Lecture given at MIT May 6, 2014 (shorter version given at ITA UCSD on Valentines Day 2014).
Based on joint research with Ana Busic, Prabir Barooah, Jordan Erhan, and Yue Chen, contained in three papers at http://www.meyn.ece.ufl.edu/pp
Renewable energy sources such as wind and solar power have a high degree of unpredictability and time-variation, which makes balancing demand and supply challenging. One possible way to address this challenge is to harness the inherent flexibility in demand of many types of loads.
At the grid-level, ancillary services may be seen as actuators in a large disturbance rejection problem. It is argued that a randomized control architecture for an individual load can be designed to meet a number of objectives: The need to protect consumer privacy, the value of simple control of the aggregate at the grid level, and the need to avoid synchronization of loads that can lead to detrimental spikes in demand.
I will describe new design techniques for randomized control that lend themselves to control design and analysis. It is based on the following sequence of steps:
1. A parameterized family of average-reward MDP models is introduced whose solution defines the local randomized policy. The balancing authority broadcasts a common real-time control signal to the loads; at each time, each load changes state based on its own current state and the value of the common control signal.
2. The mean field limit defines an aggregate model for grid-level control. Special structure of the Markov model leads to a simple linear time-invariant (LTI) approximation. The LTI model is passive when the nominal Markov model is reversible.
3. Additional local control is used to put strict bounds on individual quality of service of each load, without impacting the quality of grid-level ancillary service.
Examples of application include chillers, flexible manufacturing, and even residential pool pumps. It is shown through simulation how pool pumps in Florida can supply a substantial amount of the ancillary service needs of the Eastern U.S.
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Distributed Randomized Control for Ancillary Service to the Power Grid
1. Distributed Randomized Control
for Ancillary Service to the Power Grid
With application to rational pools
LIDS Seminar May 6, 2014
Ana Buˇsi´c and Sean Meyn
Prabir Barooah, Yue Chen, and Jordan Ehren
TREC & D´epartement d’Informatique
INRIA & ENS
Electrical and Computer Engineering
University of Florida
Thanks to NSF, AFOSR, ANR, and DOE / TCIPG
2. Outline
1 Distributed Control of Loads
2 Design for Intelligent Loads
3 Linearized Dynamics and Passivity
4 One Million Pools
5 Conclusions and Extensions
6 References
0 / 28
4. Distributed Control of Loads
Power grid as a feedback control system
Massive disturbance rejection problem
One day in Gloucester:
1 / 28
5. Distributed Control of Loads
Power grid as a feedback control system
Massive disturbance rejection problem
Two typical weeks in the Pacific Northwest (BPA):
0
2
4
6
8
2
4
6
8
0
0.8
-0.8
1
-1
0
0.8
-0.8
1
-1
0
Sun Mon Tue
October 20-25 October 27 - November 1
Hydro
Wed Thur FriSun Mon Tue Wed Thur Fri
GenerationandLaodGW
GWGW
RegulationGW
Thermal
Wind
Load
Generation
Regulation
1 / 28
6. Distributed Control of Loads
Control of Deferrable Loads
Control Goals and Architecture
Power GridControl WaterPump
Batteries
Coal
GasTurbine
BP
BP
BP C
BP
BP
Voltage
Frequency
Phase
HC
Σ
−
Actuator feedback loop
A
LOAD
Context: Consider population of similar loads that are deferrable.
Two examples of flexible energy hogs:
Chillers in HVAC systems and residential pool pumps
2 / 28
7. Distributed Control of Loads
Control of Deferrable Loads
Control Goals and Architecture
Power GridControl WaterPump
Batteries
Coal
GasTurbine
BP
BP
BP C
BP
BP
Voltage
Frequency
Phase
HC
Σ
−
Actuator feedback loop
A
LOAD
Context: Consider population of similar loads that are deferrable.
Two examples of flexible energy hogs:
Chillers in HVAC systems and residential pool pumps
Control Constraints:
Grid operator demands reliable ancillary service;
Consumers demand reliable service (and more)
2 / 28
8. Distributed Control of Loads
One Million Pools in Florida
Pools Service the Grid Today
On Call1: Utility controls residential pool pumps and other loads
1
Florida Power and Light, Florida’s largest utility.
www.fpl.com/residential/energysaving/programs/oncall.shtml
3 / 28
9. Distributed Control of Loads
One Million Pools in Florida
Pools Service the Grid Today
On Call1: Utility controls residential pool pumps and other loads
Contract for services: no price signals involved
Used only in times of emergency — Activated only 3-4 times a year
1
Florida Power and Light, Florida’s largest utility.
www.fpl.com/residential/energysaving/programs/oncall.shtml
3 / 28
10. Distributed Control of Loads
One Million Pools in Florida
Pools Service the Grid Today
On Call1: Utility controls residential pool pumps and other loads
Contract for services: no price signals involved
Used only in times of emergency — Activated only 3-4 times a year
Opportunity:
FP&L already has their hand on the switch of nearly one million pools!
