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Energy Internet: An open and transactive electricity market
Energy Internet: An open and transactive electricity market
Dr. Alex Q. Huang, [email protected] Energy Distinguished Professor
FREEDM Systems Center, NC State University
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Energy Internet: An open and transactive electricity market
Outline
• Energy Internet Concept
• Key Enabling Technologies for Energy Internet
– Power delivery system
– Software platform
– Market framework
2
Energy Internet: An open and transactive electricity market
Energy Cells are to
operate and manage local generators,
energy storage, and dispatchable load
compete with each other to maximize
their own profits
Analogous to internet consumer-to-
consumer commerce (eBay) or stock market
Utilities are expected to make more
profit on providing ancillary services to
ensure the residential distribution
system security and reliability, in
addition to electricity transaction.
Energy Internet Concept
[1] W. Su, and A.Q. Huang, “A Game Theoretic Framework for a
Next-generation Retail Electricity Market with High Penetration of
Distributed Residential Electricity Suppliers” Applied Energy,
vol.119, pp.341-350, April 2014.
[2] W. Su, “The Role of Customers in the U.S. Electricity Market:
Past, Present, and Future”, The Electricity Journal, 2014. (invited)
Energy Internet: An open and transactive electricity market
Grid Infrastructure Needs: A Resilient Grid to support plug-and-play
Power
Factor
Correction
DC/DC
Converter
CPU
Power
System
Power
Memory
Power
Graphics
Power
400V (DC)
< Front end AC/DC >
< On board DC/DC >
60-264V (AC)(DC)
(DC)
(DC)
(DC)
(DC)
•Plug-and-play of power
•Unprecedented power quality
•Isolation of load dynamics by POL
(Point of Load) converters
4
POLs
Energy Internet: An open and transactive electricity market
Distribution Grid of the Future
Power
Factor
Correction
DC/DC
Converter
Load
Renewable
Energy
Generation
Energy
Storage
Others
MV DC
< Front end AC/DC >
4160-69 kV (AC))
LV DC
Direct MV Power Conversion:
•Ability to achieve power conversion
without 60 Hz transformer
•Silicon Carbide technology is within
reach in the 4160-15 kV class range
Inverter LV AC
5
Energy Internet: An open and transactive electricity market
Voltage (kV)
6
SiC p-
ETO
15
20
2 20 40
10
Silicon
Switching frequency (kHz)
SiC MOSFET
SiC n-IGBT
300 MHz-V
600 MHz-V(ZVS)
5 MHz-V
40 MHz-V
Medium Voltage SiC Technology
Using SiC MOSFET
• 60 to 120 X improvements in
V-f capability
Enables MV & HF power
conversion
Energy Internet: An open and transactive electricity market
FREEDM System for Energy Internet
Bi-directional flow
2. Solid State Transformer
(Energy Router)
380 VDC Bus
7
Proposed by Dr. Huang in 2007
Storage DG
1. Plug & play interface
1. Plug & play interface
Plug-and-play DC Microgrid
(Energy Cell)
software
Energy Internet: An open and transactive electricity market 8
DC FREEDM System
Plug-and-play DC Microgrid
(Energy Cell)
Storage DG
Energy Internet: An open and transactive electricity market 9
DC Microgrid (Energy Cell) Advantage
AC & DC microgrid
AC microgridSST interfaced DC microgrid
SST
1) higher efficiency;
2) better to power homes’ DC loads
3) no harmonic and reactive power factors
AC busDC bus
DC/AC DC/AC
Energy Internet: An open and transactive electricity market
Resilient Grid: Autonomous and Distributed Power Management Control
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Mode I:
FREEDM system
in grid-connected
Mode II:
FREEDM system
in islanding
Mode III:
SST in
islanding
Substation SST detects
grid faults and disconnects
MVAC bus under frequency
Substation SST synchronizes MVAC bus to
grid and connects
Substation SST restores MVAC bus and SSTs
reconnects
Rectifier stage
DC/DC
BatterySST2
FREEDM MV Feeder
droop
SST1
MPPT Controller
AC Load
droop droop
AC
Load
DC
Microgrid
Transmission Grid
Substation SST
DC/ACAC/DC
IPM Command
via DGI
QHVref
VMVref
fMVref
VMV, fMV
PSST1
QSST1
VMV fMV
QSST1 PSST1
PSST2
QSST2
QMVref
VhdcrefVMV
VHV, fHV
Vhdc
fMV
PMVref
Vldcref
droop
droop
Vldc
ωref
Vlac_dref
Vlac
droop
Vldc Pbat
Pref(IPM)
IEM Command
via DGI
Pbatref
Pref(IEM)SOC
PV
droop
Vldc
Pdroop
PPV
PMPPTVPV
IPV
Vldc
Load
D: Load shedding
