Electronic Power Distribution Systems
Transcript of Electronic Power Distribution Systems
1
Center for Power Electronics SystemsA National Science Foundation Engineering Research Center
Virginia Tech, University of Wisconsin - Madison, Rensselaer Polytechnic InstituteNorth Carolina A&T State University, University of Puerto Rico - Mayaguez
15 April, 2008
Electronic Power Distribution Systems
Dushan Boroyevich
Power Electronics Systems IntegrationCPES Joint Course
Spring 2008
15 April, 2008 DB-1
Most of the Emerging Electric Power Technologies Presume Active Most of the Emerging Electric Power Technologies Presume Active Dynamic Control of the Power FlowDynamic Control of the Power Flow(i.e. (i.e. Require the Use of Power ElectronicsRequire the Use of Power Electronics)!)!
Power ElectronicsExpanding and Emerging Applications
Industry AutomationPowering IT
Alternativeand
DistributedEnergy
SystemsVehicularPowerSystems
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15 April, 2008 DB-2
Electronic Focusof Electric Power System Research
Emerging and future power systems will have all sources and loads interfaced through power electronics converters:
• IT Power: Portable, Server, Telecom, Data Center• More-electric aircraft, All-electric ship, Hybrid-electric car, • Sustainable energy, Distributed generation, Future power grid
Focus on: Electronic Power Distribution Systems (EPDS) .
Technical Scope:• System architecture design and optimization; • System-oriented modeling of DC EPDS;• Power quality, power management, and protection;• System-oriented modeling of hybrid AC/DC EPDS;• High-density converter integration.
OUTLINE
OOUUTTLLIINNEE
15 April, 2008 DB-3
• System stability anchored at the sources– Electromechanical– Electrochemical
• Generation, distribution, and delivery fully coupled• Overwhelming, slow, source dynamics imposed on the system• Electromechanical system control and protection
120 V, 1Φ AC
Lighting
MotorMotor
CentralFan
120 V1Φ AC
480 V, 3Φ AC
HVAC System Pumps and Fans
… …
480 V, 3Φ AC
Com-pressor
SW GRSW GRSW GR SW GRSW GRSW GR
SWGR
Electrical Power Systems of the Last Century – I
SWGRSWGR SWGRSWGR
MotorMotor MotorMotor MotorMotor
120 V1Φ AC
SWGR Computer Power System
ASICs
Mem
Fan
DigitalICs
LED
AnalogICs
Rectifier
DC-DCConverter
• System dynamics is too constraining for applications
• Slow and inefficient• Unreliable
ASDASD
ASDASD ASD ASD
Fan
SWBD
Analog
Telecom Power System
Battery
– 48 VDC
SWGR
ACMotor
DCGen.
Utility
Generator
SWGR
208 V3Φ AC
Rectifier
SWGR
3
15 April, 2008 DB-4
Fan
SWBD
Analog
Telecom Power System
Battery
– 48 VDC
SWGR
120 V, 1Φ AC
Lighting
MotorMotor
CentralFan
120 V1Φ AC
480 V, 3Φ AC
HVAC System Pumps and Fans
Utility
… …
480 V, 3Φ AC
Com-pressor
SW GRSW GRSW GR SW GRSW GRSW GR
SWGR
Electrical Power Systems of the Last Century – II
SWGR
SWGRSWGR SWGRSWGR
MotorMotor MotorMotor MotorMotor
120 V1Φ AC
SWGR Computer Power System
ASICs
Mem
Fan
DigitalICs
LED
AnalogICs
DC-DCConverter
208 V3Φ AC
SWGR
PFCRectifier
PFCRectifier
...
ASDASD
ASDASD ASD ASD
AC-DCFront-End
Server
48 VDC
Non-IsolatedPOL Conv.
μP
ElectronicBallast
ElectronicBallast
ElectronicBallast
AC-DC
DC-AC
Battery
24 V, 1Φ AC
Fire Alarm System
SWGRSWGRSWGR
DC-AC
Battery
120 V, 1Φ AC
Emergency Lighting
SWGRSWGRSWGR
AC-DC
LED
AnalogICs
ASICs
MemIsolated POL
Converter
DigitalICs
DC-DCConverter
μP Non-IsolatedPOL Conv. ...
• Highly decoupled load dynamics• Still inefficient, although more expensive• Even less reliable
Generator
15 April, 2008 DB-5
Generator
Fan
SWBD
Analog
Telecom Power System
Battery
– 48 VDC
SWGR
480 V, 3Φ AC
Micro-Turbine
VSCFConverter
RenewableEnergy Source DC-AC
SWGRSWGR
Generator
120 V, 1Φ AC
Lighting
MotorMotor
CentralFan
120 V1Φ AC
480 V, 3Φ AC
HVAC System Pumps and Fans
… …
480 V, 3Φ AC
Com-pressor
SW GRSW GRSW GR SW GRSW GRSW GR
SWGR
Electrical Power Systems of this Century?