1
Florida Power and Light, Florida’s largest utility.
www.fpl.com/residential/energysaving/programs/oncall.shtml
3 / 28
11. Distributed Control of Loads
One Million Pools in Florida
Pools Service the Grid Today
On Call1: Utility controls residential pool pumps and other loads
Contract for services: no price signals involved
Used only in times of emergency — Activated only 3-4 times a year
Opportunity:
FP&L already has their hand on the switch of nearly one million pools!
Surely pools can provide much more service to the grid
1
Florida Power and Light, Florida’s largest utility.
www.fpl.com/residential/energysaving/programs/oncall.shtml
3 / 28
12. Distributed Control of Loads
One Million Pools in Florida
Pools Service the Grid Today
On Call1: Utility controls residential pool pumps and other loads
Contract for services: no price signals involved
Used only in times of emergency — Activated only 3-4 times a year
Opportunity:
FP&L already has their hand on the switch of nearly one million pools!
Surely pools can provide much more service to the grid
Summary (beyond pools):
For many household loads, contracts with consumers are already in place
1
Florida Power and Light, Florida’s largest utility.
www.fpl.com/residential/energysaving/programs/oncall.shtml
3 / 28
13. Distributed Control of Loads
One Million Pools in Florida
Pools Service the Grid Today
On Call1: Utility controls residential pool pumps and other loads
Contract for services: no price signals involved
Used only in times of emergency — Activated only 3-4 times a year
Opportunity:
FP&L already has their hand on the switch of nearly one million pools!
Surely pools can provide much more service to the grid
Summary (beyond pools):
For many household loads, contracts with consumers are already in place
For other loads, such as plug-in electric vehicles (PEVs),
consumer risk may be too great.
1
Florida Power and Light, Florida’s largest utility.
www.fpl.com/residential/energysaving/programs/oncall.shtml
3 / 28
14. Distributed Control of Loads
Control of Deferrable Loads
Randomized Control Architecture
Context: Consider population of similar loads that are deferrable.
Constraints: Grid operator demands reliable ancillary service; Consumer demands
reliable service
Control strategy
Requirements:
4 / 28
15. Distributed Control of Loads
Control of Deferrable Loads
Randomized Control Architecture
Context: Consider population of similar loads that are deferrable.
Constraints: Grid operator demands reliable ancillary service; Consumer demands
reliable service
Control strategy
Requirements:
1. Minimal communication: Each load should know the needs of the
grid, and the status of the service it is intended to provide.
4 / 28
16. Distributed Control of Loads
Control of Deferrable Loads
Randomized Control Architecture
Context: Consider population of similar loads that are deferrable.
Constraints: Grid operator demands reliable ancillary service; Consumer demands
reliable service
Control strategy
Requirements:
2. Smooth behavior of the aggregate
=⇒ Randomization
4 / 28
17. Distributed Control of Loads
Control of Deferrable Loads
Randomized Control Architecture
Control strategy
Requirements:
1. Minimal communication: Each load should know the needs of the
grid, and the status of the service it is intended to provide.
2. Smooth behavior of the aggregate
=⇒ Randomization
Need: A practical theory for distributed control based on this architecture
For recent references see thesis of J. Mathieu
4 / 28
18. Distributed Control of Loads
Example: One Million Pools in Florida
How Pools Can Help Regulate The Grid
1,5KW 400V
Needs of a single pool
Filtration system circulates and cleans: Average pool pump uses
1.3kW and runs 6-12 hours per day, 7 days per week
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19. Distributed Control of Loads
Example: One Million Pools in Florida
How Pools Can Help Regulate The Grid
1,5KW 400V
Needs of a single pool
Filtration system circulates and cleans: Average pool pump uses
1.3kW and runs 6-12 hours per day, 7 days per week
Pool owners are oblivious, until they see frogs and algae
5 / 28
20. Distributed Control of Loads
Example: One Million Pools in Florida
How Pools Can Help Regulate The Grid
1,5KW 400V
Needs of a single pool
Filtration system circulates and cleans: Average pool pump uses
1.3kW and runs 6-12 hours per day, 7 days per week
Pool owners are oblivious, until they see frogs and algae
Pool owners do not trust anyone: Privacy is a big concern
5 / 28
21. Distributed Control of Loads
Example: One Million Pools in Florida
How Pools Can Help Regulate The Grid
1,5KW 400V
Needs of a single pool
Filtration system circulates and cleans: Average pool pump uses
1.3kW and runs 6-12 hours per day, 7 days per week
Pool owners are oblivious, until they see frogs and algae
Pool owners do not trust anyone: Privacy is a big concern
Randomized control strategy is needed.
