DB PECon 2008 Keynote · 2008. 11. 27. · Title: Microsoft PowerPoint - DB PECon 2008 Keynote.ppt Author: dule Created Date: 11/23/2008 11:45:13 PM

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

December 1, 2008

Future Electronic Power Distribution Systems– A contemplative view –

Dushan BoroyevichVirginia Tech, Blacksburg, Virginia, USA

Keynote presentation at:

The 2nd IEEE International Power & Energy ConferenceJohor Bahru, MALAYSIA

PECon 2008

December 1, 2008 DB-1

Power ElectronicsExpanding and Emerging Applications

Industry AutomationPowering IT

Alternativeand

DistributedEnergy

SystemsVehicularPowerSystems

Most of the Emerging Electric Power Technologies presumeMost of the Emerging Electric Power Technologies presumeActive Dynamic Control of the Electric Energy Flow (i.e. Active Dynamic Control of the Electric Energy Flow (i.e. Require the Use of Power ElectronicsRequire the Use of Power Electronics)!)!

Dushan Boroyevich: Future Electronic Power Distribution SystemsKeynote at PECon 2008, Johor Bahru, Malaysia, 1 December 2008

2


Power Electronics Future?

• Essential for societal energy needs from:

Retinal ImplantJ. G. KassakianIPEC, Niigata,

2005

organ implants

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


Electronic Focusof New Electric Power Systems

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) .

The major opportunities and challenges for synthesis and integration of these systems are in:

• High-density power converter integration; • System-oriented modeling and analysis;• System architecture design and optimization;• Power management, control, and protection.


3


Generator

480 V, 3Φ AC

Micro-Turbine

VSCFConverter

RenewableEnergy Source DC-AC

SWGRSWGR

Generator

Advanced (?) Electrical Power Systemof a Large Datacom Center

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

208 V3Φ AC

SWGR

Fan

SWBD

Analog

Telecom Power System

Battery

– 48 VDC

SWGR

PFCRectifier

PFCRectifier

...

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

120 V1Φ AC

SWGR Computer Power System

ASICs

Mem

Fan

DigitalICs

LED

AnalogICs

DC-DCConverter

AC-DCFront-End

Server

48 VDC

Non-IsolatedPOL Conv.

μP

UPS

AC-DC DC-AC

Battery

120 V1Φ AC

...

• Inefficient• Expensive• Unreliable

Very colorful patchwork inherited from last century!


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 dynamics of the sources.

• 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

Challenge: Reduce system cost, increase efficiency and availability by decoupling the dynamics of energy sources, distribution system, and loads through the use of power electronics.


4


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


More Electric Transportation

1. Variable frequency starter/generator

⇒ Eliminates Gearbox2. Variable speed drives

for ECS⇒ Eliminates Pneumatics3. High-frequency

voltage step-up/down⇒ Less Copper & Iron4. Electrical actuation⇒ Reduces Hydraulics

Similar approaches and advantages are being pursued in:1. Rail systems and vehicles (for long time)2. All-electric ships3. Hybrid electric cars, trucks, and buses

All electrical energy processed through electronic converters


5


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


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


6


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 % !


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:


7


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)


Synthesis of DCElectronic Power Distribution Systems

Fan

SWBD

Analog

Telecom Power System

Battery

– 48 VDC

SWGR

PFCRectifier

PFCRectifier

...

LED

AnalogICs

ASICs

MemIsolated POL

Converter

DigitalICs

DC-DCConverter

μP Non-IsolatedPOL Conv. ...

Computer Power System

ASICs

Mem

Fan

DigitalICs

LED

AnalogICs

DC-DCConverter

AC-DCFront-End

Server

48 VDC

Non-IsolatedPOL Conv.

μP

...

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

Fan

LED

AnalogICs

DC-DCConverter

48 VDC

Fan

LED

AnalogICs

DC-DCConverter

48 VDC

48 VDC

Fan

SWBD

Analog– 48 V

DCPFC

Rectifier

PFCRectifier

...

LED

AnalogICs

Isolated POLDigital

ICs

DC-DCConverter

Fan

SWBD

Analog– 48 V

DC

Fan

SWBD

Analog– 48 V

DCPFC

Rectifier

PFCRectifier

...

LED

AnalogICs

Isolated POLDigital

ICs

DC-DCConverter

LED

AnalogICs

Isolated POLDigital

ICs

DC-DCConverter

Isolated POLDigital

ICs

DC-DCConverter


8


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 ⋅≈⋅=


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

de

Current Back-gain Hi ( jω )

0.01

0.1

1

0-200


Pha

se [°

]M

agni

tude

Mag

nitu

de

0.01

0.1

1

Pha

se [°

]

0-200


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


9


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


Imag

inar

y

0

-50

50

100

-50 0 50 100 150Real

L

S

ZZ

• To avoid instability, the return ratio:

LS ZZL ≡must stay away from –1 !