SWGR
SWGRSWGR SWGRSWGR
MotorMotor MotorMotor MotorMotor
120 V1Φ AC
SWGR Computer Power System
ASICs
Mem
Fan
DigitalICs
LED
AnalogICs
DC-DCConverter
208 V3Φ AC
SWGR
PFCRectifier
PFCRectifier
...
ASDASD
ASDASD ASD ASD
AC-DCFront-End
Server
48 VDC
Non-IsolatedPOL Conv.
μP
ElectronicBallast
ElectronicBallast
ElectronicBallast
LED
AnalogICs
ASICs
MemIsolated POL
Converter
DigitalICs
DC-DCConverter
μP Non-IsolatedPOL Conv. ...
AC-DC
DC-AC
Battery
24 V, 1Φ AC
Fire Alarm System
SWGRSWGRSWGR
DC-AC
Battery
120 V, 1Φ AC
Emergency Lighting
SWGRSWGRSWGR
AC-DC
UPS
AC-DC DC-AC
Battery
120 V1Φ AC
...
• Inefficient• Expensive• Unreliable
Very colorful patchwork inherited from last century!
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Benefits of Classical AC Grid Systems
Source Dynamics• Active power flow control by
frequency control• Voltage control by reactive power
control
Distribution Dynamics• Passive voltage step-up/down
(transformers)– Cost; efficiency; reliability
• Protection by effective circuit breakers (zero crossings)
Load Dynamics• AC (induction) motors• Transformer-rectifiers
Challenges:• Not used in tight, single-
source systems• Not suitable for alternative
sources
• Converters, DC transmission, (high-frequency transformers)– Cost; efficiency; reliability
• Protection by active control (zero crossings not needed)– Reliability
• Only “coffee makers” are still non-electronic loads
15 April, 2008 DB-7
A Possible Future Electronic Power Distribution Systems
Legend:Power
DistributionConverters
IntegratedLoad
Converters
IntegratedSource
Converters
Telecom Equipment
...Fan
LED
AnalogICs
DC-DC …
200 V, DC BUS
Emergency and Alarms
HVAC
Pumps and Fans
48 V, DC BUS
ASICs
Mem
DigitalICs
Fan
LED
AnalogICs
μP + IPS
Lighting
Fan
Server
Server
Server
Server
DC-DCConverter
Utility Utility
SWGR
Bi AC-DCConverter
Lighting
Left
0.8
kV
DC
BU
S
Battery
Bi DC-DCConverter
DC-DCConverter
RenewableEnergy Source
Micro-Turbine
AC-DCConverter
......
DC-DCConverter
DC-DCConverter
48 V, DC BUS
DC-DCConverter
200 V, DC BUS
HVAC
Pumps and Fans
…Integ.Ballast
Integ.Ballast
…Integ.Ballast
Integ.Ballast
…IMMD IMMD
…IMMD IMMD
SWGRSWGR SWGRSWGR
SWGRSWGR SWGRSWGR
Rig
ht 0
.8 k
V D
C B
US
Computer Equipment
12 V DC
3 V DC
DC-DC
DC-DCASICs
Mem
DigitalICs
LED
AnalogICs
+ μPIPS
12 V DC
3 V DCDC-DC
DC-DC
F i r s t F l o o r
S e c o n d F l o o r
ASD
Motor
ASD
Motor
0.8V0.8V
• Hybrid and electric cars
• More-electric airplane
• All-electric ship
• Alternative energy
• Distributed generation
• Future electric power systems
Emerging and future systems:
• Telecom Power ⇒ Data Centers
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15 April, 2008 DB-8
Barriers/Challenges – I
• Traditional power systems:– Dynamics of generation, distribution, and delivery fully coupled– System stability is enabled by imposing an overwhelming, slow,
dynamics of the sources.
Challenge: Separate the dynamics of sources, distribution system, and loads.
• Local focus of power electronics:– Concentrated on load dynamics– Evolving focus on source dynamics (UPS, distributed generation,
fuel cells, alternative energy sources)– Until now, only “fixing the problems” of power distribution (ac)
Challenge: Use power electronics to separate the dynamics.
15 April, 2008 DB-9
Barriers/Challenges – II
• High cost, low efficiency, and low reliability of power electronics converters
Challenge: Enable dramatic improvements in performance, reliability, and cost effectiveness of power electronics systems by developing an integrated system approach via Integrated Power Electronics Modules (IPEMs).