5 / 28
22. yt
Control @ Utility
Gain
One Million Pools
Disturbance to be rejected
Proportion of pools on
desired
ζt
d
dt
µt = µtDζt yt = µt, U
Intelligent Appliances
23. Distributed Control of Loads
General Model
Controlled Markovian Dynamics
Assumptions
1 Continuous-time model on finite state space X
2 Controlled Markovian generator Dζ(x, y) : x, y ∈ X, ζ ∈ R.
6 / 28
24. Distributed Control of Loads
General Model
Controlled Markovian Dynamics
Assumptions
1 Continuous-time model on finite state space X
2 Controlled Markovian generator Dζ(x, y) : x, y ∈ X, ζ ∈ R.
D = D0 models nominal behavior of load.
6 / 28
25. Distributed Control of Loads
General Model
Controlled Markovian Dynamics
Assumptions
1 Continuous-time model on finite state space X
2 Controlled Markovian generator Dζ(x, y) : x, y ∈ X, ζ ∈ R.
D = D0 models nominal behavior of load.
3 Smooth and Lipschitz: For a constant ¯b,
d
dζ
Dζ(x, y) ≤ ¯b, for x, y ∈ X, ζ ∈ R.
6 / 28
26. Distributed Control of Loads
General Model
Controlled Markovian Dynamics
Assumptions
1 Continuous-time model on finite state space X
2 Controlled Markovian generator Dζ(x, y) : x, y ∈ X, ζ ∈ R.
D = D0 models nominal behavior of load.
3 Smooth and Lipschitz: For a constant ¯b,
d
dζ
Dζ(x, y) ≤ ¯b, for x, y ∈ X, ζ ∈ R.
4 Utility function U : X → R
represents state-dependent power consumption
6 / 28
27. Distributed Control of Loads
General Model
Controlled Markovian Dynamics
Assumptions
1 Continuous-time model on finite state space X
2 Controlled Markovian generator Dζ(x, y) : x, y ∈ X, ζ ∈ R.
D = D0 models nominal behavior of load.
Each load is subject to common controlled Markovian dynamics.
For the ith load,
P{Xi
(t + s) = x+
| Xi
(t) = x−
} ≈ sDζt (x−
, x+
) + O(s2
)
6 / 28
28. Distributed Control of Loads
General Model
Mean Field Model
Aggregate model: N loads running independently,
each under the command ζ.
Empirical Distributions:
µN
t (x) =
1
N
N
i=1
I{Xi
(t) = x}, x ∈ X
7 / 28
29. Distributed Control of Loads
General Model
Mean Field Model
Aggregate model: N loads running independently,
each under the command ζ.
Empirical Distributions:
µN
t (x) =
1
N
N
i=1
I{Xi
(t) = x}, x ∈ X
Limiting model:
d
dt
µt(x ) =
x∈X
µt(x)Dζt (x, x ), yt :=
x
µt(x)U(x)
via Law of Large Numbers for martingales
7 / 28
30. Distributed Control of Loads
General Model
Mean Field Model
Aggregate model: N loads running independently,
each under the command ζ.
Empirical Distributions:
µN
t (x) =
1
N
N
i=1
I{Xi
(t) = x}, x ∈ X
Mean-field model:
d
dt
µt = µtDζt , yt = µt(U)
ζt = ft(µ0, . . . , µt) by design
7 / 28
31. Distributed Control of Loads
General Model
Mean Field Model
Mean-field model:
d
dt
µt = µtDζt , yt = µt(U)
ζt = ft(µ0, . . . , µt) by design
yt
Control @ Utility
Gain
N Loads
Disturbance to be rejected
desired
ζt
µt+1 = µtPζt
yt = µt, U
Questions: 1. How to control this complex nonlinear system? CDC 2013
8 / 28
32. Distributed Control of Loads
General Model
Mean Field Model
Mean-field model:
d
dt
µt = µtDζt , yt = µt(U)
ζt = ft(µ0, . . . , µt) by design
yt
Control @ Utility
Gain
N Loads
Disturbance to be rejected
desired
ζt
µt+1 = µtPζt
yt = µt, U
Questions: 1. How to control this complex nonlinear system? CDC 2013
2. How to design {Dζ} so that control is easy?
8 / 28
33. Distributed Control of Loads
General Model
Mean Field Model
Mean-field model:
d
dt
µt = µtDζt , yt = µt(U)
ζt = ft(µ0, . . . , µt) by design
yt
Control @ Utility
Gain
N Loads
Disturbance to be rejected
desired
ζt
µt+1 = µtPζt
yt = µt, U
Questions: 1. How to control this complex nonlinear system? CDC 2013
2. How to design {Dζ} so that control is easy? focus here
8 / 28
35. Design for Intelligent Loads
Mean Field Model
Design via “Bellman-Shannon” Optimal Control
Goal: Construct a family of generators {Dζ : ζ ∈ R}.
