Ninth Annual Carnegie Mellon Conference on the Electricity Industry
Role of Coordination in Resilient & Fine-Grain Control of Power Grids
February 4-5, 2014
Prosumer-Based Decentralized Cyber-Physical
Architecture for Green Electricity Internetworks
Santiago Grijalva
Director, Power System Engineering Center, NREL
Associate Professor, Georgia Institute of Technology (on leave)
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The Emerging Grid
Natural Gas
Generators
Nuclear Power
Plants
Transmission
System
Distributed
storage
Distributed
wind
Rooftop
Solar
Smart Grid functionality restores the
balance
Hydro power
plants
Distribution
Substations
PHEV
Home
Energy
Customers
Storage
Energy
Efficiency
Wind Farms
Solar Farms
Commercial
Customers
2 © 2014 Georgia Institute of Technology
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Core Trends and Paradigms
Domain
Trend or Paradigm Change
Future System
Objectives
• Reliability and Economy + Sustainability
Sustainable
Sources
•  From fossil fuel to renewable
• From bulk centralized to distributed
• Highly Variable
Renewable
Distributed
Stochastic
Information
• Can control entire system through SW
• Increased digital control ->
• Privacy and cyber-security issues
Cyber-Controlled
Cyber-Physical
Private
Actors
• Consumers can also produce and store
• Consumers seek their own objectives
• Massive number of actors and devices
Prosumers
Smart
Scalable
Carriers
• Interdependencies with other systems
Integrated
Prosumer-Based Decentralized Cyber-Physical Control and
Management Architecture for Green Electricity Internetworks
3 © 2014 Georgia Institute of Technology
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Georgia Tech ARPA-E GENI Project
Investigators:
Santiago Grijalva, Magnus Egerstedt, Marilyn Wolf, Shabbir Ahmed.
Objectives: Develop and demonstrate at large-scale:
1. A control and management architecture that will allow the
electricity industry to operate with characteristics similar to
the internet: Distributed, Flat, Layered, Scalable
2. A distributed services cyber-infrastructure that supports
prosumer interaction. This cyber-infrastructure can be
understood as an “Electricity Operating System”.
3. A real-time decentralized prosumer frequency controller
4. A decentralized prosumer energy scheduler
4 © 2014 Georgia Institute of Technology
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Architecture: Prosumer Abstraction
External
Supply
Energy
Storage
Local
Energy
Wires
Load 1
Load 2
....
Load n
•
A generic model that captures basic functions (produce, consume,
store) can be applied to power systems at any scale.
•
The fundamental task is power balancing:
PINT  PG  PD  PLoss  PSTO   PSTO 
•
Energy services can be virtualized.
5 © 2014 Georgia Institute of Technology
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Architecture: Flat Electricity Industry
Interconnection
ISO
Utility
Grid, Building, Home
•
•
Interactions occur among entities of the same type (prosumers)
Can achieve “flatness”
6 © 2014 Georgia Institute of Technology
S. Grijalva, "Multi-Scale, Multi-Dimensional Computational Algorithms for Next
Generation Electric Power Grid", DOE Workshop on Computational Needs for Next
Generation Electric Power Grid, Cornell University, Ithaca, NY, April 18-20, 2011.
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Architecture: Prosumer Interactions
• Interactions will leverage recent
developments in networked and
autonomous control.
S. Grijalva, M. Costley, "Prosumer-Based Smart Grid Architecture Enables a Flat, Sustainable
Electricity Industry", IEEE PES Conference on Innovative Smart Grid Technologies (ISGT),
Anaheim, California, January 17-19, 2011.
7 © 2014 Georgia Institute of Technology
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Architecture: Cyber-Physical Layered Model
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Prosumer Power Agreement
Prosumer States
pˆ i : Desired Power
p i : Agreed Upon Power
pi : Actual Power
q (t  1)  q (t )  t[ LWLq (t )  WLpˆ ]
Given desired power levels, how to agree on
N
power outputs?
min  wi || p i  pˆ i ||2
p
i 1
An agreement dynamics, incorporating
constraints, weights, and trust, is used to agree
on the power levels across the network in a
decentralized fashion.
 