• No standardization in power electronics• No modularization (definitions of IPEMs)
– “A minimum set of building blocks with integrated functionality, standardized interfaces, suitability for mass production, and application versatility.”
Challenge: Develop a physics-based, hierarchical, and consistent methodology for evaluation and trade-off analysis of different architectures, partitions, and implementations.
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Power-Converter-Based Power Systems Example: A Notebook PC
LCD Bias– 8 V
Backlight800 V
Memory1.8 V
Processor0.7-1.7 V
Logic
I /O DiskDrive
5 V Bus3.3 VBus
Peripherals
12 V
12-16 VPower
Management Battery90-260 V
50-60 Hz
19 VCharger AC Adapter
Voltage Regulator
Voltage Regulator
CCFL Inverter
LCD Converter
LDO Regulator
Bus Converter
Bus Converter
Boost Converter
• Load converters: Meet dynamic energy requirements of the loads
REDUCECOST !
• Power Distribution Converters:– Increase peak-power efficiency ⇔ Improve power density– Increase light-load efficiency ⇔ Improve energy efficiency
• Source converters: Meet ac line standards; improve battery utilization
15 April, 2008 DB-11
More Electric Aircraft
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DC Zonal Shipboard Power Distribution System
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VariableVariable--speed doublyspeed doubly--fed wind turbinefed wind turbineDirect gearDirect gear--less variableless variable--speed wind turbinespeed wind turbine
1. Eliminates gear box and need for doubly-fed induction generator
2. Simpler transformer structure
3. Fully decouples wind and grid dynamics
Wind Energy:Evolution of Turbine Power Electronics
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Electronic Power Distribution System: Grid-interface for Offshore Wind Farms
AC Transmission for Offshore Energy HarvestingAC Transmission for Offshore Energy Harvesting
HVDC Transmission for Offshore Energy HarvestingHVDC Transmission for Offshore Energy Harvesting
15 April, 2008 DB-15
Japan: The Historical Leader
in Electrical Power System Complexity
in Advanced Electric Power System Development?or
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15 April, 2008 DB-16
US and Canada Electric Grid
Four major independent asynchronous networks, tied together only by DC interconnections:
1. Eastern Interconnected Network
2. Quebec
3. Texas
4. Western Interconnected Network
Four major independent asynchronous networks, tied together only by DC interconnections:
1. Eastern Interconnected Network
2. Quebec
3. Texas
4. Western Interconnected Network
15 April, 2008 DB-17
MixedAC / DC Power
Distribution
6 A
Servers1.5 kW
Charger2.8 kW
Transfer Switch
Inverter3 kW
6 A
25 A
100 A
60 A 60 A
25 A
Transfer Switch
Battery
Charger2.8 kW
6 A
LV DC Distribution48 V DC
1Φ AC Distribution120 V AC
CPES University Testbed: Hybrid Power System for Remote-site Datacom Centers
10 A
Cooling1.5 kW
Hybrid EnergyPower Sources
Telecom and ComputerLoads with HVAC
Similar tradeoffs in terms of size, efficiency, and power density for all power converters.
Single Enclosure,Self-Contained UnitPeak-powerEfficiency< 50 % !
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15 April, 2008 DB-18
6 A
Servers1.5 kW
Charger2.8 kW
Transfer Switch
Inverter3 kW
6 A
25 A
100 A
60 A 60 A
25 A
Transfer Switch
Battery
Charger2.8 kW
6 A
LV DC Distribution48 V DC
1Φ AC Distribution120 V AC
10 A
Cooling1.5 kW
Electronic Power Distribution System (EPDS): An Integrated Testbed
Servers
DC-DC
HV DC Distribution300 V DC
Charger /Discharger RectifierRectifier
HVAC
System impact evaluation of integrated:• Active modules• Passive modules• Converters• Loads and converters
• Reduce number of converters by 30%
• Eliminate switchgear
• Improve availability
• Increase energy efficiency
Improved architectures:
15 April, 2008 DB-19
Characteristics of FutureElectronic 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 system controllability, flexibility, and responsiveness– 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)
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15 April, 2008 DB-20
Hierarchical Modular Modeling and Analysis
6 AServers1.5 kW
Charger2.8 kW
Inverter3 kW
6 A
20 A
60 A 60 A
20 A
Transfer Switch
6 A
LV DC Distribution48 V DC
1Φ AC Distribution120 V AC
6 A
Cooling1 kW
Battery
Solar Panel
Emulator
60 HzAC Grid
Motor
Motor Drives
Distributed Power Supplies
Motor
How to study large systems of converters with unknown internal
structure and parameters?