9 / 28
36. Design for Intelligent Loads
Mean Field Model
Design via “Bellman-Shannon” Optimal Control
Goal: Construct a family of generators {Dζ : ζ ∈ R}.
Design: Consider first the finite-horizon control problem:
Choose distribution pζ to maximize
1
T
ζEpζ
T
t=0
U(Xt) − D(pζ p0)
D denotes relative entropy.
p0 denotes nominal Markovian model.
9 / 28
37. Design for Intelligent Loads
Mean Field Model
Design via “Bellman-Shannon” Optimal Control
Goal: Construct a family of generators {Dζ : ζ ∈ R}.
Design: Consider first the finite-horizon control problem:
Choose distribution pζ to maximize
1
T
ζEpζ
T
t=0
U(Xt) − D(pζ p0)
D denotes relative entropy.
p0 denotes nominal Markovian model.
Explicit solution for finite T:
p∗
ζ(xT
0 ) ∝ exp ζ
T
t=0
U(xt) dt p0(xT
0 )
9 / 28
38. Design for Intelligent Loads
Mean Field Model
Design via “Bellman-Shannon” Optimal Control
Explicit solution for finite T:
p∗
ζ(xT
0 ) ∝ exp ζ
T
t=0
U(xt) dt p0(xT
0 )
9 / 28
39. Design for Intelligent Loads
Mean Field Model
Design via “Bellman-Shannon” Optimal Control
Explicit solution for finite T:
p∗
ζ(xT
0 ) ∝ exp ζ
T
t=0
U(xt) dt p0(xT
0 )
Markovian, but not time-homogeneous.
As T → ∞, we obtain generator Dζ
9 / 28
40. Design for Intelligent Loads
Mean Field Model
Design via “Bellman-Shannon” Optimal Control
Explicit solution for finite T:
p∗
ζ(xT
0 ) ∝ exp ζ
T
t=0
U(xt) dt p0(xT
0 )
As T → ∞, we obtain generator Dζ
Simple construction via eigenvector problem:
9 / 28
41. Design for Intelligent Loads
Mean Field Model
Design via “Bellman-Shannon” Optimal Control
Explicit solution for finite T:
p∗
ζ(xT
0 ) ∝ exp ζ
T
t=0
U(xt) dt p0(xT
0 )
As T → ∞, we obtain generator Dζ
Simple construction via eigenvector problem:
Dζ(x, y) =
v(y)
v(x)
ζU(x) − Λ + D(x, y)
9 / 28
42. Design for Intelligent Loads
Mean Field Model
Design via “Bellman-Shannon” Optimal Control
Explicit solution for finite T:
p∗
ζ(xT
0 ) ∝ exp ζ
T
t=0
U(xt) dt p0(xT
0 )
As T → ∞, we obtain generator Dζ
Simple construction via eigenvector problem:
Dζ(x, y) =
v(y)
v(x)
ζU(x) − Λ + D(x, y)
where Dv = Λv, D(x, y) = ζU(x) + D(x, y)
Extension/reinterpretation of [Todorov 2007] ⊕ Kontoyiannis & M 200X
9 / 28
43. d
dt
µt = µtDζt
yt = µt, U
d
dt
Φt = AΦt + Bζt
γt = CΦt
Linearized Dynamics
44. Linearized Dynamics and Passivity
Mean Field Model
Linearized Dynamics
Mean-field model: d
dt µt = µtDζt , yt = µt(U)
Linear state space model:
Φt+1 = AΦt + Bζt
γt = CΦt
10 / 28
45. Linearized Dynamics and Passivity
Mean Field Model
Linearized Dynamics
Mean-field model: d
dt µt = µtDζt , yt = µt(U)
Linear state space model:
Φt+1 = AΦt + Bζt
γt = CΦt
Interpretations: |ζt| is small, and π denotes invariant measure for D.
10 / 28
46. Linearized Dynamics and Passivity
Mean Field Model
Linearized Dynamics
Mean-field model: d
dt µt = µtDζt , yt = µt(U)
Linear state space model:
Φt+1 = AΦt + Bζt
γt = CΦt
Interpretations: |ζt| is small, and π denotes invariant measure for D.
• Φt ∈ R|X|, a column vector with
Φt(x) ≈ µt(x) − π(x), x ∈ X
10 / 28
47. Linearized Dynamics and Passivity
Mean Field Model
Linearized Dynamics
Mean-field model: d
dt µt = µtDζt , yt = µt(U)
Linear state space model:
Φt+1 = AΦt + Bζt
γt = CΦt
Interpretations: |ζt| is small, and π denotes invariant measure for D.