PLoad
DC Microgrid FeederBlue: sampling signals for IPM
Green: controllable/reference
signals for IPM Inverter
Min
FREEDM SYSTEM
C: DRER control
OR
B: DESD control
A: SST droop
f
no
shedding
vldc vldc vldc vldc
P P P0
380
Pbat_max0 0
A:SST B:DESD C:DRER D:Load
PPV_max
MPPT
360
400
Pbat_min
385
375
390
0 PL_maxPL_min
370
365
I E M382
378
fmin fmax60
Energy Internet: An open and transactive electricity market
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Solid State Transformer
Functional Diagram
SST
Medium Voltage AC
(or Medium Voltage DC)
LV DC
LVAC 2LVAC 1
Software Communication
•Power Management:
•Change/Control the customer
voltage levels
•Provide DC power
•Control power factor
•Disconnect from grid under fault
•Limiting fault current
•Eliminate customer side harmonics
•Low voltage ride through
•Supports multiple islanding modes
•Energy Management
•Monitor energy usage
•Smart agent for energy transaction
•Can control/dispatch power via
microgrids (Energy Cell)
•Demand side management
Energy Internet: An open and transactive electricity market 12
MV AC voltage sag operation: 25% voltage sag, 5KW
Input voltage, current, PWM voltage, high voltage DC link 3Output DC voltage, AC voltage and current
Gen-I SST
120V AC
3.6 kV AC
5 kW LOAD
Energy Internet: An open and transactive electricity market
SST Integration with a Non-linear Load: Harmonic Mitigation
13
Gen-II SST
120V AC
1.8 kV AC
Non linear LOAD
LV AC load current
HV AC load current
Note: Output AC phase is 180 shifted with the HV AC
LV AC Voltage
0 1000 2000 3000 4000 5000 6000
HV AC Current Harmonics
Energy Internet: An open and transactive electricity market
Energy Internet Technology Needs
1) Plug-and-Play Interface
(RJ45, USB)
2) Router
3)Open Standard Protocol and
Operation System
(TCP/IP, HTML)
4) Data Storage
5) WWW/eBay/Twitter/Facebook
Internet/Computer
1) Plug-and-play DC and AC
Energy Cell protocol
2) Solid State Transformer
(with embedded software)
3) Software platform?
4) Distributed storage
5) Market/business framework
Energy Internet
14
Energy Internet: An open and transactive electricity market
Key Challenge: Software Platform
High-volume
High-velocity
Expensive
Single point of failure
Not easy to expand
Highly complex
……
Centralized Data Storage and
Processing
……
Energy Cell #1
SST1 SST2 SSTn
Energy Cell #2
Energy Cell #n
Energy Internet: An open and transactive electricity market
……
Energy Cell #1
SST1 SST2 SSTn
Energy Cell #2
Energy Cell #n
Operation View
1. Real-time Energy Cell Data Collection: Open Standard and Plug-and-Play
2. Distributed Data Storage and Management
3. Open-source Programming & Open API
Cost-effective
Scalable
Fast
Resilient to failure
Flexible
Easy to use
……
Distributed Data Storage and Processing
Energy Internet: An open and transactive electricity market
Proof-of-Concept Platform
…… ……
16 of low-cost single
board PCs (e.g.,
CubieBoard)
• High-availability distributed object-oriented platform
• Google’s MapReduce and Google File System
Simulated PV data is implemented into Lego
Mindstorm EV3 Intelligent Brick (ARM 9 processor
with Linux-based operating system)
Energy Cell
Layer
SST
Software
Layer
……
…
Energy Internet: An open and transactive electricity market
Efficient
Allows parallel data processing over a large amount of PV data
Reduce overall processing time through parallel & faster execution
Efficient Data Management
0
100
200
300
400
500
600
700
Pro
cess
ing
tim
e (S
ecs)
Data Size (MB)
trial 1 trial 2 trial 3 trial 4
0
1000
2000
3000
4000
5000
6000
7000
Tota
l Pro
cess
ing
Tim
e (S
)
Data Size (MB)
Distributed Conventional
Total processing times using the distributed data management systems over different data size and
trials
Comparison on average data processing time
using distributed and conventional data
management systems
Energy Internet: An open and transactive electricity market
Energy Cell #1:
Cost functions Comfort level
Customer preference
Load demand
Local regulation and policy
Local operational constraints Bidding/offer strategy
……
Utility Cell:
Cost functions (supply curve)
Electricity transaction
Ancillary services
Power flow (global) constraints
Environment:
Social impact
Government policy
Environmental incentives
Renewable energy forecast
……
...