15 April, 2008 DB-21
Equivalency Between ISO/OSI and Power System Models
Physical
Link
Network
Transport
Session
Presentation
Application
Device
Component
Module
Converter
Station
Network
Transport
Power System HierarchyISO/OSI Reference Model
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The Cognitive Revolution
OutputInput
“The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing
Information”
George MillerThe Psychological Review, vol. 63, pp. 81-97, 1956
Humans asInformation Systems
15 April, 2008 DB-23
Energy Processing
Devicessemiconductors, magnetic cores,
dielectrics, heat spreaders, …
Packaged Componentstransistors, inductors, capacitors,
heat sinks, …
Integrated Modulesfor energy flow control and
energy storage
Power Converters
Power Stationparallel, series, or cascade converters
with switchgear and enclosure
Power Distribution
Generation and Transmission
1
2
3
4
5
6
7
ISO / OSI Telecom Model
Physical
Link
Network
Transport
Session
Presentation
Application
Electric Power Conversion
Device
Component
Module
Converter
Station
Network
Transport
Modeling and Simulation
Finite Element
Physics-Based Lumped Parameter
Behavioral
Average
Application
Power Flow
Cost and Quality
Control
Physical
Real-TimeOperating System
Elementary Control Objects
Data Flow
Application
Enterprise
Mission
Conceptual Reference Model
Standard-Cell, Open-Architecture, Electric Power Conversion Systems
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1 2 … mControl Terminals (u)Mode n (failure mode)
Mode 3 (overload)Mode 2 (start-up)
• Terminal models of subsystems
iHiY
iiiv
oE oZoi
ov
Modeling and Simulation Approach– a hypothesis –
12:j
1 2 … k
j+1j+2
:l
Mode 1 (normal)
Thermal Terminals (θ, p)Input PowerTerminals (v, i)
Output PowerTerminals (v, i)
IPEM
• Subsystems are mildly non-linear• Dynamics can be divided into four weakly coupled components• Modes of operation can be described using state-machine concept
– Fundamental frequency(DC, 50, 60, 400 Hz)
Active
– Very low frequency(< 100 Hz)
Thermal
– Intermediate frequency(ffund – fsw)
Reactive
– High frequency(> fsw)
EMI
ε++++= tjejrjajj vvvvv ε++++= tjejrjajj iiiiiUsing staggered singular perturbations theory, the complete response is then:
…
15 April, 2008 DB-25
ioi
oi vivη
PJ⋅
=),(
Simplified Power Model of a Regulated DC-DC Converter
iiiv
orefV
iJ oE oi ov
[A]
[V]
10
20
30
40
50
0 5 10 15 20 25
Eo
io
Iomax
voltage regulation
mode
current limit
mode
Voref
Static Output Characteristic
[V]
10
20
30
40
50
0 40 60 80 100
1 kW
450 W
Vimax
Vimin
PoJi
vi
[A]
750 W
Static Input Characteristic
oorefooo iVivP ⋅≈⋅=
14
15 April, 2008 DB-26
ovorefV
Small-signal Static Model at an Operating Point
[A]
[V]
10
20
30
40
50
0 5 10 15 20 25
Eo
io
Iomax
voltage regulation
mode
current limit
mode
Voref
[V]
10
20
30
40
50
0 40 60 80 100
1 kW
450 W
Vimax
Vimin
PoJi
vi
[A]
750 W
iiiv oi
Static Output CharacteristicStatic Input Characteristic
oZiY
slopeslope
LOAD
15 April, 2008 DB-27
lov LOAD
liilorefV
Load Converter
loZlivliY loi
Well-known Stability Problem with “Constant Power Loads”
Source Converter
soZsiisivsiY
sorefV
liso
sorefsoref
soli
lili YZ
VV
ZYYv
⋅+=⋅
+=
1/1/1
• Interface voltage is:
• To avoid instability, the return ratio:
liso YZL ⋅≡must stay away from –1 !