• Φt ∈ R|X|, a column vector with
Φt(x) ≈ µt(x) − π(x), x ∈ X
• γt ≈ yt − y0; deviation from nominal steady-state
10 / 28
48. Linearized Dynamics and Passivity
Mean Field Model
Linearized Dynamics
Mean-field model: d
dt µt = µtDζt , yt = µt(U)
Linear state space model:
Φt+1 = AΦt + Bζt
γt = CΦt
Interpretations: |ζt| is small, and π denotes invariant measure for D.
• Φt ∈ R|X|, a column vector with
Φt(x) ≈ µt(x) − π(x), x ∈ X
• γt ≈ yt − y0; deviation from nominal steady-state
• A = DT
, Ci = U(xi), and input dynamics linearized:
10 / 28
49. Linearized Dynamics and Passivity
Mean Field Model
Linearized Dynamics
Mean-field model: d
dt µt = µtDζt , yt = µt(U)
Linear state space model:
Φt+1 = AΦt + Bζt
γt = CΦt
Interpretations: |ζt| is small, and π denotes invariant measure for D.
• Φt ∈ R|X|, a column vector with
Φt(x) ≈ µt(x) − π(x), x ∈ X
• γt ≈ yt − y0; deviation from nominal steady-state
• A = DT
, Ci = U(xi), and input dynamics linearized:
BT
=
d
dζ
πDζ
ζ=0
10 / 28
50. Linearized Dynamics and Passivity
Linearized Dynamics
Transfer Function
Linear state space model:
Φt+1 = AΦt + Bζt
γt = CΦt A = DT
, Ci = U(xi
), BT
=
d
dζ
πDζ
ζ=0
11 / 28
51. Linearized Dynamics and Passivity
Linearized Dynamics
Transfer Function
Linear state space model:
Φt+1 = AΦt + Bζt
γt = CΦt A = DT
, Ci = U(xi
), BT
=
d
dζ
πDζ
ζ=0
Transfer Function:
G(s) = C[Is − A]−1
B = C[Is − DT
]−1
B hmmmm...
11 / 28
52. Linearized Dynamics and Passivity
Linearized Dynamics
Transfer Function
Linear state space model:
Φt+1 = AΦt + Bζt
γt = CΦt A = DT
, Ci = U(xi
), BT
=
d
dζ
πDζ
ζ=0
Transfer Function:
G(s) = C[Is − A]−1
B = C[Is − DT
]−1
B hmmmm...
Resolvent Matrix:
Rs =
∞
0
e−st
etD
dt = [Is − D]−1
11 / 28
53. Linearized Dynamics and Passivity
Linearized Dynamics
Transfer Function
Linear state space model:
Φt+1 = AΦt + Bζt
γt = CΦt A = DT
, Ci = U(xi
), BT
=
d
dζ
πDζ
ζ=0
Transfer Function:
G(s) = C[Is − A]−1
B = C[Is − DT
]−1
B hmmmm...
= CRT
sB TF for L-MFM Resolvent for one load
Resolvent Matrix:
Rs =
∞
0
e−st
etD
dt = [Is − D]−1
11 / 28
55. Linearized Dynamics and Passivity
Linearized Dynamics
Passive Pools
Theorem: Reversibility =⇒ Passivity
Suppose that the nominal model is reversible.
Then its linearization satisfies,
Re G(jω) = PSDY (ω), ω ∈ R ,
where
G(s) = C[Is − A]−1
B for s ∈ C.
PSDY (ω) =
∞
−∞
e−jω
Eπ[U(X0)U(Xt)] dt
12 / 28
56. Linearized Dynamics and Passivity
Linearized Dynamics
Passive Pools
Theorem: Reversibility =⇒ Passivity
Suppose that the nominal model is reversible.
Then its linearization satisfies,
Re G(jω) = PSDY (ω), ω ∈ R ,
where
G(s) = C[Is − A]−1
B for s ∈ C.
PSDY (ω) =
∞
−∞
e−jω
Eπ[U(X0)U(Xt)] dt
Implication for control: G(s) is positive real
12 / 28
57. Linearized Dynamics and Passivity
Linearized Dynamics
Example Without Passivity
Example: Eight state model Utility function U(xi) = i.
1 2
3 4
5 6
7 8
a c
c
a
a a
a a
a a
b b b b
Not reversible
13 / 28
58. Linearized Dynamics and Passivity
Linearized Dynamics
Example Without Passivity
Example: Eight state model Utility function U(xi) = i.