Energy Cell #2 Energy Cell #N
min ( )i iF U
Market Clearing House:
Collect bid and offer from cells
Find Nash equilibrium points
Clear the market price
Regulate the deregulated
electricity market
Pi is the net power demand
of the i-th energy cell
1 1
( )N N
i i
i i
P P
λ is the retailed electricity price
for customers within a same
distribution system
( )i i iP f U
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Energy Internet Market Framework: Energy eBay
Energy Internet: An open and transactive electricity market
The Proposed Market Clearing Scheme
Start
Initialization with PLoss and x0
Iter1 = Iter2 = k = 0
Max ѱ(xk,y) in to find yi subject to local constraints
Run power flow in OpenDSS with yi and calculate the new PLoss
Calculate and update PLoss
Iter2 = Iter2+1
End
No
Yes
ΔPLoss< ɛ
Iter1 = Iter2 = 0
Apply relaxation algorithm to obtain new xk
Z(x) < ɛNo
Yes
k = k +1
Check solution feasibility
yi (Iter1) = yi (Iter1-1)+ΔW
Iter1 = Iter1+1No
Yes
A Modified IEEE Distribution Test Feeder
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Need game-theoretical algorithms to clear the
electricity market price
Energy Internet Clearing House
Energy Internet: An open and transactive electricity market
21
Matlab/Simulink-based Testbed
Energy Internet Market Framework
Energy Internet: An open and transactive electricity market
Objective Values $
Type 1 Energy cell Type 2 Utility Cell
Step k Bus 645 Bus 671 Bus 675 Bus 634 Bus 650
1 -165.04 -3403.7 -4667.2 -1794.1 4007.9
2 420.09 -2632.7 -3642.7 -1684.2 6514.7
3 707.89 -2226.7 -3342.3 -1605.4 7673.6
4 834.51 -2020.9 -3162.5 -1580.9 8179.4
5 908.73 -1901.0 -3157.0 1556.9 8444.7
: : : : : :
15 993.86 -1726.5 -3328.6 -1529.5 8808.9
16 993.96 -1726.0 -3330.3 -1529.4 8810.1
17 994.05 -1725.8 -3331.5 -1529.3 8810.8
Nikaido-Isoda Function Values
Pay-off Function Values 22
*
*
,
max , 0.x y X
x y
Energy Internet Market Framework
Nikaido-Isoda function reaches zero, no
player can increase its payoffs by
unilaterally changing its strategy (demand
or supply). Therefore, the Nikaido-Isoda
function can approximately approach a
Nash equilibrium point.
Energy Internet: An open and transactive electricity market
One example of industry implementing evolutionary tech:
www.grid-bridge.com
Energy Internet: An open and transactive electricity market
ConclusionsEnergy Internet Concept is discussed
– A totally open energy market supports the energy transaction of all types of Energy Cells
– A resilient and plug-and-play capable grid is a prerequisite for realizing energy internet. Power electronics plays a key role in achieving this goal
– Distributed and secure software platform to support large and distributed data monitoring and application
– Business model of the energy internet will be more and more like an Energy eBay. Example of using game theory to clear every Energy Cell’s bidding is shown
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