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15 April, 2008 DB-28
48 V 8 V
A commercial60 W bus converter
100
0
-100
0.01
0.1
1
Mag
nitu
deP
hase
[°]
Frequency [rad/s]104 105 106
Output Impedance Zo ( jω )
Input Admittance Yi ( jω )
0100
Frequency [rad/s]103 104 105 106
Pha
se [°
]
0.01
1
100
Mag
nitu
deCurrent Back-gain Hi ( jω )
0.01
0.1
1
0-200
Frequency [rad/s]103 104 105 106
Pha
se [°
]M
agni
tude
Mag
nitu
de
0.01
0.1
1
Pha
se [°
]
0-200
Frequency [rad/s]103 104 105 106
Audio Susceptibility Go ( jω )Measured frequency response functions
Modular Terminal Behavioral (MTB) Low-frequency Model of DC-DC Converter
ii
ivoi
ovoZ
iYoi iH ⋅
io vG ⋅
“Black Box”Modeling Example
Curve-fitted,reduced order
transfer functions
15 April, 2008 DB-29
ii (t)
0.6
1
1.4
4.4Time [ms]
4.3
[A]
vi (t)
47.8
48.2
48.6
4.4 4.5Time [ms]
4.3
[V]
Measured transient response to load step-change
MTB Low-frequency ModelVerification: Load Transient
8 V
ii
ivoi
ovoZ
iYoi iH ⋅
io vG ⋅ 3.2A
7.4A
StepLoad
Simulated response to load step-change using curve-fitted reduced order model
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15 April, 2008 DB-30
Output Impedance ofUnregulated Bus Converter
NonlinearLinearNonlinear
Output Impedance of Regulated Flyback Converter
• Family of local linear models for different terminal conditions
• Blend together by a smooth interpolation function
Polytopic Structure
Polytopic MTB Modeling
15 April, 2008 DB-31
Bus Converter Validation: Simultaneous variation of output current and input voltage; Load Step from 1 A to 5 A to 19 A
2 2.5 3 3.5x 10
-3
38
40
42
44
46
48
50
Time(Sec)
Vol
ts
Input Voltage
2 2.5 3 3.5x 10
-3
0
1
2
3
4
5
Time(Sec)
Am
p
Input Current
2 2.5 3 3.5x 10
-3
8
9
10
11
12
Time(Sec)
Vol
t
Output Voltage
2 2.5 3 3.5x 10
-3
0
5
10
15
20
Time(Sec)
Am
p
Output Current
Blue = Experimental
Green = Experimental Moving average
Red = Simulation
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15 April, 2008 DB-32
0.05 0.051 0.052 0.053 0.0545.06
5.08
5.1
5.12
5.14
5.16
5.18
Time(Sec)
Vol
t
Output Voltage
0.061 0.062 0.063 0.064 0.0655.06
5.08
5.1
5.12
5.14
5.16
5.18
Time(Sec)
Vol
t
Output Voltage
0.05 0.055 0.06 0.0650.5
1
1.5
2
2.5
Time(Sec)
Am
pInput Current
0.05 0.055 0.06 0.0655.05
5.1
5.15
Time(Sec)
Vol
t
Output Voltage
Closed-Loop Flyback Converter Model ValidationFixed 20 V Input; Load Step from 3 A to 4 A to 5 A
15 April, 2008 DB-33
0.01
0.1
1Current Back-gain Hi ( jω )
0-200
Frequency [rad/s]103 104 105 106
Pha
se [°
]M
agni
tude
Alternative Low Frequency Model forNonlinear Behavior of Buck Converter
Input Admittance Yi ( jω )
0100
Frequency [rad/s]103 104 105 106
Pha
se [°
]
0.01
1
100
Mag
nitu
de
30 50 60 [V]vi
0.1
0.2
0.3
0
Hi (0)
Vimax
Vimin
constant power mode
Mag
nitu
de
0.01
0.1
1
Pha
se [°
]
0-200
Frequency [rad/s]103 104 105 106
Audio Susceptibility Go ( jω )
voltage regulation
mode current limit
mode
Iomax
Voref
10 20 30 [A]0
io
8
[V]
4
Go (0)⋅vi [V]
100
0
-100
0.01
0.1
1
Mag
nitu
deP
hase
[°]
Frequency [rad/s]104 105 106
Output Impedance Zo ( jω )
48 V 8 V
ii
iv
oi
ovoZ
iYoi iH ⋅
io vG ⋅
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15 April, 2008 DB-34
Unstable Unstable
Subsystem Interaction Example– modeling and experiments with commercial converters –