Generator is the 8 × 8 matrix,
D =
−a a 0 0 0 0 0 0
a −(a + b + c) 0 b c 0 0 0
b 0 −(a + b) a 0 0 0 0
0 0 a −a 0 0 0 0
0 0 0 0 −a a 0 0
0 0 0 0 a −(a + b) 0 b
0 0 0 c b 0 −(a + b + c) a
0 0 0 0 0 0 a −a
13 / 28
59. Linearized Dynamics and Passivity
Linearized Dynamics
Example Without Passivity
1 2
3 4
5 6
7 8
a c
c
a
a a
a a
a a
b b b b
Example: Eight state model a = c = 10, b = 1
−2
−1
0
1
2
Real Axis
−1 0 1 2
ImaginaryAxis
−25 −20 −15 −10 −5 0 5 10
−15
−10
−5
0
5
10
15
Real Part
ImaginaryPart
Pole-zero Plot
G(jω), ω >0
Non-minimum
phase zero
Nyquist Plot
G(s) = C[Is − A]−1B not positive real
13 / 28
60. yt
Control @ Utility
Gain
One Million Pools
Disturbance to be rejected
Proportion of pools on
desired
ζt
µt+1 = µtPζt
yt = µt, U
One Million Pools
61. One Million Pools
A Single Pool
Control Architecture
Transition diagram for a single pool:
1 2 T−1 T
. . .
T
On
Off
12T−1
...
Numerics using discrete-time model
14 / 28
62. One Million Pools
A Single Pool
Control Architecture
1 2 T−1 T
. . .
T
On
Off
12T−1
...
Utility:
U(x) = I Pool is on
x
∝ (Power consumption)
x
14 / 28
63. One Million Pools
A Single Pool
Control Architecture
1 2 T−1 T
. . .
T
On
Off
12T−1
...
Utility:
U(x) = I Pool is on
x
∝ (Power consumption)
x
Controlled dynamics: As ζ increases, probability of turning on increases:
0 2412
0
0.5
1
zζ
=-4
ζ=-2
ζ = 4
ζ = 2
ζ = 0
(ζ)
14 / 28
64. One Million Pools
Mean Field Pool Model
Linearization: Minimum Phase Pole-Zero Plot
−1 0 1
−1
0
1
Real PartImaginaryPart
Transfer function
Normalized Frequency (×π rad/sample)1/24 hrs
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
-180
0
20
Phase(degrees)Magnitude(dB)
40
-90
0
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65. One Million Pools
Mean Field Pool Model
Stochastic simulation — Filtered regulation signal
−400
−200
0
200
400
MW
July 18 July 20July 19 July 21 July 23July 22 July 24
BPA Balancing Reserves Deployed (July 2013)
∗transmission.bpa.gov/Business/Operations/Wind/reserves.aspx
16 / 28
66. One Million Pools
Mean Field Pool Model
Stochastic simulation — Filtered regulation signal
−400
−200
0
200
400
MW
July 18 July 20July 19 July 21 July 23July 22 July 24
Filtered BPA reserve signal that can be tracked by pools
BPA Balancing Reserves Deployed (July 2013)
∗transmission.bpa.gov/Business/Operations/Wind/reserves.aspx
16 / 28
67. One Million Pools
Mean Field Pool Model
Stochastic simulation using N = 105
pools PI control
Reference (from Bonneville Power Authority)
−300
−200
−100
0
100
200
300
TrackingBPARegulationSignal
(MW)
17 / 28
68. One Million Pools
Mean Field Pool Model
Stochastic simulation using N = 105
pools PI control
Reference (from Bonneville Power Authority)
Output deviation y
−300
−200
−100
0
100
200
300
TrackingBPARegulationSignal
(MW)
17 / 28
69. One Million Pools
Mean Field Pool Model
Stochastic simulation using N = 105
pools PI control
Reference (from Bonneville Power Authority)
Output deviation y
−300
−200
−100
0
100
200
300
-2
-1
-3
2
3
0
1
Input ζ
ζ
TrackingBPARegulationSignal
(MW)
17 / 28
76. Conclusions and Extensions
Conclusions
Recap
QUIZ: Why intelligence at the loads?
To simplify control at the grid level
A particular approach to distributed control is proposed
The grid level control problem is simple because:
Mean field model is simple, and a good approximation of finite system
20 / 28
77. Conclusions and Extensions
Conclusions
Recap
QUIZ: Why intelligence at the loads?
To simplify control at the grid level
A particular approach to distributed control is proposed
The grid level control problem is simple because:
Mean field model is simple, and a good approximation of finite system
LTI approximation is positive real, which implies minimum phase
20 / 28
79. Conclusions and Extensions
Conclusions
Are the customers happy?
No time for details, but no ...
QoS without local control
−100 −80 −60 −40 −20 0 20 40 60 80 100
0
0.01
0.02
0.03
0.04
0.05
fractionofpools
Histogram of pool health
Gaussian distribution
21 / 28
80. Conclusions and Extensions
Conclusions
Are the customers happy?
No time for details, but no ...