Unstable Unstable

LoadConverter R8 V liv48 V 3.3 Vlii

siv+

–

+

–

BusConverter

0-3

-2

0

2-1

50%

Load60%

)(sZS )(sZL

LS

sisosiso

SL

Lli ZZ

vGvGZZ

Zv+

=+

=1

• Interface voltage is:

Well-known Stability Problem with “Constant Power Loads”

0.01

1

100

Mag

. [Ω

]


Source OutputLoad Input

ZS ZL

Subsystem Interaction Example– modeling and experiments with commercial converters –

3

5

Inpu

t Cur

rent

[A]

7

4.4 4.8Time [ms]

4


10


)(sZS )(sZL

LS

sisosiso

SL

Lli ZZ

vGvGZZ

Zv+

=+

=1


Imag

inar

y

0

-50

50

100

-50 0 50 100 150Real

L

S

ZZ

Source OutputLoad Input

ZLZS0.01

1

100

Mag

. [Ω

]


Subsystem Interaction Example– modeling and experiments with commercial converters –

C100 μF

LoadConverter R8 V liv48 V 3.3 Vlii

siv+

–

+

–

BusConverter

0-3

-2

0

2-1

Stable Stable

50%

100%

4.4 4.8Time [ms]

4

3

5

Inpu

t Cur

rent

[A]

7


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


11


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]

Sou

rce

Cur

rent

[A]

time [ms]

io1

io2

0 5 10

30

0

10

20

55

35

45

vo1

vo2

Breakershut-down

Bus

Vol

tage

[V]

Sou

rce

Cur

rent

[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


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


12


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.


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,


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


13


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


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 !


14


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]


Hypothetical Concepts

DOE: “GRID 2030” VISION EPRI: 2003 Electricity Technology Roadmap

• Dynamically decoupled (asynchronous), hierarchical grid• Consider both AC and DC• Gradual removal of synchronism • Start decoupling from both ends;

– HVDC backbone ⇒ Regional DC interties– Nanogrids ⇒ Microgrids

• Supplant Substations with “Electricity Routers” (“Smart Grid” isn’t it!)


15


An “Electricity Router”

+Energy Storage

ConstantFrequency AC⇔ MV DC

Connection to Base Grid

MV DC⇔ w/ isolation

HV DC

Local AC Microgrid

LV DC⇒

MV DC


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


16


Plans for New ASEAN Electric Grid

???Peninsular Malaysia – Sarawak (Malaysia)132014600 MWACBatam (Indonesia) – Singapore9???Thailand – Peninsular Malaysia122014600 MWDCSumatra (Indonesia) – Singapore 8

2007300 MWACSarawak (Malaysia) – W. Kalimantan (Indo.)112012700 MWDCPeninsular Malaysia – Singapore72019300 MWACSabah/Sarawak (Malaysia) – Brunei Daruss.102008600 MWDCPeninsular Malaysia – Sumatra (Indonesia)6

ASEAN Centre for Energy


A Dream of Electronic Energy Network

that will supplant Electric Power Gridto enable Carbon-Free Electricity by 2030

• All electricity could be generated carbon-free:Hydro Wind Solar Nuclear

• Today’s electric power grid cannot handle this due to:– No ability to absorb high % of distributed generation and storage– No adequate long-distance energy transport– No adequate energy storage

• Must use electronic networks for electric energy utilization!

• Save: bio fuels for some transportation fossil hydrocarbons for chemical products


17


Research Directions

1. Network Architectures– Dynamically decoupled, hierarchically interconnected, smart,

super-grid and a network of small-, mini-, micro-, and nano-grids, instead of single, constant-frequency ac, grid

– Distributed generation, storage, loads, and intelligence

2. Energy Transfer Protocols and Markets– Technology for continuous control of all energy flows– Enabling of efficient market mechanisms

3. Safety and Reliability– Safety & protection– Reliability & lifetime

4. Energy Storage (minutes, hours, days, seasons)

• Energy sources, HVDC, superconducting transmission, high-power electronic conversion, …


Metrics of Success

• Peak power density– Weight and volume (right-of-way, real estate, … , W/cm3, W/g)– Related to investment cost

• Energy efficiency – High efficiency at light and full load or optimized over load-cycle– Related to operating cost

• Life-cycle cost– Based on life-cycle analysis– Related to environmental and societal impact

• Reliability and Availability – Critical for economic and societal impact– Related to risk-mitigation pricing

• Safety and Protection– More design constraints than metrics of success– Critical for acceptance by community and society


18


Thank You

The work and contributions are by many CPES faculty, students, and staff.

Many global industrial and US government sponsors of CPES researchare gratefully acknowledged.

This work was supported primarily by

ERC Program of the US National Science Foundation under Award Number ECC-9731677

This trip was partially sponsored byJoint PELS / IAS / IES Chapter of

IEEE Malaysia SectionIEEE Power Electronics Society

(PELS)

This presentation is a part of Distinguished Lecturer Program organized by

IEEE Power Electronics Society.


Documents

DB PECon 2008 Keynote · 2008. 11. 27. · Title: Microsoft PowerPoint - DB PECon 2008 Keynote.ppt Author: dule Created Date: 11/23/2008 11:45:13 PM