LoadConverter R8 V liv48 V 3.3 Vlii
siv+
–
+
–
BusConverter
)(sZS )(sYL
)()()( sYsZsL LS ⋅≡
)1( 1siso
-LSli vGYZv ⋅⋅⋅+=
Imag
inar
y
0
-50
50
100
-50 0 50 100 150Real
L( jω )
0-3
-2
0
2-1
0.01
1
100
Mag
. [Ω
]
Frequency [rad/s]103 105 107
Source OutputLoad Input
ZS 1/YL
50%
Load60%
3
5
Inpu
t Cur
rent
[A]
7
4.4 4.8Time [ms]
4
15 April, 2008 DB-35
Source OutputLoad Input
1/YLZS0.01
1
100
Mag
. [Ω
]
Frequency [rad/s]103 105 107
Subsystem Interaction Example– modeling and experiments with commercial converters –
C100 μF
LoadConverter R8 V liv48 V 3.3 Vlii
siv+
–
+
–
BusConverter
)(sZS )(sYL
)()()( sYsZsL LS ⋅≡
)1( 1siso
-LSli vGYZv ⋅⋅⋅+=
Imag
inar
y
0
-50
50
100
-50 0 50 100 150Real
L( jω )
0-3
-2
0
2-1
Stable Stable
50%
100%
4.4 4.8Time [ms]
4
3
5
Inpu
t Cur
rent
[A]
7
19
15 April, 2008 DB-36
Analysis of Stability, Power Quality, Power Management and Protection
Charger25 A
25 A
Battery
48 V DC Distribution
Minimum relevant EPDS example:• Two sources• Two loads• DC distribution
15 April, 2008 DB-37
Load 2 enters current limit
Source impedance becomes greater than load impedance
Small-signal instability with constant-power loads
System shut-down
Power Flow Control & Protection Simulation:Classical System Transient Example
48 V dc buswith 2% short-circuit
impedancevo1 vo2io1 io2
Const.5 A
PV25 A Charger+
BatteryLoad 1
Converter
25 A
3 ALoad 2
Converter
33 A1,000 μF 1,000 μF
Additional Capacitors Reduce Source Impedance
15time [ms]
io1
io2
0 5 10
30
0
10
20
55
35
45
vo1
vo2
Breakershut-down
Bus
Vol
tage
[V]
Sour
ce C
urre
nt [
A]
time [ms]
io1
io2
0 5 10
30
0
10
20
55
35
45
vo1
vo2
Breakershut-down
Bus
Vol
tage
[V]
Sour
ce C
urre
nt [
A]
time [ms]
io1
io2
0 5 10 15
vo1vo2
Bus
Vol
tage
[V]
Sou
rce
Cur
rent
[A
] 30
0
10
20
55
35
45
20
15 April, 2008 DB-38
1,000 μF 1,000 μF
48 V dc buswith 2% short-circuit
impedancevo1 vo2io1 io2
Const.5 A
+
Battery
DC-DCConverter
Charger /Discharger
Load 1Converter
PV
3 ALoad 2
Converter
33 A
25 A25 A
Power Flow Control & Protection Simulation:Converter Controlled Distribution System
50 A
30
0
10
20
io1
io2
55
0 5 10 1535
45
time [ms]
vo1vo2
Bus
Vol
tage
[V]
Sou
rce
Cur
rent
[A
]
0 5 10 15time [ms]
vo1vo250
0
25
io1
io2 Systemoverload!
Softshutdown!
30
0
10
20
Bus
Vol
tage
[V]
Sou
rce
Cur
rent
[A
]
Vo2refVo1ref
Iomax25 A
Iomax25 A
Possible Advantages:• NO excess energy storage for stability• NO AC nor DC circuit breakers• NO converter overrating by “>100% for
1-2 sec for breaker clearing”• NO overrating of wiring, contactors, …
for short-circuit currents >10x
Hence:• Lower cost ?• Higher efficiency ?• Increased availability ?
Monitoring and Control
15 April, 2008 DB-39
Generator
480 V, 3Φ AC
Micro-Turbine
VSCFConverter
RenewableEnergy Source DC-AC
SWGRSWGR
Generator
ACElectronic Power Distribution Systems
SWGR
120 V, 1Φ AC
Lighting
MotorMotor
CentralFan
120 V1Φ AC
480 V, 3Φ AC
HVAC System Pumps and Fans
… …
480 V, 3Φ AC
Com-pressor
SW GRSW GRSW GR SW GRSW GRSW GR
SWGR
SWGRSWGR SWGRSWGR
MotorMotor MotorMotor MotorMotor
ASDASD
ASDASD ASD ASD
ElectronicBallast
ElectronicBallast
ElectronicBallast
MTB Modeling of AC 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
“Electronic”only recentlyin transportation and datacom centers.
