XX - 1
Control of the SuperGrid
Crowne Plaza Cabana Palo Alto Hotel
Palo Alto, California, November 6-8, 2002
Bob Lasseter
University of Wisconsin-Madison
XX - 2
Long range assumptions
• Looking 20-50 years ahead• Environmental issues will increase• Pressures to reduce carbon fuels• Address both transportation and
stationary energy needs
XX - 3
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)
XX - 4
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.
XX - 5
How to handle load power needs
• AC systems; frequency droop
• Complexity of power flow control• Need distributed control
100s of rectifiers 100,000s inverters
XX - 6
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
XX - 7
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)
XX - 8
Power Dispatch on dc voltage
Vdc
Idc Max
Idc Max
Idc Max
XX - 9
Power Dispatch on dc voltage
Vdc
Idc Max
Idc Max
Idc Max
Load shedding area
XX - 10
Single system voltage used for load tracking control
All inverters
2 inverters
Vdc
Vdc
Vac
Idc Imax
Inv1
Inv2 Inv3
Rectifier
XX - 11
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.
XX - 12
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
XX - 13
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
XX - 14
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.
XX - 15
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?
XX - 16
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.
XX - 17
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
XX - 18
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
XX - 19
Issues
• How to distribute H2 ?• Superconducting current control?• Grid vs. point-to-point?• H2 line independent from
superconducting line.• H2 microgrids
XX - 20
Possibilities
Today
• Natural gas microgrids > H2 base• Point-to-point dc superconductor