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Control of the SuperGrid

Crowne Plaza Cabana Palo Alto Hotel

Palo Alto, California, November 6-8, 2002

Bob Lasseter

University of Wisconsin-Madison

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Long range assumptions

• Looking 20-50 years ahead• Environmental issues will increase• Pressures to reduce carbon fuels• Address both transportation and

stationary energy needs

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Continental SuperGrid

DC GridDC Grid

ac/dc

ac/dc

ac/dc

dc/ac Load

dc/ac Load

dc/ac Load

dc/ac Load

• Nuclear generation (other none carbon sources of energy)

• Hydrogen cooled superconducting grid

• DC network (power electronics & losses)

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DC Superconducting Network

System: Low voltage high current superconducting network (unit connected generation>DC>distribution)

Issues•Complexity of System control (100s of sources and 100,000s loads)

•Current control

References:Johnson,B.K., R.H. Lasseter, F.L. Alvarado, D.M. Divan, H. Singh, M.C. Chandorkar, and R. Adapa, "High-Temperature Superconducting dc Networks", IEEE Transactions On Applied Superconductivity, Vol. 4, No.3, pp.115-120, September 1994.

Tang, W and R.H.Lasseter, "An LVDC Industrial Power Distribution System without Central Control Unit," PECS , Ireland, June 2000.

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How to handle load power needs

• AC systems; frequency droop

• Complexity of power flow control• Need distributed control

100s of rectifiers 100,000s inverters

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Distributed Control Issues

Rectifiers (generation or storage)• Change power output depending on load.• Share load• Independent of number

Inverters• Provides stable ac voltage to the load• Provide required power for loads• Automatic load shedding

Coordination is achieved through dc voltage

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Control of injected current

i1

i2

Vdc V () 3

XacIdc

V ()

"R"3

Xac

Thyristor Controlled Rectifier

Assume no resistance in line(some ac losses due to harmonics)

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Power Dispatch on dc voltage

Vdc

Idc Max

Idc Max

Idc Max

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Power Dispatch on dc voltage

Vdc

Idc Max

Idc Max

Idc Max

Load shedding area

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Single system voltage used for load tracking control

All inverters

2 inverters

Vdc

Vdc

Vac

Idc Imax

Inv1

Inv2 Inv3

Rectifier

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Superconducting Network

System: Low voltage high current superconducting network (generation>DC>distribution)

Issues•System control•Current control

References:Johnson,B.K., R.H. Lasseter, F.L. Alvarado, D.M. Divan, H. Singh, M.C. Chandorkar, and R. Adapa, "High-Temperature Superconducting dc Networks", IEEE Transactions On Applied Superconductivity, Vol. 4, No.3, pp.115-120, September 1994.

Tang, W and R.H.Lasseter, "An LVDC Industrial Power Distribution System without Central Control Unit," PECS , Ireland, June 2000.

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Current levels in superconductors

i1

i2

Current flow is a function of over time and the line inductance.

In steady state there is a single dc voltage across the system(some ac losses due to harmonics)

V

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Issues:Control of grid currents

DC gridDC grid

Load

Load

Load

Load

Need current control devices for each segment

•Currents in segments are defined by past transients (no unique steady state)

•Issues of over-currents in segments and faults

•Adding a de-energized segment

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Superconducting Network

• Power flow control is distributed• Network current control requires new

devices*(superconducting current transfer device)

• Point-to-point only transmission • Storage needed near loads• Ideal transport of H2

*Johnson,B.K., R.H. Lasseter, F.L. Alvarado, and R.Adapa, "Superconducting Current Transfer Devices for Use with a Superconducting LVdc Mesh", IEEE Transactions on Applied Superconductivity, Vol. 4, No. 4, pp. 216-222, December 1994.

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Ratio of H2 to electricity?

• For superconductor cooling only?• Include transportation and stationary

energy needs?

• Generate some H2 at source and some at load?

• Two pipelines?

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Hydrogen only grid?

• Clusters of microgrids with H2 generators

• Small generation placed near the heat and electrical loads allows for reduncey

• The combined heat and power efficiencies can approach 95%

• Transportation is integral to system.

• Technology issues for H2 grid & storage.

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Hydrogen MicroGrid with CHP

Campus Owned Distribution (13.2

kV)

Heat Distribution

Academic Building A

Dormitory B Administrative Building

Dormitory A

Student Union

Academic Building B

To Other

Campus Loads

500 kVA 500 kVA 300 kVA

75 kVA

800 kVA

300 kVA

Generator Step Up

Transformer

Generator Protection

and Control

Paralleling Bus (4.8 kV)

Voltage Regulator

Heat Distribution

1.75 MVA

1.75 MVA

1.75 MVA

Heat Recovered from ICE Units

Load control

Communication & Control Signal Path

HG HGHG

Hydrogen

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MicroGrids in each building

H2 electric generators are placed at the point of use to provide both electricity and heat

storageHydrogen

Reference (http/certs.lbl.gov/)“Integration of Distributed Energy Resources: The CERTS MicroGrid Concept,”

R. Lasseter, A. Akhil, C. Marnay, J. Stephens, A.S. Meliopoulous, R. Yinger, and J. Eto

April 2002

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Issues

• How to distribute H2 ?• Superconducting current control?• Grid vs. point-to-point?• H2 line independent from

superconducting line.• H2 microgrids

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Possibilities

Today

• Natural gas microgrids > H2 base• Point-to-point dc superconductor