21
15 April, 2008 DB-40
MTB Modeling of Hybrid AC/DC EDPS Components
AC to DC RectifierAC to DC Rectifier
Small-signal frequency-domain modeling exists if AC side is:• Three-phase, 3-wire or 4-wire,• No negative- and constant zero-sequence• No (low) harmonic distortion
DC to AC InverterDC to AC Inverter
AC to AC ConverterAC to AC Converter
Activeand
Passive
Pi & Podo not vary
in steady-state
15 April, 2008 DB-41
rrNonlinearNonlinearAC to AC ConverterAC to AC ConverterModel in stationary Model in stationary
coordinatescoordinates
aa
ωωii bb
cc
ss
tt
ωωoo
NonlinearNonlinearAC to AC ConverterAC to AC Converter
Model in rotating Model in rotating coordinatescoordinates
ddii
qqiidcdc
00
ddoo
qqoo dcdc
00
MTB Low-frequency Modelof AC-AC Converter
•• If ACIf AC--AC equipment is nonlinear (like power converters), AC equipment is nonlinear (like power converters), it cannot be it cannot be linearizedlinearized due to timedue to time--varying steadyvarying steady--state.state.
•• Change to rotating coordinates in synchronism with input Change to rotating coordinates in synchronism with input and output frequencies produces equilibrium steadyand output frequencies produces equilibrium steady--states.states.
•• SmallSmall--signal frequencysignal frequency--domain models are obtained by domain models are obtained by linearizinglinearizing at the equilibrium point. at the equilibrium point.
Balanced converter model in synchronous Balanced converter model in synchronous dd--qq frame(sframe(s))
idvidi
ddY iqdqvY odddiH oqdqiH
iqviqi
qqY idqdvY odqdiH oqqqiH
idddvGddZ
iqdqvG oqdqiZ
odi
odv
iqqqvG
qqZ
idqdvGodqdiZ
oqi
oqv
22
15 April, 2008 DB-42
MTB Low-frequency Model– DC System vs. AC System –
ii
iv
oi
ovDC to DCDC to DCConverterConverterSingle-Input
Single-Output
idiidv
odiodv
iqiiqv
oqioqv
AC to ACAC to ACConverterConverterMulti-Input
Multi-Output
⎥⎦
⎤⎢⎣
⎡⋅⎥⎦
⎤⎢⎣
⎡ −=⎥
⎦
⎤⎢⎣
⎡
o
i
ii
oo
i
o
iv
sHsYsZsG
iv
)()()()(
⎥⎦
⎤⎢⎣
⎡=
)()()()(
sGsGsGsG
qqqd
dqddoG
⎥⎦
⎤⎢⎣
⎡=
)()()()(
sYsYsYsY
qqqd
dqddiY
⎥⎦
⎤⎢⎣
⎡=
)()()()(
sZsZsZsZ
qqqd
dqddoZ
⎥⎦
⎤⎢⎣
⎡=
)()()()(
sHsHsHsH
qqqd
dqddiH
⎥⎦
⎤⎢⎣
⎡⋅⎥⎦
⎤⎢⎣
⎡ −=⎥
⎦
⎤⎢⎣
⎡
o
i
ii
oo
i
o
iv
HYZG
iv
)()()()(
ssss
15 April, 2008 DB-43
Stable Stable
AC Subsystem Interaction Example– small-signal and average modeling and simulation –
R50 Hz230 V
AC Generator PWM Boost Rectifier
600 VDC bus
Start-up to 135 kW
liv
)(sSZ )(sLY
( ))()()(
ssese
q
d Leig=⎥⎦
⎤⎢⎣
⎡
)()()( sss LS YZL ⋅=
• To avoid instability,
• Interface voltage is:
must not encircle –1 !
eigenvalues
the return ratio
ThLSli VYZIv ⋅⋅+= 1)( -
0-3
-2
0
2-1
-4
-2
0
2
4
0 2 4 6 8 10-1Real
Imag
inar
y
ed ( jω ) eq ( jω )
Generalized Nyquist Criterion
200
400
600
Cur
rent
[A]
0 0.1 0.2 0.3 0.4Time [s]
100200300400
Vol
tage
[V] vd
vq
id
iq
23
15 April, 2008 DB-44
200
400
600
Cur
rent
[A]
0 0.1 0.2 0.3 0.4Time [s]
100200300400
Vol
tage
[V] vd
vq
id
iq
AC Subsystem Interaction Example– small-signal and average modeling and simulation –
)(sSZ )(sLY
R50 Hz230 V
Unstable Unstable AC Generator PWM Boost Rectifier
600 VDC bus
-4
-2
0
2
4
0 2 4 6 8 10-1Real
Imag
inar
y
ed ( jω ) eq ( jω )
liv Start-up to 180 kW
Generalized Nyquist Criterion
15 April, 2008 DB-45
DC/AC
LV ACDistribution
LV AC Bus Voltage
Advanced Shipboard Electric Power Systems
• Increase in negative impedance loads produces oscillations.
• Further increase in negative impedance loads produces instability.
Active Filter
Using active filter to introduce damping at higher frequencies decouples the load from source dynamics; thence:
reduces complexity and stabilizes network !