QoS without local control
−100 −80 −60 −40 −20 0 20 40 60 80 100
0
0.01
0.02
0.03
0.04
0.05fractionofpools
Histogram of pool health
Gaussian distribution
There will be “rare events” in which the pool is under- or over-cleaned.
21 / 28
81. Conclusions and Extensions
Conclusions
Are the customers happy?
No time for details, but no ...
QoS without local control
−100 −80 −60 −40 −20 0 20 40 60 80 100
0
0.01
0.02
0.03
0.04
0.05fractionofpools
Histogram of pool health
Gaussian distribution
There will be “rare events” in which the pool is under- or over-cleaned.
Proposed approach: Additional layer of control at each load, so that hard
constraints on performance can be assured.
21 / 28
82. Conclusions and Extensions
Conclusions
Are the customers happy?
No time for details, but no ...
QoS without local control
−100 −80 −60 −40 −20 0 20 40 60 80 100
0
0.01
0.02
0.03
0.04
0.05fractionofpools
Histogram of pool health
Gaussian distribution
There will be “rare events” in which the pool is under- or over-cleaned.
Proposed approach: Additional layer of control at each load, so that hard
constraints on performance can be assured.
This will create some modeling error at grid level.
Preliminary experiments on the pool model:
No loss of performance at grid level.
21 / 28
83. Conclusions and Extensions
Conclusions
The customers are happy
Proposed approach: Additional layer of control at each load, so that hard
constraints on performance can be assured.
QoS without local control
−100 −80 −60 −40 −20 0 20 40 60 80 100
0
0.01
0.02
0.03
0.04
0.05
fractionofpools
Histogram of pool health
Gaussian distribution
22 / 28
84. Conclusions and Extensions
Conclusions
The customers are happy
Proposed approach: Additional layer of control at each load, so that hard
constraints on performance can be assured.
QoS without local control QoS with local control
−100 −80 −60 −40 −20 0 20 40 60 80 100
0
0.01
0.02
0.03
0.04
0.05
fractionofpools
Histogram of pool health
Conditional Gaussian distribution
Histogram of pool health
Gaussian distribution
−100 −80 −60 −40 −20 0 20 40 60 80 100
Load opts-out when its QoS is outside of prescribed bounds
Analysis: LQG approximation for individual load – CDC 2014
22 / 28
85. Conclusions and Extensions
Conclusions
Many issues skipped because they are topics of current research
1 Information at the load: Should these loads simply act as frequency
regulators? Measurement of local frequency deviation will suffice.
23 / 28
86. Conclusions and Extensions
Conclusions
Many issues skipped because they are topics of current research
1 Information at the load: Should these loads simply act as frequency
regulators? Measurement of local frequency deviation will suffice.
Or, more information may be valuable: Two measurements at each
load, the BA command, and local frequency measurements.
23 / 28
87. Conclusions and Extensions
Conclusions
Many issues skipped because they are topics of current research
1 Information at the load: Should these loads simply act as frequency
regulators? Measurement of local frequency deviation will suffice.
Or, more information may be valuable: Two measurements at each
load, the BA command, and local frequency measurements.
2 Information at the BA: Does this macro control view suffice?
Power Grid
Actuation
Control
WaterPump
Batteries
HVAC
Coal
GasTurbine
BP
BP
BP
BP
BP
Baseline
Generation
Disturbances
from nature
Measurements:
Voltage
Frequency
Phase
HC
Σ
−
23 / 28
88. Conclusions and Extensions
Conclusions
Many issues skipped because they are topics of current research
1 Information at the load: Should these loads simply act as frequency
regulators? Measurement of local frequency deviation will suffice.
Or, more information may be valuable: Two measurements at each
load, the BA command, and local frequency measurements.
2 Information at the BA: Does this macro control view suffice?
Power Grid
Actuation
Control
WaterPump
Batteries
HVAC
Coal
GasTurbine
BP
BP
BP
BP
BP
Baseline
Generation
Disturbances
from nature
Measurements:
Voltage
Frequency
Phase
HC
Σ
−
Does the grid operator need to know the real-time power
consumption of each population of loads?
23 / 28
90. Conclusions and Extensions
Conclusions
Many issues skipped because they are topics of current research
3 How can we engage consumers?
The formulation of contracts with customers requires a better
understanding of the value of ancillary service, as well as consumer
preferences.
24 / 28
91. Conclusions and Extensions
Conclusions
Many issues skipped because they are topics of current research
3 How can we engage consumers?
The formulation of contracts with customers requires a better
understanding of the value of ancillary service, as well as consumer
preferences.