qi (t  1)  qi (t )  t    wi  (qi (t )  qk (t ))  w j  (qk (t )  q (t ))   wi  ( pˆ i  pˆ j ) 
N k
jN i

 jNi  kNi

p i 
p
jN i
ij
Converges asymptotically to
the global minimizer
(exponentially in the
algebraic connectivity of the
network)
Ramachandran, Costello, Kingston, Grijalva, Egerstedt. “Distributed Power
Allocation in Prosumer Networks”, NecSys, 2012.
9 © 2014 Georgia Institute of Technology
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Malicious/Malfunctioning Prosumer
•
Linearize dynamics:
??
•
On state-space form:
•
Project the (asymptotically
stable) dynamics and evaluate
z “after a while” and solve for d:
•
Can evaluate x in a distributed
way:
10 © 2014 Georgia Institute of Technology
Unstable!
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Decentralized Control
Hardware Demonstrations
N. Ainsworth, M. Costley, J. Thomas, M. Jezierny, S. Grijalva: "Versatile
Autonomous Smartgrid Testbed (VAST): A Flexible, Reconfigurable Testbed for
Research on Autonomous Control for Critical Electricity Grids", in Proceedings of
the North American Power Symposium, Champaign, IL, September 9-11, 2012.
11 © 2014 Georgia Institute of Technology
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Decentralized Frequency Regulation
• Model Predictive Control solvable in a distributed manner.
• Each prosumer solves its sub-problem and shares its
optimal control strategy with its neighbors.
n
2
min   pi xi (tc  1) 2  ru
i i 
u1 ,...,un
i 1
s.t. : xi (tc  1)  aii xi (tc )  bii ui (tc )
  jN  aij x j (tc )  bij u j (tc ) 
• Prosumer i strategy:
k 1
i
u

2
 arg min  ru
i i  pi aii xi  bii ui   jN ( aij x j  bij u j
i

12 © 2014 Georgia Institute of Technology

2



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Decentralized Energy Scheduling
• 1,500+ Generator case
• Full UC realistic data.
13 © 2014 Georgia Institute of Technology
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Further Elements for De-centralized
Control
Requirement
Theory
Synchronization/
stabilization
Decentralized controller for nonlinear coupled
oscillators
Effect of losses
Bi-directed graphs and non-odd functions
Voltage Stability
Locally enforceable necessary condition
Transient Stability
Locally enforceable sufficient condition
Flow Constraints
Distributed enforcement of coupling constraints
14 © 2014 Georgia Institute of Technology
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Decentralized Computing Infrastructure
M.U. Tariq, S. Grijalva, M. Wolf, "Towards a Distributed, Service-Oriented Control
Infrastructure for Smart Grid", ACM/IEEE Second International Conference on Cyber-Physical
Systems, Chicago, IL, April 11-14, 2011.
15 © 2014 Georgia Institute of Technology
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Demonstration System
Prosumer Computational Node Instance
Estimator, SA, Scheduler, etc.
Market
Market Conditions
System Control
System Conditions
Electricity Operating .
System
CPS
Conditions
Communication Network Simulator
Network Conditions
ISO/Utility Data
Scenario Generator
Data Organization
and Processing
Device Local Control
…
Power System Devices
Prosumer Grid Data Instance
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Grid Conditions
Simulation Testbed
OSI Soft
Database
Prosumer
Data Instance
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Decentralized Control: Large-Scale
Systems
• 20 Self-Optimizing Regions in a Large-Scale RTO System.
• Non-fictitious Tie-Line Bus LMP Difference Convergence
obtained using Distributed Optimization.
M. Costley, S. Grijalva, “Efficient Distributed OPF for De-centralized Power System Operations and Electricity
Markets”, IEEE PES Conference on Innovative Smart Grid Technologies, Washington D.C., January 17-19, 2012.
17 © 2014 Georgia Institute of Technology
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Decentralized Control: Large-Scale
Systems
PSE&G
PENELEC
RECO
UGI
CE
PJM
FE
PPL
AE
DLCO
AP
JCP&L
METED
PECO
BGE
DAY
IPRV
DP&L
PEPCO
DEO&K
AEP
A
98%
M W
EKPC
18 © 2014 Georgia Institute of Technology
DVP
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Multi-Scale Prosumer Behavior
• Prosumer exposes
standardized services
–
–
–
–
–
–
19 © 2014 Georgia Institute of Technology
Energy balancing
Frequency regulation
Reserve
Sensing and Information
Forecasting
Security
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Decentralized Building Control
LMP $/MWh
Node
Iteration
a) Building prosumer interaction at
transformer connection point for a
constrained grid.
20 © 2014 Georgia Institute of Technology
b) Voltage contouring for PV variability
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Summary
• Future electricity systems will consist of billions of smart
devices and millions of interconnected decision makers.
• Only a decentralized control and management architecture
will be able to support the objectives and requirements of the
future electricity industry.
THANKS!
21 © 2014 Georgia Institute of Technology
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