24
15 April, 2008 DB-46
Converter Controlled AC Distribution SystemFault Handling: One-Phase-to-Ground Short
av
bv
cv
ai
bi
ciWith Current Limiting Only
Bus
Vol
tage
[V
]S
ourc
e C
urre
nt [
A]
-250
-150
-50
50
150
250
0.300 0.320 0.340 0.360 0.380Time [s]
-250
-150
-50
50
150
250With Soft Shut-Down
-250
-150
-50
50
150
250
-250
-150
-50
50
150
250
0.300 0.320 0.340 0.360 0.380Time [s]
Bus
Vol
tage
[V
]S
ourc
e C
urre
nt [
A]
15 April, 2008 DB-47
Electromagnetic Compatibility and Interference(EMC & EMI)
UPS
AC-DC DC-AC
Battery
UPS
Server
120 V1Φ AC120 V
1Φ AC
Computer Power System
480 V, 3Φ AC
Micro-Turbine
120 V, 1Φ AC
Lighting
120 V1Φ AC
480 V, 3Φ AC
HVAC System Pumps and Fans
VSCFConverter
RenewableEnergy Source DC-AC
Utility
ASICs
Mem
Fan
DigitalICs
LED
AnalogICs
AC-DCFront-End
Server
48 VDC
Non-IsolatedPOL Conv.
μP
...
…
Server
Server …
…
Utility
480 V, 3Φ AC
ElectronicBallast
ElectronicBallast
ElectronicBallast
DC-DCConverter
ASD
Motor
CentralFan
ASD
Motor
ASD
Motor
ASD
Motor
ASD
Motor
ASD
Motor
ASD
Motor
SWGR
SW GRSW GRSW GR SW GRSW GRSW GR
SWGR
SWGR
SWGRSWGR
ElectronicBallast
ASD
Motor
ASD
Motor
ASD
Motor
Com-presso
r
AC-DCFront-End
FilteredInput Current
DM EMI
Non-FilteredInput Current
Spectrum
Composite VDE / FCC Class A,B EMI LimitsFiltered
Input CurrentDM EMI
Non-FilteredInput Current
Spectrum
Composite VDE / FCC Class A,B EMI Limits
Single-Phase PFC Rectifier Input Current
Single-Phase PFC Rectifier Input Current Spectra
25
15 April, 2008 DB-48
EMI Simulation Using Multiple Modeling Techniques
Change fS, still match.Well-matched EMI
Simulation
Measurement
Effectiveness of Detailed Physical Modeling in Predicting Conducted EMI
15 April, 2008 DB-49
MTB Equivalent EMI Source Model
Zs1
Zs2
Is1
Is2
Zs3 Zs4 Zs5
P
M
N
G
Norton equivalent source and impedance
DC Bus
Ground Plane
LISN+
7.8 mF
7.8 mF 2 μF
2 μF
1 mH2 Ω400 V
40 A, 60 Hz
25 kHzDC Bus
Ground Plane
LISN+
7.8 mF
7.8 mF 2 μF
2 μF
1 mH2 Ω400 V
40 A, 60 Hz
25 kHz
Measured and predicted conducted EMI spectra of half-bridge inverter
120
60
80
[dBμV
]
100Prediction
Test 40
Differential ModePrediction
Test
0.1 1frequency [MHz]
Common Mode
0.1 1 10frequency [MHz]
26
15 April, 2008 DB-50
Concluding Remarks
Future human energy needs will be provided by new electric power systems, which from
Retinal ImplantJ. G. KassakianIPEC, Niigata,
2005
carbon-free energyto …
Source: Shell Global Scenarios
% of PrimaryEnergy
0%
20%
40%
60%
80%
Coal
Nuclear
Oil
Gas
Hydro
Traditional (Wood, etc.)
Wind, PV,other
renewables
1850 1875 1900 1925 1950 1975 2000 2025 2050Courtesy of GE Global Technology Center Source: Shell Global Scenarios
% of PrimaryEnergy
0%
20%
40%
60%
80%
Coal
Nuclear
Oil
Gas
Hydro
Traditional (Wood, etc.)
Wind, PV,other
renewables
1850 1875 1900 1925 1950 1975 2000 2025 2050Courtesy of GE Global Technology Center
will be: Distributed Power Electronics Systems
organ implants
15 April, 2008 DB-51
Thank You
The work and contributions are result of manyCPES faculty, students, and staff.
This work was supported primarily by ERC Program of the National Science Foundation under Award Number ECC-9731677.
Many other US government and industrial sponsors of CPES research are gratefully acknowledged.