We will not use real time
prices, even via aggregator,
if we want responsive, reliable
ancillary service
ReferenceOutputdeviation(MW)
−300
−200
−100
0
100
200
300
-2
-1
-3
2
3
0
1
Input
TrackingBPARegulationSignal
(a)
24 / 28
93. Control Techniques
FOR
Complex Networks
Sean Meyn
Pre-publication version for on-line viewing. Monograph available for purchase at your favorite retailer
More information available at http://www.cambridge.org/us/catalogue/catalogue.asp?isbn=9780521884419
Markov Chains
and
Stochastic Stability
S. P. Meyn and R. L. Tweedie
August 2008 Pre-publication version for on-line viewing. Monograph to appear Februrary 2009
π(f)<∞
∆V (x) ≤ −f(x) + bIC(x)
Pn
(x, · ) − π f → 0
sup
C
Ex[SτC(f)]<∞
References
94. References
References: Demand Response
S. Meyn, P. Barooah, A. Buˇsi´c, and J. Ehren. Ancillary service to the grid from deferrable
loads: the case for intelligent pool pumps in Florida (Invited). In Proceedings of the 52nd
IEEE Conf. on Decision and Control, 2013.
A. Buˇsi´c and S. Meyn. Passive dynamics in mean field control. ArXiv e-prints:
arXiv:1402.4618. Submitted to the 53rd IEEE Conf. on Decision and Control (Invited),
2014.
S. Meyn, Y. Chen, and A. Buˇsi´c. Individual risk in mean-field control models for
decentralized control, with application to automated demand response. Submitted to the
53rd IEEE Conf. on Decision and Control (Invited), 2014.
J. L. Mathieu. Modeling, Analysis, and Control of Demand Response Resources. PhD
thesis, Berkeley, 2012.
D. Callaway and I. Hiskens, Achieving controllability of electric loads. Proceedings of the
IEEE, 99(1):184–199, 2011.
S. Koch, J. Mathieu, and D. Callaway, Modeling and control of aggregated heterogeneous
thermostatically controlled loads for ancillary services, in Proc. PSCC, 2011, 1–7.
H. Hao, A. Kowli, Y. Lin, P. Barooah, and S. Meyn Ancillary Service for the Grid Via
Control of Commercial Building HVAC Systems. ACC 2013
(much more on our websites)
26 / 28
95. References
References: Markov Models
I. Kontoyiannis and S. P. Meyn. Spectral theory and limit theorems for geometrically
ergodic Markov processes. Ann. Appl. Probab., 13:304–362, 2003.
I. Kontoyiannis and S. P. Meyn. Large deviations asymptotics and the spectral theory of
multiplicatively regular Markov processes. Electron. J. Probab., 10(3):61–123 (electronic),
2005.
E. Todorov. Linearly-solvable Markov decision problems. In B. Sch¨olkopf, J. Platt, and
T. Hoffman, editors, Advances in Neural Information Processing Systems, (19) 1369–1376.
MIT Press, Cambridge, MA, 2007.
M. Huang, P. E. Caines, and R. P. Malhame. Large-population cost-coupled LQG problems
with nonuniform agents: Individual-mass behavior and decentralized ε-Nash equilibria.
IEEE Trans. Automat. Control, 52(9):1560–1571, 2007.
H. Yin, P. Mehta, S. Meyn, and U. Shanbhag. Synchronization of coupled oscillators is a
game. IEEE Transactions on Automatic Control, 57(4):920–935, 2012.
P. Guan, M. Raginsky, and R. Willett. Online Markov decision processes with
Kullback-Leibler control cost. In American Control Conference (ACC), 2012, 1388–1393,
2012.
V.S.Borkar and R.Sundaresan Asympotics of the invariant measure in mean field models
with jumps. Stochastic Systems, 2(2):322-380, 2012.
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96. References
References: Economics
G. Wang, M. Negrete-Pincetic, A. Kowli, E. Shafieepoorfard, S. Meyn, and U. Shanbhag.
Dynamic competitive equilibria in electricity markets. In A. Chakrabortty and M. Illic,
editors, Control and Optimization Theory for Electric Smart Grids. Springer, 2011.
G. Wang, A. Kowli, M. Negrete-Pincetic, E. Shafieepoorfard, and S. Meyn. A control
theorist’s perspective on dynamic competitive equilibria in electricity markets. In Proc.
18th World Congress of the International Federation of Automatic Control (IFAC), Milano,
Italy, 2011.
S. Meyn, M. Negrete-Pincetic, G. Wang, A. Kowli, and E. Shafieepoorfard. The value of
volatile resources in electricity markets. In Proc. of the 10th IEEE Conf. on Dec. and
Control, Atlanta, GA, 2010.
I.-K. Cho and S. P. Meyn. Efficiency and marginal cost pricing in dynamic competitive
markets with friction. Theoretical Economics, 5(2):215–239, 2010.
U.S. Energy Information Administration. Smart grid legislative and regulatory policies and
case studies. December 12 2011.
http://www.eia.gov/analysis/studies/electricity/pdf/smartggrid.pdf
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