⎥
⎥
Z
(
s
)
Z
(
s
)
G
(
s
)
G
(
s
)
qq
qq
⎣ qdd
⎦
⎣ qdd
⎦
⎡Ydd ( s ) Ydq ( s )⎤
⎡ H dd ( s ) H dq ( s )⎤
Yi = ⎢
Hi = ⎢
⎥
⎥
(
)
(
s
)
(
)
(
s
)
Y
s
Y
H
s
H
qq
qq
⎣ qd
⎦
⎣ qd
⎦
January 28, 2010
db-47
AC Subsystem Interaction Example
– small-signal and average modeling and simulation –
230 V
400 Hz
v li
AC Generator
600 V
DC bus
R
St t
t
Start-up
to
135 kW
PWM Boost Rectifier
Z S (s ) YL (s )
Generalized Nyquist Criterion
• Interface voltage is:
v li = (I + Z S ⋅ YL ) -1 ⋅ VTh
L( s ) = Z S ( s ) ⋅ YL ( s )
eigenvalues
⎡e d ( s ) ⎤
⎢ e ( s ) ⎥ = eig (L( s ) )
⎣ q ⎦
must not encircle –1 !
January 28, 2010
Imaginaryy
• To avoid instability,
the return ratio
4
ed ( jω )
eq ( jω )
2
0
-3
2
-2
-1 0
0
-4
-2
-1 0
2
4
Real
6
db-48
8
10
AC Subsystem Interaction Example
– small-signal and average modeling and simulation –
230 V
400 Hz
v li
AC Generator
600 V
DC bus
R
PWM Boost Rectifier
9Stable
Z S (s ) YL ( s )
Generalized Nyquist Criterion
• Interface voltage is:
Current [[A]
L( s ) = Z S ( s ) ⋅ YL ( s )
600
eigenvalues
200
id
e
(
s
)
⎡ d ⎤
⎢ e ( s ) ⎥ = eig (L( s ) )
iq
⎣ q ⎦
0 not0.1
0.2 –10.3
must
encircle
!
Time [s]
January 28, 2010
4
Imaginaryy
Voltage [V]]
V
400
vd -1
300 v li = (I + Z S ⋅ YL ) ⋅ VTh
vq
• 200
To avoid instability,
100
the return ratio
400
St t
t
Start-up
to
135 kW
ed ( jω )
eq ( jω )
2
0
2
-2
-1 0
0
-4
0.4
-3
-2
-1 0
2
4
Real
6
db-49
8
10
AC Subsystem Interaction Example
– small-signal and average modeling and simulation –
v li
230 V
400 Hz
AC Generator
600 V
DC bus
R
PWM Boost Rectifier
St t
t
Start-up
to
180 kW
8 Unstable
Z S (s ) YL ( s )
vd
400
300
200
100
4e
vq
Imaginaryy
Current [[A]
Voltage [V]]
V
Generalized Nyquist Criterion
id
600
2
0
-2
400
200
0
eq ( jω )
d ( jω )
iq
0.1
January 28, 2010
0.2
0.3
Time [s]
-4
0.4
-1 0
2
4
Real
6
db-50
8
10
Advanced Shipboard AC Electric Power Systems
Low Voltage AC
Distribution
Low Voltage AC Bus Voltage
DC/AC
January 28, 2010
db-51
Advanced Shipboard AC Electric Power Systems
Low Voltage AC
Distribution
Low Voltage AC Bus Voltage
DC/AC
• IIncrease in
i negative
ti impedance
i
d
loads produces oscillations.
January 28, 2010
db-52
Advanced Shipboard AC Electric Power Systems
Low Voltage AC
Distribution
Low Voltage AC Bus Voltage
DC/AC
• IIncrease in
i negative
ti impedance
i
d
loads produces oscillations.
• Further increase in negative
impedance loads produces
instability.
January 28, 2010
db-53
Advanced Shipboard AC Electric Power Systems
Low Voltage AC
Distribution
Low Voltage AC Bus Voltage
DC/AC
Active
Filter
• IIncrease in
i negative
ti impedance
i
d
loads produces oscillations.
• Further increase in negative
impedance loads produces
instability.
Using
g active filter to introduce damping
p g at higher
g
frequencies
q
decouples the load from source dynamics; thence:
reduces complexity and stabilizes network !
January 28, 2010
db-54
Electronic AC Power Distribution System:
Fault Handling: One-Phase-to-Ground Short
va
ia
ib
vb
vc
ic
With Current Limiting Only
Buss Voltage [V]
250
150
50
-50
-150
50
-50
-150
-250
250
250
150
50
-50
-150
150
-250
0.300
0.320
January 28, 2010
0.340
Time [s]
0.360
0.380
With Soft Shut-Down
150
-250
Sou
urce Current [A
A]
Sou
urce Current [A
A]
Buss Voltage [V]
250
150
50
-50
-150
150
-250
0.300
0.320
0.340
Time [s]
db-55
0.360
0.380
¿ Intergrid ?
DG = Distributed Generation; mDG = milli DG; μDG = micro DG; nDG = nano DG
2
1
3
1
1
2
4
2
EMC
with hierarchical levels:
1, 2, 3, 4, …
Energy Management Center (EMC):
• Bi-directional p
power conversion
• Load management (actuation)
• DG management (actuation)
• Load data acquisition & aggregation
• DG data acquisition
q
& aggregation
gg g
• Communication, prioritization, prediction
• Islanded and dispatchable operation
January 28, 2010
EMCs are hierarchical (in acquisition and
actuation) and have distributed intelligence
with ability to make autonomous decisions
based on:
• Local conditions, time, and
environment,
• Top-down commands from system
operators, and
• Bottom-up demands from the users
• Market-based cost / real-time pricing.
db-56
Power Electronics Future?
• Essential for societal energy needs from:
organ implants
to …
Retinal Implant
carbon-free energy
J. G. Kassakian
IPEC, Niigata,
2005
% of Primary
Energy
80%
Traditional
(Wood, etc.)
60%
40%
Coal
Wind, PV,
other
renewables
bl
Oil
O
Gas
20%
Hydro
Nuclear
0%
1850 1875 1900 1925 1950 1975 2000 2025 2050
Courtesy of GE Global Technology Center
January 28, 2010
Source: Shell Global Scenarios
db-57
Meaning
Acknowledgment
I would
for like
to to
thank:
like
thank:
My numerous graduate students at CPES
for their help in simulations and experiments,
and my colleagues
Prof Fred Wang and Dr
Prof.
Dr. Rolando Burgos
for many useful discussions.
January 28, 2010
db-58
Meaning
Acknowledgment
I would
for like
to to
thank:
like
thank:
My numerous graduate students at CPES
did
thehelp
work,
for all
their
in simulations and experiments,
and my colleagues
Prof Fred Wang and Dr
Prof.
Dr. Rolando Burgos
for
many useful
discussions.
explained
to me what
it means !
January 28, 2010
db-59
Thank You
The work and contributions are by many CPES faculty, students, and staff.
Many global industrial and US government sponsors of CPES research
are gratefully acknowledged.
This presentation is a part of Distinguished Lecturer Program organized by
IEEE Power Electronics Society.
January 28, 2010
db-60